JP2023017345A - Braking force control system - Google Patents

Abstract

To provide a braking force control system of an electric vehicle, which is configured to suppress the vehicle from being accelerated unintentionally, when decreasing regenerative braking force, during travelling on a downslope road.SOLUTION: A braking force control system controls braking force of an electric vehicle which is travelling on a downslope road, which comprises a battery, a motor, a switching switch that can switch supply destinations of regenerative currents of the motor, an ESC actuator, a water-cooling resistor 52, and an ECU. The ECU is configured to stop the regenerative currents before the battery is fully charged, when a supply destination of the regenerative currents is switched from the battery to the water-cooling resistor 52, during regenerative braking by the motor during travelling of the vehicle on the downslope road, make the ESC actuator generate hydraulic braking force so as to make up for loss of the regenerative braking force, and switch the switching switch, during the generation of the hydraulic braking force.SELECTED DRAWING: Figure 3

Description

The present invention relates to a braking force control system for controlling the braking force of a vehicle, and more particularly to a braking force control system for controlling the braking force of an electric vehicle while traveling on a downhill road.

Conventionally, electric vehicles (BEV vehicles) that drive motors with electricity stored in batteries, fuel cell vehicles (FCEV vehicles) that drive motors with electricity generated using hydrogen, etc. An electric vehicle that runs by driving is known.

In such an electric vehicle, for example, while driving on a downhill road, the motor generates power by reverse driving from the driving wheels, so that the kinetic energy during driving is used while the regenerative braking force is used as the brake of the electric vehicle. It is common to perform control (regenerative control) to convert the current into regenerative current and charge the battery.

However, in an electric vehicle, when the battery is fully charged, the regenerative current cannot be received by the battery, so regenerative control cannot be performed. There is a problem that it becomes difficult to perform the deceleration assistance that is used. In particular, in a fuel cell vehicle that uses hydrogen to generate electricity, the battery is likely to be fully charged quickly, so such a problem becomes significant.

Therefore, in an electric vehicle, even when the battery is fully charged, the regenerative current exceeding the range that the battery can accept is consumed by a resistor in order to assist deceleration using the regenerative braking force while traveling on a downhill road. has traditionally been done.

Further, for example, Patent Document 1 discloses an electric retarder that generates a braking force by a current supplied from a battery, a battery state-of-charge determination means that determines whether or not the charge capacity of the battery is equal to or greater than a predetermined upper limit, and a vehicle that travels downhill. and braking force determination means for determining whether or not regenerative braking force is required, and when it is determined that the charge capacity of the battery is equal to or higher than the upper limit value and that regenerative braking force is required, the electric retarder A braking control device for a vehicle is disclosed in which the is driven by the current of the battery.

JP 2018-023212 A

However, the above-described conventional method of causing a resistor to consume a regenerative current exceeding the acceptable range of the battery has the following problems.

In other words, in the method of consuming the regenerative current with a resistor, the switch is used to switch the regenerative current supply destination from the battery to the resistor during regenerative braking by the motor. Since the current is flowing, a spark is generated at the time of switching, which may deteriorate the durability of the changeover switch (the contacts of the changeover switch may wear out) or cause radio interference.

Therefore, it is conceivable to set the switching timing after the regenerative current is gradually stopped by the inverter. There is In addition, such a problem may occur similarly when switching the supply destination of the regenerative current from the resistor to the battery.

Further, as in Patent Document 1, when it is determined that deceleration assistance by regenerative braking cannot be performed due to the state in which the regenerative current is being supplied to the battery, the electric retarder is operated using the current from the battery. However, there is a problem in that it is difficult to keep the braking force constant during the period from stopping regenerative braking to switching to the electromagnetic retarder.

The present invention has been made in view of this point, and its object is to reduce (including stop) the regenerative braking force while traveling on a downhill in a braking force control system for an electric vehicle. Another object of the present invention is to provide a technique for suppressing unintended acceleration.

In order to achieve the above object, in the braking force control system according to the present invention, hydraulic braking force is generated so as to compensate for the decrease in regenerative braking force, and while the hydraulic braking force is being generated, the regenerative current is reduced. We are switching supply destinations.

Specifically, the present invention is directed to a braking force control system that controls the braking force of an electric vehicle running downhill.

The braking force control system includes a rechargeable battery mounted on the electric vehicle, a motor for applying regenerative braking force to the electric vehicle by power generation, and a supply of regenerative current generated by the motor. By controlling a changeover switch capable of switching between destinations, a hydraulic pressure generating device that applies hydraulic braking force to the electric vehicle, a power consumption device mounted on the electric vehicle that consumes electric power, and the changeover switch, a control device that switches a supply destination of the regenerative current generated by the motor from one of the battery and the power consumption device to the other, wherein the control device operates during regenerative braking by the motor while traveling on a downhill road. When switching the supply destination of the regenerative current generated by the motor, the hydraulic braking force is generated by the hydraulic pressure generating device so as to reduce the regenerative current and compensate for the decrease in the regenerative braking force, It is characterized in that the switch is switched while the hydraulic braking force is being generated.

