Hybrid electric vehicle

Abstract

A hybrid electric vehicle is characterized by being provided with: an engine; a motor that is provided on a power transmission path between the engine and the drive wheels and that receives rotational power of the engine to generate power; a torque converter provided on a power transmission path between the motor and the drive wheel and having a lock-up clutch; an automatic transmission; a battery; and a control device including: a determination unit that determines whether the engine is in a driving state and in a stopped state, whether the automatic transmission is in a D-range, and whether the lock-up clutch is in a released state; a setting unit that, when the determination unit has a positive determination, sets a target idle rotation speed, which is a target rotation speed in an idle operation state of the engine, to a higher value as the required charging power of the battery increases; and a control unit that, when the engine is in the idle operation state, controls the engine such that the increase rate when the engine rotation speed is increased toward the target idle rotation speed is lower as the engine rotation speed is higher.

Description

Technical Field

[0001] This invention relates to a hybrid electric vehicle. Background Technology

[0002] There is a hybrid electric vehicle that sets the engine’s target idle speed to a high value when there is a need for battery charging (for example, see Japanese Patent Application Publication No. 2024-078322). Summary of the Invention

[0003] It is believed that the higher the battery's charging power demand, the higher the target idle speed should be set. However, increasing the target idle speed will increase creep torque and vehicle acceleration during start-up, potentially leading to a decrease in driving performance.

[0004] Therefore, the object of the present invention is to provide a hybrid electric vehicle that suppresses the decline in driving performance.

[0005] The above objective can be achieved by a hybrid electric vehicle comprising: an engine; a motor disposed in the power transmission path between the engine and the drive wheels, and receiving rotational power from the engine to generate electricity; a torque converter disposed in the power transmission path between the motor and the drive wheels, and having a lock-up clutch; an automatic transmission disposed between the torque converter and the drive wheels; a battery for charging the electricity generated by the motor; and a control device comprising: a determination unit for determining whether the engine is in a driving state and a parked state, whether the automatic transmission is in drive (D) gear, and whether the lock-up clutch is in a released state; a setting unit for setting a higher target speed (target idle speed) of the engine in the idling state when the determination unit determines that the higher the charging power demand of the battery, the higher the target idle speed; and a control unit for controlling the engine in the idling state such that the rate of increase of the engine speed toward the target idle speed is lower when the engine speed is higher.

[0006] The setting unit can set the target idle speed to a higher value in stages when the charging power demand of the battery is higher, and the control unit can reduce the rate of increase in stages when the engine speed is higher.

[0007] The setting unit is configured as follows: when the charging power demand is less than a first threshold, the target idle speed is set to a first speed; when the charging power demand is greater than or equal to the first threshold but less than a second threshold greater than the first threshold, the target idle speed is set to a second speed higher than the first speed; and when the charging power demand is greater than or equal to the second threshold, the target idle speed is set to a third speed higher than the second speed. The control unit performs the following control: when the target idle speed is set to the second or third speed and the engine speed is less than the second speed, the rate of increase is controlled to the first rate; when the target idle speed is set to the third speed and the engine speed is greater than the second speed and less than the third speed, the rate of increase is controlled to the second rate, which is less than the first rate.

[0008] According to the present invention, a hybrid electric vehicle that suppresses the decline in driving performance can be provided. Attached Figure Description

[0009] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein: Figure 1 This is a schematic diagram of the structure of a hybrid electric vehicle.

[0010] Figure 2 This is a flowchart illustrating idle speed control.

[0011] Figure 3 This is a timing diagram illustrating idle speed control.

[0012] Figure 4 It is a graph showing the relationship between idle speed and turbine torque. Detailed Implementation

[0013] A general outline of a hybrid electric vehicle. Figure 1This is a schematic structural diagram of a hybrid electric vehicle 1. In the hybrid electric vehicle 1, an engine 10 and a motor 15 are provided as the power source for driving. The engine 10 is a gasoline engine with multiple cylinders, but it can also be a diesel engine. A transmission unit 11 is provided along the power transmission path from the engine 10 to the drive wheels 13. The transmission unit 11 is driven and connected to the left and right drive wheels 13 via a differential 12.

