JP5946351B2 - Car equipped with electric negative pressure pump - Google Patents

Description

  The present invention relates to a vehicle equipped with an electric negative pressure pump.

  In a vehicle such as an electric vehicle or a hybrid car, the kinetic energy is converted into electric energy and recovered by the traveling motor functioning as a generator during braking. At this time, the traveling motor becomes a resistance, and the resistance is applied to the wheel as a braking force (regenerative braking).

  This regenerative braking is used together with braking by a hydraulic brake (friction braking). In friction braking, friction braking force is applied to the wheel from the hydraulic brake, and at this time, the kinetic energy of the vehicle is consumed by being converted into thermal energy (friction heat). Therefore, at the time of braking of the vehicle, only a part of the kinetic energy is recovered as electric energy, and most of the kinetic energy is converted into heat energy and is wasted.

  Various proposals for improving the energy recovery efficiency have been made. For example, it has been proposed that only the regenerative braking force is generated without generating the hydraulic braking force by the hydraulic brake until the stroke amount of the push rod interlocked with the brake pedal exceeds a predetermined invalid stroke amount.

JP 2007-55588 A JP 2003-284202 A

  Electric energy (electric power) generated by the traveling motor must be absorbed by the battery (charged to the battery). However, when the battery is fully charged, the regenerative energy cannot be absorbed by the battery. In this case, regeneration by the traveling motor must be limited, and regenerative braking force cannot be applied to the wheels. For this reason, the invalid stroke amount cannot be set large, and with the above-described configuration, the effect of improving the energy recovery efficiency is small.

  An object of the present invention is to provide a vehicle equipped with an electric negative pressure pump capable of improving energy recovery efficiency.

In order to achieve the above object, a vehicle equipped with an electric negative pressure pump according to the present invention includes a brake pedal, a master cylinder, a friction brake that applies a friction braking force to a wheel by hydraulic pressure generated by the master cylinder, and a brake. A booster, an electric negative pressure pump for generating negative pressure supplied to the brake booster, negative pressure detecting means for detecting negative pressure in the negative pressure chamber of the brake booster, and negative pressure detected by the negative pressure detecting means In response to the pressure falling below the on threshold, the electric negative pressure pump is driven, and in response to the negative pressure detected by the negative pressure detecting means rising above the off threshold, the electric negative The pump control means for stopping the pressure pump, the generator that regenerates the rotation of the wheel into electric power and generates the regenerative braking force applied to the wheel, and the operation of the brake pedal are detected. A brake operation detecting means, a regeneration control means for starting a regenerative operation by the generator in response to the operation of the brake pedal being detected by the brake operation detecting means, and an electric power regenerated by the generator A secondary battery to be charged; charge rate detection means for detecting a charge rate of the secondary battery; and when the charge rate detected by the charge rate detection means is equal to or lower than a predetermined first charge rate. A predetermined second charging rate in which the charging rate detected by the charging rate detecting means is larger than the first charging rate, with the threshold value and the off threshold value set to a first on negative pressure value and a first off negative pressure value, respectively. When the above is true, the on-threshold value and the off-threshold value are respectively set to a second on-negative pressure value greater than the first on-negative pressure value and a second off-negative pressure greater than the first off-negative pressure value. To set and a threshold value setting means. The brake booster is coupled to the brake pedal and pushes the master cylinder. When the negative pressure in the negative pressure chamber is equal to or lower than the first on-negative pressure value, the push rod and the When the distance between the master cylinder and the master cylinder is relatively large, and the negative pressure in the negative pressure chamber is equal to or greater than the second on negative pressure value, the distance between the push rod and the master cylinder is relatively small. And a shell that is deformed into a shape.

  According to this configuration, when the brake pedal is operated, the push rod of the brake booster is interlocked with the brake pedal, the master cylinder is pressed by the push rod, and the master cylinder generates hydraulic pressure. A friction braking force is applied from the friction brake to the wheel by the hydraulic pressure generated by the master cylinder.

