JP3986208B2 - Exhaust gas purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for purifying exhaust gas discharged from a diesel engine. More specifically, the present invention relates to an apparatus that reduces the emission of NOx in exhaust gas to the atmosphere.
[0002]
[Prior art]
Conventionally, as this type of exhaust gas purifying apparatus, a NOx reduction catalyst housed in a catalytic converter is provided in an exhaust pipe of a diesel engine, and a reducing agent supply means for supplying a reducing agent to the exhaust upstream side of the NOx reduction catalyst is provided. Furthermore, there is disclosed a diesel engine exhaust gas purification device in which a controller controls the above-mentioned reducing agent supply means in accordance with the operating condition of the engine (Japanese Patent Laid-Open No. 5-302509). In this apparatus, a reducing agent supply means is connected to an exhaust pipe or a catalytic converter via a reducing agent feed nozzle, a reducing agent feed pipe and a reducing agent feed pump, and a reducing agent feed pipe is provided in the reducing agent feed pipe. A reducing agent flow rate adjustment valve capable of adjusting the supply amount to the reducing agent feed nozzle, an air tank connected to the reducing agent feed nozzle via an air feed pipe, and a reducing agent feed nozzle for compressed air provided in the air feed pipe And an air flow rate adjusting valve capable of adjusting the supply amount of the air. Examples of the reducing agent include light oil and engine oil. The controller is specifically configured to control the reducing agent feed pump, the reducing agent flow rate adjusting valve, and the air flow rate adjusting valve in accordance with the engine speed, the engine load, the exhaust gas temperature on the catalyst inlet side, and the oxygen concentration in the exhaust gas. The
[0003]
In the exhaust gas purification apparatus for a diesel engine configured in this way, an optimal amount of reducing agent according to the operating condition of the engine is finely atomized by compressed air and supplied to the exhaust gas. As a result, the utilization rate of the reducing agent can be improved, and NOx contained in the exhaust gas can be efficiently reduced, so that the consumption of the reducing agent can be reduced. Further, since the temperature reduction of the exhaust gas is suppressed and the reaction of the NOx reduction catalyst is sufficiently maintained, the NOx purification rate can be improved, and NOx can be treated with the catalyst even if the exhaust gas contains a large amount of oxygen. It has become.
[0004]
[Problems to be solved by the invention]
However, in the conventional exhaust gas purifying apparatus for diesel engines disclosed in Japanese Patent Laid-Open No. 5-302509, since a large amount of oxygen is present in the exhaust gas of the engine, when light oil is supplied as a reducing agent, the light oil becomes NOx. Instead, it reacts with oxygen in the exhaust gas. For this reason, even if a relatively large amount of reducing agent is supplied to the NOx reduction catalyst, there is a problem that the NOx reduction efficiency at the catalyst, that is, the NOx reduction rate is still low.
[0005]
A first object of the present invention is to provide an exhaust gas purifying apparatus capable of reducing the amount of reducing agent consumed by a NOx reduction catalyst and reducing NOx with high efficiency.
The second object of the present invention is to sufficiently atomize the light oil injected into the cylinder at the time of regeneration of the catalyst, thereby generating an optimum reducing agent for the NOx reduction catalyst in the cylinder, and using this reducing agent as NOx. An object of the present invention is to provide an exhaust gas purification device that can be supplied to a reduction catalyst.
The third object of the present invention is to sufficiently atomize the light oil injected into the exhaust passage at the time of regeneration of the catalyst, so that the air-fuel ratio of the exhaust gas in the exhaust passage can be surely made rich in the reducing agent. An object is to provide an exhaust gas purification device.
A fourth object of the present invention is to provide an exhaust gas purifying apparatus capable of reliably detecting the catalyst regeneration start timing and regeneration completion timing.
A fifth object of the present invention is to provide an exhaust gas purifying device capable of reducing NOx in exhaust gas even when the regeneration prohibition state of the catalyst continues for a predetermined time or more after reaching the regeneration start time of the catalyst. It is in.
[0006]
[Means for Solving the Problems]
  The invention according to claim 115 to 17As shown, the NOx in the exhaust gas that is provided in the exhaust passage 12 of the diesel engine 11 and flows into the exhaust passage 12 is occluded, and HC, CO, CO in the exhaust gas₂Or H₂EGR that adjusts the flow rate of exhaust gas that is provided in an EGR pipe 14 that bypasses the diesel engine 11 and connects the exhaust passage 12 and the intake passage 18 by bypassing the diesel engine 11 and that passes through the EGR pipe 14. A valve 16;A light oil adding means 71 connected to the exhaust passage 12 upstream of the catalyst 13 and capable of injecting light oil 42 toward the catalyst 13;A regeneration start detection sensor 21 that detects the regeneration start timing of the catalyst 13 and an EGR valve 16 based on the detection output of the regeneration start detection sensor 21.And light oil adding means 71An exhaust gas purifying apparatus comprising a controller 22 for controllingThus, the light oil adding means 71 is inserted into the exhaust passage 12 and has an addition injector 71a capable of injecting the light oil 42 toward the catalyst 13, and the pin 71e is idled in the nozzle hole 71d of the nozzle portion 71c of the addition injector 71a. A plurality of spiral grooves 71f are formed on the inner peripheral surface of the injection hole 71d, the addition injector 71a is connected to the common rail 51b or the feed pump 51c of the in-cylinder fuel injection device 51, and the controller 22 inserts the injection injector 71a. By controlling the addition from the injector 71a to the light oil 42 ) Is configured to be injected.
