JP2011252474A - Method and device for controlling engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for controlling an engine, which can achieve both NOx reduction and a regeneration treatment of a particulate filter without reducing sealability of an intake valve during regeneration treatment of the particulate filter.SOLUTION: The method for controlling the engine includes: a filter regeneration step of regenerating the particulate filter by applying post injection; an internal EGR step of refluxing a part of exhaust gas into a cylinder by opening an exhaust valve during an intake stroke; a post injection quantity increasing step of increasing an injection quantity of the post injection with the lapse of time from the post injection starting; and an internal EGR completion step of completing the internal EGR step when the temperature of the particulate filter does not reach a predetermined temperature based on a value related to the temperature of the particulate filter at a point time when the injection quantity of the post injection reaches a predetermined value.

Description

  The present invention relates to an engine control method and control apparatus in which an exhaust valve is configured to be openable and closable during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage.

  Engines for vehicles and the like use an external EGR system that recirculates a part of the exhaust gas from the exhaust passage to the intake passage in order to reduce NOx contained in the exhaust gas, and particularly in a diesel engine, the exhaust passage An oxidation catalyst that oxidizes and purifies HC and CO contained in the exhaust gas and a particulate filter that collects particulate matter (PM) contained in the exhaust gas are disposed, Purifying is generally performed.

  Further, when the amount of particulates collected by the particulate filter increases, so-called post-injection in which fuel is injected into the cylinder after main injection is performed in addition to main injection to inject fuel to be burned in the cylinder. A regeneration process of the particulate filter is performed in which the fuel is supplied to the oxidation catalyst and combusted, and the temperature of the particulate filter is increased by the combustion heat to burn and remove the particulate.

  However, during the regeneration process of the particulate filter, since the exhaust gas becomes high temperature, the EGR valve of the external EGR system may be damaged. Therefore, during the regeneration process of the particulate filter, during the intake stroke instead of the external EGR system. It is known to perform so-called internal EGR to open a part of the exhaust valve and return part of the exhaust gas from the exhaust passage into the cylinder, thereby suppressing combustion and reducing NOx.

  Regarding this internal EGR, for example, Patent Document 1 does not relate to the regeneration processing of the particulate filter. However, when there is a difference between the ignition timing of the air-fuel mixture in the premixed combustion and the appropriate ignition timing, By opening the intake valve during the intake stroke of the engine where the intake valve is open, exhaust gas is introduced into the combustion chamber and the mixture is reduced in oxygen to bring the actual ignition timing closer to the appropriate ignition timing. It is disclosed.

JP 2007-138777 A

  By the way, during the regeneration process of the particulate filter, the post injection is performed and the exhaust valve is opened during the intake stroke to perform the internal EGR, so that the temperature of the particulate filter can be increased while reducing NOx. Part of the unburned fuel from the injection returns to the cylinder together with the exhaust gas, so the unburned fuel supplied to the oxidation catalyst is insufficient, and the temperature of the particulate filter to a predetermined temperature at which particulates can be burned and removed In some cases, the particulate filter cannot be completely regenerated.

  On the other hand, by increasing the amount of post-injection, it is possible to increase the temperature of the particulate filter by increasing the amount of unburned fuel supplied to the oxidation catalyst. At the same time, the amount of unburned fuel that returns to the cylinder also increases, and a portion of the unburned fuel that returns to the cylinder adheres to the intake valve and its seating surface that are open during the intake stroke, reducing the sealing performance of the intake valve. There is drowning.

  Therefore, the present invention provides an engine control method and control device capable of achieving both NOx reduction and particulate filter regeneration processing without reducing the sealing performance of the intake valve during particulate filter regeneration processing. The purpose is to provide.

  For this reason, the invention according to claim 1 of the present application is an engine control method in which an exhaust valve is configured to be openable and closable during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage. A post-injection process in which fuel is injected into the cylinder after the main injection near the compression top dead center to regenerate the particulate filter; and a part of the exhaust gas by opening the exhaust valve during the intake stroke The post-injection amount that increases the amount of post-injection over time after the start of post-injection in the state in which the internal EGR step for returning the fuel to the cylinder, the filter regeneration step, and the internal EGR step are executed And the particulate filter based on a value related to the temperature of the particulate filter when the injection amount of the post injection reaches a predetermined value. If the temperature of the does not reach the predetermined temperature has an internal EGR termination step of terminating the internal EGR process, it is characterized.

  Here, the “predetermined value” at “when the post-injection injection amount reaches a predetermined value” refers to a limit value of the post-injection injection amount that does not deteriorate the sealing performance of the intake valve.

  The invention according to claim 2 of the present application is characterized in that, in the invention according to claim 1, the predetermined value is set based on an amount of unburned fuel in the cylinder.

