JP5155671B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine. More specifically, the present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a DPF (diesel particulate filter) that collects PM (particulates) in exhaust gas.

  In the present invention, the term “rich” indicates that the air / fuel ratio of the fuel in question (hereinafter referred to as “air-fuel ratio”) is smaller than the stoichiometric air-fuel ratio, and is referred to as “lean”. The term indicates that the air / fuel ratio of the fuel in question is greater than the stoichiometric air / fuel ratio described above. In the following description, the weight ratio of air to fuel in the air-fuel mixture flowing into the engine is referred to as engine air-fuel ratio, and the weight ratio of air in the exhaust pipe to combustible gas is referred to as exhaust air-fuel ratio.

  As a method for controlling the exhaust air-fuel ratio, the exhaust air-fuel ratio is lowered (hereinafter referred to as “main injection”) by adjusting the amount of fuel injection (hereinafter referred to as “main injection”) that reduces the intake air amount of the engine and contributes to torque. , “Enriching”) and fuel injection that does not contribute to torque (hereinafter referred to as “post-injection”) and flowing unburned fuel through the exhaust passage to enrich the exhaust air-fuel ratio. . In addition, a method of directly injecting fuel into the exhaust passage (hereinafter referred to as “exhaust injection”) is also known.

  A technique for reducing the amount of PM emission by providing a DPF for collecting PM in exhaust gas in an exhaust system of a diesel engine is widely used. Since there is a limit to the amount of PM that can be collected by the DPF, a DPF regeneration process for burning the PM deposited on the DPF is appropriately executed. In recent years, various proposals have been made regarding this DPF regeneration processing technology.

For example, in Patent Document 1, a catalytic converter in which a catalyst having high oxidation performance is applied to the upstream side of the DPF in the exhaust passage is disposed, and unburned fuel is injected into the exhaust passage to exhaust the fuel. There is shown an exhaust emission control device that combusts PM accumulated in a DPF by raising the temperature of exhaust gas that is burned by a converter and flowing the exhaust gas that has reached a high temperature into the DPF.
Further, for example, in Patent Document 2, post-injection is performed instead of the above-described exhaust injection, so that fuel is burned by a catalytic converter in the same manner as the exhaust gas purification apparatus of Patent Document 1 to raise the temperature of the exhaust, and to the DPF An exhaust purification device for burning the deposited PM is shown.

By the way, besides these exhaust injection and post injection, as a method of enriching the exhaust air-fuel ratio, there is a method of providing a fuel reformer in the exhaust passage for producing a reducing gas containing carbon monoxide and hydrogen by a reforming reaction. Are known. Here, as a reforming reaction in the reforming catalyst of the fuel reformer, for example, a reaction for producing a gas containing hydrogen and carbon monoxide by a partial oxidation reaction of hydrocarbon as shown in the following formula (1) It has been known.
_{C n H m + 1 / 2nO} 2 → nCO + 1 / 2mH 2 (1)
This partial oxidation reaction is an exothermic reaction using fuel and oxygen, and the reaction proceeds spontaneously. For this reason, once reaction starts, it can continue producing hydrogen, without supplying heat from the outside. In such a partial oxidation reaction, when fuel and oxygen coexist at a high temperature, a combustion reaction as shown in the following formula (2) also proceeds in the reforming catalyst.
_{C n H m + (n +} 1 / 4m) O 2 → nCO 2 + 1 / 2mH 2 O (2)
As the reforming reaction, in addition to the partial oxidation reaction, a steam reforming reaction represented by the following formula (3) is also known.
_{C n H m + nH 2 O} → nCO + (n + 1 / 2m) H 2 (3)
This steam reforming reaction is an endothermic reaction using fuel and steam, and is not a reaction that proceeds spontaneously. For this reason, the steam reforming reaction is easily controlled with respect to the partial oxidation reaction described above. On the other hand, it is necessary to input energy such as heat supply from the outside.
Japanese Patent No. 3835241 JP-A-8-42326

However, when exhaust injection is performed as in the exhaust purification device of Patent Document 1, the unburned fuel directly contacts the catalytic converter, the temperature of the catalyst surface becomes locally high, and the catalyst such as sintering deteriorates. There is a risk that. Further, when the fuel comes into contact with the catalyst in the form of droplets, the temperature of the catalyst surface at this contact portion is locally lowered due to latent heat of vaporization, and coking may occur.
In addition, if exhaust injection is performed when the exhaust temperature is low, the exhaust temperature further decreases due to the latent heat of vaporization of the fuel supplied by exhaust injection, and liquid fuel accumulates in the exhaust passage, causing deterioration of the catalyst and exhaust system. There is a risk of corrosion of parts.

  Further, when post injection is performed as in the exhaust gas purification device of Patent Document 2, a part of the injected fuel may adhere to the wall surface of the cylinder, and this fuel may be mixed into the engine oil. In such a case, the injected fuel does not contribute to the combustion of PM, and so-called oil dilution may occur in which engine oil is diluted by this fuel.

  Further, like these exhaust gas purification apparatuses of Patent Documents 1 and 2, most of the reducing agent consumed by the oxidation reaction in the catalytic converter is hydrocarbon. Therefore, the catalytic converter needs to be maintained at a temperature at which the inflowing hydrocarbon can undergo an oxidation reaction. However, when the low load operation is continued, the temperature of the catalytic converter is lowered to a temperature at which the oxidation reaction hardly occurs, and there is a possibility that the DPF regeneration cannot be executed.