[0014] The transmission unit 11 includes a K0 clutch 14 and a motor 15. The motor 15 is positioned on the power transmission path from the engine 10 to the drive wheel 13.

[0015] The K0 clutch 14 is disposed between the engine 10 and the motor 15 in the power transmission path. The K0 clutch 14 is engaged when hydraulic pressure is supplied, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is disengaged when the hydraulic pressure supply stops, disconnecting the power transmission between the engine 10 and the motor 15. Furthermore, the K0 clutch 14 is in a slippery state from the start of torque transmission until it is fully engaged.

[0016] Motor 15 is connected to battery 16 via inverter 17. Battery 16 is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. Motor 15 functions as a motor that generates driving force for the vehicle based on power supplied from battery 16. Furthermore, motor 15 also functions as a generator that produces electricity by charging battery 16 based on power transmitted from engine 10 or drive wheels 13. The power supplied between motor 15 and battery 16 is regulated by inverter 17.

[0017] A torque converter 18 and an automatic transmission 19 are provided in the transmission unit 11. The torque converter 18 is a fluid coupling with torque amplification function. The torque converter 18 is located between the motor 15 and the drive wheel 13 in the aforementioned 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 is equivalent to the output shaft of the torque converter 18. A lock-up clutch (hereinafter referred to as the LU clutch) 20 is provided in the torque converter 18, which is engaged by receiving a hydraulic supply to directly connect the motor 15 and the automatic transmission 19.

[0018] The LU clutch 20 is engaged when hydraulic pressure is supplied, connecting the motor 15 and the drive wheel 13 for power transmission. The LU clutch 20 is disengaged when the hydraulic pressure supply stops. Furthermore, the LU clutch 20 is in a slipping state from disengagement to engagement.

[0019] An automatic transmission 19 is disposed between the hydraulic torque converter 18 and the drive wheel 13 in the aforementioned power transmission path. The automatic transmission 19 is a stepped transmission, including multiple hydraulic friction engagement elements and a planetary gear assembly. In the automatic transmission 19, by selectively engaging the multiple friction engagement elements, it can switch to any one of P (Park), R (Reverse), N (Neutral), and D (Drive) gears.

[0020] The transmission unit 11 also includes an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied via the hydraulic control mechanism 22 to the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the LU clutch 20. The hydraulic control mechanism 22 includes the hydraulic circuits for each of the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the LU clutch 20, as well as various hydraulic control valves for controlling their working hydraulic pressure.

[0021] In the hybrid electric vehicle 1, an electronic control unit (ECU) 50 is provided as the control device for the hybrid electric vehicle. The ECU 50 is an electronic control unit equipped with a computational processing circuit that performs various calculations related to vehicle driving control and a memory that stores control programs or data. The ECU 50 is an example of a control device, and more specifically, it functionally implements the decision-making unit, setting unit, and control unit described later.

[0022] An ignition switch 61, a crankshaft angle sensor 62, an air flow meter 63, a shift position sensor 64, and a vehicle speed sensor 65 are connected to the ECU 50. Additionally, a coolant temperature sensor 66, a state of charge (SOC) sensor 67, a battery temperature sensor 68, and a throttle opening sensor 69 are connected to the ECU 50. The ignition switch 61 detects whether the ignition is on or off. The crankshaft angle sensor 62 detects the crankshaft speed of the engine 10. The air flow meter 63 detects the amount of air intake into the engine 10. The shift position sensor 64 detects whether the shift lever is in P, R, N, or D position. The vehicle speed sensor 65 detects the speed of the hybrid electric vehicle 1. The coolant temperature sensor 66 detects the temperature of the coolant cooling the engine 10. The SOC sensor 67 detects the charge level of the battery 16. The battery temperature sensor 68 detects the temperature of the battery 16. Throttle opening sensor 69 detects the throttle opening as the opening of the accelerator pedal operated by the driver.

