JP2007262992A - Exhaust emission control device for compression ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently perform temperature rise or reduction of an exhaust emission control catalyst by post injection in relation to an exhaust emission control device for a compression ignition type internal combustion engine. <P>SOLUTION: When necessity of temperature rise process and/or reduction process of the exhaust emission control catalyst is judged and it is judged that the temperature rise process or the reduction process is necessary, post injection is performed by a fuel injection valve capable of directly injecting fuel into a cylinder. At that time, open close timing and/or operating angle of at least one of an intake valve and an exhaust valve is changed by a variable valve gear to positively control cylinder inside temperature during post injection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for a compression ignition type internal combustion engine, and more particularly to an exhaust gas purification apparatus for a compression ignition type internal combustion engine that performs post-injection as means for raising or reducing the temperature of an exhaust gas purification catalyst.

  A compression ignition type internal combustion engine is provided with an exhaust purification catalyst for purifying harmful components such as NOx in the exhaust gas. In an exhaust purification catalyst having a structure for trapping NOx inside, the purification capability can be maintained by reducing the trapped NOx from time to time and desorbing it from the exhaust purification catalyst. As a reduction processing method, for example, as described in Patent Document 1, it is known to enrich the air-fuel ratio of exhaust gas by post injection. In this prior art, NOx trapped in the exhaust purification catalyst is reduced by supplying fuel (unburned HC) as a reducing agent to the exhaust purification catalyst.

Further, the purification ability of the exhaust purification catalyst greatly depends on the catalyst temperature. In order to maintain the purification capacity, it is necessary to maintain the catalyst temperature at a certain temperature or higher, and when the catalyst temperature decreases, it is required to quickly raise the temperature to the activation temperature. As a method for raising the catalyst temperature, it is known to perform post injection as described in Patent Document 2, for example. In this prior art, the exhaust gas temperature is raised by the combustion of post-injected fuel, and the catalyst temperature is raised by supplying high-temperature exhaust gas to the exhaust purification catalyst.
JP 2002-371889 A JP 2003-120368 A JP 2001-263109 A

  By the way, whether the post-injected fuel is burned or discharged without being burned depends on the in-cylinder temperature at the time of post-injection. However, each of the above prior arts does not disclose positively controlling the in-cylinder temperature.

  If the in-cylinder temperature at the time of post-injection can be positively controlled, the temperature or reduction of the exhaust purification catalyst can be performed more efficiently. For example, if the fuel can be reformed (lightened) by thermal decomposition by controlling the in-cylinder temperature, the oxidation reaction of the fuel on the exhaust purification catalyst can be promoted, and NOx can be reduced more efficiently. Can do. Further, by reforming the fuel as described above and supplying it to the exhaust purification catalyst instead of completely burning the fuel, the catalyst temperature can be raised by the reaction heat due to the oxidation reaction. When fuel is burned and high-temperature exhaust gas is supplied, the heat efficiency is reduced due to heat radiation from the exhaust pipe. However, if the reformed fuel is subjected to an oxidation reaction on the exhaust purification catalyst, a decrease in thermal efficiency due to heat dissipation is small, and the catalyst temperature can be raised more efficiently.

  The present invention has been made to solve the above-described problems, and provides an exhaust purification device for a compression ignition type internal combustion engine that can efficiently raise or reduce the temperature of an exhaust purification catalyst by post injection. The purpose is to do.

In order to achieve the above object, a first invention is an exhaust emission control device for a compression ignition type internal combustion engine,
A fuel injection valve for directly injecting fuel into the cylinder of the internal combustion engine;
An exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine;
A variable valve mechanism that is provided in at least one of an intake valve or an exhaust valve of the internal combustion engine and changes an opening / closing timing and / or an operating angle;
A catalyst processing means for determining the necessity of a temperature raising process and / or a reduction process of the exhaust purification catalyst, and when the temperature raising process or the reduction process is determined to be necessary, a catalyst processing means for causing the fuel injection valve to perform post injection;
When post injection is executed, an in-cylinder temperature control means for operating the variable valve mechanism to control the in-cylinder temperature;
It is characterized by having.

