JP2020133611A - Control device for internal combustion engine - Google Patents

Abstract

To provide a control device for an internal combustion engine enabling improvement of estimation accuracy of a temperature of an exhaust emission control member calculated during execution of automatic restart.SOLUTION: An internal combustion engine 10 includes a filter 18 provided in an exhaust passage 15, and automatic stop and automatic restart of the engine are performed. A control device 100 executes processing for estimating a temperature of the filter 18 by performing averaging processing. The control device 100 executes processing for correcting an averaging coefficient used for the averaging processing on the basis of execution time of the automatic stop and integrated intake amount that is an integrated value of suction air amount of the internal combustion engine after execution of the automatic restart.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device for an internal combustion engine.

For example, the internal combustion engine described in Patent Document 1 includes an exhaust purification member for purifying exhaust gas in an exhaust passage. In this internal combustion engine, the engine operation is automatically stopped when the automatic stop condition is satisfied, and the engine is automatically restarted when the automatic restart condition is satisfied. Then, in this internal combustion engine, the annealing process is performed when estimating the temperature of the exhaust gas purification member, and the annealing coefficient used for the annealing process is set according to the vehicle speed.

Japanese Unexamined Patent Publication No. 2015-183528

By the way, since the vehicle speed is "0" when the vehicle is not running at the time of executing the automatic restart, in the above-mentioned Patent Document 1, the smoothing process using the smoothing coefficient according to the vehicle speed is performed. I can't. Therefore, the estimation accuracy of the temperature of the exhaust gas purification member calculated at the time of executing the automatic restart may decrease.

The control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine in which an exhaust gas purifying member for purifying exhaust gas is provided in an exhaust passage and the engine is automatically stopped and restarted. This control device executes a process of estimating the temperature of the exhaust gas purification member by performing an annealing process. Then, this control device uses the smoothing coefficient used in the smoothing process based on the integrated intake air amount which is the integrated value of the intake air amount of the internal combustion engine after the execution time of the automatic stop and the execution of the automatic restart. Is executed.

When the automatic restart is executed, the accumulated gas in the exhaust passage whose temperature has dropped during the execution of the automatic stop flows into the exhaust purification member, and then the combustion gas generated by the restart of the engine flows into the exhaust purification member. .. Therefore, when the automatic restart is executed, the phenomenon that the actual temperature rise of the exhaust gas purification member temporarily stagnates occurs. Here, the time during which the actual temperature rise temporarily stagnates changes according to the execution time of the automatic stop and the integrated intake amount after the execution of the automatic restart. Therefore, in the same configuration, since the smoothing coefficient is corrected based on the execution time of such automatic stop and the integrated intake amount after the execution of the automatic restart, the exhaust gas purification member calculated at the time of the execution of the automatic restart The estimation accuracy of the temperature can be improved.

The schematic diagram which shows the structure in one Embodiment of the control device of an internal combustion engine. The flowchart which shows the procedure of the calculation process of the filter temperature executed by the control device of the same embodiment. The graph which shows the relationship between the intake air amount and the smoothing coefficient in the same embodiment. The graph which shows the relationship between the stop time counter and the integrated air amount and the correction value in the same embodiment. A timing chart showing the operation of the same embodiment.

Hereinafter, an embodiment of an internal combustion engine control device mounted on a vehicle will be described with reference to FIGS. 1 to 5.
As shown in FIG. 1, the internal combustion engine 10 includes a plurality of cylinders 10a, and an intake passage 13 is connected to an intake port of each cylinder 10a. The intake passage 13 is provided with a throttle valve 14 for adjusting the amount of intake air.

The internal combustion engine 10 is provided with a fuel injection valve 11 for supplying fuel into the cylinder 10a. In the combustion chamber of each cylinder 10a, a mixture of air sucked through the intake passage 13 and fuel injected from the fuel injection valve 11 is ignited by spark discharge to be burned. The exhaust (combustion gas) generated by the combustion of the air-fuel mixture in the combustion chamber is discharged to the exhaust passage 15 connected to the exhaust port of the internal combustion engine 10.

The exhaust passage 15 is provided with a three-way catalyst (hereinafter referred to as a catalyst) 17 which is an exhaust purification member for purifying exhaust gas. The catalyst 17 oxidizes and purifies hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas, and reduces and purifies nitrogen oxides (NOx) contained in the exhaust gas.

At a position downstream of the catalyst 17 in the exhaust passage 15, a filter 18 which is an exhaust purification member for purifying the exhaust gas and collects particulate matter (hereinafter referred to as PM) in the exhaust gas is provided.

