Hybrid vehicles

Abstract

The challenge is to provide a hybrid vehicle that minimizes the decline in drivability. [Solution] The vehicle comprises an engine, a motor that generates electricity by receiving the rotational power of the engine, a torque converter having a lock-up clutch, an automatic transmission provided between the torque converter and the drive wheels, a battery that charges the power generated by the motor, and a control device, wherein the control device includes a determination unit that determines whether the engine is in a driving state and stationary, and whether the lock-up clutch is in a disengaged state in the D range of the automatic transmission, a setting unit that, if the determination unit makes a positive determination, sets the target idle speed of the engine to a higher value the greater the required charging power of the battery, and a control unit that controls the engine such that the rate of increase when raising the engine speed toward the target idle speed decreases as the engine speed increases when the engine is idling.

Description

Technical Field

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

Background Art

[0002] There is a hybrid vehicle that sets the target idle speed of the engine to a high value when there is a request for battery charging (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] It is conceivable to set the target idle speed to a higher value as the required charging power of the battery increases. However, increasing the target idle speed increases the creep torque, which may increase the acceleration at the time of vehicle start and reduce driving performance.

[0005] Therefore, an object of the present invention is to provide a hybrid vehicle that suppresses a decrease in driving performance.

Means for Solving the Problems

[0006] The above objective can be achieved by a hybrid vehicle comprising: an engine; a motor provided on a power transmission path between the engine and the drive wheels and generating electricity by receiving rotational power from the engine; a torque converter provided on the power transmission path between the motor and the drive wheels and having a lock-up clutch; an automatic transmission provided between the torque converter and the drive wheels; a battery for charging the power generated by the motor; and a control device, wherein the control device includes a determination unit that determines whether the engine is in a driving state, a stationary state, the automatic transmission is in D range, and the lock-up clutch is in a disengaged state; a setting unit that, if the determination unit makes an affirmative determination, sets a target idle speed, which is the target rotational speed of the engine in an idle state, to a higher value the greater the required charging power of the battery; and a control unit that controls the engine such that the rate of increase when raising the engine speed toward the target idle speed decreases as the engine speed increases when the engine is in an idle state.

[0007] The setting unit may set the target idle speed to a progressively higher value as the battery's required charging power increases, and the control unit may progressively decrease the rate of increase as the engine speed increases.

[0008] The setting unit sets the target idle speed to the first rotation speed if the requested charging power is less than the first threshold; sets the target idle speed to the second rotation speed which is higher than the first rotation speed if the requested charging power is greater than or equal to the first threshold but less than the second threshold which is greater than the first threshold; sets the target idle speed to the third rotation speed which is higher than the second rotation speed if the requested charging power is greater than or equal to the second threshold; the control unit controls the rate of increase to the first rate if the target idle speed is set to the second or third rotation speed and the engine speed is less than the second rotation speed; and controls the rate of increase to the second rate which is lower than the first rate if the target idle speed is set to the third rotation speed and the engine speed is greater than or equal to the second rotation speed but less than the third rotation speed. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hybrid vehicle that suppresses a decline in drivability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a hybrid vehicle. [Figure 2] This is a flowchart illustrating idle speed control. [Figure 3] This is a timing chart illustrating idle speed control. [Figure 4] This graph shows the relationship between idle speed and turbine torque. [Modes for carrying out the invention]

[0011] [Overall configuration of a hybrid vehicle] Figure 1 is a schematic diagram of the hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 and a motor 15 as the power source for driving. The engine 10 is a gasoline engine with multiple cylinders, but it may also be a diesel engine. A transmission unit 11 is provided in the power transmission path from the engine 10 to the drive wheels 13. The transmission unit 11 and the left and right drive wheels 13 are driven together via a differential gear 12.

[0012] The transmission unit 11 is equipped with a K0 clutch 14 and a motor 15. The motor 15 is located on the power transmission path from the engine 10 to the drive wheels 13.

[0013] The K0 clutch 14 is located between the engine 10 and the motor 15 in the power transmission path. The K0 clutch 14 engages when hydraulic pressure is supplied, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 disengages when the hydraulic pressure supply is stopped, interrupting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 also slips from the start of torque transmission until it is fully engaged.

[0014] The motor 15 is connected to the battery 16 via an inverter 17. The battery 16 is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16. Furthermore, the motor 15 also functions as a generator that generates electricity 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 regulated by the inverter 17.

[0015] The transmission unit 11 is equipped with a torque converter 18 and an automatic transmission 19. The torque converter 18 is a fluid coupling with a torque amplification function. The torque converter 18 is installed between the motor 15 and the drive wheels 13 on the power transmission path. The turbine shaft 18a of the torque converter 18 is connected to the input shaft of the automatic transmission 19. The turbine shaft 18a corresponds to the output shaft of the torque converter 18. The torque converter 18 is equipped with a lock-up clutch (hereinafter referred to as LU clutch) 20 that receives hydraulic pressure, engages with it, and directly connects the motor 15 and the automatic transmission 19.

