阅读说明：本技术 内燃机的排气净化装置 (Exhaust gas purification device for internal combustion engine ) 是由 金子真也 久保田博文 于 2021-03-22 设计创作，主要内容包括：本发明涉及内燃机的排气净化装置,该内燃机的排气净化装置在具备具有颗粒状物质(PM)的捕集功能的颗粒过滤器(GPF)的内燃机中能够增加GPF的再生机会而防止PM堆积量的增大。内燃机的排气净化装置具备：GPF,捕集排气中的PM；自动变速器,具备带锁止离合器的变矩器；及控制装置,在内燃机的减速中且自动变速器的润滑油(ATF)的油温比判定值高的情况下以进行燃料切断的方式控制内燃机,并且在燃料切断的执行中以将锁止离合器接合的方式控制自动变速器。控制装置推定向GPF堆积的PM的堆积量,在该堆积量超过预定的第一堆积量的情况下,将判定值设定为比堆积量超过第一堆积量之前小的值。(The present invention relates to an exhaust emission control device for an internal combustion engine, which is capable of preventing an increase in the amount of PM accumulation by increasing the opportunity for GPF regeneration in an internal combustion engine provided with a particulate filter (GPF) having a function of trapping Particulate Matter (PM). An exhaust gas purification device for an internal combustion engine is provided with: GPF for trapping PM in exhaust gas; an automatic transmission provided with a torque converter having a lockup clutch; and a control device that controls the internal combustion engine so as to perform a fuel cut when the internal combustion engine is decelerating and an oil temperature of a lubricating oil (ATF) of the automatic transmission is higher than a determination value, and controls the automatic transmission so as to engage the lockup clutch during execution of the fuel cut. The control device estimates a deposition amount of PM deposited on the GPF, and sets the determination value to a value smaller than that before the deposition amount exceeds a first deposition amount when the deposition amount exceeds a predetermined first deposition amount.)

1. An exhaust purification device for an internal combustion engine, comprising:

a particulate filter disposed in an exhaust passage of an internal combustion engine and configured to collect particulate matter in exhaust gas;

an automatic transmission provided with a torque converter having a lockup clutch; and

a control device that controls the internal combustion engine so as to perform a fuel cut when the internal combustion engine is decelerating and a temperature-related value of lubricating oil of the automatic transmission is higher than a determination value, and controls the automatic transmission so as to engage the lock-up clutch while the fuel cut is being performed,

the control device is configured to include:

a deposition amount estimation unit configured to estimate a deposition amount of the particulate matter deposited on the particulate filter; and

and a determination value changing unit that changes the determination value to a value smaller than that before the accumulation amount exceeds a predetermined first accumulation amount when the accumulation amount exceeds the first accumulation amount.

2. The exhaust gas purifying apparatus of an internal combustion engine according to claim 1,

the control device further includes an air-fuel ratio control unit that changes a target air-fuel ratio of the internal combustion engine to a lean air-fuel ratio when the accumulation amount exceeds a second accumulation amount that is larger than the first accumulation amount, compared to before the accumulation amount exceeds the second accumulation amount.

3. The exhaust gas purifying apparatus of an internal combustion engine according to claim 2,

the air-fuel ratio control unit is configured to prohibit a change of the target air-fuel ratio to a lean air-fuel ratio when an intake air amount of the internal combustion engine is larger than a predetermined determination air amount.

4. The exhaust gas purifying apparatus of an internal combustion engine according to claim 2 or 3,

the air-fuel ratio control unit is configured to change the target air-fuel ratio of the internal combustion engine to a lean air-fuel ratio within a range not reaching a combustion variation limit of the internal combustion engine.

5. The exhaust gas purification apparatus of an internal combustion engine according to any one of claims 2 to 4,

the air-fuel ratio control unit is configured to change the target air-fuel ratio to a leaner air-fuel ratio as the water temperature of the internal combustion engine increases.

Technical Field

The present disclosure relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly, to an exhaust gas purification apparatus for an internal combustion engine having a particulate filter for trapping particulate matter.

Background

For the purpose of improving fuel economy of a vehicle using an internal combustion engine as a power source, fuel cut for stopping fuel injection may be performed during deceleration of the vehicle. During the fuel cut, the internal combustion engine may stall due to a decrease in the rotation speed of the output shaft. In the technique described in patent document 1, in a vehicle provided with a torque converter with a lock-up clutch, the lock-up clutch is controlled to an engaged state or a semi-engaged state during execution of a fuel cut, thereby preventing a stall.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent application No. 2008-025376

Disclosure of Invention

Problems to be solved by the invention

Among Gasoline engines that perform stoichiometric combustion, there are Gasoline engines that include a Gasoline Particulate Filter (GPF) in the exhaust passage. GPF prevents PM from being discharged to the outside by collecting Particulate Matter (PM) discharged from an internal combustion engine. In the regeneration treatment for removing PM deposited on GPF, it is necessary to increase the temperature of GPF and supply oxygen to GPF. In a gasoline engine, the GPF regeneration process is mainly performed during fuel cut for supplying oxygen to the GPF.

Here, during the fuel cut, it is required to engage a lock-up clutch of the automatic transmission in order to prevent the internal combustion engine from stalling. However, the lockup clutch is not able to be engaged at any time. When the temperature of atf (automatic Transmission fluid), which is a lubricating oil of an automatic Transmission, is extremely low (for example, -10 ℃), vibration called chattering vibration may occur due to engagement of the lock-up clutch. Therefore, the execution of the fuel cut is also restricted under the condition that the engagement of the lock-up clutch is restricted, such as when the ATF oil temperature is extremely low.

