JP7740172B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

In a vehicle equipped with a clutch in the power transmission path between the engine and the transmission, a technique is known for determining engine misfire abnormalities based on engine rotation fluctuations (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2021-024369

From the perspective of protecting components, it is possible to perform a fail-safe process that disengages the clutch before a misfire is determined to have occurred. By disengaging the clutch, the impact of engine rotation fluctuations on the transmission, which is located downstream of the clutch, can be reduced. However, the amount of engine rotation fluctuation that occurs when a misfire occurs differs between when the fail-safe process, in which the clutch is disengaged, is being performed and when the fail-safe process is stopped. This may prevent accurate determination of a misfire abnormality.

The present invention therefore aims to provide a vehicle control device that can accurately detect misfire abnormalities.

The above objective can be achieved by a vehicle control device equipped with a clutch on a power transmission path between an engine and a transmission, the vehicle control device comprising: a counting unit that counts a misfire counter indicating the number of misfires of the engine when the rotational fluctuation amount of the engine is greater than a threshold value; an execution unit that executes failsafe processing to release the clutch when the misfire counter is greater than a first determination value; a determination unit that determines a misfire abnormality in the engine when the misfire counter is greater than a second determination value that is greater than the first determination value; and a setting unit that sets the threshold value during execution of the failsafe processing to a value higher than the threshold value during stoppage of the failsafe processing.

The vehicle may include a first motor provided between the engine and the clutch, a second motor arranged on a power transmission path different from the power transmission path, and a battery that is charged with power generated by the first motor and supplies power to the second motor, and the execution unit may, as the fail-safe processing, cause the engine to perform regenerative operation of the first motor to charge the battery while driving the vehicle using the second motor.

The vehicle may include a motor provided on the power transmission path between the clutch and the transmission, and the execution unit may run the vehicle using the motor as the fail-safe processing.

The present invention provides a vehicle control device that can accurately detect misfire abnormalities.

FIG. 1 is a schematic diagram of a hybrid vehicle. FIG. 2 is a flowchart showing an example of misfire counter update control executed by the ECU. FIG. 3 is a flowchart showing an example of misfire abnormality determination control executed by the ECU.

[General configuration of hybrid vehicle]
FIG. 1 is a schematic diagram of a hybrid vehicle 10. The hybrid vehicle 10 includes an engine 200, a front motor 220, and a rear motor 270 as driving power sources. The engine 200 is a gasoline engine or a diesel engine. The front motor 220 and the rear motor 270 receive electric power from a battery 310 (described later) via power conversion devices 300 and 320, respectively, to drive them. The front motor 220 also generates electric power by regenerating using the power of the engine 200. The rear motor 270, described in more detail later, drives the hybrid vehicle 10. The front motor 220 and the rear motor 270 are arranged on different power transmission paths.

A K0 clutch 210 is provided between the engine 200 and the front motor 220. The K0 clutch 210 engages, slips, and disengages the engine 200 and the front motor 220. A WSC (Wet Start Clutch) clutch 230 is provided between the front motor 220 and the transmission 240. The WSC clutch 230 engages, slips, and disengages the front motor 220 and the transmission 240. The K0 clutch 210 and the WSC clutch 230 are switched between engagement, slip, and disengagement according to the hydraulic pressure supplied from a hydraulic control device (not shown).

Transmission 240 is a transmission that switches between multiple gear ratios, such as five forward speeds and one reverse speed. The gear ratio is switched depending on, for example, vehicle speed or accelerator pedal position. WSC clutch 230 is provided separately from transmission 240, but some of the multiple friction engagement elements engaged in each gear of transmission 240 may be used. Note that a lock-up clutch provided in a torque converter may be used instead of WSC clutch 230.

The output shaft of the transmission 240 is connected to the front drive wheels 251 and 252 via a propeller shaft 245, a differential 250, a right drive shaft 261, and a left drive shaft 262. The output shaft of the rear motor 270 is connected to the rear drive wheels 253 and 254 via a propeller shaft 275, a differential 280, a right drive shaft 291, and a left drive shaft 292.