The control device 100 of the internal combustion engine 10 includes a central processing unit (hereinafter referred to as a CPU) 110, a memory 120, and the like, and the CPU 110 executes a program stored in the memory 120 to control various types of the internal combustion engine 10. carry out.

Detection signals of various sensors are input to the control device 100. Examples of such sensors include a crank angle sensor 52 that detects the crank angle, which is the rotation angle of the crankshaft of the internal combustion engine 10, an air flow meter 53 that detects the intake air amount GA, and the temperature of the cooling water of the internal combustion engine 10. A water temperature sensor 54 for detecting a certain cooling water temperature THW is provided. Further, an intake air temperature sensor 55 for detecting the intake air temperature THA, which is the temperature of the air sucked into the internal combustion engine 10, is provided. Further, the accelerator position sensor 56 that detects the accelerator operation amount ACCP, which is the operation amount of the accelerator pedal, the brake sensor 57 that detects the brake operation amount BK, which is the operation amount of the brake pedal, and the vehicle speed SP, which is the traveling speed of the vehicle, are used. A vehicle speed sensor 58 for detecting is also provided.

The control device 100 calculates the engine rotation speed NE from the detection result of the crank angle by the crank angle sensor 52. Further, the control device 100 calculates the engine load factor KL based on the engine rotation speed NE and the intake air amount GA.

The control device 100 calculates the filter temperature TF, which is the estimated temperature of the filter 18, based on various engine operating conditions. Further, the control device 100 calculates the PM accumulation amount Ps, which is the accumulation amount of the particulate matter in the filter 18, based on the engine rotation speed NE, the engine load factor KL, the filter temperature TF, and the like. Here, when the temperature of the filter 18 becomes equal to or higher than the specified combustion temperature THB, the particulate matter deposited on the filter 18 burns and decreases. Therefore, when the filter temperature TF is equal to or higher than the combustion temperature THB when calculating the PM accumulation amount Ps, the control device 100 executes a subtraction process of the PM accumulation amount Ps by burning the particulate matter. ..

As one of various controls of the internal combustion engine 10, the control device 100 automatically stops or restarts the internal combustion engine 10 when a predetermined automatic stop condition or automatic restart condition is satisfied, that is, so-called idle stop control. To execute. In the present embodiment, as the automatic stop condition, for example, a condition that the accelerator operation amount ACCP is "0" and the vehicle speed SP is equal to or less than the reference speed SPk (SPk> 0) is set. As a result, when the vehicle is at a reference speed SPk or less without the accelerator pedal being depressed, for example, when the vehicle is decelerating or the vehicle is stopped, fuel injection from the fuel injection valve 11 and ignition of the air-fuel mixture are stopped. The internal combustion engine 10 is automatically stopped. Further, as the automatic restart condition, for example, the accelerator operation amount ACCP becomes a specified value or more during the automatic stop, the brake operation amount BK decreases during the automatic stop, and the like are set. As a result, when the accelerator pedal is depressed during automatic stop, or when the depression of the brake pedal is weakened, internal combustion is started by starting cranking, fuel injection from the fuel injection valve 11, and ignition of the air-fuel mixture. The engine 10 is automatically restarted.

By the way, when the automatic restart is executed, the accumulated gas in the exhaust passage 15 whose temperature has dropped during the execution of the automatic stop flows into the filter 18, and then the combustion gas generated by the automatic restart flows into the filter 18. Become. Therefore, when the automatic restart is executed, the phenomenon that the actual temperature rise of the filter 18 temporarily stagnates occurs. Therefore, in the present embodiment, the filter temperature TF, which is the estimated temperature of the filter 18, is calculated in consideration of such a temporary stagnation of the temperature rise.

Next, with reference to FIGS. 2 to 4, the procedure of the filter temperature TF calculation process executed by the control device 100 is shown. The calculation process shown in FIG. 2 is realized by the CPU 110 repeatedly executing the program stored in the memory 120 of the control device 100 at predetermined cycles. Further, in the following, the step number is represented by a number with "S" added at the beginning.

As shown in FIG. 2, when this process is started, the control device 100 first acquires the simulated temperature TFM, the intake air amount GA, the integrated intake air amount SGA, and the stop time counter CS (S100).
The simulated temperature TFM is the temperature of the filter 18 calculated by the control device 100 with reference to a map or the like based on the engine operating state such as the engine load factor KL and the engine rotation speed NE.

