JP2022063663A - Regenerative braking control device for electric vehicle - Google Patents

Abstract

To provide a regenerative braking control device for an electric vehicle which can prevent a vehicle behavior from being instable on a low μ road, and prevents discomfort in a change of deceleration feeling on the low μ road and a high μ road.SOLUTION: A regenerative torque control part (102) controls a regenerative torque so as to have a predetermined gradient (ΔTb) at the time of a regenerative start, and reduces the regenerative torque after rising of the regenerative torque compared with the case in which a road surface friction coefficient is large when the road surface friction coefficient acquired by a road surface friction coefficient acquisition part (101) is small.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a regenerative braking control device for an electric vehicle.

Japanese Patent Application Laid-Open No. 2005-253157 (Patent Document 1) discloses a regenerative braking control device that performs braking by driving a generator with the rotational energy of wheels. In this regenerative braking control device, the rising gradient of the deceleration at the start time of the regenerative braking is changed according to the road surface friction coefficient estimated by the road surface friction coefficient estimating means. On a road surface with a small road surface friction coefficient (low μ road), the rising gradient of deceleration at the start of regenerative braking is reduced, and the deceleration at the initial stage of braking is gradually increased. As a result, the braking torque is suddenly increased to prevent slip from occurring at a low deceleration, and slip does not occur until a relatively high deceleration is achieved.

Japanese Unexamined Patent Publication No. 2005-253157

The regenerative braking control device disclosed in Patent Document 1 reduces the rising gradient of deceleration at the start of regenerative braking on a low μ road, so that slip occurrence can be suppressed, but the road surface has a large road friction coefficient (high). The feeling of deceleration felt by the driver is smaller than that during regenerative braking on the μ road), which may give the driver a sense of discomfort.

The present disclosure provides a regenerative braking control device for an electric vehicle, which can prevent the vehicle behavior from becoming unstable on a low μ road and is less likely to cause a sense of discomfort in the change in deceleration feeling between a low μ road and a high μ road. The purpose is.

The regenerative braking control device for an electric vehicle of the present disclosure is a regenerative braking control device for an electric vehicle equipped with a rotary electric machine for traveling, and has a road surface friction coefficient acquisition unit for acquiring a road surface friction coefficient and rotation during deceleration of the electric vehicle. It is equipped with a regenerative torque control unit that controls the regenerative torque of the electric machine. The regenerative torque control unit controls the regenerative torque so that it has a predetermined rising gradient at the start of regeneration, and when the road surface friction coefficient acquired by the road surface friction coefficient acquisition unit is small, it is regenerated as compared with the case where the road surface friction coefficient is large. It is configured to reduce the regenerative torque after the torque rises.

According to this configuration, when the road surface friction coefficient acquired by the road surface friction coefficient acquisition unit is small, the regenerative torque control unit has a smaller regenerative torque after the rise of the regenerative torque than when the road surface friction coefficient is large. .. When the road surface friction coefficient is small (low μ road), the regenerative torque after the rise of the regenerative torque is smaller than when the road surface friction coefficient is large (high μ road), so the braking force on the low μ road is small. Therefore, it is possible to prevent the vehicle behavior from becoming stable and unstable. In addition, since the regenerative torque rises with a predetermined rising gradient, the deceleration at the initial stage of regenerative braking on the high μ road and the low μ road is almost the same, and the change in the deceleration feeling on the high μ road and the low μ road can be suppressed, resulting in a sense of discomfort. Can be hard to feel.

According to the present disclosure, a regenerative braking control device for an electric vehicle is provided, which can prevent the vehicle behavior from becoming unstable on a low μ road and is less likely to cause a sense of discomfort in the change in deceleration feeling between a low μ road and a high μ road. Can be provided.