On the other hand, when the fuel reformer is provided in the exhaust passage, there are the following problems.
That is, as described above, in the case where a fuel reformer is provided in an exhaust passage in which the exhaust amount constantly varies, in order to effectively produce hydrogen with this fuel reformer, reforming of the fuel reformer is required. It is necessary to increase the reaction time between the catalyst and the exhaust. However, in order to increase the reaction time in this way, it is necessary to enlarge the reforming catalyst, which may be costly.
In order to operate the fuel reformer in a stable state, it is necessary to keep the reaction temperature in the reforming catalyst of the fuel reformer constant. However, as described above, if the fuel reformer is provided in the exhaust passage in which the oxygen amount, the water vapor amount, and the temperature constantly change, it becomes difficult to operate the fuel reformer in a stable state.

  The present invention has been made in consideration of the above-described points, and an object thereof is to provide an exhaust emission control device for an internal combustion engine that can efficiently perform DPF regeneration.

  In order to achieve the above object, an invention according to claim 1 is an internal combustion engine comprising a particulate filter (32) that is provided in an exhaust passage (4) of an internal combustion engine (1) and collects particulates in the exhaust gas. In the exhaust emission control device, a regeneration means (40) for performing regeneration processing for burning the particulates collected by the particulate filter and the exhaust passage are provided separately, and reforming the fuel to reform hydrogen and monoxide A fuel reformer for producing a reducing gas containing carbon and supplying the reducing gas into the exhaust passage from an inlet (14) provided upstream of the particulate filter in the exhaust passage. (50), and the regeneration means performs normal regeneration means (40) for performing a regeneration process without using the reducing gas produced by the fuel reformer, and the fuel reformer Heating regeneration means (40) capable of executing a regeneration process using a reducing gas produced by the above-described method, and according to a predetermined condition, the regeneration process is performed by the normal regeneration means or the heating regeneration means To switch whether to execute the reproduction process.

The invention according to claim 2 is the exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the reducing gas produced by the fuel reformer contains more carbon monoxide than hydrogen. To do.
According to a third aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first or second aspect, a reducing gas is continuously introduced between the inlet and the particulate filter in the exhaust passage. A catalytic converter (31) for oxidation is provided.
According to a fourth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to third aspects, the combustion determination for determining whether or not the particulates accumulated on the particulate filter are in a combustion state. Means (40, 29), and when it is determined that the particulate is in a combustion state, the regeneration means performs a regeneration process by the normal regeneration means, and the particulate is not in a combustion state. If it is determined, regeneration processing is executed by the heating regeneration means.
According to a fifth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fourth aspect, the oxygen concentration detection means for detecting or estimating the oxygen concentration of the exhaust gas downstream of the particulate filter in the exhaust passage. In addition, the combustion determination unit may determine whether the particulate is in a combustion state based on the oxygen concentration detected or estimated by the oxygen concentration detection unit.

According to a sixth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fourth aspect of the present invention, downstream exhaust gas temperature detection for detecting or estimating an exhaust gas temperature (TD) downstream of the particulate filter in the exhaust passage. Means (29), wherein the combustion determination means determines whether or not the particulate is in a combustion state based on the exhaust temperature (TD) detected or estimated by the downstream exhaust temperature detection means. It is characterized by.
According to a seventh aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the fourth to sixth aspects, the heating regeneration means is more preferable than the case where the regeneration process is performed by the normal regeneration means. The intake air amount (GE) of the internal combustion engine is reduced, the exhaust gas recirculation amount of the internal combustion engine is increased, or the charging efficiency of the internal combustion engine is reduced.
According to an eighth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the seventh aspect, the heating regeneration means performs a regeneration process while supplying a reducing gas into the exhaust passage by the fuel reformer. First heating regeneration means (40) for performing, and second heating regeneration means (40) for performing regeneration processing without supplying reducing gas into the exhaust passage by the fuel reformer, According to a predetermined condition, whether the regeneration process is performed by the first heating regeneration unit or the regeneration process is performed by the second heating regeneration unit is switched.
According to a ninth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the eighth aspect of the present invention, the upstream exhaust temperature for detecting or estimating the temperature (TU) of the exhaust upstream of the particulate filter in the exhaust passage. The heating regeneration unit further includes a detection unit (28), and when the temperature (TU) detected by the upstream exhaust temperature detection unit is smaller than a predetermined determination value (TCTH), the heating regeneration unit A reproduction process is executed.

A tenth aspect of the present invention is the exhaust gas purification apparatus for an internal combustion engine according to the eighth or ninth aspect, further comprising a filter temperature estimating means for estimating or detecting a temperature (TDPF) of the particulate filter, wherein the heating regeneration is performed. The means is characterized in that when the temperature (TDPF) estimated or detected by the filter temperature estimation means is smaller than a predetermined judgment value (TDTH), the regeneration processing is executed by the first heating regeneration means.
The invention according to claim 11 is the exhaust gas purification apparatus for an internal combustion engine according to any one of claims 8 to 10, further comprising torque estimation means (40) for estimating a generated torque (TRQ) of the internal combustion engine, When the generated torque (TRQ) estimated or detected by the torque estimation unit is smaller than a predetermined determination value (TRQTH), the heating regeneration unit performs a regeneration process by the first heating regeneration unit. And
According to a twelfth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the eleventh aspect, the torque estimating means sets at least one of a rotational speed, a fuel injection amount, and a fuel injection timing of the internal combustion engine. Based on this, the generated torque of the internal combustion engine is estimated.
According to a thirteenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the eighth to twelfth aspects, the time measuring means (40) for measuring an elapsed time (TIM) since the start of the internal combustion engine. The heating regeneration means performs regeneration processing by the first heating regeneration means when the elapsed time (TIM) measured by the timing means is smaller than a predetermined determination value (TIMTH). Features.