According to a second invention, in the first invention,
The in-cylinder temperature control means determines an operation amount of the variable valve mechanism so that an in-cylinder temperature at a post injection timing falls within a predetermined target temperature range set lower than a fuel combustion temperature. It is a feature.

According to a third invention, in the second invention,
The in-cylinder temperature control means acquires an environmental factor affecting the in-cylinder temperature and / or an index value of the internal factor of the internal combustion engine, and corrects an operation amount of the variable valve mechanism based on the index value. It is characterized by.

According to a fourth invention, in the second invention,
The in-cylinder temperature control means corrects the operation amount of the variable valve mechanism in a direction to decrease the in-cylinder temperature as the injection timing of the post injection is advanced to the compression top dead center side. .

According to a fifth invention, in the second invention,
Combustion detection means for detecting fuel combustion by post-injection;
Combustion suppression means that corrects the operation amount of the variable valve mechanism and / or the injection timing of post-injection in a direction to suppress combustion when combustion is detected;
Is further provided.

According to a sixth invention, in the fifth invention,
The combustion suppression means stops control for suppressing combustion when power transmission from the internal combustion engine to the transmission is interrupted.

  According to the first invention, the in-cylinder temperature at the time of post-injection can be positively controlled by operating the variable valve mechanism, and the combustion state of the post-injected fuel can be controlled. For example, the post-injected fuel is not completely burned, but can be thermally decomposed and reformed (lightened). The oxidation reaction on the exhaust purification catalyst is promoted by the reforming of the fuel, and it becomes possible to efficiently raise the temperature or reduce the exhaust purification catalyst.

  According to the second aspect of the present invention, the in-cylinder temperature at the injection timing of the post injection is controlled to a temperature lower than the combustion temperature of the fuel, so that the thermal decomposition can be efficiently performed without burning the fuel.

  According to the third invention, the in-cylinder temperature is set to an optimum temperature for the thermal decomposition of the fuel without being affected by environmental factors (intake air temperature, etc.) and internal factors of the internal combustion engine (cylinder wall surface temperature, EGR rate, etc.). Can be controlled.

  According to the fourth aspect of the invention, when the injection timing of the post injection is advanced to the compression top dead center side, the combustion of the fuel is suppressed by reducing the in-cylinder temperature. Can be advanced, and the dilution of oil by post injection can be suppressed.

  According to the fifth aspect, it is possible to prevent an increase in torque due to combustion of the post-injected fuel.

  According to the sixth aspect of the present invention, when the power transmission in which the torque fluctuation is not transmitted to the occupant is interrupted, the control for suppressing the combustion is stopped, so that the variable valve mechanism in the direction of promoting the thermal decomposition of the fuel. It is possible to positively control the operation amount and post injection timing.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

  FIG. 1 is a schematic configuration diagram of a compression ignition type internal combustion engine as an embodiment of the present invention. The internal combustion engine shown in FIG. 1 is a direct-injection diesel engine, and includes a cylinder block 4 in which a piston 8 is disposed, and a cylinder head 6 assembled to the cylinder block 4. A space from the upper surface of the piston 8 to the cylinder head 6 forms a combustion chamber 10, and an intake port 12 and an exhaust port 14 are formed in the cylinder head 6 so as to communicate with the combustion chamber 10. An intake passage 22 for introducing fresh air into the combustion chamber 10 is connected to the intake port 12, and an exhaust passage 24 for discharging combustion gas is connected to the exhaust port 14.

  In the cylinder head 6, an intake valve 32 is provided at a connection portion between the intake port 12 and the combustion chamber 10. A variable valve mechanism 42 that makes the valve timing and phase variable is attached to the intake valve 32. The variable valve mechanism 42 may be a cam type, an electromagnetic valve, or a hydraulic drive type, and there is no limitation on its structure. FIG. 2 is a graph showing an operation example of the intake valve 32 when the cam type is adopted as the variable valve mechanism 42, the crank angle is taken on the horizontal axis, and the lift amount of the intake valve 32 is taken on the vertical axis. .