  The negative pressure in the negative pressure chamber of the brake booster is detected by the negative pressure detection means. When the negative pressure in the negative pressure chamber falls below the on threshold, the electric negative pressure pump is driven, and when the negative pressure in the negative pressure chamber rises above the off threshold, the electric negative pressure pump is stopped. A negative pressure is generated by driving the electric negative pressure pump, and the negative pressure is supplied to the negative pressure chamber of the brake booster.

  When the brake pedal is operated, the operation of the brake pedal is detected by the brake operation detecting means. In response to this, a regenerative operation by the generator is started, the rotation of the wheel is regenerated to electric power, and a regenerative braking force is applied to the wheel. Electric power regenerated by the generator is charged in the secondary battery.

  The charging rate of the secondary battery is detected by the charging rate detection means. When the charging rate of the secondary battery is equal to or lower than the predetermined first charging rate, the on threshold value and the off threshold value are set to the first on negative pressure value and the first off negative pressure value, respectively. When the charging rate of the secondary battery is greater than or equal to the second charging rate that is greater than the first charging rate, the second ON negative pressure value and the first OFF negative value that are larger than the first ON negative pressure value, respectively, The second off negative pressure value is set larger than the pressure value.

  Therefore, in a situation where the charging rate of the secondary battery is relatively small and the amount of electric power that can be regenerated (regenerative amount) is large, the driving of the electric negative pressure pump is suppressed, and the regeneration of electric power by the generator is ensured. The On the other hand, when the charge rate of the secondary battery is relatively large and the regenerative amount is small, the negative pressure in the negative pressure chamber of the brake booster is maintained at a large value, and sufficient friction braking force is applied from the friction brake to the wheels. Is granted.

  The brake booster shell has a relatively large distance between the push rod and the master cylinder when the negative pressure in the negative pressure chamber is the first on-negative pressure value, and the negative pressure in the negative pressure chamber is the second pressure. When the ON negative pressure value is set, the distance between the push rod and the master cylinder is deformed to be relatively small.

  For this reason, in a situation where the charging rate of the secondary battery is relatively small and the regenerative amount is large, the push rod from the position of the push rod when the brake pedal is not operated until the push rod comes into contact with the master cylinder. A large invalid stroke amount, which is a stroke amount, can be secured. As a result, the power can be regenerated by the generator for a relatively long time from the start of operation of the brake pedal until the stroke amount of the push rod reaches the invalid stroke amount, and accordingly, regenerative braking force is applied to the wheels. be able to. On the other hand, when the charging rate of the secondary battery is relatively large and the regenerative amount is small, the invalid stroke amount is small, so that the friction braking force is applied to the wheel in a relatively short time from the start of operation of the brake pedal. be able to.

  According to the present invention, under a situation where the regenerative amount is large, it is possible to suppress driving of the electric negative pressure pump, and it is possible to positively perform power regeneration by the generator. Therefore, the energy recovery efficiency can be improved. On the other hand, in a situation where the regenerative amount is small, a sufficient friction braking force can be quickly applied to the wheels in response to the operation of the brake pedal, and a good braking performance can be exhibited.

FIG. 1 is a diagram schematically showing a configuration of a main part of a vehicle equipped with an electric negative pressure pump according to an embodiment of the present invention. FIG. 2 is a flowchart for defining the start timing of regeneration of electric power by the motor generator. FIG. 3 is a flowchart showing a flow of drive control of the electric negative pressure pump. FIG. 4 is a graph showing an example of setting the on threshold value and the off threshold value. FIG. 5A is a schematic cross-sectional view of a brake booster, showing a state where the distance between the tip of the push rod and the piston of the master cylinder is relatively small. FIG. 5B is a schematic cross-sectional view of the brake booster, showing a state where the distance between the tip of the push rod and the piston of the master cylinder is relatively large.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Vehicle configuration>

  FIG. 1 is a diagram schematically showing a configuration of a main part of a vehicle equipped with an electric negative pressure pump according to an embodiment of the present invention.

