Engine control unit

Abstract

This design suppresses the reduction in the heating effect of the exhaust gas purification catalyst while also suppressing changes in engine output caused by adjusting the ignition timing retardation amount. [Solution] The engine control device 30 performs a catalyst heating process to raise the temperature of the exhaust gas purification catalyst 17 by retarding the ignition timing, a retardation amount adjustment process that adjusts according to the combustion state of the engine 10, and a multi-injection process that divides fuel injection into intake stroke injection and compression stroke injection and performs fuel injection by the in-cylinder injection valve 19. Furthermore, during the catalyst heating process, the engine control device 30 performs an injection ratio adjustment process that adjusts the ratio of fuel injection amounts for intake stroke injection and compression stroke injection according to the change in output of the engine 10 due to the adjustment of the ignition timing retardation amount in the retardation amount adjustment process.

Description

Technical Field

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[0001] The present invention relates to an engine control device.

Background Art

[0002] Patent Document 1 describes an engine control device that performs a catalyst temperature increase promotion process for promoting the temperature increase of an exhaust purification catalyst installed in an exhaust passage by delaying the ignition timing of an engine. This engine control device reduces the amount of ignition timing retard when the engine speed decreases during the catalyst temperature increase promotion process.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the amount of ignition timing retard is decreased, combustion is improved and engine output increases. If it is desired to maintain the engine output, it is necessary to decrease the engine load ratio together with the ignition timing retard. However, when the engine load ratio is decreased, the effect of promoting the temperature increase of the exhaust purification catalyst decreases in combination with the decrease in the amount of ignition timing retard.

Means for Solving the Problems

[0005] An engine control device that solves the above problems is an engine control device applied to an engine comprising an in-cylinder injection valve for injecting fuel into a combustion chamber and an exhaust gas purification catalyst installed in the exhaust passage, and is configured to perform: a catalyst heating process for heating the exhaust gas purification catalyst by retarding the ignition timing of the engine; a retardation amount adjustment process for adjusting the amount of retardation of the ignition timing according to the combustion state of the engine during the catalyst heating process; a multi-injection process for performing fuel injection from the in-cylinder injection valve divided into intake stroke injection and compression stroke injection during the catalyst heating process; and an injection ratio adjustment process for adjusting the ratio of the fuel injection amounts of the intake stroke injection and the compression stroke injection in the multi-injection process according to the change in engine output accompanying the adjustment of the retardation amount in the retardation amount adjustment process. [Effects of the Invention]

[0006] The above-mentioned engine control device has the effect of suppressing changes in engine output caused by adjusting the ignition timing retardation amount while maintaining the temperature-raising effect of the exhaust gas purification catalyst. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing the configuration of one embodiment of an engine control device. [Figure 2] Figure 2 is a flowchart of the injection ratio adjustment routine executed by the engine control unit shown in Figure 1. [Figure 3] Figure 3 is a graph showing the relationship between the intake stroke injection ratio and engine output. [Figure 4] Figure 4 is a flowchart of the injection ratio adjustment routine performed by another embodiment of the engine control device. [Modes for carrying out the invention]

[0008] Hereinafter, one embodiment of the engine control device will be described in detail with reference to Figures 1 to 3. <Configuration of the engine control device 30> First, with reference to Figure 1, the configuration of the engine 10 to which the engine control device 30 of this embodiment is applied will be described. The engine 10 is mounted in a vehicle. The engine 10 includes a combustion chamber 11 for burning the air-fuel mixture, an intake passage 12 which is the path for introducing intake air into the combustion chamber 11, and an exhaust passage 13 which is the path for discharging exhaust gas from the combustion chamber 11. The intake passage 12 is equipped with an airflow meter 14 for detecting the amount of intake air to the engine 10, and a throttle valve 15 for adjusting the intake air flow rate by changing the flow area of ​​the intake air passage. The exhaust passage 13 is equipped with an exhaust gas purification catalyst 17. The engine 10 also includes an in-cylinder injection valve 19 for injecting fuel into the combustion chamber 11, and an ignition device 20 for igniting the air-fuel mixture in the combustion chamber 11 by spark discharge.

