Engine control unit

Abstract

To enable intermittent shutdowns to be initiated as early as possible while minimizing the deterioration of emissions. [Solution] An electronic control unit 20 that controls an engine 10 in which an exhaust purification catalyst 16 is installed in the exhaust passage 13 determines whether or not the amount of regulated substances in the exhaust discharged into the outside air is high during the catalyst warm-up period until the exhaust purification catalyst 16 has finished warming up. If it determines that the amount of regulated substances is not high, it is configured to allow intermittent shutdown of the engine 10 at an earlier stage than if it were determined that the amount is high.

Description

Technical Field

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

Background Art

[0002] In in-vehicle engines and the like, exhaust gas is purified by an exhaust gas purification catalyst installed in the exhaust passage, thereby suppressing the discharge of regulated substances in the exhaust gas such as NOx into the outside air. However, the exhaust gas purification catalyst is in a state where it cannot sufficiently purify the exhaust gas until warm-up is completed. Patent Document 1 describes that in order to suppress the discharge amount of unpurified exhaust gas into the outside air within an allowable range, the output of the engine is limited during the period until the warm-up of the exhaust gas purification catalyst is completed. Further, Patent Document 2 describes that intermittent stopping of the engine is prohibited while the engine water temperature rises to a predetermined temperature after the engine is started.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] If the exhaust gas purification catalyst becomes inactive due to a temperature drop during intermittent stopping of the engine, emissions deteriorate at the time of resumption from intermittent stopping. The deterioration of emissions at the time of resumption can be avoided by prohibiting intermittent stopping until the temperature of the exhaust gas purification catalyst becomes sufficiently high so that the activity of the exhaust gas purification catalyst can be maintained even if the temperature drops during intermittent stopping. However, in such a case, the period during which the effect of reducing the fuel consumption of the engine by intermittent stopping cannot be enjoyed becomes long.

Means for Solving the Problems

[0005] An engine control device that solves the above problems is a control device applied to an engine in which an exhaust gas purification catalyst is installed in the exhaust passage, and is configured to prohibit intermittent stopping of the engine when the engine is started, to determine whether or not there is a high level of emissions of regulated substances in the exhaust into the outside air during the catalyst warm-up period until the exhaust gas purification catalyst has warmed up, and, if it is determined that there is no high level of emissions, to release the prohibition of intermittent stopping at an earlier stage than if it were determined that there is a high level of emissions. [Effects of the Invention]

[0006] The above-mentioned engine control device has the effect of enabling intermittent stopping to be initiated earlier, within a range that can suppress the deterioration of emissions. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram schematically shows the configuration of one embodiment of an engine control device. [Figure 2] Figure 1 is a flowchart showing the flow of processing performed by the engine control device after the engine has started. [Figure 3] Figure 1 is a time chart showing the changes in the catalytic converter warm-up flag, the changes in engine output, the changes in engine water temperature, and the changes in the intermittent stop permission flag when an engine to which the engine control device shown in Figure 1 is applied is subjected to power limiting during the catalytic converter warm-up period. [Figure 4] Figure 1 is a time chart showing the changes in the catalytic converter warm-up flag, the changes in engine output, the changes in engine water temperature, and the changes in the intermittent stop permission flag when an engine to which the engine control device shown in Figure 1 is applied is not subject to power limiting during the catalytic converter warm-up period. [Modes for carrying out the invention]

[0008] An embodiment of the engine control device will be described in detail below with reference to Figures 1 to 3. <Engine control system configuration> First, the configuration of the engine control device of this embodiment will be described with reference to Figure 1. The engine 10 to which the engine control device of this embodiment is applied is mounted in a vehicle. The engine 10 includes a combustion chamber 11 for burning a fuel-air 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. A throttle valve 14 is installed in the intake passage 12. The throttle valve 14 adjusts the flow rate of air flowing into the combustion chamber 11 through the intake passage 12 by changing the opening ratio. An exhaust gas purification catalyst 16 is installed in the exhaust passage 13 to purify the exhaust gas. Furthermore, the engine 10 is equipped with an injector 17 that injects fuel into the air used for combustion in the combustion chamber 11 to form a fuel-air mixture. The engine 10 is also equipped with an ignition device 18 that ignites the fuel-air mixture in the combustion chamber 11 by spark discharge.