The particulate matter PM is particularly easily discharged when the internal combustion engine is cold. Therefore, under a condition that a short stroke of the internal combustion engine is frequently performed in an extremely cold environment or the like, there is a possibility that a sufficient opportunity for the GPF regeneration process cannot be obtained and the amount of PM deposition increases. If the PM deposition amount to the GPF increases, the exhaust pressure increases due to the increase in pressure loss, which leads to deterioration in combustion of the internal combustion engine and deterioration in fuel economy.

The present disclosure has been made in view of the above-described problems, and an object thereof is to provide an exhaust gas purification apparatus for an internal combustion engine, which is provided with a GPF having a PM trapping function, and which is capable of increasing the opportunity of GPF regeneration and preventing an increase in the amount of PM accumulation.

Means for solving the problems

In order to solve the above problems, the disclosure 1 is applied to an exhaust gas purification apparatus for an internal combustion engine. The exhaust gas purification device is provided with: a particulate filter disposed in an exhaust passage of an internal combustion engine and configured to collect particulate matter in exhaust gas; an automatic transmission provided with a torque converter having a lockup clutch; and a control device that controls the internal combustion engine so as to perform a fuel cut when the internal combustion engine is decelerating and the temperature-related value of the lubricating oil of the automatic transmission is higher than the determination value, and controls the automatic transmission so as to engage the lock-up clutch during execution of the fuel cut. The control device is configured to include: a deposition amount estimating unit that estimates a deposition amount of the particulate matter deposited on the particulate filter; and a determination value changing unit that changes the determination value to a value smaller than the value before the accumulation amount exceeds a predetermined first accumulation amount when the accumulation amount exceeds the first accumulation amount.

The 2 nd publication also has the following features in the 1 st publication.

The control device further includes an air-fuel ratio control portion that changes the target air-fuel ratio of the internal combustion engine to a lean air-fuel ratio, when the accumulation amount exceeds a second accumulation amount that is larger than the first accumulation amount, than before the accumulation amount exceeds the second accumulation amount.

The 3 rd publication also has the following features in the 2 nd publication.

The air-fuel ratio control unit is configured to prohibit a change from the target air-fuel ratio to a lean air-fuel ratio when an intake air amount of the internal combustion engine is larger than a predetermined determination air amount.

The 4 th publication also has the following features in the 2 nd or 3 rd publication.

The air-fuel ratio control unit is configured to change the target air-fuel ratio of the internal combustion engine to a lean air-fuel ratio within a range not reaching the combustion variation limit of the internal combustion engine.

The publication of 5 also has the following features in any 1 publication of the 2 nd to 4 th publications.

The air-fuel ratio control unit is configured to change the target air-fuel ratio to a leaner air-fuel ratio as the water temperature of the internal combustion engine increases.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the disclosure of claim 1, when the amount of accumulation of Particulate Matter (PM) in the particulate filter increases, the opportunity of execution of fuel cut during deceleration can be increased. This can increase the chances of regeneration of the particulate filter, and thus can prevent an increase in the amount of PM accumulation.

Further, according to the disclosure of claim 2, by changing the target air-fuel ratio to a lean air-fuel ratio, the regeneration efficiency of the particulate filter can be improved.

Further, according to the disclosure of claim 3, when the intake air amount is larger than the determination air amount, the change of the target air-fuel ratio to the lean air-fuel ratio is prohibited. This can prevent an increase in the amount of exhaust NOx.

Further, according to the disclosure 4, it is possible to prevent control to a lean air-fuel ratio beyond the combustion variation limit of the internal combustion engine.

Further, according to the disclosure of the 5 th publication, the lean air-fuel ratio can be optimized in accordance with the water temperature.

Drawings

Fig. 1 is a diagram for explaining the structure of an exhaust gas purification device according to embodiment 1.

Fig. 2 is a diagram showing functional blocks of the ECU.

Fig. 3 is a flowchart showing a routine of deceleration fuel cut control executed in embodiment 1.

Fig. 4 is a timing chart for explaining a difference in the GPF regeneration performance depending on whether or not the deceleration lock-up allowable oil temperature changing process is executed.

Fig. 5 is a flowchart showing a control routine of the PM accumulation amount estimation process executed in the ECU.

Fig. 6 is a diagram showing an example of a PM discharge map in which an estimated accumulation amount with respect to the engine speed NE and the engine load KL is defined.

Fig. 7 is a diagram showing an example of an air-fuel ratio correction map for calculating a correction coefficient with respect to an estimated accumulation amount of the air-fuel ratio.

Fig. 8 is a diagram showing an example of a water temperature correction map for calculating a correction coefficient of an estimated accumulation amount with respect to the engine water temperature.

Fig. 9 is a diagram showing an example of a regeneration amount map for calculating an estimated regeneration amount.

Fig. 10 is a flowchart showing a routine of the allowable oil temperature change process executed by the exhaust gas purification device according to embodiment 1.

Fig. 11 is a diagram showing the relationship between the regeneration amount of the GPF and the PM accumulation amount in the GPF for each air-fuel ratio.

Fig. 12 is a graph showing the relationship between the combustion variation and the amount of exhaust NOx with respect to the air-fuel ratio.

Fig. 13 is a time chart for explaining the difference in the change in the exhaust NOx amount and the GPF bed temperature at the execution timing of the lean air-fuel ratio control in embodiment 2.

Fig. 14 is a flowchart of a control routine executed in the exhaust gas purification apparatus according to embodiment 2.

Fig. 15 is a map defining the relationship of the target air-fuel ratio with respect to the engine water temperature.

