Engine control device

Abstract

The present application provides an engine control device, which can accurately diagnose a decrease in the warm-up promotion effect of a catalyst of a rapid catalyst warm-up control. An electronic control unit performs a rapid catalyst warm-up control, which promotes the warm-up of a catalyst by increasing the heat of exhaust gas discharged from a combustion chamber to an exhaust passage while implementing idle speed control at the time of cold start of an engine, and performs a diagnosis process that diagnoses a decrease in the warm-up promotion effect when the engine speed is below a predetermined decrease determination value for a predetermined period while the rapid catalyst warm-up control is being implemented. Furthermore, the electronic control unit starts the rapid catalyst warm-up control with the condition that the engine speed is determined to be in a predetermined idle speed region and the engine is in idle operation, and on the other hand, continues the control even after starting the control when it is determined not to be in idle operation in an idle determination process.

Description

Technical Field

[0001] This invention relates to an engine control device for rapidly warming up an exhaust purification catalyst disposed in the exhaust passage. Background Technology

[0002] For example, as described in Patent Document 1, there is a known engine that purifies exhaust gas by means of a catalyst disposed in the exhaust passage. In such an engine, rapid catalyst warm-up control is sometimes implemented during cold starts by means of ignition timing delay or the like to promote catalyst warm-up.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2014-172595 Summary of the Invention

[0004] It can be assumed that, for some reason, rapid catalytic warm-up control cannot fully utilize the catalytic's warm-up promoting effect. In this case, even with rapid catalytic warm-up control, the catalytic warm-up will be delayed, potentially exceeding permissible limits and worsening emissions. Therefore, it is necessary to diagnose whether the catalytic warm-up promoting effect based on rapid catalytic warm-up control is reduced, but there is room for improvement in this diagnostic method.

[0005] The engine control device for solving the above-mentioned problems is a device for controlling an engine in which an exhaust purification catalyst is installed in the exhaust passage supplying exhaust gas flow from the combustion chamber. Its configuration includes performing the following processes: idle speed control, adjusting the engine intake volume based on the deviation between a measured value and a target value of engine speed to reduce the deviation; idle speed determination processing, determining that idling operation occurs when the engine speed is within a predetermined idle speed range during the execution of the idle speed control; and rapid catalyst warm-up control, which, during engine cold starts, simultaneously performs the idle speed control and increases the intake air volume from the combustion chamber. The heat from the exhaust gas discharged from the combustion chamber to the exhaust passage is used to promote the warm-up of the catalyst; and a diagnostic process is performed to diagnose whether the warm-up promotion effect of the catalyst is reduced during the implementation of the rapid catalyst warm-up control, and the diagnostic process is as follows: if the engine speed is continuously below a predetermined reduction judgment value, the reduced warm-up promotion effect is diagnosed, the rapid catalyst warm-up control is started on the condition that the idle speed is determined to be running at idle speed in the idle speed determination process, and continues after the start even if the determination of the idle speed is negative in the idle speed determination process.

[0006] Invention Effects

[0007] The aforementioned engine control device has the following effect: it can more accurately diagnose whether the warm-up promotion effect of the catalyst based on rapid catalyst warm-up control has decreased. Attached Figure Description

[0008] Figure 1 This is a diagram schematically illustrating the structure of a drive system for a hybrid vehicle equipped with an engine control device in one embodiment.

[0009] Figure 2 This is a schematic diagram illustrating the structure of one embodiment of the engine control device.

[0010] Figure 3 yes Figure 2 The flowchart of the diagnostic process performed by the engine control unit.

[0011] Figure 4 yes Figure 2 The flowchart shows the process for determining the implementation of rapid catalyst warm-up control by the engine control unit. Detailed Implementation

[0012] The following is for reference. Figures 1-4 One embodiment of the engine control device will be described in detail.