  Furthermore, the invention according to claim 3 of the present application is an engine control method in which an exhaust valve is configured to be openable and closable during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage, A filter regeneration process for regenerating the particulate filter by performing post injection for injecting fuel into the cylinder after main injection performed near the compression top dead center, and opening an exhaust valve during the intake stroke to remove part of the exhaust gas Post injection amount increase for increasing the post injection amount over time from the start of post injection in the state in which the internal EGR step for returning to the cylinder, the filter regeneration step and the internal EGR step are being executed The temperature of the particulate filter is determined based on a process and a value related to the temperature of the particulate filter after a predetermined time has elapsed from the start of post injection. If it is not expected to reach the constant temperature has an internal EGR termination step of terminating the internal EGR process, characterized in that.

  Furthermore, the invention according to claim 4 of the present application is an engine control device in which an exhaust valve is configured to be openable and closable during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage. Filter regeneration means for regenerating the particulate filter by performing post-injection in which fuel is injected into the cylinder after main injection performed in the vicinity of compression top dead center; and opening part of the exhaust valve during the intake stroke to open a part of the exhaust gas The post-injection amount for increasing the post-injection amount over time from the start of post-injection while the internal EGR means for recirculating the fuel into the cylinder, the filter regeneration means and the internal EGR means are being executed An increasing means, a temperature detecting means for detecting a value related to the temperature of the particulate filter, and the particulate matter when the injection amount of the post injection reaches a predetermined value. Internal EGR control means for controlling to stop execution of the internal EGR means when the temperature of the particulate filter does not reach a predetermined temperature based on a value related to the temperature of the particulate filter. Features.

  According to the invention of claim 1 of the present application, the post-injection injection amount is increased with the passage of time from the start of the post-injection while the filter regeneration step and the internal EGR step are being executed. If the temperature of the particulate filter does not reach the predetermined temperature based on the value related to the temperature of the particulate filter when the amount reaches the predetermined value, the internal EGR process is terminated.

  As a result, the temperature of the particulate filter can be increased while reducing the generation of NOx without reducing the sealing performance of the intake valve until the injection amount of the post injection reaches a predetermined value. After the amount reaches the predetermined value, the temperature of the particulate filter can be raised without ending the internal EGR and lowering the sealing performance of the intake valve, so that the sealing performance of the intake valve is not lowered. , NOx reduction and particulate filter regeneration processing can both be achieved.

  According to the invention of claim 2 of the present application, the predetermined value is set based on the amount of unburned fuel in the cylinder, so that the limit of the injection amount of the post injection that does not deteriorate the sealing performance of the intake valve. Since the value can be set with higher accuracy, NOx can be reduced more effectively, and the above-described effect can be more effectively achieved.

  Further, according to the invention of claim 3 of the present application, the post-injection amount is increased with the passage of time from the start of the post-injection while the filter regeneration step and the internal EGR step are being executed. If it is predicted that the temperature of the particulate filter will not reach the predetermined temperature based on the value related to the temperature of the particulate filter after the lapse of a predetermined time from the start, the internal EGR process is terminated.

  As a result, the temperature of the particulate filter is reduced from the start of the post injection before the post injection amount reaches a predetermined value until the elapse of a predetermined time, while reducing the generation of NOx without reducing the sealing performance of the intake valve. If it is expected that the temperature of the particulate filter will not reach the predetermined temperature after a predetermined time has elapsed since the start of post injection, the internal EGR process is terminated and the sealing performance of the intake valve is lowered. Therefore, the temperature of the particulate filter can be raised, so that both NOx reduction and particulate filter regeneration processing can be achieved without reducing the sealing performance of the intake valve.

  In particular, if the temperature of the particulate filter is predicted not to reach the predetermined temperature before the post injection amount reaches the predetermined value, the internal EGR is terminated, so the temperature of the particulate filter is increased quickly. Therefore, the time for performing the filter regeneration process can be shortened.

  Furthermore, according to the device invention of claim 4 of the present application, the same effect as the method invention of claim 1 of the present application can be obtained.

It is a figure which shows the system configuration | structure of the engine which concerns on embodiment of this invention. It is a figure which shows the opening / closing timing of the intake valve and exhaust valve of the engine. It is a figure which shows the injection timing of the fuel of the said engine. It is a flowchart which shows control of the said engine. FIG. 5 is a diagram illustrating an example of changes in DPF regeneration processing, VVL on / off state, post-injection amount, and DPF temperature when the engine shown in FIG. It is explanatory drawing for demonstrating another control of the said engine. It is a flowchart which shows another control of the said engine. It is a figure which shows an example of the change of the DPF regeneration process and the on / off state of VVL, the post injection amount, the DPF temperature, and the DPF temperature increase rate when the engine shown in FIG. 7 is controlled.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a system configuration of an engine according to an embodiment of the present invention. An engine 1 according to the embodiment of the present invention shown in FIG. 1 is a multi-cylinder diesel engine in which a plurality of cylinders are arranged in a row, and each cylinder of the engine 1 has an intake stroke in which an intake valve 2 is opened. Air is sucked into the combustion chamber 4 from the intake port 3.