  An exhaust valve 34 is provided at a connection portion between the exhaust port 14 and the combustion chamber 10. The exhaust valve 34 is also provided with a variable valve mechanism 44 that makes the valve timing and phase variable. The variable valve mechanism 44 may be any of a cam type, a solenoid valve, or a hydraulic drive type, and its structure is not limited. FIG. 3 is a graph showing an operation example of the exhaust valve 34 when the cam type is adopted as the variable valve mechanism 44, in which the abscissa indicates the crank angle and the ordinate indicates the lift amount of the exhaust valve 34. .

  Further, an injector 30 for directly injecting fuel into the combustion chamber 10 is attached to the top of the combustion chamber 10 in the cylinder head 6. The injector 30 is connected to a common rail (not shown) and receives supply of high-pressure fuel from the common rail. Since the high pressure fuel compressed by the supply pump is always stored in the common rail, the fuel can be injected into the combustion chamber 10 at an arbitrary timing by opening the injector 30.

  The cylinder block 4 is provided with a water temperature sensor 54 that outputs a signal corresponding to the temperature of the cooling water flowing in a water jacket (not shown). Since the coolant temperature represents the cylinder wall temperature, the cylinder wall temperature can be estimated from the signal from the water temperature sensor 54. A crank angle sensor 56 that outputs a signal corresponding to the rotation angle of the crankshaft 16 is attached to the cylinder block 4.

  An exhaust purification catalyst 28 is disposed in the exhaust passage 24. The exhaust purification catalyst 28 may be any catalyst that can at least oxidize HC and can be expected to rise in temperature due to the oxidation reaction of HC. For example, an oxidation catalyst (CCo), DPF, or DPNR catalyst can be used.

  An intake throttle valve 36 is provided in the intake passage 22. The amount of air taken into the combustion chamber 10 can be controlled by adjusting the opening of the intake throttle valve 36. The opening degree of the intake throttle valve 36 is adjusted according to the operating state of the engine. An intake air temperature sensor 52 that outputs a signal corresponding to the temperature of the intake air is attached to the intake passage 22.

  An EGR passage 26 is connected downstream of the intake throttle valve 22 in the intake passage 22. The opposite end of the EGR passage 26 is connected upstream of the exhaust purification catalyst 28 in the exhaust passage 24, and a part of the exhaust gas (EGR gas) is introduced into the intake passage 22 through the EGR passage 26. An EGR valve 38 that opens and closes the EGR passage 26 is provided in the middle of the EGR passage 26.

  The diesel engine of this embodiment includes an ECU (Electronic Control Unit) 50 as its control device. Various devices such as the injector 30, the intake throttle valve 36, the EGR valve 38, and the variable valve mechanisms 42 and 44 are connected to the output side of the ECU 50. In addition to the intake air temperature sensor 52, the water temperature sensor 54, and the crank angle sensor 56 described above, various sensors such as an accelerator opening sensor 58 and a clutch sensor 60 are connected to the input side of the ECU 50. The accelerator opening sensor 58 is a sensor that outputs a signal corresponding to the opening of an accelerator pedal (not shown). The clutch sensor 60 is a sensor that detects engagement / disengagement of a clutch that connects an engine and a transmission (not shown). The ECU 50 drives each device according to a predetermined control program based on the output of each sensor.

  The diesel engine of the present embodiment can execute secondary fuel injection (post injection) separately from normal fuel injection (main injection) as fuel injection by the injector 30. The post-injection is a fuel injection that is executed in the expansion stroke, and is executed for the purpose of raising the temperature and reducing the exhaust purification catalyst 28. Hereinafter, engine control for post injection executed by the ECU 50 in the present embodiment will be described.