It is an overall block diagram of the electric vehicle 1 provided with the regenerative braking control device which concerns on this embodiment. It is a functional block diagram of the HV-ECU 100 in this embodiment. It is a figure which shows the map for calculating the regenerative torque Tb of MG60. It is a flowchart which shows the procedure which is processed by the regenerative torque control unit 102 of the HV-ECU 100. It is a figure which shows the deceleration of the electric vehicle 1 by a regenerative torque Tb. It is a map which calculates the regenerative torque Tb of MG60 in the modification 1. It is a flowchart which shows the procedure to be processed by the regenerative torque control unit 102 of the HV-ECU 100 in the modification 2. It is a figure explaining the electric vehicle 200 in the modification 3. FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

FIG. 1 is a diagram showing an overall configuration of an electric vehicle 1 provided with a regenerative braking control device according to the present embodiment. The electric vehicle 1 is a hybrid vehicle provided with an internal combustion engine 10. The electric vehicle 1 includes an internal combustion engine 10, a torque converter 20, and an automatic transmission 30.

The internal combustion engine 10 is, for example, a spark ignition type internal combustion engine or a compression ignition type internal combustion engine, and the output shaft of the internal combustion engine 10 is connected to the input shaft of the torque converter 20. The torque converter 20 is a torque converter with a lockup clutch and includes a pump impeller, a turbine runner, a stator, and a lockup clutch (not shown). Torque amplification is performed between the pump impeller connected to the input shaft of the torque converter 20 and the turbine runner connected to the output shaft of the torque converter 20, and the output of the internal combustion engine 10 is transmitted to the automatic transmission 30. The lockup clutch (not shown) of the torque converter 20 is controlled to one of an engaged state, an released state, and a slip (semi-engaged) state. When the lockup clutch is engaged, the input shaft and the output shaft of the torque converter 20 are directly connected, and the input shaft and the output shaft rotate integrally.

The output shaft of the torque converter 20 is connected to the input shaft of the automatic transmission 30. The automatic transmission 30 is a planetary gear type multi-stage automatic transmission, and achieves each transmission stage by controlling the combination of engagement and disengagement of a plurality of friction engagement elements. The output shaft of the automatic transmission 30 is connected to the differential gear 40 via the propeller shaft. The differential gear 40 is connected to the rear wheel 50, which is a drive wheel, via a drive shaft. The electric vehicle 1 is a rear wheel drive vehicle that transmits the output torque (drive torque) output from the internal combustion engine 10 to the rear wheels 50 via the torque converter 20, the automatic transmission 30, and the differential gear 40.

The electric vehicle 1 includes a motor generator (hereinafter referred to as “MG”) 60. The MG60 is a rotary electric machine, for example, an IPM (Interior Permanent Magnet) synchronous motor in which a permanent magnet is embedded in a rotor. The output shaft (rotor shaft) of the MG 60 is connected to the crank shaft of the internal combustion engine 10 via the belt 61. When the MG 60 operates as an electric motor, the output torque of the MG 60 drives the rear wheels 50, which are the driving wheels, via the crank shaft of the internal combustion engine 10. Specifically, the output torque of the MG 60 is added to the output torque of the internal combustion engine 10 to drive the rear wheels 50, which are the driving wheels. Further, when the MG 60 is driven via the crank shaft of the internal combustion engine 10, the MG 60 operates as a generator.

The PCU (Power Control Unit) 70 converts the DC power received from the power storage device 80 into AC power for driving the MG 60. Further, the PCU 70 converts the AC power generated (regenerated) by the MG 60 into DC power for charging the power storage device 80. The PCU 70 includes, for example, an inverter and a converter that boosts the DC voltage supplied to the inverter to a voltage equal to or higher than that of the power storage device 80.

The power storage device 80 is a rechargeable DC power source, and includes a secondary battery such as a lithium ion battery or a nickel hydrogen battery. For example, a 48V lithium ion battery may be used as the power storage device 80. The power storage device 80 receives the electric power generated by the MG 60 and is charged. Then, the power storage device 80 supplies the stored electric power to the PCU 70, and the MG 60 is driven.

The power storage device 80 is provided with a monitoring unit 81. The monitoring unit 81 includes a voltage sensor, a current sensor, and a temperature sensor (none of which are shown) for detecting the voltage, input / output current, and temperature of the power storage device 80, respectively. The monitoring unit 81 outputs the detected values of each sensor (voltage of the power storage device 80, input / output current, and temperature) to the BAT-ECU 110.

The electric vehicle 1 includes an E / G-ECU (Electronic Control Unit) 90, an HV-ECU 100, a BAT-ECU 110, an accelerator opening sensor 120, an outside air temperature sensor 130, and various sensors 140. Each ECU includes a CPU (Central Processing Unit), a memory, and an input / output buffer (not shown), inputs signals from various sensors and outputs control signals to each device, and controls each device.

