JP3912197B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device for an internal combustion engine.
[0002]
[Prior art]
Conventionally, a particulate filter for collecting particulates in exhaust gas flowing into an exhaust passage of an internal combustion engine in which combustion is continuously performed under a lean air-fuel ratio, and a catalyst having an oxidizing ability. Exhaust gas flowing through the particulate filter by disposing a supported particulate filter, providing a bypass passage extending from the exhaust passage upstream of the particulate filter, and controlling the amount of exhaust gas flowing through the bypass passage A bypass control valve is provided to control the amount of gas, and a reducing agent supply valve is provided to supply reducing agent into the exhaust passage between the branching portion of the bypass passage and the particulate filter, thereby raising the temperature of the particulate filter. Bypass so that only a small amount of exhaust gas flows into the particulate filter. While controlling the valve, the internal combustion engine is known which is adapted to temporarily supply the reducing agent from the reducing agent feed valve. That is, when the reducing agent is supplied from the reducing agent supply valve, the reducing agent is oxidized on the particulate filter, and the temperature of the particulate filter is raised to, for example, 600 ° C. or more by the reaction heat at this time. As a result, the fine particles deposited on the particulate filter are surely oxidized and removed.
[0003]
[Problems to be solved by the invention]
However, when the reducing agent is oxidized on the particulate filter in this way, the reducing agent does not necessarily react with the entire particulate filter, and thus the temperature of the entire particulate filter can be increased uniformly. Can not. That is, if the temperature at the downstream end of the particulate filter is not excessively high, the temperature at the upstream end of the particulate filter will not rise above 600 ° C, and the temperature at the upstream end of the particulate filter will rise above 600 ° C. In this case, there is a problem that the downstream end of the particulate filter may become excessively high at this time. The problem is NO_XCatalyst or NO_XIt can also occur when the temperature of the particulate filter carrying the catalyst should be raised.
[0004]
Accordingly, an object of the present invention is to provide a particulate filter, NO_XCatalyst or NO_XAn object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can reliably raise the temperature of the entire particulate filter carrying a catalyst.
[0005]
[Means for Solving the Problems]
  In order to solve the above-mentioned problem, according to the first invention, the exhaust purification means is disposed in the exhaust passage of the internal combustion engine in which combustion is continuously performed under a lean air-fuel ratio, A particulate filter carrying a catalyst having an oxidizing ability for collecting particulates in the exhaust gas to be discharged, and NO in the exhaust gas flowing in when the air-fuel ratio of the flowing exhaust gas is lean_XNO when storing the reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in decreases_XNO is being reduced and stored_XNO decreases in quantity_XA catalyst and said NO_XIt comprises any one of a particulate filter carrying a catalyst, and a bypass passage extending from the exhaust passage upstream of the exhaust purification means is provided to control the amount of exhaust gas flowing through the bypass passage. By providing a bypass control valve for controlling the amount of exhaust gas flowing through the exhaust purification means, the exhaust gas flowing into the exhaust purification means is placed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means. An exhaust temperature raising means for raising the temperature is arranged, and the exhaust temperature raising means is provided with a reducing agent supply valve for supplying a reducing agent, and an auxiliary having an oxidizing ability arranged downstream of the reducing agent supply valve. When the temperature of the exhaust gas purification means is increased, the exhaust temperature rises while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust gas purification means. From stage of the reducing agent feed valve so as to temporarily supply the reducing agentWhen the temperature of the exhaust gas flowing into the exhaust purification unit is increased by the exhaust temperature increasing unit, the rate of increase in temperature obtained by determining the rate of increase in the temperature of the exhaust gas flowing into the exhaust purification unit The temperature increase rate is controlled so that the rate matches a predetermined target increase rate, and the auxiliary catalyst is composed of a catalyst with an electric heater, and when the temperature of the exhaust purification means is increased, The temperature rise rate is controlled by temporarily operating the heater and controlling the amount of current supplied to the electric heater.ing.
[0006]
  According to the second invention,An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the inflowing exhaust gas. Particulate filter carrying a catalyst having a function, and NO in exhaust gas flowing in when the air-fuel ratio of the flowing exhaust gas is lean _X NO when storing the reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in decreases _X NO is being reduced and stored _X NO decreases in quantity _X A catalyst and said NO _X It comprises any one of a particulate filter carrying a catalyst, and a bypass passage extending from the exhaust passage upstream of the exhaust purification means is provided to control the amount of exhaust gas flowing through the bypass passage. By providing a bypass control valve for controlling the amount of exhaust gas flowing through the exhaust purification means, the exhaust gas flowing into the exhaust purification means is placed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means. An exhaust temperature raising means for raising the temperature is arranged, and the exhaust temperature raising means is provided with a reducing agent supply valve for supplying a reducing agent, and an auxiliary having an oxidizing ability arranged downstream of the reducing agent supply valve. When the temperature of the exhaust gas purification means is increased, the exhaust temperature rises while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust gas purification means. A reductant is temporarily supplied from the reductant supply valve of the stage, and flows into the exhaust purification means when the temperature of the exhaust gas flowing into the exhaust purification means is raised by the exhaust temperature raising means The temperature increase rate is controlled so that the calculated temperature increase rate matches a predetermined target increase rate, and a unit from the reducing agent supply valve is obtained. To control the rate of temperature rise by controlling the amount of reducing agent supplied per houris doing.
[0007]
  According to the third invention,An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the inflowing exhaust gas. Particulate filter carrying a catalyst having a function, and NO in exhaust gas flowing in when the air-fuel ratio of the flowing exhaust gas is lean _X NO when storing the reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in decreases _X NO is being reduced and stored _X NO decreases in quantity _X A catalyst and said NO _X It comprises any one of a particulate filter carrying a catalyst, and a bypass passage extending from the exhaust passage upstream of the exhaust purification means is provided to control the amount of exhaust gas flowing through the bypass passage. By providing a bypass control valve for controlling the amount of exhaust gas flowing through the exhaust purification means, the exhaust gas flowing into the exhaust purification means is placed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means. An exhaust temperature raising means for raising the temperature is arranged, and the exhaust temperature raising means is provided with a reducing agent supply valve for supplying a reducing agent, and an auxiliary having an oxidizing ability arranged downstream of the reducing agent supply valve. When the temperature of the exhaust gas purification means is increased, the exhaust temperature rises while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust gas purification means. A reducing agent is temporarily supplied from a stage reducing agent supply valve, the auxiliary catalyst is constituted by a catalyst with an electric heater, and the electric heater is temporarily operated when the temperature of the exhaust gas purification means is increased. When the temperature of the exhaust purification means is raised, the bypass control valve is controlled so that the amount of exhaust gas flowing into the exhaust purification means becomes substantially zero, and the reducing agent supply action from the reducing agent supply valve The electric heater is operated while stopping the operation, and then the bypass control valve is controlled so that a slight amount of exhaust gas flows into the exhaust purification means and the electric heater is operated while the reducing agent is supplied from the reducing agent supply valve. To supplyis doing.
[0008]
  According to the fourth invention,An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the inflowing exhaust gas. Particulate filter carrying a catalyst having a function, and NO in exhaust gas flowing in when the air-fuel ratio of the flowing exhaust gas is lean _X NO when storing the reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in decreases _X NO is being reduced and stored _X NO decreases in quantity _X A catalyst and said NO _X It comprises any one of a particulate filter carrying a catalyst, and a bypass passage extending from the exhaust passage upstream of the exhaust purification means is provided to control the amount of exhaust gas flowing through the bypass passage. By providing a bypass control valve for controlling the amount of exhaust gas flowing through the exhaust purification means, the exhaust gas flowing into the exhaust purification means is placed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means. An exhaust temperature raising means for raising the temperature is arranged, and the exhaust temperature raising means is provided with a reducing agent supply valve for supplying a reducing agent, and an auxiliary having an oxidizing ability arranged downstream of the reducing agent supply valve. When the temperature of the exhaust gas purification means is increased, the exhaust temperature rises while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust gas purification means. A reducing agent is temporarily supplied from the reducing agent supply valve of the stage, and an additional exhaust purification means is disposed in the bypass passage, and in the bypass passage between the branch portion of the bypass passage and the additional exhaust purification means. An additional exhaust temperature raising means for raising the temperature of the exhaust gas flowing into the additional exhaust purification means is arranged, and the additional exhaust temperature raising means is provided with an additional reducing agent supply for supplying a reducing agent. And an additional auxiliary catalyst having an oxidizing ability disposed downstream of the reducing agent supply valve, and when the temperature of the additional exhaust purification means is raised, a slight amount is contained in the additional exhaust purification means. Temporarily supply the reducing agent from the additional reducing agent supply valve of the additional exhaust temperature raising means while controlling the bypass control valve so that the exhaust gas flows inis doing.
[0009]
  According to the fifth invention,An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the inflowing exhaust gas. Particulate filter carrying a catalyst having a function, and NO in exhaust gas flowing in when the air-fuel ratio of the flowing exhaust gas is lean _X NO when storing the reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in decreases _X NO is being reduced and stored _X NO decreases in quantity _X A catalyst and said NO _X It comprises any one of a particulate filter carrying a catalyst, and a bypass passage extending from the exhaust passage upstream of the exhaust purification means is provided to control the amount of exhaust gas flowing through the bypass passage. By providing a bypass control valve for controlling the amount of exhaust gas flowing through the exhaust purification means, the exhaust gas flowing into the exhaust purification means is placed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means. An exhaust temperature raising means for raising the temperature is arranged, and the exhaust temperature raising means is provided with a reducing agent supply valve for supplying a reducing agent, and an auxiliary having an oxidizing ability arranged downstream of the reducing agent supply valve. When the temperature of the exhaust gas purification means is increased, the exhaust temperature rises while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust gas purification means. A reductant is temporarily supplied from the reductant supply valve of the stage, and after the exhaust gas circulates in the exhaust purification means after flowing in the exhaust temperature raising means, or after flowing in the exhaust purification means It further comprises a flow direction switching means capable of selectively switching whether to flow through the exhaust temperature raising means, and when raising the temperature of the exhaust purification means, a slight amount of exhaust gas is caused by the flow direction switching means and the bypass control valve. Circulates in the exhaust gas purification means after passing through the exhaust gas temperature raising means, while temporarily supplying the reducing agent from the reducing agent supply valve of the exhaust temperature raising means, the exhaust gas purification means is set to NO. _X Catalyst or NO _X In order to temporarily change the air-fuel ratio of the exhaust gas flowing into the exhaust gas purification means to rich, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is temporarily made rich. It is possible to selectively switch between switching or temporarily supplying the reducing agent from the reducing agent supply valve, in order to temporarily switch the air-fuel ratio of the exhaust gas flowing into the exhaust purification means to rich. When the air-fuel ratio of the exhaust gas discharged from the combustion chamber is temporarily changed to rich, the flow direction switching means is controlled so that the exhaust gas flows through the exhaust purification means after flowing through the exhaust purification means, When the reducing agent is temporarily supplied from the reducing agent supply valve in order to temporarily switch the air-fuel ratio of the exhaust gas flowing into the exhaust gas purification means to rich, the flow direction is switched. And controlling means so that the exhaust gas flowing through the inside of the exhaust purification device after flowing through the inside of the exhaust temperature raising meansis doing.
[0010]
  According to the sixth invention,5In the second invention,When the amount of EGR gas supplied into the combustion chamber is increased while maintaining the injection timing constant, the amount of soot generated gradually increases and reaches a peak, and is supplied into the combustion chamber while maintaining the injection timing constant. When the amount of EGR gas is further increased, the internal combustion engine is composed of an internal combustion engine in which the fuel during combustion in the combustion chamber and the surrounding gas temperature are lower than the generation temperature of soot and soot is hardly generated. The first combustion in which the amount of EGR gas supplied to the combustion chamber is larger than the amount of EGR gas at which the generation amount of soot reaches a peak and the generation of soot hardly occurs, and the combustion is greater than the amount of EGR gas at which the generation amount of soot reaches a peak The second combustion with a small amount of EGR gas supplied into the room is selectively switched, and the air-fuel ratio of the exhaust gas flowing into the exhaust gas purification means when the first combustion is being performed. In order to temporarily switch to rich, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is temporarily switched to rich, and when the second combustion is being performed, the air-fuel ratio of the exhaust gas flowing into the exhaust purification means is Temporarily supply reducing agent from the reducing agent supply valve to temporarily switch to richis doing.
[0011]
  According to the seventh invention,1The second inventionAny one of the sixth invention fromInThe auxiliary catalyst is replaced with the NO. _X Composed of catalystis doing.
[0012]
  According to the eighth invention2The second inventionAny one of the fourth invention, the fifth invention and the sixth inventionInThe auxiliary catalyst is composed of a catalyst with an electric heater, and the electric heater is temporarily operated when the temperature of the exhaust gas purification means is increased.is doing.
[0013]
  According to the ninth invention,The first invention orIn the eighth invention,When raising the temperature of the exhaust purification means, the bypass control valve is controlled so that the amount of exhaust gas flowing into the exhaust purification means becomes almost zero, and the reducing agent supply action from the reducing agent supply valve is stopped. While operating the electric heater, the bypass control valve is controlled so that a slight amount of exhaust gas flows into the exhaust gas purification means, and the reducing agent is supplied from the reducing agent supply valve while operating the electric heater. Likeis doing.