In the present invention, "reducing the regenerative current" also includes stopping the regenerative current.

In this configuration, when switching the supply destination of the regenerative current generated by the motor during regenerative braking by the motor while traveling on a downhill, even if a large current is flowing in the circuit, the regenerative current is reduced (or stop), the current value flowing through the circuit can be temporarily lowered. In this way, the supply destination of the regenerative current is switched by the changeover switch while the current value flowing through the circuit is reduced. It is possible to suppress the deterioration of durability and the occurrence of radio wave interference.

However, when the regenerative current is reduced (or stopped), the regenerative braking force is also reduced. Since the supply destination of the regenerative current is switched by the changeover switch while the braking force is being generated, it is possible to suppress the occurrence of unintended acceleration (so-called G loss).

Then, after switching the selector switch, for example, by returning the regenerative braking force to the state before switching, the regenerative braking force before switching (regenerative braking force), during switching (hydraulic braking force), after switching (regenerative braking force ), it is possible to keep the braking force constant.

Therefore, according to the present invention, when switching the supply destination of the regenerative current generated by the motor while traveling downhill, the regenerative braking force is reduced in order to suppress deterioration in the durability of the changeover switch and radio wave interference due to the generation of sparks. Even when it is reduced (or stopped), it is possible to suppress unintended acceleration.

Further, in the braking force control system, the control device predicts that the battery will be fully charged by supplying the regenerative current generated by the motor during regenerative braking by the motor while traveling on a downhill road. In this case, before the battery is fully charged, the regenerative current is reduced, the hydraulic braking force is generated by the hydraulic pressure generating device, and the supply destination of the regenerative current is selected while the hydraulic braking force is being generated. It may be configured to switch to the power consuming device.

According to this configuration, when it is predicted that the battery will be fully charged due to the supply of regenerative current during regenerative braking by the motor while traveling on a downhill, the regenerative current supply destination is switched to the power consuming device. Therefore, even when the battery is fully charged, it is possible to assist deceleration using the regenerative braking force.

Moreover, before the battery is fully charged, the regenerative current is reduced and the hydraulic braking force is generated by the hydraulic pressure generator. Unintended acceleration can be suppressed. Therefore, before switching (regenerative braking force), during switching (hydraulic braking force), and after switching (regenerative braking force), the regenerative power exceeding the range that the battery can accept is supplied to the power consumption device while maintaining the braking force constant. can be consumed.

Further, the present invention provides a braking force control system for controlling the braking force of an electric vehicle running downhill, comprising: a rechargeable battery mounted on the electric vehicle; A motor for applying braking force, a hydraulic generator for applying hydraulic braking force to the electric vehicle, an electromagnetic retarder for applying braking force to the electric vehicle by being supplied with electric current, and charging/discharging of the battery. a controllable control device, wherein the control device predicts that the battery will be fully charged by supplying the regenerative current generated by the motor during regenerative braking by the motor while the vehicle is running on a downhill road. In this case, before the battery is fully charged, the regenerative current is stopped, and the hydraulic braking force is generated by the hydraulic pressure generator so as to compensate for the share of the regenerative braking force, and the hydraulic braking force is configured to supply current from the battery to the electromagnetic retarder during the occurrence of .

According to this configuration, when it is predicted that the battery will be fully charged by the supply of the regenerative current during regenerative braking by the motor while traveling on a downhill, the regenerative current is supplied before the battery is fully charged. In addition, hydraulic braking force is generated so as to compensate for the share of the regenerative braking force, and current is supplied from the battery to the electromagnetic retarder while the hydraulic braking force is being generated. ), during switching (hydraulic braking force), and after switching (braking force by the electromagnetic retarder), the braking force can be kept constant. Therefore, even when the regenerative braking force by the motor is switched to the braking force by the electromagnetic retarder while traveling on a downhill road, it is possible to suppress unintended acceleration.

As described above, according to the braking force control system of the present invention, it is possible to suppress unintended acceleration even when the regenerative braking force is reduced (or stopped) while traveling on a downhill road. can.