The BAT-ECU 110 calculates the SOC (State Of Charge) of the power storage device 80 based on the detection value of each sensor output from the monitoring unit 81, and outputs the SOC (State Of Charge) to the HV-ECU 100. The HV-ECU 100 outputs a command for controlling the internal combustion engine 10 and the torque converter 20 to the E / G-ECU 90, and outputs a command for controlling the MG 60 to the PCU 70. The HV-ECU 100 corresponds to the "regenerative braking control device" in the present disclosure.

The E / G-ECU 90 controls the output of the internal combustion engine 10 and controls the engagement state (slip state) of the lockup clutch of the torque converter 20 based on the command of the HV-ECU 100. By controlling the PCU 70 according to the command of the HV-ECU 100, the MG 60 is controlled to the power running state (driving state) or the regenerative state (power generation state).

The accelerator opening sensor 120 detects the accelerator opening AP, which is the amount of depression of the accelerator pedal. Instead of the accelerator opening sensor 120, a throttle opening sensor that detects the throttle opening of the internal combustion engine 10 may be used. The outside air temperature sensor 130 detects the outside air temperature around the electric vehicle 1. Further, the various sensors 140 include a vehicle speed sensor that detects the vehicle speed V, a brake sensor that detects the amount of depression of the brake pedal, and the like.

FIG. 2 is a functional block diagram of the HV-ECU 100 in the present embodiment. The HV-ECU 100 includes a road surface friction coefficient acquisition unit 101 and a regenerative torque control unit 102. These configurations may be realized by software processing or by hardware (electrical circuit).

The road surface friction coefficient acquisition unit 101 estimates and acquires the road surface friction coefficient (road surface μ) based on the outside air temperature detected by the outside air temperature sensor 130. Specifically, the road surface friction coefficient acquisition unit 101 estimates that the road surface friction coefficient is small (low μ road) when the outside air temperature is low enough to freeze the road surface (for example, when the outside air temperature is 2 ° C. or lower). Further, the road surface friction coefficient acquisition unit 101 estimates that the road surface friction coefficient is large (high μ road) when the outside air temperature is not so low as to freeze the road surface (for example, when the outside air temperature exceeds 2 ° C.).

The regenerative torque control unit 102 determines that the electric vehicle 1 is decelerating when the accelerator opening AP detected by the accelerator opening sensor 120 is zero, that is, when the accelerator pedal is not depressed while the vehicle is running. Judgment is made, and the regenerative torque of MG60 is calculated. FIG. 3 is a map for calculating the regenerative torque Tb of the MG 60, and the regenerative torque control unit 102 calculates the regenerative torque Tb of the MG 60 based on the map of FIG.

In FIG. 3, the vertical axis is the magnitude of the regenerative torque Tb, and the horizontal axis is the time from the start of regeneration (at the start of deceleration). In FIG. 3, the solid line shows the regenerative torque TbA on the high μ road, and the broken line shows the regenerative torque TbB on the low μ road. The rising gradient ΔTb (= dTb / dt) at the start of regeneration is the same for the regenerative torque TbA on the high μ road and the regenerative torque TbB on the low μ road. The regenerative torque TbA on the high μ path increases with the rising gradient ΔTb after the start of regeneration, and when the magnitude of the regenerative torque TbA reaches the maximum value Tb1, it is maintained at the maximum value Tb1 thereafter. The regenerative torque TbB in the low μ path increases with the rising gradient ΔTb after the start of regeneration, gradually decreases when the magnitude of the regenerative torque TbB reaches the maximum value Tb1, and then is maintained at Tb2 when it reaches Tb2. As described above, the regenerative torque TbB on the low μ road is set so that the regenerative torque after the rise of the regenerative torque is smaller than that of the regenerative torque TbA on the high μ road. The regenerative torque Tb calculated by the regenerative torque control unit 102 is output to the PCU 70 as a command value. The PCU 70 drives the MG 60 so that the regenerative torque of the MG 60 matches the command value.