[0014]
  According to the tenth inventionThe first invention,3rd inventionAnd any one of the eighth inventionInThe energization amount to the electric heater when supplying the reducing agent from the reducing agent supply valve is set based on the amount of reducing agent supplied from the reducing agent supply valve and the temperature of the catalyst with the electric heater.is doing.
[0015]
  According to the eleventh invention, the first inventionAny one of the third invention and the eighth inventionInThe electric heater is temporarily activated to remove soluble organic components adhering to the auxiliary catalyst.is doing.
[0019]
In the present specification, the ratio of the air supplied to the exhaust passage upstream of a certain position of the exhaust passage, the combustion chamber, and the intake passage and the hydrocarbon HC and carbon monoxide CO is determined by the ratio of the exhaust gas at that position. This is called the air-fuel ratio.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine.
[0021]
Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13. A throttle valve 17 driven by a step motor 16 is disposed in the intake duct 13, and a cooling device 18 for cooling intake air flowing through the intake duct 13 is disposed around the intake duct 13. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18 and the intake air is cooled by the engine cooling water.
[0022]
On the other hand, the exhaust port 10 is connected to an exhaust turbine 21 of an exhaust turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20, and an outlet of the exhaust turbine 21 is connected to a catalytic converter 22 via an exhaust pipe 20a.
[0023]
Referring to FIG. 2 together with FIG. 1, the catalytic converter 22 includes a switching valve 61 driven by a step motor 60, and an outlet of the exhaust pipe 20 a is connected to an inflow port 62 of the switching valve 61. An exhaust gas discharge pipe 64 of the catalytic converter 22 is connected to the outflow port 63 of the switching valve 61 facing the inflow port 62. The switching valve 61 further has a pair of inflow / outflow ports 65, 66 facing each other on both sides of a straight line connecting the inflow port 62 and the outflow port 63, and the inflow / outflow ports 65, 66 have an annular shape of the catalytic converter 22. Both ends of the exhaust pipe 67 are connected. The exhaust pipe 23 is connected to the outlet of the exhaust gas discharge pipe 64.
[0024]
The annular exhaust pipe 67 extends through the exhaust gas exhaust pipe 64, and a filter housing chamber 68 is formed in a portion of the annular exhaust pipe 67 located in the exhaust gas exhaust pipe 64. A particulate filter 69 for collecting fine particles in the exhaust gas is housed in the filter housing chamber 68. In FIG. 2, reference numerals 69a and 69b denote one end face and the other end face of the particulate filter 69, respectively.
[0025]
As shown in FIG. 2A showing a partial longitudinal sectional view of the catalytic converter 22 including the one end surface 69a of the particulate filter 69, and FIG. 2B showing a partial transverse sectional view of the catalytic converter 22, the particulate filter 69 has a honeycomb structure and includes a plurality of exhaust gas passages 70 and 71 extending in parallel with each other. These exhaust gas passages are constituted by an exhaust gas passage 70 having one end opened and the other end closed by a sealing material 72, and an exhaust gas passage 71 having the other end opened and one end closed by a sealing material 73. Is done. Note that the hatched portion in FIG. 2A shows the sealing material 73. The exhaust gas passages 70 and 71 are alternately arranged via thin partition walls 74 formed of a porous material such as cordierite. In other words, the exhaust gas passages 70 and 71 are arranged such that each exhaust gas passage 70 is surrounded by four exhaust gas passages 71 and each exhaust gas passage 71 is surrounded by four exhaust gas passages 70.
[0026]
As will be described later, NO on the particulate filter 69._XA catalyst 81 is supported. On the other hand, a catalyst storage chamber 75 is formed in the exhaust gas discharge pipe 64 between the outflow port 63 of the switching valve 61 and the portion through which the annular exhaust pipe 67 penetrates. A catalyst 76 having an oxidizing ability carried on a substrate having a honeycomb structure is accommodated.
[0027]
Also, an electrically controlled reducing agent supply valve 77 for supplying a reducing agent is disposed in the annular exhaust pipe 67 between the inflow / outflow port 65 of the switching valve 61 and the particulate filter 69. An auxiliary catalyst 79 having an oxidizing ability is disposed in the annular exhaust pipe 67 between the particulate filters 69. The reducing agent supply valve 77 and the auxiliary catalyst 79 can act as an exhaust temperature raising device 80 for raising the temperature of the exhaust gas flowing into the particulate filter 69, as will be described later.
[0028]
A reducing agent is supplied to the reducing agent supply valve 77 from an electrically controlled reducing agent pump 78. In the embodiment according to the present invention, the fuel of the internal combustion engine, that is, light oil, is used as the reducing agent. On the other hand, in the embodiment shown in FIG. 1, the auxiliary catalyst 79 is composed of a catalyst with an electric heater capable of controlling the energization amount. The energization amount to the auxiliary catalyst 79 is controlled based on an output signal from the electronic control unit 40. In the embodiment according to the present invention, the reducing agent supply valve and the auxiliary catalyst are not arranged in the annular exhaust pipe 67 between the inflow / outflow port 66 and the particulate filter 69.
[0029]
Still referring to FIG. 1, the exhaust manifold 19 and the surge tank 12 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 24, and an electrically controlled EGR control valve 25 is provided in the EGR passage 24. Be placed. A cooling device 26 for cooling the EGR gas flowing in the EGR passage 24 is disposed around the EGR passage 24. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 26, and the EGR gas is cooled by the engine cooling water.
[0030]
On the other hand, each fuel injection valve 6 is connected to a fuel reservoir, so-called common rail 27, through a fuel supply pipe 6a. Fuel is supplied into the common rail 27 from an electrically controlled fuel pump 28 with variable discharge amount, and the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 via each fuel supply pipe 6a. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27, and a fuel pump 28 is set so that the fuel pressure in the common rail 27 becomes a target fuel pressure based on an output signal of the fuel pressure sensor 29. The discharge amount is controlled.
[0031]
The electronic control unit 40 is composed of a digital computer, and is connected to each other by a bidirectional bus 41. A ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45 and an output port 46 are connected. It comprises. The output signal of the fuel pressure sensor 29 is input to the input port 45 via the corresponding AD converter 47. A temperature sensor 48 for detecting the temperature of the exhaust gas flowing into the particulate filter 69 is attached to the annular exhaust pipe 67 between the auxiliary catalyst 79 and the particulate filter 69, and the output voltage of the temperature sensor 48 corresponds to the corresponding AD. The signal is input to the input port 45 via the converter 47. The temperature of the exhaust gas represents the temperature of the auxiliary catalyst 79 or the temperature T of the particulate filter 69. A pressure sensor 49 for detecting the pressure in the exhaust pipe 20 a, that is, the engine back pressure, is attached to the exhaust pipe 20 a, and the output voltage of the pressure sensor 49 is input to the input port 45 via the corresponding AD converter 47. The A load sensor 51 that generates an output voltage proportional to the amount of depression of the accelerator pedal 50 is connected to the accelerator pedal 50, and the output voltage of the load sensor 51 is input to the input port 45 via the corresponding AD converter 47. The The amount of depression of the accelerator pedal represents the required load L. Further, a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 45.
[0032]
On the other hand, the output port 46 is connected through the corresponding drive circuit 53 to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, the fuel pump 28, the switching valve driving step motor 60, the reducing agent supply valve 77, The reducing agent pump 78 and the electric heater of the auxiliary catalyst 79 are connected to each other.
[0033]
The switching valve 61 is normally positioned at one of a position indicated by a solid line and a position indicated by a broken line in FIG. When the switching valve 61 is positioned at the position indicated by the solid line in FIG. 3B, the inflow port 62 communicates with the inflow / outflow port 65 while the communication between the outflow port 63 and the inflow / outflow port 66 is blocked by the switching valve 61. The outflow port 63 is communicated with the inflow / outflow port 66 by the switching valve 61. As a result, as shown by the solid arrows in FIG. 3B, all the exhaust gas flowing through the exhaust pipe 20a flows into the annular exhaust pipe 67 through the inflow port 62 and the inflow / outflow port 65 in sequence, Next, after passing through the exhaust temperature raising device 80 and then passing through the particulate filter 69, the exhaust gas flows out into the exhaust gas exhaust pipe 64 through the inflow / outflow port 66 and the outflow port 63 in order.
[0034]
On the other hand, when the switching valve 61 is positioned at the position indicated by the broken line in FIG. 3B, the inflow port 62 is inflow / outflow while the communication between the outflow port 63 and the inflow / outflow port 65 is blocked by the switching valve 61. The outflow port 63 is communicated with the inflow / outflow port 65 by the switching valve 61. As a result, all the exhaust gas flowing through the exhaust pipe 20a flows into the annular exhaust pipe 67 through the inflow port 62 and the inflow / outflow port 66 in sequence as shown by the broken arrows in FIG. Next, after passing through the particulate filter 69 and then passing through the exhaust temperature raising device 80, the exhaust gas flows out into the exhaust gas discharge pipe 64 through the inflow / outflow port 65 and the outflow port 63 in order.
[0035]
By switching the position of the switching valve 61 in this way, the flow of exhaust gas in the annular exhaust pipe 67 is reversed. In other words, whether exhaust gas flows through the particulate filter 69 after flowing through the exhaust temperature raising device 80 or selectively flows through the exhaust temperature raising device 80 after flowing through the particulate filter 69. Switchable. Hereinafter, the exhaust gas flow indicated by the solid line in FIG. 3B is referred to as forward flow, and the exhaust gas flow indicated by the broken line is referred to as reverse flow. 3B, the position of the switching valve 61 indicated by a solid line is referred to as a forward flow position, and the position of the switching valve 61 indicated by a broken line is referred to as a backflow position.
[0036]
The exhaust gas that has flowed into the exhaust gas discharge pipe 64 through the outflow port 66 then passes through the catalyst 76 and travels along the outer peripheral surface of the annular exhaust pipe 67 as shown in FIGS. After that, it flows out into the exhaust pipe 23.
[0037]
Explaining the flow of exhaust gas in the particulate filter 69, during forward flow, the exhaust gas flows into the particulate filter 69 through the one end surface 69a and flows out of the particulate filter 69 through the other end surface 69b. At this time, the exhaust gas flows into the exhaust gas passage 70 opened in the one end surface 69 a, and then flows into the adjacent exhaust gas passage 71 through the surrounding partition wall 74. On the other hand, during reverse flow, the exhaust gas flows into the particulate filter 69 via the other end surface 69b and flows out of the particulate filter 69 via the one end surface 69a. At this time, the exhaust gas flows into the exhaust gas passage 71 opened in the other end surface 69 b, and then flows into the adjacent exhaust gas passage 70 through the surrounding partition wall 74.
[0038]
In the embodiment shown in FIG. 1, the switching valve 61 can be controlled to the weak forward flow position shown in FIG. 4 and the bypass position shown in FIG. 5 in addition to the forward flow position and the reverse flow position shown in FIG. it can. That is, when the switching valve 61 is held at the weak forward flow position, most of the exhaust gas flowing through the exhaust pipe 20a is directly exhausted from the inflow port 62 through the outflow port 63 as shown by the arrows in FIG. The gas flows out into the gas exhaust pipe 64, that is, bypasses the particulate filter 69, and a small amount of the remaining exhaust gas flows into the annular exhaust pipe 67 through the inflow / outflow port 65, and then passes through the exhaust temperature raising device 80. Then, it circulates in the particulate filter 69 in the forward flow direction. That is, when the switching valve 61 is held at the weak forward flow position, the amount of exhaust gas flowing through the exhaust temperature raising device 80 and the particulate filter 69 is larger than when the switching valve 61 is held at the forward flow position or the reverse flow position. As a result, the space velocity of the exhaust gas in the exhaust temperature raising device 80 and the particulate filter 69 decreases.
[0039]
On the other hand, when the switching valve 61 is held at the bypass position, all the exhaust gas flowing through the exhaust pipe 20a is directly discharged from the inflow port 62 through the outflow port 63 as indicated by arrows in FIG. It flows into the pipe 64, that is, bypasses the exhaust temperature raising device 80 and the particulate filter 69, and the exhaust gas does not flow through the exhaust temperature raising device 80 and the particulate filter 69. Thus, when the switching valve 61 is held at the weak forward flow position or the bypass position, the exhaust gas flow path from the inflow port 62 to the outflow port 63 of the switching valve 61 acts as a bypass passage that bypasses the particulate filter 69. It will be.
[0040]
As shown in FIG. 6, NO on the partition wall 74 of the particulate filter 69, for example, on both side surfaces of the partition wall 74 and the inner wall surface of the pore._XEach catalyst 81 is supported. This NO_XThe catalyst 81 uses, for example, alumina as a carrier, and an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, an alkaline earth such as barium Ba and calcium Ca, lanthanum La, and yttrium Y on the carrier. At least one selected from rare earths and a noble metal such as platinum Pt, palladium Pd, rhodium Rh, and iridium Ir are supported.
[0041]
NO_XThe catalyst is NO when the air-fuel ratio of the exhaust gas flowing in is lean._XNO when storing the reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in decreases_XNO is being reduced and stored_XAccumulation and reduction action to reduce the amount of.
[0042]
NO_XThe detailed mechanism of the accumulation and reduction action of the catalyst has not been fully clarified. However, the mechanism currently considered can be briefly described as follows, taking as an example the case where platinum Pt and barium Ba are supported on a support.