  The air sucked into the combustion chamber 4 in the cylinder is compressed by the piston 5 in the compression stroke to be in a high temperature / high pressure state, and the high temperature / high pressure of the combustion chamber 4 in the cylinder from the fuel injection valve 6 near the compression top dead center. Fuel such as light oil is injected into the air in the state, and the fuel self-ignites and burns in the expansion stroke. The combustion gas generated by this combustion, that is, the exhaust gas, is discharged to the exhaust port 8 in the exhaust stroke in which the exhaust valve 7 is opened.

  In the engine 1, a series of these operations are repeated, and the piston 5 repeats reciprocating motion in the cylinder central axis direction in the cylinder. The reciprocating motion of the piston 5 is converted into a rotational motion of the crankshaft 10 via a connecting rod 12 that connects the piston 5 and the pin portion 11 of the crankshaft 10, and is taken out as engine output.

  Fuel is supplied to the fuel injection valve 6 from a fuel tank through a fuel supply passage (both not shown), and a fuel pump and a common rail (not shown) for storing high-pressure fuel are passed through the fuel supply passage. It is installed. Thus, the fuel injection valve 6 can inject high-pressure fuel into the cylinder by opening the fuel injection valve 6. Further, the fuel injection valve 6 can change the injection amount.

  In the engine 1, the fuel injection valve 6 performs main injection that injects fuel into the cylinder near the compression top dead center, and pilot injection that injects fuel into the cylinder before the main injection in order to create a fire type. However, in the filter regeneration process for regenerating the particulate filter, in addition to the pilot injection and the main injection, the post-injection for injecting the fuel into the cylinder after the main injection is controlled.

  The intake valve 2 is opened and closed at a predetermined timing in synchronization with the rotation of the crankshaft 10 by an intake camshaft 13 that is drivingly connected to the crankshaft 10, and the exhaust valve 7 is an exhaust camshaft that is drivingly connected to the crankshaft 10. 14 is opened and closed at a predetermined timing in synchronization with the rotation of the crankshaft 10.

  Further, the exhaust valve 7 is provided with a variable lift amount mechanism (VVL) 15 that can vary the opening / closing timing of the exhaust valve 7 and the valve lift amount. Is configured to be able to open and close during the intake stroke while opening the exhaust valve 7 during the exhaust stroke. In the engine 1, when the VVL is turned on, the exhaust valve 7 is opened during the intake stroke, and internal EGR for returning a part of the exhaust gas into the cylinder can be performed.

  An intake passage 3 that supplies air to the combustion chamber 4 in the cylinder is connected to the intake port 3 that is opened and closed by the intake valve 2, and the intake passage 16 is connected in the flow direction of the air supplied to the combustion chamber 4. A throttle valve 18 is provided on the upstream side of the surge tank 17 that stabilizes the air flow. The throttle valve 18 is controlled in the closing direction so as to reduce the intake air amount when idling, and is fully opened and closed when idling.

  On the other hand, an exhaust port 8 that is opened and closed by the exhaust valve 7 is connected to an exhaust passage 19 that exhausts exhaust gas generated in the combustion chamber 4 in the cylinder to the atmosphere. The exhaust passage 19 is included in the exhaust gas. A diesel particulate filter (DPF) 20 is provided as a particulate filter for collecting particulates to be collected, and HC contained in the exhaust gas upstream of the DPF 20 in the flow direction of the exhaust gas discharged into the atmosphere. An oxidation catalyst 21 for oxidizing and purifying CO is provided.

  The exhaust passage 19 is also provided with a differential pressure sensor 22 that detects a differential pressure before and after the DPF 20. In the engine 1, compression is performed when the differential pressure detected by the differential pressure sensor 22 is equal to or higher than a predetermined pressure. After the main injection performed near the top dead center, post injection is performed to inject fuel into the cylinder, unburned fuel is supplied to the oxidation catalyst 21, and the temperature of the DPF 20 is raised to burn the particulates collected in the DPF 20. The DPF 20 is regenerated.

  The engine 1 is also provided with an external EGR device 23 that recirculates a part of the exhaust gas from the exhaust passage 19 to the intake passage 16 in order to reduce NOx contained in the exhaust gas. The external EGR device 23 includes a recirculation path 24 branched from the exhaust passage 19 upstream of the oxidation catalyst 21 in the exhaust gas flow direction and connected to the intake passage 16 between the throttle valve 18 and the surge tank 17. The passage 24 includes a water-cooled EGR cooler 25 that cools the high-temperature EGR gas and an EGR valve 26 that controls the flow rate of the EGR gas from the upstream side in the flow direction of the EGR gas recirculated from the exhaust passage 19 to the intake passage 16. And are provided.