[0013] <Structure of the vehicle's drive system>

[0014] First, refer to Figure 1 The structure of the drive system of the vehicle 10 equipped with the engine control device of this embodiment will be described. Figure 1 As shown, vehicle 10 is equipped with an engine 11. The engine 11 is connected to drive wheels 16 via a motor 13 and a transmission 14. A first clutch 12 is provided between the engine 11 and the motor 13 to disconnect or connect their power transmission. Furthermore, a second clutch 15 is provided between the transmission 14 and the drive wheels 16 to disconnect or connect their power transmission.

[0015] The engine 11 includes a combustion chamber 20 for combustion of a mixture, an intake passage 21 for introducing intake air into the combustion chamber 20, and an exhaust passage 22 for discharging exhaust gas from the combustion chamber 20. Figure 1In this case, the engine 11 has four combustion chambers 20, but the number of combustion chambers 20 can be arbitrarily changed. A throttle valve 23 is provided in the intake passage 21 for adjusting the amount of intake air introduced into the combustion chambers 20. A catalyst 24 for purifying exhaust gas is provided in the exhaust passage 22. Furthermore, the engine 11 is provided with an injector 25 that injects fuel into the intake air introduced into the combustion chambers 20 through the intake passage 21. Also, an ignition device 26 is provided in the combustion chambers 20 for igniting the air-fuel mixture (the mixture of intake air and fuel) by spark discharge. Furthermore, the engine 11 is provided with a variable valve mechanism 27 that allows the opening and closing time of the intake valve (not shown) that opens and closes the intake passage 21 to the combustion chambers 20 to be variable.

[0016] <Structure of Engine Control Unit>

[0017] Next, refer to Figure 2 The structure of the engine control device according to this embodiment will be described. The engine control device of this embodiment is configured as follows: Figure 2 The electronic control unit 30 shown is equipped with an arithmetic processing unit 31, a storage device 32, an input circuit 33, and an output circuit 34. The storage device 32 stores engine control programs and data. The electronic control unit 30 is configured to execute various processes for engine control by executing the programs read from the storage device 32 through the arithmetic processing unit 31.

[0018] Various sensors for detecting the operating status of the engine 11 or the driving status of the driver of the vehicle 10 are connected to the input circuit 33 of the electronic control unit 30. Examples of sensors connected to the input circuit 33 include an air flow meter 35, a crankshaft angle sensor 36, a camshaft angle sensor 37, and a coolant temperature sensor 38. The air flow meter 35 is a sensor that detects the flow rate of intake air flowing in the intake passage 21, i.e., the intake air volume GA. The crankshaft angle sensor 36 is a sensor that detects the rotation angle of the crankshaft, which is the output shaft of the engine 11, i.e., the crankshaft angle CNK. The camshaft angle sensor 37 is a sensor that detects the rotation angle of the camshaft, which is equipped with cams for opening and closing intake valves, i.e., the camshaft angle. The coolant temperature sensor 38 is a sensor that detects the engine coolant temperature THW, which is the temperature of the coolant in the engine 11. Furthermore, drive circuits for various actuators of the engine 11, such as the throttle valve 23, the injector 25, and the ignition device 26, are connected to the output circuit 34 of the electronic control unit 30.

[0019] Furthermore, the electronic control unit 30 calculates the engine speed NE, which is the crankshaft rotation speed, based on the detection result of the crankshaft angle CNK. Also, the electronic control unit 30 calculates the engine load rate KL based on the engine speed NE, the throttle opening ratio of the throttle 23, and so on. The engine load rate KL represents the intake air filling efficiency η of the combustion chamber 20. Moreover, the electronic control unit 30 confirms the operation of the variable valve mechanism 27 based on the detection results of the crankshaft angle sensor 36 and the camshaft angle sensor 37.

[0020] The electronic control unit 30, configured in this way, calculates the operating parameters of the actuators of the engine 11 based on the detection results of the sensors input to the input circuit 33. Examples of operating parameters calculated by the electronic control unit 30 include the throttle opening ratio (throttle valve 23), the fuel injection quantity and timing of the injector 25, and the ignition timing of the air-fuel mixture based on the ignition device 26. Then, the electronic control unit 30 outputs command signals corresponding to the calculated operating parameters to the drive circuits of each actuator via the output circuit 34, thereby controlling the engine.