[0043]
That is, NO_XWhen the air-fuel ratio of the exhaust gas flowing into the catalyst becomes considerably leaner than the stoichiometric air-fuel ratio (≈14.6), the oxygen concentration in the exhaust gas flowing in greatly increases and oxygen O₂Is O₂ ⁻Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the inflowing exhaust gas is O on the surface of platinum Pt.₂ ⁻Or O^2-Reacts with NO₂(NO + O₂→ NO₂+ O^*Where O^*Is active oxygen). Then the generated NO₂Part of the NO is being oxidized further on platinum Pt_XNitrate ion NO while being absorbed in the catalyst and combined with barium oxide BaO₃ ⁻NO in the form of_XIt diffuses into the catalyst. In this way NO_XIs NO_XStored in the catalyst.
[0044]
In contrast, NO_XWhen the average air-fuel ratio of the exhaust gas flowing into the catalyst becomes rich or stoichiometric, the oxygen concentration in the exhaust gas decreases and NO₂Production amount decreases and the reaction proceeds in the reverse direction (NO₃ ⁻→ NO + 2O^*) And thus NO_XNitrate ion NO in the catalyst₃ ⁻NO in the form of NO_XReleased from the catalyst. This released NO_XIf the exhaust gas contains a reducing agent, that is, HC or CO, it can be reduced by reacting with the HC and CO. In this way, NO on the surface of platinum Pt._XNO when no longer exists_XNO from catalyst to next_XIs released and reduced, NO_XNO stored in the catalyst_XThe amount of is gradually reduced.
[0045]
NO without forming nitrate_XStore NO_XNO without releasing_XIt is also possible to reduce In addition, active oxygen O^*If you pay attention to, NO_XThe catalyst is NO_XWith the accumulation and release of oxygen^*It can also be regarded as an active oxygen generating catalyst that generates
[0046]
On the other hand, the catalyst 76 and the auxiliary catalyst 79 are each formed of a noble metal catalyst containing noble metal such as platinum Pt without containing alkali metal, alkaline earth, and rare earth. However, the catalyst 76 or the auxiliary catalyst 79 is replaced with the NO described above._XIt can also be formed from a catalyst.
[0047]
As described above, the switching valve 61 is normally held in the forward flow position or the reverse flow position. The switching valve 61 is switched from the forward flow position to the reverse flow position or vice versa every time the required load L becomes smaller than a predetermined threshold value, for example. When the switching valve 61 is switched from the forward flow position to the reverse flow position or vice versa, the switching valve 61 passes through the bypass position shown in FIG._XThe catalyst 81 is bypassed. Therefore, if the switching valve 61 is switched from the forward flow position to the reverse flow position or vice versa when the required load L is low, the particulate filter 69 and the NO._XThe amount of exhaust gas that bypasses the catalyst 81 can be reduced.
[0048]
As described above, the exhaust gas passes through the particulate filter 69 even when the switching valve 61 is in the forward flow position or the reverse flow position. Further, the internal combustion engine shown in FIG. 1 is continuously combusted under a lean air-fuel ratio, and therefore, the air-fuel ratio of the exhaust gas flowing into the particulate filter 69 is maintained lean. As a result, NO in the exhaust gas_XIs NO on the particulate filter 69_XIt is stored in the catalyst 81.
[0049]
NO over time_XNO accumulated in catalyst 81_XThe amount increases gradually. In an embodiment according to the invention, for example NO_XNO accumulated in catalyst 81_XWhen the amount exceeds the allowable amount QN1, NO_XNO stored in catalyst 81_XNO_XNO accumulated in catalyst 81_XNO to reduce the amount_XRich control is performed in which the air-fuel ratio of the exhaust gas flowing into the catalyst 81 is temporarily changed to rich. This rich control will be described later.
[0050]
On the other hand, fine particles mainly composed of carbon contained in the exhaust gas are collected on the particulate filter 69. That is, in brief description, fine particles are collected on the side surfaces and the pores of the partition wall 74 on the exhaust gas passage 70 side in the forward flow, and on the side surfaces and the pores of the partition wall 74 on the exhaust gas passage 71 side in the reverse flow. Fine particles are collected. As described above, the internal combustion engine shown in FIG. 1 is continuously combusted under a lean air-fuel ratio, and NO_XSince the catalyst 81 has an oxidizing ability, if the temperature of the particulate filter 69 is maintained at a temperature at which particulates can be oxidized, for example, 250 ° C. or more, the particulates are oxidized on the particulate filter 69 and removed. The
[0051]
In this case, the above-mentioned NO_XNO of catalyst 81_XAccording to the accumulation and reduction mechanism of NO_XNO in catalyst 81_XNO is also stored when_XActive oxygen is also generated when is released. This active oxygen is oxygen O₂Therefore, the fine particles deposited on the particulate filter 69 are rapidly oxidized. That is, NO on the particulate filter 69._XWhen the catalyst 81 is supported, fine particles deposited on the particulate filter 69 are oxidized regardless of whether the air-fuel ratio of the exhaust gas flowing into the particulate filter 69 is lean or rich. In this way, the fine particles are continuously oxidized.
[0052]
However, if the temperature of the particulate filter 69 is not maintained at a temperature that can oxidize the particulates, or the amount of particulates flowing into the particulate filter 69 per unit time becomes considerably large, the particulates that accumulate on the particulate filter 69. Gradually increases, and the pressure loss of the particulate filter 69 increases.
[0053]
Therefore, in the embodiment according to the present invention, for example, when the amount of deposited particulates on the particulate filter 69 exceeds the allowable maximum amount, the exhaust gas flowing into the particulate filter 69 in order to reduce the amount of particulates deposited on the particulate filter 69. While maintaining the gas air-fuel ratio to be lean, the temperature of the particulate filter 69 is raised to 600 ° C. or higher, and then temperature rise control is performed to maintain it at 600 ° C. or higher. When this temperature increase control is performed, the fine particles deposited on the particulate filter 69 are ignited and burned and removed. In the internal combustion engine shown in FIG. 1, when the engine back pressure detected by the pressure sensor 49 exceeds the allowable value when the switching valve 61 is held in the forward flow position or the reverse flow position, the particulate filter 69 It is determined that the amount of deposited fine particles exceeded the allowable maximum amount.
[0054]
On the other hand, sulfur is contained in the exhaust gas._XIs included in the form of NO_XNO in the catalyst 81_XNot only SO_XCan also be stored. This SO_XNO_XThe accumulation mechanism in the catalyst 81 is NO._XThis is considered to be the same as the accumulation mechanism. That is, when the case where platinum Pt and barium Ba are supported on a carrier is simply described as an example, NO_XWhen the air-fuel ratio of the exhaust gas flowing into the catalyst 81 is lean, as described above, the oxygen O₂Is O₂ ⁻Or O^2-Attached to the surface of platinum Pt in the form of SO₂Is O on the surface of platinum Pt.₂ ⁻Or O^2-Reacts with SO₃It becomes. The generated SO₃NO is being oxidized on platinum Pt_XWhile being absorbed into the catalyst 81 and combined with barium oxide BaO, sulfate ions SO₄ ⁻NO in the form of_XIt diffuses into the catalyst 81. This sulfate ion SO₄ ⁻Then barium ion Ba⁺Combined with sulfate BaSO₄Is generated. This sulfate BaSO₄Is difficult to decompose, NO_XEven if the air-fuel ratio of the exhaust gas flowing into the catalyst 81 is simply rich, NO_XSulfate BaSO in catalyst 81₄The amount of does not decrease. For this reason, as time passes, NO_XSulfate BaSO in catalyst 81₄The amount of NO increases, resulting in NO_XNO that the catalyst 81 can store_XThe amount of will decrease.
[0055]
However, NO_XWhile maintaining the temperature of the catalyst 81 at 550 ° C. or higher, NO_XWhen the average air-fuel ratio of the exhaust gas flowing into the catalyst 81 is made rich or stoichiometric, NO._XSulfate BaSO in catalyst 81₄Decomposes into SO₃NO in the form of_XReleased from the catalyst 81. This released SO₃If exhaust gas contains a reducing agent, ie, HC or CO, it reacts with HC and CO to react with SO.₂To be reduced. In this way NO_XSO stored in the catalyst 81_XThe amount of NO decreases gradually, at this time NO_XFrom catalyst 81 to SO_XIs SO₃It will not leak out.
[0056]
Therefore, in the embodiment according to the present invention, for example, NO._XAccumulated SO in catalyst 81_XWhen the amount exceeds the allowable amount, NO_XSO stored in the catalyst 81_XNO_XAccumulated SO in catalyst 81_XNO to reduce the amount_XNO while maintaining the air-fuel ratio of the exhaust gas flowing into the catalyst 81 lean_XThe temperature of the catalyst 81 is increased to 550 ° C. or higher, and then NO_XTemperature increase control is performed to maintain the average air-fuel ratio of the exhaust gas flowing into the catalyst 81 at 550 ° C. or higher while maintaining the theoretical air-fuel ratio or rich.
[0057]
FIG. 7 is a time chart schematically showing these temperature rise controls. In FIG. 7, D represents the opening degree of the switching valve 61. D = 0 indicates that the switching valve 61 is in the bypass position, D = 100 indicates that the switching valve 61 is in the forward flow position, and D = -100 indicates that the switching valve 61 is in the reverse position. Represents. That is, when D> 0, the amount of exhaust gas flowing in the forward flow direction in the particulate filter 69 increases as D increases. When D <0, the amount of exhaust gas in the particulate filter 69 increases in the reverse flow direction as D decreases. The amount of exhaust gas that circulates increases.
[0058]
In FIG. 7, an arrow X indicates a time when the above-described temperature increase control should be started. At this time, the switching valve 61 is switched from, for example, a reverse flow position to a weak forward flow position and held, and the electric heater of the auxiliary catalyst 79 is turned on. Further, the reducing agent is supplied from the reducing agent supply valve 77 while maintaining the air-fuel ratio of the exhaust gas flowing into the auxiliary catalyst 79 and the particulate filter 69 lean. This reducing agent is oxidized in the particulate filter 69, so that the temperature T of the particulate filter 69 is raised as shown in FIG.
[0059]
In this case, the reducing agent is vaporized or partially oxidized in the auxiliary catalyst 79 before reaching the particulate filter 69. At this time, the electric heater of the auxiliary catalyst 79 is turned on. As a result, the temperature of the exhaust gas flowing into the particulate filter 69 is raised.
[0060]
When oxidizing the reducing agent in the particulate filter 69 to increase the temperature of the particulate filter 69, the reducing agent is not immediately oxidized even if it flows into the particulate filter 69. Oxidized after proceeding to some extent. As a result, the temperature of the downstream side portion of the exhaust gas flow of the particulate filter 69 becomes higher than the temperature of the upstream side portion.
[0061]
On the other hand, in the embodiment shown in FIG. 7, the temperature of the exhaust gas flowing into the particulate filter 69 is raised, and thereby the temperature of the upstream portion of the particulate filter 69 in the exhaust gas flow is raised. . Therefore, the temperature of the entire particulate filter 69 can be increased substantially uniformly.
[0062]
At this time, since the switching valve 61 is held at the weak forward flow position, the residence time of the exhaust gas in the particulate filter 69 becomes longer. Therefore, the temperature of the particulate filter 69 can be quickly raised.
[0063]
In this way, the filter temperature T rises, and at this time, the filter temperature T rises with a temperature rise rate ΔT. In the embodiment shown in FIG. 7, temperature increase rate maintenance control for controlling this temperature increase rate ΔT so as to coincide with a predetermined target increase rate is performed.
[0064]
Here, the temperature increase rate maintaining control will be described with reference to FIG. In FIG. 8, the solid line indicates the relationship between the opening degree D of the switching valve 61 when the temperature increase control is being performed and the rate of increase ΔT in the filter temperature, and the broken line indicates the opening degree D of the switching valve 61 and the patty. A relationship with the amount QEX of the exhaust gas flowing in the forward flow direction in the curate filter 69 is shown.
[0065]
When the opening degree D of the switching valve 61 is zero, that is, when the switching valve 61 is in the bypass position, there is no exhaust gas flow in the particulate filter 69, so that almost no oxidation reaction of the reducing agent occurs in the particulate filter 69. Absent.
[0066]
When the opening degree D of the switching valve 61 is slightly increased from zero, the temperature increase rate ΔT rapidly increases and reaches a peak. When the opening degree D is further increased, the temperature increase rate ΔT gradually increases as the opening degree D increases. descend. This is mainly because the amount of reducing agent oxidized in the particulate filter 69 decreases because the space velocity of the exhaust gas in the particulate filter 69 increases as the opening degree D increases. That is, if the opening degree D of the switching valve 61 is controlled, the temperature increase rate ΔT can be controlled.
[0067]
Therefore, in the temperature increase rate maintaining control of the embodiment shown in FIG. 7, the opening degree D of the switching valve 61 is controlled so that the temperature increase rate ΔT of the filter temperature T matches the target increase rate ΔT0. That is, when the temperature raising control should be started, the opening degree D of the switching valve 61 is set as an initial value, for example, to D1 shown in FIG. 8, and then the temperature increase rate ΔT of the filter temperature T detected by the temperature sensor 48 is the target. When the rate of increase is smaller than the increase rate ΔT0, the opening degree D is decreased by a certain value. In this way, the filter temperature T can be quickly raised, but the filter temperature T is prevented from rising excessively.
[0068]
The target increase rate ΔT0 may be determined in any way, but in the embodiment shown in FIG. 7, the target increase rate ΔT0 is determined according to the engine operating state. That is, as shown in FIG. 9A, the target increase rate ΔT0 is reduced as the required load L and the engine speed N increase. This is because the temperature of the exhaust gas discharged from the internal combustion engine increases as the required load L and the engine speed N increase. The target increase rate ΔT0 is stored in advance in the ROM 42 as a function of the required load L and the engine speed N in the form of a map shown in FIG.
