Hybrid vehicles

Abstract

To provide a hybrid vehicle that ensures the transition to motor-driven travel while suppressing hesitation.SOLUTION: A control device which switches between engine-driven hybrid travel with a clutch engaged and motor-driven travel with the clutch released: calculates a predicted upper limit which is an output upper limit of a battery when an engine is started by a motor during the hybrid travel; sets a determination value on the basis of the predicted upper limit; determines that transition to motor-driven travel is prohibited when a vehicle speed during the hybrid travel exceeds a determination value; and permits transition to the motor-driven travel when the vehicle speed is equal to or less than the determination value. A setting section sets the vehicle speed which results in a sufficient output value to reach the predicted upper limit as the determination value. The determination value is obtained by adding a predetermined margin value which decreases as the vehicle speed decreases to a required output value. The required output value is a battery's output value per unit time at each vehicle speed capable of maintaining the motor-driven travel when the engine start-up is completed and decreases as the vehicle speed decreases.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle.

Background Art

[0002] There is a hybrid vehicle that switches between hybrid driving powered by an engine and motor driving powered by a motor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When shifting from motor driving to hybrid driving, the engine is cranked by the motor, which is the driving power source, to start the engine. Here, depending on the output upper limit value of the battery, there is a possibility that the power of the motor is insufficient when starting the engine, resulting in hesitation where the acceleration of the hybrid vehicle decreases. Therefore, when the output upper limit value of the battery during hybrid driving is low, it may be considered to disallow the shift from hybrid driving to motor driving and continue hybrid driving. However, if the frequency of disallowing the shift to motor driving increases, the driving time of the engine becomes long, which may deteriorate fuel consumption and exhaust emissions.

[0005] Therefore, an object of the present invention is to provide a hybrid vehicle that suppresses hesitation and ensures a shift to motor driving.

Means for Solving the Problems

[0006] The above objective is to provide an engine, a clutch positioned on the power transmission path from the engine to the wheels, a motor positioned on the power transmission path from the clutch to the wheels and capable of starting the engine by cranking the engine with the clutch engaged, a battery that outputs power to the motor, and a control device that switches between hybrid driving, in which the vehicle is driven by the engine with the clutch engaged, and motor driving, in which the vehicle is driven by the motor with the clutch disengaged, wherein the control device includes a calculation unit that calculates a predicted upper limit value, which is a predicted value of the upper limit of the battery output when the engine is started by the motor during motor driving, and the predicted upper limit The system includes a setting unit that sets a judgment value based on a limit value, and a decision unit that decides not to allow the transition to motor driving when the vehicle speed during hybrid driving is higher than the judgment value, and decides to allow the transition to motor driving when the vehicle speed during hybrid driving is less than or equal to the judgment value, wherein the setting unit sets the vehicle speed at which the sufficient output value becomes the predicted upper limit value as the judgment value, the sufficient output value is the value obtained by adding a predetermined margin value to the required output value, the required output value is the output value of the battery per unit time for each vehicle speed at which driving can be maintained by the motor when the engine has finished starting, the required output value decreases as the vehicle speed decreases, and the margin value decreases as the vehicle speed decreases, which can be achieved by a hybrid vehicle.

[0007] The system includes a transmission located on the power transmission path from the motor to the wheel, and the margin value may decrease as the gear ratio in the transmission increases.

[0008] The calculation unit may calculate the predicted upper limit based on the State of Charge (SOC) of the battery and the amount of power consumed by the battery from the start to the completion of starting the engine by the motor.

[0009] The calculation unit may calculate the power consumption based on the rotational speed of the motor during hybrid driving, the torque of the motor required for motor driving at the rotational speed of the motor, the cranking torque required for cranking the engine by the motor, and the cranking period, which is the period from when the motor starts cranking the engine until combustion starts in the engine. [Effects of the Invention]

[0010] This allows us to provide hybrid vehicles that ensure a smooth transition to motor-only driving while suppressing hesitation. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of a hybrid vehicle. [Figure 2] Figure 2 is a flowchart illustrating motor-driven transition control. [Figure 3] Figure 3A is an example of a map defining the relationship between vehicle speed and battery output value in this embodiment, and Figure 3B is an example of a map defining the relationship between vehicle speed and battery output value in a comparative example. [Figure 4] Figure 4 is an example diagram of a map that defines the relationship between vehicle speed and battery output value in a modified example. [Figure 5] Figure 5 is a flowchart illustrating the control of the calculation of the predicted upper limit. [Figure 6] Figure 6 is an example of a map that defines the upper limit of output according to the battery's SOC and temperature. [Modes for carrying out the invention]