  FIG. 4 is a flowchart showing the contents of engine control for post injection executed by the ECU 50 in the present embodiment. In the first step S100 of this routine, it is determined whether or not the post injection permission flag is on. The permission flag is switched from off to on when the post injection execution condition is satisfied, and is switched off again after the post injection is performed. As an execution condition of the post injection, there is a request for either a reduction process of the exhaust purification catalyst 28 or a temperature raising process. The request for the reduction process of the exhaust purification catalyst 28 is issued, for example, when the purification efficiency of the exhaust purification catalyst 28 is lowered to a reference efficiency or less, and the request for the temperature increase process of the exhaust purification catalyst 28 is, for example, the exhaust purification catalyst 28. This occurs when the catalyst temperature of the catalyst falls below a predetermined temperature.

  When the post-injection execution condition is satisfied and the permission flag is turned on, the processes after step S102 are executed. First, in step S102, the in-cylinder temperature control start flag by the intake side variable valve mechanism 42 is switched from OFF to ON. Here, TDC is assumed to be the start timing of post-injection, and the in-cylinder temperature at TDC is aimed at as the in-cylinder temperature (target in-cylinder temperature). The target in-cylinder temperature is set to an optimum temperature at which the fuel can be decomposed and reformed (lightened) without burning the fuel. The operation of the variable valve mechanism 42 during the in-cylinder temperature control is set according to the target in-cylinder temperature.

  In step S104, the target cylinder temperature correction start flag corresponding to the intake air temperature or the cylinder wall temperature is switched from OFF to ON. Regarding intake air temperature and cylinder wall temperature, standard intake air temperature and standard cylinder wall temperature are determined in advance, and the target in-cylinder temperature based on these standard intake air temperature and standard cylinder wall temperature is preset as the standard target in-cylinder temperature. Has been.

  In the next step S106, whether or not the intake air temperature measured from the signal of the intake air temperature sensor 52 is higher than the standard intake air temperature, or the cylinder wall temperature estimated from the signal of the water temperature sensor 54 is higher than the standard cylinder wall temperature. It is determined whether it is high. As a result of the determination, when the intake air temperature or the cylinder wall temperature is higher than the standard value, the process of step S108 is executed, and when it is lower, the process of step S110 is executed.

  In step S108, the target in-cylinder temperature decrease is corrected. If the in-cylinder temperature is affected by environmental factors such as intake air temperature and engine internal factors such as cylinder wall temperature, the engine control conditions (speed, air amount, fuel injection amount, etc.) are the same. The higher the intake air temperature and the cylinder wall temperature, the higher the in-cylinder temperature. The fuel is thermally decomposed by exposure to high temperatures, but if the in-cylinder temperature becomes too high, the ratio of complete combustion of the fuel increases. For this reason, the processing in step S108 is optimized so that the actual in-cylinder temperature can be promoted to thermally decompose the fuel by lowering the target in-cylinder temperature from the standard target in-cylinder temperature when the intake air temperature or the cylinder wall temperature is high. I try to keep it at temperature. The target in-cylinder temperature decrease is set according to the temperature difference between the actual intake air temperature or cylinder wall temperature and the standard intake air temperature or standard cylinder wall temperature.

  On the other hand, in step S110, the target in-cylinder temperature rise is corrected. If the in-cylinder temperature becomes too low, the proportion of fuel that is discharged without being reacted (unreformed) increases. For this reason, when the intake air temperature or the cylinder wall temperature is low, the processing in step S110 is optimized so that the actual in-cylinder temperature can be accelerated by increasing the target in-cylinder temperature above the standard in-cylinder temperature. I try to keep it at temperature. The target cylinder temperature increase range is set according to the temperature difference between the actual intake air temperature or cylinder wall temperature and the standard intake air temperature or standard cylinder wall temperature.

  In step S112, the target in-cylinder temperature corrected in step S108 or step S110 is set as the final target in-cylinder temperature. As a result, the target in-cylinder temperature correction corresponding to the intake air temperature and the cylinder wall temperature is completed, and the target in-cylinder temperature correction start flag is switched from on to off.