[0069]
Next, when the filter temperature T exceeds, for example, the lower limit value TL of the target holding temperature, temperature maintenance control for maintaining the filter temperature T at the target holding temperature is performed. The lower limit value TL of the target holding temperature is, for example, 600 ° C. in the temperature rise control for reducing the amount of deposited fine particles on the particulate filter 69, and NO._XSO stored in the catalyst 81_XNO_XAccumulated SO in catalyst 81_XIn the temperature rise control for reducing the amount, for example, 550 ° C. Further, the upper limit value TU of the target holding temperature is, for example, NO in any case._XThe temperature is 700 ° C. at which thermal degradation of the catalyst 81 does not occur. In other words, in the temperature maintenance control, the filter temperature T is maintained between the lower limit value TL and the upper limit value TU.
[0070]
In the temperature maintenance control for reducing the amount of particulates deposited on the particulate filter 69, the air-fuel ratio of the exhaust gas flowing into the particulate filter 69 is maintained lean, and NO._XSO stored in the catalyst 81_XNO_XAccumulated SO in catalyst 81_XIn the temperature maintenance control for decreasing the amount, the average air-fuel ratio of the exhaust gas flowing into the particulate filter 69 is maintained at the stoichiometric air-fuel ratio or rich.
[0071]
Next, when the temperature raising control should be stopped as indicated by an arrow Y in FIG. 7, the switching valve 61 is switched to the forward flow position, for example, the electric heater of the auxiliary catalyst 79 is turned off, and the reduction from the reducing agent supply valve 77 is performed. The agent supply is stopped. In the embodiment according to the present invention, for example, the amount of deposited fine particles on the particulate filter 69 or NO_XAccumulated SO in catalyst 81_XWhen the amount becomes substantially zero, it is determined that the temperature raising control should be stopped.
[0072]
FIG. 10 shows a routine for executing the temperature raising control shown in FIG. This routine is executed by interruption every predetermined time.
[0073]
Referring to FIG. 10, first, at step 100, it is determined whether or not the temperature raising control should be started. When the temperature raising control should not be started, the processing cycle is ended, and when the temperature raising control should be started, the process proceeds to step 101. In step 101, the switching valve 61 is switched to the weak forward flow position, and at this time, the opening degree D is set to D1 described above. In the subsequent step 102, the electric heater of the auxiliary catalyst 79 is turned on, and at this time, the energization amount QE to the electric heater is set to a constant value QE1. In the subsequent step 103, the reducing agent supply operation from the reducing agent supply valve 77 is started, and at this time, the time interval INT of the reducing agent supply operation is set to a constant value INT1. In the embodiment according to the present invention, as shown in FIG. 11, the reducing agent is intermittently supplied from the reducing agent supply valve 77 at the time interval INT, and this INT is set to INT1.
[0074]
In the subsequent step 104, the target increase rate ΔT0 is calculated from the map of FIG. In the following step 105, a temperature increase rate maintenance control routine is performed. This temperature rise rate maintenance control routine is shown in FIG.
[0075]
Referring to FIG. 12A, first, at step 120, the rate of increase ΔT of the filter temperature T is calculated based on the output of the temperature sensor 48. In the following step 121, it is determined whether or not the actual temperature increase rate ΔT is larger than the target increase rate ΔT0. When ΔT> ΔT0, the routine proceeds to step 122, where the opening degree D of the switching valve 61 is increased by a certain value d1, and when ΔT ≦ ΔT0, the routine proceeds to step 123, where the opening degree D of the switching valve 61 is decreased by a certain value d1. Is done. The processing cycle is then terminated.
[0076]
In the following step 106, it is determined whether or not the temperature increase rate maintenance control should be stopped and the temperature maintenance control should be started. When the temperature maintenance control should not be started, the routine returns to step 105, and when the temperature maintenance control should be started, the routine proceeds to step 107, where the temperature maintenance control routine is executed. This temperature maintenance control routine is shown in FIG.
[0077]
Referring to FIG. 12B, first, at step 140, it is judged if the filter temperature T is higher than the upper limit value TU of the target temperature. When T ≦ TU, the routine jumps to step 142. When T> TU, the routine proceeds to step 141 where the opening degree D of the switching valve 61 is increased by a constant value d2. Next, the routine proceeds to step 142. In step 142, it is determined whether or not the filter temperature T is lower than the lower limit value TL of the target temperature. When T ≧ TL, the processing cycle is terminated, and when T <TL, the routine proceeds to step 143 where the opening degree D of the switching valve 61 is decreased by a constant value d2. The processing cycle is then terminated.
[0078]
In the following step 108, it is determined whether or not the temperature maintenance control should be stopped and the temperature raising control should be stopped. When temperature increase control should not be stopped, the process returns to step 107, and when temperature increase control should be stopped, the process proceeds to step 109. In step 109, the switching valve 61 is switched to the forward flow position, for example, the electric heater of the auxiliary catalyst 79 is turned off, and the reducing agent supply action from the reducing agent supply valve 77 is stopped. In this way, the temperature raising control is stopped.
[0079]
13 and 14 show another embodiment of the temperature rise rate maintenance control routine and the temperature maintenance control, respectively.
[0080]
In the embodiment shown in FIG. 13, the rate of increase ΔT of the filter temperature is controlled by controlling the energization amount QE of the auxiliary catalyst 79 to the electric heater. That is, referring to FIG. 13A showing the temperature increase rate maintenance control routine, first, in step 120a, the increase rate ΔT of the filter temperature T is calculated based on the output of the temperature sensor 48. In the following step 121a, it is determined whether or not the actual temperature increase rate ΔT is larger than the target increase rate ΔT0. When ΔT> ΔT0, the routine proceeds to step 122a, where the energization amount QE is decreased by the constant value q1, and when ΔT ≦ ΔT0, the routine proceeds to step 123a, where the energization amount QE is increased by the constant value q1. The processing cycle is then terminated.
[0081]
Referring to FIG. 13B showing the temperature maintenance control routine, first, at step 140a, it is judged if the filter temperature T is higher than the upper limit value TU of the target temperature. When T ≦ TU, the routine jumps to step 142a. When T> TU, the routine proceeds to step 141a, where the energization amount QE is decreased by a constant value q2. Next, the routine proceeds to step 142a. In step 142a, it is determined whether or not the filter temperature T is lower than the lower limit value TL of the target temperature. When T ≧ TL, the processing cycle is terminated. When T <TL, the process proceeds to step 143a, where the energization amount QE is increased by a constant value q2. The processing cycle is then terminated.
[0082]
On the other hand, in the embodiment shown in FIG. 14, the increase rate ΔT of the filter temperature is controlled by controlling the amount of reducing agent supplied per unit time from the reducing agent supply valve 77, for example, the time interval INT (FIG. 11). The That is, referring to FIG. 14A showing the temperature increase rate maintenance control routine, first, in step 120b, the increase rate ΔT of the filter temperature T is calculated based on the output of the temperature sensor 48. In the following step 121b, it is determined whether or not the actual temperature increase rate ΔT is larger than the target increase rate ΔT0. When ΔT> ΔT0, the routine proceeds to step 122b, where the time interval INT is increased by a constant value i1, and when ΔT ≦ ΔT0, the routine proceeds to step 123b, where the time interval INT is decreased by a constant value i1. The processing cycle is then terminated.
[0083]
Referring to FIG. 14B showing the temperature maintenance control routine, first, at step 140b, it is judged if the filter temperature T is higher than the upper limit value TU of the target temperature. When T ≦ TU, the routine jumps to step 142b. When T> TU, the routine proceeds to step 141b, where the time interval INT is increased by a constant value i2. Next, the routine proceeds to step 142b. In step 142b, it is determined whether or not the filter temperature T is lower than the lower limit value TL of the target temperature. When T ≧ TL, the processing cycle is terminated. When T <TL, the process proceeds to step 143b, where the time interval INT is decreased by a constant value i2. The processing cycle is then terminated.
[0084]
FIG. 15 shows another embodiment of the temperature rise control. In this embodiment, when the temperature increase control is to be started as indicated by an arrow X in FIG. 15, when the filter temperature T is lower than the threshold value TW, the temperature increase described with reference to FIGS. Preheating control is performed prior to rate maintenance control and temperature maintenance control. That is, in this preheating control, the switching valve 61 is switched from, for example, the backflow position to the bypass position, and the electric heater of the auxiliary catalyst 79 is turned on, however, no reducing agent is supplied from the reducing agent supply valve 77. In this way, since the exhaust gas does not flow through the auxiliary catalyst 79, the temperature of the auxiliary catalyst 79 can be quickly increased. Further, since the reducing agent is not supplied, the catalyst particles of the auxiliary catalyst 79 are not covered with the reducing agent, and the oxidizing ability of the auxiliary catalyst 79 is not lowered.
[0085]
Next, for example, when the time tZ has elapsed since the start of the preheating control, the preheating control is stopped and the temperature increase rate maintenance control is started. At this time, the temperature of the auxiliary catalyst 79 is high. Therefore, the reducing agent supplied at this time is well vaporized or partially oxidized in the auxiliary catalyst 79, and the filter temperature T is quickly raised.
[0086]
Further, in the embodiment shown in FIG. 15, the temperature increase rate maintenance control and the temperature maintenance control are performed by controlling the energization amount QE to the electric heater of the auxiliary catalyst 79. That is, regarding temperature increase rate maintenance control, the temperature increase rate ΔT is maintained at the target rate of increase ΔT0 as the amount QF of reducing agent supplied per unit time increases or as the temperature of the auxiliary catalyst 79 decreases. The amount of electricity required to do so increases. Similarly, in the temperature maintenance control, the energization necessary for maintaining the filter temperature T at the target temperature as the amount QF of the reducing agent supplied per unit time increases or as the temperature of the auxiliary catalyst 79 decreases. The amount increases.
[0087]
Therefore, in the embodiment shown in FIG. 15, the energization amount QEI required to maintain the temperature increase rate ΔT at the target increase rate ΔT0 and the energization amount QEM required to maintain the filter temperature T at the target temperature are respectively It is obtained in advance as a function of the reducing agent supply amount QF and the temperature T of the auxiliary catalyst 79. When the temperature increase rate maintenance control is performed, the electric heater of the auxiliary catalyst 79 is energized by QEI, and when the temperature maintenance control is performed, the auxiliary catalyst 79 electric heaters are energized by QEM. These QEI and QEM are stored in advance in the ROM 42 in the form of maps shown in FIGS. 16B and 16C as functions of the reducing agent supply amount QF and the temperature T of the auxiliary catalyst 79, respectively.
[0088]
FIG. 17 shows a routine for executing the temperature raising control shown in FIG. This routine is executed by interruption every predetermined time.
[0089]
Referring to FIG. 17, first, at step 100a, it is determined whether or not the temperature raising control should be started. When the temperature raising control should not be started, the processing cycle is ended, and when the temperature raising control should be started, the process proceeds to step 101a. In step 101a, a preheating control routine is executed. This preheating control routine is shown in FIG.
[0090]
Referring to FIG. 18, first, at step 160, it is judged if the filter temperature T is lower than the threshold value TW. When T ≧ TW, the processing cycle is terminated. When T <TW, the routine proceeds to step 161 where the switching valve 61 is switched to the bypass position, that is, the opening degree D is set to zero. In the following step 162, the electric heater of the auxiliary catalyst 79 is turned on, and at this time, the energization amount QE to the electric heater is set to a constant value QE1. Preheating control is performed in this way. In the following step 163, it is determined whether or not the time tZ has elapsed since the preheating control was started. When the time tZ has not elapsed, the process returns to step 163, and when the time tZ has elapsed, the processing cycle is ended, that is, the preheating control is stopped.
[0091]
In the subsequent step 102a, the switching valve 61 is switched to the weak forward flow position, and at this time, the opening degree D is set to D1 described above. In the subsequent step 103a, the reducing agent supply operation is started from the reducing agent supply valve 77, and at this time, the time interval INT of the reducing agent supply operation is set to a constant value INT1. In the subsequent step 104a, the target increase rate ΔT0 is calculated from the map of FIG. 9B, and in the subsequent step 105a, a temperature increase rate maintaining control routine is performed. This temperature rise rate maintenance control routine is shown in FIG.
[0092]
Referring to FIG. 19A, in step 120c, a reducing agent supply amount QF is calculated. In the subsequent step 121c, the required energization amount QEI is calculated from the map of FIG. In the subsequent step 122c, the energization amount QE is set to this QEI.
[0093]
In the subsequent step 106a, it is determined whether or not the temperature maintenance control should be started. When the temperature maintenance control should not be started, the routine returns to step 105a, and when the temperature maintenance control should be started, the routine proceeds to step 107a, where the temperature maintenance control routine is executed. This temperature maintenance control routine is shown in FIG.
[0094]
Referring to FIG. 19B, in step 140c, the reducing agent supply amount QF is calculated. In the subsequent step 141c, the required energization amount QEM is calculated from the map of FIG. In the subsequent step 142c, the energization amount QE is set to this QEM.
[0095]
In the next step 108a, it is determined whether or not the temperature raising control should be stopped. When temperature increase control should not be stopped, the process returns to step 107a, and when temperature increase control should be stopped, the process proceeds to step 109a. In step 109a, the switching valve 61 is switched to the forward flow position, for example, the electric heater of the auxiliary catalyst 79 is turned off, and the reducing agent supply action from the reducing agent supply valve 77 is stopped. In this way, the temperature raising control is stopped.