[0009] The engine 10 is controlled by an electronic control unit 20, which acts as an engine control device. The electronic control unit 20 includes a processing circuit 21 that performs various processes for engine control, and a storage device 22 that stores programs and data for engine control. Detection signals from sensors such as an airflow meter 23, a crank angle sensor 24, an accelerator pedal sensor 25, and a water temperature sensor 26 are input to the electronic control unit 20. The airflow meter 23 is a sensor that detects the intake air volume Ga, and the crank angle sensor 24 is a sensor that detects the crank angle θc. The accelerator pedal sensor 25 is a sensor that detects the accelerator pedal opening degree Acc, and the water temperature sensor 26 is a sensor that detects the engine water temperature Thw. The intake air volume Ga represents the flow rate of air flowing into the combustion chamber 11 through the intake passage 12. The crank angle θc represents the rotation angle of the crankshaft 27, which is the output shaft of the engine 10. The accelerator pedal opening degree Acc represents the amount the driver depresses the accelerator pedal 28. The engine water temperature Thw represents the temperature of the coolant in the engine 10. The electronic control unit 20 determines the engine speed Ne based on the detection result of the crank angle θc. The electronic control unit 20 also determines the intake air filling ratio η of the combustion chamber 11 from the intake air volume Ga, engine speed Ne, etc.

[0010] The electronic control unit 20 determines the control parameters of the engine 10, such as throttle opening, fuel injection amount, and ignition timing, based on the detection signals from each sensor. Based on these determined parameters, the electronic control unit 20 controls the engine by operating the actuators of the engine 10, such as the throttle valve 14, injector 17, and ignition device 18. For example, the electronic control unit 20 calculates the required engine output Pe* based on the accelerator pedal opening (Acc). The required engine output Pe* represents the engine output necessary to generate the driving force of the vehicle requested by the driver through the operation of the accelerator pedal 28. The electronic control unit 20 then determines the throttle opening and operates the throttle valve 14 so that the intake air filling rate η of the combustion chamber 11 is obtained according to the required engine output Pe*. Furthermore, the electronic control unit 20 determines the fuel injection amount according to the intake air filling rate η and operates the injector 17.

[0011] <Output limiting control> The electronic control unit 20 implements output limiting control to restrict the output of the engine 10 during the period until the exhaust gas purification catalyst 16 has warmed up. When implementing output limiting control, the electronic control unit 20 sets an output limit value LM, and if the requested engine output Pe* exceeds the output limit value LM, it controls the engine 10 to make the engine output corresponding to the output limit value LM. In this way, the electronic control unit 20 limits the engine output during output limiting control to the output limit value LM or less. In this embodiment, the electronic control unit 20 sets the output limit value LM as a value that increases in proportion to the increase in the accumulated air volume after the engine 10 has started.

[0012] In this embodiment, the electronic control unit 20 estimates the temperature of the exhaust gas purification catalyst 16 based on the operating state of the engine 10. In the following description, the electronic control unit 20 will refer to the temperature of the exhaust gas purification catalyst 16 as the estimated catalyst temperature. The electronic control unit 20 determines that the exhaust gas purification catalyst 16 has warmed up when the estimated catalyst temperature reaches or exceeds a predetermined warm-up completion temperature.

[0013] <Intermittent stop control> Furthermore, the electronic control unit 20 performs intermittent stop control of the engine 10. In this embodiment, when the electronic control unit 20 determines that the vehicle is stopped, such as at a traffic light, it stops the engine 10 and performs intermittent stop control to restart the engine 10 in response to the driver's starting operation. Examples of starting operations include releasing the brake pedal and pressing the accelerator pedal 28. The electronic control unit 20 prohibits intermittent stop when the engine is started, and then lifts that prohibition afterward.