[0009] Next, with reference to Figure 1, the configuration of the engine control device 30 of this embodiment will be described. The engine control device 30 is configured as an electronic control unit comprising a processing unit 31 and a storage device 32. The storage device 32 stores control programs and data. The engine control device 30 is configured to perform various processes for controlling the engine 10 by having the processing unit 31 execute the programs stored in the storage device 32. In addition to the airflow meter 14 described above, the engine control device 30 receives detection signals from various sensors for detecting the operating status of the engine 10, such as a crank angle sensor 22, an accelerator pedal sensor 33, and a vehicle speed sensor 34. The crank angle sensor 22 is a sensor that detects the crank angle. The crank angle represents the rotation angle of the crankshaft 21, which is the output shaft of the engine 10. The accelerator pedal sensor 33 is a sensor that detects the accelerator pedal opening. The accelerator pedal opening represents the amount of operation of the accelerator pedal of the vehicle on which the engine 10 is installed. The vehicle speed sensor 34 is a sensor that detects the vehicle speed. Vehicle speed represents the driving speed of the vehicle equipped with engine 10. The engine control device 30 calculates the engine rotational speed based on the crank angle. The engine control device 30 also calculates the engine load ratio based on the engine rotational speed, intake air volume, etc. The engine load ratio represents the intake air filling rate of the combustion chamber 11.

[0010] The engine control device 30 calculates the control amount for the engine 10 based on the detection results of each sensor. The control amount for the engine 10 includes the throttle opening, which is the opening ratio of the throttle valve 15; the fuel injection amount and timing of the in-cylinder injector 19; and the ignition timing of the air-fuel mixture by the ignition device 20. The engine control device 30 then controls the engine 10 by operating the actuators of the engine 10, such as the throttle valve 15, the in-cylinder injector 19, and the ignition device 20, according to the calculated control amount.

[0011] <Catalytic converter warm-up acceleration control> The engine control device 30 performs catalyst warm-up acceleration control to accelerate the warm-up of the exhaust gas purification catalyst 17 when the engine 10 is running cold. In catalyst warm-up acceleration control, the engine control device 30 performs a catalyst heating process to raise the temperature of the exhaust gas purification catalyst 17 by retarding the ignition timing of the engine 10. Furthermore, in catalyst warm-up acceleration control, the engine control device 30 performs a retardation amount adjustment process to adjust the amount of retardation of the ignition timing according to the combustion state of the engine 10 during the catalyst heating process. When the ignition timing of the engine 10 is retarded during the catalyst heating process, the temperature of the exhaust gas flowing into the exhaust gas purification catalyst 17 increases, thus accelerating the warm-up of the exhaust gas purification catalyst 17. However, if the ignition timing is retarded too much, combustion will deteriorate. In response to this, the engine control device 30 suppresses the deterioration of combustion by adjusting the amount of retardation of the ignition timing according to the combustion state of the engine 10 in the retardation amount adjustment process. Specifically, in the ignition timing retardation adjustment process, the engine control device 30 reduces the ignition timing retardation amount when it detects a deterioration in the combustion state due to an increase in the amount of fluctuation in engine rotational speed, etc., during the catalyst heating process. In the following explanation, the catalyst heating process performed in the catalyst warm-up acceleration control during cold operation of the engine 10 will be referred to as the cold-start catalyst heating process.

[0012] <Multi-injection treatment> The engine control device 30 performs multi-injection processing during engine 10 operation, dividing the fuel injection into intake stroke injection and compression stroke injection, and injecting fuel into the combustion chamber 11 by the in-cylinder injection valve 19. In engine 10, divided injection by multi-injection processing is also performed during the cold catalyst heating process. When performing multi-injection processing, the engine control device 30 determines the ratio of fuel injection amounts for intake stroke injection and compression stroke injection based on the engine rotational speed, engine load ratio, etc.