  The electric negative pressure pump-equipped vehicle 1 is an electric vehicle using the motor generator 2 as a driving source for traveling. The electric negative pressure pump-equipped vehicle 1 includes front wheels 3FL, 3FR and rear wheels 3RL, 3RR.

  The electric negative pressure pump-equipped vehicle 1 is a rear wheel drive vehicle. Drive shafts 5RL and 5RR extending from the differential gear 4 to the left and right are connected to the left and right rear wheels 3RL and 3RR, respectively. The output shaft of the motor generator 2 is connected to the differential gear 4 via a transmission or the like.

  During acceleration of the vehicle 1 equipped with the electric negative pressure pump, the motor generator 2 functions as a motor. The driving force generated by the motor generator 2 is transmitted to the drive shafts 5RL and 5RR via the transmission and the differential gear 4. As a result, the drive shafts 5RL and 5RR rotate, and the rear wheels 3RL and 3RR rotate together with the drive shafts 5RL and 5RR.

  When braking the vehicle 1 equipped with the electric negative pressure pump, the motor generator 2 functions as a generator. The rotations of drive shafts 5RL and 5RR are transmitted to the output shaft of motor generator 2, and the rotation of the output shaft of motor generator 2 is regenerated into electric power. At this time, the motor generator 2 becomes a resistance, and the resistance is applied to the rear wheels 3RL and 3RR as a regenerative braking force.

  An inverter (INV) 6 is connected to the motor generator 2.

  A secondary battery 7 for storing electric power supplied to the motor generator 2 is connected to the inverter 6.

  When the motor generator 2 is driven, DC power output from the secondary battery 7 is supplied to the inverter 6. Then, the DC power is converted into AC power by the inverter 6, and the AC power after the conversion is supplied from the inverter 6 to the motor generator 2. On the other hand, when the motor generator 2 generates power, AC power output from the motor generator 2 is converted into DC power by the inverter 6, and the secondary battery 7 is charged by the DC power after the conversion.

  Friction brakes 8FL, 8FR, 8RL, 8RR are provided on the left and right front wheels 3FL, 3FR and the left and right rear wheels 3RL, 3RR, respectively. In order to operate the friction brakes 8FL, 8FR, 8RL, 8RR, the electric negative pressure pump-equipped vehicle 1 is provided with a master cylinder 9, a brake booster 10, an electric negative pressure pump 11, and an ABS actuator 12.

  A brake pedal 13 that is operated by the driver's foot is provided in front of the driver's seat in the passenger compartment of the electric negative pressure pump-equipped vehicle 1. When the brake pedal 13 is operated (depressed), the pedaling force input to the brake pedal 13 is amplified by the negative pressure in the negative pressure 33 (see FIG. 5A) of the brake booster 10, and the amplified force is the master. Input to cylinder 9. The negative pressure in the negative pressure chamber 33 of the brake booster 10 is supplied from the electric negative pressure pump 11. In the master cylinder 9, a hydraulic pressure corresponding to the force input from the brake booster 10 is generated. The hydraulic pressure of the master cylinder 9 is transmitted to the wheel cylinders provided in the friction brakes 8FL, 8FR, 8RL, and 8RR via the ABS actuator 12 and the like. A friction braking force is applied to the front wheels 3FL, 3FR and the rear wheels 3RL, 3RR from the friction brakes 8FL, 8FR, 8RL, 8RR, respectively, by the hydraulic pressure of the wheel cylinder.

  The electric negative pressure pump-equipped vehicle 1 is provided with an ECU (electronic control unit) 21 having a configuration including a CPU and a memory.

  A stop lamp switch (STPSW) 22 is connected to the ECU 21. While the brake pedal 13 is depressed, the stop lamp switch 22 is turned on, and when the foot is released from the brake pedal 13, the stop lamp switch 22 is turned off. While the stop lamp switch 22 is on, a stop lamp (brake lamp) disposed at the rear of the electric negative pressure pump-equipped vehicle 1 is lit.