[0014] <Control during engine startup> As described above, the electronic control unit 20 implements output limiting control during the catalyst warm-up period after engine start. Furthermore, the electronic control unit 20 prohibits intermittent stopping of the engine 10 when it is started. The following describes the processing flow of the electronic control unit 20 from the start of the engine 10 until the prohibition on intermittent stopping is lifted.

[0015] Figure 2 shows the processing flow of the electronic control unit 20 from the start of the engine 10 to the release of the intermittent stop prohibition. The electronic control unit 20 prohibits intermittent stop when the engine 10 is started (S100). In addition, the electronic control unit 20 starts output limiting control at the same time as the engine 10 is started (S110).

[0016] Thereafter, when the warm-up of the exhaust purification catalyst 16 is completed (S120: YES), the electronic control unit 20 terminates the output control restriction (S130). Then, the electronic control unit 20 determines whether an output control restriction has been applied during the implementation of the output control restriction (S140). Specifically, it is determined whether the required engine output Pe* has ever become equal to or greater than the output control limit value LM during the implementation of the output control restriction. When an output control restriction has been applied (S140: YES), the electronic control unit 20 waits for the engine coolant temperature Thw to become equal to or higher than the predetermined allowable coolant temperature TD and then解除 the prohibition of intermittent stop (S150). In contrast, when no output control restriction has been applied (S140: NO), the electronic control unit 20解除 the prohibition of intermittent stop at the current time, that is, at the completion of the catalyst warm-up (S160).

[0017] 〈Operation of the Embodiment〉 In the engine 10, after the warm-up of the exhaust purification catalyst 16 is completed, the exhaust purification catalyst 16 purifies the exhaust gas, thereby suppressing the discharge of regulated substances in the exhaust gas such as NOx into the outside air. However, during the catalyst warm-up period, a certain amount of regulated substances cannot be completely purified by the exhaust purification catalyst 16 and are discharged into the outside air. The discharge amount of regulated substances in the exhaust gas into the outside air during the catalyst warm-up period needs to be suppressed to a certain amount or less. In the following description, the discharge amount of regulated substances in the exhaust gas into the outside air is referred to as the emission discharge amount.

[0018] In the case of this embodiment, during the catalyst warm-up period, by restricting the output of the engine 10 to be equal to or less than the output control limit value LM by the output control restriction, the emission discharge amount during the catalyst warm-up period is suppressed within an allowable range. In the output control restriction, the electronic control unit 20 increases the output control limit value LM in accordance with the increase in the integrated air amount after the engine is started. And thereby, in accordance with the increase in the exhaust purification rate of the exhaust purification catalyst 16 as the warm-up progresses, the output control of the engine 10 is relaxed.

[0019] On the other hand, the catalyst temperature may decrease during the intermittent stop of the engine 10. Therefore, even if the intermittent stop of the engine 10 is performed after the warm-up of the exhaust purification catalyst 16, the exhaust purification catalyst 16 may return to the un-warmed state again due to the decrease in the catalyst temperature during the intermittent stop. In such a case, re-warming of the exhaust purification catalyst 16 is required after the return from the intermittent stop, and unpurified exhaust is discharged to the outside air during that period. Therefore, the total emission amount during the first catalyst warm-up period and the re-warming period after the return from the intermittent stop may exceed the allowable range.

[0020] In order to avoid re-warming of the exhaust purification catalyst 16 due to the intermittent stop, it is necessary to prohibit the intermittent stop of the engine 10 until the catalyst temperature rises to a temperature at which the catalyst temperature can be maintained above the warm-up completion temperature even due to the temperature decrease during the intermittent stop. In the case of this embodiment, it is determined that the catalyst temperature is rising until the return to the un-warmed state can be avoided when the engine water temperature Thw is higher than the allowable water temperature TD. And the fact that the engine water temperature Thw is higher than the allowable water temperature TD is set as one of the conditions for releasing the prohibition of the intermittent stop.