According to the first aspect of the present invention, when executing the regeneration process for burning the particulates collected by the particulate filter, the normal regeneration means for performing the regeneration process without using the reducing gas; The heating regeneration unit capable of performing the regeneration process using the reducing gas is switched according to a predetermined condition. Here, the reducing gas produced by the fuel reformer includes easily flammable molecules such as hydrogen and carbon monoxide. By supplying such a reducing gas to the particulate filter, for example, even if the exhaust gas temperature is low and it is difficult to burn the particulates, the exhaust gas temperature can be quickly raised. Further, by switching between the normal regeneration means and the heat regeneration means according to a predetermined condition, for example, in the conventional method as described above, for example, immediately after engine startup or when shifting to low load operation, the particulate filter Even if it becomes difficult to execute the reproduction process, the reproduction process can be executed. That is, the frequency at which the operating state of the internal combustion engine becomes difficult to continue the regeneration process of the particulate filter and the regeneration process must be interrupted can be reduced. Therefore, the time required for the reproduction process can be shortened.
Further, by using the reducing gas in this way, the temperature of the exhaust gas can be raised without supplying unburned fuel as in the case of exhaust injection or post injection. Thereby, problems such as the occurrence of coking as described above, deterioration and corrosion of the catalyst and parts in the exhaust passage, deterioration of fuel consumption, and generation of oil dilution can be avoided.
In addition, the molecular diameter of carbon monoxide and hydrogen contained in the reducing gas is smaller than the molecular diameter of hydrocarbons supplied by exhaust injection or post injection. For this reason, even when a large amount of particulates is deposited on the particulate filter, the reducing gas can be supplied together with oxygen to the deep part. Thereby, the combustion of particulates can be promoted efficiently.
Further, by providing a fuel reformer for producing reducing gas separately from the exhaust passage, the regeneration timing of the particulate filter can be determined independently of the state of the internal combustion engine. Therefore, the regeneration process of the particulate filter can be appropriately executed as necessary while always controlling the internal combustion engine in an optimal state. In addition, by providing a fuel reformer separately from the exhaust passage, it is possible to always produce reducing gas with optimum efficiency regardless of the operating state of the internal combustion engine, the oxygen concentration and the water vapor concentration of the exhaust gas, etc. Sexual gas can be supplied into the exhaust passage.
On the other hand, when the fuel reformer is provided in the exhaust passage, it is necessary to enlarge the fuel reformer so that the fuel reformer can be operated without affecting the exhaust components, temperature, and flow velocity. Accordingly, by providing the fuel reformer separately from the exhaust passage, stable operation can be performed without increasing the size of the apparatus. Further, by providing the fuel reformer separately from the exhaust passage, it is possible to activate the catalyst included in the fuel reformer at an early stage by performing control of a system different from the control of the internal combustion engine.

According to the invention described in claim 2, the reducing gas contains more carbon monoxide than hydrogen. Carbon monoxide burns at a lower temperature than hydrogen. By supplying such a reducing gas containing carbon monoxide, the particulates deposited on the particulate filter can be burned efficiently.
According to the third aspect of the present invention, the reducing gas produced by the fuel reformer flows into the catalytic converter and burns in the catalytic converter. By burning the reducing gas in the catalytic converter in this way, the temperature of the exhaust gas can be raised, and the particulates deposited on the particulate filter can be burned efficiently.
According to the fourth aspect of the present invention, when it is determined that the particulate deposited on the particulate filter is in a combustion state, the regeneration process is performed by the normal regeneration means without using the reducing gas, and the particulate When it is determined that is not in the combustion state, the regeneration process is performed using the reducing gas by the heating regeneration unit. Accordingly, it is possible to efficiently execute the regeneration process while preventing the reducing gas from being consumed wastefully.
According to the fifth aspect of the present invention, it is determined whether or not the particulate is in the combustion state based on the oxygen concentration in the exhaust gas downstream of the particulate filter. Thereby, the combustion state of the particulate can be determined with high accuracy.
According to the sixth aspect of the present invention, it is determined whether or not the particulate is in the combustion state based on the exhaust gas temperature on the downstream side of the particulate filter. Thereby, the combustion state of the particulate can be determined with high accuracy.

According to the invention described in claim 7, when the regeneration process is performed by the heating regeneration unit, the intake air amount of the internal combustion engine is reduced as compared with the case where the regeneration process is performed by the normal regeneration unit, Increase the exhaust gas recirculation amount of the internal combustion engine or reduce the charging efficiency of the internal combustion engine. By executing the regeneration process with such a heat regeneration means, the temperature of the particulate filter can be quickly raised.
According to the eighth aspect of the present invention, the first heat regeneration means for executing the regeneration process while supplying the reducing gas to the heat regeneration processing means, and the first process for performing the regeneration process without supplying the reducing gas. 2 heating regeneration means is provided, and the first heating regeneration means and the second heating regeneration means are switched according to a predetermined condition. Thereby, the reproduction process can be appropriately executed according to the conditions.
According to the ninth aspect of the present invention, when the exhaust temperature upstream of the particulate filter is lower than the predetermined determination value, the regeneration process is executed while supplying the reducing gas by the first heating regeneration unit. Thereby, even in a state where the exhaust gas temperature is low and it is difficult to burn the particulates, the exhaust gas temperature can be quickly raised to promote the burning of the particulates.