  In the exhaust gas purifying apparatus according to the first aspect, when the engine 11 is operated normally, that is, when the air-fuel ratio of the air-fuel mixture in the engine 11 is in a lean state, the catalyst 13 changes NO in the exhaust gas to NO.₂When the regeneration start detection sensor 21 detects that the NOx occlusion amount by the catalyst 13 has reached a predetermined value, the controller 22 sets the EGR valve 16 to a predetermined value based on the detection output of the sensor 21. Open at an opening of 0, O in exhaust gas₂HC, CO, CO in exhaust gas while reducing concentration₂Or H₂Increase the concentration of. As a result, the reduction reaction in the catalyst 13 is promoted, and NOx occluded in the catalyst 13 is harmless N₂The catalyst 13 is regenerated by converting it into water or the like and discharging it to the atmosphere.Further, when the catalyst 13 is regenerated, the controller 22 opens the EGR valve 16 at a predetermined opening and injects the light oil 42 from the light oil adding means 41. ₂ HC, CO, CO in exhaust gas while reducing concentration ₂ Or H ₂ The concentration of can be increased. Furthermore, since the light oil 42 injected into the exhaust passage 12 during regeneration of the catalyst 13 can be sufficiently atomized, the concentration of HC in the exhaust gas in the exhaust passage 12 can be increased.
[0013]
ContractClaim2The invention according to claim1Further, the catalyst regeneration time is 0.1 to2It is characterized by seconds.
  ThisofClaim2In the exhaust gas purification apparatus described in the above, the regeneration completion time of the catalyst 13 isPredictTherefore, after the predetermined time has elapsed, it can be reliably detected, so that the NOx in the exhaust gas can be efficiently occluded by the catalyst 13 again.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
  Next, the present inventionThe fruitThe form of applicationAlong with the reference formExplain based on the drawingsThe
  <First Reference Form>
  As shown in FIG. 1, an exhaust gas purifying device for purifying exhaust gas discharged from a diesel engine 11 of a truck is provided with a catalyst 13 provided in an exhaust pipe 12, an EGR valve 16 provided in an EGR pipe 14, and an exhaust pipe 12. Based on the exhaust throttle valve 17 provided in the engine, the intake throttle valve 19 provided in the intake pipe 18, the regeneration start detection sensor 21 for detecting the regeneration start timing of the catalyst 13, and the detection output of the regeneration start detection sensor 21. A controller 22 for controlling the EGR valve 16, the exhaust throttle valve 17, and the intake throttle valve 19. The catalyst 13 occludes NOx in the exhaust gas flowing into the exhaust pipe 12, and HC, CO, CO in the exhaust gas.₂Or H₂This is a so-called NOx occlusion reduction type catalyst that regenerates the occluded NOx when the amount of NOx is increased. The catalyst 13 is accommodated in a case 23 provided in the middle of the exhaust pipe 12.
[0020]
Although not shown, the catalyst 13 has a monolithic carrier (material: cordierite) in which a grid-like (honeycomb-like) passage is formed in the exhaust gas flow direction, and is formed on the monolithic carrier and carries a noble metal and a NOx storage agent. And a coat layer. Examples of the noble metal include Pt, and examples of the NOx storage agent include alkali metals such as Li, Na, K, and Cs, alkaline earth metals such as Mg, Ca, and Ba, Y, La, Ce, Pr, Nd, and Eu. , Gd, Dy (other than Y, lanthanoid metal) and the like. The NOx storage agent is supported by 2 to 20% by weight, preferably 5 to 10% by weight, based on the total weight of the catalyst. An example of the coat layer is alumina.
[0021]
The EGR pipe 14 bypasses the engine 11 and connects the exhaust pipe 12 and the intake pipe 18, and the EGR valve 16 adjusts the flow rate of the exhaust gas that passes through the EGR pipe 14 and is recirculated from the exhaust pipe 12 to the intake pipe 18. Configured. Although the EGR valve 16 is not shown, an electric valve that adjusts the opening degree of the EGR valve 16 by driving a valve body by a motor is used, but an air-driven valve or the like may be used. Reference numeral 26 in FIG. 1 is an EGR cooler that cools the exhaust gas (EGR gas) recirculated to the intake pipe 18.
[0022]
The exhaust throttle valve 17 is provided in the exhaust pipe 12 on the exhaust downstream side of the connection portion of the EGR pipe 14 to the exhaust pipe 12 and on the exhaust upstream side of the catalyst 13 so that the flow rate of the exhaust gas flowing through the exhaust pipe 12 can be adjusted. Is done. The intake throttle valve 19 is provided in the intake pipe 18 upstream of the connection portion of the EGR pipe 14 to the intake pipe 18 so that the flow rate of the intake air flowing through the intake pipe 18 can be adjusted. The exhaust throttle valve 17 is configured to increase the amount of exhaust gas recirculated to the intake pipe 18 through the EGR pipe 14 by restricting the exhaust pipe 12 during regeneration of the catalyst 13. Further, the intake throttle valve 19 is configured to reduce the oxygen amount or oxygen concentration of the air-fuel mixture supplied to the cylinder 11a by restricting the intake pipe 18 during regeneration of the catalyst 13.
[0023]
  The reproduction start detection sensor 21referenceIn this embodiment, the accelerator sensor 21a detects the amount of depression of the accelerator pedal, and the rotation sensor 21b detects the rotational speed of the engine 11. The exhaust pipe 12 on the exhaust downstream side of the catalyst 13 has an outlet side O for detecting the oxygen concentration contained in the exhaust gas that has passed through the catalyst 13.₂A sensor 31b is provided, and the exhaust pipe 12 upstream of the catalyst 13 has an inlet side O for detecting the oxygen concentration contained in the exhaust gas before passing through the catalyst 13.₂A sensor 31a is provided. Entrance side O₂Sensor and outlet side O₂A regeneration completion detection sensor 31 is configured by the sensors. Since oxygen on the catalyst 13 is used as the catalyst 13 is regenerated, the oxygen concentration in the exhaust gas that has passed through the catalyst 13 gradually decreases, and when the oxygen concentration reaches about 1%, regeneration of the catalyst 13 is almost completed. Can be estimated.
