JP7690890B2 - Hybrid vehicle control device - Google Patents

Description

The present invention relates to a control device for a hybrid vehicle.

Hybrid vehicles are known that are equipped with an engine and a motor as a power source for running, and that start the engine by cranking it with the motor (see, for example, Patent Document 1).

JP 2020-111276 A

By reducing the cranking torque to a degree that does not affect the startability of the engine, the operating range in which the motor can drive can be expanded, improving fuel efficiency. When cranking the engine, the motor needs to output a cranking torque that is sufficient to overcome the rotational resistance torque of the engine. However, the rotational resistance torque of such an engine is not constant, but varies depending on various conditions. Therefore, if the cranking torque is insufficient relative to the rotational resistance torque, the startability of the engine may decrease. On the other hand, if the cranking torque is too large relative to the rotational resistance torque, the operating range in which the motor can drive can be reduced.

The present invention aims to provide a control device for a hybrid vehicle that can appropriately adjust the cranking torque.

The above object can be achieved by a control device for a hybrid vehicle having an engine, a motor provided on a power transmission path between the engine and drive wheels, and a clutch provided on a portion of the power transmission path between the engine and the motor, the control device for the hybrid vehicle including: a first acquisition unit that acquires a correlation value that correlates with an accumulated operating time of the engine; and a first correction unit that corrects the cranking torque required by the motor to crank the engine via the clutch to a greater extent the shorter the accumulated operating time indicated by the correlation value.

The first correction unit may set the correction amount of the cranking torque to 0 when the accumulated operating time indicated by the correlation value is equal to or greater than a predetermined value.

The correlation value may be the cumulative mileage of the hybrid vehicle.

The system may also include a second acquisition unit that acquires the temperature of the clutch lubricant supplied to the clutch, and a second correction unit that corrects the cranking torque to be lower as the temperature of the clutch lubricant decreases.

The system may include a third acquisition unit that acquires atmospheric pressure, and a third correction unit that corrects the cranking torque to be lower the lower the atmospheric pressure.

The system may include a fourth acquisition unit that acquires the temperature of the cooling water that cools the engine, and a fourth correction unit that corrects the cranking torque to a greater extent as the temperature of the cooling water increases.

The system may also include a fifth acquisition unit that acquires the temperature of the engine lubricant supplied to the engine, and a fifth correction unit that corrects the cranking torque to a greater extent as the temperature of the engine lubricant is lower.

The present invention provides a control device for a hybrid vehicle that can appropriately adjust the cranking torque.

FIG. 1 is a schematic diagram of a hybrid vehicle. FIG. 2 is a map showing the relationship between the torque and the rotation speed of the motor. FIG. 3 is a flowchart showing an example of the cranking torque correction control. 4A and 4B are maps for calculating the correction amount. 5A and 5B are maps for calculating the correction amount. FIG. 6 is a map for calculating the correction amount.

[General configuration of hybrid vehicle]
1 is a schematic diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and a transmission 19 are provided in this order in a power transmission path from an engine 10 to drive wheels 13. The engine 10 and the motor 15 are mounted as a power source for driving the hybrid vehicle 1. The engine 10 is, for example, a V6 gasoline engine, but the number of cylinders is not limited thereto, and may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, the torque converter 18, and the transmission 19 are provided in a transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drive-coupled via a differential 12.

The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 receives a supply of hydraulic pressure from a released state and enters an engaged state, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 enters a released state in response to the cessation of the hydraulic pressure supply and cuts off the power transmission between the engine 10 and the motor 15. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotation speed. The released state is a state in which both engagement elements of the K0 clutch 14 are separated.

The motor 15 is connected to the battery 16 via the inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16, and also functions as a generator that generates power to charge the battery 16 in response to power transmission from the engine 10 and the drive wheels 13. The power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

The inverter 17 is controlled by the ECU 100 described below, and converts the DC voltage from the battery 16 to an AC voltage, or converts the AC voltage from the motor 15 to a DC voltage. In the case of power running in which the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 to an AC voltage and adjusts the power supplied to the motor 15. In the case of regenerative running in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 to a DC voltage and adjusts the power supplied to the battery 16.