  In the next step S114, the post injection timing setting start flag is switched from OFF to ON. In step S116, based on the target in-cylinder temperature set in step S112, the target injection timing is temporarily set in the vicinity of TDC in the expansion stroke. The target injection timing is a target value for the start timing of post injection. The reason why the target injection timing is temporarily set in the vicinity of TDC is to suppress oil dilution due to adhesion of post-injected fuel to the cylinder bore as much as possible. The target injection timing is temporarily set so as to approach TDC as the target in-cylinder temperature is lower.

  In step S118, the target injection timing correction start flag corresponding to the intake air temperature or the cylinder wall temperature is switched from OFF to ON. As in the case of the target in-cylinder temperature, with respect to the intake air temperature and the cylinder wall temperature, the standard intake air temperature and the standard cylinder wall temperature are determined in advance, and the target injection timing temporarily set in step S114 is the standard intake air temperature and the standard cylinder wall temperature. This is the target injection timing (standard target injection timing) based on the cylinder wall temperature.

  In the next step S120, whether or not the intake air temperature measured from the signal of the intake air temperature sensor 52 is higher than the standard intake air temperature, or the cylinder wall temperature estimated from the signal of the water temperature sensor 54 is higher than the standard cylinder wall temperature. It is determined whether it is high. As a result of the determination, when the intake air temperature or the cylinder wall temperature is higher than the standard value, the process of step S122 is executed, and when it is lower, the process of step S124 is executed.

  In step S122, the target injection timing is retarded. Whether the post-injected fuel efficiently decomposes depends on the in-cylinder temperature when the fuel is injected, but the in-cylinder temperature decreases as the distance from the TDC increases. When the intake air temperature or the cylinder wall temperature is high, the process of step S122 is performed when the in-cylinder temperature is at an optimum temperature that can promote the thermal decomposition of the fuel by delaying the target injection timing from the standard target injection timing. The fuel can be injected. It should be noted that the retard width of the target injection timing is set according to the temperature difference between the actual intake air temperature or cylinder wall temperature and the standard intake air temperature or standard cylinder wall temperature.

  On the other hand, in step S124, advance angle correction of the target injection timing is performed. If the in-cylinder temperature becomes too low, the proportion of fuel that is discharged without being reacted (unreformed) increases. For this reason, in the process of step S124, when the intake air temperature or the cylinder wall temperature is low, the in-cylinder temperature is set to the optimum temperature that can promote the thermal decomposition of the fuel by advancing the target injection timing with respect to the standard target injection timing. At some point, fuel can be injected. The advance angle width of the target injection timing is set according to the temperature difference between the actual intake air temperature or cylinder wall temperature and the standard intake air temperature or standard cylinder wall temperature.

  In the next step S126, the post injection end timing is calculated from the target injection timing corrected in step S122 or step S124, and it is determined whether or not the injection end timing is on the retard side with respect to a predetermined threshold value. This threshold value is a limit end timing at which oil dilution is allowed. When the injection end timing is on the retard side of the threshold value, the oil dilution exceeds the allowable range due to fuel adhering to the cylinder bore.

  For this reason, as a result of the determination in step S126, when the injection end timing is on the retard side with respect to the threshold value, the process in step S128 is selected. In step S128, the target in-cylinder temperature decrease is corrected. After the process of step S128, the process returns to step S112 again, and the target in-cylinder temperature that has been corrected to decrease in step S128 is reset as the final target in-cylinder temperature. As a result of the target in-cylinder temperature being lowered, the target injection timing temporarily set in step S116 approaches TDC. Thereby, it is avoided that the end timing of the post-injection is retarded from the threshold value.

  As a result of the determination in step S126, if the injection end timing is not retarded from the threshold value, the process in step S130 is selected. In step S130, the target injection timing corrected in step S122 or step S124 is set as the final target injection timing. Thus, the target injection timing correction according to the intake air temperature and the cylinder wall temperature is completed, and the injection timing correction start flag is switched from on to off.