[0023] ECU 50 controls the drive of engine 10 and motor 15. Specifically, ECU 50 adjusts the power transmission between motor 15 and battery 16 by controlling inverter 17, thereby controlling the torque of motor 15. ECU 50 controls the drive of K0 clutch 14, LU clutch 20, and automatic transmission 19 through hydraulic control mechanism 22.

[0024] ECU 50 operates the hybrid electric vehicle 1 in either motor-driven mode or hybrid driving mode. In motor-driven mode, ECU 50 releases clutch K0 14 and uses the power of motor 15 to rotate drive wheels 13. In hybrid driving mode, ECU 50 engages clutch K0 14, causing drive wheels 13 to rotate using at least the power of engine 10. For example, if the requested driving force for the hybrid electric vehicle 1 exceeds a driving force threshold, the system switches from motor-driven mode to hybrid driving mode. Furthermore, if the charge level of battery 16 falls below a power threshold, the system switches from motor-driven mode to hybrid driving mode.

[0025] In hybrid driving mode, the ECU 50 increases the negative torque of the motor 15 as the charging power demand of the battery 16 increases. Therefore, for example, if the charging power demand of the engine 10 increases while idling, the negative torque of the motor 15 increases. Consequently, the rotational torque of the input shaft of the torque converter 18 transitions from positive to negative, potentially increasing gear backlash and causing knocking noise. To suppress this knocking 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 caused by the rotation of the input shaft of the torque converter 18, which can suppress the aforementioned knocking noise. The ECU 50 controls the engine 10 to achieve the target idle speed set based on this principle.

[0026] Idle speed control Figure 2 This is a flowchart illustrating idle speed control. This control is repeatedly executed during ignition. ECU 50 determines whether the hybrid electric vehicle 1 is in a parked state, whether the automatic transmission 19 is in D gear, and whether the LU clutch 20 is in the disengaged state (S1). If S1 is negative, this control ends. S1 is an example of the processing performed by the determination unit.

[0027] If the condition in S1 is true, ECU50 determines whether the charging power demand of battery 16 is less than the first threshold P1 (S2). If the condition in S2 is true, ECU50 sets the target idle speed to the first speed R1 (S3).

[0028] If S2 is incorrect, ECU 50 determines whether the charging power demand is less than the second threshold P2 (S4). The second threshold P2 is greater than the first threshold P1. If S4 is correct, ECU 50 sets the target idle speed to the second speed R2 (S5). The second speed R2 is higher than the first speed R1. If S4 is incorrect, ECU 50 sets the target idle speed to the third speed R3 (S6). The third speed R3 is higher than the second speed R2. S2 to S6 are examples of the processing performed by the setting unit.

[0029] After executing S3, S5, or S6, ECU50 determines whether the current engine speed is less than the second speed R2 (S7). If yes in S7, ECU50 sets the engine speed increase rate to the first rate U1 (S8). The engine speed increase rate refers to the increase in engine speed per unit time.

[0030] If the condition in S7 is negative, ECU50 determines whether the current engine speed is less than the third speed R3 (S9). If the condition in S9 is positive, ECU50 sets the rate of increase of engine speed to the second rate U2 (S10). The second rate U2 is lower than the first rate U1. If the condition in S9 is negative, this control ends. In this case, the target idle speed is set to the third speed R3, and the engine speed is maintained at the third speed R3.

[0031] After executing S8 or S10, the ECU 50 controls the engine 10 to increase the engine speed at a set rate of increase (S11). Specifically, the engine speed is increased at the desired rate of increase by adjusting the intake air quantity or fuel injection quantity and ignition timing of the engine 10. S7 to S11 are examples of the processes performed by the control unit.