[0024]
  A catalyst temperature sensor 32 that detects the temperature of the catalyst 13 is inserted into the case 23. The catalyst temperature sensor 32 includes an inlet side temperature sensor 32a inserted into the case 23 upstream of the catalyst 13 and an outlet side temperature sensor 32b inserted into the case 23 downstream of the catalyst 13. The catalyst temperature is estimated from the average value of the detection outputs 32a and 32b. The reason for estimating the catalyst temperature is to regenerate the catalyst 13 within a temperature range (200 to 450 ° C.) in which the catalyst 13 can be efficiently regenerated, that is, a temperature at which the catalyst can be regenerated. The driving state detection sensor 33 for detecting the driving state of the truckreferenceIn this embodiment, the accelerator sensor 21a is used to detect whether the truck is in an accelerating state, a steady running state, or a decelerating state based on the rate of change of the accelerator sensor 21a with respect to time. Further, reference numeral 34 in FIG. 1 denotes an exhaust gas temperature sensor for detecting the temperature of the exhaust gas immediately after being discharged from the engine 11.
[0025]
As shown in FIG. 2, the accelerator sensor 21a, the rotation sensor 21b, the inlet side O₂Sensor 31a, outlet side O₂The detection outputs of the sensor 31b, the inlet side temperature sensor 32a, the outlet side temperature sensor 32b, the running state detection sensor 33, and the exhaust gas temperature sensor 34 are connected to the control input of the CPU 22a of the controller 22 via the I / O port 22b. Are connected to the EGR valve 16, the exhaust throttle valve 17, and the intake throttle valve 19 through the I / O port 22c. Further, a memory 37 is connected to the CPU 22a, and as shown in FIG. 4, the opening of the EGR valve 16 and the exhaust throttle valve 17 when the NOx is occluded by the catalyst, when the catalyst is regenerated, and when the catalyst regeneration prohibition is canceled are shown. Are stored and control maps A, B and C (maps indicating the optimum opening degree of the EGR valve 16 and the like when the engine speed and the engine load change) are stored. Further, as shown in FIG. 3, the memory 37 stores a NOx emission map indicating NOx emission from the engine 11 that changes with changes in the engine speed and the accelerator pedal depression amount (accelerator opening). The In addition, the code | symbol 38 of FIG. 1 is a muffler.
[0026]
The operation of the exhaust gas purification apparatus configured as described above will be described with reference to the flowchart of FIG.
First, the controller 22 takes in the rotational speed of the engine 11 and the amount of depression of the accelerator pedal (accelerator opening) based on the detection outputs of the rotation sensor 21b and the accelerator sensor 21a. Next, the controller 22 calculates the NOx emission amount of the engine 11 by applying the engine rotation speed and the accelerator opening to the NOx emission amount map (FIG. 3), and thereby accumulates the NOx occlusion amount occluded in the catalyst 13. Next, the controller 22 calculates a change rate Y of the accelerator opening (a change amount of the accelerator opening per unit time). For example, the accelerator opening exceeds a predetermined value (for example, 70% or more), and the change rate Y is predetermined. Rate of change Y₀(For example, when the accelerator opening changes in the direction of increasing by 5% or more per second), it is determined that the truck is in an acceleration state, and the accelerator opening and its change rate Y are When it is out of the above range, it is determined that the truck is in a steady running or decelerating state.
[0027]
The truck is in a steady running or decelerating state, and the NOx occlusion amount X of the catalyst 13 is a predetermined amount X₀If it is (for example, 70%) or less, the controller 22 takes in the control map A at the time of NOx occlusion by the catalyst of FIG. 4 and controls the EGR valve 16 and the like according to this control map A. That is, the controller 22 fully closes the EGR valve 16 and fully opens the exhaust throttle valve 17 and the intake throttle valve 19. As a result, control during normal operation is performed, and accumulation of the NOx occlusion amount is continued. During this normal operation (NOx occlusion), the air-fuel ratio of the air-fuel mixture in the cylinder 11a is high and lean, that is, the excess air ratio (actual supply air amount / theoretical air amount necessary for light oil combustion). Is 2 or more. If, for example, Ba is used as the NOx occluding agent supported on the coating layer of the catalyst 13, NOx discharged from the engine 11 is converted into O in the exhaust gas at the catalyst 13.₂And BaO, BaCO in the catalyst 13_ThreeReacts with [Ba (NO_Three)₂] Is generated and stored in this state in the catalyst 13. For this reason, after the exhaust gas on the catalyst inlet side having a high NOx concentration passes through the catalyst, the NOx concentration becomes extremely low and is discharged to the catalyst outlet side, and NOx emission into the atmosphere can be reduced.
[0028]
On the other hand, the NOx occlusion amount X of the catalyst 13 is a predetermined amount X.₀If it exceeds (for example, 70%), the controller 22 determines that the catalyst 13 has reached the regeneration timing, and each detection output T of the inlet side temperature sensor 32a and the outlet side temperature sensor 32b of the catalyst temperature sensor 32 is detected.₁, T₂Then, the average value of the detection outputs of these temperature sensors 32a and 32b ((T₁+ T₂) / 2) is estimated as the catalyst temperature Tc. This catalyst temperature Tc is the catalyst regeneration lower limit temperature T.₀When the temperature exceeds (for example, 200 ° C.), the controller 22 takes in the control map B at the time of catalyst regeneration shown in FIG. That is, the controller 22 opens the EGR valve 16 with a predetermined opening degree, and closes the exhaust throttle valve 17 and the intake throttle valve 19 with a predetermined closing degree. As a result, the oxygen concentration in the exhaust gas decreases and HC, CO, CO₂Or H₂As the reducing agent increases, first, [Ba (NO_Three)₂] Reacts with the reducing agent in the exhaust gas to react with N₂The catalyst 13 functions as a highly selective reduction catalyst, and the NO₂Reacts with CO and HC in exhaust gas, harmless N₂, CO₂, H₂O is produced and discharged to the atmosphere. As a result, almost all of CO and HC can be effectively utilized for catalyst regeneration without being affected by oxygen in the exhaust gas, so that the catalyst 13 can be efficiently regenerated.
