JP2002067907A - Braking device for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both pedal feeling and brake feeling while effectively utilizing an antilock braking mechanism. SOLUTION: Controls of pressure increase and pressure reduction are carried out while regulating them by carrying out PWM control (duty control) of electromagnetic valves 36, 38 including the antilock mechanism. By carrying out the PWM control (duty control) of a motor of a pump 34, a pedal reaction at the time of controlling the pressure reduction is smoothened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking technique for an electric vehicle including a driving wheel driven by an electric motor among a plurality of wheels supporting a vehicle body, and more particularly to a braking technique for braking a driving wheel. The present invention also relates to a braking technique using both regenerative braking means for braking by regeneration of an electric motor and hydraulic braking means for utilizing hydraulic pressure of hydraulic fluid generated by a master cylinder when a brake pedal is depressed.

[0002]

BACKGROUND OF THE INVENTION Generally, as a braking device for an automobile, hydraulic brake means for supplying hydraulic pressure of a hydraulic fluid generated by a master cylinder to a wheel cylinder in response to depression of a brake pedal and mechanically braking the wheel cylinder is used. . In an electric vehicle, in addition to such mechanical hydraulic braking means, electromagnetic regenerative braking means using an electric motor (drive motor) can be used. The required brake torque required by the electric vehicle is obtained as the sum of the regenerative brake torque by the regenerative brake means and the mechanical brake torque by the conventional general hydraulic brake means. Therefore,
In a braking device of an electric vehicle, a hydraulic pressure control device for generating a mechanical brake torque corresponding to a difference between a required brake torque and a regenerative brake torque is required.

As this hydraulic pressure control device, it is conceivable to utilize a brake optimization control mechanism for appropriately controlling mechanical braking torque by hydraulic pressure braking means for a running electric vehicle, such as antilock control and vehicle attitude control. . These brake optimization control mechanisms aim at safe and comfortable running of the automobile, and are necessary mechanisms not only for ordinary automobiles powered by an internal combustion engine but also for electric automobiles. In addition, the brake optimization control mechanism can perform pressure reduction control for releasing the hydraulic pressure of the wheel cylinder to the reservoir and pressure increasing control for increasing the hydraulic pressure of the wheel cylinder. Therefore, by using the brake optimization control mechanism provided in the electric vehicle, a relatively low-cost braking device for the electric vehicle can be provided without adding a new hydraulic pressure control device. In this regard, for example, JP-A-7-336805 discloses an example in which an antilock control mechanism is used as a hydraulic pressure control device for an electric vehicle.

[0004]

Incidentally, such a brake optimization control mechanism includes a pump for returning the hydraulic fluid released from the wheel cylinder to the reservoir to the master cylinder side. The anti-lock control is a control in which the number of operations performed in accordance with the locking tendency is small, whereas a normal brake operation is a large number of times and is a natural operation. During frequent braking, as compared to anti-lock control, the pump will kick back on the brake pedal with each braking operation. Also, when considering coordination with the regenerative braking means indicating a gradual change in brake torque, a change in brake torque by the brake optimization control mechanism (or
Smooth and gentle hydraulic pressure control is also required for pressure reduction control and pressure increase control.

An object of the present invention is to provide a braking device for an electric vehicle that can improve both pedal feeling and brake feeling while effectively utilizing a brake appropriateness control mechanism attached to the vehicle. . Another object of the present invention is to provide a technique capable of obtaining a good depression feeling of a brake pedal without providing a pedal simulator. Other objects of the present invention will become clear from the following description.

[0006]

According to the present invention, the electromagnetic valve included in the brake appropriateness control mechanism is subjected to PWM control (duty control) to perform both pressure increase and pressure reduction control while limiting the pump motor. Also, by performing PWM control (duty control), the pedal reaction at the time of pressure reduction control is made smooth.