Description of the reference numerals

8 ejector

10 engines

12 air intake passage

14 exhaust passage

16 air flow meter

18 throttle valve

22 Start converter (S/C)

24 GPF (gasoline particle filter)

26 automatic transmission

28 torque converter

29 lockup clutch

30 ECU (Electronic Control Unit)

32 speed sensor

34 water temperature sensor

36 oil temperature sensor

38 exhaust gas temperature sensor

40 air-fuel ratio sensor

100 exhaust gas purification device

310 deceleration fuel cut control unit

312 accumulation amount estimating unit

314 deceleration lock-up permissible oil temperature changing unit

316 air-fuel ratio control unit

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the embodiments shown below, when the number, the amount, the range, and the like of each element are mentioned, the present invention is not limited to the mentioned number except for the case where the number is specifically and explicitly shown or the case where the number is clearly specified in principle. In addition, the structures, steps, and the like described in the embodiments shown below are not necessarily essential to the present invention, except for the case where the structures, steps, and the like are specifically shown or clearly specified in principle.

1. Embodiment 1.

Embodiment 1 will be described with reference to the drawings.

1-1. Structure of embodiment 1

Fig. 1 is a diagram for explaining the structure of an exhaust gas purification device according to embodiment 1. As shown in fig. 1, an exhaust gas purification apparatus 100 of the present embodiment includes an internal combustion engine (engine) 10. Engine 10 is mounted on a vehicle as a power source. The engine 10 is a gasoline engine based on stoichiometric combustion. In the engine 10, 4 cylinders are arranged in series, and an injector 8 is provided for each cylinder. An intake manifold and an exhaust manifold (both not shown) are mounted on engine 10. An intake passage 12 for taking intake air into the engine 10 is connected to the intake manifold. An exhaust passage 14 for discharging exhaust gas discharged from the engine 10 to the atmosphere is connected to the exhaust manifold.

An air flow meter 16 for detecting the intake air amount is disposed in the middle of the intake passage 12. A throttle valve 18 is provided in the intake passage 12 on the intake downstream side of the airflow meter 16. A start-up converter (S/C)22 as a three-way catalyst is disposed in the exhaust passage 14. A GPF (gasoline particulate filter) 24 is disposed on the exhaust gas downstream side of the starter converter 22 in the exhaust passage 14. The GPF24 traps PM (particulate matter) discharged from the engine 10.

The crankshaft of the engine 10 is connected to an input shaft of an automatic transmission 26 via a torque converter 28. The torque converter 28 incorporates a lock-up clutch 29 for engaging the output shaft of the engine 10 and the input shaft of the automatic transmission 26 in a directly coupled state.

The exhaust gas purification device 100 according to the present embodiment includes an ecu (electronic Control unit) 30. The ECU30 is a control device that comprehensively controls the entire exhaust gas purification device, and the control device according to the present disclosure is embodied as one function of the ECU 30.

The ECU30 has at least an input/output interface, ROM, RAM, and CPU. The input/output interface takes in signals of sensors provided in the exhaust gas purification apparatus 100 and outputs operation signals to actuators provided in the engine 10. The sensors are installed at various places of the exhaust gas purification apparatus 100. An air-fuel ratio sensor 40 for detecting the air-fuel ratio a/F of the exhaust gas is provided in the exhaust passage 14 on the upstream side of the starter converter 22. An exhaust gas temperature sensor 38 for detecting the bed temperature of GPF24 is provided on the upstream side of GPF24 in the exhaust passage 14. A rotation speed sensor 32 that detects the engine rotation speed NE of the engine 10, a water temperature sensor 34 that detects the engine water temperature thw of the engine 10, an oil temperature sensor 36 that detects the temperature of lubricating oil (ATF) of the automatic transmission 26 (ATF oil temperature), and the like are also mounted. The ECU30 processes the signals of the sensors taken in and operates the actuators in accordance with a predetermined control program.

The actuators operated by the ECU30 include the injector 8, the throttle valve 18, the lock-up clutch 29 of the torque converter 28, and the like. The ROM stores various control data including various control programs and maps for controlling the engine 10. The CPU reads out the control program from the ROM, executes the control program, and generates an operation signal based on the acquired sensor signal. Although many actuators and sensors are connected to the ECU30 in addition to those shown in the drawings, the description thereof is omitted in this specification.

Fig. 2 is a diagram showing functional blocks of the ECU. The ECU30 includes a deceleration fuel cut control unit 310, a deposit amount estimation unit 312, a deceleration lock-up permitting oil temperature change unit 314, and an air-fuel ratio control unit 316 as functional blocks for controlling the exhaust gas purification apparatus 100. Hereinafter, the processing executed in each functional block will be described in detail.

1-2 basic operation of exhaust gas purification device according to embodiment 1

1-2-1 deceleration fuel cutoff control

The control of engine 10 performed by ECU30 of exhaust gas purification apparatus 100 includes deceleration fuel cut control. The deceleration fuel cut control is executed in deceleration fuel cut control portion 310 of ECU 30. In the deceleration fuel cut control of the present embodiment, when a predetermined execution condition is satisfied during deceleration of a vehicle in which the engine 10 is mounted, fuel injection from the injector 8 is stopped for the purpose of improving fuel economy.

However, during the deceleration fuel cut, the rotation speed of the output shaft of the engine 10 decreases, and therefore the engine 10 may stall. Therefore, the ECU30 controls the lock-up clutch 29 of the torque converter 28 to be in the engaged state during deceleration fuel cut. Thus, the output shaft of the engine 10 is forcibly rotated by the output shaft on the vehicle side during the deceleration fuel cut, and therefore, the engine 10 can be prevented from stalling.