The rising gradient ΔTb at the start of regeneration and the maximum value Tb1 are predetermined by experiments and simulations so that a desired deceleration can be obtained when the electric vehicle 1 is decelerated. A plurality of rising gradient ΔTb and maximum value Tb1 may be set according to the shift range of the electric vehicle 1, the vehicle speed V at the start of deceleration, and the like.

FIG. 4 is a flowchart showing a procedure processed by the regenerative torque control unit 102 of the HV-ECU 100. In the flowchart shown in FIG. 4, when the accelerator opening AP becomes zero and deceleration is started while the electric vehicle 1 is traveling, interrupt processing is performed. For example, when the depression of the accelerator pedal is released while the electric vehicle 1 is traveling, interrupt processing is performed. First, in step 1 (hereinafter, step is abbreviated as "S") 1, it is determined whether or not the vehicle speed V of the electric vehicle 1 is larger than the predetermined value α. The predetermined value α is a value for determining whether or not regenerative braking is performed by the regenerative torque of the MG 60, and is a value previously determined in an experiment or the like depending on the amount of energy obtained by the regenerative braking and the responsiveness of various devices. When the vehicle speed V is equal to or less than the predetermined value α, the regenerative braking is not executed, so that a negative determination is made and the process proceeds to S7. If the vehicle speed V is larger than the predetermined value α, a positive judgment is made and the process proceeds to S2.

In S2, it is determined whether or not regeneration by MG60 is possible. Specifically, it is determined whether or not the SOC of the power storage device 80 exceeds the predetermined value β. When the SOC of the power storage device 80 exceeds the predetermined value β, charging the power storage device 80 may result in overcharging, so that it is determined that regeneration by the MG 60 is difficult. If it is determined in S2 that the SOC of the power storage device 80 exceeds the predetermined value β, the process proceeds to S7. When the temperature TB of the power storage device 80 exceeds the upper limit value or the temperature of the MG 60 exceeds the upper limit value, S2 may be determined affirmatively (determined that regeneration by the MG 60 is difficult). ..

If the SOC of the power storage device 80 is equal to or less than the predetermined value β in S2, it is determined that regeneration by MG60 is possible (negative determination in S2), and the process proceeds to S3. In S3, the regenerative torque Tb of the MG 60 is calculated based on the (estimated) road surface friction coefficient acquired by the road surface friction coefficient acquisition unit 101. Specifically, when the outside air temperature is low enough to freeze the road surface and the road surface is low, the regenerative torque TbB is calculated as the regenerative torque Tb from the map shown in FIG. 3, and the outside air temperature is not so low that the road surface freezes. In the case of a high μ path, the regenerative torque TbA is calculated as the regenerative torque Tb from the map shown in FIG. 3, and the process proceeds to S4.

In S4, the calculated regenerative torque Tb is output to the PCU 70 as a command value, and the regenerative braking is executed by driving the MG 60 so that the regenerative torque of the MG 60 matches the command value.

In S5 following S4, it is determined whether or not the accelerator opening AP has become larger than zero. When the accelerator pedal is depressed and the accelerator opening AP becomes larger than zero, a positive judgment is made in S5 and the process proceeds to S7. If the accelerator pedal is not depressed, the accelerator opening AP is zero, so a negative determination is made and the process proceeds to S6.

In S6, it is determined whether or not the vehicle speed V exceeds the predetermined value γ. The predetermined value γ is a threshold value for ending the regenerative braking, and may be, for example, equal to or smaller than the predetermined value α. If the vehicle speed V exceeds the predetermined value γ, a positive judgment is made, the vehicle returns to S4, and regenerative braking is continued. If the vehicle speed V is equal to or less than the predetermined value γ, a negative determination is made and the process proceeds to S7.

In S7, after the regenerative torque Tb is set to zero, the current routine (interrupt processing) is terminated. By setting the regenerative torque Tb to zero in S7, the command value of the regenerative torque of the PCU 70 becomes zero, so that the regenerative braking ends or the regenerative braking is not executed.