1 is a diagram schematically showing an electric vehicle equipped with a braking force control system according to Embodiment 1 of the present invention; FIG. It is a block diagram which shows typically the structural example of the principal part of a braking force control system, the same figure (a) showed the state before full charge, and the same figure (b) has shown the state after full charge. 4 is a time chart schematically showing an auxiliary braking force during running on a downhill road; 4 is a flow chart showing an example of control by a braking force control system; 9 is a time chart schematically showing an auxiliary braking force during running downhill according to Modification 1. FIG. 9 is a time chart schematically showing an auxiliary braking force during running downhill according to Modification 2. FIG. FIG. 5 is a diagram schematically showing an electric vehicle equipped with a braking force control system according to Embodiment 2 of the present invention; It is a block diagram which shows typically the structural example of the principal part of a braking force control system, the same figure (a) showed the state before full charge, and the same figure (b) has shown the state after full charge. 4 is a time chart schematically showing an auxiliary braking force during running on a downhill road;

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing.

(Embodiment 1)
FIG. 1 is a diagram schematically showing an electric vehicle 1 equipped with a braking force control system 10 according to this embodiment. This electric vehicle 1 runs by driving a motor 11 with electricity stored in a battery 13 .

-overall structure-
The electric vehicle 1, as shown in FIG. , a rechargeable battery 13 that exchanges electric power with a motor 11 via an inverter 12; a brake system 20 that applies mechanical braking force to drive wheels 2a and 2b and driven wheels 3a and 3b; and an ECU 30 that controls the whole.

The motor 11 is a known synchronous generator-motor having a rotor (not shown) connected to the drive shaft 5 and embedded with permanent magnets, and a stator (not shown) wound with a three-phase coil. It is configured. A battery 13 capable of charging and discharging a direct current is connected to the motor 11 via an inverter 12 capable of bi-directionally converting between a direct current and an alternating current. The inverter 12 is composed of six switching elements (not shown) and is configured to convert the direct current supplied from the battery 13 into a pseudo three-phase alternating current and supply the motor 11 with the pseudo three-phase alternating current.

When the DC current stored in the battery 13 is converted into AC current by the inverter 12 and supplied to the motor 11, the motor 11 operates as a driving source of the electric vehicle 1 (power running control). The driving force generated by the motor 11 is transmitted to the drive wheels 2a and 2b via the drive shaft 5 and the differential gear 4 to cause the electric vehicle 1 to run.

On the other hand, when the electric vehicle 1 decelerates or runs downhill (during regenerative running), the motor 11 operates as a generator by reverse driving from the driving wheels 2a and 2b (regenerative control). The negative driving force generated by the motor 11 is transmitted to the drive wheels 2a and 2b as a braking force, and the AC current generated by the motor 11 is converted into a DC current by the inverter 12 and charged to the battery 13. be. Thus, the motor 11 is configured to apply regenerative braking force to the electric vehicle 1 by generating power.

The brake system 20 includes a master cylinder 24 that is pressurized by stepping on a brake pedal 21, and wheel brakes 22a, 22b, 23a, 23b that apply braking force to the driving wheels 2a, 2b and the driven wheels 3a, 3b by hydraulic pressure. , an ESC actuator 25 for adjusting the hydraulic pressure to these wheel brakes 22 a, 22 b, 23 a, 23 b, and a brake ECU 26 for controlling the ESC actuator 25 .

The wheel brakes 22a, 22b, 23a, 23b are so-called disc brakes, and include disc rotors that rotate together with the drive wheels 2a, 2b and the driven wheels 3a, 3b, brake pads that are friction members, and the brake pads that are pressed against the disc rotors. a brake caliper having a hydraulic wheel cylinder;

The ESC actuator 25 is provided on a hydraulic path of the brake oil that connects the master cylinder 24 and the wheel brakes 22a, 22b, 23a, 23b. It is configured to adjust the braking force applied to the driving wheels 2a, 2b and the driven wheels 3a, 3b by increasing or decreasing the hydraulic pressures in 22a, 22b, 23a, 23b.

In the brake system 20, basically, when the driver operates the brake pedal 21, master cylinder pressure is applied to the brake oil by the master cylinder 24 according to the pedaling force acting on the brake pedal 21, and the master cylinder pressure is applied to the brake oil. Pressure corresponding to the pressure (pressure adjusted by the ESC actuator 25) acts as wheel cylinder pressure in each of the wheel brakes 22a, 22b, 23a, 23b.

During normal driving, the ESC actuator 25 adjusts the wheel cylinder pressure acting on the wheel brakes 22a, 22b, 23a, and 23b according to the amount of depression of the brake pedal 21 by the driver in accordance with the control command from the brake ECU 26. configured to regulate pressure. Furthermore, the ESC actuator 25 individually adjusts the braking force acting on the drive wheels 2a, 2b and the driven wheels 3a, 3b according to the running state of the electric vehicle 1, regardless of the operation of the brake pedal 21 by the driver. By doing so, it is possible to apply hydraulic braking force to the electric vehicle 1 .