  The ECU 21 is connected to various sensors provided in the electric negative pressure pump-equipped vehicle 1. The various sensors include a brake negative pressure sensor 23 that detects a negative pressure in the negative pressure chamber 33 of the brake booster 10 and a current sensor 24 that detects a current input to and output from the secondary battery 7.

  The ECU 21 controls the motor generator 2 and the electric negative pressure pump 11 based on detection signals input from the stop lamp switch 22 and various sensors.

<Regenerative control>

  FIG. 2 is a flowchart for defining the start timing of regeneration of electric power by the motor generator.

  While the electric negative pressure pump-equipped vehicle 1 is traveling, the ECU 21 repeatedly checks whether or not the stop lamp switch 22 is turned on (step S1).

  When the brake pedal 13 is depressed and the stop lamp switch 22 is turned on (YES in step S1), the inverter 6 is controlled, and the regeneration of electric power by the motor generator 2 is started (step S2).

  When the regeneration of electric power is started, the motor generator 2 becomes a resistance, and the resistance is applied to the rear wheels 3RL and 3RR as a regenerative braking force.

  On the other hand, as described above, when the brake pedal 13 is depressed, friction braking force is applied from the friction brakes 8FL, 8FR, 8RL, 8RR to the front wheels 3FL, 3FR and the rear wheels 3RL, 3RR, respectively.

  Accordingly, in the vehicle 1 equipped with the electric negative pressure pump, when the brake pedal 13 is depressed, regenerative braking by the regenerative braking force and friction braking by the friction braking force function.

<Drive control of electric negative pressure pump>

  FIG. 3 is a flowchart showing a flow of drive control of the electric negative pressure pump.

  While the start switch (ignition key switch) of the vehicle 1 equipped with the electric negative pressure pump is turned on, the ECU 21 refers to the detection signal of the brake negative pressure sensor 23 to constantly monitor the negative pressure of the brake booster 10. .

  Then, it is determined whether or not the absolute value of the negative pressure detected by the brake negative pressure sensor 23 (for example, the absolute pressure at which the vacuum is 0) is equal to or less than the on threshold (step S11).

  While the absolute value of the negative pressure detected by the brake negative pressure sensor 23 is larger than the ON threshold (NO in step S11), the electric negative pressure pump 11 is not driven and is stopped.

  When the brake pedal 13 is depressed and the negative pressure of the brake booster 10 is used to amplify the pedal force, the negative pressure of the brake booster 10 decreases (the degree of vacuum decreases). When the absolute value of the negative pressure detected by the brake negative pressure sensor 23 falls to the on threshold (YES in step S11), the electric negative pressure pump 11 is driven (step S12).

  When the electric negative pressure pump 11 is driven, the negative pressure generated by the electric negative pressure pump 11 is transmitted to the brake booster 10, and the negative pressure of the brake booster 10 increases (the degree of vacuum increases). When the absolute value of the negative pressure of the brake booster 10 reaches the off threshold (YES in step S13), the driving of the electric negative pressure pump 11 is stopped (step S14).

<Setting of on threshold and off threshold>

  FIG. 4 is a graph showing an example of setting the on threshold value and the off threshold value.

  The on-threshold value and the off-threshold value are set according to SOC (State Of Charge) which is a charging rate of the secondary battery 7 in which the secondary battery 7 has an empty state of 0. The SOC is calculated by the ECU 21 based on the detection signal input from the current sensor 24.

When the SOC is equal to or lower than the first charging rate S1, the ON threshold value and the OFF threshold value are set to the first ON negative pressure value P1 _ON and the first OFF negative pressure value P1 _OFF , respectively.