[0016] The LU clutch 20 engages when hydraulic pressure is supplied, connecting the power transmission between the motor 15 and the drive wheels 13. The LU clutch 20 disengages when the hydraulic pressure supply is stopped. The LU clutch 20 also slips from disengagement to engagement.

[0017] The automatic transmission 19 is provided between the torque converter 18 and the drive wheels 13 on the above power transmission path. The automatic transmission 19 is a stepped transmission and includes a plurality of hydraulic friction engagement elements and a planetary gear device. In the automatic transmission 19, by selectively engaging a plurality of friction engagement elements, it can be switched to any one of the P (parking) range, R (reverse) range, N (neutral) range, and D (drive) range.

[0018] 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 automatic transmission 19, and the LU clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with respective hydraulic circuits for the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the LU clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures.

[0019] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 50 as a control device of the hybrid vehicle. The ECU 50 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 50 is an example of a control device and functionally realizes a determination unit, a setting unit, and a control unit, which will be described in detail later.

[0020] The ECU 50 is connected to an ignition switch 61, a crank angle sensor 62, an air flow meter 63, a shift position sensor 64, a vehicle speed sensor 65, a water temperature sensor 66, a SOC (State Of Charge) sensor 67, a battery temperature sensor 68, and an accelerator opening sensor 69. The ignition switch 61 detects the on / off state of the ignition. The crank angle sensor 62 detects the rotational speed of the crankshaft of the engine 10. The air flow meter 63 detects the intake air amount introduced into the engine 10. The shift position sensor 64 detects whether the position of the shift lever is in any of the P range position, R range position, N range position, and D range position. The vehicle speed sensor 65 detects the traveling speed of the hybrid vehicle 1. The water temperature sensor 66 detects the temperature of the cooling water that cools the engine 10. The SOC sensor 67 detects the charge amount of the battery 16. The battery temperature sensor 68 detects the temperature of the battery 16. The accelerator opening sensor 69 detects the accelerator opening, which is the opening of the accelerator pedal operated by the driver.

[0021] The ECU 50 controls the driving of the engine 10 and the motor 15. Specifically, the ECU 50 controls the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16, thereby performing torque control of the motor 15. The ECU 50 performs drive control of the K0 clutch 14, the LU clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22.

[0022] The ECU 50 drives the hybrid vehicle 1 in either the motor driving mode or the hybrid driving mode. In the motor driving mode, the ECU 50 releases the K0 clutch 14 and rotates the drive wheels 13 with the power of the motor 15. In the hybrid driving mode, the ECU 50 engages the K0 clutch 14 and rotates the drive wheels 13 with at least the power of the engine 10. For example, when the required driving force for the hybrid vehicle 1 becomes greater than or equal to the driving force threshold value, the mode is switched from the motor driving mode to the hybrid driving mode. Also, when the charge amount of the battery 16 becomes less than or equal to the power threshold value, the mode is switched from the motor driving mode to the hybrid driving mode.

[0023] In hybrid driving mode, the ECU 50 determines that the negative torque of the motor 15 increases as the required charging power of the battery 16 increases. Therefore, for example, if the required charging power increases while the engine 10 is idling, the negative torque of the motor 15 increases. As a result, the rotational torque of the input shaft of the torque converter 18 changes from positive torque to negative torque, which may increase gear noise due to gear backlash. To suppress such gear noise, the ECU 50 increases the target idle speed of the engine 10. This is because increasing the target idle speed increases the centrifugal force due to the rotation of the input shaft of the torque converter 18, thereby suppressing the aforementioned gear noise. The ECU 50 controls the idle speed of the engine 10 to the target idle speed set based on this consideration as follows.

[0024] [Idle speed control] Figure 2 is a flowchart illustrating idle speed control. This control is executed repeatedly while the ignition is on. The ECU 50 determines whether the hybrid vehicle 1 is stationary, the automatic transmission 19 is in D range, and the LU clutch 20 is disengaged (step S1). If the result in step S1 is No, this control terminates. Step S1 is an example of the process executed by the determination unit.

[0025] If the answer in step S1 is Yes, the ECU 50 determines whether the required charging power of the battery 16 is less than the first threshold P1 (step S2). If the answer in step S2 is Yes, the ECU 50 sets the target idle speed to the first rotational speed R1 (step S3).

[0026] If the answer in step S2 is No, the ECU 50 determines whether the requested charging power is less than the second threshold P2 (step S4). The second threshold P2 is greater than the first threshold P1. If the answer in step S4 is Yes, the ECU 50 sets the target idle speed to the second R2 (step S5). The second R2 is higher than the first R1. If the answer in step S4 is No, the ECU 50 sets the target idle speed to the third R3 (step S6). The third R3 is higher than the second R2. Steps S2 to S6 are examples of processes performed by the setting unit.

[0027] After step S3, S5, or S6 is completed, the ECU 50 determines whether the current engine speed is less than the second engine speed R2 (step S7). If the answer in step S7 is Yes, the ECU 50 sets the rate of increase of the engine speed to the first rate U1 (step S8). The rate of increase of the engine speed is the amount of increase in engine speed per unit time.