[0021] <Driving Modes of Vehicle 10>

[0022] Vehicle 10 is configured as a hybrid vehicle capable of electric driving using only the power of motor 13 when engine 11 is stopped, and hybrid driving when engine 11 is running. Electric driving is performed by engaging the second clutch 15 and disengaging the first clutch 12, connecting only motor 13 (from engine 11) to drive wheel 16. Hybrid driving is performed by engaging both the first clutch 12 and the second clutch 15, connecting both engine 11 and motor 13 to drive wheel 16.

[0023] The switching from electric to hybrid driving is performed in the following order. The engine 11 is started according to the switching request. Starting the engine 11 can also be achieved by setting the first clutch 12 to a semi-engaged state and transmitting a portion of the power from the motor 13 to the engine 11. Alternatively, a dedicated engine starter motor can be installed separately from the motor 13, and the engine 11 can be started by rotating the engine 11 using this motor. After starting the engine 11, idle speed control for maintaining independent operation is performed, while rapid catalytic converter warm-up control is implemented to promote the warm-up of the catalytic converter 24. Idle speed control is based on the deviation between the measured value and the target value of the engine speed NE, adjusting the intake air volume GA of the engine 11 to reduce this deviation. In the following description, the target value of the engine speed NE in idle speed control is referred to as the target idle speed NIDL. On the other hand, rapid catalytic converter warm-up control is the control to increase the temperature of the exhaust gas discharged from the combustion chamber 20 to the exhaust passage 22 and flowing into the catalytic converter 24. For example, the electronic control unit 30 implements rapid catalyst warm-up control by delaying ignition timing, leaning the air-fuel ratio, and increasing valve overlap (hereinafter referred to as valve O / L). Once the catalyst 24 has warmed up, hybrid driving is initiated by engaging the first clutch 12 while synchronizing the rotation of the engine 11 and the motor 13.

[0024] <Diagnosis and Treatment>

[0025] During rapid catalytic converter warm-up control, for various reasons, the catalytic converter 24 may not warm up sufficiently. For example, if misfire occurs during rapid catalytic converter warm-up control, the ignition timing retardation (hereinafter referred to as ignition retardation) is sometimes limited to suppress combustion deterioration. If the ignition retardation is limited, the temperature of the exhaust gas exiting the combustion chamber 20 cannot be sufficiently increased, thus reducing the warm-up promotion effect of the catalytic converter 24. Furthermore, during rapid catalytic converter warm-up control, idle speed control may not function effectively, resulting in a decrease in engine speed NE. If engine speed NE decreases, even if the exhaust temperature is high, the exhaust flow through the catalytic converter 24 will decrease, and the heat received by the catalytic converter 24 from the exhaust will also decrease, thus reducing the warm-up promotion effect of the catalytic converter 24. If the warm-up promotion effect of rapid catalytic converter warm-up control decreases, the warm-up completion of the catalytic converter 24 will be delayed, which may cause the emissions of the engine 11 to exceed the permissible limit and deteriorate. During the rapid catalyst warm-up control, the electronic control unit 30 performs diagnostic processing to determine whether the warm-up promotion effect of the catalyst 24 has decreased.

[0026] exist Figure 3 An example of the processing sequence of the electronic control unit 30 used for this diagnostic process is shown. Figure 3 The process, during the rapid catalytic warm-up control, becomes a process repeatedly executed by the electronic control unit 30 according to each predetermined control cycle. Furthermore, in Figure 3 And then Figure 4 In Chinese, the "S" preceding the symbol indicates "step".