According to the tenth aspect of the present invention, when the temperature of the particulate filter is lower than the predetermined determination value, the regeneration process is executed while supplying the reducing gas by the first heating regeneration means. As a result, even when the temperature of the particulate filter is low and it is difficult to burn the particulates, the exhaust gas temperature can be quickly raised to promote the burning of the particulates.
According to the eleventh aspect of the present invention, when the generated torque is smaller than the predetermined determination value, the regeneration process is executed while supplying the reducing gas by the first heating regeneration means. As a result, even when the internal combustion engine is in a low-load operation state and the particulates are hardly combusted, the exhaust gas temperature can be quickly raised to promote the combustion of the particulates.
According to the thirteenth aspect of the present invention, when the elapsed time since the start of the internal combustion engine is smaller than the predetermined determination value, the regeneration process is executed while supplying the reducing gas. Thereby, even in a state where it is difficult to burn the particulates soon after the internal combustion engine is started, the exhaust gas temperature can be quickly raised to promote the burning of the particulates.

  FIG. 1 is a diagram showing a configuration of an internal combustion engine and an exhaust purification device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into the combustion chamber of each cylinder 7, and each cylinder 7 is provided with a fuel injection valve (not shown). These fuel injection valves are electrically connected by an electronic control unit (hereinafter referred to as “ECU”) 40, and the valve opening time and valve closing time of the fuel injection valve are controlled by the ECU 40.

  The engine 1 includes an intake pipe 2 through which intake air circulates, an exhaust pipe 4 through which exhaust gas circulates, an exhaust gas recirculation passage 6 that recirculates part of the exhaust gas in the exhaust pipe 4 to the intake pipe 2, and intake air into the intake pipe 2. And a supercharger 8 for pressure-feeding.

  The intake pipe 2 is connected to the intake port of each cylinder 7 of the engine 1 through a plurality of branch portions of the intake manifold 3. The exhaust pipe 4 is connected to the exhaust port of each cylinder 7 of the engine 1 through a plurality of branch portions of the exhaust manifold 5. The exhaust gas recirculation passage 6 branches from the exhaust manifold 5 and reaches the intake manifold 3.

  The supercharger 8 includes a turbine (not shown) provided in the exhaust pipe 4 and a compressor (not shown) provided in the intake pipe 2. The turbine is driven by the kinetic energy of the exhaust flowing through the exhaust pipe 4. The compressor is rotationally driven by the turbine, pressurizes the intake air, and pumps it into the intake pipe 2. The turbine includes a plurality of variable vanes (not shown), and is configured to change the turbine rotation speed (rotational speed) by changing the opening of the variable vanes. The vane opening degree of the turbine is electromagnetically controlled by the ECU 40.

  A throttle valve 9 for controlling the intake air amount GA of the engine 1 is provided upstream of the supercharger 8 in the intake pipe 2. The throttle valve 9 is connected to the ECU 40 via an actuator, and the opening degree is electromagnetically controlled by the ECU 40. In addition, an intercooler 11 for cooling the intake air pressurized by the supercharger 8 is provided on the downstream side of the supercharger 8 in the intake pipe 2.

  The exhaust gas recirculation passage 6 connects the exhaust manifold 5 and the intake manifold 3 and recirculates part of the exhaust discharged from the engine 1. The exhaust gas recirculation passage 6 is provided with an EGR cooler 12 that cools the exhaust gas that is recirculated, and an EGR valve 13 that controls the flow rate of the recirculated exhaust gas. The EGR valve 13 is connected to the ECU 40 via an actuator (not shown), and the valve opening degree is electromagnetically controlled by the ECU 40.

  A catalytic converter 31 and a DPF 32 are provided in this order from the upstream side on the downstream side of the supercharger 8 in the exhaust pipe 4.

The catalytic converter 31 includes a three-way catalyst that continuously oxidizes reducing gas supplied from a fuel reformer 50 described later. The catalytic converter 31 includes rhodium (Rh) as a noble metal active species in catalytic combustion reactions such as carbon monoxide, hydrogen, and light hydrocarbons contained in a reducing gas described later, and ceria (CeO ₂ ) having oxygen storage capacity. ). By supplying the reducing gas to such a catalytic converter 31, the temperature can be quickly raised even when the exhaust gas temperature is low. Further, by containing ceria, a stable catalytic action can be exhibited even in a sudden change in oxygen concentration.
In this embodiment, as the catalytic converter 31, platinum (Pt) is 2.4 (g / L), rhodium is 1.2 (g / L), and palladium (Pd) is 6.0 (g / L). A slurry is produced by stirring and mixing 50 (g / L) of ceria, 150 (g / L) of alumina (Al ₂ O ₃ ), 10 of a binder, and an aqueous medium with a ball mill, After coating this slurry on a support made of Fe—Cr—Al alloy, a slurry prepared by drying and firing at 600 ° C. for 2 hours is used.

When the exhaust gas passes through fine holes in the filter wall, the DPF 32 collects PM mainly composed of carbon in the exhaust gas by depositing it on the surface of the filter wall and the holes in the filter wall. As a constituent material of the filter wall, for example, ceramics such as silicon carbide (SiC) or a porous metal body is used.
When PM is collected to the limit of the collection capability of the DPF 32, that is, the accumulation limit, the pressure loss increases. Therefore, it is necessary to appropriately perform a DPF regeneration process for burning the collected PM. This DPF regeneration process is performed by raising the temperature of the exhaust gas flowing into the DPF 32 to the combustion temperature of the PM collected by the DPF 32. The procedure of this DPF regeneration process will be described in detail later with reference to FIG.