When the motor vehicle 1 decelerates, the front wheel load increases, but the rear wheel load decreases. Therefore, in the electric vehicle 1 driven by the rear wheels, the rear wheels 50 tend to be easily locked by the braking force due to the regenerative torque Tb of the MG 60. In particular, on a low μ road having a small road surface friction coefficient, the rear wheels 50 are more likely to lock, and the vehicle behavior of the electric vehicle 1 is likely to become unstable. Therefore, on a low μ road, it is desirable to reduce the regenerative torque Tb of the MG 60 to suppress the locking of the rear wheels 50 and stabilize the behavior of the electric vehicle 1. However, when the regenerative torque Tb of the MG 60 becomes small, the braking force becomes small, and the feeling of deceleration felt by the driver also decreases.

In the present embodiment, the regenerative torque Tb of MG60 calculated in S3 is obtained from the map of FIG. In the case of a low μ road having a small road surface friction coefficient, the regenerative torque TbB is calculated, and in the case of a high μ road having a large road surface friction coefficient, the regenerative torque TbA is calculated. In the regenerative torque TbB on the low μ road and the regenerative torque TbA on the high μ road, the rising gradient ΔTb at the start of regeneration (at the start of deceleration) is the same, but the regenerative torque TbB on the low μ road gradually decreases after the rising. , The value after rising is set to be smaller than that of the regenerative torque TbA on the high μ road.

FIG. 5 is a diagram showing the deceleration of the electric vehicle 1 due to the regenerative torque. In FIG. 5, the solid line shows the deceleration a of the electric vehicle 1 at the regenerative torque TbA, and the broken line shows the deceleration b of the electric vehicle 1 at the regenerative torque TbB. Since the rising gradient ΔTb of the regenerative torque TbA and the regenerative torque TbB are the same, as shown in FIG. 5, the deceleration a and the deceleration b at the start of regeneration (at the start of deceleration) are the same. After the regenerative torque rises, the regenerative torque TbB gradually decreases and becomes smaller than the regenerative torque TbA, so that the deceleration b becomes smaller than the deceleration a.

The regenerative torque TbB on the low μ path is gradually reduced to a small value after rising. Therefore, the braking force on the low μ road becomes small, and the locking of the rear wheel 50 on the low μ road can be suppressed, so that the vehicle behavior can be prevented from becoming unstable on the low μ road. Further, since the rising gradient ΔTb of the regenerative torque TbA and the regenerative torque TbB is the same, and the deceleration a and the deceleration b at the start of regeneration are the same, the driver of the electric vehicle 1 is high even on a low μ road. You can feel the same deceleration feeling as on the μ road. Further, since the regenerative torque TbB on the low μ road gradually decreases (because it gradually decreases), it is possible to further suppress the change in the deceleration feeling between the low μ road and the high μ road, and it is possible to make it difficult to feel a sense of discomfort.

In the above embodiment, the road surface friction coefficient acquisition unit 101 estimates the road surface friction coefficient (road surface μ) based on the outside air temperature detected by the outside temperature sensor 130, and is either a low μ road or a high μ road. The coefficient of friction on the road surface was estimated relatively easily. However, the method of acquiring the road surface friction coefficient by the road surface friction coefficient acquisition unit 101 is not limited to this. For example, by irradiating an infrared laser with multiple wavelengths toward the road surface and measuring its reflection, the friction coefficient of the road surface and the road surface condition (dry, wet, frozen, etc.) are detected and the road surface friction coefficient is obtained. May be. Further, the slip ratio at the time of acceleration is obtained from the vehicle body speed of the electric vehicle 1 and the wheel speed of the rear wheels 50 (driving wheels), and the road surface friction coefficient is estimated based on the slip ratio and the maximum value of the acceleration. good.

(Modification 1)
In the above embodiment, the regenerative torque Tb by MG60 is obtained from the map of FIG. 3, but the regenerative torque Tb may be calculated from the map shown in FIG. FIG. 6 is a map for calculating the regenerative torque Tb of MG60 in the first modification.

In FIG. 6, the regenerative torque TbB1 in the low μ path increases at the rising gradient ΔTb after the start of regeneration, gradually decreases when the magnitude of the regenerative torque TbB reaches the maximum value Tb3, and then is maintained at Tb2 when it reaches Tb2. .. The maximum value Tb3 is smaller than the maximum value Tb1 at which the rise of the regenerative torque TbA on the high μ path ends. In this modification, the maximum value Tb3 of the regenerative torque TbB1 on the low μ road is made smaller than the maximum value Tb1 of the regenerative torque TbA on the high μ road, and the regenerative torque TbB1 is gradually reduced after the regenerative torque rises. .. In this modification 1, the braking force on a low μ road can be made smaller, and the locking of the rear wheel 50 can be suppressed more reliably. Since the rising gradient ΔTb of the regenerative torque TbA and the regenerative torque TbB1 are the same and the deceleration at the start of regeneration is the same, the driver of the electric vehicle 1 decelerates the same as the high μ road even on the low μ road. You can feel the feeling.