[0013] <Injection ratio adjustment process> During the cold-start catalyst heating process, the engine control device 30 performs an injection ratio adjustment process to adjust the ratio of fuel injection amounts for intake stroke injection and compression stroke injection in the multi-injection control. In the following explanation, the ratio of fuel injection amounts for intake stroke injection will be referred to as the intake stroke injection ratio, and the ratio of fuel injection amounts for compression stroke injection will be referred to as the compression stroke injection ratio.

[0014] Figure 2 shows a flowchart of the injection ratio adjustment routine executed by the engine control device 30 for injection ratio adjustment processing performed during the cold catalyst heating process. The engine control device 30 repeatedly executes this routine at predetermined control cycles while the engine 10 is running.

[0015] When this routine is started, the engine control device 30 first determines in step S100 whether or not the cold catalyst heating process is currently being performed. If the engine control device 30 determines that the cold catalyst heating process is not being performed (NO), it terminates the processing of this routine for the current control cycle. On the other hand, if the engine control device 30 determines that the cold catalyst heating process is being performed (YES), it proceeds to step S110.

[0016] In step S110, the engine control device 30 determines whether the actual output is equal to the target output. If the engine control device 30 determines that the actual output is equal to the target output (YES), it terminates the processing of this routine for the current control cycle. If the engine control device 30 determines that the actual output is not equal to the target output (NO), it proceeds to step S120. Actual output represents the actual value of the engine output, and target output represents the target value of the engine output. The engine control device 30 estimates the actual output based on the engine load ratio, engine rotational speed, etc. The engine control device 30 also sets the target output as the engine output necessary to meet the driver's driving request based on the amount of accelerator pedal operation, vehicle speed, etc.

[0017] In step S120, the engine control device 30 determines whether the actual output is less than the target output. If the engine control device 30 determines that the actual output is less than the target output (YES), it proceeds to step S130. In step S130, the engine control device 30 decreases the intake stroke injection ratio. On the other hand, if the engine control device 30 determines that the actual output is not less than the target output (NO), that is, if the actual output is greater than the target output, it proceeds to step S140. In step S140, the engine control device 30 increases the intake stroke injection ratio. After processing in step S130 or step S140, the engine control device 30 terminates the processing of this routine for the current control cycle. Note that the increase or decrease in the intake stroke injection ratio in steps S130 and S140 may be determined, for example, by determining the amount of increase or decrease in the intake stroke injection ratio based on the difference between the actual output and the target output, such that the larger the difference, the larger the value. Alternatively, the intake stroke injection ratio may be increased or decreased in steps S130 and S140 in such a manner that the intake stroke injection ratio is decreased or increased by a fixed amount while the actual output remains lower or higher than the target output.

[0018] <Effect of the Embodiment> In the catalyst warm-up promotion control, the engine control device 30 performs a cold-time catalyst temperature increase process for raising the temperature of the exhaust purification catalyst 17 by retardating the ignition timing of the engine 10. In addition to this, in the catalyst warm-up promotion control, the engine control device 30 performs a retard angle amount adjustment process for adjusting the retard angle amount of the ignition timing according to the combustion state of the engine 10 during the cold-time catalyst temperature increase process. Further, during the cold-time catalyst temperature increase process, the engine control device 30 performs a multi-injection process for performing fuel injection of the in-cylinder injection valve 19 by dividing it into intake stroke injection and compression stroke injection.

[0019] When the combustion is improved by reducing the retard angle amount of the ignition timing by the retard angle amount adjustment process, the engine output increases. In contrast, the engine control device 30 of the present embodiment compensates for the change in the engine output due to the adjustment of the ignition timing retard angle amount by adjusting the intake stroke injection ratio and the compression stroke injection ratio by the injection ratio adjustment process.