Further, on the upstream side of the catalytic converter 31 and the DPF 32 in the exhaust pipe 4, a fuel reformer that reforms the fuel gas to produce a reformed gas containing hydrogen (H ₂ ) and carbon monoxide (CO). 50 is connected. The fuel reformer 50 supplies the produced reformed gas as a reducing gas into the exhaust pipe 4 from the inlet 14 formed on the upstream side of the catalytic converter 31 and the DPF 32 in the exhaust pipe 4.

  The fuel reformer 50 is provided in the gas passage 51, a gas passage 51 whose one end is connected to the exhaust pipe 4, a fuel gas supply device 52 that supplies fuel gas from the other end of the gas passage 51, and the gas passage 51. And a reforming catalyst 53 as a reforming catalyst.

  The fuel gas supply device 52 mixes fuel stored in the fuel tank and air supplied by the compressor at a predetermined ratio to produce fuel gas, and supplies the fuel gas to the gas passage 51. The fuel gas supply device 52 is connected to the ECU 40, and the fuel gas supply amount and the mixing ratio thereof are controlled by the ECU 40. Further, by controlling the supply amount of the fuel gas, the supply amount GRG of the reducing gas supplied to the exhaust pipe 4 (the amount of reducing gas supplied into the exhaust pipe 4 per unit time) can be controlled. It is possible.

  The reforming catalyst 53 contains rhodium and ceria. The reforming catalyst 53 is a catalyst that reforms the fuel gas supplied from the fuel gas supply device 52 to produce a reformed gas containing hydrogen, carbon monoxide, and hydrocarbons. More specifically, the reforming catalyst 53 has a pressure higher than atmospheric pressure due to a partial oxidation reaction between the hydrocarbon fuel constituting the fuel gas and air, and has a volume ratio of carbon monoxide higher than hydrogen. A reformed gas containing a large amount of is produced. Further, as described above, the partial oxidation reaction is an exothermic reaction. Thus, the fuel reformer 50 can supply reducing gas having a temperature higher than that of the exhaust gas in the vicinity of the inlet 14 in the exhaust pipe 4 into the exhaust pipe 4.

  The reforming catalyst 53 is connected to a heater (not shown) including a glow plug, a spark plug, and the like, so that the reforming catalyst 53 can be heated when the fuel reformer 50 is started. It is possible. The fuel reformer 50 is provided separately from the exhaust pipe 4. That is, the fuel gas supply device 52 and the reforming catalyst 53 of the fuel reformer 50 are not provided in the exhaust pipe 4.

  The ECU 40 includes an air flow meter 21 that detects an intake air amount GA of the engine 1 (amount of air newly sucked into the engine 1 per unit time), an exhaust temperature upstream of the DPF 32 and the catalytic converter 31 in the exhaust pipe 4. A downstream temperature sensor 29 that detects TU and a downstream temperature sensor 29 that detects an exhaust temperature TD downstream of the DPF 32 in the exhaust pipe 4 are connected, and detection signals from these sensors are supplied to the ECU 40.

  The ECU 40 shapes an input signal waveform from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter, “ CPU ”). In addition, the ECU 40 is a storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, a fuel reformer 50, a throttle valve 9, an EGR valve 13, a supercharger 8, and a fuel injection of the engine 1. An output circuit for outputting a control signal to a valve or the like.

  FIG. 2 is a flowchart showing a procedure of DPF regeneration processing by the ECU. As shown in FIG. 2, the DPF regeneration process includes a normal regeneration process in which the regeneration process is performed without using the reducing gas produced by the fuel reformer, and a heating regeneration process in which the regeneration process using the reducing gas can be performed. Can be switched according to a predetermined condition. Moreover, this DPF regeneration process is performed, for example, every predetermined time.

In step S1, it is determined whether or not a DPF regeneration request flag FDPFRR is “1”. If this determination is YES, the process proceeds to step S2, and if this determination is NO, this process is immediately terminated. Here, the DPF regeneration request flag FDPFRR is set to “1” when the fuel consumption reaches a predetermined value or when the travel distance of the vehicle reaches a predetermined value.
In step S2, it is determined whether or not the exhaust temperature TD downstream of the DPF detected by the downstream temperature sensor is lower than a predetermined determination temperature TATH. If this determination is YES, the PM accumulated in the DPF is burned. If it is determined that the engine is not in the state, the process proceeds to step S4. If NO, the PM is determined to be in the combustion state, and the process proceeds to step S3.

  In step S3, normal reproduction processing is executed, and the process proceeds to step S9. In this normal regeneration process, for example, the post-injection is executed to raise the temperature of the exhaust gas to the combustion temperature of PM.