The integrated intake air amount SGA is an integrated value of the intake air amount GA of the internal combustion engine 10 after the execution of the above-mentioned automatic restart. The control device 100 resets the integrated intake amount SGA to "0" at the timing when the automatic restart is executed. Then, during the engine operation, the integrated intake air amount SGA is updated by accumulating the intake air amount GA. During the execution of the automatic stop, the value of the integrated intake amount SGA is held at the value immediately before the start of the automatic stop.

The stop time counter CS is a value obtained by measuring the execution time of the automatic stop before the automatic restart is executed. The control device 100 resets the stop time counter CS to "0" at the timing when the automatic stop is executed. Then, during the automatic stop, the stop time counter CS is updated by increasing the stop time counter CS by a constant value. During engine operation, the value of the stop time counter CS is held at the value immediately before the start of automatic restart.

Next, the control device 100 calculates the annealing coefficient N used for the annealing process of the simulated temperature TFM based on the acquired intake air amount GA (S110).
As shown in FIG. 3, the smoothing coefficient N is variably set so that the value of the smoothing coefficient N becomes smaller as the intake air amount GA is larger. In this embodiment, as an example, the value of the smoothing coefficient N is 1 or more. Further, as can be seen from the equation (1) described later, the larger the annealing coefficient N is, the more the change in the filter temperature TF, which is the value after the simulated temperature TFM is annealed, with respect to the change in the simulated temperature TFM. Become gradual. By the way, the reason why the value of the smoothing coefficient N becomes smaller as the intake air amount GA increases in this way is that the actual temperature rise of the filter 18 becomes faster as the intake air amount GA increases, so that the intake air amount GA increases. This is because the delay time when the filter temperature TF follows the change of the simulated temperature TFM is shortened.

Next, the control device 100 calculates a correction value H for correcting the smoothing coefficient N based on the acquired integrated intake amount SGA and the stop time counter CS (S120). In the present embodiment, as an example, the value of the correction value H is a value of 1 or more, and the larger the value of the correction value H, the larger the value of the smoothing coefficient N after the correction as compared with the value before the correction. Is corrected to. For example, in the present embodiment, the smoothing coefficient N is corrected by multiplying the smoothing coefficient N by the correction value H.

As shown in FIG. 4, the correction value H is variably set so that the value of the correction value H becomes larger as the integrated intake amount SGA is smaller. When the integrated intake amount SGA becomes equal to or higher than a predetermined value, the value of the correction value H is set to "1" regardless of the value of the stop time counter CS. When the value of the correction value H is set to "1" in this way, the smoothing coefficient N before correction and the smoothing coefficient N after correction become the same, and the smoothing coefficient N is substantially the same. The correction of N is not performed.

Further, the correction value H is variably set so that the value of the correction value H becomes larger as the value of the stop time counter CS becomes larger. When the stop time counter CS is "0", the value of the correction value H is set to "1" regardless of the value of the integrated intake amount SGA. When the value of the correction value H is set to "1" in this way, the correction of the smoothing coefficient N is substantially not performed as described above.

The reason for variably setting the correction value H in this way is as follows. That is, the smaller the integrated intake amount SGA, the longer the time until the combustion gas reaches the filter 18 at the time of executing the automatic restart, and the slower the actual temperature rise of the filter 18. Therefore, the correction value H is increased as the integrated intake amount SGA is smaller so that the change in the calculated filter temperature TF becomes slower as the integrated intake amount SGA is smaller.

Further, the larger the stop time counter CS is, the longer the execution time of the automatic stop is. As a result, the temperature of the stagnant gas in the exhaust passage 15 that is lowered during the execution of the automatic stop has a larger temperature reduction allowance. There is. Therefore, when the automatic restart is executed, the actual temperature rise of the filter 18 becomes slow due to the inflow of such low-temperature retained gas into the filter 18. Therefore, the correction value H is increased as the stop time counter CS is larger so that the calculated filter temperature TF changes more slowly as the stop time counter CS is larger.

Next, the control device 100 calculates the filter temperature TF by annealing the acquired simulated temperature TFM based on the following equation (1) (S130), and temporarily terminates this process.
TF = previous value of TF + (previous value of TFM-TF) / (N × H)… (1)
TF: Filter temperature TFM: Simulated temperature N: Annealing coefficient H: Correction value The operation of this embodiment will be described with reference to FIG.

When the automatic stop is executed at the time t1, the stop time counter CS is reset and then gradually increased. Further, when the automatic stop is executed, the combustion gas does not flow into the filter 18, so that the actual temperature TFr, which is the actual temperature of the filter 18, gradually decreases as shown by the solid line L3.