[0020] Fig. 3 shows the relationship between the intake stroke injection ratio and the engine output. The relationship between the intake stroke injection ratio and the engine output changes between the cold operation and the warm operation of the engine 10. In Fig. 3, the relationship between the intake stroke injection ratio and the engine output during the cold operation of the engine 10 is shown using a solid line. Also, in Fig. 3, the relationship between the intake stroke injection ratio and the engine output during the warm operation of the engine 10 is shown using a two-dot chain line.

[0021] During cold operation of the engine 10, the wall temperature of the combustion chamber 11 is low, making it difficult for the fuel injected by the in-cylinder injector 19 to vaporize. The fuel that does not vaporize after injection adheres to the wall of the combustion chamber 11. The fuel adhering to the wall of the combustion chamber 11 contributes very little to combustion within the combustion chamber 11. Incidentally, in controlling the fuel injection of the engine 10, the engine control device 30 predicts the amount of fuel that will adhere to the wall of the combustion chamber 11 and corrects the amount of fuel injected by the in-cylinder injector 19 by increasing it accordingly. During the compression stroke, the intake air in the combustion chamber 11 is compressed and its temperature rises, so the temperature inside the combustion chamber 11 is higher during the compression stroke than during the intake stroke. Therefore, during cold operation of the engine 10, a larger proportion of the fuel injected during the compression stroke vaporizes and contributes to combustion than the fuel injected during the intake stroke. Therefore, even if the total amount of fuel injected is the same, a higher intake stroke injection ratio results in greater engine output from combustion than a lower intake stroke injection ratio.

[0022] In contrast, in this embodiment, the engine control device 30 reduces the intake stroke injection ratio when the actual output of the engine 10 falls below the target output during the cold catalyst heating process. This increases the compression stroke injection ratio, which in turn increases the amount of fuel contributing to combustion, thus increasing engine output. On the other hand, in this embodiment, the engine control device 30 increases the injection stroke injection ratio when the actual output of the engine 10 falls above the target output during the cold catalyst heating process. This decreases the compression stroke injection ratio, which in turn reduces the amount of fuel contributing to combustion, thus increasing engine output. Therefore, the increase in engine output due to the reduction in ignition timing retardation in response to combustion deterioration during the cold catalyst heating process is offset by the decrease in engine output due to the increase in the intake stroke injection ratio. Unlike the case where engine output is reduced by a decrease in engine load, the total amount of fuel injected by the in-cylinder injector 19 does not change even if the intake stroke injection ratio changes. Fuel that does not burn in the combustion chamber 11 is discharged into the exhaust passage 13 along with the exhaust. The unburned fuel in the exhaust then burns in the exhaust. Therefore, even if the engine output is reduced by decreasing the intake stroke injection ratio, the reduction in the amount of heat in the exhaust gas flowing into the exhaust purification catalyst 17 will be limited.

[0023] <Effects of the Embodiment> <Effects of the Embodiment> The engine control device 30 of this embodiment provides the following effects.

[0024] (1) During the cold-start catalyst heating process, in which the ignition timing of the engine 10 is retarded to raise the temperature of the exhaust gas purification catalyst 17, the engine control device 30 performs an ignition timing retardation adjustment process to adjust the amount of ignition timing retardation according to the combustion state of the engine 10. In addition, during the cold-start catalyst heating process, the engine control device 30 performs a multi-injection process in which fuel injection from the in-cylinder injector 19 is divided into intake stroke injection and compression stroke injection. Furthermore, during the cold-start catalyst heating process, the engine control device 30 performs an injection ratio adjustment process to adjust the ratio of fuel injection amounts for intake stroke injection and compression stroke injection according to the change in engine output due to the adjustment of the ignition timing retardation amount in the ignition timing retardation adjustment process. As a result, the heating effect of the exhaust gas purification catalyst 17 can be maintained while suppressing changes in engine output due to the adjustment of the ignition timing retardation amount.

[0025] (2) In the injection ratio adjustment process during the cold catalyst heating process performed when the engine 10 is running cold, the engine control device 30 increases the ratio of the fuel injection amount for the compression stroke injection when the ignition timing retardation amount is reduced. Therefore, it is possible to adjust the injection ratio appropriately to correspond to the vaporization rate of the fuel for the intake stroke injection and compression stroke injection during cold operation.