  When the target in-cylinder temperature and the target injection timing are determined by the series of processes described above, the variable valve mechanism 42 for realizing the target in-cylinder temperature is then driven. The fuel injection by the injector 30 is controlled by another routine (injector drive control routine) executed in parallel with this routine. In the injector drive control routine, the fuel injection mode is selected according to the running state of the vehicle. For example, when the vehicle is in steady running, post-injection is executed following the main injection, and when the vehicle is decelerating, the main injection is cut and only post-injection is executed.

  In step S132, it is determined whether or not a process for reducing the in-cylinder temperature is necessary to achieve the target in-cylinder temperature. When the set target in-cylinder temperature is higher than the standard value, it is necessary to operate the variable valve mechanism 42 to lower the in-cylinder temperature. In this case, the process of step S134 is executed. On the other hand, when the set target in-cylinder temperature is lower than the standard value, it is necessary to operate the variable valve mechanism 42 to increase the in-cylinder temperature. In that case, the process of step S136 is performed.

  In step S134, the variable valve mechanism 42 advances or retards the closing timing of the intake valve (IN valve) 32. The intake air amount in the combustion chamber 10 is determined by closing the intake valve 32. Normally, the intake valve 32 is closed when the intake air amount becomes substantially maximum (for example, the timing indicated by the broken line in FIG. 2). Is set. In step S134, as indicated by a solid line in FIG. 2, the closing timing is advanced (that is, closes earlier) than normal, or is delayed (that is, closes late) than normal. As a result, the amount of intake air is reduced to reduce the substantial compression ratio ε. By reducing the substantial compression ratio ε, an increase in the in-cylinder temperature due to compression can be suppressed, and the in-cylinder temperature in the vicinity of the TDC can be reduced. The advance width (or retard angle width) of the closing timing of the intake valve 32 is set according to the temperature difference between the target in-cylinder temperature and its standard value.

  In step S136, the opening timing of the intake valve 32 is advanced by the variable valve mechanism 42, and the overlap period between the valves 32 and 34 is increased. The closing timing of the intake valve 32 is maintained at a constant timing. As the valve overlap increases, the amount of exhaust gas reintroduced into the combustion chamber 10 increases. Since the exhaust gas is hot, the in-cylinder temperature increases as the amount of exhaust gas reintroduction (internal EGR amount) increases. The increase range of the valve overlap is set according to the temperature difference between the target in-cylinder temperature and its standard value.

  By executing the process of step S134 or step S136, the in-cylinder temperature is controlled to an optimum temperature at which the fuel can be decomposed and reformed without burning the fuel. Thereby, when the reduction process of the exhaust purification catalyst 28 is required, the oxidation reaction of the fuel on the exhaust purification catalyst 28 can be promoted, and NOx can be reduced more efficiently. . Further, since the reformed fuel can react actively even when the catalyst temperature is low, it is possible to achieve high energy efficiency by effectively using the fuel, and the fuel that has not reacted with the exhaust purification catalyst 28 (unreacted). Fuel HC) is also prevented from being released into the atmosphere. Further, when the temperature raising process of the exhaust purification catalyst 28 is required, the catalyst temperature can be efficiently raised by the reaction heat due to the oxidation reaction.

  By realizing the target in-cylinder temperature, the in-cylinder temperature control by the variable valve mechanism 42 ends. In step 138, the in-cylinder temperature control start flag is switched from on to off.

  In the next step S140, the opening timing of the exhaust valve (EX valve) 34 is advanced by the variable valve mechanism 44 on the exhaust side. Specifically, the timing is advanced from the opening timing in the vicinity of BDC indicated by the broken line in FIG. 3 (normal opening timing) to the timing substantially the same as the post injection in the vicinity of TDC indicated by the solid line in FIG. The closing timing of the exhaust valve 34 is maintained at a constant timing. By opening the exhaust valve 34 in this way, the gas containing the post-injected fuel can be discharged to the exhaust port 14 before expanding in the combustion chamber 10.