  In the engine 1, a first temperature sensor 27 that detects the temperature of the exhaust gas is disposed in the exhaust passage 19 in the vicinity of the branch portion of the exhaust passage 19 with the recirculation passage 23, and upstream of the branch portion. A second temperature sensor 28 for detection is disposed upstream of the oxidation catalyst 21 in the exhaust passage 19, and a third temperature sensor 29 for detecting the temperature of the DPF 20 and the rate of increase in the temperature is provided for the DPF 20 in the exhaust passage 19. It is arranged upstream and downstream of the oxidation catalyst 21. As the temperature sensors 27, 28, 29, for example, thermocouples can be used.

  Although not shown in the figure, the configuration related to the engine 1 includes an air cleaner provided in the intake passage 16, an air flow sensor that detects the amount of intake air, an accelerator opening sensor that detects the accelerator opening, and an intake pressure detection An intake pressure sensor for detecting exhaust pressure, an exhaust pressure sensor for detecting exhaust pressure, an engine speed sensor for detecting engine speed, and the like are provided.

  Further, the engine 1 is provided with a control unit C that controls the engine 1 and the configuration related thereto. The control unit C is a comprehensive control device for the engine 1, and includes temperature sensors 27, 28, 29, a differential pressure sensor 22, an air flow sensor, an accelerator opening sensor, an intake pressure sensor, an exhaust pressure sensor, and an engine speed sensor. Various operation controls of the throttle valve 18, EGR valve 26, fuel injection valve 6, lift amount variable mechanism 15 and the like are performed based on various control information from the above.

  In the present embodiment, when the regeneration process of the DPF 20 is performed, the control unit C opens the exhaust valve 7 during the intake stroke and performs post-injection. Post-injection is an injection amount with the passage of time from the start of post-injection. When the injection amount of the post injection reaches a predetermined value that is a limit value that does not deteriorate the sealing performance of the intake valve 2, the temperature of the DPF 20 does not reach a predetermined temperature at which particulates can be burned and removed. In this case, control is performed so as to stop opening the exhaust valve 7 during the intake stroke.

  Further, the control unit C can calculate the amount of unburned fuel in the cylinder when the exhaust valve 7 is opened and the post injection is performed during the intake stroke. The amount of unburned fuel in the cylinder is calculated from the engine speed, the intake pressure, the exhaust pressure, the post injection amount, and the like. Note that the control unit C includes a microcomputer as a main part.

  In the engine 1 having the above configuration, during normal operation, while the NOx is reduced using the external EGR device 24 and the particulates are collected using the DPF 20, as described above, For example, when the differential pressure before and after the DPF 20 detected by the differential pressure sensor 22 exceeds a predetermined pressure, the EGR valve 26 is closed and the regeneration of the DPF 20 is started.

  In the present embodiment, a filter regeneration process for regenerating the particulate filter by performing post injection, an internal EGR process for recirculating a part of the exhaust gas into the cylinder by opening the exhaust valve during the intake stroke, and a filter regeneration process And a post injection amount increasing step of increasing the injection amount of the post injection with the passage of time from the start of the post injection.

  FIG. 2 is a diagram showing the opening / closing timings of the intake valve and the exhaust valve of the engine. FIG. 2 shows the opening / closing timings of the intake valve and the exhaust valve when the internal EGR process is performed. FIG. 3 is a diagram showing the fuel injection timing of the engine, and FIG. 3 shows the fuel injection timing when the filter regeneration process is performed. In the engine 1, when the regeneration of the DPF 20 is started, first, as shown in FIG. 2, the intake valve 2 and the exhaust valve 7 are opened in the intake stroke, and as shown in FIG. In addition to injection, post injection is performed.

Hereinafter, the control during the filter regeneration process executed in the engine 1 will be described.
FIG. 4 is a flowchart showing the control of the engine, and FIG. 5 shows changes in the DPF regeneration process, VVL on / off state, post injection amount, and DPF temperature when the engine control shown in FIG. 4 is performed. It is a figure which shows an example. In FIG. 5, the period during which the regeneration process of the DPF 20 is performed is expressed as time t ₁ to time t ₄ , and the limit value that is the limit value at which the post-injection injection amount does not deteriorate the sealing performance of the intake valve 2 is expressed as Q _L. represents represents the temperature of the DPF20 at time _{t 1} as _{T 0,} a predetermined temperature which can be removed by burning particulates were collected in DPF20 as _{T D.}

In the engine 1, for example, when the differential pressure before and after the DPF 20 detected by the differential pressure sensor 22 exceeds a predetermined pressure, regeneration of the DPF 20 is started (step S1), the VVL is turned on, and the exhaust valve is turned on during the intake stroke. The operation of the exhaust valve 7 is controlled to open 7 (step S2), and the injection amount of post injection is set (step S3). As shown in FIG.
Until post injection amount reaches the limit value Q _L is the injection amount over time from the start the post injection is set to increase.