The ECU (Electric Control Unit) 30 is configured as a microprocessor with a CPU (Central Processing Unit) 31 at its center. A RAM (random access memory) 33 for storing data, an input/output port and a communication port (not shown) are provided.

The ECU 30 receives the rotational position from a rotational position detection sensor 41 that detects the rotational position of the rotor of the motor 11, phase current from a current sensor (not shown) attached to the connection line between the motor 11 and the inverter 12, , the voltage across the terminals from a voltage sensor (not shown) installed between the terminals of the battery 13, and the charge/discharge from a current sensor (not shown) attached to the power line connected to the output terminal of the battery 13. Current, battery temperature from a temperature sensor (not shown) attached to the battery 13, shift position from a shift position sensor 43 that detects the operating position of the shift lever 42, and the amount of depression of the accelerator pedal 44 are detected. Accelerator pedal position sensor 45, brake pedal position from brake pedal position sensor 46 that detects the amount of depression of the brake pedal 21, vehicle speed from vehicle speed sensor 47, and slope sensor 48 that detects road slope. A signal representing the gradient from is input through the input port.

On the other hand, the ECU 30 outputs a switching control signal and the like to the inverter 12 that drives the motor 11 through the output port. The ECU 30 calculates the number of rotations of the motor 11 based on the rotational position of the rotor of the motor 11 detected by the rotational position detection sensor 41, and calculates the number of rotations of the motor 11 based on the integrated value of the charging/discharging current of the battery 13 detected by the current sensor. The state of charge (SOC), which is a ratio of the storage capacity that can be discharged from the battery 13, is calculated, or the battery 13 is charged and discharged based on the battery temperature detected by the temperature sensor and the calculated SOC. Calculate a good maximum allowable power. The ECU 30 is also connected to the brake ECU 26 via a communication port to exchange various control signals and data.

The positions of the shift lever 42 detected by the shift position sensor 43 include the parking position (P position), the neutral position (N position), the drive position (D position) for traveling in the forward direction, and the forward position. There is a brake position (B position) where the vehicle travels in the direction of the vehicle, but the braking force when the accelerator is off is greater than that in the drive position, and a reverse position (R position) for traveling in the reverse direction.

In the electric vehicle 1 configured as described above, the required torque to be output to the drive wheels 2a and 2b is calculated based on the accelerator opening corresponding to the amount of depression of the accelerator pedal 44 by the driver and the vehicle speed. A torque command is set as the torque to be output from the motor 11, and the motor 11 is driven and controlled based on the torque command.

Further, when the electric vehicle 1 is decelerated by releasing the accelerator while driving, the braking force corresponding to the shift position and the brake depression force is the regenerative braking force by the regenerative control of the motor 11 and the braking force by the brake system 20. Realized. Then, when the vehicle speed becomes low, in order to stop the electric vehicle 1 smoothly without causing a shock or the like, brake cooperation control is performed to gradually replace the regenerative braking force of the motor 11 with the braking force of the brake system 20. . By performing such coordinated brake control, most of the kinetic energy can be regenerated as electric power by the motor 11 and stored in the battery 13, and the electric vehicle 1 can be stopped smoothly while suppressing the occurrence of shocks. becomes.

- Braking force control system -
In the electric vehicle 1 of the present embodiment, the regenerative braking force is used as the brake of the electric vehicle 1 by generating power in the motor 11 by reverse driving from the driving wheels 2a and 2b while traveling on a downhill road. However, it is common to perform control (regenerative control) to convert kinetic energy during running into regenerative current and charge the battery 13 .

However, when the battery 13 is fully charged, the regenerative current cannot be received by the battery 13, so regenerative control cannot be performed. A case is assumed in which it is difficult to perform deceleration assistance.

Therefore, even when the battery 13 is fully charged, in order to assist deceleration using the regenerative braking force while traveling on a downhill, a regenerative current exceeding the range that the battery 13 can accept is supplied to the power consuming device. consumption is possible.

However, when the regenerative current is consumed by the power consuming device while traveling on a downhill road, the regenerative current supply destination is switched from the battery 13 to the power consuming device using the selector switch 50 during regenerative braking by the motor 11. However, since a large current is flowing in the circuit during regenerative braking, a spark is generated at the time of switching, which deteriorates the durability of the changeover switch 50 (the contact of the changeover switch 50 wears out) and causes radio waves. Disturbances may occur.

In order to avoid deterioration of the durability of the changeover switch 50 and the occurrence of radio interference, it is conceivable to set the switching timing after the regenerative current is gradually stopped by the inverter 12. Since the power is reduced, unintended acceleration (so-called G loss) may occur.