[0096]
By the way, when such a temperature rise control is performed, a reducing agent adheres to the auxiliary catalyst 79 in a liquid form, and a soluble organic component (SOF) is formed on the auxiliary catalyst 79 even if the electric heater is turned on. ) May remain. This SOF covers the catalyst particles of the auxiliary catalyst 79, and there is a possibility that the oxidizing ability of the auxiliary catalyst 79 is lowered.
[0097]
However, the SOF is thermally decomposed and removed from the auxiliary catalyst 79 when the temperature of the auxiliary catalyst 79 increases. Therefore, in the embodiment shown in FIG. 1, regeneration control for temporarily operating the electric heater is performed in order to remove the SOF adhering to the auxiliary catalyst 79.
[0098]
Although this regeneration control may be performed at any timing, in the embodiment according to the present invention, the regeneration control is performed not during the above-described temperature increase control and during fuel supply stop during engine deceleration operation. This will be described with reference to FIG.
[0099]
In the internal combustion engine shown in FIG. 1, when the required load L becomes zero as shown in FIG. 20 and the engine speed N is higher than the first threshold value N1, the fuel supply to the engine is stopped. The When the fuel supply is stopped, the engine speed N gradually decreases, and then the fuel supply resumes when the engine speed N becomes lower than the second threshold value N2 or the required load L becomes higher than zero. Is done.
[0100]
When such a fuel supply stop action is started, as shown in FIG. 20, the switching valve 61 is switched from, for example, the forward flow position to the bypass position and held, and the electric heater of the auxiliary catalyst 79 is turned on. In this way, a relatively low temperature gas does not flow through the auxiliary catalyst 79, so that the SOF on the auxiliary catalyst 79 can be quickly removed.
[0101]
Next, when the regeneration control is started, for example, when the time tV elapses or the fuel supply operation is resumed, the electric heater is turned off, the switching valve 61 is returned to the forward flow position, for example, and thus the regeneration control is stopped. The
[0102]
FIG. 21 shows a routine for executing the regeneration control shown in FIG. This routine is executed by interruption every predetermined time.
[0103]
Referring to FIG. 21, first, at step 180, it is judged if the temperature raising control is currently being performed. When the temperature raising control is currently being performed, the processing cycle is terminated. In step 181, it is determined whether the fuel supply is currently stopped. When the fuel supply is not currently stopped, the routine jumps to step 185. When the fuel supply is currently stopped, the routine proceeds to step 182 where the switching valve 61 is switched to the bypass position. In the subsequent step 183, the electric heater of the auxiliary catalyst 79 is turned on. In this way, reproduction control is performed. In the following step 184, when the time tV has not elapsed since the start of the reproduction control, it is determined whether or not the time tV has elapsed. When the time tV has elapsed, the process proceeds to step 185.
[0104]
In step 185, the switching valve 61 is returned or maintained to the forward flow position or the reverse flow position, and in the subsequent step 186, the electric heater of the auxiliary catalyst 79 is turned off.
[0105]
Next, another embodiment of the reproduction control will be described with reference to FIG. In the embodiment shown in FIG. 22, the auxiliary catalyst 79 is constituted by a catalyst not provided with an electric heater. However, the embodiment shown in FIG. 22 can also be applied when the auxiliary catalyst 79 is composed of a catalyst with an electric heater.
[0106]
Also in the embodiment shown in FIG. 22, the temperature increase control described with reference to FIGS. 7 to 13 is executed. That is, when the temperature raising control is to be executed as indicated by the arrow X in FIG. . As a result, the temperature T of the exhaust gas flowing out from the auxiliary catalyst 79 gradually increases.
[0107]
However, if the oxidizing ability of the auxiliary catalyst 79 is reduced by SOF, the exhaust gas temperature T does not rise rapidly. Therefore, in the embodiment shown in FIG. 22, for example, when the exhaust gas temperature T is lower than the allowable lower limit temperature TC when the time tA has elapsed since the start of the temperature increase control, the temperature increase control is stopped and the auxiliary catalyst 79 is stopped. Playback control is started. In this case, the allowable lower limit temperature TC is set lower than the lower limit value TL of the target temperature, as can be seen from FIG.
[0108]
More specifically, the switching valve 61 is switched to the backflow position and held while stopping the reducing agent supply action from the reducing agent supply valve 77. When the temperature raising control is started, even if the oxidizing ability of the auxiliary catalyst 79 is reduced, a part of the reducing agent is oxidized in the particulate filter 69 and the temperature of the particulate filter 69 is somewhat increased. Accordingly, if the switching valve 61 is held at the backflow position at this time, the exhaust gas flowing into the particulate filter 69 is heated by the particulate filter 69, and the exhaust gas having reached a high temperature then flows into the auxiliary catalyst 79. Thus, the SOF on the auxiliary catalyst 79 is removed. Next, when, for example, time tB elapses after the regeneration control is started, the switching valve 61 is switched to the forward flow position, for example.
[0109]
FIG. 23 shows a routine for executing the regeneration control shown in FIG. This routine is executed only once when the temperature raising control is started.
[0110]
Referring to FIG. 23, first, at step 180a, it is judged if time tA has elapsed since the temperature raising control was started. When the time tA has elapsed, the routine proceeds to step 181a, where it is determined whether or not the exhaust gas temperature T is lower than the allowable reduction temperature TC. When T ≧ TC, the processing cycle is terminated, that is, the temperature rise control is continued. On the other hand, when T <TC, the routine proceeds to step 182a where temperature increase control is stopped. In the subsequent step 183a, the switching valve is switched to the backflow position and held. In this way, re-control is performed. In the following step 184a, it is determined whether or not a time tB has elapsed since the start of the reproduction control. When the time tB has elapsed, the process proceeds to step 185a, and the switching valve 61 is switched to the forward flow position, for example.
[0111]
By the way, NO supported on the particulate filter 69._XThe catalyst 81 is NO as described above._XHas accumulation and reduction action. However, this NO_XNO to obtain accumulation and reduction_XThe temperature of the catalyst 81 needs to be maintained at a temperature higher than the so-called activation temperature.
[0112]
Therefore, in an embodiment according to the present invention, NO_XActivation control is performed to maintain the temperature of the catalyst 81 at its activation temperature, for example, 200 ° C. or higher. This activation control will be described with reference to FIG.
[0113]
In FIG. 24, an arrow S indicates when activation control should be started. In the embodiment shown in FIG. 24, when the engine start is started and the filter temperature T is NO._XIt is determined that the activation control should be started when the temperature is lower than the activation temperature of the catalyst 81. At this time, as shown in FIG. 24, the switching valve 61 is held in the bypass position, the electric heater of the auxiliary catalyst 79 is turned on, however, no reducing agent is supplied from the reducing agent supply valve 77. In this way, activation control is started. As a result, the temperature of the auxiliary catalyst 79 can be quickly increased.
[0114]
Next, for example, when the time tD elapses after the activation control is started, the switching valve 61 is switched to the weak forward flow position, and at this time, the opening degree D of the switching valve 61 is set to, for example, D1 described above. Further, the reducing agent is supplied from the reducing agent supply valve 77 while keeping the air-fuel ratio of the exhaust gas flowing into the auxiliary catalyst 79 and the particulate filter 69 lean, and at this time, the reducing agent supply amount QR per unit time is For example, it is set to QR1. As a result, after the reducing agent is vaporized or partially oxidized by the relatively hot auxiliary catalyst 79, NO_XTo the catalyst 81 and therefore NO_XThe temperature of the catalyst 81 can be quickly increased.
[0115]
For example, when the time tE has elapsed since the start of the reducing agent supply operation, the opening D of the switching valve 61 is gradually increased by dd, for example, to the forward flow position, and the reducing agent supply amount QR is gradually decreased by rr to zero. The That is, if the opening degree D of the switching valve 61 is increased, NO_XSince the space velocity of the exhaust gas in the catalyst 81 increases, NO_XThe amount of the reducing agent flowing out from the catalyst 81 can be increased. Therefore, in the embodiment shown in FIG. 24, as the opening degree D of the switching valve 61 is increased, the reducing agent supply amount QR is decreased, and NO._XThe amount of the reducing agent flowing out from the catalyst 81 is suppressed. This means that the supplied reducing agent is NO_XIt also shows that the catalyst 81 is effectively utilized for increasing the temperature.
[0116]
Next, for example, when the time tF has elapsed since the reduction agent supply amount QR is decreased, the switching valve 61 is positioned at the forward flow position, and the reduction agent supply amount QR becomes zero. At this time, the electric heater of the auxiliary catalyst 79 is turned off. In this way, activation control is completed.
[0117]
FIG. 25 shows a routine for executing the activation control shown in FIG. This routine is executed by interruption every predetermined time.
[0118]
Referring to FIG. 25, first, at step 200, it is judged if activation control should be started. When activation control should not be started, the processing cycle is ended, and when activation control should be started, the process proceeds to step 201. In step 201, the switching valve 61 is switched to the bypass position, that is, D = 0. In the subsequent step 202, the electric heater of the auxiliary catalyst 79 is turned on. In this way, activation control is started. In the next step 203, it is determined whether or not the time tD has elapsed since the activation control was started. When the time tD has elapsed, the routine proceeds to step 204 where the switching valve 61 is switched to the weak forward flow position and held, and at this time, the opening degree D is set to D1 described above. In the following step 205, the reducing agent supply action from the reducing agent supply valve 77 is started, and at this time, the reducing agent supply amount QR is set to the above-described QR1.
[0119]
In the next step 206, it is determined whether or not the time tE has elapsed since the reducing agent supply operation was started. When the time tE has elapsed, the routine proceeds to step 207, where an increase dd (= (100−D1) / tF) of the opening degree D of the switching valve 61 and a decrease rr (= QR1 / tF) of the reducing agent supply amount QR are calculated. The In the next step 208, the opening degree D of the switching valve 61 and the reducing agent supply amount QR are updated (D = D + dd, QR = QR−rr). In the following step 209, it is determined whether or not the time tF has elapsed since the reducing agent supply amount QR is decreased. When the time tF has elapsed, the routine proceeds to step 210, where the electric heater of the auxiliary catalyst 79 is turned off. In this way, activation control is completed.
[0120]
The temperature increase control including the temperature increase rate maintenance control and the temperature maintenance control, the preheating control, the regeneration control, and the activation control described so far can be applied to the internal combustion engine shown in FIGS. 26 and 28, for example.
[0121]
In the internal combustion engine shown in FIG. 26, a casing 267 is connected to the outlet of the exhaust pipe 20a, and the casing 267 is connected to the casing 268 via the exhaust pipe 20b. Further, the casing 268 is connected to the casing 275 via the exhaust pipe 20 c, and the casing 275 is connected to the exhaust pipe 23. In these casings 267, 268, 275, auxiliary catalyst 79, NO_XThe particulate filter 69 carrying the catalyst 81 and the catalyst 76 are accommodated.
[0122]
A bypass pipe 285 is branched from the exhaust pipe 20a, and an outflow end of the bypass pipe 285 opens to the exhaust pipe 20c. Further, a switching valve 261 that is controlled by an electronic control unit (not shown) is disposed in a portion of the exhaust pipe 20a where the inflow end of the bypass pipe 285 is open. Further, a reducing agent supply valve 77 is disposed in the exhaust pipe 20 a between the inflow end of the bypass pipe 285 and the auxiliary catalyst 79.
[0123]
The switching valve 261 is normally held in the normal position indicated by the solid line in FIG. When the switching valve 261 is held in this normal position, the bypass pipe 285 is shut off, and almost all exhaust gas flowing into the exhaust pipe 20a is guided into the particulate filter 69. Therefore, the normal position of the switching valve 261 corresponds to the forward flow position or the reverse flow position of the switching valve 61 in the internal combustion engine of FIG.
[0124]
For example, when the temperature raising control described with reference to FIGS. 7 to 12 is to be performed, the switching valve 261 is switched to the weak flow position indicated by the one-dot chain line in FIG. 27 and temporarily held. When the switching valve 261 is held at this weak flow position, a small part of the exhaust gas that has flowed into the exhaust pipe 20 a is guided into the particulate filter 69 and the remaining exhaust gas is guided into the bypass pipe 285. Therefore, the weak flow position of the switching valve 261 corresponds to the weak forward flow position of the switching valve 61 in the internal combustion engine of FIG. At the same time, the electric heater of the auxiliary catalyst 79 is temporarily turned on, and the reducing agent is temporarily supplied from the reducing agent supply valve 77. At this time, for example, the opening degree or position of the switching valve 261 is controlled so that the temperature increase rate and temperature of the particulate filter 69 are maintained at the corresponding target values.
[0125]
The switching valve 261 can also be held at the bypass position indicated by the broken line in FIG. When the switching valve 261 is held in this bypass position, almost all the exhaust gas that has flowed into the exhaust pipe 20a flows into the bypass pipe 285, and does not flow into the auxiliary catalyst 79 and the particulate filter 69. Therefore, the bypass position of the switching valve 261 corresponds to the bypass position of the switching valve 61 in the internal combustion engine of FIG.