[0012] [Overview of Hybrid Vehicle Configuration] Figure 1 is a schematic diagram of the hybrid vehicle 1. The hybrid vehicle 1 has a power transmission path from the engine 10 to the drive wheels 70, in which a clutch 30, a motor 40, and a transmission 50 are provided in that order. The engine 10 and motor 40 are mounted as the drive source for the hybrid vehicle 1. The engine 10 is, for example, a gasoline engine, but it may also be a diesel engine. The transmission 50 and the left and right drive wheels 70 are connected via a differential gear 60. The transmission 50 includes a torque converter 51 and an automatic transmission 52. The automatic transmission 52 is a stepped transmission, but it may also be a continuously variable transmission.

[0013] The clutch 30 is located between the engine 10 and the motor 40 on the same power transmission path. The clutch 30 engages from a disengaged state when hydraulic pressure is supplied, connecting the power transmission between the engine 10 and the motor 40. The clutch 30 disengages when the hydraulic pressure supply is stopped, interrupting the power transmission between the engine 10 and the motor 40.

[0014] The motor 40 is connected to the battery 90 via the PCU 80. The motor 40 functions as a power source for the hybrid vehicle 1 in response to power supplied from the battery 90. Furthermore, the motor 40 also functions as a generator that charges the battery 90 in response to power transmission from the engine 10 and the drive wheels 70. The motor 40 can start the engine 10 by cranking the engine 10 with the clutch 30 engaged.

[0015] The PCU80 is controlled by the ECU100, which will be described later. In the case of powered operation where the motor 40 outputs torque, the PCU80 converts the DC voltage of the battery 90 to an AC voltage and adjusts the power supplied to the motor 40. In the case of regenerative operation where the motor 40 generates electricity, the PCU80 converts the AC voltage from the motor 40 to a DC voltage and adjusts the regenerative power supplied to the battery 90.

[0016] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 as a control device for the vehicle. The ECU 100 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to the running control of the vehicle, and a memory in which control programs and data are stored. The ECU 100 is an example of a control device for the hybrid vehicle 1. The ECU 100 functionally realizes a calculation unit, a setting unit, and a determination unit, which will be described in detail later.

[0017] An oil temperature sensor 11, a rotation speed sensor 41, a SOC sensor 91, and a temperature sensor 92 are electrically connected to the ECU 100. The oil temperature sensor 11 detects the temperature of the lubricating oil of the engine 10. The rotation speed sensor 41 detects the rotation speed of the motor 40. The SOC sensor 91 detects the SOC (State of Charge) of the battery 90. The temperature sensor 92 detects the temperature of the battery 90. In the case where the SOC sensor 91 is not provided, the ECU 100 may calculate the SOC based on the current value and voltage value of the battery 90.

[0018] The ECU 100 drives the hybrid vehicle 1 either in motor drive or hybrid drive. In motor drive, the ECU 100 stops the engine 10, disengages the clutch 30, and runs by the power of the motor 40. In hybrid drive, the clutch 30 is engaged and the vehicle runs at least by the power of the engine 10. Also, in hybrid drive, the output of the motor 40 can assist the driving of the engine 10.

[0019] The switching between motor drive and hybrid drive is performed based on the required torque for the hybrid vehicle 1 obtained from the vehicle speed and the accelerator opening. For example, when the required torque is less than the starting threshold for starting the engine 10, motor drive with the engine 10 stopped is selected to improve fuel efficiency. When the required torque is greater than or equal to the starting threshold for starting the engine 10, hybrid drive with the engine 10 started is selected.

[0020] [Motor Drive Transition Control] Figure 2 is a flowchart illustrating motor driving transition control. The ECU 100 determines whether the hybrid vehicle 1 is in hybrid driving (step S1). If the answer in step S1 is No, this control ends.

[0021] If the answer in step S1 is Yes, the ECU 100 executes a calculation process for calculating the predicted upper limit value of the battery 90 (step S2). The predicted upper limit value is a predicted value of the output upper limit value of the battery 90 when the start of the engine 10 by the motor 40 is completed during motor driving. The output upper limit value is the upper limit value that the battery 90 can output per unit time. The specific content of the calculation process will be described later. Step S2 is a process executed by the calculation unit.

[0022] Next, the ECU 100 determines whether the predicted upper limit value has been calculated (step S3). If the answer in step S3 is Yes, the ECU 100 determines whether the predicted upper limit value is greater than or equal to the lower limit value (step S4). The lower limit value will be described later. If the answer in step S3 or S4 is No, the ECU 100 does not permit the transition to motor driving (step S7).