[0026] (3) The engine control device 30 adjusts the injection ratio in the injection ratio adjustment process based on the result of comparing the actual value of the engine output with the target value. Therefore, it is possible to make appropriate adjustments to the injection ratio in response to changes in engine output corresponding to the adjustment of the ignition timing retardation amount.

[0027] (Other embodiments) The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0028] <Catalyst heating process during warm operation> The exhaust gas purification catalyst 17 may be heated by retarding the ignition timing, for example, to recover from poisoning of the exhaust gas purification catalyst 17, during warm operation of the engine 10. Even in such catalyst heating treatments during warm operation, if an ignition timing retardation adjustment process is performed to adjust the amount of ignition timing retardation according to the combustion state of the engine 10, the engine output will change in accordance with the change in the amount of ignition timing retardation. In such cases, the change in engine output can also be compensated for by adjusting the injection ratio. However, the relationship between the injection ratio and engine output differs between cold operation and warm operation.

[0029] Figure 3, mentioned above, shows the relationship between the intake stroke injection ratio and engine output during warm operation using a dashed line. During warm operation, the wall temperature inside the combustion chamber 11 is higher than during cold operation, so fuel adhesion to the wall is less likely to occur. During such warm operation, intake stroke injection, where the spray is atomized by mixing with the intake air, contributes a larger proportion of vaporized fuel to combustion than compression stroke injection. Therefore, during the catalyst heating process during warm operation, it is preferable to configure the injection ratio adjustment process to increase the intake stroke injection ratio when the ignition timing retardation amount is reduced by the retardation amount adjustment process. In the following explanation, the catalyst heating process performed during warm operation of the engine 10 will be referred to as the warm catalyst heating process.

[0030] Figure 4 shows a flowchart of the injection ratio adjustment routine executed by the engine control device 30 for injection ratio adjustment processing performed during the catalyst heating process while the engine is hot. The engine control device 30 repeatedly executes this routine at predetermined control cycles while the engine 10 is running.

[0031] When this routine is started, the engine control device 30 first determines in step S200 whether or not the hot catalyst heating process is currently being performed. If the engine control device 30 determines that the hot catalyst heating process is currently being performed (YES), it proceeds to step S210; otherwise, it terminates the processing of this routine for the current control cycle. In step S210, the engine control device 30 determines whether or not the actual output is equal to the target output. If the engine control device 30 determines that the actual output is equal to the target output (YES), it terminates the processing of this routine for the current control cycle; otherwise, it proceeds to step S220. In step S220, the engine control device 30 determines whether or not the actual output is less than the target output. If the engine control device 30 determines that the actual output is less than the target output (YES), it increases the intake stroke injection ratio in step S230. On the other hand, if the engine control device 30 determines that the actual output is not less than the target output, that is, that the actual output is greater than the target output (NO), it reduces the intake stroke injection ratio in step S240. After processing in step S230 or step S240, the engine control device 30 terminates the processing of this routine for the current control cycle.

[0032] <How to check the actual output of Engine 10> In the above embodiment, the engine control device 30 estimated the actual output of the engine 10 based on the engine rotational speed, engine load ratio, etc. However, the actual output of the engine 10 may be determined by other methods. For example, if a torque sensor is installed on the crankshaft 21, the actual output of the engine 10 can be calculated from the detected engine torque and the engine rotational speed. Also, if the engine 10 is mounted on a hybrid vehicle equipped with a motor driven and connected to the crankshaft 21, the engine torque can be determined using a resolver installed on the motor. In such cases as well, it is possible to calculate the actual output of the engine 10 based on the engine torque and the engine rotational speed.