[0126]
On the other hand, in the internal combustion engine shown in FIG. 28, the exhaust pipe 20a is formed of a Y-shaped pipe having a pair of branch pipes 291 ′ and 291 ″, and casings 67 ′ and 67 ″ are connected to the outlets of the branch pipes, respectively. The The casings 67 ′ and 67 ″ are connected to the corresponding casings 68 ′ and 68 ″ via the exhaust pipes 20b ′ and 20b ″. Further, the casings 68 ′ and 68 ″ are connected to the branch pipes 292 ′ and 292 ′ of the exhaust pipe 20c. 292 ″ and connected to the casing 275 via the exhaust pipe 20c. The casing 275 is connected to the exhaust pipe 23. Within these casings 67 ′ and 67 ″, the first and second auxiliary catalysts 79 ′ are connected. 79 ″, respectively, first and second particulate filters 69 ′ and 69 ″ are accommodated in the casings 68 ′ and 68 ″, respectively, and a catalyst 76 is accommodated in the casing 275. On the first and second particulate filters 69 'and 69 ", the first and second NOs are respectively provided._XCatalysts 81 'and 81 "are supported.
[0127]
First and second switching valves 61 ′ and 61 ″ driven by a common actuator 260 are disposed in the branch pipe of the exhaust pipe 20c. The first and second switch valves 61 ′ and 61 ″ are disposed in the branch pipe of the exhaust pipe 20a. Reducing agent supply valves 77 ′ and 77 ″ are arranged, respectively. The actuator 261 and the reducing agent supply valves 77 'and 77 "are controlled by an electronic control unit (not shown).
[0128]
The switching valves 61 ′ and 61 ″ are normally held at the first position indicated by the solid line in FIG. 29A or the second position indicated by the broken line. When held in the position, the first switching valve 61 ′ is held in the fully open position, and the second switching valve 61 ″ is held in the fully closed position, and therefore, as shown by the solid line arrow in FIG. Almost all the exhaust gas flowing into the exhaust pipe 20a is guided into the first particulate filter 69 '. On the other hand, when the switching valves 61' and 61 "are held in the second position, the first particulate filter 69 ' The switching valve 61 ′ is held in the fully closed position, and the second switching valve 61 ″ is held in the fully opened position. Therefore, almost all of the gas flowing into the exhaust pipe 20a as shown by the broken line arrow in FIG. Exhaust gas is introduced into the second particulate filter 69 " . Accordingly, the first and second positions of the switching valves 61 'and 61 "correspond to the normal position or the bypass position of the switching valve 261 in the internal combustion engine of FIG.
[0129]
When the temperature raising control is to be performed, the switching valves 61 'and 61 "are switched to the first and second intermediate positions. That is, the first particulate filter 69' or the first NO._XWhen the temperature rise control of the catalyst 81 ′ is to be performed, the switching valves 61 ′ and 61 ″ are switched to the first intermediate position indicated by the solid line in FIG. 29B. The switching valves 61 ′ and 61 ″ are the first intermediate position. When held in the position, the first switching valve 61 ′ is held at an intermediate position between the fully opened position and the fully closed position, and the second switching valve 61 ″ is held in the fully opened position. Therefore, in FIG. As indicated by the solid line arrow, a small part of the exhaust gas flowing into the exhaust pipe 20a is guided into the first particulate filter 69 ', and the remaining exhaust gas is supplied to the second particulate filter 69 ". Led in. At the same time, the electric heater of the first auxiliary catalyst 79 ′ is temporarily turned on, and the reducing agent is temporarily supplied from the first reducing agent supply valve 77 ′. At this time, for example, the opening or position of the switching valve 61 ′ or the switching valve 61 ″ is controlled so that the temperature increase rate and temperature of the first particulate filter 69 ′ are maintained at the corresponding target values.
[0130]
On the other hand, the second particulate filter 69 "or the second NO_XWhen the temperature raising control of the catalyst 81 ″ is to be performed, the switching valves 61 ′ and 61 ″ are switched to the second intermediate position indicated by the broken line in FIG. When the switching valves 61 ′ and 61 ″ are held at the second intermediate position, the first switching valve 61 ′ is held at the fully opened position, and the second switching valve 61 ″ is intermediate between the fully opened position and the fully closed position. Therefore, a slight part of the exhaust gas flowing into the exhaust pipe 20a is guided into the second particulate filter 69 "as shown by the broken arrow in FIG. The exhaust gas is introduced into the first particulate filter 69 '. At the same time, the electric heater of the second auxiliary catalyst 79 "is temporarily turned on, and the reducing agent is supplied from the second reducing agent supply valve 77". At this time, for example, the opening degree of the switching valve 61 ′ or the switching valve 61 ″ is maintained so that the temperature increase rate and temperature of the second particulate filter 69 ′ are maintained at the corresponding target values. The position is controlled. As described above, the first and second intermediate positions of the switching valves 61 ′ and 61 ″ correspond to the weak forward flow position of the switching valve 261 in the internal combustion engine of FIG. 26.
[0131]
Here, for example, focusing on the exhaust passage portion from the branch pipe 291 ′ of the exhaust pipe 20a to the branch pipe 292 ′ of the exhaust pipe 20c, the exhaust from the branch pipe 291 ″ of the exhaust pipe 20a to the branch pipe 292 ″ of the exhaust pipe 20c. It can be seen that the passage portion constitutes a bypass pipe similar to the bypass pipe 285 in the internal combustion engine of FIG. In this case, the second reducing agent supply valve 77 ″, the second auxiliary catalyst 79, the second particulate filter 69 ″, the second NO_XEach of the catalysts 81 "has an additional reducing agent supply valve, an additional auxiliary catalyst, an additional particulate filter, and an additional NO disposed in the bypass pipe._XThat is, it constitutes a catalyst.
[0132]
Next, rich control in the internal combustion engine of FIG. 1 will be described. In this rich control, NO_XNO stored in catalyst 81_XNO_XNO accumulated in catalyst 81_XNO to reduce the amount_XThe air-fuel ratio of the exhaust gas flowing into the catalyst 81 is temporarily switched to rich.
[0133]
In the internal combustion engine shown in FIG. 1, two different combustion, that is, first combustion and second combustion are selectively switched. This will be described first before explaining the rich control.
[0134]
FIG. 30 shows the fuel injection timing and EGR rate (= EGR gas amount / (EGR gas amount + intake air amount)), that is, the mixture combusted in the combustion chamber 5 when the engine speed and the fuel injection amount are kept constant. Air-fuel ratio AFM, smoke and NO_XIt shows an example of a simulation result showing the relationship with the amount of discharge. In FIG. 30, the solid line indicates the equal smoke emission (FSN), and the broken line indicates the equal NO._XThe discharge amount (g / kwh) is shown.
[0135]
As can be seen from FIG. 30, when the EGR rate is increased from, for example, 30% while maintaining the injection timing constant, the smoke discharge amount starts to increase. Next, when the EGR rate is further increased and the air-fuel ratio AFM of the air-fuel mixture is decreased while making the injection timing constant, the amount of smoke generated increases rapidly and reaches a peak. Next, if the EGR rate is further increased while the injection timing is made constant and the air-fuel ratio AFM of the air-fuel mixture is made smaller, the smoke suddenly decreases. The air-fuel ratio AFM of the air-fuel mixture becomes the EGR rate 65% or more while keeping the injection time constant. Smoke becomes almost zero at around 15.0. That is, almost no wrinkles occur. NO at this time_XThe amount of generated is almost zero.
[0136]
Such smoke and NO_XThe behavior of the discharge amount is also supported by the experimental example shown in FIG. FIG. 31 shows the air-fuel ratio AFM of the air-fuel mixture combusted in the combustion chamber 5 by changing the opening degree of the throttle valve 17 and the EGR rate while maintaining the fuel injection timing constant during engine low load operation (FIG. 31). Of the output torque when the horizontal axis of) is changed, and smoke, HC, CO, NO_XThe experiment example which shows the change of the discharge amount of is shown.
[0137]
Therefore, in the internal combustion engine of FIG. 1, the EGR rate is higher than the EGR rate at which the generation amount of soot peaks, and soot and NO_XCombustion is performed at an injection timing and an EGR rate at which almost no is generated. This is the first combustion. On the other hand, the second combustion is combustion that is normally performed conventionally, and the EGR rate is lower than the EGR rate at which the amount of soot generation reaches a peak. Therefore, generally speaking, the first combustion is combustion in which the amount of EGR gas supplied into the combustion chamber 5 is larger than the amount of EGR gas at which the amount of generated soot reaches a peak, and soot is hardly generated. The second combustion is combustion in which the amount of EGR gas supplied into the combustion chamber 5 is smaller than the amount of EGR gas in which the amount of generated soot reaches a peak.
[0138]
FIG. 32 shows a region R1 where the first combustion is performed and a region R2 where the second combustion is performed. In FIG. 32, a broken line P shows a point where the amount of soot is peaked, and a solid line Q shows a point where the amount of soot is almost zero when the EGR rate is further increased. As can be seen from FIG. 32, the region R1 where the first combustion is performed is on one side of the broken line P, and the region R2 where the second combustion is performed is on the other side of the broken line P.
[0139]
In the first combustion, a large amount of EGR gas and a small amount of air are supplied into the combustion chamber 5. The fuel reacts with this small amount of oxygen, and the reaction heat at this time is absorbed by the surrounding EGR gas, so that the combustion temperature does not rise so much. As a result, the fuel or hydrocarbons do not grow to the soot and are discharged from the combustion chamber 5 in the form of soot precursors or hydrocarbons in the previous state. In fact, as shown in FIG. 31, when the amount of smoke discharged becomes almost zero, the amount of HC and CO discharged increases. Also, because the combustion temperature is kept low, NO_XIs also kept low.
[0140]
Then, when the internal combustion engine shown in FIG. 1 increases the amount of EGR gas supplied into the combustion chamber while maintaining the injection timing constant, the generation amount of soot gradually increases and reaches a peak, and the injection timing is reduced. If the amount of EGR gas supplied into the combustion chamber is further increased while maintaining a constant level, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber will be lower than the soot generation temperature, and soot will hardly be generated. It can also be seen that it consists of an internal combustion engine.
[0141]
FIG. 33 shows a first operation region I in which the first combustion is performed and a second combustion region II in which the second combustion is performed. In FIG. 33, LX (N) indicates the first boundary between the first operation region I and the second operation region II, and LY (N) indicates the first operation region I and the second operation region II. The 2nd boundary is shown. The change determination of the operation region from the first operation region I to the second operation region II is performed based on the first boundary LX (N), and the second operation region II to the first operation region I is determined. The change determination of the operation region is performed based on the second boundary LY (N). That is, when the required load L exceeds the first boundary LX (N) that is a function of the engine speed N when the engine operating state is in the first operating region I and the first combustion is performed. It is determined that the operation region has moved to the second operation region II, and the operation is switched to the second combustion. Next, when the required load L becomes lower than the second boundary LY (N) that is a function of the engine speed N, it is determined that the operating region has shifted to the first operating region I, and the second combustion is changed to the first combustion. Switched.
[0142]
Next, the operation control of the internal combustion engine of FIG. 1 will be described with reference to FIGS. Referring to FIG. 34, first, at step 220, it is judged if the flag I indicating that the engine operating region is the first operating region I is set. When the flag I is set, that is, when the engine operating region is the first operating region I, the routine proceeds to step 221 where the required load L becomes larger than the first boundary LX (N) shown in FIG. It is determined whether or not.
[0143]
When L ≦ LX (N), the routine proceeds to step 222, where the opening of the throttle valve 17 is controlled to an opening corresponding to the required load L shown in the first operation region I of FIG. Next, at step 223, the opening degree of the EGR control valve 25 is controlled to an opening degree corresponding to the required load L shown in the first operation region I of FIG. Next, at step 224, the injection amount, the injection start timing θS, and the injection completion timing θE corresponding to the required load L shown in the first operation region I of FIG. 35 are obtained, and fuel injection is performed based on these.
[0144]
That is, in the example shown in FIG. 35, the opening degree of the throttle valve 17 is gradually increased from nearly fully closed to about half-opening as the required load L increases, and the opening degree of the EGR control valve 25 increases the required load L. As it is increased from close to fully open. At this time, the EGR rate is, for example, about 70%, and the air-fuel ratio AFM of the air-fuel mixture formed in the combustion chamber 5 is reduced as the required load L increases, and reaches a target lean air-fuel ratio of about 15 to 18. Maintained. Further, the fuel injection is performed before the compression top dead center TDC, and the injection start timing θS is delayed as the required load L increases, and the injection completion timing θE is also delayed as the injection start timing θS is delayed.
[0145]
On the other hand, if it is determined in step 221 that L> LX (N), the routine proceeds to step 225, where the flag I is reset. Next, the routine proceeds to step 227, where the opening degree of the throttle valve 17 is controlled to an opening degree corresponding to the required load L shown in the second operation region II of FIG. That is, the throttle valve 17 is fully opened. Next, at step 228, the opening degree of the EGR control valve 25 is controlled to an opening degree corresponding to the required load L shown in the second operation region II of FIG. Next, at step 229, an injection amount, an injection start timing θS and an injection completion timing θE corresponding to the required load L shown in the second operation region II of FIG. 35 are obtained, and fuel injection is performed based on these.
[0146]
That is, in the example shown in FIG. 35, the throttle valve 17 is held in the fully open state, and the opening degree of the EGR control valve 25 is reduced as the required load L increases. At this time, the EGR rate is, for example, 40% or less, and the air-fuel ratio AFM of the air-fuel mixture formed in the combustion chamber 5 is reduced as the required load L increases, and reaches a target lean air-fuel ratio of about 24 to 60. Maintained. Further, the injection start timing θS is set near the compression top dead center TDC.