[0029]
The controller 22 controls the inlet side O during regeneration of the catalyst 13.₂Sensor 31a and outlet side O₂Based on each detection output of the sensor 31b, the oxygen concentration in the exhaust gas before passing through the catalyst 13 and after passing through the catalyst 13 is expressed as S.₁, S₂Each uptake, oxygen concentration S₁, S₂Difference is not less than a predetermined value and the oxygen concentration S₂Is the predetermined concentration S₀When it becomes less than (for example, 1%), it is determined that regeneration of the catalyst 13 is completed. After the catalyst regeneration is completed, the controller 22 initializes the integrated value of the NOx occlusion amount, and then takes in the control map A when the NOx occlusion is performed by the catalyst shown in FIG. Control.
[0030]
The track is in an acceleration state, that is, the accelerator opening is equal to or greater than a predetermined value, and the change rate Y is a predetermined change rate Y.₀The controller 22 determines that the temperature exceeds the catalyst regeneration temperature, and the catalyst temperature Tc is lower than the catalyst regeneration lower limit temperature T.₀If higher, the controller 22 takes in the control map B during catalyst regeneration shown in FIG. 4 and controls the EGR valve 16 and the like based on the control map B. Since a large amount of light oil is injected into the cylinder 11a during the acceleration of the truck, the oxygen concentration in the exhaust gas decreases and HC, CO, CO₂, H₂Thus, the catalyst 13 can be efficiently regenerated. The controller 22 calculates the accelerator opening and its rate of change Y during regeneration of the catalyst 13, and the rate of change Y of the accelerator opening is a predetermined rate of change Y.₀After the regeneration of the catalyst 13 is stopped at the following time, the control map A at the time of NOx occlusion by the catalyst of FIG. 4 is taken, and the opening degree of the EGR valve 16 and the like are controlled based on this control map A.
[0031]
Further, the NOx occlusion amount X of the catalyst 13 is a predetermined amount X.₀Even if it is determined that the controller 22 has reached the catalyst regeneration timing (for example, 70%), the catalyst temperature Tc is equal to the catalyst regeneration lower limit temperature T.₀When the temperature is equal to or lower than (eg, 200 ° C.), the controller 22 prohibits the regeneration of the catalyst 13 and the regeneration prohibiting time H₀Is accumulated. For example, if the regeneration prohibition time is 5 minutes or less, the estimation of the catalyst temperature Tc is repeated, and if it exceeds 5 minutes, it is determined that the catalyst 13 cannot effectively store NOx in the exhaust gas. The control map C is taken in, and the EGR valve 16 is controlled according to the control map C. That is, since the controller 22 opens the EGR valve 16 at a predetermined opening, the catalyst 13 can be regenerated. The completion of regeneration of the catalyst 13 is similar to the above in the inlet side O.₂Sensor 31a and outlet side O₂A determination is made based on each detection output of the sensor 31b, that is, the oxygen concentration S before and after the catalyst 13.₁, S₂Difference is not less than a predetermined value and the oxygen concentration S₂Is the predetermined concentration S₀When it becomes less than (for example, 1%), it is determined that regeneration of the catalyst 13 is completed. After the catalyst regeneration is completed, the controller 22 initializes the integrated value of the NOx occlusion amount, and then takes in the control map A when the NOx occlusion is performed by the catalyst shown in FIG. Control.
[0032]
Further, since the combustion of light oil in the engine 11 becomes inactive when the catalyst 13 is regenerated, the NOx concentration on the catalyst inlet side decreases, and the catalyst 13 functions as a reduction catalyst, so the NOx concentration on the catalyst outlet side is Decreases rapidly. Thus, the NOx in the exhaust gas can be efficiently stored in the catalyst 13 and the NOx stored in the catalyst 13 is harmless N₂It is possible to efficiently regenerate the catalyst 13 in a short time by converting it to water or the like.
[0033]
  <Second Reference Form>
  6 to 8Is the first2referenceThe form of is shown. 6, the same reference numerals as those in FIG. 1 denote the same parts.The
  thisreferenceIn this embodiment, the light oil adding means 41 is connected to the exhaust pipe 12 upstream of the catalyst 13, and the controller 22 detects the EGR valve 16, the exhaust throttle valve 17, and the intake throttle valve 19 based on the detection output of the regeneration start detection sensor 21. And it is comprised so that the light oil addition means 41 may be controlled. The light oil addition means 41 includes an addition injection nozzle 41a that is inserted into the exhaust pipe 12 and can inject the light oil 42 toward the catalyst 13, and an addition injection pump 41b that pumps the light oil 42 to the addition injection nozzle 41a. The addition injection nozzle 41a is connected to the discharge port of the addition injection pump 41b via the addition discharge pipe 41c, and the suction port of the addition injection pump 41b is connected to the fuel tank 43 via the addition suction pipe 41d. Is done. Light oil 42 is stored in the fuel tank 43.
