Control device for on-vehicle internal combustion engine

Abstract

To suppress an excessive rise in temperature of a filter device while suppressing deterioration of drivability.SOLUTION: An ECM 20 executes cooling control to temporarily increase a throttle opening when the temperature of a filter device 18 becomes equal to or higher than a threshold value during fuel cut of an on-vehicle internal combustion engine 10. The ECM 20 sets the amount of increase in the throttle opening during the cooling control and the time period of increase so that the amount of change in vehicle deceleration caused by the execution of the cooling control is less than a preset value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine mounted on a vehicle. [Background technology]

[0002] As an exhaust purification device for an internal combustion engine mounted on a vehicle, etc., there is a filter device that collects particulate matter (PM) in the exhaust. During fuel cut of the internal combustion engine, the exhaust gas supplied to the filter device is replaced with fresh air. At this time, if the filter device is in a high temperature state, the PM accumulated in the filter device will burn. Then, there is a risk that the temperature of the filter device will rise excessively due to the heat generated by the combustion.

[0003] Patent Document 1 describes a control device for an on-vehicle internal combustion engine that performs cooling control of a filter device when the filter device reaches a certain temperature or higher during a fuel cut. This control device performs cooling control by opening the throttle valve and closing the EGR valve to increase the flow rate of gas flowing into the filter device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-211788 A Summary of the Invention [Problem to be solved by the invention]

[0005] Fuel cut of the internal combustion engine may be performed when the vehicle is decelerating. If the cooling control is executed during fuel cut when the vehicle is decelerating, the pumping loss of the internal combustion engine decreases as the throttle opening increases. Therefore, if the cooling control is executed during fuel cut when the vehicle is decelerating, the magnitude of engine braking may fluctuate, which may deteriorate drivability. [Means for solving the problem]

[0006] A control device for an on-board internal combustion engine that solves the above problem is a device that controls an on-board internal combustion engine equipped with a filter device that collects particulate matter in the exhaust, and executes cooling control to temporarily increase the throttle opening when the temperature of the filter device becomes equal to or higher than a threshold value during fuel cut of the on-board internal combustion engine, and the amount of increase in the throttle opening in the cooling control and the period of increase are set so that the amount of change in vehicle deceleration accompanying the execution of the cooling control is less than a preset value. Effect of the Invention

[0007] The control device for an on-vehicle internal combustion engine has the effect of suppressing an excessive rise in temperature of the filter device while suppressing deterioration of drivability. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of a control device for an on-vehicle internal combustion engine; [Diagram 2] 4 is a flowchart of a cooling control routine executed by the control device. [Diagram 3] 13 is a time chart showing, when cooling control is being performed, (a) the change in throttle opening, (b) the change in intake air flow rate, (c) the change in filter temperature, (d) the change in accumulated air volume, and (e) the change in vehicle deceleration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of a control device for an on-vehicle internal combustion engine will be described in detail with reference to FIGS. <Configuration of the embodiment> First, the configuration of this embodiment will be described with reference to FIG. 1. As shown in FIG. 1, an on-vehicle internal combustion engine 10 includes an intake passage 11, a combustion chamber 12, and an exhaust passage 13. An air flow meter 14 and a throttle valve 15 are installed in the intake passage 11. The air flow meter 14 is a sensor that detects the flow rate of intake air (intake air flow rate GA) flowing through the intake passage 11. The throttle valve 15 is a valve that adjusts the flow rate of intake air by varying the flow path area of ​​the intake air. The on-vehicle internal combustion engine 10 includes an injector 16 that injects fuel into the intake air. The intake air is introduced into the combustion chamber 12 through the intake passage 11. The injector 16 and an ignition device 17 are installed in the combustion chamber 12. The injector 16 injects fuel into the intake air in the combustion chamber 12 to form a combustible mixture in the combustion chamber 12. The ignition device 17 ignites the mixture in the combustion chamber 12 by spark discharge. Exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber 12 is discharged into the exhaust passage 13. A filter device 18 that collects PM (particulate matter) in the exhaust gas is installed in the exhaust passage 13. The filter device 18 supports an oxidation catalyst.