[0027] If start Figure 3 In the processing, the electronic control unit 30 determines whether at least one of the following conditions A to D is met. Condition A is that the ignition retarding amount is less than or equal to a predetermined value X1 (S100: "Yes"). Condition B is that the valve O / L amount is less than or equal to a predetermined value X2. Condition C is that the air-fuel ratio is richer than or equal to a predetermined value X3. Condition D is that the engine speed NE is less than or equal to a predetermined reduction determination value X4. The predetermined values ​​X1 to X3 are respectively set with the ignition retarding amount, valve O / L amount, and lean air-fuel ratio correction amount required to fully promote the warm-up of the catalyst 24. Furthermore, the reduction determination value X4 is set with a speed lower than the target idle speed NIDL. The fulfillment of these conditions A to D all indicate that the warm-up promotion effect of the catalyst 24 in the rapid catalyst warm-up control is in a state that is lower than before.

[0028] If the electronic control unit 30 determines that none of the requirements A to D are met (S100 to S106 are all "yes"), the current control cycle will end directly. Figure 3 The processing proceeds to step 108 if the electronic control unit 30 determines that one or more of requirements A through D are met. In step 108, the electronic control unit 30 increments the error counter CNT. The value of the error counter CNT is reset to "0" at the start of the rapid catalytic converter warm-up control. Therefore, the value of the error counter CNT represents the number of times at least one of requirements A through D is met during this rapid catalytic converter warm-up control. Then, in the subsequent step 110, the electronic control unit 30 determines whether the value of the error counter CNT is above or above a predetermined function reduction determination value. Then, if the electronic control unit 30 determines that the value of the error counter CNT is less than the function reduction determination value ("No"), the current control cycle ends. Figure 3 The processing. On the other hand, if the electronic control unit 30 determines that the value of the abnormal counter CNT is above the function reduction determination value ("Yes"), in step 112, it is diagnosed that the catalyst 24 is in a state of reduced warm-up promotion function based on rapid catalyst warm-up control.

[0029] Alternatively, diagnostic procedures can be performed in other ways. For example, the frequency or duration of the occurrence of elements A through D can be summarized separately for diagnostic purposes.

[0030] <Implementation Determination of Rapid Catalyst Warm-up Control>

[0031] exist Figure 4 The diagram shows the processing sequence of the electronic control unit 30 used to determine whether to implement rapid catalytic converter warm-up control. The electronic control unit 30 executes this process repeatedly according to predetermined control cycles during engine 11 operation. Figure 4 The processing. In Figure 4 In the process, the electronic control unit 30 operates the implementation flag for rapid catalytic warm-up control. Then, the electronic control unit 30 implements rapid catalytic warm-up control according to the implementation flag. Specifically, the electronic control unit 30 starts rapid catalytic warm-up control when switching from a state where the implementation flag is cleared to a state where it is set, and continues rapid catalytic warm-up control while the implementation flag is set. Then, the electronic control unit 30 completes or stops rapid catalytic warm-up control when switching from a state where the implementation flag is set to a state where it is cleared. Here, completion of rapid catalytic warm-up control means ending rapid catalytic warm-up control upon completion of catalytic 24 warm-up. And, termination of rapid catalytic warm-up control means ending rapid catalytic warm-up control before catalytic 24 warm-up is complete. Furthermore, in... Figure 4 During processing, after the electronic control unit 30 determines the status of the implementation flag in step 202 or step 210, it ends the current control cycle. Figure 4 The processing.

[0032] If start Figure 4 In the processing, firstly in step 200, the electronic control unit 30 determines whether there is a rapid catalytic converter warm-up request. If the engine 11 has started and the catalyst 24 is not warmed up, the electronic control unit 30 determines that there is a rapid catalytic converter warm-up request. Therefore, when starting the engine 11 while the catalyst 24 is warmed up, it does not determine that there is a rapid catalytic converter warm-up request, and the engine 11 is run. Furthermore, if the engine 11 is started while the catalyst 24 is not warmed up, and the catalyst 24 has completed warm-up, it is determined that there is no rapid catalytic converter warm-up request. Then, if the electronic control unit 30 determines that there is no rapid catalytic converter warm-up request ("No"), the process proceeds to step 202. Then, in step 202, the electronic control unit 30 clears the implementation flag.