[0023] If the answer in step S4 is Yes, the ECU 100 sets a judgment value (step S5). The judgment value is set as follows. Figure 3A is an example of a map that defines the relationship between vehicle speed and battery output value in this embodiment. This map is pre-stored in the ROM of the ECU 100. Figure 3A shows the required output value and the sufficient output value. The required output value is the output value of the battery 90 per unit time for each vehicle speed at which the motor 40 can maintain driving when the engine 10 has finished starting. The sufficient output value is the required output value plus a predetermined margin value. The margin value is a value that is appropriately determined taking into account fluctuations in the output of the battery 90, etc. The required output value decreases as the vehicle speed decreases. For this reason, the sufficient output value also decreases as the vehicle speed decreases. The vehicle speed at which the sufficient output value becomes the predicted upper limit is set as the judgment value. As mentioned above, the sufficient output value decreases as the vehicle speed decreases. Therefore, the lower the predicted upper limit of the battery 90, the lower the judgment value that is set. As will be explained in more detail later, the margin value decreases as the vehicle speed decreases and as the gear ratio of the automatic transmission 52 increases. Step S5 is an example of a process performed by the setting unit.

[0024] Figure 3A shows the lower limit mentioned above. The lower limit is the minimum sufficient output value for which a transition to motor-driven operation is permitted. Therefore, as mentioned above, if the answer in step S4 is No, a transition to motor-driven operation is not permitted (step S7).

[0025] After step S5 is executed, the ECU 100 determines whether the vehicle speed of hybrid vehicle 1 is below a certain value (step S6). If the answer in step S6 is No, the ECU 100 decides not to allow the transition to motor-driven mode (step S7). If the answer in step S6 is Yes, the ECU 100 decides to allow the transition to motor-driven mode (step S8). Steps S7 and S8 are examples of processes executed by the decision unit.

[0026] As shown in Figure 3A, the lower the predicted upper limit, the lower the judgment value. In other words, the lower the predicted upper limit, the wider the range in which the transition to motor-only driving is not permitted. This allows hybrid driving to continue and suppresses hesitation when transitioning from motor-only driving to hybrid driving.

[0027] Here, we will describe a comparative example where the margin value is constant. Figure 3B is an example of a map that defines the relationship between vehicle speed and battery output value in the comparative example. As shown in Figure 3B, when the margin value is constant, the judgment value is set to a lower value than in the case of this embodiment shown in Figure 3A. For this reason, the permitted range in which the transition to motor driving is allowed in the comparative example is narrower than in this embodiment. Here, when the vehicle speed of hybrid vehicle 1 is low, the acceleration in response to the accelerator input is large. That is, even if hesitation occurs at low vehicle speed, acceleration can be immediately secured by operating the accelerator. For this reason, the driver is less likely to feel the occurrence of hesitation. Accordingly, as shown in Figure 3A, in this embodiment, the margin value decreases as the vehicle speed decreases. As a result, the transition to motor driving is permitted within the range of vehicle speeds in which the driver is less likely to feel the occurrence of hesitation.

[0028] Furthermore, as shown in Figure 3A, the larger the gear ratio of the automatic transmission 52, or in other words, the lower the gear of the automatic transmission 52, the more the margin value decreases in stages. This is because the lower the gear, the greater the acceleration in response to the accelerator input, and the less likely the driver is to perceive hesitation. The transition to motor-driven operation is permitted within the range of gears in which the driver is less likely to perceive hesitation.

[0029] Figure 4 is an example of a map that defines the relationship between vehicle speed and battery output value in a modified example. In the modified example, the automatic transmission 52 is a continuously variable transmission. In this case, the larger the gear ratio of the automatic transmission 52, the more the margin value decreases continuously. In this case as well, the larger the gear ratio, the greater the acceleration in response to the accelerator input, and the less the driver perceives hesitation.

[0030] [Calculation control of predicted upper limit] Next, the calculation control of the predicted upper limit value described above will be explained. Figure 5 is a flowchart illustrating the calculation control of the predicted upper limit value. First, the ECU 100 calculates the current output upper limit value of the battery 90 based on the SOC and temperature of the battery 90 (step S21). Figure 6 is an example diagram of a map that defines the output upper limit value according to the SOC and temperature of the battery 90. Figure 6 shows the cases when the SOC is high and when the SOC is low. As shown in Figure 6, the higher the temperature of the battery 90, the higher the output upper limit value of the battery 90 increases to a predetermined value. When the temperature of the battery 90 is above the predetermined value, the output upper limit value of the battery 90 remains constant. Also, the higher the SOC, the higher the output upper limit value.