Then, in addition to the pilot injection and the main injection, the operation of the fuel injection valve 6 is controlled so that the post injection is performed with the injection amount set in step S3 (step S4). Next, VVL whether is ON is determined (step S5), and this is the case of YES, that if VVL is on, limit _{Q L} of the post injection amount is set (step S6).

The limit value Q _L of the post-injection amount is set based on the amount of unburned fuel in the cylinder, and when the amount of unburned fuel in the cylinder is large, compared to the case where the amount of unburned fuel in the cylinder is small. Since unburned fuel tends to adhere to the intake valve 2 and its seating surface, the unburned fuel is set smaller than the case where the amount of unburned fuel in the cylinder is small.

When the limit value Q _L in the post-injection amount is set in step S6, the post-injection amount set in the step S3 whether reached the limit value Q _L in the post injection amount is determined (step S7). At the beginning post injection, since the result of the determination in step S7 is NO, that is, the post injection amount does not reach the limit value Q _L, then, whether or not the reproduction of the DPF20 has been completed is determined ( Step S10).

  Since the determination result in step S10 is NO at the start of post-injection, that is, the regeneration of the DPF 20 is not completed, the process returns to step S3, where the injection amount of post-injection increases with time from the start of post-injection. It is set to increase (step S3), and post injection is performed with the injection amount set in step 3 (step S4).

Then, VVL whether is ON is determined (step S5), and since VVL is on, the limit value Q _L in the post injection amount is set (step S6), and the post injection amount is the limit value Q _L It is determined whether or not it has been reached (step S7). Steps S10 and S3 to S6 are repeated until the determination result in step S7 becomes YES, that is, until the post injection amount reaches the limit value. If the determination result in step S7 becomes YES, that is, the post injection amount is Upon reaching the limit value Q _L, the temperature of the DPF20 whether not reached the predetermined temperature T _D which can be removed by burning particulates is determined (step S8).

If the determination in step S8 is YES, i.e., when the temperature of the DPF20 has not reached the predetermined temperature T _D, VVL is turned off, the exhaust valve so as to stop the opening of the exhaust valve 7 during the intake stroke 7 is controlled (step S9). As shown in FIG. 5, when the temperature of the DPF20 in the post-injection amount limit value Q _L time reaches the t ₂ it has not reached the predetermined temperature T _D is the VVL off.

Then, it is determined whether the regeneration of the DPF 20 is completed (step S10). If the determination result in step S10 is NO, that is, if regeneration of the DPF 20 is not completed, the process returns to step S3, the post injection amount is set, and post injection is performed (step S4). After VVL is turned off, even if the post injection amount is increased from the limit value Q _L , the sealing performance of the intake valve 2 is not deteriorated. Therefore, the post injection amount further increases with the passage of time from the start of post injection. It is set to increase.

After the VVL is turned off, the determination result in step S5 is NO, so steps S3 and S4 are repeated until the regeneration of the DPF 20 is completed. As shown in FIG. 5, until time t ₃ when the temperature reaches the predetermined temperature T _D of the DPF 20, the post injection amount, increasing the amount of injection amount over time from the start of the post injection, the predetermined temperature the temperature of the DPF 20 is T After reaching _D , the post injection amount is set so as to maintain a predetermined temperature. When the determination result in step S10 is YES, that is, when it is determined that the regeneration of the DPF 20 is completed, the post injection is stopped and the regeneration process of the DPF 20 is ended. Whether or not the regeneration of the DPF has been completed is determined, for example, based on whether or not the differential pressure detected by the differential pressure sensor 22 has become a predetermined pressure or less, or whether or not the regeneration time has elapsed.

On the other hand, when the determination in step S7 becomes to YES, if the result of the determination in step S8 is NO, that is, when the temperature of the DPF20 has reached a predetermined temperature _{T D,} until the reproduction of the DPF20 is completed The post-injection is performed with the injection amount set to the limit value Q _L while the VVL is turned on. When the determination result in step S10 is YES, that is, when it is determined that the regeneration of the DPF 20 is completed, the VVL is turned off and the post injection is stopped, and the regeneration process of the DPF 20 is ended.

As described above, in the control of the engine 1 according to the present embodiment, the post-injection is performed to regenerate the DPF 20, and the exhaust valve 7 is opened during the intake stroke to recirculate a part of the exhaust gas into the cylinder. A post-injection amount increasing step for increasing the injection amount of the post-injection as time elapses from the start of post-injection in a state where the internal EGR step, the filter regeneration step, and the internal EGR step are executed, the value relating to the temperature of the DPF20 when the injection quantity has reached a predetermined value _{Q L,} the internal EGR end temperature of DPF20 based specifically on the temperature of the DPF20 is if does not reach the predetermined temperature _{T D} to terminate the internal EGR process And a process.