The execution condition of the deceleration fuel cut includes that engagement of the lock-up clutch 29 can be achieved, in addition to that the vehicle is decelerating. Typically, the ECU30 permits engagement of the lockup clutch 29 when the ATF oil temperature, which is the oil temperature of the lubricating oil of the automatic transmission 26 during deceleration of the vehicle, is higher than a predetermined deceleration lockup permitting oil temperature, and prohibits engagement of the lockup clutch 29 when the ATF oil temperature is lower than the predetermined deceleration lockup permitting oil temperature. The deceleration lock-up permitting oil temperature is a determination value for determining permission and prohibition of engagement of the lock-up clutch 29. If the lock-up clutch 29 is engaged in an extremely cold environment, there is a possibility that deterioration of drivability due to the chattering phenomenon cannot be tolerated. Therefore, the deceleration lock-up permitting oil temperature is set to a lower limit temperature that is permitted, for example, from the viewpoint of drivability. Thereby, the stall of the engine 10 in the deceleration fuel cut is prevented, and the deterioration of the drivability due to the flutter phenomenon is prevented.

1-2-2. specific handling of deceleration fuel cut-off control

Next, a specific process of the deceleration fuel cut control executed in the exhaust gas purification apparatus 100 according to embodiment 1 will be described with reference to a flowchart. Fig. 3 is a flowchart showing a routine of deceleration fuel cut control executed in embodiment 1. Further, the routine shown in fig. 3 is repeatedly executed by the ECU30 at predetermined control cycles during operation of the engine 10.

In step S100 of the routine shown in fig. 3, it is determined whether or not the vehicle mounted with the engine 10 is decelerating. As a result, the process proceeds to step S102 when the vehicle is decelerating, and the routine is ended when the vehicle is not decelerating.

In step S102, it is determined whether the ATF oil temperature is higher than a predetermined deceleration lock-up permitting oil temperature. As a result, if the determination is not satisfied, the process proceeds to step S104, and the lock-up clutch 29 is maintained in the released state (lock-up release (OFF)). When the processing of step S104 is completed, the present routine is ended.

ON the other hand, when it is determined in step S102 that the determination is established, the process proceeds to step S106, and the lockup clutch 29 is brought into an engaged state (lockup ON). Upon completion of the process at step S106, the process proceeds to step S108. In step S108, a fuel cut is performed. Upon completion of the processing of step S108, the present routine is ended.

1-2-3 PM trapping and regeneration treatment by GPF

GPF24 traps PM contained in the exhaust gas discharged from engine 10. The trapped PM is accumulated in the GPF 24. In order to continue to trap PM in the GPF24, a regeneration process is required for removing PM deposited on the GPF24 and regenerating the trapping ability of the GPF 24. As such a regeneration process, a process of passively burning and removing trapped PM by placing GPF24 in a high-temperature lean atmosphere may be considered. In a gasoline engine based on stoichiometric combustion, the exhaust heat during normal operation can be used to raise the temperature of GPF24 to a temperature at which regeneration can be achieved. In addition, the lean atmosphere of GPF24 is typically realized during deceleration fuel cut of engine 10. That is, the regeneration process of GPF24 is passively performed in the deceleration fuel cut after the warm-up of GPF 24.

1-3. characteristic operation of exhaust gas purification device according to embodiment 1

1-3-1. overview of deceleration Lock-Up allowable oil temperature Change Process

Next, a deceleration lock-up allowable oil temperature changing process, which is a characteristic operation of the exhaust gas purification apparatus according to embodiment 1, will be described. The engine 10 discharges a large amount of PM during a period from the engine start until the cylinder wall surface and the like are warmed up. The PM emission amount tends to increase as the cylinder wall surface temperature decreases, and particularly tends to increase exponentially in an extremely cold environment in which the ambient temperature is 0 ℃ or lower.

In such an extremely cold environment, a situation is assumed in which the engine 10 repeats a short stroke. Since GPF24 is disposed in exhaust passage 14, it is warmed up to a bed temperature at which the regeneration process can be realized relatively early even at the time of cold start in an extremely cold environment. However, ATF lubricating the automatic transmission 26 tends to have a slower temperature rise than GPF 24. Therefore, in a situation where the engine 10 repeats a short stroke in an extremely cold environment, there is a possibility that the execution opportunity of the deceleration fuel cut cannot be sufficiently obtained without causing the ATF oil temperature to reach the deceleration lock allowable oil temperature. If the condition that the amount of PM collected in GPF24 is larger than the amount of PM subjected to regeneration processing continues, the amount of PM accumulation in GPF24 continues to increase. Excessive accumulation of PM in the GPF24 causes deterioration of combustion and deterioration of fuel economy with an increase in the exhaust pressure.

Therefore, the exhaust gas purification device 100 of the present embodiment is characterized by performing the allowable oil temperature changing process for changing the allowable temperature in accordance with the PM accumulation amount in the GPF 24. Typically, the deposit amount estimation unit 312 of the ECU30 estimates the amount of PM deposited on the GPF24 based on the operating state of the engine 10. Then, when the estimated PM accumulation amount, that is, the estimated accumulation amount is larger than the predetermined threshold value a, the deceleration lock-up allowable oil temperature changing unit 314 of the ECU30 changes the deceleration lock-up allowable oil temperature (determination value) during deceleration of the vehicle to a value lower than that during normal operation. The deceleration lock-up allowable oil temperature changing unit 314 is also referred to as a "determination value changing unit" because it changes the deceleration lock-up allowable oil temperature as the determination value. The threshold value a here is a value determined in advance through experiments or simulations as the PM accumulation amount that may cause deterioration of combustion of the engine 10. The threshold a is also referred to as a first amount of accumulation. According to such control, the opportunities for execution of deceleration fuel cut can be increased in an extremely cold environment, and therefore, reduction in the PM deposition amount by performing the regeneration process of GPF24 can be expected.