[0010] The on-board internal combustion engine 10 is controlled by an ECM (Engine Control Module) 20 as a control device. The ECM 20 is an electronic control device that controls the on-board internal combustion engine 10. Detection signals of various sensors installed in various parts of the vehicle are input to the ECM 20. In addition to the above-mentioned air flow meter 14, sensors that output detection signals to the ECM 20 include a crank angle sensor 21, a filter temperature sensor 22, an accelerator sensor 23, and a vehicle speed sensor 24. The crank angle sensor 21 is a sensor that detects a crank angle, which is a rotation phase of the crankshaft 19 of the on-board internal combustion engine 10. The filter temperature sensor 22 is a sensor that detects a filter temperature TF, which is the temperature of the filter device 18. The accelerator sensor 23 is a sensor that detects an accelerator operation amount ACC, which is an amount of depression of an accelerator pedal by a driver of the vehicle. The vehicle speed sensor 24 is a sensor that detects a vehicle speed V, which is a traveling speed of the vehicle. The ECM 20 determines the operation amount of each operation part of the on-board internal combustion engine 10 based on the detection results of these sensors. The ECM 20 controls the vehicle-mounted internal combustion engine 10 by operating each operating part according to the determined operating amount. The operating parts of the vehicle-mounted internal combustion engine 10 operated by the ECM 20 include the throttle valve 15, the injector 16, and the ignition device 17. The operating amounts determined by the ECM 20 include the throttle opening, which is the opening of the throttle valve 15, the amount and timing of fuel injection by the injector 16, and the ignition timing of the air-fuel mixture by the ignition device 17. The ECM 20 calculates the engine speed NE, which is the rotation speed of the vehicle-mounted internal combustion engine 10, based on a detection signal of a crank angle sensor 21.

[0011] <About fuel cut control> As part of the control of the on-board internal combustion engine 10, the ECM 20 executes fuel cut control during vehicle deceleration. The ECM 20 starts fuel cut control when the logical product of the following conditions (A) and (B) is true. Condition (A) is a condition that the accelerator pedal is released. Whether or not this condition is established is determined based on the accelerator depression amount ACC. Condition (B) is a condition that the engine rotation speed NE is equal to or higher than a first speed NthH. In response to the start of fuel cut control, the ECM 20 stops fuel injection from the injector 16 and spark discharge from the ignition device 17.

[0012] During execution of fuel cut control, the ECM 20 ends the fuel cut control when the logical sum of the following conditions (C), (D), and (E) is true. Condition (C) is a condition that the accelerator pedal has been depressed. This condition may be determined to be satisfied when the accelerator depression amount ACC is equal to or greater than a predetermined amount. Condition (D) is a condition that the engine speed NE is equal to or less than a second speed NthL. The second speed NthL is set to a value smaller than the first speed NthH. Condition (E) is a condition that the vehicle speed V is equal to or less than a predetermined speed V1. In response to the end of the fuel cut control, the ECM 20 resumes fuel injection from the injector 16 and spark discharge from the ignition device 17.

[0013] <Cooling control> Next, the cooling control of the filter device 18 executed by the ECM 20 as part of the control of the on-vehicle internal combustion engine 10 will be described with reference to Fig. 2. Fig. 2 shows the procedure of a cooling control routine executed by the ECM 20 for the cooling control. The ECM 20 repeatedly executes this routine at every predetermined control period while the vehicle is in operation.

[0014] When this routine starts, the ECM 20 first determines in step S100 whether or not fuel cut control is being executed. Note that "F / C" in FIG. 2 and FIG. 3 described later stands for fuel cut. If fuel cut control is being executed (YES), the ECM 20 proceeds to step S110. On the other hand, if fuel cut control is not being executed (NO), the ECM 20 ends the processing of this routine for the current control cycle.

[0015] In step S110, the ECM 20 updates the value of the integrated air amount S based on the current detection value of the intake air flow rate GA by the air flow meter 14. Specifically, in step S110, the ECM 20 updates the value of the integrated air amount S so that the updated value is the sum of the current detection value of the intake air flow rate GA and the value before the update. Note that the ECM 20 resets the value of the integrated air amount S to the initial value of "0" when fuel cut control starts.