The torque converter 18 is a fluid coupling with a torque amplification function. The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by changing the gear stage, but is not limited to this and may be a continuously variable automatic transmission. The transmission 19 is provided between the motor 15 and the drive wheels 13 on the power transmission path. The motor 15 and the transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that receives a supply of hydraulic pressure and enters an engaged state to directly connect the motor 15 and the transmission 19.

The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures. A wet clutch may be provided instead of the torque converter 18.

The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 for the hybrid vehicle. The ECU 100 is an electronic control unit that includes a calculation processing circuit that performs various calculation processes related to the vehicle's driving control, and a memory that stores control programs and data. The ECU 100 is an example of a control device for a hybrid vehicle, and functionally realizes the first to fifth acquisition units and the first to fifth correction units, which will be described in detail later.

The ECU 100 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the rotation speed and torque of the motor 15 by controlling the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16. The ECU 100 also controls the operation of the K0 clutch 14, the lock-up clutch 20, and the transmission 19 through the control of the hydraulic control mechanism 22.

The ECU 100 receives signals from an ignition switch 71, a crank angle sensor 72, a mileage sensor 73, an AT oil temperature sensor 74, an atmospheric pressure sensor 75, a water temperature sensor 76, and an engine oil temperature sensor 77. The crank angle sensor 72 detects the rotation speed of the crankshaft of the engine 10. The mileage sensor 73 detects the mileage of the hybrid vehicle 1. The AT oil temperature sensor 74 detects the temperature of the lubricating oil supplied to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20. The atmospheric pressure sensor 75 detects the atmospheric pressure. The water temperature sensor 76 detects the temperature of the cooling water that cools the engine 10. The engine oil temperature sensor 77 detects the temperature of the lubricating oil that lubricates the drive parts of the engine 10.

The ECU 100 runs the hybrid vehicle in either the motor mode or the hybrid mode. In the motor mode, the ECU 100 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. The hybrid mode includes a mode in which the vehicle runs using only the power of the engine 10, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 10 and the motor 15 as power sources.

The driving mode is switched based on the vehicle's required driving force, which is calculated from the vehicle speed and accelerator opening, and the state of charge of the battery 16. For example, when the required driving force is relatively small and the SOC (State of Charge), which indicates the amount of charge stored in the battery 16, is relatively high, the motor mode, in which the engine 10 is stopped, is selected to improve fuel efficiency. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the hybrid mode, in which the engine 10 is driven, is selected.

The ECU 100 executes intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is met, and to restart the automatically stopped engine 10 when a predetermined restart condition is met. For example, when the accelerator opening becomes zero in the hybrid mode, the ECU 100 automatically stops the engine 10, assuming that the automatic stop condition is met. Also, when the accelerator opening becomes greater than zero, for example, the ECU 100 automatically restarts the engine 10, assuming that the restart condition is met. When automatically stopping, the ECU 100 releases the K0 clutch 14 to stop combustion. When automatically restarting, the ECU 100 cranks the engine 10 by the motor 15 via the K0 clutch 14 to start combustion, and then engages the K0 clutch 14.

Figure 2 is a map showing the relationship between the torque and rotation speed of the motor 15. The vertical axis shows the torque of the motor 15, and the horizontal axis shows the rotation speed of the motor 15. The solid line in Figure 2 shows the maximum torque that the motor 15 can output. When the rotation speed of the motor 15 is low, the maximum torque is high, and as the rotation speed of the motor 15 increases, the maximum torque decreases. Here, the motor 15 must always secure the cranking torque required to crank the engine 10 described above as surplus torque. For this reason, the operating range in which driving in motor mode is possible is the range obtained by dividing the cranking torque by the maximum torque.