(Modification 2)
FIG. 7 is a flowchart showing a procedure processed by the regenerative torque control unit 102 of the HV-ECU 100 in the second modification. The flowchart shown in FIG. 7 is obtained by adding S10 and S20 to the flowchart of FIG. 4 in the above embodiment, and interrupt processing is performed when the accelerator opening AP becomes zero while the electric vehicle 1 is traveling.

In FIG. 7, the processes of S1 to S7 are the same as those in FIG. 4, and the description thereof will be omitted. In S10, it is determined whether or not the temperature TB of the power storage device 80 exceeds the predetermined value θ based on the detected value of the monitoring unit 81. The predetermined value θ is a threshold value for determining whether or not the power storage device 80 needs to be warmed up. When the temperature TB of the power storage device 80 exceeds the predetermined value θ, it is not necessary to warm up the power storage device 80, so that a positive determination is made and the process proceeds to S3. When the temperature TB of the power storage device 80 is equal to or less than the predetermined value θ, it is determined to be negative because the power storage device 80 needs to be warmed up, and the process proceeds to S20. In S20, the regenerative torque Tb of the MG 60 is set to the regenerative torque TbA, and the process proceeds to S4. The regenerative torque TbA is the regenerative torque TbA in the high μ path shown in FIG.

When the power storage device 80 is charged, it self-heats due to internal resistance. In this modification 2, when the power storage device 80 needs to be warmed up even on a low μ path, regenerative braking is executed by the regenerative torque TbA on the high μ path, and the regenerative amount (regenerative power) is not reduced. Therefore, warming up by self-heating is promoted.

(Modification 3)
In the above embodiment, the hybrid vehicle (electric vehicle 1) in which the output shaft of the MG 60 is connected to the crank shaft of the internal combustion engine 10 via the belt 61 has been described, but even the electric vehicle 200 having the configuration shown in FIG. 8 has been described. good. FIG. 8 is a diagram illustrating the electric vehicle 200 in the modified example 3. In FIG. 8, in the electric vehicle 200, the MG 60A is provided on the input shaft of the torque converter 20. That is, the rotor shaft of the MG60A is connected to the input shaft of the torque converter 20. The MG 60A and the internal combustion engine 10 are connected via the clutch 11. Other configurations are the same as those of the electric vehicle 1.

In the electric vehicle 200, when the clutch 11 is released, traveling (EV traveling) using only the output of the MG 60A without using the power of the internal combustion engine 10 becomes possible. Further, by releasing the clutch 11, it is possible to decelerate only by the regenerative torque of the MG60A without using the engine brake.

In the above embodiment, the hybrid vehicle has been described as the electric vehicle 1, but the electric vehicle may be an electric vehicle not provided with an internal combustion engine.

Although the above embodiment is a rear-wheel drive vehicle, it may be a front-wheel drive vehicle or an all-wheel drive vehicle.

By exemplifying the embodiments in the present disclosure, the following embodiments can be exemplified.

1) A regenerative braking control device (100) for an electric vehicle (1) equipped with a rotary electric machine (60) for traveling, which includes a road surface friction coefficient acquisition unit (101) for acquiring a road surface friction coefficient and an electric vehicle (1). ) Is provided with a regenerative torque control unit (102) that controls the regenerative torque of the rotary electric machine (60) during deceleration, and the regenerative torque control unit (102) regenerates so as to have a predetermined rising gradient (ΔTb) at the start of regeneration. When the road surface friction coefficient acquired by the road surface friction coefficient acquisition unit (101) by controlling the torque is small, the regenerative torque after the rise of the regenerative torque is smaller than when the road surface friction coefficient is large. There is.