Further, in order to suppress abrupt movement of hydraulic fluid due to control and abrupt change in brake torque, brake fluid pressure control for a wheel cylinder of a part of a plurality of front and rear wheels is performed. The brake fluid pressure control for the wheel cylinders of the remaining wheels is alternately performed with a predetermined time difference. From the viewpoint of reducing the yaw moment of the vehicle, it is preferable that the brake fluid pressure control for the front wheel cylinders and the fluid pressure control for the rear wheel cylinders be alternately performed in a short time. By separately performing the brake fluid pressure control of a plurality of wheels in this manner, abrupt movement of the hydraulic fluid accompanying the control is suppressed, and the entire brake torque change accompanying the control of the pressure increase and the pressure decrease can be smoothed. Yes, and smooth pedal reaction during control.

Furthermore, when the pressure reduction control, instead of returning the hydraulic fluid in the reservoir to the master cylinder side each time the control, only when the working fluid volume in the reservoir exceeds a predetermined value Q _1, in the reservoir by a pump It is preferable to return the hydraulic fluid to the master cylinder side. When the pressure reduction control, when hydraulic fluid volume in the reservoir is below a predetermined value Q _1, the time of your next pressure increasing after the pressure reduction control, the hydraulic fluid in the reservoir back to the master cylinder side by the pump I do. This makes it possible to reduce the amount of return of the brake pedal that occurs during the pressure reduction control, and to reduce the amount of extension of the brake pedal accompanying the subsequent pressure increase control. As a result, the pedal stroke characteristics can be improved.

Regarding braking of an electric vehicle, generally,
Steps covered by regenerative braking torque due to regeneration of the electric motor (that is, steps where regenerative braking is fully applied and steps until regenerative braking torque reaches maximum)
The idea that the required braking torque required is obtained only by the regenerative braking is exclusively adopted.
However, at the stage where the required brake torque is covered by the regenerative braking means, another concept of securing the required brake torque with both the regenerative brake torque and the hydraulic brake torque can be adopted. As a result, a good depression feeling of the brake pedal can be obtained without providing a pedal simulator.

[0010]

FIG. 1 shows the overall piping and main control command connection relationship showing an embodiment of an electric vehicle braking apparatus according to the present invention. In the figure, the piping system is indicated by a solid line, and the electric control command is indicated by a broken line. The electric vehicle to be braked is a front-wheel drive four-wheeled vehicle. Two front wheels of the four wheels, that is, the left front wheel F
L and the right front wheel FR are drive wheels driven by the electric motor 10. The remaining two rear wheels, that is, the right rear wheel RR and the left rear wheel RL are driven wheels having no drive source. The four wheels each include a wheel cylinder,
Each wheel cylinder produces a mechanical braking torque for each wheel.

An electric motor 10, which is a driving source for the front wheels, uses a rechargeable battery as an energy source and a motor controller 12 mainly composed of a microcomputer, for example.
Drive control is performed based on a control command from the controller. On the other hand, the electric motor 10 also functions as a generator, and generates a braking torque of a regenerative brake. Therefore, the motor controller 12 is also electrically connected to the brake controller 14 also mainly composed of a microcomputer. The brake controller 14 gives a regenerative brake command to the motor controller 12, and the motor controller 12 gives the brake controller 14 a maximum regenerative brake signal corresponding to the brake torque of the regenerative brake that can be output at the present time, and / or Gives the actual value of the regenerative braking torque. The brake controller 14 is also provided with a signal from a hydraulic pressure sensor P / S for detecting a master cylinder hydraulic pressure and signals from wheel speed sensors 161 to 164 of each wheel. The calculation is performed, and a control command based on the calculation result is sent to the solenoid valve and the pump motor as described later.