Thus, the temperature of the DPF 20 can be raised while reducing the generation of NOx without reducing the sealing performance of the intake valve 2 until the injection amount of the post injection reaches the predetermined value Q _L , and after the injection quantity has reached a predetermined value Q _L, without lowering the sealing performance of the intake valve 2 to end the internal EGR, it is possible to raise the temperature of the DPF 20, thereby lowering the sealing performance of the intake valve Therefore, both reduction of NOx and regeneration processing of the particulate filter can be achieved.

Further, by setting the predetermined value Q _L based on the amount of unburned fuel in the cylinder, the limit value of the post-injection injection amount that does not deteriorate the sealing performance of the intake valve can be set with higher accuracy. Therefore, NOx can be reduced more effectively, and the effect can be more effectively achieved.

In the control of the engine 1 shown in FIG. 4, during the regeneration process of the DPF 20, the exhaust valve 7 is opened during the intake stroke, and the post injection is performed by increasing the injection amount over time from the start of the post injection. the temperature of the DPF20 when it reaches the value Q _L is off the VVL if does not reach the predetermined temperature T _D, before the injection quantity reaches the predetermined value Q _L, the injection quantity reaches a predetermined value Q _L If the temperature of the DPF20 in time is not expected to reach a predetermined temperature T _D is also possible to turn off the VVL at that time.

FIG. 6 is an explanatory diagram for explaining another control of the engine. When the injection amount reaches the predetermined value Q _L before the injection amount reaches the predetermined value Q _L , the temperature of the DPF 20 becomes the predetermined temperature T. FIG. 6 is a diagram showing changes in DPF regeneration processing, VVL on / off state, post-injection amount, and DPF temperature when control for turning off VVL is performed when it is predicted that _D will not be reached.

As shown in FIG. 6, during the regeneration process of the DPF 20, the VVL is turned on, the exhaust valve 7 is opened during the intake stroke, and the post injection is performed by increasing the injection amount over time from the start of the post injection. At a time t ₂ ′ after the elapse of a predetermined time from the start of post-injection before reaching the predetermined value Q _L , a value related to the temperature of the DPF 20 is detected. Specifically, the temperature T ₂ ′ of the DPF 20 is detected and detecting the rate of rise of temperature, the detected DPF 20 based on the temperature increase rate of the temperature _{T 2} 'and DPF 20, it estimates the temperature _{T 2} of the DPF 20 at time _{t 2,} the estimated time _{t 2} in DPF 20 If temperature T ₂ has not reached the predetermined temperature T _D can also der be controlled to increase the temperature of the DPF20 by the post injection to clear the VVL .

In this case, the control unit C estimates the temperature T ₂ of the DPF 20 at the time t ₂ based on the temperature of the DPF 20 at the time t ₂ ′ detected by the third temperature sensor 29 and the rate of increase in the temperature. , if the temperature _{T 2} of the DPF20 in the estimated time _{t 2} has not reached the predetermined temperature _{T D} is controlled so as to turn off the VVL.

Thus, in the control of the engine 1, if the injection amount of the post injection temperature of DPF20 based on the temperature of the DPF20 Once at the prescribed value Q _L does not reach the predetermined temperature T _D to end the internal EGR process Instead, the temperature T _{2 of} the DPF 20 is set to the predetermined temperature based on the value related to the temperature of the DPF 20 at the time t ₂ after the elapse of a predetermined time from the start of the post injection, specifically, the temperature T ₂ of the DPF 20 and the rate of increase of the temperature. it is also possible to end the internal EGR process when it is not expected to reach the T _D.

Even in such a case, from the start of the post injection before the post injection amount reaches the predetermined value Q _L to the elapse of the predetermined time, the DPF 20 reduces the generation of NOx without reducing the sealing performance of the intake valve 2. temperature can be raised, and after a predetermined time has elapsed from the start the post injection, when the temperature of the DPF20 is not expected to reach a predetermined temperature T _D, the seal of the intake valve 2 to end the internal EGR process Since the temperature of the DPF 20 can be raised without lowering the performance, it is possible to achieve both NOx reduction and particulate filter regeneration processing without lowering the sealing performance of the intake valve.

In particular, at time _{t 2} 'prior to the injection quantity of post injection reaches the predetermined value _{Q L,} so it ends the internal EGR when the temperature of the DPF20 is not expected to reach a predetermined temperature _{T D,} the temperature of the DPF20 As a result, the time for performing the regeneration process of the DPF 20 can be shortened.

In control of the engine 1 shown in FIG. 4, when the temperature of the DPF20 when the injection quantity of post injection has reached a predetermined value Q _L does not reach the predetermined temperature T _D is also predetermined value injection quantity of post injection Q _L it is also possible to perform the post-injection while to turn on the VVL when the temperature of the DPF20 when executing the post injection a predetermined time at the set state is expected to reach a predetermined temperature T _D.