When the SOC is equal to or higher than the second charging rate S2 larger than the first charging rate S1, the on threshold value and the off threshold value are set to the second on negative pressure value P2 _ON and the second off negative pressure value P2 _OFF , respectively.

In a range where the SOC is larger than the first charging rate S1 and smaller than the second charging rate S2, the on threshold is larger than the first on negative pressure value P1 _{ON and} smaller than the second on negative pressure value P2 _ON. Thus, the larger the SOC is, the larger the value is set. Further, the off threshold value is set to a larger value as the SOC is larger in a range larger than the first off negative pressure value P1 _{OFF and} smaller than the second off negative pressure value P2 _OFF .

<Configuration of brake booster>

  5A and 5B are schematic cross-sectional views of the brake booster.

  The brake booster 10 includes a pedal side shell 31 and a cylinder side shell 32. The pedal-side shell 31 and the cylinder-side shell 32 are coupled to each other and provide a negative pressure chamber 33 therebetween. In addition, the brake booster 10 includes a push rod 34 that moves in the opposing direction of the pedal-side shell 31 and the cylinder-side shell 32 in conjunction with the brake pedal 13.

  The master cylinder 9 is coupled to the cylinder side shell 32 of the brake booster 10. One end of the piston 35 of the master cylinder 9 protrudes into the negative pressure chamber 33 and is disposed on the central axis of the push rod 34.

  When the brake pedal 13 is stepped on, the push rod 34 moves to the master cylinder 9 side in conjunction with the brake pedal 13. After the tip of the push rod 34 comes into contact with the piston 35 of the master cylinder 9, when the push rod 34 further moves to the master cylinder 9 side, the piston 35 is pushed by the push rod 34 and hydraulic pressure is generated in the master cylinder 9. .

The cylinder side shell 32 is deformed by the negative pressure in the negative pressure chamber 33. Specifically, when the negative pressure in the negative pressure chamber 33 is equal to or higher than the second ON negative pressure value P2 _ON , the cylinder side shell 32 is not depressed, as shown in FIG. 5A. When the distance between the tip of the push rod 34 and the piston 35 of the master cylinder 9 becomes relatively small, and the negative pressure in the negative pressure chamber 33 is equal to or less than the first ON negative pressure value P1 _ON, it is shown in FIG. 5B. As described above, the distance between the tip of the push rod 34 and the piston 35 of the master cylinder 9 when the brake pedal 13 is not depressed is relatively increased.

Thereby, when the negative pressure in the negative pressure chamber 33 is equal to or lower than the first on-negative pressure value P1 _ON , from the start of the depression of the brake pedal 13 until the tip of the push rod 34 comes into contact with the piston 35 of the master cylinder 9. A large invalid stroke amount that is the stroke amount of the push rod 34 is secured.

  The deformation of the cylinder side shell 32 according to the negative pressure in the negative pressure chamber 33 can be realized, for example, by reducing the rigidity of the cylinder side shell 32. Specifically, in the configuration of the conventional brake booster, the cylinder side shell is formed to a thickness (plate thickness) that hardly deforms, whereas in the brake booster 10, the plate of the cylinder side shell 32 is formed. By making the thickness smaller than the thickness, the cylinder-side shell 32 can be deformed as described above according to the negative pressure in the negative pressure chamber 33. Further, by reducing the number of reinforcing ribs and irregularities formed in the cylinder side shell 32 in the vicinity of the coupling portion between the master cylinder 9 and the cylinder side shell 32, the negative pressure in the negative pressure chamber 33 is reduced. Accordingly, the cylinder-side shell 32 can be deformed as described above.

<Effect>

  As described above, when the brake pedal 13 is operated, the push rod 34 of the brake booster 10 is interlocked with the brake pedal 13, the master cylinder 9 is pressed by the push rod 34, and the master cylinder 9 generates hydraulic pressure. By the hydraulic pressure generated by the master cylinder 9, friction braking force is applied from the friction brakes 8FL, 8FR, 8RL, 8RR to the front wheels 3FL, 3FR and the rear wheels 3RL, 3RR, respectively.