[0032] Figure 3 This is a timing diagram illustrating idle speed control. Figure 3 This indicates the shift in charging power demand [kW], target idle speed [rpm], and engine speed [rpm]. Figure 3 The example illustrates a scenario where the charging power demand gradually increases. When the charging power demand is less than the first threshold P1, the target idle speed is set to the first speed R1, and the engine speed begins to increase from the state of the first speed R1 (time t0). If the charging power demand becomes greater than or equal to the first threshold P1, the target idle speed is set to the second speed R2, and the engine speed begins to increase at the first rate U1 (time t1).

[0033] If the charging power demand exceeds the second threshold P2, the target idle speed is set to the third speed R3. However, since the engine speed is lower than the second speed R2, it continues to increase at the first rate U1 (time t2). If the engine speed exceeds the second speed R2, it begins to increase at the second rate U2 (time t3). If the engine speed exceeds the third speed R3, the increase in engine speed stops and remains at the third speed R3 (time t4).

[0034] As described above, the engine 10 is controlled so that the higher the engine speed, the lower the rate of increase in engine speed. The reason for this will be explained below. Figure 4 This 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, in other words, the torque of the output shaft of the torque converter 18. For example... Figure 4 As shown, the higher the idle speed, the greater the slope of the turbo torque. That is, the higher the idle speed, the greater the rate of increase in turbo torque. Therefore, a higher idle speed results in greater acceleration during start-up due to turbo torque, potentially leading to a deterioration in driving performance. Therefore, as... Figure 2 and Figure 3 As shown, by increasing engine speed, the rate of increase in engine speed decreases, thus reducing the increase in turbo torque per unit time. Therefore, suppressing acceleration during start-up can prevent a decline in driving performance.

[0035] like Figure 2 and Figure 3 As shown, the higher the charging power demand, the higher the target idle speed is set to in stages, resulting in higher engine speeds and a progressively lower rate of increase, but this is not a limitation. It is possible to continuously set the target idle speed to higher values ​​as the charging power demand increases, resulting in higher engine speeds and a progressively lower rate of increase. Furthermore, as... Figure 2 and Figure 3 As shown, the target idle speed is set to 3 stages and the rate of increase is set to 2 stages, but the number of stages can also be more than that.

[0036] The embodiments of the present invention have been described in detail above, but the present invention is not limited to this specific embodiment. Various modifications and alterations can be made within the scope of the spirit of the present invention as set forth in the claims.

Claims

1. A hybrid electric vehicle, characterized in that, have: engine; A motor is located on the power transmission path between the engine and the drive wheel, and generates electricity by receiving the rotational power of the engine. A hydraulic torque converter is disposed on the power transmission path between the motor and the drive wheel, and has a lock-up clutch; An automatic transmission disposed between the torque converter and the drive wheels; A battery that charges the motor with the electricity it generates; and Control device, The control device includes: The determination unit determines whether the engine is in a driving state and a parked state, whether the automatic transmission is in D gear, and whether the lock-up clutch is in a released state. The setting unit, when the determination unit makes a positive determination, sets the target speed (target idle speed) of the engine to a higher value if the battery charging power demand is higher; and The control unit controls the engine in a manner that, when the engine is idling, the rate of increase of the engine speed toward the target idle speed is lower as the engine speed increases.

2. The hybrid electric vehicle according to claim 1, characterized in that, The setting unit periodically sets the target idle speed to a higher value as the battery's charging power demand increases. The control unit causes the rate of increase to decrease in stages as the engine speed increases.

3. The hybrid electric vehicle according to claim 2, characterized in that, The setting unit is configured as follows: If the charging power demand is less than the first threshold, the target idle speed is set to the first speed. When the charging power demand is greater than or equal to the first threshold and less than a second threshold that is greater than the first threshold, the target idle speed is set to a second speed that is higher than the first speed; and If the charging power demand is above the second threshold, the target idle speed is set to a third speed that is higher than the second speed. The control unit performs the following control: When the target idle speed is set to the second or third speed and the engine speed is less than the second speed, the rate of increase is controlled to the first rate; and When the target idle speed is set to the third speed and the engine speed is above the second speed but less than the third speed, the rate of increase is controlled to be a second rate that is smaller than the first rate.

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