[0033] <Adjusting the injection ratio> In the above embodiment, the engine control device 30 adjusted the injection ratio in the injection ratio adjustment process based on the comparison result between the actual output of the engine 10 and the target output. The adjustment of the injection ratio in response to the change in the output of the engine 10 due to the adjustment of the ignition timing retardation amount in the retardation amount adjustment process may be performed in other ways, such as the following:

[0034] In engine 10, feedback control of engine rotational speed may be performed during idle operation, etc. When catalyst heating is performed during such engine rotational speed feedback control, if the ignition timing retardation amount is reduced by the retardation amount adjustment process and the engine output increases, the actual engine rotational speed will be higher than the target value. Therefore, when engine rotational speed feedback control is performed, the change in engine output during catalyst heating can be confirmed by comparing the actual engine rotational speed with the target value. Thus, in such cases, it is possible to adjust the injection ratio in the injection ratio adjustment process based on the comparison result between the actual engine rotational speed and the target value.

[0035] The injection ratio adjustment process may be performed based on the amount of ignition timing retardation. For example, the injection ratio may be adjusted based on a comparison between the amount of ignition timing retardation before adjustment and the amount of ignition timing retardation after adjustment by the retardation adjustment process. If the amount of ignition timing retardation after adjustment is lower than before adjustment, the engine output will increase, so by adjusting the injection ratio to the side that decreases this engine output, the change in engine output can be suppressed.

[0036] <others> The number of intake stroke injections and compression stroke injections in multi-injection control may be changed. In other words, multi-injection control is a control that divides the fuel injection of the in-cylinder injection valve 19 into one or more intake stroke injections and one or more compression stroke injections.

[0037] • When performing catalyst heating treatment by retarding the ignition timing during both cold and warm operation of engine 10, the injection ratio adjustment treatment using the injection ratio adjustment routines in both Figure 2 and Figure 4 may also be performed.

[0038] The above embodiments and their modifications can also be applied to engines with configurations different from the engine 10 shown in Figure 1. [Explanation of symbols]

[0039] 10 Engines 11 Combustion chamber 12 Intake passage 13 Exhaust passage 14. Airflow meter 15 Throttle valve 17 Exhaust purifying catalyst 19. In-cylinder injection valve 20 Ignition system 21 Crank Axle 22 Crank angle sensor 30 Engine control unit 31 Arithmetic Processing Unit 32 Storage device 33. Accelerator pedal sensor 34. Vehicle speed sensor

Claims

1. An engine control device applicable to an engine equipped with an in-cylinder injection valve for injecting fuel into the combustion chamber and an exhaust gas purification catalyst installed in the exhaust passage, A catalyst heating treatment is performed to raise the temperature of the exhaust gas purification catalyst by retarding the ignition timing of the engine, A retardation adjustment process that adjusts the amount of ignition timing retardation according to the combustion state of the engine during the catalyst heating process, During the catalyst heating process, a multi-injection process is performed in which fuel injection by the in-cylinder injection valve is carried out by dividing it into intake stroke injection and compression stroke injection, An injection ratio adjustment process that adjusts the ratio of fuel injection amounts for the intake stroke injection and the compression stroke injection in the multi-injection process in accordance with the change in engine output due to the adjustment of the retardation amount in the retardation amount adjustment process, An engine control device that performs this function.

2. The engine control device according to claim 1, wherein the catalyst heating treatment is performed during cold operation of the engine, and the injection ratio adjustment treatment is configured to increase the ratio of the fuel injection amount for the compression stroke injection when the retardation amount is reduced by the retardation amount adjustment treatment.

3. The engine control device according to claim 1, wherein the catalyst heating treatment is performed during warm operation of the engine, and is configured to increase the ratio of the fuel injection amount for the intake stroke injection when the retardation amount is reduced by the retardation amount adjustment treatment.

4. The engine control device according to claim 1, wherein the adjustment of the fuel injection amount ratio in the injection ratio adjustment process is performed based on the result of comparing the actual value of the engine output with a target value.

5. The engine control device according to claim 1, wherein the adjustment of the fuel injection amount ratio in the injection ratio adjustment process is performed based on the result of comparing the actual engine rotation speed with a target value.

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