The wider the driving range in motor mode, the more the frequency of engine 10 operation can be reduced, improving fuel efficiency. For this reason, it is preferable that the cranking torque is as low as possible without affecting the startability of engine 10. When cranking engine 10, motor 15 needs to output a cranking torque that is sufficient to overcome the rotational resistance torque that acts as a resistance to the rotation of engine 10. The rotational resistance torque of engine 10 is not constant, but fluctuates depending on various conditions. In this embodiment, ECU 100 executes cranking torque correction control to respond to such fluctuations in the rotational resistance torque of engine 10.

[Cranking torque correction control]
3 is a flow chart showing an example of the cranking torque correction control. This control is repeatedly executed while the ignition is on and the engine 10 is stopped, but is not limited thereto, and may be executed only when there is a request to start the engine 10. First, the ECU 100 obtains a basic cranking torque (step S1). The basic cranking torque is a torque that can appropriately crank the engine 10, which is obtained in advance by an experiment. The basic cranking torque may be a variable value that varies depending on the stop position of the engine 10, for example, or may be a predetermined fixed value.

The ECU 100 acquires the accumulated mileage, AT oil temperature, atmospheric pressure, coolant temperature, and engine oil temperature based on the detection values of the mileage sensor 73, AT oil temperature sensor 74, atmospheric pressure sensor 75, water temperature sensor 76, and engine oil temperature sensor 77 (step S2). Step S2 is an example of the process executed by the first to fifth acquisitions.

The ECU 100 corrects the cranking torque based on the acquired cumulative mileage, etc. (step S3). Step S3 is an example of the processing executed by the first to fifth correction units. Specifically, the cranking torque is corrected by adding or subtracting a predetermined correction amount to the basic cranking torque described above. The method of calculating the correction amount is described below.

[Method of calculating correction amount]
The ECU 100 calculates a plurality of correction amounts by referring to the maps shown in Figures 4A to 6. Figures 4A to 6 are maps for calculating the correction amounts. The maps shown in Figures 4A to 6 are defined based on experimental results and are stored in the memory of the ECU 100.

Figure 4A is an example of a map that specifies the relationship between the accumulated mileage and the correction amount. The vertical axis indicates the correction amount [N·m], and the horizontal axis indicates the accumulated mileage [km] of the hybrid vehicle 1. The correction amount increases from 0 as the accumulated mileage decreases within a range in which the accumulated mileage is equal to or less than a predetermined value. The reason for this is as follows. A short accumulated mileage is almost synonymous with a short accumulated operating time of the engine 10, and the accumulated mileage is a correlation value that correlates with the accumulated operating time of the engine 10. Here, when the engine 10 is new, the mechanical friction torque (hereinafter referred to as friction torque), which is the rotational resistance torque of the engine 10, is large. As the accumulated operating time of the engine 10 increases, the friction torque corresponding to the accumulated operating time decreases, and after the so-called break-in operation is completed, the friction torque corresponding to the accumulated operating time becomes 0. The motor 15 requires a cranking torque that is sufficient to overcome the friction torque of the engine 10 that varies depending on the accumulated operating time.

Since the friction torque of the engine 10 varies depending on the accumulated mileage, the cranking torque can be appropriately adjusted by calculating the correction amount based on the accumulated mileage.

As described above, the cumulative mileage is a correlation value that correlates with the cumulative operating time of the engine 10. For example, since the engine 10 is generally stopped during driving in the motor mode, the cumulative mileage increases but the cumulative operating time of the engine 10 does not increase. Therefore, as the cumulative driving time in the motor mode increases, the cumulative mileage increases but the cumulative operating time of the engine 10 does not increase. However, if the power of the battery 16 becomes insufficient while driving in the motor mode, the engine 10 is driven and the vehicle is switched to driving in the hybrid mode. Therefore, it is difficult to always drive in the motor mode, and as a result, the cumulative mileage correlates with the cumulative operating time of the engine 10.