[0016] Next, in steps S120 to S140, the ECM 20 determines whether or not to execute cooling control. Specifically, the ECM 20 determines to execute cooling control when the logical product of the following conditions (f), (g), and (h) is true. Condition (f) is a condition that the filter temperature TF is equal to or higher than a predetermined threshold value TFh (S120). This condition may be determined based on a detection signal of the filter temperature sensor 22. Condition (g) is a condition that the PM accumulation amount MPM of the filter device 18 is equal to or higher than a predetermined threshold value MPMh (S130). The ECM 20 estimates the PM accumulation amount MPM based on the operating conditions of the on-board internal combustion engine 10. Condition (g) is preferably determined based on the estimation result of the PM accumulation amount MPM. Condition (h) is a condition that the accumulated air amount S is equal to or higher than a predetermined threshold value Sh. The logical product of the condition (f) and the condition (g) being true means that the condition for an increase in the filter temperature TF due to the combustion of the PM accumulated in the filter device 18 is established.

[0017] If the ECM 20 determines that the logical product of the conditions (f), (g), and (h) is true (S120: YES, S130: YES, and S140: YES), the ECM 20 proceeds to step S150. On the other hand, if the ECM 20 determines that the logical product of the conditions (f), (g), and (h) is true (S120: NO, S130: NO, or S140: NO), the ECM 20 ends the processing of this routine in the current control cycle.

[0018] In step S150, the ECM 20 calculates a target opening tTA and a duration Tx based on the filter temperature TF and the PM accumulation amount MPM. In the following step S160, the ECM 20 executes a throttle opening increase process according to the target opening tTA and the duration Tx. Specifically, the ECM 20 increases the throttle opening to the target opening tTA in response to the start of the throttle opening increase process. When the throttle opening reaches the target opening tTA, the ECM 20 holds the throttle opening at the target opening tTA for the duration Tx. Thereafter, the ECM 20 reduces the throttle opening until it becomes an idle opening, which is the original opening during the fuel cut control. When the throttle opening reaches the idle opening, the ECM 20 ends the throttle opening increase process in step S160. The ECM 20 sets the increase speed and decrease speed of the throttle opening in the throttle opening increase process to a predetermined gradual change speed SM.

[0019] After completing the throttle opening increasing process in step S160, the ECM 20 resets the value of the integrated air amount S to 0 in the following step S170. After that, the ECM 20 ends the process of this routine in the current control cycle.

[0020] <Regarding the target opening tTA, duration Tx, gradual change speed SM, and threshold Sh of the cumulative air volume S> In the throttle opening increase process of step S160 in FIG. 2, the throttle opening is temporarily increased during fuel cut control. When the throttle opening increases, the intake flow rate GA increases, and the flow rate of the inflow gas to the filter device 18 also increases. The inflow gas to the filter device 18 during fuel cut control is fresh air that is lower in temperature than the exhaust gas. Therefore, by executing the throttle opening increase process, the amount of heat carried away from the filter device 18 by the inflow gas increases. In this embodiment, such a throttle opening increase process is executed as cooling control for cooling the filter device 18.

[0021] It is considered that the filter device 18 is cooled by such cooling control until the filter temperature TF becomes lower than the combustion temperature of PM. In this case, it is desirable that the target opening tTA and duration Tx are set to larger values ​​as the filter temperature TF is higher. Also, the larger the PM accumulation amount MPM is, the greater the amount of heat generated by the combustion of PM is. Therefore, it is desirable that the target opening tTA and duration Tx are set to larger values ​​as the PM accumulation amount MPM is larger. However, if the throttle opening is increased during fuel cut control, the pumping loss of the on-board internal combustion engine 10 is reduced and engine braking is reduced. Therefore, if cooling control is executed with consideration given only to the cooling of the filter device 18, the vehicle deceleration may fluctuate, resulting in deterioration of drivability.

[0022] In response to this, the ECM 20 sets upper guard values ​​for each of the target opening tTA and the duration Tx. The upper guard values ​​are set so that the amount of change in the vehicle deceleration caused by the execution of the cooling control is less than a preset value. The gradual-change speed SM is also set so that the amount of change in the vehicle deceleration caused by the execution of the cooling control is less than a preset value. The preset value here is a value smaller than the upper limit of the amount of change in the vehicle deceleration at which the deterioration of drivability falls within an acceptable range.

[0023] In addition, even if the deterioration of drivability is within the tolerable range when the cooling control is executed only once, if the cooling control is executed multiple times in a short period of time, the change in the vehicle deceleration may occur such that the deterioration of drivability exceeds the tolerable range. In contrast, in this embodiment, the necessary condition for executing the cooling control is that the condition (H) that the accumulated air amount S is equal to or greater than the predetermined threshold value Sh is true. The threshold value Sh here is set so that even when the cooling control is executed multiple times during one fuel cut control, each cooling control is executed with an interval that is sufficient to make the amount of change in the vehicle deceleration less than the predetermined value.