2) In 1, the regenerative torque (TbA) when the road surface friction coefficient is large and the regenerative torque (TbB) when the road surface friction coefficient is small have the same maximum value (Tb1) after rising, and the road surface friction coefficient is small. The regenerative torque (TbB) in the case is gradually reduced when it reaches the maximum value (Tb1).

According to this configuration, the regenerative torque (TbA) when the road surface friction coefficient is large (high μ road) and the regenerative torque (TbB) when the road surface friction coefficient is small (low μ road) have a predetermined rising gradient (ΔTb). The maximum value (Tb1) after the rise is the same. Therefore, the deceleration at the initial stage of regenerative braking on the high μ road and the low μ road is almost the same, the change in the deceleration feeling between the high μ road and the low μ road can be suppressed, and the feeling of discomfort can be lessened. Further, since the regenerative torque (TbB) on the low μ road gradually decreases (because it gradually decreases), the change in the deceleration feeling between the low μ road and the high μ road can be further suppressed, and the feeling of discomfort can be lessened.

3) In 1, the maximum value (Tb3) after rising in the regenerative torque (TbB1) when the road surface friction coefficient is small is larger than the maximum value (Tb1) after rising in the regenerative torque (TbA) when the road surface friction coefficient is large. The regenerative torque (TbB1) when the road surface friction coefficient is small is gradually reduced when it reaches the maximum value (Tb3).

According to this configuration, the braking force when the road surface friction is small (low μ road) can be made smaller, the lock of the drive wheels can be suppressed more reliably, and the vehicle behavior becomes unstable. can. Further, since the rising gradient of the regenerative torque is the same on the high μ road and the low μ road, the deceleration at the initial stage of the regenerative braking is almost the same, and the driver can hardly feel a sense of discomfort.

4) In 2 or 3, the rotary electric machine (60) is provided with a power storage device (80) that receives and charges the regenerated (generated) power, and the regenerative torque control unit (102) has the temperature of the power storage device (80). When the value is lower than the predetermined value (θ) and the road surface friction coefficient is high, the regenerative torque (TbA) is set as the regenerative torque of the rotary electric machine (60).

According to this configuration, when warming up of the power storage device (80) is required, regenerative braking is executed by the regenerative torque (TbA) when the road surface friction coefficient is high, and the regenerative amount (regenerative power) is not reduced. , Warming up of the power storage device (80) is promoted.

5) In 1 to 4, the road surface friction coefficient acquisition unit (101) estimates that the road surface friction coefficient is small when the outside air temperature is lower than the predetermined temperature.

According to this configuration, the coefficient of friction on the road surface can be obtained relatively easily.

6) In 1 to 5, the electric vehicle (1) is rear-wheel drive.

When the vehicle is decelerating, the front wheel load generally increases, but the rear wheel load decreases. Therefore, when the electric vehicle (1) is rear-wheel drive, the rear wheels tend to lock easily due to deceleration due to the regenerative torque. However, each of the above configurations should be applied to the rear-wheel drive electric vehicle (1). Therefore, the locking of the rear wheels due to the regenerative torque can be suitably suppressed. In addition, in a part-time four-wheel drive vehicle, this may be applied when traveling by rear-wheel drive.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the scope of claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Electric vehicle, 10 internal combustion engine, 20 torque converter, 30 automatic transmission, 50 rear wheels, 60 motor generator (MG), 70 PCU, 80 power storage device, 100 HV-ECU, 101 road friction coefficient acquisition unit, 102 regenerative torque Acquisition unit, 120 accelerator opening sensor, 130 outside temperature sensor.

Claims (1)

A regenerative braking control device for electric vehicles equipped with a rotary electric machine for traveling.
The road surface friction coefficient acquisition unit that acquires the road surface friction coefficient, and the road surface friction coefficient acquisition unit,
A regenerative torque control unit that controls the regenerative torque of the rotary electric machine when the electric vehicle is decelerated is provided.
The regenerative torque control unit controls the regenerative torque so as to have a predetermined rising gradient at the start of regeneration, and when the road surface friction coefficient acquired by the road surface friction coefficient acquisition unit is small, it is compared with the case where the road surface friction coefficient is large. A regenerative braking control device for an electric vehicle, which is configured to reduce the regenerative torque after the rise of the regenerative torque.

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