[0034]
  The control input of the controller 22 includes an accelerator sensor 21a, a rotation sensor 21b, an inlet side O₂Sensor 31a, outlet side O₂The detection outputs of the sensor 31b, the inlet side temperature sensor 32a, the outlet side temperature sensor 32b, the running state detection sensor 33, and the exhaust gas temperature sensor 34 are respectively connected, and the control output of the controller 22 is the EGR valve 16, the exhaust throttle valve 17, the intake air The throttle valve 19 and the addition injection pump 41b are connected to each other. As shown in FIG. 7, the memory 37 stores the opening degree of the EGR valve 16, the degree of closing of the exhaust throttle valve 17, and the intake throttle valve 19 when the NOx is occluded by the catalyst, when the catalyst is regenerated, and when the catalyst regeneration prohibition is canceled. The control maps A, B, and C of the degree of closing and the amount of light oil added to the exhaust pipe 12 (maps indicating the optimum opening degree of the EGR valve 16 when the engine speed and the engine load change) are stored. 1st other than the abovereferenceThe configuration is the same as that.
[0035]
  The operation of the exhaust gas purification apparatus configured as described above will be described with reference to the flowchart of FIG.
  NOx occlusion amount X by the catalyst 13 is a predetermined amount X₀The controller 22 determines that the catalyst 13 has reached the regeneration time, and the catalyst temperature Tc is the catalyst regeneration lower limit temperature T.₀If the catalyst can be regenerated beyond this, the controller 22 takes in the control map B at the time of catalyst regeneration shown in FIG. 7 and controls the EGR valve 16 and the like based on the control map B. That is, the controller 22 opens the EGR valve 16 at a predetermined opening, closes the exhaust throttle valve 17 and the intake throttle valve 19 respectively, and further operates the addition injection pump 41b of the light oil addition means 41 to operate the exhaust pipe. 12 is added with light oil 42. As a result, the oxygen concentration in the exhaust gas decreases and HC, CO, CO in the exhaust gas.₂Or H₂Is the firstreferenceIt increases further as a reducing agent than the form of. As a result, first [Ba (NO_Three)₂] Reacts with the reducing agent in the exhaust gas to react with N₂The catalyst 13 functions as a highly selective reduction catalyst, and the NO₂Reacts with CO and HC in exhaust gas, harmless N₂, CO₂, H₂Since O is generated and discharged to the atmosphere, almost all CO and HC can be effectively utilized for catalyst regeneration without being affected by oxygen in the exhaust gas. Operation other than the above is the firstreferenceSince it is substantially the same as the embodiment of FIG.
[0036]
  <Third Reference Form>
  9 to 11Is the firstThreereferenceThe form of is shown. 9, the same reference numerals as those in FIG. 1 denote the same parts.The
  thisreferenceIn this embodiment, an in-cylinder fuel injection device 51 that can change either or both of the injection timing and the injection amount of the light oil 42 injected into the cylinder 11a is used. The in-cylinder fuel injection device 51 has an in-cylinder injector 51a whose front end faces the cylinder 11a and can inject the light oil 42 into the cylinder 11a, a common rail 51b that accumulates the light oil 42 inside and pressure-feeds the light oil to the injector 51a, and the common rail A feed pump 51c for supplying light oil 42 to 51b.
[0037]
The in-cylinder injector 51a is configured such that the injection amount and injection timing of the light oil 42 can be adjusted by a solenoid valve (not shown) built in the injector 51a. The in-cylinder injector 51a is connected to the common rail 51b through the pressure feed pipe 51d, the common rail 51b is connected to the discharge port of the feed pump 51c through the in-cylinder discharge pipe 51e, and the suction port of the feed pump 51c is connected to the inside of the cylinder. The fuel tank 43 is connected in communication via the suction pipe 51f. When the catalyst 13 is regenerated, the in-cylinder fuel injection device 51 advances the main injection timing and performs post-injection after the main injection, so that both the injection timing and the injection amount of the light oil 42 into the cylinder 11a can be achieved. Configured to be changed. Reference numeral 52 in FIG. 9 is a pressure sensor for detecting the pressure (fuel pressure) of the light oil 42 in the common rail 51b.
[0038]
  The control input of the controller 22 includes an accelerator sensor 21a, a rotation sensor 21b, an inlet side O₂Sensor 31a, outlet side O₂Sensor 31b, inlet side temperature sensor 32a, outlet side temperature sensor 32b, running state detection sensor 33, exhaust gas temperature sensor 34, and pressure sensor 52 are connected to each other. Control outputs of controller 22 are EGR valve 16, exhaust throttle valve. 17, intake throttle valve 19, in-cylinder injector 51a, and feed pump 51c are connected to each other. In addition, as shown in FIG. 10, the memory 37 stores the opening degree of the EGR valve 16, the exhaust throttle valve closing degree, the intake throttle valve closing degree at the time of NOx occlusion by the catalyst, at the time of catalyst regeneration, and at the time of releasing the catalyst regeneration prohibition. Control map A, B, C of main injection timing, pilot injection presence / absence / post injection injection timing / timing (map showing optimum EGR valve 16 opening degree when engine speed and engine load change) ) Is stored. 1st other than the abovereferenceThe configuration is the same as that.
[0039]
The operation of the thus configured exhaust gas purification apparatus will be described based on the flowchart of FIG.
The truck is in a steady running or decelerating state, and the NOx occlusion amount X of the catalyst 13 is a predetermined amount X₀If it is (for example, 70%) or less, the controller 22 takes in the control map A at the time of NOx occlusion by the catalyst of FIG. 10 and controls the EGR valve 16 and the like according to this control map A. That is, the controller 22 fully closes the EGR valve 16, fully opens the exhaust throttle valve 17 and the intake throttle valve 19, performs main injection at a timing with the highest combustion efficiency, and further performs pilot injection. At this time, post injection is not performed. As a result, control during normal operation is performed, and NOx in the exhaust gas is occluded by the catalyst 13, so that NOx emission into the atmosphere can be reduced.