FIG. 7 is a flowchart showing still another control of the engine. FIG. 8 shows a DPF regeneration process and the VVL on / off state, post injection amount, DPF when the engine control shown in FIG. 7 is performed. It is a figure which shows an example of a change of temperature and a DPF temperature rise rate. In the engine control shown in FIG. 7, the same steps as those of the engine control shown in FIG. In FIG. 8, the period for performing the regeneration process of the DPF 20 is expressed as time t ₁₁ to time t ₁₄ , the time when the post injection amount reaches the limit value Q _L is expressed as t ₁₂ , and the injection amount is set to the predetermined value Q _L. it represents the post injection as a time t ₁₃ the period from time t ₁₂ to execute a predetermined time at the set state.

Also in the engine control shown in FIG. 7, similar to the engine control shown in FIG. 4, the regeneration of the DPF 20 is started (step S1), the VVL is turned on (step S2), and the post-injection injection amount is set. (Step S3). Post injection, until the post-injection amount reaches the limit value Q _L is the injection amount over time from the start the post injection is set to increase.

Next, VVL whether is ON is determined (step S5), and if the VVL is on, limit Q _L of the post injection amount is set (step S6), and the post-injection amount of the post injection amount whether the host vehicle has reached the limit value Q _L is determined (step S7). Step S10 until the post-injection amount reaches the limit value _{Q L,} S3 to S6 is repeated and the post injection amount reaches the limit value _{Q L} at time _{t 12,} the temperature of the DPF20 is not reached the predetermined temperature _{T D} It is determined whether or not there is (step S8).

If the determination in step S8 is NO, that is if the temperature of the DPF20 has reached a predetermined temperature _{T D,} similarly to the control of the engine shown in FIG. 4, until the reproduction of the DPF20 is completed, VVL is on remain in the state they were in, the post injection is performed in a state in which the injection quantity is set to the limit value Q _L.

On the other hand, when the result of the determination in step S8 is YES, i.e., when the temperature of the DPF20 has not reached the predetermined temperature T _D Further, whether or not the temperature of the DPF20 within predetermined time has not reached the predetermined temperature T _D is Determination is made (step S11). State in the post-injection quantity limit value Q time t ₁₂ that reaches _L, and the value relating to the temperature of the DPF 20, in particular based on the temperature and the temperature rise rate of DPF 20, and sets the injection quantity to a predetermined value Q _L in the post injection (to the time _{t 13} from the time _{t 12)} a predetermined time at time _{t 13} when running temperature of the DPF20 whether not reach the predetermined temperature _{T D} is determined.

If the determination in step S11 is YES, that is, when the temperature of the DPF20 within predetermined time has not reached the predetermined temperature T _D, VVL is turned off (step S9), and similar to the control of the engine shown in FIG. 4 described above It is controlled, if the determination in step S11 is NO, that is, when the temperature of the DPF20 within a predetermined time reaches a predetermined temperature _{T D,} the step S10, S 3 to S 8, S11 is repeated.

As shown in FIG. 8, on the basis of the post-injection quantity limit value Q _L time reaches the t ₁₂ to the rate of increase in temperature and the temperature of the DPF 20, the post injection in a state of setting the injection quantity to a predetermined value Q _L at time t ₁₃ when executing a predetermined time temperature DPF20 may reach the predetermined temperature T _D is in a state of turning on the VVL, post injection is performed by setting the injection quantity to a predetermined value Q _L.

  When the determination result in step S10 is YES, that is, when it is determined that the regeneration of the DPF 20 is completed, the VVL is turned off and the post injection is stopped, and the regeneration process of the DPF 20 is ended.

In this case, the control unit C performs the post operation in a state where the injection amount is set to the predetermined value Q _L based on the temperature of the DPF 20 at the time t ₁₂ detected by the third temperature sensor 29 and the increase rate of the temperature. injection estimates the temperature of the DPF20 at time _{t 13} when executing a predetermined time, the temperature _{T 13} of DPF20 in the estimated time _{t 13} is if it does not reach the predetermined temperature _{T D} to clear the VVL, estimated time If the temperature _{T 13} of DPF20 at t ₁₃ reaches a predetermined temperature _{T D} is controlled so as to continue while turning on the VVL.

Thus, in yet another control of the engine 1 according to the present embodiment, a filter regeneration process for regenerating the DPF 20 by performing post injection, and opening a part of the exhaust gas by opening the exhaust valve 7 during the intake stroke. A post injection amount increasing step for increasing the injection amount of the post injection with the passage of time from the start of the post injection in a state in which the internal EGR step for returning to the inside, the filter regeneration step and the internal EGR step are being executed; If the injection quantity of post injection value relating to the temperature of the DPF 20 when it reaches a predetermined value Q _L, the temperature of in particular based on the temperature and the temperature rise rate of DPF 20 DPF 20 does not reach a predetermined temperature T _D is An internal EGR process for ending the internal EGR process.