Therefore, in the present embodiment, a braking force control system configured to generate hydraulic braking force so as to compensate for the decrease in regenerative braking force and to switch the supply destination of regenerative current during generation of the hydraulic braking force. 10 is provided in the electric vehicle 1.

Specifically, the braking force control system 10 controls the braking force of the electric vehicle 1 during downhill running. 11, a chopper circuit 51, and a water cooling resistor 52 that consumes power.

FIG. 2 is a block diagram schematically showing a configuration example of the essential parts of the braking force control system 10. FIG. 2(a) shows the state before full charge, and FIG. 2(b) shows the state after full charge. is shown. Also, FIG. 3 is a time chart schematically showing the auxiliary braking force during running downhill. Note that the "auxiliary braking force" is, for example, a braking force that assists deceleration, other than the braking force generated by the wheel cylinder pressure generated by the driver's operation of the brake pedal 21, among the braking forces required while traveling on a downhill road. means.

As shown in FIGS. 1 and 2, changeover switch 50 is arranged between inverter 12 and battery 13 and is electrically connected to water cooling resistor 52 via chopper circuit 51 . The changeover switch 50 is configured to switch the supply destination of the regenerative current generated by the motor 11 from one of the battery 13 and the water cooling resistor 52 to the other by being controlled by the ECU 30 . The water-cooled resistor 52 is a type of power consuming device, has a heating wire structure, and is configured to consume the lost power by converting electricity into heat. The chopper circuit 51 is a power supply circuit that performs chopper control to artificially generate an arbitrary voltage or current as an effective value from a DC or AC power supply by repeating ON-OFF of current.

Before the battery 13 is fully charged while traveling downhill, the braking force control system 10 utilizes the regenerative braking force as a brake for the electric vehicle 1 as shown in FIG. is converted into a regenerative current and charged to the battery 13. On the other hand, after the battery 13 is fully charged, as shown in FIG. The regenerative braking force is used to assist deceleration while being consumed by the resistor 52 .

Moreover, in the braking force control system 10 of the present embodiment, when it is predicted that the battery 13 will be fully charged by the supply of the regenerative current generated by the motor 11 during regenerative braking by the motor 11 while traveling on a downhill road. , the regenerative current is stopped before the battery 13 is fully charged, and hydraulic braking force is generated by the ESC actuator 25 so as to compensate for the loss of the regenerative braking force, and the hydraulic braking force is generated. The ECU 30 is configured to switch the selector switch 50 inside.

More specifically, at time t0 in FIG. 3 while traveling downhill, (1) the driver depresses the brake pedal 21, (2) the shift is changed to the brake position, or (3) the regenerative lever (see FIG. not shown) is performed, the ECU 30 executes regenerative control to generate regenerative braking force and charge the battery 13 with regenerative current.

Reference numeral 13 a in FIG. 3 schematically represents the SOC of the battery 13 . The ECU 30 predicts that the battery 13 will be fully charged during running downhill when the SOC becomes equal to or greater than a predetermined first charge amount set slightly lower than the full charge, and the regenerative current is supplied to the battery. 13 to the water-cooled resistor 52. Specifically, at time t1 before the battery 13 is fully charged, the ECU 30 issues a command to the inverter 12 to stop the regenerative current, and instructs the brake ECU 26 to compensate for the loss of the regenerative braking force. A command is issued to cause the ESC actuator 25 to generate hydraulic braking force regardless of the operation of the brake pedal 21 by the driver.

Then, the ECU 30 switches the selector switch 50 to switch the supply destination of the regenerative current from the battery 13 to the water cooling resistor 52 during the period from time t1 to time t2 during which the ESC actuator 25 is generating the hydraulic braking force. . When the switching of the supply destination of the regenerative current is completed in this way, the ECU 30 reduces the hydraulic braking force by the ESC actuator 25 at time t2, and returns the regenerative braking force to the state before switching.

In the braking force control system 10 of the present embodiment, voltage (current) can be varied by performing chopper control using the inverter 12 and the chopper circuit 51. Therefore, as shown in FIG. It is possible to smoothly transition from power to hydraulic braking force (or from hydraulic braking force to regenerative braking force).

-effect-
In the braking force control system 10 of the present embodiment, when switching the supply destination of the regenerative current generated by the motor 11 from the battery 13 to the water cooling resistor 52 during regenerative braking by the motor 11 while traveling on a downhill road, the circuit Even if a large current is flowing through the circuit, the inverter 12 is used to stop the regenerative current, so that the value of the current flowing through the circuit can be temporarily lowered. In this way, the selector switch 50 is switched to switch the supply destination of the regenerative current in a state in which the value of the current flowing through the circuit is reduced. It is possible to prevent deterioration of the durability of the changeover switch 50 and occurrence of radio wave interference.