[0147]
On the other hand, when it is determined in step 220 that the flag I is reset, that is, when the engine operating region is the second operating region II, the routine proceeds to step 226, where the required load L is the second boundary shown in FIG. It is determined whether or not it has become smaller than LY (N). When L ≧ LY (N), the routine proceeds to step 227. On the other hand, when L <LY (N), the routine proceeds to step 230 where the flag I is set, and then the routine proceeds to step 222.
[0148]
In this case, when the first combustion is switched to the second combustion or vice versa, the EGR rate is increased or decreased in a stepped manner, and the air-fuel ratio AFM of the air-fuel mixture is increased or decreased in a stepped manner. As a result, since the EGR rate exceeds the EGR rate range where a large amount of smoke is generated, a large amount of smoke is not generated when switching combustion.
[0149]
Now, the rich control in the embodiment shown in FIG. 1 will be described with reference to FIGS. 36 and 37. FIG.
[0150]
FIG. 36 shows the rich control when the first combustion is performed. That is, as shown by the arrow XX in FIG._XCalculated accumulated NO in catalyst 81_XWhen the amount QN exceeds the above-described allowable value QN1, the switching valve 61 is switched from the forward flow position to the reverse flow position, for example. At this time, the air-fuel ratio AFM of the air-fuel mixture combusted in the combustion chamber 5 is switched to rich. As a result, NO_XThe air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 becomes rich, and therefore NO._XNO stored in catalyst 81_XIs reduced and NO_XNO accumulated in catalyst 81_XThe amount is reduced. In this case, the reducing agent is not supplied from the reducing agent supply valve 77.
[0151]
When the first combustion is performed, as described above, soot and NO_XThe air-fuel ratio AFM of the air-fuel mixture can be made rich without increasing the amount of exhaust gas. In this case, the amount of fuel required to switch the air-fuel ratio AFEX of the exhaust gas to rich can be reduced. Therefore, in the embodiment according to the present invention, the air-fuel ratio AFM of the air-fuel mixture is switched to rich in order to switch the air-fuel ratio AFEX of the exhaust gas to rich when the first combustion is being performed.
[0152]
On the other hand, until the rich control is performed, the air-fuel ratio of the exhaust gas flowing through the auxiliary catalyst 79 is kept lean, and thus oxygen adheres to the surface of the catalyst particles of the auxiliary catalyst 79. Accordingly, if the switching valve 61 is held in the forward flow position when the air-fuel ratio AFM of the air-fuel mixture is switched to rich, NO_XNO stored in catalyst 81_XIn order to reliably reduce the air-fuel ratio, it is necessary to deepen the richness of the air-fuel ratio AFM of the air-fuel mixture or to lengthen the time during which the air-fuel ratio AFM of the air-fuel mixture is kept rich.
[0153]
Therefore, in the embodiment according to the present invention, when the first combustion is performed, and the air-fuel ratio AFM of the air-fuel mixture is switched to rich, the switching valve 61 is held at the backflow position. In this way, the exhaust gas is NO._XAfter flowing through the catalyst 81, it flows through the auxiliary catalyst 79, and therefore is not affected by oxygen adhering to the auxiliary catalyst 79.
[0154]
Next, as shown by the arrow YY in FIG._XFor example, when time tG elapses after the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 is switched to rich, the air-fuel ratio AFM of the air-fuel mixture is returned to lean, and the switching valve 61 is returned to its original position. At this time, the accumulated NO_XThe quantity QN is returned to zero.
[0155]
On the other hand, FIG. 37 shows the rich control when the second combustion is performed. That is, as shown by arrow XX in FIG._XCalculated accumulated NO in catalyst 81_XWhen the amount QN exceeds the allowable value QN1 described above, the switching valve 61 is switched from, for example, a backflow position to a forward flow position. At this time, NO_XThe reducing agent is supplied from the reducing agent supply valve 77 so that the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 becomes rich. As a result, NO_XNO stored in catalyst 81_XIs reduced and NO_XNO accumulated in catalyst 81_XThe amount is reduced. In this case, the air-fuel ratio AFM of the air-fuel mixture burned in the combustion chamber 5 is maintained lean.
[0156]
When the air-fuel ratio AFM of the air-fuel mixture is made rich during the second combustion, a large amount of soot is generated. Therefore, when the second combustion is being performed, the reducing agent is supplied from the reducing agent supply valve 77 in order to switch the air-fuel ratio AFEX of the exhaust gas to be rich.
[0157]
In this case, the reducing agent in the form of droplets supplied from the reducing agent supply valve 77 is NO._XEven if it flows into the catalyst 81, it is not immediately oxidized, and the open end of the exhaust gas passage 70 of the particulate filter 69 may be blocked. Therefore, in the embodiment according to the present invention, the second combustion is performed, and therefore when the reducing agent is supplied from the reducing agent supply valve 77, the switching valve 61 is held in the forward flow position. In this way, after the reducing agent has circulated through the auxiliary catalyst 79, NO_XIt flows into the catalyst 81 and is vaporized or partially oxidized in the auxiliary catalyst 79 at this time. As a result, the reducing agent is NO_XIt becomes possible to react quickly in the catalyst 81.
[0158]
Next, as shown by the arrow YY in FIG._XFor example, when the time tH elapses after the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 is switched to rich, the reducing agent supply action is stopped and the switching valve 61 is returned to the original position. At this time, the accumulated NO_XThe quantity QN is returned to zero.
[0159]
FIG. 38 shows a routine for executing the rich control in the internal combustion engine of FIG. 1 described above. This routine is executed by interruption every predetermined time.
[0160]
Referring to FIG. 38, first, in step 240, NO_XCalculated accumulated NO in catalyst 81_XA quantity QN is calculated. Accumulated NO in this calculation_XThe quantity QN is for example NO_XNO per unit time when the air-fuel ratio of the exhaust gas flowing into the catalyst 81 is lean_XNO flowing into the catalyst 81_XCan be obtained by integrating the amount of. In the subsequent step 241, the accumulated NO_XIt is determined whether or not the amount QN is larger than the above-described allowable amount QN1. When QN ≦ QN1, the processing cycle is ended, and when QN> QN1, the process proceeds to step 242 and whether or not the flag I to be set or reset in the operation control routine of FIG. It is determined whether or not combustion is being performed. When the flag I is set, that is, when the first combustion is currently being performed, the routine proceeds to step 243, where the switching valve 61 is switched or held at the backflow position. In the following step 244, the air-fuel ratio AFM of the air-fuel mixture burned in the combustion chamber 5 is switched to rich. In the following step 245, NO_XIt is determined whether time tG has elapsed since the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 is switched to rich. When the time tG has elapsed, the routine proceeds to step 246, where the air-fuel ratio AFM is returned to lean. In the following step 247, the switching valve 61 is returned to the forward flow position or the reverse flow position, and in the subsequent step 248, the accumulated NO is calculated._XThe quantity QN is cleared.
[0161]
On the other hand, when the flag I is reset at step 242, that is, when the second combustion is currently being performed, the routine proceeds to step 249, where the switching valve 61 is switched or held at the forward flow position. In the following step 250, NO_XThe reducing agent is supplied from the reducing agent supply valve 77 so that the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 becomes rich. In the following step 251, NO_XIt is determined whether time tH has elapsed since the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 is switched to rich. When the time tH has elapsed, the routine proceeds to step 252 where the reducing agent supply action is stopped. In the following step 247, the switching valve 61 is returned to the forward flow position or the reverse flow position, and in the subsequent step 248, the accumulated NO is calculated._XThe quantity QN is cleared.
[0162]
In the example shown in FIGS. 36 to 38, when the rich control is completed, the switching valve 61 is returned to the original position. However, it is not necessary to return the switching valve 61 to the original position, that is, when the first combustion is being performed, the switching valve 61 is maintained at the reverse flow position, and when the second combustion is being performed, the switch valve 61 is at the forward flow position. You may make it hold | maintain.
[0163]
NO_XIn order to make the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 rich, the fuel can be secondarily injected from the fuel injection valve 6 in the latter half of the explosion stroke or the first half of the exhaust stroke.
[0164]
Therefore, NO_XWhen the air-fuel ratio of the exhaust gas discharged from the combustion chamber 5 is made rich to temporarily make the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81 rich, the exhaust gas is NO._XAfter flowing through the catalyst 81, the auxiliary catalyst 79 is circulated, and NO_XWhen supplying the reducing agent from the reducing agent supply valve 77 in order to temporarily enrich the air-fuel ratio AFEX of the exhaust gas flowing into the catalyst 81, the exhaust gas passes through the auxiliary catalyst 79 and then the NO._XThis means that the catalyst 81 is circulated.
[0165]
Alternatively, when the first combustion is being performed, the exhaust gas is NO._XWhile flowing through the auxiliary catalyst 79 after flowing through the catalyst 81, NO_XWhen the second combustion is performed when the air-fuel ratio of the exhaust gas discharged from the combustion chamber 5 is temporarily switched to rich to temporarily switch the air-fuel ratio of the exhaust gas flowing into the catalyst 81 to rich. NO after exhaust gas circulates in auxiliary catalyst 79_XWhile flowing through the catalyst 81, NO_XThis means that the reducing agent is temporarily supplied from the reducing agent supply valve 77 in order to temporarily switch the air-fuel ratio of the exhaust gas flowing into the catalyst 81 to rich.
[0166]
The rich control described above can also be applied to the internal combustion engine shown in FIG. 39, for example. In the internal combustion engine shown in FIG. 39, a casing 267 is connected to the outlet of the exhaust pipe 20a, and this casing 267 is connected to the casing 268 via the exhaust pipe 20b. Further, the casing 268 is connected to the casing 275 via the exhaust pipe 20 c, and the casing 275 is connected to the exhaust pipe 23. In these casings 267, 268, 275, auxiliary catalyst 79, NO_XThe particulate filter 69 carrying the catalyst 81 and the catalyst 76 are accommodated.
[0167]
A bypass pipe 285 is branched from the exhaust pipe 20a, and the outflow end of the bypass pipe 285 opens to the exhaust pipe 20b. Further, a switching valve 261 that is controlled by an electronic control unit (not shown) is disposed in a portion of the exhaust pipe 20a where the inflow end of the bypass pipe 285 is open. Further, a reducing agent supply valve 77 is disposed in the exhaust pipe 20 a between the inflow end of the bypass pipe 285 and the auxiliary catalyst 79.
[0168]
In the example shown in FIG. 39, when the first combustion is performed, the exhaust gas does not flow into the auxiliary catalyst 79 and NO._XWhile holding the switching valve 261 in the bypass position shown by the broken line in FIG. 39 so as to flow into the catalyst 81, NO_XIn order to temporarily switch the air-fuel ratio of the exhaust gas flowing into the catalyst 81 to rich, the air-fuel ratio of the exhaust gas discharged from the combustion chamber 5 is temporarily switched to rich. On the other hand, when the second combustion is being performed, the exhaust gas passes through the auxiliary catalyst 79 and then NO._XWhile holding the switching valve 261 in the normal position shown by the solid line in FIG._XIn order to temporarily switch the air-fuel ratio of the exhaust gas flowing into the catalyst 81 to rich, a reducing agent is temporarily supplied from the reducing agent supply valve 77.
[0169]
【The invention's effect】
Particulate filter, NO_XCatalyst or NO_XThe temperature of the entire particulate filter carrying the catalyst can be reliably increased.
[Brief description of the drawings]
FIG. 1 is an overall view of an internal combustion engine.
FIG. 2 is a diagram showing a structure of a catalytic converter.
FIG. 3 is a view for explaining the flow of exhaust gas when the switching valve is in a forward flow position or a reverse flow position.
FIG. 4 is a view for explaining the flow of exhaust gas when the switching valve is in a weak forward flow position.
FIG. 5 is a diagram for explaining the flow of exhaust gas when the switching valve is in the bypass position.
FIG. 6 is a partially enlarged cross-sectional view of a partition wall of a particulate filter.
FIG. 7 is a diagram for explaining temperature rise control.
FIG. 8 is a graph showing the relationship between the opening degree of the switching valve, the rate of increase in filter temperature, and the amount of exhaust gas.
FIG. 9 is a diagram showing a target temperature increase rate.
FIG. 10 is a flowchart for executing temperature rise control.
FIG. 11 is a diagram for explaining a time interval of a reducing agent supply operation.
FIG. 12 is a flowchart for executing temperature rise rate maintenance control and temperature maintenance control.
FIG. 13 is a flowchart for executing temperature increase rate maintenance control and temperature maintenance control according to another embodiment.
FIG. 14 is a flowchart for executing temperature increase rate maintenance control and temperature maintenance control according to another embodiment.
FIG. 15 is a diagram for explaining temperature rise control according to another embodiment.
FIG. 16 is a diagram showing an energization amount to the electric heater.
FIG. 17 is a flowchart for executing temperature increase control of the embodiment shown in FIG. 15;
FIG. 18 is a flowchart for executing preheating control according to the embodiment shown in FIG. 15;
FIG. 19 is a flowchart for executing temperature increase rate maintenance control and temperature maintenance control according to the embodiment shown in FIG. 15;
FIG. 20 is a diagram for explaining playback control.
FIG. 21 is a flowchart for executing temperature increase control according to the embodiment shown in FIG. 20;
FIG. 22 is a diagram for explaining playback control according to another embodiment;
FIG. 23 is a flowchart for executing temperature rise control according to the embodiment shown in FIG. 22;
FIG. 24 is a diagram for explaining activation control.