Thus, the temperature of the DPF 20 can be raised while reducing the generation of NOx without reducing the sealing performance of the intake valve 2 until the injection amount of the post injection reaches the predetermined value Q _L , and after the injection quantity has reached a predetermined value Q _L, sealing of the intake valve 2 to end the internal EGR when the temperature of the DPF20 based on the temperature and the temperature rise rate of not reach the predetermined temperature T _D of the DPF20 Since the temperature of the DPF 20 can be raised without lowering the NOx, it is possible to achieve both NOx reduction and particulate filter regeneration without reducing the sealing performance of the intake valve.

In yet another control of the engine 1 according to this embodiment, the temperature is the predetermined temperature T _D of the DPF20 based on the injection quantity increasing rate of the temperature and the temperature of the DPF20 Once at the prescribed value Q _L in the post-injection If it reaches, the internal EGR process is continued, so that NOx can be reduced more effectively, and the reduction of NOx and the regeneration process of the particulate filter can be achieved without reducing the sealing performance of the intake valve 2. Can do.

The control unit C includes a filter regeneration unit as a filter regeneration unit that performs post injection to regenerate the DPF 20, and an internal EGR that opens the exhaust valve 7 during the intake stroke to recirculate a part of the exhaust gas into the cylinder. The post as a post injection amount increasing means for increasing the injection amount of the post injection with the passage of time from the start of the post injection in the state where the internal EGR section as the means, the filter regeneration means and the internal EGR means are executed. and injection amount increasing unit, so if the injection amount of the post injection temperature of DPF20 based on the value relating to the temperature of the DPF when it reaches a predetermined value does not reach a predetermined temperature T _D to stop the execution of the internal EGR means And an internal EGR control unit as internal EGR control means for controlling.

  The present invention is not limited to the illustrated embodiments, and it goes without saying that various improvements and design changes are possible without departing from the spirit of the present invention.

  The present invention relates to engine control capable of achieving both NOx reduction and particulate filter regeneration processing while suppressing unburned fuel from adhering to an intake valve during particulate filter regeneration processing. For example, the present invention can be suitably applied to an engine such as a vehicle in which an oxidation catalyst and a particulate filter are disposed in an exhaust passage.

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake valve 6 Fuel injection valve 7 Exhaust valve 15 Lift amount variable mechanism 19 Exhaust passage 20 DPF
21 Oxidation catalyst 27, 28, 29 Temperature sensor C Control unit

Claims (4)

An engine control method in which an exhaust valve can be opened and closed during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage,
A filter regeneration step of regenerating the particulate filter by performing post injection for injecting fuel into the cylinder after main injection performed near the compression top dead center;
An internal EGR process in which an exhaust valve is opened during the intake stroke to recirculate part of the exhaust gas into the cylinder;
A post-injection amount increasing step for increasing the injection amount of the post-injection as time elapses from the start of post-injection in a state in which the filter regeneration step and the internal EGR step are performed;
An internal EGR end step of ending the internal EGR step when the temperature of the particulate filter does not reach the predetermined temperature based on a value related to the temperature of the particulate filter when the injection amount of the post injection reaches a predetermined value When,
An engine control method comprising: The predetermined value is set based on the amount of unburned fuel in the cylinder;
The engine control method according to claim 1. The engine control method is configured such that the exhaust valve can be opened and closed during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage,
A filter regeneration step of regenerating the particulate filter by performing post injection for injecting fuel into the cylinder after main injection performed near the compression top dead center;
An internal EGR process in which an exhaust valve is opened during the intake stroke to recirculate part of the exhaust gas into the cylinder;
A post-injection amount increasing step for increasing the injection amount of the post-injection as time elapses from the start of post-injection in a state in which the filter regeneration step and the internal EGR step are performed;
When the temperature of the particulate filter is predicted not to reach a predetermined temperature based on a value related to the temperature of the particulate filter after a predetermined time has elapsed from the start of post injection, the internal EGR process is terminated. Process,
An engine control method comprising: An engine control device in which an exhaust valve is configured to be openable and closable during an intake stroke, and an oxidation catalyst and a particulate filter are disposed in an exhaust passage,
Filter regeneration means for regenerating the particulate filter by performing post injection for injecting fuel into the cylinder after main injection performed near the compression top dead center;
An internal EGR means for opening an exhaust valve during the intake stroke to recirculate part of the exhaust gas into the cylinder;
Post injection amount increasing means for increasing the injection amount of the post injection with the passage of time from the start of post injection in a state where the filter regeneration means and the internal EGR means are being executed;
Temperature detecting means for detecting a value related to the temperature of the particulate filter;
If the temperature of the particulate filter does not reach a predetermined temperature based on a value related to the temperature of the particulate filter when the post injection amount reaches a predetermined value, the execution of the internal EGR means is stopped. Internal EGR control means to control;
An engine control device characterized by comprising:

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