However, when the regenerative current is stopped, the regenerative braking force also disappears. Since the regenerative current supply destination is switched from the battery 13 to the water-cooled resistor 52 by 50, it is possible to suppress the occurrence of unintended acceleration.

Then, after switching the changeover switch 50, the regenerative braking force is restored to the state before switching, so that before switching (regenerative braking force), during switching (hydraulic braking force), and after switching (regenerative braking force) Through this, it is possible to cause the water-cooling resistor 52 to consume regenerative current exceeding the acceptable range of the battery 13 while maintaining a constant auxiliary braking force.

- Control flow -
Next, a specific example of control by the braking force control system 10 of this embodiment will be described with reference to the flowchart shown in FIG.

First, in step S<b>1 , the ECU 30 determines whether or not the electric vehicle 1 is running downhill based on the gradient detected by the gradient sensor 48 . If the determination in step S1 is NO, the control by the braking force control system 10 does not need to be executed, so END is performed as it is. On the other hand, if the determination in step S1 is YES, the process proceeds to step S2.

In the next step S2, the ECU 30 determines whether or not the brake pedal 21 has been depressed and whether or not the shift has been changed to the brake position based on the detection results of the brake pedal position sensor 46, the shift position sensor 43, and the like. , and whether or not an ON operation of a regenerative lever or the like has been performed. If the determination in step S2 is NO, that is, if no operation has been performed, the control by the braking force control system 10 does not need to be executed, so END is performed.

On the other hand, if the determination in step S2 is YES, that is, if at least one operation has been performed, the process proceeds to step S3.

In the next step S3, the ECU 30 determines whether the SOC is greater than or equal to the first charge amount based on the integrated value of the charging/discharging current of the battery 13 detected by the current sensor. If the determination in step S3 is NO, END while regenerative control is being executed. On the other hand, if the determination in step S3 is YES, the process proceeds to step S4.

In the next step S4, the ECU 30 issues a command to the inverter 12 to stop the regenerative current, issues a command to the brake ECU 26 so as to compensate for the loss of the regenerative braking force, and generates a hydraulic braking force by the ESC actuator 25. After that, the process proceeds to step S5.

In the next step S5, the ECU 30 switches the selector switch 50 to switch the supply destination of the regenerative current from the battery 13 to the water cooling resistor 52, and then proceeds to step S6. In the next step S6, the ECU 30 returns the regenerative braking force to the state before switching while reducing the hydraulic braking force by the ESC actuator 25, and then ENDs.

-Modification of Embodiment 1-
Next, a modification of the first embodiment will be described.

<Modification 1>
This modification differs from the first embodiment in that, when switching the supply destination of the regenerative current generated by the motor 11, the regenerative current is reduced rather than stopped. Hereinafter, the points different from the first embodiment will be mainly described.

FIG. 5 is a time chart schematically showing the auxiliary braking force during running downhill according to this modified example. For example, if the electric vehicle 1 is a compact vehicle, even if regeneration control is performed while traveling on a downhill road, it is unlikely that a large current will flow through the circuit, and there is little concern that a spark will occur when the selector switch 50 is switched. . Therefore, in this modification, the inverter 12 is not controlled to gradually stop the regenerative current.

However, there is a possibility that unintended acceleration occurs when switching the selector switch 50 . Therefore, in this modification, when switching the supply destination of the regenerative current generated by the motor 11 from the battery 13 to the water-cooled resistor 52 in order to keep the braking force constant, as shown in FIG. Before the battery is fully charged, the regenerative current is reduced and a relatively small hydraulic braking force is generated by the ESC actuator 25 so as to compensate for the reduction in the regenerative braking force.

For safety reasons, the ECU 30 is configured so that the changeover switch 50 is switched between time t1' and time t2' when the hydraulic braking force by the ESC actuator 25 is generated according to the target value. there is

According to this modification, appropriate braking force control can be performed according to the size of the electric vehicle 1 .

<Modification 2>
This modification differs from the first embodiment in that the supply destination of the regenerative current generated by the motor 11 is switched from the power consumption device to the battery 13 . Hereinafter, the points different from the first embodiment will be mainly described.

FIG. 6 is a time chart schematically showing the auxiliary braking force during running downhill according to this modified example. When the regenerative current generated by the motor 11 is directly supplied to the water-cooled resistor 52, when the SOC of the battery 13 decreases (below the predetermined second charging amount), the regenerative current is supplied to the battery 13. need to switch.

However, even when switching the supply destination of the regenerative current from the water-cooled resistor 52 to the battery 13, a spark is generated at the time of switching, which may deteriorate the durability of the changeover switch 50 or cause radio interference. have a nature. Further, if switching is performed after the regenerative current is gradually stopped by the inverter 12, unintended acceleration may occur.