FIG. 25 is a flowchart for executing activation control;
FIG. 26 is a diagram showing another embodiment.
FIG. 27 is a view for explaining the position of the switching valve of the embodiment shown in FIG. 26;
FIG. 28 is a diagram showing another embodiment.
FIG. 29 is a view for explaining the position of the switching valve of the embodiment shown in FIG. 28;
FIG. 30 shows injection timing, EGR rate, smoke, and NO._XIt is a figure which shows the relationship with the generation amount of.
FIG. 31 is a diagram showing a smoke discharge amount and the like when the air-fuel ratio of the air-fuel mixture is changed.
FIG. 32 shows first and second fuel regions.
FIG. 33 is a diagram showing first and second operation regions.
FIG. 34 is a flowchart for executing operation control.
FIG. 35 is a diagram showing an opening degree of a throttle valve and the like.
FIG. 36 is a diagram for explaining rich control.
FIG. 37 is a diagram for explaining rich control.
FIG. 38 is a flowchart for executing rich control.
FIG. 39 is a diagram showing another embodiment.
[Explanation of symbols]
1 ... Engine body
20a ... exhaust pipe
22 ... Catalytic converter
61 ... Switching valve
64 ... Exhaust gas exhaust pipe
67 ... Annular exhaust pipe
69 ... Particulate filter
76 ... Catalyst
77 ... Reducing agent supply valve
79 ... Auxiliary catalyst
81 ... NO_Xcatalyst

Claims (11)

An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the flowing exhaust gas. a particulate filter carrying a catalyst having an air-fuel ratio of the exhaust gas flowing doth the NO _X in the exhaust gas flowing when the lean, the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lowered and NO _X catalyst amount of the NO _X are stored by reducing NO _X are stored as containing reducing agent is reduced from any one of the particulate filter carrying the NO _X catalyst The amount of exhaust gas that flows through the exhaust purification means by providing a bypass passage that extends from the exhaust passage upstream of the exhaust purification means and that controls the amount of exhaust gas that flows through the bypass passage. A bypass control valve for controlling is provided, and an exhaust temperature raising means for raising the temperature of the exhaust gas flowing into the exhaust purification means is disposed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means, The exhaust temperature raising means is composed of a reducing agent supply valve for supplying a reducing agent and an auxiliary catalyst having an oxidizing ability arranged downstream of the reducing agent supply valve, and raises the temperature of the exhaust purification means. sometimes while controlling the bypass control valve as modicum amount of exhaust gas flows into the exhaust gas purification device, so as to temporarily supply the reducing agent from the reducing agent feed valve of the exhaust temperature raising means, the exhaust gas temperature When the temperature of the exhaust gas flowing into the exhaust purification means is raised by the raising means, the rate of increase in the temperature of the exhaust gas flowing into the exhaust purification means is obtained to determine the obtained temperature rise rate in advance. The temperature increase rate is controlled to match the target increase rate, and the auxiliary catalyst is composed of a catalyst with an electric heater. When the temperature of the exhaust gas purification means is increased, the electric heater is temporarily An exhaust gas purification apparatus for an internal combustion engine, wherein the temperature increase rate is controlled by controlling an energization amount to the electric heater . An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the flowing exhaust gas. a particulate filter carrying a catalyst having an air-fuel ratio of the exhaust gas flowing doth the NO _X in the exhaust gas flowing when the lean, the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lowered and NO _X catalyst amount of the NO _X are stored by reducing NO _X are stored as containing reducing agent is reduced from any one of the particulate filter carrying the NO _X catalyst The amount of exhaust gas that flows through the exhaust purification means by providing a bypass passage that extends from the exhaust passage upstream of the exhaust purification means and that controls the amount of exhaust gas that flows through the bypass passage. A bypass control valve for controlling is provided, and an exhaust temperature raising means for raising the temperature of the exhaust gas flowing into the exhaust purification means is disposed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means, The exhaust temperature raising means is composed of a reducing agent supply valve for supplying a reducing agent and an auxiliary catalyst having an oxidizing ability arranged downstream of the reducing agent supply valve, and raises the temperature of the exhaust purification means. Sometimes the reducing agent is temporarily supplied from the reducing agent supply valve of the exhaust temperature raising means while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust purification means. When the temperature of the exhaust gas flowing into the exhaust purification means is raised by the raising means, the rate of increase in the temperature of the exhaust gas flowing into the exhaust purification means is obtained to determine the obtained temperature rise rate in advance. The temperature increase rate is controlled to match the target increase rate, and the temperature increase rate is controlled by controlling the amount of reducing agent supplied per unit time from the reducing agent supply valve. An exhaust purification device for an internal combustion engine. An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the flowing exhaust gas. a particulate filter carrying a catalyst having an air-fuel ratio of the exhaust gas flowing doth the NO _X in the exhaust gas flowing when the lean, the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lowered and NO _X catalyst amount of the NO _X are stored by reducing NO _X are stored as containing reducing agent is reduced from any one of the particulate filter carrying the NO _X catalyst configured to branch from the exhaust passage of the exhaust gas control means upstream the bypass passage is provided which extends, the amount of exhaust gas flowing through the more the exhaust gas control means to control the amount of exhaust gas flowing through the bypass passage A bypass control valve for controlling is provided, and an exhaust temperature raising means for raising the temperature of the exhaust gas flowing into the exhaust purification means is disposed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means, The exhaust temperature raising means is composed of a reducing agent supply valve for supplying a reducing agent and an auxiliary catalyst having an oxidizing ability arranged downstream of the reducing agent supply valve, and raises the temperature of the exhaust purification means. In some cases, the auxiliary catalyst is temporarily supplied from the reducing agent supply valve of the exhaust temperature raising means while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust purification means. Is composed of a catalyst with an electric heater, and when the temperature of the exhaust gas purification means is raised, the electric heater is temporarily operated, and when the temperature of the exhaust gas purification means is raised, the exhaust gas is exhausted. The bypass heater is controlled so that the amount of exhaust gas flowing into the purification means becomes substantially zero, and the electric heater is operated while stopping the reducing agent supply action from the reducing agent supply valve, and then the exhaust gas purification is performed. An exhaust emission control device for an internal combustion engine, wherein a reducing agent is supplied from a reducing agent supply valve while controlling a bypass control valve so that a slight amount of exhaust gas flows into the means and operating an electric heater . An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the flowing exhaust gas. a particulate filter carrying a catalyst having an air-fuel ratio of the exhaust gas flowing doth the NO _X in the exhaust gas flowing when the lean, the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lowered and NO _X catalyst amount of the NO _X are stored by reducing NO _X are stored as containing reducing agent is reduced from any one of the particulate filter carrying the NO _X catalyst The amount of exhaust gas that flows through the exhaust purification means by providing a bypass passage that extends from the exhaust passage upstream of the exhaust purification means and that controls the amount of exhaust gas that flows through the bypass passage. A bypass control valve for controlling is provided, and an exhaust temperature raising means for raising the temperature of the exhaust gas flowing into the exhaust purification means is disposed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means, The exhaust temperature raising means is composed of a reducing agent supply valve for supplying a reducing agent and an auxiliary catalyst having an oxidizing ability arranged downstream of the reducing agent supply valve, and raises the temperature of the exhaust purification means. Sometimes the reducing agent is temporarily supplied from the reducing agent supply valve of the exhaust temperature raising means while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust purification means, and the bypass passage An additional exhaust purification means is disposed within the bypass passage between the branch passage of the bypass passage and the additional exhaust purification means to increase the temperature of the exhaust gas flowing into the additional exhaust purification means. An additional exhaust temperature raising means is disposed, and the additional exhaust temperature raising means is provided with an additional reducing agent supply valve for supplying a reducing agent and an oxidizing ability arranged downstream of the reducing agent supply valve. When the temperature of the additional exhaust purification means is raised, the additional exhaust temperature is controlled while controlling the bypass control valve so that a slight amount of exhaust gas flows into the additional exhaust purification means. An exhaust emission control device for an internal combustion engine, wherein a reducing agent is temporarily supplied from an additional reducing agent supply valve of an ascending means . An exhaust purification means is disposed in an exhaust passage of an internal combustion engine where combustion is continuously performed under a lean air-fuel ratio, and the exhaust purification means is used to collect particulates in the flowing exhaust gas. a particulate filter carrying a catalyst having an air-fuel ratio of the exhaust gas flowing doth the NO _X in the exhaust gas flowing when the lean, the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lowered and NO _X catalyst amount of the NO _X are stored by reducing NO _X are stored as containing reducing agent is reduced from any one of the particulate filter carrying the NO _X catalyst The amount of exhaust gas that flows through the exhaust purification means by providing a bypass passage that extends from the exhaust passage upstream of the exhaust purification means and that controls the amount of exhaust gas that flows through the bypass passage. A bypass control valve for controlling is provided, and an exhaust temperature raising means for raising the temperature of the exhaust gas flowing into the exhaust purification means is disposed in the exhaust passage between the branch portion of the bypass passage and the exhaust purification means, The exhaust temperature raising means is composed of a reducing agent supply valve for supplying a reducing agent and an auxiliary catalyst having an oxidizing ability arranged downstream of the reducing agent supply valve, and raises the temperature of the exhaust purification means. Sometimes, while controlling the bypass control valve so that a slight amount of exhaust gas flows into the exhaust purification means, the reducing agent is temporarily supplied from the reducing agent supply valve of the exhaust temperature raising means, Flow direction switching capable of selectively switching between flowing through the exhaust gas purification means after flowing through the exhaust gas temperature raising means or flowing through the exhaust gas purification means after flowing through the exhaust gas purification means. Means for increasing the temperature of the exhaust gas purification means so that a slight amount of exhaust gas flows through the exhaust gas temperature raising means after flowing through the exhaust gas temperature raising means by the flow direction switching means and the bypass control valve. However, the reducing agent is temporarily supplied from the reducing agent supply valve of the exhaust temperature raising means, and the exhaust purification means is constituted by a NO _X catalyst or a particulate filter carrying the NO _X catalyst, and the exhaust purification means In order to temporarily switch the air-fuel ratio of the flowing exhaust gas to rich, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is temporarily switched to rich, or the reducing agent is temporarily supplied from the reducing agent supply valve. It is possible to selectively switch whether to supply or not to the combustion chamber to temporarily switch the air-fuel ratio of the exhaust gas flowing into the exhaust purification means to rich. When the air-fuel ratio of the exhaust gas to be exhausted is temporarily changed to rich, the flow direction switching means is controlled so that the exhaust gas circulates in the exhaust gas temperature raising means after flowing in the exhaust gas purification means. When the reducing agent is temporarily supplied from the reducing agent supply valve in order to temporarily switch the air-fuel ratio of the exhaust gas flowing into the exhaust gas to a rich state, the flow direction switching means is controlled to cause the exhaust gas to flow through the exhaust temperature raising means An exhaust gas purification apparatus for an internal combustion engine that is configured to circulate in the exhaust gas purification means. When the amount of EGR gas supplied into the combustion chamber is increased while maintaining the injection timing constant, the amount of soot generated gradually increases and reaches a peak, and is supplied into the combustion chamber while maintaining the injection timing constant. When the amount of EGR gas is further increased, the internal combustion engine is composed of an internal combustion engine in which the fuel during combustion in the combustion chamber and the surrounding gas temperature are lower than the generation temperature of soot and soot is hardly generated. The first combustion in which the amount of EGR gas supplied to the combustion chamber is larger than the amount of EGR gas at which the generation amount of soot reaches a peak and the generation of soot hardly occurs, and the combustion is greater than the amount of EGR gas at which the generation amount of soot reaches a peak The second combustion with a small amount of EGR gas supplied into the room is selectively switched, and the air-fuel ratio of the exhaust gas flowing into the exhaust gas purification means when the first combustion is being performed. In order to temporarily switch to rich, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is temporarily switched to rich, and when the second combustion is being performed, the air-fuel ratio of the exhaust gas flowing into the exhaust purification means is 6. The exhaust gas purification apparatus for an internal combustion engine according to claim 5, wherein a reducing agent is temporarily supplied from a reducing agent supply valve in order to temporarily switch to a rich state . An exhaust purification system of an internal combustion engine according to any one of the auxiliary catalyst to the NO _X 6 claims 1 constructed from the catalyst. 7. The auxiliary catalyst is constituted by a catalyst with an electric heater, and the electric heater is temporarily operated when the temperature of the exhaust gas purification means is increased. Exhaust gas purification device for internal combustion engine. When raising the temperature of the exhaust purification means, the bypass control valve is controlled so that the amount of exhaust gas flowing into the exhaust purification means becomes almost zero, and the reducing agent supply action from the reducing agent supply valve is stopped. While the electric heater is operated, the reducing agent is supplied from the reducing agent supply valve while the bypass control valve is controlled and the electric heater is operated so that a slight amount of exhaust gas flows into the exhaust gas purification means. The exhaust emission control device for an internal combustion engine according to claim 1 or 8, wherein The energization amount to the electric heater when supplying the reducing agent from the reducing agent supply valve is set based on the amount of reducing agent supplied from the reducing agent supply valve and the temperature of the catalyst with the electric heater. The exhaust emission control device for an internal combustion engine according to any one of claims 1, 3, and 8 . The exhaust of the internal combustion engine according to any one of claims 1, 3, and 8, wherein the electric heater is temporarily operated to remove soluble organic components adhering to the auxiliary catalyst. Purification equipment.

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