[0024] In this embodiment, the target opening tTA corresponds to the increase amount of the throttle opening in the cooling control, and the duration Tx corresponds to the period of increase in the throttle opening in the cooling control.

[0025] <Actions and Effects of the Embodiments> Next, the operation of this embodiment will be described with reference to Fig. 3. Fig. 3 shows the manner in which cooling control is performed. Fig. 3(a) shows the transition of the throttle opening, Fig. 3(b) shows the transition of the intake air flow rate GA, Fig. 3(c) shows the transition of the filter temperature TF, Fig. 3(d) shows the transition of the integrated air volume S, and Fig. 3(e) shows the transition of the vehicle deceleration.

[0026] In the case of Fig. 3, fuel cut control is started at time t1. At time t1, the filter temperature TF exceeds the threshold value TFh, and the PM accumulation amount MPM of the filter device 18 exceeds the threshold value MPMh. Therefore, after the start of fuel cut control, the filter temperature TF increases due to the combustion of PM. Then, at time t2 when the integrated air amount S after the start of fuel cut control reaches the threshold value Sh, the process of increasing the throttle opening degree by cooling control is executed.

[0027] The increase in the throttle opening at this time is performed according to the target throttle opening tTA, duration Tx, and gradual change speed SM that are set as described above. Therefore, the change in the vehicle deceleration caused by the execution of the cooling control is suppressed to an amount that keeps the deterioration of drivability within an acceptable range.

[0028] In the case of FIG. 3, even after the cooling control that started at time t2 is terminated, the filter temperature TF continues to rise. Then, the filter temperature TF exceeds the threshold value TFh thereafter. In this case, the cooling control is executed again at time t3 when the accumulated air volume S from time t2 becomes equal to or greater than the threshold value Sh. In this way, when the cooling of the filter device 18 is insufficient by executing the cooling control only once, the filter device 18 is cooled by executing the cooling control multiple times with an interval required to ensure drivability.

[0029] As described above, in the control device for the vehicle-mounted internal combustion engine 10 of this embodiment, the increase amount and the period of the increase in the throttle opening in the cooling control are set so that the change amount of the vehicle deceleration caused by the execution of the cooling control is less than a preset value. Therefore, the control device for the vehicle-mounted internal combustion engine 10 of this embodiment has the effect of suppressing an excessive rise in the temperature of the filter device 18 while suppressing deterioration of drivability.

[0030] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0031] The filter temperature TF may be estimated based on the operating conditions of the on-vehicle internal combustion engine 10, instead of being actually measured. In the above embodiment, the target opening tTA and duration Tx are calculated based on the filter temperature TF and the PM accumulation amount MPM. These calculations may be performed in a different manner. For example, the target opening tTA and duration Tx may be calculated based on only one of the filter temperature TF and the PM accumulation amount MPM. Furthermore, the target opening tTA and duration Tx may be fixed values.

[0032] In the above embodiment, the interval of the cooling control is determined based on the integrated air volume S. The interval of the cooling control may be determined based on a parameter other than the integrated air volume S, such as actual time.

[0033] When the filter temperature TF exceeds the threshold value TFh and becomes even higher, the target opening tTA and the duration Tx may be set so that the amount of change in the vehicle deceleration caused by the execution of the cooling control is equal to or greater than a preset value. In other words, when the urgency of cooling the filter device 18 is high, the filter device 18 may be cooled while allowing the deterioration of drivability. [Explanation of symbols]

[0034] 10. Vehicle internal combustion engine 16 Injector 17 Ignition system 18 Filter device 20 ECM 22 Filter temperature sensor 23 Accelerator sensor

Claims

[Claim 1] A device for controlling an on-vehicle internal combustion engine having a filter device for trapping particulate matter in exhaust gas, comprising: executing a cooling control for temporarily increasing a throttle opening degree when a temperature of the filter device becomes equal to or higher than a threshold value during a fuel cut of the on-board internal combustion engine; The amount of increase in the throttle opening in the cooling control and the period of increase are set so that the amount of change in the vehicle deceleration caused by the execution of the cooling control is less than a preset value. A control device for an internal combustion engine in a vehicle.

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