[0033] In contrast, if the electronic control unit 30 determines that there is a request for rapid catalytic converter warm-up (S200: "Yes"), the process proceeds to step 204. Then, in step 204, the electronic control unit 30 determines whether the mechanism of the engine 11 required for exhaust gas warm-up in the rapid catalytic converter warm-up control (hereinafter referred to as the warming mechanism) is functioning properly. The warming mechanism includes the throttle valve 23, actuators of the engine 11 used in the rapid catalytic converter warm-up control, and sensors. Then, if the electronic control unit 30 determines that the warming mechanism is functioning properly ("Yes"), the process proceeds to step 206; if it determines that the mechanism is not functioning properly ("No"), the process proceeds to step 202.

[0034] In step 206, the electronic control unit 30 determines whether an implementation flag has been set. If the implementation flag has been set ("Yes"), the electronic control unit 30 maintains the state of setting the implementation flag and ends the current control cycle. Figure 4 In contrast, if the implementation flag is not set ("No"), the electronic control unit 30 proceeds to step 208.

[0035] In step 208, the electronic control unit 30 determines whether the engine speed NE is within the idle speed range. The idle speed range refers to the range of engine speeds NE that are deemed to be appropriately controlled based on idle speed control. In this embodiment, the range of engine speeds NE between the lower limit speed LO and the upper limit speed HI is set as the idle speed range. That is, speeds lower than the target idle speed NIDL are set as the lower limit speed LO, and speeds higher than the target idle speed NIDL are set as the upper limit speed HI. Furthermore, in this embodiment, speeds lower than the aforementioned reduction determination value X4 are set as the lower limit speed LO. Then, if the electronic control unit 30 determines that the engine speed NE is within the idle speed range ("Yes"), it sets an implementation flag in step 210. On the other hand, if the electronic control unit 30 determines that the engine speed NE is not within the idle speed range ("No"), it proceeds to step 202.

[0036] <The Role of the Implementation Method>

[0037] When the engine 11 is cold-started, the electronic control unit 30 implements rapid catalytic converter warm-up control to warm up the catalyst 24 early. This rapid catalytic converter warm-up control is performed while idle speed control is in place to maintain continuous idling of the engine 11. Therefore, the electronic control unit 30 initiates rapid catalytic converter warm-up control based on the condition that the engine 11 is idling. Furthermore, the electronic control unit 30 performs the following idle speed determination process: when idle speed control is executed, if the engine speed NE is within a predetermined idle speed range, it is determined that the engine is idling.

[0038] On the other hand, during the implementation of rapid catalytic converter warm-up control, the electronic control unit 30 performs a diagnostic process to determine whether the warm-up promotion effect of the catalyst 24 based on this control has decreased. During the diagnostic process, if the engine speed NE remains below a predetermined reduction threshold X4, it is diagnosed that the warm-up promotion effect of the catalyst 24 has decreased.

[0039] As described above, rapid catalytic converter warm-up control is performed while the engine 11 is idling. Considering this, if the engine 11 is no longer idling during the implementation of rapid catalytic converter warm-up control, the control should be stopped. However, in this case, if the engine speed NE drops below the lower limit of the idle speed range (LO) during rapid catalytic converter warm-up control, the control is immediately stopped at that point. Therefore, it is possible that the state where the engine speed NE is below the reduction determination value X4 will not continue before the diagnostic process diagnoses a reduction in the warm-up promotion effect of the catalyst 24. In contrast, in this embodiment, the electronic control unit 30 continues to perform rapid catalytic converter warm-up control even if the engine speed NE deviates from the idle speed range after the rapid catalytic converter warm-up control is started. Therefore, if the engine speed NE continues to drop below the reduction determination value X4, a reduction in the warm-up promotion effect of the catalyst 24 is diagnosed.