Therefore, in this modification, when switching the supply destination of the regenerative current generated by the motor 11 from the water cooling resistor 52 to the battery 13 in order to keep the braking force constant, as shown in FIG. Before the SOC becomes less than the second filling amount, the regenerative current is stopped and the hydraulic braking force is generated by the ESC actuator 25 so as to compensate for the loss of the regenerative braking force. The ECU 30 is configured to switch the selector switch 50 between certain time t1'' and time t2''.

According to this modification, even when the regenerative current supply destination is switched from the water-cooled resistor 52 to the battery 13 while traveling on a downhill road, unintended acceleration occurs while suppressing the generation of sparks at the time of switching. can be restrained.

(Embodiment 2)
This embodiment differs from the first embodiment in that the auxiliary braking force is switched from the regenerative braking force by the motor 11 to the braking force by the electromagnetic retarder 60 during regenerative braking by the motor 11 while traveling downhill. be. The same reference numerals are assigned to the same configurations as in the first embodiment, and the points different from the first embodiment will be mainly described below.

FIG. 7 is a diagram schematically showing an electric vehicle 1' provided with a braking force control system 10' according to this embodiment. Unlike the electric vehicle 1 of Embodiment 1, this electric vehicle 1' does not include a selector switch 50, a chopper circuit 51 and a water-cooled resistor 52. Instead of these, as shown in FIG. A retarder 60 and a retarder ECU 61 are provided.

The braking force control system 10' controls the braking force of the electric vehicle 1' running downhill, and includes a motor 11, an inverter 12, a battery 13, an ESC actuator 25, an ECU 30, an electromagnetic It is configured including a retarder 60 and a retarder ECU 61 .

FIG. 8 is a block diagram schematically showing a configuration example of a main part of the braking force control system 10', where (a) shows the state before full charge, and (b) shows the state after full charge. state. FIG. 9 is a time chart schematically showing the auxiliary braking force during running downhill. As shown in FIG. 8 , the electromagnetic retarder 60 is attached to the drive shaft 5 , and is supplied with current from the battery 13 via the retarder ECU 61 . ' gives a braking force. More specifically, the electromagnetic retarder 60 has a large number of electromagnets (not shown) arranged in a circumferential direction, and the excitation current of the electromagnets is controlled by the retarder ECU 61 to generate a braking force corresponding to the excitation current. , the rotation of the drive shaft 5 is braked, and accordingly the rotation of the drive wheels 2a and 2b is braked. Note that the retarder ECU 61 is controlled by the ECU 30 .

Before the battery 13 is fully charged while traveling on a downhill road, the braking force control system 10' utilizes the regenerative braking force as a brake for the electric vehicle 1' as shown in FIG. While performing regeneration control to convert kinetic energy into regenerative current and charge the battery 13, after the battery 13 is fully charged, as shown in FIG. is configured to assist deceleration using the braking force of the electromagnetic retarder 60 by supplying a current to . As described above, in the present embodiment, the auxiliary braking force is switched from the regenerative braking force by the motor 11 to the braking force by the electromagnetic retarder 60. Since the inverter 12 and the retarder ECU 61 can be used as a changeover switch, the changeover switch 50 can be omitted.

However, when regenerative control is stopped while the regenerative current is being supplied to the battery 13 while traveling downhill, and the current from the battery 13 is used to operate the electromagnetic retarder 60, the regenerative control is stopped. There is a problem that it is difficult to keep the braking force constant until switching to the electromagnetic retarder 60 after switching to the electromagnetic retarder 60 .

Therefore, in the braking force control system 10' of the present embodiment, it is predicted that the battery 13 will be fully charged by the supply of the regenerative current generated by the motor 11 during regenerative braking by the motor 11 while the vehicle is traveling downhill. In this case, the regenerative current is stopped before the battery 13 is fully charged, and hydraulic braking force is generated by the ESC actuator 25 so as to compensate for the share of the regenerative braking force, and the hydraulic braking force is generated. The ECU 30 is configured to supply current from the battery 13 to the electromagnetic retarder 60 .

More specifically, at time t0 in FIG. 9 while traveling on a downhill, (1) depression of the brake pedal 21, (2) shift change to the brake position, or (3) ON operation of a regenerative lever or the like is performed. When performed, the ECU 30 executes regenerative control to generate regenerative braking force and charge the battery 13 with regenerative current.

The ECU 30 predicts that the battery 13 will be fully charged during running downhill when the SOC becomes equal to or greater than a predetermined first charge amount, and the ECU 30 predicts that the regenerative braking force of the motor 11 will be switched to the braking force of the electromagnetic retarder 60 . Start preparing. Specifically, at time t1 before the battery 13 is fully charged, the ECU 30 issues a command to the inverter 12 to stop the regenerative current, and commands the brake ECU 26 to compensate for the share of the regenerative braking force. to generate the hydraulic braking force by the ESC actuator 25 regardless of the operation of the brake pedal 21 by the driver.