Next, let us look at the piping for the hydraulic brake. The master cylinder 18 is a source of hydraulic pressure. The master cylinder 18 generates a hydraulic pressure inside the cylinder through the booster 22 as the brake pedal 20 is depressed. The master cylinder 18 is of a tandem type, and independent brake lines 31 and 32 extend from the primary and secondary hydraulic ports 24p and 24s, respectively, to the wheel cylinders of the respective wheels. Each brake line 3
Reference numerals 1 and 32 denote components for antilock control, that is, a pump 34 driven by a motor M, a normally-open first solenoid valve 36, a normally-closed second solenoid valve 38, and a release. A reservoir 40 is provided. Here, a two-port two-position valve (two two-port two-position valves corresponding to the respective wheel cylinders) is used as the first and second solenoid valves 36 and 38. It goes without saying that a three-port three-position solenoid valve can be used or another solenoid valve can be used. Each brake line 31,
32 further includes a first solenoid valve 36 and a master cylinder 1
A first position communicating with the master cylinder 18 and a second position that generates a relief function when the hydraulic pressure on the upstream side of the first solenoid valve 36 becomes higher than the master cylinder 18 by a predetermined amount or more.
A position-type third electromagnetic valve 43 and a two-position-type fourth electromagnetic valve 44 for communicating and shutting off between the master cylinder 18 side and the suction side of the pump 34 are provided. The third solenoid valve 43 is used to balance hydraulic pressure in the same system or to balance hydraulic pressure in different systems.
The electromagnetic valve 44 can be used to increase braking responsiveness by opening at the time of sudden braking.

[0013]

[Example of Processing in Brake Controller] FIG. 2 is a flowchart showing an example of processing performed in the brake controller 14 in order to distribute the required brake torque required for the electric vehicle to the regenerative brake torque and the hydraulic brake torque. is there. First, in order to know the required brake torque, as shown in step S1, the hydraulic pressure sensor P /
S samples the hydraulic pressure Pm of the master cylinder 18. Then, based on the sampled hydraulic pressure Pm,
In step S2, a predetermined calculation (for example, TB =
α · Pm, α: proportionality constant) to calculate the required required brake torque TB. In the next step S3, a regenerative brake torque Trb is calculated from the required brake torque TB calculated in step S2. For this calculation, the relationship of TB-Trb is set in advance in the ROM in the brake controller 14. Regarding the relationship of TB-Trb, for example, even before the characteristic C1 as shown in FIG. 3, that is, before the regenerative braking torque of the electric motor 10 reaches the maximum, a part of the required braking torque (for example, 25 to 25).
It is preferable that the hydraulic brake torque is set to cover about 35%). In this regard, in the normal concept of prioritizing regenerative braking, before the regenerative braking torque is maximized, as long as the regenerative braking torque can cover the situation,
All required braking torques are covered by regenerative braking torque. According to the characteristic C1, when the brake pedal 20 is operated, a part of the hydraulic fluid flows with the depression from the master cylinder 18 side toward the wheel cylinder, and the feeling of stepping on the plate, which is a problem in braking the electric vehicle, is reduced. Can be eased. Therefore, a good depression feeling of the brake pedal 20 can be obtained without providing a pedal simulator mainly composed of a reservoir. In the characteristic C1 of FIG. 3, the hydraulic brake torque is increased at a constant rate until the regenerative brake torque becomes from zero to the maximum. good. Then, the break point of the characteristic C1 can be reduced, and a better depression feeling of the brake pedal 20 can be obtained.

Next, in step S4, the maximum regenerative braking torque Trbmax is
Get. The motor controller 12 determines Trbmax based on the motor speed and the state of charge of the battery. Then, in the subsequent step S5, the Trb
It is determined whether Trb is greater than max and Trb> T
If rbmax is "YES", Trb is set to Trbmax (step S6), and if "NO", Tb is set to Trb.
rb itself is output to the motor controller 12 (step S7).