When the automatic restart is executed at time t2, the integrated intake amount SGA is reset. Further, the stop time counter CS is held at the value immediately before the start of automatic restart.
Then, after time t2, the correction value H is calculated based on the stop time counter CS held at the value immediately before the start of the automatic restart and the cumulative intake amount SGA that gradually increases. Therefore, the correction value H, which was set to, for example, “1” before the time t2, suddenly becomes a large value at the time t2, and gradually decreases as the integrated intake amount SGA increases after the time t2.

In accordance with the transition of the correction value H, after the time t2, the smoothing coefficient N (shown by the solid line L1) after the correction corrected by the correction value H is the smoothing coefficient N (two-dot chain line L2) before the correction. (Shown in). That is, the corrected smoothing coefficient N suddenly becomes a large value at the time t2 when the automatic restart is executed, and gradually decreases as the correction value H decreases after the time t2.

Further, when the automatic restart is executed at time t2, the accumulated gas in the exhaust passage 15 whose temperature has dropped during the execution of the automatic stop flows into the filter 18, so that the actual temperature TFr (solid line L3) of the filter 18 is temporarily set. descend. Then, when the combustion gas generated by the restart of the engine operation by the automatic restart starts to flow into the filter 18, the actual temperature TFr of the filter 18 starts to rise. As described above, when the automatic restart is executed, a stagnation phenomenon occurs in which the increase in the actual temperature TFr of the filter 18 is temporarily delayed.

Then, when the actual temperature TFr of the filter 18 becomes equal to or higher than the combustion temperature THB (after time t5), the particulate matter deposited on the filter 18 burns, so that the amount of the particulate matter deposited on the filter 18 decreases. ..

Further, when the engine operation is started by executing the automatic restart at time t2, the above simulated temperature TFM (shown by the alternate long and short dash line L4) is calculated based on the engine rotation speed NE, the engine load factor KL, and the like. Is done.

Here, as shown by the alternate long and short dash line L2, when the smoothing coefficient N is not corrected by the correction value H, the smoothing coefficient N is corrected by the correction value H as shown by the solid line L1. The value of the smoothing coefficient N is smaller than that in the case of correction. Therefore, if the simulated temperature TFM is annealed with the uncorrected annealing coefficient N to calculate the filter temperature TF, as shown by the alternate long and short dash line L5, the automatic restart is executed. The rate of increase in the filter temperature TF increases. Therefore, in this case, the filter temperature TF rises faster even though the actual temperature TFr rises slower because the stagnation phenomenon occurs when the automatic restart is executed. The discrepancy between the temperature TF and the actual temperature TFr becomes remarkable, and the estimation accuracy of the filter temperature TF deteriorates.

Further, when the rate of increase of the filter temperature TF increases as described above, the timing at which the filter temperature TF reaches the combustion temperature THB (time t3) is earlier than the timing at which the actual temperature TFr reaches the combustion temperature THB (time t5). turn into. Therefore, even though the filter 18 is not actually above the combustion temperature THB, the control device 100 executes the subtraction process of the PM accumulation amount Ps by burning the particulate matter at an earlier timing, and the PM The estimation accuracy of the deposited amount Ps may deteriorate.

On the other hand, as shown by the solid line L1, in the case of the present embodiment in which the smoothing coefficient N is corrected by the correction value H, the value of the smoothing coefficient N becomes large when the automatic restart is executed. Therefore, as shown by the alternate long and short dash line L6, the rate of increase in the filter temperature TF after the automatic restart is executed becomes slow. Therefore, in the case of the present embodiment, as compared with the case of using the uncorrected smoothing coefficient N, the deviation between the filter temperature TF and the actual temperature TFr when the automatic restart is executed is suppressed, and the filter temperature is suppressed. The estimation accuracy of TF is improved.

Further, since the rate of increase of the filter temperature TF becomes slow in this way, in the present embodiment, the timing (time t4) at which the filter temperature TF reaches the combustion temperature THB is the case where the uncorrected annealing coefficient N is used. It becomes later than the timing (time t3) and approaches the timing (time t5) when the actual temperature TFr reaches the combustion temperature THB. Therefore, the timing at which the control device 100 executes the subtraction process of the PM accumulation amount Ps by burning the particulate matter is a more appropriate timing as compared with the case where the uncorrected smoothing coefficient N is used, and the PM accumulation amount Ps The estimation accuracy of is improved.