  The negative pressure in the negative pressure chamber 33 of the brake booster 10 is detected by the brake negative pressure sensor 23. When the negative pressure in the negative pressure chamber 33 falls below the on threshold, the electric negative pressure pump 11 is driven, and when the negative pressure in the negative pressure chamber 33 rises above the off threshold, the electric negative pressure pump 11 is stopped. . By driving the electric negative pressure pump 11, a negative pressure is generated, and the negative pressure is supplied to the negative pressure chamber 33 of the brake booster 10.

  When the brake pedal 13 is operated, the stop lamp switch 22 is turned on. In response to this, a regenerative operation by the motor generator 2 is started, the rotation of the wheel is regenerated to electric power, and a regenerative braking force is applied to the wheel. Electric power regenerated by the motor generator 2 is charged in the secondary battery 7.

The ECU 21 detects the SOC that is the charging rate of the secondary battery 7. When the SOC of the secondary battery 7 is equal to or lower than the predetermined first charging rate S1, the on threshold value and the off threshold value are set to the first on negative pressure value P1 _ON and the first off negative pressure value P1 _OFF , respectively. When the SOC of the secondary battery 7 is equal to or higher than the second charging rate S2 larger than the first charging rate S1, the second ON negative pressure value P2 having an ON threshold value and an OFF threshold value larger than the first ON negative pressure value P1 _ON, respectively. The second off negative pressure value P2 _OFF is set larger than the _ON and first off negative pressure value P1 _OFF .

  Therefore, in the situation where the SOC of the secondary battery 7 is relatively small and the amount of electric power that can be regenerated (regenerative amount) is large, the driving of the electric negative pressure pump 11 is suppressed, and the electric power regeneration by the motor generator 2 is prevented. Secured. On the other hand, when the SOC of the secondary battery 7 is relatively large and the regenerative amount is small, the negative pressure in the negative pressure chamber 33 of the brake booster 10 is maintained at a large value, and the friction brakes 8FL, 8FR, 8RL are maintained. , 8RR, a sufficient friction braking force is applied to the front wheels 3FL, 3FR and the rear wheels 3RL, 3RR, respectively.

The cylinder-side shell 32 of the brake booster 10 has a relatively large distance between the push rod 34 and the master cylinder 9 when the negative pressure in the negative pressure chamber 33 is the first ON negative pressure value P1 _ON. When the negative pressure in the negative pressure chamber 33 is the second ON negative pressure value P2 _ON , the distance between the push rod 34 and the master cylinder 9 is deformed to be relatively small.

  Therefore, in a situation where the SOC of the secondary battery 7 is relatively small and the regenerative amount is large, from the position of the push rod 34 when the brake pedal 13 is not operated until the push rod 34 contacts the master cylinder 9 A large invalid stroke amount, which is the stroke amount of the push rod 34, can be secured. Thereby, electric power can be regenerated by the motor generator 2 for a relatively long time from the start of operation of the brake pedal 13 until the stroke amount of the push rod 34 reaches the invalid stroke amount, and accordingly, the rear wheels 3RL, 3RR. A regenerative braking force can be applied to. On the other hand, when the SOC of the secondary battery 7 is relatively large and the regenerative amount is small, the invalid stroke amount is small. Therefore, the front wheels 3FL, 3FR and the rear wheels are relatively short in the time from the start of operation of the brake pedal 13. A friction braking force can be applied to 3RL and 3RR.

  Therefore, under a situation where the regenerative amount is large, the driving of the electric negative pressure pump 11 can be suppressed, and the regeneration of electric power by the motor generator 2 can be actively performed. Therefore, the energy recovery efficiency can be improved. On the other hand, in a situation where the regenerative amount is small, a sufficient friction braking force can be quickly applied to the front wheels 3FL, 3FR and the rear wheels 3RL, 3RR in response to the operation of the brake pedal 13, and good braking performance is achieved. Can be demonstrated.