In the motor controller 12, Thb = T
Based on the B-Trb, a hydraulic brake torque Thb is calculated (step 8), and then a hydraulic pressure P for obtaining the calculated Thb is obtained (step 9).
ΔP (= P−P) between the current estimated brake fluid pressure Po and
o) is obtained (step 10). Estimated brake fluid pressure Po
Can be obtained by inputting the current master cylinder hydraulic pressure, the operating state of each solenoid valve, and the like to a hydraulic model provided in a microcomputer in the brake controller 14. And in the following steps,
It is determined whether P is positive or negative.
S ”, the pressure increase control, ΔP> 0 is“ NO ”, and if ΔP <0 is“ YES ”, the pressure reduction control, and ΔP> 0 is“ NO ”, In addition, if △ P <0 is “NO”, the holding control is performed.

[0016]

[Another Example of Processing in Brake Controller] In the processing shown in the flowchart of FIG. 2, the regenerative brake signal is transmitted from the motor controller 12 to the brake controller 14, but such transmission of the regenerative brake signal can be eliminated. . FIG. 4 is a flowchart illustrating a process in which transmission of a regenerative brake signal is eliminated. First, in step S41, the hydraulic pressure Pm of the master cylinder 18 is sampled by the hydraulic pressure sensor P / S. Then
Step S42 is performed based on the sampled hydraulic pressure Pm.
, The required deceleration Am is calculated, not as the brake torque. In the following step S43, the estimated vehicle speed Vc is calculated based on the output of the wheel speed sensors 161 to 164. In step S44, the estimated vehicle deceleration (that is, the actual vehicle deceleration is calculated by differentiating the estimated vehicle speed Vc). (Acceleration of the vehicle) is calculated.

The difference ΔA between the calculated required deceleration Am and the estimated vehicle deceleration Ac is determined (step S45), and the deceleration ΔA is multiplied by a pressure conversion coefficient α to obtain a hydraulic pressure. Is converted to the difference ΔP (step S4
6). Thereafter, as described above, the pressure increase control, the pressure decrease control, and the hold control are performed based on the sign of ΔP. In addition, both the regenerative brake signal and the wheel speed sensor signal are taken in,
It can also be used to correct control and check for inconsistencies.

[0018]

[Pressure increase control] FIG. 5 is a flowchart showing an example of pressure increase control. In the pressure increase control, the second solenoid valve (AV) 3
8 is closed (step S51), and the first solenoid valve (EV)
36 is subjected to PWM control (duty control) (step S
57). Therefore, from the above ΔP, the first solenoid valve 3
6 is calculated (step S).
52). The duty ratio Dev increases as ΔP increases (that is, the energization time increases). When it is estimated that the working fluid is contained in the reservoir 40, the motor of the pump 34 performs PWM control (duty control). Therefore, it is determined whether the reservoir liquid amount Qr is larger than Q ₀ (Q ₀ = 0) (step S53), and Qr> Q
_{If 0} is “YES”, the duty ratio Dp of the pump drive is calculated from the PWM duty ratio DEV of the first solenoid valve 36.
Is calculated (step S54), and the pump 34 is driven at the duty ratio Dp (step S55). The duty ratio Dp of the pump drive increases (i.e., the energization time increases) as the PWM duty ratio DEV of the first solenoid valve 36 increases. The reservoir fluid amount Qr is calculated using the estimated wheel cylinder fluid pressure Pw, the valve opening time of the second solenoid valve 38 during pressure reduction control, and the driving time of the motor of the pump 34 as parameters. Therefore, during a series of processing,
Estimation of the reservoir liquid amount Qr (Step S56) and estimation of the wheel cylinder pressure Pw (Step S58). In such pressure increase control, since the first solenoid valve 36 is subjected to the PWM control, the change in the brake fluid pressure accompanying the control is smooth and gradual, and no rapid change is observed in the vehicle deceleration.
In addition, since the motor of the pump 34 is also subjected to the PWM control, the liquid source at the time of increasing the pressure is present in a place other than the master cylinder, which has the effect of suppressing the extension of the pedal stroke.