[0040]
  The truck is in a steady running or decelerating state, and the NOx occlusion amount X of the catalyst 13 is a predetermined amount X₀(For example, 70%) and the catalyst temperature Tc is lower than the catalyst regeneration lower limit temperature T₀When the temperature exceeds (for example, 200 ° C.), the control map B at the time of NOx occlusion by the catalyst of FIG. 10 is taken, and the EGR valve 16 and the like are controlled according to this control map B. That is, the controller 22 opens the EGR valve 16 with a predetermined opening, closes the exhaust throttle valve 17 and the intake throttle valve 19 with a predetermined close degree, and advances the main injection by a predetermined angle from the normal travel time. Further, the pilot injection is not performed, and the post injection is performed in a plurality of times after the top dead center of the piston 11b. As a result, the oxygen concentration in the exhaust gas decreases and HC, CO, CO in the exhaust gas.₂Or H₂Is the firstreferenceIt increases further as a reducing agent than the form of. As a result, almost all CO and HC can be effectively utilized for catalyst regeneration without being affected by oxygen in the exhaust gas.
[0041]
The track is in an accelerated state, and the catalyst temperature Tc is the catalyst regeneration lower limit temperature T.₀If higher, the controller 22 takes in the control map B during catalyst regeneration shown in FIG. 10 and controls the EGR valve 16 and the like based on the control map B. Since a large amount of light oil 42 is injected into the cylinder 11a during the acceleration of the truck, the oxygen concentration in the exhaust gas decreases and HC, CO, CO₂, H₂Thus, the catalyst 13 can be efficiently regenerated.
[0042]
  Further, the NOx occlusion amount X of the catalyst 13 is a predetermined amount X.₀Even if the controller 22 determines that the regeneration time of the catalyst 13 has been reached (for example, 70%), the catalyst temperature Tc is equal to the catalyst regeneration lower limit temperature T.₀When the temperature is equal to or lower than (eg, 200 ° C.), the controller 22 prohibits the regeneration of the catalyst 13 and the regeneration prohibiting time H₀Is accumulated. For example, if the regeneration prohibition time is 5 minutes or less, the estimation of the catalyst temperature Tc is repeated, and if it exceeds 5 minutes, it is determined that the catalyst 13 cannot effectively store NOx in the exhaust gas. The control map C is taken in, and the EGR valve 16 is controlled according to the control map C. That is, the controller 22 opens the EGR valve 16 at a predetermined opening, and advances the main injection by a predetermined angle from the normal travel time. At this time, pilot injection and post injection are not performed. As a result, the catalyst 13 can be regenerated. Operation other than the above is the firstreferenceSince it is substantially the same as the embodiment of FIG.
[0043]
  <Fourth Reference Form>
  12 to 14Is the firstFourreferenceThe form of is shown. 12, the same reference numerals as those in FIGS. 6 and 9 denote the same parts.The
  thisreferenceThe exhaust gas purification apparatus of the form of the secondreferenceIn the exhaust gas purification device of the formreferenceThis is a device incorporating the in-cylinder fuel injection device 19 of the form. That is, thisreferenceThe exhaust gas purifying apparatus of the form includes a catalyst 13, an EGR valve 16, an exhaust throttle valve 17, an intake throttle valve 19, a light oil addition means 41, and an in-cylinder fuel injection device 51, and the controller 22 detects regeneration start. Based on the detection output of the sensor 21, the EGR valve 16, the exhaust throttle valve 17, the intake throttle valve 19, the light oil adding means 41 and the in-cylinder fuel injection device 51 are controlled.
[0044]
  Accelerator sensor 21a, rotation sensor 21b, inlet side O₂Sensor 31a, outlet side O₂The detection outputs of the sensor 31b, the inlet side temperature sensor 32a, the outlet side temperature sensor 32b, the running state detection sensor 33, the exhaust gas temperature sensor 34, and the pressure sensor 36 are connected to the control input of the controller 22, and the control output of the controller 22 is EGR. Connected to the valve 16, the exhaust throttle valve 17, the intake throttle valve 19, the addition injection pump 41b, the in-cylinder injector 51a, and the feed pump 51c, respectively. As shown in FIG. 13, the memory 37 stores the opening degree of the EGR valve 16, the degree of closing of the exhaust throttle valve 17, and the closing of the intake throttle valve 19 when NOx is occluded by the catalyst, during catalyst regeneration, and when the catalyst regeneration prohibition is canceled. , Main injection timing, pilot injection presence / absence, post-injection presence / absence / timing and light oil addition amount to exhaust pipe 12 A, B, C (optimal when engine speed and engine load change) A map indicating the opening degree of the EGR valve 16 is stored. Other than the above, the second and thirdreferenceThe configuration is the same as that.
[0045]
The operation of the exhaust gas purification apparatus configured as described above will be described based on the flowchart of FIG.
The truck is in a steady running or decelerating state, and the NOx occlusion amount X of the catalyst 13 is a predetermined amount X₀If it is (for example, 70%) or less, the controller 22 takes in the control map A at the time of NOx occlusion by the catalyst of FIG. 13 and controls the EGR valve 16 and the like according to this control map A. That is, the controller 22 fully closes the EGR valve 16, fully opens the exhaust throttle valve 17 and the intake throttle valve 18, performs main injection at the time when the combustion efficiency is highest, and further performs pilot injection. At this time, post injection and addition of light oil to the exhaust pipe 12 are not performed. As a result, control during normal operation is performed, and NOx in the exhaust gas is occluded by the catalyst 13, so that NOx emission into the atmosphere can be reduced.