<Modification>

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

For example, the second charging rate S2 is greater than the first charging rate S1, but may be the same value as the first charging rate S1. In this case, when the SOC is equal to or lower than the first charging rate S1, the ON threshold value and the OFF threshold value are set to the first ON negative pressure value P1 _ON and the first OFF negative pressure value P1 _OFF , respectively, and the SOC is set to the first charging rate S1. When larger than (= second charging rate S2), the ON threshold value and the OFF threshold value are set to the second ON negative pressure value P2 _ON and the second OFF negative pressure value P2 _OFF , respectively.

  Further, the configuration in which the driving force for driving of the motor generator 2 is transmitted to the rear wheels 3RL and 3RR, that is, the configuration of the rear wheel drive vehicle using the rear wheels 3RL and 3RR as drive wheels has been taken up. 1 may be a front-wheel drive vehicle having the front wheels 3FL and 3FR as drive wheels.

  Moreover, although the case where the electric negative pressure pump carrying vehicle 1 was an electric vehicle was taken up, if the brake system which concerns on this invention is a vehicle provided with an electric negative pressure pump as well as an electric vehicle, for example, an engine and a motor Or it can also mount in the hybrid car which mounts a motor generator as a drive source for driving | running | working.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

1 Car equipped with electric negative pressure pump 2 Motor generator (generator)
3FL front wheel (wheel)
3FR Front wheel (wheel)
3RL Rear wheel (wheel)
3RR Rear wheel (wheel)
7 Secondary battery 8FL Friction brake 8FR Friction brake 8RL Friction brake 8RR Friction brake 9 Master cylinder 10 Brake booster 11 Electric negative pressure pump 13 Brake pedal 21 ECU (pump control means, regeneration control means, charge rate detection means, threshold setting means)
22 Stop lamp switch (Brake operation detection means)
23 Brake negative pressure sensor (negative pressure detection means)
32 Cylinder side shell (shell)
33 Negative pressure chamber 34 Push rod

Claims (1)

Brake pedal,
A master cylinder,
A friction brake that applies friction braking force to the wheels by the hydraulic pressure generated by the master cylinder;
Brake booster,
An electric negative pressure pump for generating a negative pressure supplied to the brake booster;
Negative pressure detecting means for detecting negative pressure in the negative pressure chamber of the brake booster;
In response to the negative pressure detected by the negative pressure detecting means decreasing below the ON threshold, the electric negative pressure pump is driven, and the negative pressure detected by the negative pressure detecting means increases above the OFF threshold. In response to the pump control means for stopping the electric negative pressure pump;
A generator for regenerating the rotation of the wheel into electric power and generating a regenerative braking force applied to the wheel;
Brake operation detecting means for detecting operation of the brake pedal;
In response to the operation of the brake pedal being detected by the brake operation detection means, regenerative control means for starting a regenerative operation by the generator;
A secondary battery that is charged by electric power regenerated by the generator;
Charging rate detection means for detecting a charging rate of the secondary battery;
When the charging rate detected by the charging rate detection means is equal to or lower than a predetermined first charging rate, the on threshold value and the off threshold value are respectively set to a first on negative pressure value and a first off negative pressure value; When the charging rate detected by the charging rate detection means is equal to or higher than a predetermined second charging rate that is larger than the first charging rate, the on threshold value and the off threshold value are set to be higher than the first on negative pressure value, respectively. Threshold value setting means for setting a large second on-negative pressure value and a second off-negative pressure value larger than the first off-negative pressure value,
The brake booster is interlocked with the brake pedal to push the master cylinder, and when the negative pressure in the negative pressure chamber is equal to or lower than the first on-negative pressure value, the push rod and the master cylinder When the negative pressure in the negative pressure chamber is equal to or greater than the second ON negative pressure value, the distance between the push rod and the master cylinder is relatively reduced. Equipped with an electric negative pressure pump.

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