[0021] If the emission emissions during the catalyst warm-up period are low, even if intermittent stopping necessitates re-warming the exhaust purification catalyst 16, the total emission emissions during the catalyst warm-up period and re-warm-up period may remain within an acceptable range. Therefore, the electronic control unit 20 determines whether or not the emission emissions during the catalyst warm-up period are high. In this embodiment, the electronic control unit 20 determines that the emission emissions are high if the output limit is applied in the output limit control performed during the catalyst warm-up period. More specifically, the electronic control unit 20 determines that the emission emissions are high if, during output limit control, a requested engine output Pe* greater than or equal to the output limit value LM is set. When the electronic control unit 20 determines that the emission emissions during the catalyst warm-up period are high, it releases the prohibition on intermittent stopping when the engine water temperature Thw reaches or exceeds the permitted water temperature TD. In response to this, if the electronic control unit 20 determines that there are no high emissions during the catalyst warm-up period, it lifts the ban on intermittent shutdown before the engine water temperature Thw exceeds the permitted water temperature TD, specifically at the end of the catalyst warm-up period.

[0022] Figure 3 shows an example of the control behavior after engine start-up by the engine control device of this embodiment. Figure 3(a) shows the transition of the catalyst warm-up flag, Figure 3(b) shows the transition of the engine output, Figure 3(c) shows the transition of the engine water temperature Thw, and Figure 3(d) shows the transition of the intermittent stop permission flag. The catalyst warm-up flag is a flag that indicates whether or not the exhaust purification catalyst 16 has finished warming up. The intermittent stop permission flag is a flag that indicates whether or not intermittent stopping of the engine 10 is permitted. When the engine 10 is started, both the catalyst warm-up flag and the intermittent stop permission flag are cleared. The electronic control unit 20 sets the catalyst warm-up flag when it determines that the exhaust purification catalyst 16 has finished warming up. The electronic control unit 20 also sets the intermittent stop permission flag when it releases the prohibition on intermittent stopping. In Figure 3(b) and Figure 4(b) described later, the trend of the required engine output Pe* is shown by a dashed line, the trend of the output limit value LM is shown by a dashed-dotted line, and the trend of the engine output is shown by a solid line.

[0023] In the case of Figure 3, at time t1, the exhaust purification catalyst 16 has finished warming up, and the catalyst warm-up flag is set. The electronic control unit 20 has been performing output limit control of the engine 10 up to this time t1. In the case of Figure 3, during the execution of output limit control up to time t1, there is a period in which the requested engine output Pe* is equal to or greater than the output limit value LM. That is, there is a period in which the engine output fluctuates in line with the output limit value LM due to the application of the engine output limit due to output limit control. In this case, at the time t2 thereafter, when the engine water temperature Thw becomes equal to or greater than the permitted water temperature TD, the electronic control unit 20 releases the prohibition of intermittent stop and sets the intermittent stop permission flag.

[0024] Figure 4 shows another example of the control mode after engine start-up by the engine control device of this embodiment. Figure 4(a) shows the change in the catalyst warm-up flag, Figure 4(b) shows the change in engine output, Figure 4(c) shows the change in engine water temperature Thw, and Figure 4(d) shows the change in the intermittent stop permission flag.

[0025] In the case of Figure 4, the exhaust purification catalyst 16 has finished warming up at time t1, and the catalyst warm-up flag is set. The electronic control unit 20 has been performing output limit control of the engine 10 up to this time t1. However, in the case of Figure 4, the requested engine output Pe* remains below the output limit value LM throughout the execution of the output limit control up to time t1. Therefore, in the case of Figure 4, the output limit control ends without the output limit being applied. In this case, the electronic control unit 20 releases the prohibition of intermittent stopping and sets the intermittent stopping permission flag at time t1, when the exhaust purification catalyst 16 has finished warming up. Therefore, in the case of Figure 4, the prohibition of intermittent stopping is released earlier than time t2, when the engine water temperature Thw reaches the permission water temperature TD, specifically at time t1, which is the end of the catalyst warm-up period.