  According to the process of step S140, the temperature drop of the gas accompanying expansion | swelling can be suppressed by discharging | emitting the gas in the combustion chamber 10 before expansion | swelling. As a result, the post-injected fuel can be exposed to a high temperature for a longer time, and the thermal decomposition of the fuel can be promoted. Further, since the high-temperature gas is supplied to the exhaust purification catalyst 28, it is possible to suppress a decrease in the catalyst temperature, and it is possible to suppress the fuel from adhering to the exhaust passage 24.

  The series of processes described above is a process that is performed in common regardless of whether the vehicle is traveling normally or decelerating. In the next step S142, it is determined whether or not the vehicle is decelerating. When the vehicle is not decelerating, that is, when this routine is being executed during steady running, this routine ends upon completion of the series of processes described above. On the other hand, when the present routine is being executed during deceleration, the routine ends after further processing from step S144 is performed.

  In step S144, the combustion of the post-injected fuel is detected. Whether or not the post-injected fuel is burning can be determined using, for example, the methods listed below.

  The first example is a method for determining based on a change in in-cylinder pressure. The in-cylinder pressure is measured using an in-cylinder pressure sensor. When an increase in in-cylinder pressure with respect to the motoring waveform is observed, or when the in-cylinder pressure increases after TDC, it can be determined that torque is generated by the combustion of post-injected fuel.

  The second example is a method of making a determination based on the exhaust gas temperature on the upstream side of the exhaust purification catalyst 28. The exhaust gas temperature is measured using a temperature sensor. When the exhaust gas temperature rises, it can be determined that the post-injected fuel is burning.

  The third example is a method of making a determination based on fluctuations in engine speed. If the engine speed increases when the clutch is released, it can be determined that torque is generated by the combustion of post-injected fuel.

  In the next step S146, it is determined whether or not the clutch is released based on the signal from the clutch sensor 60. If the result of determination is that the clutch is engaged, the determination in step S148 is further performed. In step S148, the detection result in step S144 is reflected, and it is determined whether or not the post-injected fuel is burning. When the fuel is not combusted, the in-cylinder temperature and the post injection timing are maintained as they are.

  When the post-injected fuel is burning, the process of step S150 is performed. In step S150, control for suppressing fuel combustion, specifically, in-cylinder temperature control by the variable valve mechanism 42 is executed so as to lower the in-cylinder temperature. Alternatively, the post injection timing is retarded within a range where oil dilution is allowed.

  On the other hand, if the result of determination in step S146 is that the clutch is disengaged, processing in step S152 is performed regardless of whether post-injected fuel is burning. In step S152, in-cylinder temperature control by the variable valve mechanism 42 is executed so as to increase the in-cylinder temperature. Alternatively, the post injection timing is advanced so as to inject fuel into a higher temperature atmosphere. When the clutch is released and power transmission from the engine to the transmission is cut off, even if the engine torque fluctuates, it will not be transmitted to the occupant. Therefore, the torque fluctuation in this case can be tolerated, and the operation amount of the variable valve mechanism 42 and the post injection timing can be positively controlled in the direction of promoting the thermal decomposition of the fuel.

  In the diesel engine of the present embodiment, engine control according to the above routine is executed for post injection. According to this engine control, as described above, the post-injected fuel can be thermally decomposed and reformed by the active control of the in-cylinder temperature by the variable valve mechanism 42, instead of completely burning the post-injected fuel. By promoting the oxidation reaction on the exhaust purification catalyst, the exhaust purification catalyst 28 can be efficiently heated or reduced.

  In the present embodiment, the determination in step S100 is executed by the ECU 50, and the post-injection is executed by a routine different from the routine based on the determination result, so that "catalyst processing means" Is realized. Further, the “in-cylinder temperature control means” according to the present invention is realized by the ECU 50 executing a series of processes from step S102 to step S138. Further, the ECU 50 executes the process of step S144 to realize the “combustion detecting means” according to the present invention, and the processes of steps S146 to S152 described above execute the “combustion” according to the present invention. "Suppression means" is realized.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the engine control according to the above embodiment, the in-cylinder temperature is corrected in accordance with the intake air temperature or the cylinder wall temperature. However, other factors that affect the in-cylinder temperature, such as the EGR amount (or EGR rate), are corrected. It is also preferable to correct the target in-cylinder temperature in consideration.