Each of the power conversion devices 300 and 320 includes an inverter and a converter, and converts DC power from the battery 310 into AC current and outputs it to the front motor 220 and the rear motor 270, respectively. This allows the front motor 220 and the rear motor 270 to be driven. Furthermore, the power conversion devices 300 and 320 also convert AC power generated by the front motor 220 and the rear motor 270, respectively, into DC current and output it to the battery 310, thereby charging the battery 310. The battery 310 is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery.

The ECU (Electronic Control Unit) 100 is an electronic control unit that includes a processing circuit that performs various calculations related to the driving control of the hybrid vehicle 10, and a memory that stores control programs and data. The ECU 100 is an example of a vehicle control device, and functionally implements a counting unit, an execution unit, a determination unit, and a setting unit, which will be described in detail below. The ECU 100 is electrically connected to an ignition switch 510, a crank angle sensor 520, and an SOC sensor 530.

The ignition switch 510 detects the on/off state of the ignition. The crank angle sensor 520 detects the rotational speed of the crankshaft of the engine 200. The SOC sensor 530 detects the remaining charge (SOC: State Of Charge) of the battery 310. Note that the ECU 100 may obtain the remaining charge of the battery 310 by estimating it using a known method without using an SOC sensor.

Figure 2 is a flowchart showing an example of misfire counter update control executed by ECU 100. The flowchart shown in Figure 2 is continuously repeated while the ignition is on. ECU 100 determines whether the magnitude of engine rotation fluctuation of engine 200 is greater than a threshold value (step S1). The rotation fluctuation is calculated, for example, as follows, based on the detection value of crank angle sensor 520. The rotation fluctuation is the difference between the rotation speeds over a predetermined angular interval that includes only one compression top dead center, subtracting the value for the cylinder whose compression top dead center occurs first from the value for the cylinder whose compression top dead center occurs last, out of a pair of cylinders whose compression top dead center occurrence timings are adjacent in chronological order. If no misfire is occurring, the rotation fluctuation will be close to zero. If a misfire is occurring, the rotation fluctuation will be a large value.

If the answer is Yes in step S1, the ECU 100 increments the misfire counter by "1" (step S2). If the answer is No in step S1, the ECU 100 resets the misfire counter to "0" (step S3). In this way, the ECU 100 updates the value of the misfire counter, which indicates the number of misfires that have occurred. Steps S2 and S3 are examples of processing executed by the counting unit.

Figure 3 is a flowchart showing an example of misfire abnormality detection control executed by ECU 100. The flowchart shown in Figure 3 is continuously repeated while the ignition is on. ECU 100 determines whether the misfire counter is greater than a first determination value (step S11). If the answer is Yes in step S11, ECU 100 turns on the failsafe execution flag (step S12) and executes failsafe processing (step S13).

As a fail-safe process, the ECU 100 disengages the WSC clutch 230 while driving the vehicle using the rear motor 270, and causes the engine 200 to perform regenerative operation of the front motor 220. By disengaging the WSC clutch 230, the effects of rotation fluctuations due to misfires in the engine 200 can be prevented from being transmitted to the transmission 240 and propeller shaft 245, thereby protecting components such as the transmission 240. Furthermore, the rear motor 270 can ensure the hybrid vehicle 10's driving. Furthermore, the regenerative operation of the front motor 220 can charge the battery 310. This allows the rear motor 270 to be driven using the charged power of the battery 310, enabling the hybrid vehicle 10 to continue driving. Step S13 is an example of processing executed by the execution unit. The front motor 220 is an example of a first motor, and the rear motor 270 is an example of a second motor.

If step S11 is No or after step S13 has been executed, the ECU 100 determines whether the failsafe execution flag is ON (step S14). If step S14 is No, i.e., if the failsafe process is stopped and the WSC clutch 230 is engaged, the ECU 100 sets the threshold to value α (step S15). If step S14 is Yes, i.e., if the failsafe process is being executed and the WSC clutch 230 is released, the ECU 100 sets the threshold to value β (step S16). Value β is greater than value α. The values α and β will be described in more detail below. Steps S15 and S16 are an example of processing executed by the setting unit.