[0031] Next, the ECU 100 acquires the current motor speed of the motor 40 and estimates the motor torque, which is the torque required for motor-driven operation at the acquired motor speed (step S22). The motor torque is estimated, for example, based on a map corresponding to the motor speed.

[0032] Next, the ECU 100 calculates the maximum torque that the motor 40 can output based on the upper output limit calculated in step S21 and the motor rotation speed obtained in step S22 (step S23).

[0033] Next, the ECU 100 calculates the cranking torque and cranking period required to crank the engine 10 using the motor 40 (step S24). The cranking torque is calculated based on the temperature of the lubricating oil in the engine 10. The lower the temperature of the lubricating oil in the engine 10, the greater the cranking torque. The cranking period is the period from when the motor 40 starts cranking the engine 10 until combustion starts in the engine 10. The cranking period is calculated based on the cranking torque and the motor speed.

[0034] Next, it is determined whether the upper limit torque calculated in step S23 is greater than the sum of the cranking torque calculated in step S24 and the motor torque estimated in step S22 (step S25). If the answer in step S25 is No, this control is terminated. In this case, the predicted upper limit is not calculated, and it is determined that transitioning to motor-driven operation is not permitted.

[0035] If the answer in step S25 is Yes, the ECU 100 calculates the power consumption of the battery 90 from the start to the completion of starting the engine 10 by the motor 40 (step S26). This power consumption includes the total power consumption of the motor 40, auxiliary equipment, air conditioner, etc., during the cranking period. The output value of the battery 90 per unit time is calculated based on the sum of the cranking torque and motor torque. Next, the output value of the battery 90 per unit time due to auxiliary equipment and air conditioner is calculated. The power consumption is calculated based on the value obtained by multiplying the sum of these output values ​​by the cranking period.

[0036] Next, the predicted upper limit is calculated based on the power consumption calculated in step S26 (step S27). Specifically, the power consumption is converted to SOC. Then, the converted SOC is subtracted from the current SOC of battery 90. Based on the SOC after the subtraction and the temperature of battery 90, the output upper limit is calculated by referring to the map in Figure 6 and is calculated as the predicted upper limit.

[0037] Although 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 changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0038] 1. Hybrid vehicle 10 Engines 30 Clutch 40 motors 90 batteries 100 ECUs (Control Unit, Calculation Unit, Setting Unit, Determination Unit)

Claims

1. The engine and A clutch positioned in the power transmission path from the engine to the wheels, A motor is positioned on the power transmission path from the clutch to the wheel, and is capable of starting the engine by cranking the engine with the clutch engaged. A battery that outputs power to the motor, The system includes a control device that switches between hybrid driving, in which the vehicle is driven by the engine with the clutch engaged, and motor driving, in which the vehicle is driven by the motor with the clutch disengaged. The control device is During the aforementioned hybrid driving, a calculation unit calculates a predicted upper limit value, which is a predicted value of the upper limit of the battery output when the engine is started by the motor during the motor driving; A setting unit that sets a determination value based on the aforementioned predicted upper limit, The system includes a determination unit that determines whether to deny the transition to motor-only driving if the vehicle speed during hybrid driving is higher than the determination value, and determines whether to grant permission to transition to motor-only driving if the vehicle speed during hybrid driving is less than or equal to the determination value. The setting unit sets the vehicle speed at which the output value sufficiently reaches the predicted upper limit as the determination value. The aforementioned sufficient output value is the required output value plus a predetermined margin value. The required output value is the output value per unit time of the battery for each vehicle speed at which the motor can maintain driving when the engine has finished starting. The aforementioned required power output decreases as the vehicle speed decreases. The aforementioned margin value decreases as the vehicle speed decreases in a hybrid vehicle.

2. The transmission is located on the power transmission path from the motor to the wheel, The hybrid vehicle according to claim 1, wherein the margin value decreases as the gear ratio in the transmission increases.

3. The hybrid vehicle according to claim 1 or 2, wherein the calculation unit calculates the predicted upper limit based on the State of Charge (SOC) of the battery and the amount of power consumed by the battery from the start to the completion of starting the engine by the motor.

4. The hybrid vehicle according to claim 3, wherein the calculation unit calculates the power consumption based on the rotational speed of the motor during hybrid driving, the torque of the motor required for motor driving at the rotational speed of the motor, the cranking torque required for cranking the engine by the motor, and the cranking period, which is the period from when cranking of the engine by the motor is started until combustion is started in the engine.

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