[0046]
  The truck is in a steady running or decelerating state, and the NOx occlusion amount X of the catalyst 13 is a predetermined amount X₀(For example, 70%) and the catalyst temperature Tc is lower than the catalyst regeneration lower limit temperature T₀When the temperature exceeds (for example, 200 ° C.), the control map B at the time of NOx occlusion by the catalyst of FIG. 13 is taken, and the EGR valve 16 and the like are controlled according to this control map B. That is, the controller 22 opens the EGR valve 16 at a predetermined opening, closes the exhaust throttle valve 17 and the intake throttle valve 19 at a predetermined close degree, advances the main injection by a predetermined angle from the normal travel time, and further adds The injection pump 41b is operated to add light oil 42 to the exhaust pipe 12. Further, the pilot injection is not performed, and the post injection is performed in a plurality of times after the top dead center of the piston 11b. As a result, the oxygen concentration in the exhaust gas decreases and HC, CO, CO in the exhaust gas.₂Or H₂Is the firstreferenceIt increases further as a reducing agent than the form of. As a result, almost all CO and HC can be effectively utilized for catalyst regeneration without being affected by oxygen in the exhaust gas. Operations other than the above are the second and thirdreferenceSince it is substantially the same as the embodiment of FIG.
[0049]
  <Embodiment>
  FIG.~FIG.Is the present inventionThe fruitAn embodiment is shown.FIG.In FIG. 12, the same reference numerals as those in FIG.The
  In this embodiment, the light oil addition means 71 has an addition injector 71a capable of injecting light oil 42 toward the catalyst 13, and this addition injector 71a is connected to the common rail of the in-cylinder fuel injection device 51 via the communication pipe 71b. It is connected to 51b, and the controller 22 controls the injector 71a for addition, and it is comprised so that the light oil 42 may be injected from the injector 71a for addition (FIG.). The injector 71a for addition is configured such that the injection amount and the injection timing of the light oil 42 can be adjusted by a solenoid valve (not shown) built in the injector 71a. The addition injector 71a has a throttle-type nozzle portion 71c, and this nozzle portion 71c is inserted into the exhaust pipe 12 upstream of the catalyst 13 (see FIG.FIG.). A pin 71e is loosely inserted into the nozzle hole 71d of the nozzle portion 71c, and a plurality of spiral grooves 71f are formed on the inner peripheral surface of the nozzle hole 71d (see FIG.FIG.as well asFIG.). Since the injector 71a for addition is connected to the common rail 51b as described above, the first injector 71areferenceThe addition injection pump of the form is not required. Further, catalyst regeneration is performed for a preset time from the start of catalyst regeneration. For this reason, the inlet side O₂Sensor and outlet side O₂A sensor is unnecessary. The catalyst regeneration time should be as short as possible., 0. Set to 1-2 seconds. The catalyst regeneration time is limited to 0.1 to 180 seconds. If less than 0.1 seconds, the regeneration of the catalyst is not completed,2This is because if it exceeds 2 seconds, the amount of black smoke emitted increases. 4th except the abovereferenceThe configuration is the same as that.
[0050]
  In the exhaust gas purification apparatus configured as described above, the light oil 42 injected from the addition injector 71a during the regeneration of the catalyst 13 advances spirally along the inner surface of the exhaust pipe 12, so that it is instantly atomized and the exhaust gas is emptied. The fuel ratio can be quickly made rich, and HC, CO, H₂Can be increased. As a result, the catalyst 13 functions as a reduction catalyst, and the catalyst 13 can be efficiently regenerated. Further, the controller 22 measures the catalyst regeneration time simultaneously with the start of regeneration of the catalyst 13, and determines that the catalyst regeneration has been completed after a lapse of a predetermined time (for example, 2 seconds), so the integrated value of the NOx occlusion amount is calculated after the lapse of the predetermined time. Initialization is performed, a map at the time of NOx occlusion by the catalyst is taken in, and the opening degree of the EGR valve 16 and the like are controlled based on this map. The operation other than the above is the fourthreferenceSince it is substantially the same as the embodiment of FIG.
[0052]
  The aboveRealIn the present embodiment, when the catalyst is regenerated, the in-cylinder fuel injection device advances the main injection timing and performs post-injection after the main injection, thereby reducing both the injection timing and the injection amount of light oil into the cylinder. Although changed, either or both of the injection timing and the injection amount of the light oil into the cylinder may be changed by performing either one of the advance timing of the main injection timing or the post injection.
  Also onRealIn the present embodiment, the diesel engine of the present invention is mounted on a truck. However, it may be mounted on a bus, a passenger car or other vehicle, a ship, a construction machine, or the like.
  Also onRealIn the present embodiment, when the catalyst regeneration prohibition state continues for a predetermined time or longer, the controller cancels the catalyst regeneration prohibition, and opens the EGR valve and advances the timing of main injection by the in-cylinder fuel injection device. Although it is configured to perform both, it may be configured to perform either one of the opening of the EGR valve and the advance of the timing of the main injection by the in-cylinder fuel injection device.
[0053]
  Also onRealIn the embodiment, the accelerator sensor is described as the traveling state detection sensor that detects the traveling state of the truck. However, a vehicle speed sensor that detects the vehicle speed of the truck may be used in addition to the accelerator sensor.
  Also onRealIn the embodiment, the injector for addition is connected to the common rail of the in-cylinder fuel injection device, but may be connected to the discharge port of the feed pump of the in-cylinder fuel injection device.
  Furthermore, aboveRealIn the present embodiment, the catalyst temperature is estimated based on the respective detection outputs (catalyst inlet temperature and catalyst outlet temperature) of the inlet side temperature sensor and the outlet side temperature sensor, but the catalyst temperature is determined by the inlet side temperature sensor or the outlet side temperature sensor. You may estimate based on any one detection output (one of catalyst inlet temperature or catalyst outlet temperature).