[0026] <Effects of the Embodiment> The engine control device of this embodiment described above can achieve the following effects. (1) The electronic control unit 20 determines whether or not the emission emissions during the catalyst warm-up period are high. If the electronic control unit 20 determines that the emission emissions during the catalyst warm-up period are not high, it lifts the ban on intermittent stopping earlier than if it were determined that the emissions were high. If the emission emissions during the catalyst warm-up period are not high, even if the exhaust purification catalyst 16 needs to be re-warmed due to the early implementation of intermittent stopping, the total emission emissions during the catalyst warm-up period and the re-warm-up period can be kept within an acceptable range. Therefore, the engine control device of this embodiment has the effect of enabling intermittent stopping to be started earlier within a range that can suppress the deterioration of emissions.

[0027] (2) The emission amount during power limit control is maximized when the engine output changes in line with the power limit value LM. The power limit value LM is set so that the maximum expected value of emission during power limit control is within an acceptable range. Therefore, it is possible to determine whether there is a margin for emission during the catalyst warm-up period based on whether or not an engine output exceeding the power limit value LM is requested during power limit control. In contrast, the electronic control unit 20 in the engine control device of this embodiment determines that the emission amount is high when an engine output exceeding the power limit value LM is requested during power limit control. Therefore, it is possible to accurately determine whether or not the emission amount during the catalyst warm-up period is high.

[0028] (3) If the electronic control unit 20 determines that the emission emissions during the catalyst warm-up period are not high, it releases the prohibition on intermittent stopping at the end of the catalyst warm-up period. If the electronic control unit 20 determines that the emission emissions during the catalyst warm-up period are high, it releases the prohibition on intermittent stopping when the engine water temperature Thw rises to or above the predetermined permitted water temperature TD after the end of the catalyst warm-up period. Therefore, if there is no margin for emission emissions, the prohibition on intermittent stopping can be released after the exhaust purification catalyst 16 is no longer needed to be rewarmed after returning from intermittent stopping. If there is a margin for emission emissions, the prohibition on intermittent stopping can be released at the end of the catalyst warm-up period.

[0029] <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.

[0030] (Determination of the amount of emissions during the catalyst warm-up period) In the above embodiment, it was determined whether or not the emission output during the catalyst warm-up period was high based on whether or not output limiting was applied during the implementation of output limiting control. This determination may be made by other methods. The emission output during the catalyst warm-up period is correlated with the cumulative air volume and cumulative power output of the engine 10 during the same period. Therefore, it is possible to determine that the emission output during the catalyst warm-up period is high if the cumulative air volume of the engine 10 during the catalyst warm-up period exceeds a predetermined value, or if the cumulative power output of the engine 10 during the catalyst warm-up period exceeds a predetermined value.

[0031] (When the ban on intermittent shutdowns will be lifted) In the above embodiment, if it was determined that the emission volume during the catalyst warm-up period was high, the prohibition on intermittent stopping was lifted when the engine water temperature Thw reached or exceeded the permitted water temperature TD after the catalyst warm-up period ended. The conditions for lifting the prohibition on intermittent stopping in this case may be different from those. For example, the decision on whether or not to lift the prohibition on intermittent stopping may be made based on the estimated catalyst temperature, the cumulative amount of air after starting the engine 10, the cumulative output, etc.

[0032] In the above embodiment, if it was determined that the emission emissions during the catalyst warm-up period were not high, the prohibition on intermittent stopping was lifted at the end of the catalyst warm-up period. The timing of lifting the prohibition on intermittent stopping in this case may be set to a different time. For example, the prohibition on intermittent stopping may be lifted when the engine water temperature Thw reaches a predetermined temperature lower than the permitted water temperature TD. In any case, if it is determined that the emission emissions during the catalyst warm-up period are not high, the prohibition on intermittent stopping can be lifted earlier than when it is determined that the emissions are high, thereby achieving the effects described in (1) above.