Next, ECU 100 determines whether the misfire counter is greater than a second determination value (step S17). The second determination value is greater than the first determination value described above. If the answer is No in step S17, ECU 100 determines that the misfire in engine 200 is within the normal range and determines that combustion is normal (step S18). If the answer is Yes in step S17, ECU 100 determines that the misfire in engine 200 is beyond the normal range and determines that a misfire abnormality exists (step S19). For example, if a misfire abnormality is determined, ECU 100 may turn on a Malfunction Indicator Light (MIL) to notify the driver that a misfire abnormality has occurred in engine 200. Step S19 is an example of processing executed by the determination unit.

As described above, because the second determination value is greater than the first determination value, failsafe processing is executed (step S13) before a misfire abnormality determination (step S19) is made in the engine 200. Therefore, execution of the failsafe processing takes priority over a misfire abnormality determination, and priority is given to releasing the WSC clutch 230, thereby protecting components such as the transmission 240.

The threshold value when failsafe processing is being executed is set to a value β that is higher than the value α, which is the threshold value when failsafe processing is not being executed (step S16). When the WSC clutch 230 is engaged, the engine 200 and transmission 240 are connected, so the amount of rotational fluctuation due to misfire is small. In contrast, when the WSC clutch 230 is disengaged, the engine 200 and transmission 240 are disconnected, so the amount of rotational fluctuation due to misfire increases. By switching the threshold value in this way, the misfire counter can be counted accurately regardless of whether failsafe processing is being executed, thereby enabling accurate determination of misfire abnormalities.

In this embodiment, the hybrid vehicle is controlled by a single ECU 100, but this is not limiting. For example, the above-described control may be performed by multiple ECUs, such as an engine ECU that controls the engine 200, a front motor ECU that controls the front motor 220, a rear motor ECU that controls the rear motor 270, a clutch ECU that controls the WSC clutch 230, and a battery ECU that controls the battery 310.

In the above embodiment, the engine 200 and front motor 220 drive the front wheels, and the rear motor 270 drives the rear wheels, but this is not limited to this. For example, the engine and first motor may drive the rear wheels, and the second motor may drive the front wheels.

In the above embodiment, a hybrid vehicle 10 equipped with a front motor 220 and a rear motor 270 has been described as an example, but this is not limiting. For example, a hybrid vehicle without a rear motor 270 may also be used. In this case, as a fail-safe process, the K0 clutch 210 between the engine 200 and the front motor 220 may be released, and the vehicle may continue to run using the front motor 220 via the WSC clutch 230. This allows a hybrid vehicle without a rear motor 270 to continue running as a fail-safe process. Note that in this case, the hybrid vehicle is not limited to one in which the front wheels are driven by the engine 200 and the front motor 220, and may also be one in which the rear wheels are driven by an engine and a motor.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims.

10 Hybrid vehicle 100 ECU (vehicle control device, counting unit, execution unit, determination unit, setting unit)
200 Engine 210 K0 Clutch 220 Front Motor (First Motor)
230 WSC clutch 240 Transmission 270 Rear motor (second motor)
300, 320 Power conversion device 310 Battery

Claims (1)

A control device for a vehicle having a clutch on a power transmission path between a four-cylinder engine and a transmission,
a counting unit that counts a misfire counter indicating the number of misfires of the engine when a rotation fluctuation amount of the engine is greater than a threshold value;
an execution unit that executes a fail-safe process to release the clutch when the misfire counter is greater than a first determination value;
a determination unit that determines that a misfire abnormality has occurred in the engine when the misfire counter is greater than a second determination value that is greater than the first determination value;
a setting unit that sets the threshold value during execution of the fail-safe process to a value higher than the threshold value during suspension of the fail-safe process ,
the vehicle includes a first motor provided between the engine and the clutch, a second motor disposed on a power transmission path different from the power transmission path, and a battery that is charged with power generated by the first motor and supplies power to the second motor;
the execution unit causes the engine to perform regenerative operation of the first motor to charge the battery while causing the vehicle to run using the second motor as the fail-safe processing;
the rotational fluctuation amount is a difference between a rotational speed value at a predetermined angular interval including only one compression top dead center in a pair of cylinders adjacent in time series in which the compression top dead center occurs first and a rotational speed value at a cylinder whose compression top dead center occurs later,
the clutch is provided between the first motor and the transmission on the power transmission path between the engine and the transmission,
A vehicle control device that, when it is determined that a misfire abnormality has occurred in the engine, lights up an MIL to notify the driver that a misfire abnormality has occurred in the engine .