Fig. 4 is a timing chart for explaining a difference in the GPF regeneration performance depending on whether or not the deceleration lock-up allowable oil temperature changing process is executed. Fig. 4 (a) shows a time change in the bed temperature of GPF24, fig. 4 (b) shows a time change in the vehicle speed of the vehicle equipped with engine 10, fig. 4 (c) shows whether or not fuel cut is performed when the deceleration lock allowable oil temperature is not decreased, fig. 4 (d) shows a time change in the PM accumulation amount accumulated in GPF24 when the deceleration lock allowable oil temperature is not decreased, fig. 4 (e) shows a time change in the ATF oil temperature, fig. 4 (f) shows whether or not fuel cut is performed when the deceleration lock allowable oil temperature is decreased, and fig. 4 (g) shows a time change in the PM accumulation amount accumulated in GPF24 when the deceleration lock allowable oil temperature is decreased.

As shown in (e) in fig. 4, in the case where the permissible oil temperature changing process is not executed, the ATF oil temperature reaches the deceleration-lock permissible oil temperature at time t2, for example. In this case, as shown in (e) in fig. 4, the opportunity to execute the deceleration fuel cut is obtained after time t2, and therefore, the regeneration process of GPF24 is also performed after time t 2. As a result, as shown in fig. 4 (d), the PM accumulation amount continues to increase until time t2, and as a result, the execution opportunity of the regeneration process is lost.

In contrast, as shown in fig. 4 (e), when the deceleration lock-up permission oil temperature is decreased by the permission oil temperature changing process, the ATF oil temperature reaches the deceleration lock-up permission oil temperature at time t1 earlier than time t2, for example. In this case, as shown in (f) in fig. 4, the opportunity to execute the deceleration fuel cut is obtained after time t1, and therefore, the regeneration process of GPF24 is also performed after time t 1. As a result, as shown in fig. 4 (g), the PM accumulation amount is reduced from time t3, and the final PM accumulation amount is significantly reduced as compared with the PM accumulation amount shown in fig. 4 (d).

In this way, according to the allowable oil temperature changing process, the GPF24 regeneration process can be started early when the engine is started in an extremely cold environment. This can reduce the amount of PM deposited on GPF24, thereby preventing deterioration of combustion and fuel efficiency of engine 10.

1-3-2. specific processing of deceleration Lock-Up permissive oil temperature Change processing

In the GPF24, the collection of PM and the removal of PM by the regeneration process are performed simultaneously. The deposit amount estimating unit 312 of the ECU30 always calculates an estimated total deposit amount, which is an estimated value of the total deposit amount of PM deposited on the GPF24, during operation of the engine 10. First, before the description of the specific process of the deceleration lock-up allowable oil temperature changing process, the deposition amount estimating process in the GPF24 will be described.

1-3-3. estimating process of accumulation amount

Fig. 5 is a flowchart showing a control routine of the PM accumulation amount estimation process executed in the ECU 30. The control routine shown in fig. 5 is repeatedly executed at predetermined control cycles during the operation of the engine 10.

In step S120 of the control routine shown in fig. 5, the estimated deposition amount of PM newly deposited in GPF24 in the present control routine is calculated. Fig. 6 is a diagram showing an example of a PM discharge map in which an estimated accumulation amount with respect to the engine speed NE and the engine load KL is defined. Here, the estimated accumulation amount with respect to the current engine speed NE and engine load KL of engine 10 is calculated using the PM discharge map shown in fig. 6.

In the next step S122, the estimated accumulation amount calculated in the process of step S120 is corrected by the air-fuel ratio. Fig. 7 is a diagram showing an example of an air-fuel ratio correction map for calculating a correction coefficient with respect to an estimated accumulation amount of the air-fuel ratio. The leaner the air-fuel ratio of engine 10 is, the smaller the amount of PM discharged to exhaust passage 14 is. Therefore, the air-fuel ratio correction coefficient Kaf is calculated as a smaller value as the air-fuel ratio becomes leaner. Here, an air-fuel ratio correction coefficient Kaf corresponding to the current air-fuel ratio detected by the air-fuel ratio sensor 40 is calculated using the air-fuel ratio correction map shown in fig. 7. Then, the estimated accumulation amount calculated in the processing of step S120 is multiplied by the air-fuel ratio correction coefficient Kaf, thereby calculating the corrected estimated accumulation amount.

In the next step S124, the estimated accumulation amount calculated in the process of step S122 is further corrected by the engine water temperature. Fig. 8 is a diagram showing an example of a water temperature correction map for calculating a correction coefficient of an estimated accumulation amount with respect to the engine water temperature. The higher the engine water temperature thw of the engine 10 is, the smaller the amount of PM discharged to the exhaust passage 14 is. Therefore, the water temperature correction coefficient Kthw is calculated as a smaller value as the engine water temperature is higher. Here, a water temperature correction coefficient Kthw corresponding to the current engine water temperature thw detected by the water temperature sensor 34 is calculated using the water temperature correction map shown in fig. 8. Then, the estimated accumulation amount calculated in the processing of step S122 is multiplied by the water temperature correction coefficient Kthw, thereby calculating the corrected estimated accumulation amount.

In the next step S126, it is determined whether the GPF bed temperature of the GPF24 is greater than a predetermined bed temperature Trege. Here, the predetermined bed temperature Trege is a predetermined value as a lower limit value of the bed temperature for the regeneration process in the GPF 24. As a result, if it is not confirmed that the determination is established, the estimated regeneration amount, which is the estimated value of the regeneration amount in GPF24, is set to 0 (zero), and the process proceeds to step S130. On the other hand, if it is confirmed that the determination of step S126 is established, the process proceeds to step S128.