Figure 4B is an example of a map that specifies the relationship between the AT oil temperature and the correction amount. The vertical axis indicates the correction amount [N·m], and the horizontal axis indicates the AT oil temperature [°C]. As the AT oil temperature increases, the correction amount gradually increases from a negative value to a positive value. The reason for this is as follows. The AT oil temperature is the temperature of the lubricating oil supplied to the K0 clutch 14, and the K0 clutch 14 is a wet clutch. Therefore, the lower the AT oil temperature, the higher the viscosity of this lubricating oil becomes, and the amount of torque transmitted from the motor 15 to the engine 10 via the K0 clutch 14 increases. In other words, the lower the AT oil temperature, the greater the torque transmitted from the motor 15 to the engine 10 via the K0 clutch 14.

Since the AT oil temperature is affected by the outside air temperature, by calculating the correction amount based on the AT oil temperature, the effect of the outside air temperature can be suppressed and the cranking torque can be appropriately adjusted.

Figure 5A is an example of a map that specifies the relationship between atmospheric pressure and the correction amount. The vertical axis indicates the correction amount [N·m], and the horizontal axis indicates the atmospheric pressure [kPa]. When the atmospheric pressure is near the standard atmospheric pressure, the correction amount is 0, and when the atmospheric pressure further decreases from a predetermined value lower than the standard atmospheric pressure, the correction amount decreases from 0. Also, when the atmospheric pressure further increases from a predetermined value higher than the standard atmospheric pressure, the correction amount increases from 0. The reason for this is as follows. The higher the atmospheric pressure, the greater the amount of air filled into each cylinder of the engine 10 during cranking, and the lower the atmospheric pressure, the smaller the amount of air filled into each cylinder. Here, the compression torque due to the repulsive force that pushes back the piston that rises during the compression stroke is the rotational resistance torque of the engine 10, and the magnitude of the compression torque is proportional to the amount of air in the cylinder. This is because a cranking torque that is sufficient to overcome this compression torque is required during cranking.

Since atmospheric pressure varies depending on altitude and weather, by calculating the correction amount based on atmospheric pressure, it is possible to appropriately adjust the cranking torque while taking such environmental changes into account.

Figure 5B is an example of a map that specifies the relationship between the coolant temperature and the correction amount. The vertical axis indicates the correction amount [N·m], and the horizontal axis indicates the coolant temperature [°C]. The higher the coolant temperature is above a predetermined value, the larger the correction amount becomes. This is because when the coolant temperature becomes high enough to be above a predetermined value, the sliding parts of the engine 10 expand, and the friction torque of the engine 10 increases. For example, when the engine 10 is restarted in a short time after being automatically stopped, the coolant temperature is still high, so the cranking torque can be appropriately adjusted by calculating the correction amount based on the coolant temperature.

Figure 6 is an example of a map that specifies the relationship between engine oil temperature and the correction amount. The vertical axis indicates the correction amount [N·m], and the horizontal axis indicates the engine oil temperature [°C]. As the engine oil temperature drops below a predetermined value, the correction amount increases from 0. This is because the lower the engine oil temperature, the higher the viscosity becomes, and the greater the friction torque of the engine 10. For example, before the engine 10 has finished warming up, the engine oil temperature is low, so by calculating the correction amount based on the engine oil temperature, the cranking torque can be appropriately adjusted even before the engine 10 has finished warming up.

The cranking torque is corrected by adding all the correction amounts calculated in the above maps to the basic cranking torque. In this way, the cranking torque can be adjusted to correspond to the rotational resistance torque of the engine 10, which fluctuates for various reasons.