In step S4, the temperature TTWC of the catalytic converter is estimated based on the exhaust gas temperature TU upstream of the catalytic converter detected by the upstream temperature sensor, and it is determined whether or not the catalytic converter temperature TTWC is lower than a predetermined determination temperature TBTH. If yes, then continue with step S7, otherwise continue with step S5.
In step S5, it is determined whether or not the engine is in a low load operation state. If this determination is YES, the process proceeds to step S7, and if NO, the process proceeds to step S6. More specifically, it is determined whether the engine is in a low load operation state by estimating the generated torque TRQ of the engine and determining whether the generated torque TRQ is smaller than a predetermined torque determination value TRQTH. To do. In the present embodiment, the generated torque TRQ of the engine is estimated based on at least one of the engine speed, the fuel injection amount, and the fuel injection timing.
In step S6, it is determined whether or not it is immediately after starting. If this determination is YES, the process proceeds to step S7, and if NO, the process proceeds to step S8. Here, the determination as to whether or not it is immediately after the start is made based on whether or not an elapsed time TIM from the start of the engine measured by a timer (not shown) is smaller than a predetermined determination time TIMTH.

In step S7, execution of the first heat regeneration process is started, and the process proceeds to step S9. In the first heat regeneration process, the throttle valve is closed to reduce the intake air amount GA to a predetermined amount, and the reducing gas produced by the fuel reformer is supplied into the exhaust pipe.
In Step S8, execution of the 2nd heating regeneration processing is started, and it moves to Step S9. In the second heat regeneration process, the throttle valve is closed to reduce the intake air amount GA to a predetermined amount. In the second heat regeneration process, the reducing gas is not supplied.
In step S9, it is determined whether or not a predetermined reproduction time has elapsed. If this determination is YES, the process proceeds to step S10, the DPF regeneration request flag is returned to “0”, and the process is terminated. If NO, the process is immediately terminated.

As described above in detail, according to the present embodiment, when performing the DPF regeneration process for burning the PM collected in the DPF 32, the normal regeneration process for performing the regeneration process without using the reducing gas; The first and second heat regeneration processes capable of performing the regeneration process using the reducing gas are switched according to a predetermined condition. Here, the reducing gas produced by the fuel reformer 50 includes easily combustible molecules such as hydrogen and carbon monoxide. By supplying such a reducing gas to the DPF 32, for example, even if the exhaust gas temperature is low and it is difficult to burn PM, the exhaust gas temperature can be quickly raised.
In addition, by switching between the normal regeneration process and the first and second heat regeneration processes according to a predetermined condition, for example, the conventional method as described above, for example, immediately after starting the engine or when shifting to a low load operation Then, even if it becomes difficult to execute the DPF regeneration process, the regeneration process can be performed. That is, it is difficult for the engine operating state to continue the DPF regeneration process, and the frequency at which the regeneration process must be interrupted can be reduced. Therefore, the time required for the reproduction process can be shortened.
Further, by using the reducing gas in this way, the temperature of the exhaust can be raised without supplying unburned fuel as in the case of exhaust injection or post injection. Thereby, problems such as the occurrence of coking as described above, deterioration and corrosion of the catalyst and parts in the exhaust passage, deterioration of fuel consumption, and generation of oil dilution can be avoided.
Further, the molecular diameter of carbon monoxide and hydrogen contained in the reducing gas is smaller than the molecular diameter of hydrocarbons supplied by exhaust injection or post injection. For this reason, even when a large amount of PM is deposited on the DPF 32, the reducing gas can be supplied to the deep portion along with oxygen. Thereby, combustion of PM can be promoted efficiently.
Further, by providing the fuel reformer 50 for producing the reducing gas separately from the exhaust pipe 4, the PM regeneration timing can be determined independently of the state of the engine 1. Therefore, the DPF regeneration process can be appropriately executed as necessary while always controlling the engine 1 in an optimal state. In addition, by providing the fuel reformer 50 separately from the exhaust pipe 4, it is possible to always produce reducing gas with optimum efficiency regardless of the operating state of the engine 1 and the oxygen concentration and water vapor concentration of the exhaust. A reducing gas can be supplied into the exhaust pipe 4.
On the other hand, when the fuel reformer 50 is provided in the exhaust pipe 4, it is necessary to make the fuel reformer 50 large so that the fuel reformer 50 can be operated without affecting the exhaust components, temperature, and flow velocity. According to the present invention, by providing the fuel reformer 50 separately from the exhaust pipe 4, a stable operation can be performed without increasing the size of the apparatus. Further, by providing the fuel reformer 50 separately from the exhaust pipe 4, the reforming catalyst 53 of the fuel reformer 50 can be activated at an early stage by controlling the system different from the control of the engine 1. Is also possible.

Further, according to the present embodiment, the reducing gas contains more carbon monoxide than hydrogen. Carbon monoxide burns at a lower temperature than hydrogen. By supplying such a reducing gas containing carbon monoxide, the PM deposited on the DPF 32 can be burned efficiently.
Further, according to the present embodiment, the reducing gas produced by the fuel reformer 50 flows into the catalytic converter 31 and burns in the catalytic converter 31. By burning the reducing gas in the catalytic converter 31 in this way, the temperature of the exhaust can be raised, and the PM deposited on the DPF 32 can be burned efficiently.
Further, according to the present embodiment, when it is determined that the PM deposited on the DPF 32 is in the combustion state, the normal regeneration process is performed, and when it is determined that the PM is not in the combustion state, the first heat regeneration is performed. The process or the first heat regeneration process is executed. As a result, the regeneration process can be executed efficiently while preventing the reducing gas from being consumed unnecessarily. Thereby, the time required for the regeneration process can be shortened according to the operating state of the engine.
Further, according to the present embodiment, it is determined whether PM is in a combustion state based on the exhaust temperature downstream of the DPF 32. Thereby, the combustion state of PM can be determined with high accuracy.