[0040] <Effects of the Implementation Method>

[0041] In this embodiment, the electronic control unit 30 of the engine control device controls an engine 11 in which an exhaust purification catalyst 24 is installed in the exhaust passage 22 for the exhaust flow from the combustion chamber 20. The electronic control unit 30 performs idle speed control, idle speed determination processing, rapid catalyst warm-up control, and diagnostic processing. Idle speed control adjusts the intake air volume GA of the engine 11 by reducing the deviation between the measured value and the target value of the engine speed NE. Idle speed determination processing determines that the engine is idling when the engine speed NE is within a predetermined idle speed range during idle speed control. Rapid catalyst warm-up control promotes the warm-up of the catalyst 24 by increasing the heat of the exhaust from the combustion chamber 20 to the exhaust passage 22 during a cold start of the engine 11 while implementing idle speed control. Diagnostic processing diagnoses whether the warm-up promotion effect of the catalyst 24 is reduced during the implementation of rapid catalyst warm-up control. In its diagnostic process, the electronic control unit 30 diagnoses a decrease in the warm-up promotion effect when the engine speed NE remains below a predetermined reduction determination value X4. Then, the electronic control unit 30 initiates rapid catalytic converter warm-up control based on the condition that the engine is in idle operation as determined in the idle speed determination process. Furthermore, after initiating this control, it continues to perform this control even if the engine is not in idle operation as determined in the idle speed determination process. Therefore, the diagnosis of a decrease in the warm-up promotion effect of the catalyst 24 based on the continuous state of the engine speed NE being below the predetermined reduction determination value X4 is not hindered by the termination of the rapid catalytic converter warm-up control. Therefore, the engine control device of this embodiment has the effect of accurately diagnosing a decrease in the warm-up promotion effect of the catalyst 24 under rapid catalytic converter warm-up control.

[0042] (Other implementation methods)

[0043] The above-described embodiments can be implemented in the following ways. The above-described embodiments and the following modifications can be combined with each other to implement them without causing technical inconsistencies.

[0044] • The control parameters for rapid catalytic converter warm-up can be modified appropriately. That is, rapid catalytic converter warm-up control can be achieved simply by increasing the heat of the exhaust gas discharged from the combustion chamber 20 to the exhaust passage 22 during idling to promote the warm-up of the catalytic converter 24.

[0045] • The specific handling procedures can be modified appropriately. The diagnostic handling should simply be any procedure that diagnoses a reduced warm-up effect of catalyst 24 when the engine speed NE remains below the reduction threshold X4.

[0046] The engine control device described above can also be similarly applied to devices with... Figure 1 Vehicles with different drive systems, such as those with Figure 1 Engines in different forms of hybrid vehicles or engine vehicles that are driven solely by an engine.

[0047] Symbol Explanation

[0048] 10-Vehicle, 11-Engine, 12-First clutch, 13-Motor, 14-Transmission, 15-Second clutch, 16-Drive wheel, 20-Combustion chamber, 21-Intake passage, 22-Exhaust passage, 23-Throttle valve, 24-Catalyst, 25-Injector, 26-Ignition device, 27-Variable valve timing mechanism, 30-Electronic control unit, 31-Processing unit, 32-Storage device, 33-Input circuit, 34-Output circuit, 35-Air flow meter, 36-Crankshaft angle sensor, 37-Cam angle sensor, 38-Water temperature sensor.

Claims

1. An engine control device that controls an engine in which an exhaust purification catalyst is provided in an exhaust passage for supplying exhaust flow from the combustion chamber, the engine control device being characterized in that it performs the following processing: Idle speed control adjusts the engine's intake air volume by reducing the deviation between a measured value and a target value of engine speed. The idle speed determination process determines that the engine is idling if the engine speed is within a predetermined idle speed range during the idle speed control process. Rapid catalytic converter warm-up control, during engine cold start, while implementing the idle speed control, promotes catalyst warm-up by increasing the heat of exhaust gas discharged from the combustion chamber to the exhaust passage; and Diagnostic procedures include diagnosing whether the catalytic converter's warm-up effect is reduced during the implementation of the rapid catalytic converter warm-up control, and... The diagnostic process is as follows: if the engine speed remains below a predetermined reduction threshold for an extended period, the warm-up enhancement effect is diagnosed as reduced. The rapid catalyst warm-up control starts on the condition that the idle speed determination process determines that the system is in the idle operation, and continues to operate even if the idle speed determination process determines that the system is not in the idle operation after the start.

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