  In the above embodiment, when the in-cylinder temperature is increased, the valve overlap is increased by advancing the opening timing of the intake valve 32. However, the exhaust valve 34 is provided by the variable valve mechanism 44 on the exhaust side. The closing timing may be delayed.

  The means for controlling the in-cylinder temperature is not limited to the variable valve mechanisms 42 and 44. For example, the intake throttle valve 36 can be used as means for increasing the in-cylinder temperature. Further, if the engine is provided with an exhaust throttle valve in the exhaust passage, the exhaust throttle valve can also be used as means for increasing the in-cylinder temperature. Moreover, if it is an engine provided with a supercharger, the in-cylinder temperature can be controlled by the supercharging pressure.

1 is a schematic configuration diagram of a compression ignition type internal combustion engine as an embodiment of the present invention. It is a graph which shows the example of an action | operation of the intake valve by a variable valve mechanism. It is a graph which shows the example of an action | operation of the exhaust valve by a variable valve mechanism. It is a flowchart which shows the routine of the engine control for the post injection implemented in embodiment of this invention.

Explanation of symbols

8 piston 10 combustion chamber 16 crank angle 22 intake passage 24 exhaust passage 26 EGR passage 28 exhaust purification catalyst 30 injector 32 intake valve 34 exhaust valve 36 intake throttle valve 38 EGR valve 42 intake side variable valve mechanism 44 exhaust side variable valve mechanism 44 50 ECU
52 Intake air temperature sensor 54 Water temperature sensor 56 Crank angle sensor 58 Accelerator opening sensor 60 Clutch sensor

Claims (6)

A fuel injection valve for directly injecting fuel into a cylinder of a compression ignition type internal combustion engine;
An exhaust purification catalyst disposed in an exhaust passage of the internal combustion engine;
A variable valve mechanism that is provided in at least one of an intake valve or an exhaust valve of the internal combustion engine and changes an opening / closing timing and / or an operating angle;
A catalyst processing means for determining the necessity of a temperature raising process and / or a reduction process of the exhaust purification catalyst, and when the temperature raising process or the reduction process is determined to be necessary, a catalyst processing means for causing the fuel injection valve to perform post injection;
When post injection is executed, an in-cylinder temperature control means for operating the variable valve mechanism to control the in-cylinder temperature;
An exhaust emission control device for a compression ignition type internal combustion engine.   The in-cylinder temperature control means determines an operation amount of the variable valve mechanism so that an in-cylinder temperature at a post injection timing falls within a predetermined target temperature range set lower than a fuel combustion temperature. The exhaust gas purification apparatus for a compression ignition type internal combustion engine according to claim 1,   The in-cylinder temperature control means acquires an environmental factor affecting the in-cylinder temperature and / or an index value of the internal factor of the internal combustion engine, and corrects an operation amount of the variable valve mechanism based on the index value. 3. An exhaust emission control device for a compression ignition type internal combustion engine according to claim 2.   The in-cylinder temperature control means corrects the operation amount of the variable valve mechanism in a direction to reduce the in-cylinder temperature as the injection timing of post injection is advanced to the compression top dead center side. The exhaust gas purification apparatus for a compression ignition type internal combustion engine according to claim 2. Combustion detection means for detecting fuel combustion by post-injection;
Combustion suppression means that corrects the operation amount of the variable valve mechanism and / or the injection timing of post-injection in a direction to suppress combustion when combustion is detected;
The exhaust gas purification apparatus for a compression ignition type internal combustion engine according to claim 2, further comprising:   6. An exhaust emission control device for a compression ignition type internal combustion engine according to claim 5, wherein the combustion suppression means stops control for suppressing combustion when power transmission from the internal combustion engine to the transmission is interrupted.

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