[0019]

[Depressurization Control] FIG. 6 is a flowchart showing an example of decompression control. In the pressure reduction control, the first solenoid valve (EV) 3
6 is closed (step S61), and the second solenoid valve (AV) is closed.
38 is controlled to open for a minimum time (step S62, PWM control may be performed instead of the minimum-time valve opening control).
At that time, estimated fluid amount Qr in the reservoir 40 is determined whether larger than the predetermined value _{Q 1} (step S65), Qr> Q
₁ is “YES”, the motor of the pump 34 is PWM
Control (duty control) is performed (step S66). The predetermined value Q _1, and Q _1> Q _0, moreover, also not values impede the antilock control is started during the pressure reduction control. The anti-lock control is a control that takes precedence over the control of the regenerative brake, and the reservoir 40 must always have a capacity sufficient to receive the hydraulic pressure of the hydraulic fluid on the wheel cylinder side so that the wheels do not lock. It is. Also in this case, during the series of processes, the estimation of the wheel cylinder fluid pressure Pw (step S63), the estimation of the reservoir fluid quantity Qr (step S64), and the estimation of the reservoir fluid quantity Qr after driving the pump (step S67) are also performed. is there. In such pressure reduction control, since the second electromagnetic valve 38 is subjected to valve opening control or PMW control for a minimum time, the pressure can be reduced gradually, and no rapid change is observed in the vehicle deceleration. Moreover, by performing the PWM control of the motor of the pump 34, the reaction force to the brake pedal 20 is also smooth. Moreover, the pump 3 is the reservoir fluid amount Qr is equal to or less than a predetermined value Q ₁
Since the motor No. 4 is not driven, the return amount of the brake pedal 20 is reduced, and the brake feeling can be more effectively improved.

[0020]

[Holding Control] FIG. 7 is a flowchart showing an example of holding control. During the transition from the pressure increasing control to the pressure decreasing control and during the transition from the pressure decreasing control to the pressure increasing control, the first solenoid valve (E
V) 36 and the second electromagnetic valve (AV) 38 are both closed to control to maintain the hydraulic pressure constant. However, when the master cylinder hydraulic pressure Pm = the wheel cylinder hydraulic pressure Pw or the regenerative brake torque Trb is zero, the holding control is not performed, and the solenoid valves 36 and 38 are moved to their normal positions (the first solenoid valve 36 is opened). , The second solenoid valve 38 is closed).

In the above control, each solenoid valve 36, 38 for each wheel cylinder of a plurality of wheels can be simultaneously controlled.
That is, in the case of the pressure increase control and the pressure decrease control, it is preferable that the front wheel side and the rear wheel side are alternately controlled with a time difference. As a result, abrupt movement of the hydraulic fluid can be avoided, the change in the stroke of the brake pedal 20 can be made smoother, and the reaction force to the brake pedal 20 can be made gentler. The feeling of the brake pedal 20 can be improved.

[0022] In the embodiment described above, although the predetermined value Q ₀ of the reservoir fluid was set to zero, greater than zero predetermined value Q _0,
And set smaller than _{Q 1 (0 <Q 0 <} Q 1), the pressure increase control Gotoki only when the reservoir fluid amount Qr of Qr> _{Q 0,} to PWM control (duty control) of the motor of the pump 34 You may do it.

The present invention can be applied not only to electric vehicles that are driven entirely by electric energy (so-called pure electric vehicles) but also to hybrid vehicles that are driven by a combination of electric energy and other energy. Furthermore, the present invention can be applied not only to four-wheeled vehicles but also to multi-axle vehicles, for example, a single-axle front vehicle and a 2-axle rear vehicle.

The motor of the pump 34 is PWM-controlled during the hydraulic pressure control for coordination between the regenerative brake and the hydraulic brake. However, in the antilock control, the motor of the pump 34 is not controlled by the PWM control as usual. , Or by increasing the duty ratio.