In step S128, the estimated regeneration amount in GPF24 is calculated. Fig. 9 is a diagram showing an example of a regeneration amount map for calculating an estimated regeneration amount. The larger the PM accumulation amount of GPF24, the larger the regeneration amount in GPF 24. Further, the higher the bed temperature of GPF24, the more regeneration in GPF 24. Further, the regeneration amount in GPF24 increases as the air-fuel ratio of the exhaust gas flowing into GPF24 becomes leaner. In the regeneration amount map shown in fig. 9, the regeneration amount of GPF24 is correlated with the PM accumulation amount of GPF24, the bed temperature of GPF24, and the air-fuel ratio of the exhaust gas. Here, the regeneration amount corresponding to the estimated total accumulation amount calculated in the previous routine and the bed temperature of GPF24 detected by exhaust gas temperature sensor 38 is calculated from the regeneration amount map as the estimated regeneration amount. Upon completion of the process at step S128, the process proceeds to next step S130.

In step S130, the final estimated accumulation amount in the present routine is calculated by subtracting the estimated regeneration amount calculated in step S128 from the estimated accumulation amount calculated in step S124. In the next step S132, the present value of the estimated total accumulation amount in GPF24 is calculated. Here, the present value of the estimated total deposition amount is calculated by adding the estimated deposition amount calculated in step S130 of the present routine to the previous value of the estimated total deposition amount calculated in the previous routine.

1-3-4 deceleration lockup allowed oil temperature change process

Next, the deceleration lock-up allowable oil temperature changing process will be described. The deceleration lock-up allowable oil temperature changing process is executed by the deceleration lock-up allowable oil temperature changing unit 314 of the ECU 30. Fig. 10 is a flowchart showing a routine of the allowable oil temperature change process executed by the exhaust gas purification device according to embodiment 1. The control routine shown in fig. 10 is repeatedly executed at predetermined control cycles during operation of the engine 10. In step S140 of the routine shown in fig. 10, it is determined that MODE is satisfied as 0. The deceleration lock-up permitting oil temperature is set to either the normal deceleration lock-up permitting oil temperature Toil _ norm or Toil _ Low lower than Toil _ norm. MODE here is a flag for determining the currently set deceleration lock-up permitting oil temperature. When MODE is 0, the deceleration lock-up allowable oil temperature is set to Toil _ norm, and when MODE is 1, the deceleration lock-up allowable oil temperature is set to Toil _ Low. As a result of the determination in step S140, when MODE is 0, the process proceeds to step S142.

In the next step S142, it is determined whether or not the estimated total accumulation amount estimated in the PM accumulation amount estimation process is larger than the threshold a. As a result, if the determination is not confirmed to be established, the process proceeds to step S154, and the deceleration lock-up allowable oil temperature is maintained at Toil _ norm.

On the other hand, if it is confirmed in step S142 that the determination is established, the process proceeds to step S144. In step S144, MODE is set to 1, and the process proceeds to the next step S146. In step S146, the deceleration lock-up permission oil temperature is set to Toil _ Low.

If it is not determined in step S140 that MODE is 0, the deceleration lock-up permission oil temperature is set to Toil _ Low. In this case, the process proceeds to step S150, and it is determined whether or not the estimated total deposit amount estimated in the PM deposit amount estimation process is larger than the threshold C. The threshold value C is a threshold value of the estimated total accumulation amount for preventing the set fluctuation (instability) of the deceleration lock-up allowable oil temperature, and is set to a value in the vicinity of the threshold value a. If it is confirmed that the determination is established here, the process proceeds to step S146, and the deceleration lock-up allowable oil temperature is maintained at Toil _ Low. On the other hand, in step S150, if the establishment of the determination is not confirmed, the process proceeds to step S152.

In step S152, MODE is set to 0, and the process proceeds to the next step S154. In step S154, the deceleration lock-up permission oil temperature is set to Toil _ norm.

In this way, according to the permissible oil temperature changing process executed in the exhaust gas purification device 100 according to embodiment 1, the deceleration lock-up permissible oil temperature is changed according to the estimated total accumulation amount of the GPF 24. Accordingly, at the time of engine start in an extremely cold environment, the opportunity of deceleration fuel cut can be obtained early, and therefore, the regeneration process of the GPF24 can be started from an early stage.

1-4 variation of the System of embodiment 1

The exhaust gas purification device 100 according to embodiment 1 may be modified as follows.

The specific method of the accumulation amount estimation process is not limited. That is, the estimated total PM accumulation amount in GPF24 may be calculated by another known method such as a method using a differential pressure between before and after GPF 24. This modification is similarly applicable to the exhaust gas purifying device according to embodiment 2 described later.

In the deceleration lock-up allowable oil temperature changing process, the deceleration lock-up allowable oil temperature may be changed in 3 stages or more based on the estimated total PM accumulation amount in the GPF 24. According to such a configuration, the setting of the deceleration lock-up permission oil temperature according to the PM accumulation amount of the GPF24 is further subdivided, and therefore both suppression of excessive accumulation of PM and optimization of drivability can be achieved.

The deceleration lock-up allowable oil temperature changing process is a process in which the lock-up allowable oil temperature during deceleration of the vehicle is a target of change, and is not a process including change of the lock-up allowable oil temperature other than during deceleration. Therefore, the setting of the lock-up allowable oil temperature other than during deceleration is not limited, but may be set to a fixed value (for example, Toil _ norm) independently of the PM accumulation amount, for example. In the state where the lock-up clutch 29 is released, the work required of the engine 10 is increased by an amount corresponding to a decrease in transmission efficiency as compared with the state where the lock-up clutch is engaged. Therefore, according to such a configuration, the engagement of the lock-up clutch 29 can be restricted so as not to permit deceleration other than during deceleration until the ATF oil temperature exceeds Toil _ norm. This can promote the increase in the exhaust gas temperature, and therefore contributes to early warm-up of GPF 24. This modification is similarly applicable to the exhaust gas purifying device according to embodiment 2 described later.

The determination of permission of lockup of the lockup clutch 29 is not limited to control using the ATF oil temperature, and other values having a correlation with the ATF oil temperature may be used. Examples of such a temperature-related value include an engine water temperature of the engine 10, an oil temperature of engine oil that lubricates the inside of the engine 10, and the like. This modification is similarly applicable to the exhaust gas purifying device according to embodiment 2 described later.