[0060]
【The invention's effect】
  As described above, according to the present invention, the catalyst provided in the exhaust passage occludes NOx in the exhaust gas and releases the occluded NOx when the oxygen concentration in the exhaust gas decreases, bypassing the diesel engine. Since the EGR valve is provided in the EGR pipe to be operated, and the controller controls the EGR valve based on the detection output of the regeneration start detection sensor for detecting the regeneration start timing of the catalyst. When the air-fuel ratio of the air-fuel mixture is lean, the catalyst converts NO in the exhaust gas to NO₂When the NOx occlusion amount by the catalyst reaches a predetermined value, the controller opens the EGR valve.₂HC, CO, CO in exhaust gas while reducing concentration₂Or H₂The concentration of can be increased. As a result, the reduction reaction in the catalyst is promoted, and NOx occluded in the catalyst is removed from harmless N₂The catalyst can be regenerated by converting it to waterThe
[0061]
  Further, a light oil addition means capable of injecting light oil toward the catalyst is connected to the exhaust passage upstream of the catalyst, and the controller controls the EGR valve and the light oil addition means based on the detection output of the regeneration start detection sensor.RuWith this configuration, the OGR in the exhaust gas is further increased than when only the EGR valve is controlled during regeneration of the catalyst, or when the EGR valve and the exhaust throttle valve or the intake throttle valve are controlled.₂While reducing the concentration, HC, CO, CO₂Or H₂The concentration of can be increased. As a result, the catalyst can be regenerated more efficiently.The
[0063]
  MaLightIf the injector for addition of the oil addition means is connected to the common rail or feed pump of the in-cylinder fuel injection device, and the controller controls the injector for addition to inject light oil from the injector for injection, the catalyst can be regenerated. Since the light oil injected into the exhaust passage can be sufficiently atomized, the concentration of HC in the exhaust gas in the exhaust passage can be increased.
  MaTouchThe regeneration time of the medium is 0.1 to2If it is set to second, the regeneration completion timing of the catalyst can be reliably detected, so that the NOx in the exhaust gas can be efficiently occluded again by the catalyst.
[Brief description of the drawings]
[Figure 1]First1referenceThe block diagram which shows the exhaust gas purification apparatus of a form.
FIG. 2 is a block diagram showing control of the exhaust gas purification device.
FIG. 3 is a NOx emission map showing NOx emission from the engine which changes with changes in engine speed and accelerator opening.
FIG. 4 is a control map showing the opening degree of the EGR valve and the like when NOx is occluded by the catalyst, when the catalyst is regenerated, and when the catalyst regeneration prohibition is canceled.
FIG. 5 is a flowchart showing the operation of the exhaust gas purifying apparatus.
[Fig. 6]First2referenceThe block diagram corresponding to FIG. 1 which shows a form.
FIG. 7 is a control map showing the opening degree of the EGR valve and the like when NOx is occluded by the catalyst, when the catalyst is regenerated, and when the catalyst regeneration prohibition is canceled.
FIG. 8 is a flowchart showing the operation of the exhaust gas purifying apparatus.
FIG. 9First3referenceThe block diagram corresponding to FIG. 1 which shows a form.
FIG. 10 is a control map showing the opening degree of the EGR valve and the like when NOx is occluded by the catalyst, when the catalyst is regenerated, and when the catalyst regeneration prohibition is canceled.
FIG. 11 is a flowchart showing the operation of the exhaust gas purifying apparatus.
FIG.First4referenceThe block diagram corresponding to FIG. 1 which shows a form.
FIG. 13 is a control map showing the opening degree of the EGR valve and the like when NOx is occluded by the catalyst, when the catalyst is regenerated, and when the catalyst regeneration prohibition is canceled.
FIG. 14 is a flowchart showing the operation of the exhaust gas purifying apparatus.
[FIG.The present inventionThe fruitThe block diagram corresponding to FIG. 1 which shows embodiment.
[FIG.]FIG.FIG.
[FIG.An enlarged perspective view of the main part including the injection hole of the injector for adding the light oilFigure.
[Explanation of symbols]
  11 Diesel engine
12 Exhaust pipe (exhaust passage)
  13 Catalyst
  14 EGR pipe
  16 EGR valve
18 Intake pipe (intake passage)
21  Playback start detection sensor
22 Controller
71  Light oil addition means
42 Light oil
  51 In-cylinder fuel injection device
  51a In-cylinder injector
  51b Common rail
  51c feed pump
71a Additive injector

Claims (2)

It is provided in the exhaust passage (12) of the diesel engine (11), stores NOx in the exhaust gas flowing into the exhaust passage (12), and is regenerated when HC, CO, CO ₂ or H ₂ in the exhaust gas increases. A catalyst (13) to be treated;
An EGR valve that adjusts the flow rate of exhaust gas that is provided in an EGR pipe (14) that bypasses the diesel engine (11) and connects the exhaust passage (12) and the intake passage (18) and that passes through the EGR pipe (14). (16)
The catalyst jettable light oil addition means from being connected to the exhaust upstream side of the exhaust passage (12) toward said catalyst (13) gas oil (42) (13) (71),
A regeneration start detection sensor ( 21 ) for detecting the regeneration start time of the catalyst (13);
An exhaust gas purification apparatus comprising a controller (22) for controlling the EGR valve (16) and the light oil addition means (71) based on a detection output of the regeneration start detection sensor ( 21 ) ,
The light oil addition means (71) has an addition injector (71a) inserted into the exhaust passage (12) and capable of injecting light oil (42) toward the catalyst (13) ,
A pin (71e) is loosely inserted into the nozzle hole (71d) of the nozzle portion (71c) of the injector for addition (71a) ,
A plurality of spiral grooves (71f) are formed on the inner peripheral surface of the nozzle hole (71d) ,
The addition injector (71a) is connected to the common rail (51b) or feed pump (51c) of the in- cylinder fuel injection device (51) ,
The controller (22) is configured so that the light oil (42) is injected from the addition injector (71a) by controlling the addition injector (71a) .
An exhaust gas purification apparatus characterized by that . Claim 1 Symbol placement of the exhaust gas purifying apparatus playing time of the catalyst is from 0.1 to 2 seconds.

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