[Brief description of the drawings]

FIG. 1 is a connection diagram of piping and the like showing an embodiment of a braking device of the present invention.

FIG. 2 is a flowchart illustrating an example of a process in a brake controller.

FIG. 3 is a characteristic diagram showing a relationship between TB and Trb.

FIG. 4 is a flowchart showing another example of the processing in the brake controller.

FIG. 5 is a flowchart illustrating an example of pressure increase control.

FIG. 6 is a flowchart illustrating an example of pressure reduction control.

FIG. 7 is a flowchart illustrating an example of a holding control.

[Explanation of symbols]

 Reference Signs List 10 electric motor 12 motor controller 14 brake controller 161 to 164 wheel speed sensor 18 master cylinder 34 pump 36 first solenoid valve 38 second solenoid valve 40 reservoir

[Procedure amendment]

[Submission date] September 27, 2000 (2009.2)
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

[0018]

[Pressure increase control] FIG. 5 is a flowchart showing an example of pressure increase control. In the pressure increase control, the second solenoid valve (AV) 3
8 is closed (step S51), and the first solenoid valve (EV)
36 is subjected to PWM control (duty control) (step S
57). Therefore, from the above ΔP, the first solenoid valve 3
6 is calculated (step S).
52). The duty ratio Dev increases as ΔP increases (that is, the energization time increases). When it is estimated that the working fluid is contained in the reservoir 40, the motor of the pump 34 performs PWM control (duty control). Therefore, it is determined whether the reservoir liquid amount Qr is larger than Q ₀ (Q ₀ = 0) (step S53), and Qr> Q
_{If 0} is “YES”, the duty ratio Dp of the pump drive is calculated from the PWM duty ratio DEV of the first solenoid valve 36.
Is calculated (step S54), and the pump 34 is driven at the duty ratio Dp (step S55). The duty ratio Dp of the pump drive increases (i.e., the energization time increases) as the PWM duty ratio DEV of the first solenoid valve 36 increases. The reservoir fluid amount Qr is calculated using the estimated wheel cylinder fluid pressure Pw, the valve opening time of the second solenoid valve 38 during pressure reduction control, and the driving time of the motor of the pump 34 as parameters. Therefore, during a series of processing,
Estimation of the reservoir liquid amount Qr (Step S56) and estimation of the wheel cylinder pressure Pw (Step S58). In such pressure increase control, since the first electromagnetic valve 36 is PWM- controlled, the change in brake fluid pressure accompanying the control is smooth and gradual, and there is no rapid change in vehicle deceleration.
Further, since the motor of the pump 34 is also subjected to PWM control, the liquid source at the time of increasing the pressure is present in a place other than the master cylinder, which has the effect of suppressing the extension of the pedal stroke.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

[0019]

[Depressurization Control] FIG. 6 is a flowchart showing an example of decompression control. In the pressure reduction control, the first solenoid valve (EV) 3
6 is closed (step S61), and the second solenoid valve (AV) is closed.
38 is controlled to open for a minimum time (step S62, PWM control may be performed instead of the minimum-time valve opening control).
At that time, estimated fluid amount Qr in the reservoir 40 is determined whether larger than the predetermined value _{Q 1} (step S65), Qr> Q
₁ is “YES”, the motor of the pump 34 is PWM
Control (duty control) is performed (step S66). The predetermined value Q _1, and Q _1> Q _0, moreover, also not values impede the antilock control is started during the pressure reduction control. The anti-lock control is a control that takes precedence over the control of the regenerative brake, and the reservoir 40 must always have a capacity sufficient to receive the hydraulic pressure of the hydraulic fluid on the wheel cylinder side so that the wheels do not lock. It is. Also in this case, during the series of processes, the estimation of the wheel cylinder fluid pressure Pw (step S63), the estimation of the reservoir fluid quantity Qr (step S64), and the estimation of the reservoir fluid quantity Qr after driving the pump (step S67) are also performed. is there. In such pressure reduction control, since the second electromagnetic valve 38 is subjected to valve opening control or PWM control for the minimum time, the pressure can be reduced gradually, and no rapid fluctuation is observed in the vehicle deceleration. Moreover, by controlling the motor of the pump 34 by PWM , the reaction force to the brake pedal 20 is also smooth. Moreover, the pump 3 is the reservoir fluid amount Qr is equal to or less than a predetermined value Q ₁
Since the motor No. 4 is not driven, the return amount of the brake pedal 20 is reduced, and the brake feeling can be more effectively improved.