2. Embodiment 2.

Next, an exhaust gas purifying device according to embodiment 2 will be described.

2-1. Structure of exhaust gas purification device according to embodiment 2

The exhaust gas purification device according to embodiment 2 has the same configuration as the exhaust gas purification device 100 according to embodiment 1 shown in fig. 1. Therefore, a detailed description of the exhaust gas purification device according to embodiment 2 is omitted.

2-2 characteristics of exhaust gas purification device according to embodiment 2

In the exhaust gas purification device 100 according to embodiment 1, the opportunity of deceleration fuel cut is obtained in advance in an extremely cold environment, and thereby the regeneration process of the GPF24 is promoted in advance. In contrast, the exhaust gas purification device 100 according to embodiment 2 is characterized by lean air-fuel ratio control for changing the target air-fuel ratio to lean when there is a possibility that the deceleration fuel cut alone cannot cope with the target air-fuel ratio. The lean air-fuel ratio control is executed by the air-fuel ratio control portion 316 of the ECU 30.

Fig. 11 is a diagram showing the relationship between the regeneration amount of the GPF and the PM accumulation amount in the GPF for each air-fuel ratio. As shown in fig. 11, the regeneration amount of GPF24 tends to increase as the air-fuel ratio becomes leaner. Therefore, if the target air-fuel ratio is controlled to a lean air-fuel ratio, the regeneration efficiency of GPF24 can be improved.

However, the target air-fuel ratio in the lean air-fuel ratio control is not able to be controlled to lean without limitation. Fig. 12 is a graph showing the relationship between the combustion variation and the amount of exhaust NOx with respect to the air-fuel ratio. As shown in fig. 12, the exhaust NOx amount is at a maximum when the exhaust NOx amount is slightly lean (for example, a/F16), and then tends to decrease as the exhaust NOx amount becomes lean. Further, the combustion variation is suppressed low during the period from the stoichiometric ratio to the lean, but then tends to increase more rapidly as the lean becomes. Therefore, in the lean air-fuel ratio control, by controlling the air-fuel ratio to be lean within a range not exceeding the combustion variation limit specified for each engine water temperature, it is possible to reduce exhaust NOx and improve the regeneration efficiency of GPF 24.

It is preferable that the lean air-fuel ratio control be performed only during a period in which the intake air amount is small, such as during deceleration of the vehicle. Fig. 13 is a time chart for explaining the difference in the change in the exhaust NOx amount and the GPF bed temperature at the execution timing of the lean air-fuel ratio control in embodiment 2. Fig. 13 (a) shows a temporal change in the vehicle speed of the vehicle equipped with the engine 10, and fig. 13 (b) shows a temporal change in the intake air amount. As shown in (a) and (b) of fig. 13, the period from time t2 to time t3, the period from time t4 to time t5, and the period from time t6 to time t7 are deceleration periods during which the vehicle mainly decelerates, and are also periods during which the intake air amount is smaller than other periods. Fig. 13 (c) shows the time change of the GPF bed temperature when the lean control is limited to the deceleration period, and fig. 13 (d) shows the time change of the GPF bed temperature when the lean control is executed over the entire period. Further, (e) in fig. 13 shows the temporal change in the amount of exhaust NOx in the case where the lean air-fuel ratio control is limited only to this deceleration period, and (f) in fig. 13 shows the temporal change in the amount of exhaust NOx in the case where the lean air-fuel ratio control is executed over the entire period.

As shown in fig. 13, the period from time t1 to time t2 is a period during which the vehicle speed and the intake air amount increase during acceleration of the vehicle, and the period from time t2 to time t3 is a period during deceleration. In the example shown in (f) of the drawing, since the lean air-fuel ratio control is executed during the acceleration, the amount of exhaust NOx increases as the intake air amount increases. On the other hand, since the intake air amount is small during deceleration, the exhaust NOx is maintained small even if lean air-fuel ratio control is executed.

In contrast, in the example shown in (e) of the drawing, since the lean air-fuel ratio control is not executed during the acceleration, the exhaust NOx by the stoichiometric combustion is suppressed to be low. On the other hand, although the lean air-fuel ratio control is executed during deceleration, since the intake air amount is small, the exhaust NOx is maintained small.

In this way, when the lean air-fuel ratio control is limited to only the deceleration period, the increase in the amount of exhaust NOx can be effectively suppressed in both the acceleration period and the deceleration period. Further, as shown in (e) and (f) in the figure, during the deceleration period from time t2 to time t3, the intake air amount is small with respect to the heat capacity of GPF24, and therefore, even if lean control is performed, the decrease in the bed temperature of GPF24 can be suppressed to the minimum.

2-3 specific processing of control executed in the exhaust gas purification apparatus of embodiment 2

Fig. 14 is a flowchart of a control routine executed in the exhaust gas purification apparatus 100 according to embodiment 2. The control routine shown in fig. 14 is repeatedly executed by the ECU30 at predetermined control cycles during operation of the engine 10. In step S200 of the routine shown in fig. 14, it is determined that MODE is satisfied as 0. MODE here is a flag for determining whether or not deceleration lock-up allowable oil temperature and lean air-fuel ratio control currently set are executed. When MODE is 0, the deceleration lock-up allowable oil temperature is set to Toil _ norm, and the lean air-fuel ratio control is not executed. When MODE is 1, the deceleration lock-up permission oil temperature is set to Toil _ Low, and the lean air-fuel ratio control is not executed. When MODE is 2, the deceleration lock-up permission oil temperature is set to Toil _ Low, and lean air-fuel ratio control is executed. As a result of the determination in step S200, when MODE is 0, the process proceeds to step S202.