In this embodiment, the correction amount is calculated based on the accumulated mileage as shown in FIG. 4A, but the present invention is not limited to this. For example, the correction amount may be calculated based on the accumulated operating time of the engine 10. In this case, as in the example of FIG. 4A, the correction amount increases from 0 as the accumulated operating time becomes shorter within a range in which the accumulated operating time is equal to or less than a predetermined value. In addition, while the accumulated mileage is generally measured by a mileage sensor in many vehicles, there are few vehicles equipped with a device for measuring the accumulated operating time of the engine 10. For this reason, calculating the correction amount based on the accumulated mileage of the vehicle is more versatile than calculating the correction amount based on the accumulated operating time of the engine 10.

In Figures 4A to 6, the correction amount changes linearly, but this is not limited thereto, and the correction amount may change in a curved manner or in a stepwise manner.

In this embodiment, the cranking torque is corrected by adding a correction amount defined from various viewpoints to the basic cranking torque, but this is not limiting. For example, the cranking torque may be corrected by multiplying the basic cranking torque by a correction coefficient defined from various viewpoints.

In this embodiment, the cranking torque is corrected based on a map, but this is not limiting. For example, the cranking torque may be corrected using an arithmetic formula that uses the basic cranking torque, the accumulated mileage, the AT oil temperature, the atmospheric pressure, the coolant temperature, and the engine oil temperature as arguments.

In this embodiment, the cranking torque is corrected based on the accumulated mileage, AT oil temperature, atmospheric pressure, coolant temperature, and engine oil temperature. However, it is not necessary to correct the cranking torque based on all of these. For example, depending on the use of the vehicle, it may be limited to use in an environment where the AT oil temperature, atmospheric pressure, coolant temperature, and engine oil temperature do not change significantly. Also, depending on the type of engine, the amount of heat dissipated by the engine is relatively small, and the coolant temperature and engine oil temperature do not change significantly. In such cases, the cranking torque may be corrected based only on the accumulated mileage.

In the above embodiment, a hybrid vehicle is controlled by a single ECU 100, but this is not limited to the above. For example, the above-mentioned control may be performed by multiple ECUs, such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

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 described in the claims.

1 Hybrid vehicle 10 Engine 14 K0 clutch (clutch)
15 Motor 100 ECU (first to fifth acquisition units, first to fifth correction units)

Claims (7)

A control device for a hybrid vehicle having an engine, a motor provided on a power transmission path between the engine and drive wheels, and a clutch provided on a portion of the power transmission path between the engine and the motor,
A first acquisition unit that acquires a correlation value that correlates with an integrated operating time of the engine;
a first correction unit that corrects the cranking torque required by the motor to crank the engine via the clutch so that the shorter the integrated operating time indicated by the correlation value, the greater the correction torque. 2. The control device for a hybrid vehicle according to claim 1, wherein the first correction unit sets the correction amount of the cranking torque to zero when the integrated operating time indicated by the correlation value is equal to or greater than a predetermined value. The control device for a hybrid vehicle according to claim 1 or 2, wherein the correlation value is an accumulated mileage of the hybrid vehicle. A second acquisition unit that acquires a temperature of the clutch lubricant supplied to the clutch;
a second correction unit that corrects the cranking torque to be lower as the temperature of the clutch lubricant oil is lower;
3. The control device for a hybrid vehicle according to claim 1 or 2, comprising: A third acquisition unit that acquires atmospheric pressure;
a third correction unit that corrects the cranking torque to be lower as the atmospheric pressure is lower;
5. The control device for a hybrid vehicle according to claim 1, further comprising: A fourth acquisition unit that acquires a temperature of a cooling water that cools the engine;
a fourth correction unit that corrects the cranking torque to a larger value as the temperature of the cooling water increases;
6. The control device for a hybrid vehicle according to claim 1, further comprising: A fifth acquisition unit that acquires a temperature of engine lubricating oil supplied to the engine;
7. The control device for a hybrid vehicle according to claim 1, further comprising a fifth correction unit that corrects the cranking torque to a larger value as the temperature of the engine lubricating oil decreases.

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