[0028] If the answer in step S7 is No, the ECU 50 determines whether the current engine speed is less than the third rotational speed R3 (step S9). If the answer in step S9 is Yes, the ECU 50 sets the rate of increase of the engine speed to the second rate U2 (step S10). The second rate U2 is lower than the first rate U1. If the answer in step S9 is No, this control process ends. In this case, the target idle speed is set to the third rotational speed R3 and the engine speed is maintained at the third rotational speed R3.

[0029] After step S8 or S10 is performed, the ECU 50 controls the engine 10 to increase the engine speed at a set rate (step S11). Specifically, the engine speed is increased at a desired rate by adjusting the intake air volume, fuel injection volume, and ignition timing of the engine 10. Steps S7 to S11 are examples of processes performed by the control unit.

[0030] Figure 3 is a timing chart illustrating idle speed control. Figure 3 shows the changes in required charging power [kW], target idle speed [rpm], and engine speed [rpm]. Figure 3 illustrates the case where the required charging power gradually increases. When the required charging power is less than the first threshold P1 and the target idle speed is set to the first R1, the required charging power increases from the state where the engine speed is the first R1 (time t0). When the required charging power becomes equal to or greater than the first threshold P1, the target idle speed is set to the second R2, and the engine speed begins to increase at the first rate U1 (time t1).

[0031] When the required charging power exceeds the second threshold P2, the target idle speed is set to the third speed R3, but since the engine speed is less than the second speed R2, it continues to increase at the first rate U1 (time t2). When the engine speed exceeds the second speed R2, it begins to increase at the second rate U2 (time t3). When the engine speed exceeds the third speed R3, the increase in engine speed stops and it is maintained at the third speed R3 (time t4).

[0032] As described above, the engine 10 is controlled so that the rate of increase in engine speed decreases as the engine speed increases. The reason for this is explained below. Figure 4 is a graph showing the relationship between idle speed [rpm] and turbine torque [Nm]. Turbine torque is the output torque of the turbine shaft 18a, or in other words, the torque of the output shaft of the torque converter 18. As shown in Figure 4, the slope of the turbine torque increases as the idle speed increases. That is, the rate of increase in turbine torque increases as the idle speed increases. Therefore, the higher the idle speed, the greater the acceleration at startup due to the turbine torque, which may worsen drivability. For this reason, as shown in Figures 2 and 3, the rate of increase in engine speed decreases as the engine speed increases, thereby reducing the amount of increase in turbine torque per unit time. This suppresses acceleration at startup and prevents a decrease in drivability.

[0033] As shown in Figures 2 and 3, the target idle speed is set to progressively higher values ​​as the required charging power increases, and the rate of increase decreases progressively as the engine speed increases, but this is not limited to this. The target idle speed may be set to continuously higher values ​​as the required charging power increases, and the rate of increase may decrease progressively as the engine speed increases. Also, as shown in Figures 2 and 3, the target idle speed is set in three stages and the rate of increase is set in two stages, but there may be more stages than this.

[0034] 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]

[0035] 1. Hybrid vehicle 10 Engines 15 Motor 18 Torque Converter 20 Lock-up clutch 50 ECU (Control Unit, Judgment Unit, Setting Unit, Control Unit)

Claims

1. The engine and A motor is provided in the power transmission path between the engine and the drive wheels, and generates electricity by receiving the rotational power of the engine. A torque converter having a lock-up clutch is provided on the power transmission path between the motor and the drive wheel, An automatic transmission is provided between the torque converter and the drive wheel, A battery for charging the power generated by the motor, A control device is provided, The control device is A determination unit that determines whether the engine is in a running state, stationary state, the automatic transmission is in D range, and the lock-up clutch is in a disengaged state, If the determination unit makes a positive determination, the setting unit sets the target idle speed, which is the target rotational speed of the engine in idle operation state, to a higher value the greater the battery's required charging power. The engine includes a control unit that controls the engine such that the rate at which the engine speed is increased toward the target idle speed decreases as the engine speed increases when the engine is in an idle state. Hybrid vehicle.

2. The setting unit sets the target idle speed to a progressively higher value as the required charging power of the battery increases. The control unit progressively reduces the rate of increase as the engine speed increases, according to claim 1.

3. The setting unit sets the target idle speed to a first rotation speed if the requested charging power is less than a first threshold, sets the target idle speed to a second rotation speed higher than the first rotation speed if the requested charging power is greater than or equal to the first threshold but less than a second threshold greater than the first threshold, and sets the target idle speed to a third rotation speed higher than the second rotation speed if the requested charging power is greater than or equal to the second threshold. The hybrid vehicle according to claim 2, wherein the control unit controls the rate of increase to a first rate when the target idle speed is set to the second or third speed and the engine speed is less than the second speed, and controls the rate of increase to a second rate which is smaller than the first rate when the target idle speed is set to the third speed and the engine speed is greater than or equal to the second speed and less than the third speed.

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