In the next step S202, it is determined whether or not the estimated total accumulation amount estimated in the PM accumulation amount estimation process is larger than the threshold a. As a result, if the determination is not confirmed to be established, the process proceeds to step S212, and the deceleration lock-up allowable oil temperature is maintained at Toil _ norm.

On the other hand, if it is confirmed in step S202 that the determination is established, the process proceeds to step S204. In step S204, MODE is set to 1, and the process proceeds to the next step S206.

In the case where MODE is not 0 in the determination of step S200, the deceleration lock-up permission oil temperature has been set to Toil _ Low. In this case, the process proceeds to step S210, and it is determined whether or not the estimated total deposit amount estimated in the PM deposit amount estimation process is larger than the threshold C. The processing here is the same as in step S150 of the control routine shown in fig. 10. As a result, when the determination is not confirmed to be established, it can be determined that the possibility of excessive PM accumulation in GPF24 is low. In this case, the process proceeds to step S212, the deceleration lock-up permission oil temperature is set to Toil _ norm, the target air-fuel ratio is set to stoichiometric in the next step S214, and MODE is set to 0 in the next step S216. Upon completion of the processing of step S216, the present routine is ended.

On the other hand, if it is confirmed in step S210 that the determination is established, the process proceeds to step S220. In step S220, it is determined that MODE is 1. As a result, if it is confirmed that the determination is established, the process proceeds to step S206. In step S206, it is determined whether or not the estimated total deposit amount estimated in the PM deposit amount estimation process is larger than a threshold B. Here, the threshold B is a value larger than the threshold a, and is also referred to as a second accumulation amount. As a result, when the estimated total accumulation amount is equal to or less than the threshold value B, the process proceeds to step S208, where the deceleration lock-up permitting oil temperature is set to Toil _ Low. When the processing of step S208 is completed, the present control routine is ended.

On the other hand, in the case where the estimated total accumulation amount is larger than the threshold value B in the determination of step S206, it can be determined that the deceleration fuel cut is not sufficiently obtained even if the deceleration lock-up allowable oil temperature changing process is executed. In this case, the process proceeds to step S230, where MODE is set to 2. Upon completion of the process of step S230, the process proceeds to the next step S232.

If it is not confirmed that MODE is 1 in step S220, it is determined that the current MODE is 2, and the process proceeds to step S232. In step S232, it is determined whether the lean FLAG (lean FLAG) is activated (ON). The lean flag here is a flag for determining whether or not the current target air-fuel ratio is set to a lean air-fuel ratio by lean air-fuel ratio control. As a result, if the lean flag is not activated (OFF), the process proceeds to step S234.

In step S234, it is determined whether the intake air amount Ga detected by the airflow meter 16 is larger than the predetermined low Ga value, that is, GALo. The GALo here is a determination air amount determined in advance through experiments or simulations as the intake air amount Ga that can suppress the exhaust NOx within an allowable range when the air-fuel ratio is controlled to be lean. As a result, when the intake air amount Ga is equal to or less than GALo, it is determined that the lean air-fuel ratio control can be executed, and the process proceeds to the next step S236.

In step S236, the lean flag is set to ON. In the next step S238, the target air-fuel ratio is controlled to be lean by the lean air-fuel ratio control. Fig. 15 is a map defining the relationship of the target air-fuel ratio with respect to the engine water temperature. In this map, a lean limit value that does not exceed the combustion variation limit is defined as a target air-fuel ratio for each engine water temperature. Typically, the target air-fuel ratio is defined such that the air-fuel ratio becomes leaner as the engine water temperature is higher. Here, according to the map shown in fig. 15, the target air-fuel ratio is set to a value of the target air-fuel ratio corresponding to the engine water temperature thw detected by the water temperature sensor 34. Upon completion of the process at step S238, the process proceeds to step S208, and the deceleration lock-up permitting oil temperature is set to Toil _ Low.

On the other hand, when the intake air amount Ga is larger than the GALo as the determination air amount in the determination of step S234, it is determined that the exhaust NOx cannot be suppressed within the allowable range in the operation based on the lean air-fuel ratio, and the process proceeds to the next step S240. In step S240, the lean flag is set to OFF. In the next step S242, the target air-fuel ratio is controlled to the stoichiometric air-fuel ratio. Upon completion of the process at step S242, the process proceeds to step S208, and the deceleration lock-up permitting oil temperature is set to Toil _ Low.

If the lean flag is ON in step S232, the process proceeds to step S244. In step S244, it is determined whether or not the intake air amount Ga detected by the airflow meter 16 is larger than GAHi, which is a predetermined high Ga value. GAHi here is a threshold value of the intake air amount for preventing the air-fuel ratio from being set to oscillate between the lean air-fuel ratio and the stoichiometric air-fuel ratio, and is set to a value in the vicinity of a value larger than GALo. As a result, when the intake air amount Ga is equal to or less than GAHi, the process proceeds to step S236 to turn ON the lean flag, and when the intake air amount Ga is larger than GAHi, the process proceeds to step S240 to turn OFF the lean flag.

As described above, according to the permissible oil temperature changing process including the air-fuel ratio control executed in the exhaust gas purification device 100 of embodiment 2, even when the opportunity of deceleration fuel cut cannot be sufficiently obtained in the permissible oil temperature changing process, the target air-fuel ratio can be controlled to be lean. This enables the GPF24 regeneration process to be started at an earlier stage.

2-4 variation of System of embodiment 2

The exhaust gas purification device 100 according to embodiment 2 may be modified as follows.

The setting of the target air-fuel ratio in the lean air-fuel ratio control is not limited to the method using the map of fig. 15. That is, the target air-fuel ratio in the lean air-fuel ratio control may be a fixed value of the lean air-fuel ratio.