Further, according to the present embodiment, when the first and second heating regeneration processes are executed, the intake air amount of the engine 1 is reduced as compared with the case where the normal regeneration processes are executed. By executing such first and second heat regeneration processes, the temperature of the DPF 32 can be quickly raised.
Further, according to the present embodiment, when the temperature TTWC of the catalytic converter 31 is lower than the predetermined determination temperature TBTH, the first heating regeneration process is executed. As a result, even in a state where the exhaust gas temperature is low and it is difficult to burn PM, the exhaust gas temperature can be quickly raised to promote PM combustion.

Further, according to the present embodiment, when the generated torque TRQ is smaller than the predetermined determination value TRQTH, the first heating regeneration process is executed. Thereby, even if the engine 1 is in a low-load operation state and is in a state where it is difficult to burn PM, the exhaust gas temperature can be quickly raised to promote PM combustion.
Further, according to the present embodiment, when the elapsed time TIM after starting the engine 1 is smaller than the predetermined determination time TIMTH, the first heating regeneration process is executed. Thereby, even if it is in a state where it is difficult to burn PM soon after the engine 1 is started, the exhaust gas temperature can be quickly raised and the combustion of PM can be promoted.

  In the present embodiment, the ECU 40 performs regeneration means, normal regeneration means, heating regeneration means, first heating regeneration means, second heating regeneration means, combustion determination means, part of filter temperature estimation means, part of torque estimation means, and Consists of timekeeping means. Specifically, the means according to steps S1 to S10 in FIG. 2 corresponds to a regeneration means, the means according to step S3 corresponds to a normal regeneration means, the means according to steps S7 and S8 corresponds to a heating regeneration means, The means according to Step S7 corresponds to the first heating regeneration means, the means according to Step S8 corresponds to the second heating regeneration means, the means according to Step S2 and the downstream temperature sensor 29 correspond to the combustion determination means, and Step S5 The means according to the above corresponds to the torque estimating means, and the means according to step S6 corresponds to the time measuring means.

The present invention is not limited to the embodiment described above, and various modifications can be made.
In the above embodiment, the catalytic converter 31 having an oxidation function for continuously oxidizing the reducing gas is provided on the upstream side of the DPF 32 in the exhaust pipe 4. For example, a catalyst having a similar oxidation function may be supported on the DPF without providing the catalytic converter separately from the DPF.
Thereby, compared with the case where a catalytic converter and a DPF are provided separately, the exhaust purification device can be made compact, and the combustion reaction of PM can be further promoted. Therefore, it is possible to further shorten the time from the supply of the reducing gas to the start of PM combustion.

  In the above embodiment, in step S2, it is determined whether PM accumulated in the DPF is in the combustion state based on the exhaust temperature TD downstream of the DPF detected by the downstream temperature sensor 29. However, the present invention is not limited to this. Absent. For example, oxygen concentration detection means for detecting or estimating the oxygen concentration in the exhaust gas downstream of the DPF is provided, and whether or not PM is in a combustion state based on the oxygen concentration detected or estimated by the oxygen concentration detection means. You may judge. Even if it does in this way, there can exist an effect similar to the said embodiment.

  In the above embodiment, in steps S4 to S6, the first heating regeneration process is executed based on the temperature of the catalytic converter, the operating state of the engine, and the elapsed time from the start of the engine start, or the second heating regeneration process is performed. However, the present invention is not limited to this. For example, the first heating regeneration process may be performed when the exhaust gas temperature TU detected by the upstream temperature sensor is lower than a predetermined determination temperature TCTH. In addition, for example, a filter temperature estimation unit that estimates the temperature TDPF of the DPF is provided, and when the DPF temperature TDPF estimated by the filter temperature estimation unit is smaller than a predetermined determination temperature TDTH, the first heating regeneration process is executed. It may be. Even if it does in this way, there can exist an effect similar to the said embodiment.

  In the above embodiment, when the first heat regeneration process and the second heat regeneration process are executed in step S7 and step S8, the throttle valve is closed and the intake air amount GA is reduced to a predetermined amount. However, the present invention is not limited to this. . In these processes, not only the reduction of the intake air amount but also the EGR valve may be opened to increase the exhaust gas recirculation amount, or the engine charging efficiency may be reduced. Even if it does in this way, there can exist an effect similar to the said embodiment.

  The present invention can also be applied to an exhaust emission control device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

1 is a diagram illustrating a configuration of an internal combustion engine and an exhaust purification device thereof according to an embodiment of the present invention. It is a flowchart which shows the procedure of the DPF regeneration process by ECU which concerns on the said embodiment.

Explanation of symbols

1. Engine (internal combustion engine)
4 ... Exhaust pipe (exhaust passage)
5. Exhaust manifold (exhaust passage)
14 ... Inlet 28 ... Upstream temperature sensor (upstream exhaust temperature detection means)
29 ... Downstream temperature sensor (downstream exhaust temperature detection means)
31 ... Catalytic converter 32 ... DPF
40. Electronic control unit (regeneration means, normal regeneration means, heating regeneration means, first heating regeneration means, second heating regeneration means, combustion determination means, filter temperature estimation means, torque estimation means, and timing means)
50 ... Fuel reformer

Claims (11)