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoru Sumiai 5-2931, Urago-cho, Yokosuka-shi, Kanagawa F-term in Bosch Brake System Co., Ltd. (Reference) 3D046 AA09 BB03 BB28 CC02 CC06 DD04 EE01 FF05 HH36 LL02 LL05 LL23 LL37 LL46 LL50 5H115 PA01 PG04 PU01 QI04 QI12 QI15 TO23 TO26 UI22

Claims (6)

[Claims] 1. A regenerative brake means for electromagnetically braking by regenerative operation of an electric motor, and a hydraulic pressure for mechanically braking by supplying a hydraulic pressure of a hydraulic fluid generated by a master cylinder to a wheel cylinder upon depression of a brake pedal. Brake means, and the required brake torque required for the electric vehicle,
A braking device for an electric vehicle obtained by a regenerative braking torque by said regenerative braking means and a mechanical braking torque by said hydraulic pressure braking means, wherein said hydraulic brake is applied to said electric vehicle traveling such as anti-lock control or vehicle attitude control. Means for appropriately controlling the mechanical braking torque by the means, and utilizing the braking appropriateness control mechanism, the mechanical braking torque corresponding to the difference between the required brake torque and the regenerative braking torque. In the braking device for an electric vehicle, the brake optimization control mechanism communicates between the master cylinder and the wheel cylinder and shuts off a first solenoid valve that can be shut off, and shuts off between the wheel cylinder and the reservoir. , A second solenoid valve that can communicate, and hydraulic fluid in the reservoir. A pump for returning the master cylinder side by driving the motor, a pressure reduction control for communicating the second solenoid valve to release the hydraulic pressure of the wheel cylinder to a reservoir, and a communication for the first solenoid valve. Pressure increase control for increasing the hydraulic pressure of the wheel cylinder is possible, and by performing PWM control on the first and second solenoid valves, both pressure increase and pressure reduction controls are limited. By controlling the motor by PWM,
A braking device for electric vehicles that facilitates pedal reaction during pressure reduction control. 2. The electric vehicle includes a plurality of wheels arranged in front and rear, brake fluid pressure control for a wheel cylinder of some of the plurality of wheels, and brake fluid control for a wheel cylinder of the remaining wheels. 2. The braking device according to claim 1, wherein the pressure control and the pressure control are alternately performed with a predetermined time difference. 3. The braking device according to claim 2, wherein the some wheels are one of a front wheel and a rear wheel, and the remaining wheels are the other of a front wheel and a rear wheel. 4. A time the decompression control, only when the hydraulic fluid amount in the reservoir exceeds a predetermined value Q _1, returning the hydraulic fluid in the reservoir to the master cylinder side by the pump, brake system according to claim 1 . 5. A time the decompression control, hydraulic operating fluid amount in the reservoir when it is less than the predetermined value Q _1, the time of your next pressure increasing after the pressure reduction control by said pump within said reservoir The braking device according to claim 4, wherein liquid is returned to the master cylinder side. 6. In the step of providing the required brake torque by the regenerative braking means, the required brake torque is secured by both the regenerative brake torque and the hydraulic brake torque, thereby providing a pedal simulator. The braking device according to claim 1, wherein a good depression feeling of the brake pedal is obtained without using the brake pedal.