Then, the ECU 30 issues a command to the retarder ECU 61 to cause the electromagnetic retarder 60 to generate braking force between time t1 and time t2 during which the ESC actuator 25 is generating the hydraulic braking force.

-effect-
In the braking force control system 10' of the present embodiment, during regenerative braking by the motor 11, the regenerative current is stopped and the hydraulic braking force is generated by the ESC actuator 25 so as to compensate for the share of the regenerative braking force. Since the current is supplied from the battery 13 to the electromagnetic retarder 60 while the hydraulic braking force is being generated, before switching (regenerative braking force), during switching (hydraulic braking force), and after switching (braking force by the electromagnetic retarder). , the braking force can be kept constant. Therefore, even when the regenerative braking force of the motor 11 is switched to the braking force of the electromagnetic retarder 60 because the battery 13 is fully charged while traveling on a downhill road, unintended acceleration can be suppressed. can.

(Other embodiments)
This invention is not limited to embodiments and can be embodied in various other forms without departing from its spirit or essential characteristics.

In each of the above embodiments, the present invention is applied to the electric vehicle 1, but the present invention is not limited to this, and is applied to a fuel cell vehicle (FCEV vehicle) in which a motor is driven by electric power generated using hydrogen, for example. You may

Further, in the first embodiment and its modified example, the water-cooled resistor 52 is used as the power consumption device, but it is not limited to this, and other devices may be used.

Furthermore, in each of the above-described embodiments, (1) depression of the brake pedal 21 by the driver, (2) shift change to the brake position, or (3) ON operation of a regenerative lever or the like is performed as a trigger. However, not limited to this, for example, the regenerative braking force may be generated with an operation other than these (1) to (3) as a trigger, or some operation The regenerative braking force may be generated in order to improve fuel efficiency even without the

Thus, the above-described embodiments are merely examples in all respects and should not be construed in a restrictive manner. Furthermore, all modifications and changes within the equivalent scope of claims are within the scope of the present invention.

INDUSTRIAL APPLICABILITY According to the present invention, unintended acceleration can be suppressed even when the regenerative braking force is reduced (or stopped) while traveling on a downhill road. extremely useful.

1 Electric vehicle (electric vehicle)
10 braking force control system 11 motor 13 battery 25 ESC actuator (hydraulic pressure generator)
30 ECU (control unit)
50 changeover switch 52 water cooling resistor (power consumption device)
60 electromagnetic retarder

Claims (3)

A braking force control system for controlling the braking force of an electric vehicle running downhill,
a rechargeable battery mounted on the electric vehicle;
a motor that applies regenerative braking force to the electric vehicle by power generation;
a changeover switch capable of switching a supply destination of the regenerative current generated by the motor;
a hydraulic pressure generator that applies a hydraulic braking force to the electric vehicle;
a power consumption device that consumes power and is mounted on the electric vehicle;
a control device that switches a supply destination of the regenerative current generated by the motor from one of the battery and the power consumption device to the other by controlling the changeover switch;
When switching the supply destination of regenerative current generated by the motor during regenerative braking by the motor while traveling downhill, the control device reduces the regenerative current and compensates for the decrease in regenerative braking force. A braking force control system characterized in that the hydraulic braking force is generated by the hydraulic pressure generating device so as to compensate, and the switching switch is switched while the hydraulic braking force is being generated. In the braking force control system according to claim 1,
When it is predicted that the battery will be fully charged by the supply of the regenerative current generated by the motor during regenerative braking by the motor while traveling on a downhill road, the control device fully charges the battery. Before the power consumption device becomes A braking force control system characterized by: A braking force control system for controlling the braking force of an electric vehicle running downhill,
a rechargeable battery mounted on the electric vehicle;
a motor that applies regenerative braking force to the electric vehicle by power generation;
a hydraulic pressure generator that applies a hydraulic braking force to the electric vehicle;
an electromagnetic retarder that applies a braking force to the electric vehicle by being supplied with electric current;
and a control device capable of controlling charging and discharging of the battery,
When it is predicted that the battery will be fully charged by the supply of the regenerative current generated by the motor during regenerative braking by the motor while traveling on a downhill road, the control device fully charges the battery. Before becoming, the regenerative current is stopped, and the hydraulic braking force is generated by the hydraulic pressure generator so as to compensate for the share of the regenerative braking force, and during the generation of the hydraulic braking force, the electromagnetic from the battery A braking force control system, wherein the braking force control system is configured to supply current to the retarder.

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