Next, the effect of this embodiment will be described.
(1) When the automatic restart is executed, a phenomenon occurs in which the actual temperature rise of the filter 18 temporarily stagnates. Here, the stagnation time at which such an actual temperature rise temporarily stagnates changes according to the value of the stop time counter CS indicating the execution time of the automatic stop and the integrated intake amount SGA after the execution of the automatic restart. .. That is, as described above, the larger the stop time counter CS, the slower the actual temperature rise of the filter 18 at the time of executing the automatic restart, and the longer the stagnation time. Further, the smaller the integrated intake amount SGA, the slower the actual temperature rise of the filter 18 at the time of executing the automatic restart, and the longer the stagnation time.

Therefore, in the present embodiment, the smoothing coefficient N used for the smoothing process is corrected based on the stop time counter CS and the integrated intake amount SGA. More specifically, the correction value H is calculated so that the larger the stop time counter CS is, the larger the value of the annealing coefficient N is, so that the rate of increase of the annealed filter temperature TF becomes slower. There is. Further, the correction value H is calculated so that the larger the integrated intake amount SGA is, the larger the value of the annealing coefficient N is, so that the rate of increase of the annealed filter temperature TF is slowed down. In this way, when the automatic restart is executed, the actual temperature rise of the filter 18 is slowed down, and the rise rate of the annealed filter temperature TF is also slowed down. Therefore, the automatic restart is executed. The estimation accuracy of the filter temperature TF calculated at times can be improved.

(2) The timing at which the filter temperature TF reaches the combustion temperature THB is later than the timing when the uncorrected smoothing coefficient N is used, and the actual temperature TFr approaches the timing at which the combustion temperature THB is reached. Therefore, the accuracy of estimating the PM deposition amount Ps is improved.

The above embodiment can be modified and implemented as follows. The above-described embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

-The following values may be used instead of the stop time counter CS. That is, when the automatic restart is executed, the water temperature difference ΔTHW, which is a value obtained by subtracting the cooling water temperature THW when the automatic restart is started from the cooling water temperature THW when the automatic stop is started, is calculated. Then, the correction value H may be variably set so that the value of the correction value H becomes larger as the water temperature difference ΔTHW becomes larger. Even in this case, the same action and effect as those of the above embodiment can be obtained.

-The internal combustion engine 10 may be not only an internal combustion engine mounted on a vehicle having only an internal combustion engine as a prime mover, but also an internal combustion engine mounted on a hybrid vehicle having an internal combustion engine and a motor as a prime mover. Even in such a hybrid vehicle, since the internal combustion engine is automatically stopped and automatically restarted while the vehicle is running, the same effect can be obtained by executing the above-mentioned filter temperature TF calculation process.

-The estimated temperature of the exhaust purification member other than the filter 18 provided in the exhaust passage, for example, the three-way catalyst 17, may be calculated in the same manner as the filter temperature TF.
The control device 100 includes a CPU 110 and a memory 120, and is not limited to the one that executes software processing. For example, a dedicated hardware circuit (for example, ASIC or the like) that processes at least a part of the software processing executed in each of the above embodiments may be provided. That is, the control device 100 may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processing according to a program and a program storage device such as a memory for storing the program are provided. (B) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing are provided. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, there may be a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the above processing may be executed by a processing circuit including at least one of one or a plurality of software processing circuits and one or a plurality of dedicated hardware circuits.

10 ... Internal combustion engine, 10a ... Cylinder, 11 ... Fuel injection valve, 13 ... Intake passage, 14 ... Throttle valve, 15 ... Exhaust passage, 17 ... Three-way catalyst (exhaust purification member), 18 ... Filter (exhaust purification member), 52 ... Crank angle sensor, 53 ... Air flow meter, 54 ... Water temperature sensor, 55 ... Intake temperature sensor, 56 ... Accelerator position sensor, 57 ... Brake sensor, 58 ... Vehicle speed sensor, 100 ... Control device, 110 ... Central processing device (CPU) ), 120 ... Memory.

Claims (1)

A process that is applied to an internal combustion engine that is equipped with an exhaust purification member that purifies the exhaust in the exhaust passage and that automatically stops and restarts the engine, and estimates the temperature of the exhaust purification member by annealing. Is a control device that executes
The process of correcting the smoothing coefficient used in the smoothing process is executed based on the integrated intake air amount which is the integrated value of the intake air amount of the internal combustion engine after the execution time of the automatic stop and the execution of the automatic restart. Control device for internal combustion engine.