[0033] (others) If the determination of whether or not emissions are high during the catalyst warm-up period is not based on whether or not output limiting was applied during the implementation of output limiting control, then the configuration may be such that output limiting control is not implemented during the catalyst warm-up period.

[0034] In the above embodiment, intermittent stop control was performed to stop the engine 10 when the vehicle was stopped and to restart the engine 10 in response to a starting operation. The intermittent stopping of the engine 10 may be performed in other ways. For example, the engine control device of the above embodiment may be applied to a hybrid vehicle, and the engine stopping during motor-driven operation may be performed as the intermittent stopping of the engine in the above embodiment.

[0035] <Additional Notes> [Note 1] An engine control device applicable to an engine in which an exhaust gas purification catalyst is installed in the exhaust passage, which prohibits intermittent stopping of the engine when the engine is started, determines whether or not there is a high level of emissions of regulated substances in the exhaust into the outside air during the catalyst warm-up period until the exhaust gas purification catalyst has warmed up, and if it is determined that there is no high level of emissions, permits intermittent stopping of the engine at an earlier time than if it were determined that there is a high level of emissions.

[0036] [Note 2] An engine control device according to Note 1, which performs output limit control during the catalyst warm-up period to control the engine output to the output limit value when an engine output exceeding a predetermined output limit value is requested, and determines that the emissions are high when an engine output exceeding the output limit value is requested while the output limit control is being performed.

[0037] [Note 3] An engine control device according to Note 1 or 2, which determines that the discharge volume is high when the total amount of air in the engine during the catalyst warm-up period exceeds a predetermined value. [Note 4] An engine control device according to any one of Notes 1 to 3, which determines that the engine is in a state of high emissions when the cumulative output of the engine during the catalyst warm-up period exceeds a predetermined value.

[0038] [Note 5] An engine control device according to any one of Notes 1 to 4, wherein if it is determined that the emission level is not high, the prohibition of intermittent stopping is lifted at the end of the catalyst warm-up period, and if it is determined that the emission level is high, the prohibition of intermittent stopping is lifted when the engine water temperature rises above a predetermined temperature after the end of the catalyst warm-up period. [Explanation of symbols]

[0039] 10 Engines 11 Combustion chamber 12 Intake passage 13 Exhaust passage 14 Throttle valve 16 Exhaust purifying catalyst 17 Injectors 18 Ignition system 20 Electronic control units 21 Processing Circuit 22 Storage device 23 Airflow Meter 24 Crank angle sensor 25. Accelerator pedal sensor 26 Water temperature sensor 27 Crank Axle 28. Accelerator pedal

Claims

1. A control device applicable to an engine in which an exhaust gas purification catalyst is installed in the exhaust passage, The intermittent stopping of the engine is prohibited when the engine is started, To determine whether the amount of regulated substances released into the outside air from the exhaust gas is high during the catalyst warm-up period until the exhaust gas purification catalyst has finished warming up, If it is determined that the emissions are not high, the prohibition on intermittent shutdown will be lifted at an earlier stage than if it were determined that the emissions are high. An engine control device that performs this function.

2. During the catalyst warm-up period, output limit control is implemented to control the engine output to the output limit value if an engine output exceeding a predetermined output limit value is requested. If the engine output is requested to exceed the output limit value while the output limit control is being implemented, it is determined that the emissions are high. The engine control device according to claim 1.

3. The engine control device according to claim 1, which determines that the engine is in a state of high emissions when the total amount of air in the engine during the catalyst warm-up period exceeds a predetermined value.

4. The engine control device according to claim 1, which determines that the engine is in a state of high emissions when the cumulative output of the engine during the catalyst warm-up period exceeds a predetermined value.

5. The engine control device according to claim 1, wherein if it is determined that the emission level is not high, the prohibition of intermittent stopping is released at the end of the catalyst warm-up period, and if it is determined that the emission level is high, the prohibition of intermittent stopping is released when the engine water temperature rises above a predetermined temperature after the end of the catalyst warm-up period.

Images