In an exhaust gas purification apparatus for an internal combustion engine, which is provided in an exhaust passage of the internal combustion engine and includes a particulate filter that collects particulates in the exhaust gas,
Regeneration means for executing regeneration processing for burning the particulates collected by the particulate filter;
Provided separately from the exhaust passage, the fuel is reformed by a partial oxidation reaction to produce a reducing gas containing hydrogen and carbon monoxide, and the reducing gas is upstream of the particulate filter in the exhaust passage. A fuel reformer that is supplied into the exhaust passage from an inlet provided on the side;
A catalytic converter that is provided between the inlet and the particulate filter in the exhaust passage and continuously oxidizes reducing gas;
Combustion determination means for determining whether or not the particulates deposited on the particulate filter are in a combustion state ,
The reducing gas produced by the fuel reformer contains more carbon monoxide than hydrogen,
The reproducing means includes
Normal regeneration means for performing regeneration processing without using the reducing gas produced by the fuel reformer, and heating regeneration means capable of executing regeneration processing using the reducing gas produced by the fuel reformer And switching whether to perform the regeneration process by the normal regeneration unit or the regeneration process by the heating regeneration unit according to a predetermined condition ,
The regeneration means performs regeneration processing by the normal regeneration means when it is determined that the particulate is in the combustion state, and when it is determined that the particulate is not in the combustion state, the heating means An exhaust emission control device for an internal combustion engine, wherein a regeneration process is performed by a regeneration means . Oxygen concentration detecting means for detecting or estimating the oxygen concentration of the exhaust gas downstream of the particulate filter in the exhaust passage,
2. The internal combustion engine according to claim 1 , wherein the combustion determination unit determines whether or not the particulate is in a combustion state based on the oxygen concentration detected or estimated by the oxygen concentration detection unit. Exhaust purification equipment. Further comprising a downstream exhaust temperature detecting means for detecting or estimating an exhaust temperature downstream of the particulate filter in the exhaust passage,
The internal combustion engine according to claim 2 , wherein the combustion determination unit determines whether or not the particulate is in a combustion state based on the exhaust temperature detected or estimated by the downstream exhaust temperature detection unit. Engine exhaust purification system. The heating regeneration means reduces the intake air amount of the internal combustion engine, increases the exhaust gas recirculation amount of the internal combustion engine, or increases the exhaust gas recirculation amount of the internal combustion engine as compared with the case where the regeneration process is performed by the normal regeneration means. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3 , wherein the charging efficiency of the internal combustion engine is reduced. The heating regeneration means includes a first heating regeneration means for executing a regeneration process while supplying a reducing gas into the exhaust passage by the fuel reformer, and a reducing gas from the exhaust passage by the fuel reformer. A second heating regeneration unit that performs the regeneration process without supplying to the apparatus, and performs the regeneration process by the first heating regeneration unit or performs the regeneration process by the second heating regeneration unit according to a predetermined condition. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4 , wherein whether to perform the operation is switched. Further comprising upstream exhaust temperature detection means for detecting or estimating the temperature of the exhaust on the upstream side of the particulate filter in the exhaust passage,
The heated regeneration means, when the temperature detected by the upstream exhaust gas temperature detection means is lower than a predetermined judgment value, according to claim 5, characterized in that executing the reproduction processing by the first heated regeneration means Exhaust gas purification device for internal combustion engine. A filter temperature estimating means for estimating or detecting the temperature of the particulate filter;
The heated regeneration means, wherein, when the filter temperature estimation by the estimation means or the detected temperature is less than a predetermined judgment value, claim 5 or and executes playback processing by the first heated regeneration means 6. An exhaust emission control device for an internal combustion engine according to 6 . Torque estimation means for estimating the generated torque of the internal combustion engine,
The heated regeneration means, when the estimated or detected torque by the torque estimating means is smaller than a predetermined judgment value, the claim 5, characterized in that executing the reproduction processing by the first heated regeneration means 8. An exhaust emission control device for an internal combustion engine according to any one of 7 above. 9. The internal combustion engine according to claim 8 , wherein the torque estimation means estimates a generated torque of the internal combustion engine based on at least one of a rotational speed, a fuel injection amount, and a fuel injection timing of the internal combustion engine. Engine exhaust purification system. Further comprising time measuring means for measuring an elapsed time since starting the internal combustion engine,
10. The heating regeneration unit according to claim 5 , wherein when the elapsed time measured by the timing unit is smaller than a predetermined determination value, the regeneration process is performed by the first heating regeneration unit. An exhaust purification device for an internal combustion engine according to claim 1. In an exhaust gas purification apparatus for an internal combustion engine, which is provided in an exhaust passage of the internal combustion engine and includes a particulate filter that collects particulates in the exhaust gas,
Regeneration means for executing regeneration processing for burning the particulates collected by the particulate filter;
Provided separately from the exhaust passage, the fuel is reformed to produce a reducing gas containing hydrogen and carbon monoxide, and the reducing gas is provided upstream of the particulate filter in the exhaust passage. A fuel reformer that is supplied into the exhaust passage from the inlet,
Combustion determination means for determining whether or not the particulates deposited on the particulate filter are in a combustion state ,
The reproducing means includes
Normal regeneration means for performing regeneration processing without using the reducing gas produced by the fuel reformer, and heating regeneration means capable of executing regeneration processing using the reducing gas produced by the fuel reformer And switching whether to perform the regeneration process by the normal regeneration unit or the regeneration process by the heating regeneration unit according to a predetermined condition,
The regeneration means performs regeneration processing by the normal regeneration means when it is determined that the particulate is in the combustion state, and when it is determined that the particulate is not in the combustion state, the heating means An exhaust emission control device for an internal combustion engine, wherein a regeneration process is performed by a regeneration means.

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