JP5366867B2 - Vehicle brake system - Google Patents

Description

  The present invention relates to a vehicle brake system including a motor that generates a regenerative force and a hydraulic brake that generates a braking force by hydraulic pressure.

  Conventionally, for example, an invention disclosed in Patent Document 1 is known as a vehicle including a motor generator capable of generating braking / driving force on a rear wheel and a mechanical braking device capable of generating braking force based on fluid pressure. ing.

JP 2003-276588 A

  However, in the technique described in Patent Document 1, when performing regenerative cooperative brake control using both the braking force and the regenerative braking force of the mechanical braking device, a control system that increases or decreases the hydraulic pressure in the front and rear wheels is required. There was a problem in that the operation of the unit became frequent, resulting in an increase in the size of the unit.

  An object of the present invention is to provide a vehicle brake system that can perform regenerative cooperative brake control by operating as few solenoid valves as possible, and that can secure a braking force even in the event of a failure.

To achieve the above object, in a vehicle brake system according to the present invention, a tandem master cylinder that generates master cylinder pressure in a first master cylinder chamber and a second master cylinder chamber by operating a brake pedal, and the first master cylinder chamber A hydraulic unit that can store brake fluid, a front wheel system pipe that is connected to the hydraulic unit and supplies brake fluid to a wheel cylinder on the front wheel side to generate a hydraulic braking force, and the front wheel system pipe A rear wheel system pipe connected to the rear wheel side wheel cylinder for generating a hydraulic braking force by supplying brake fluid, the front wheel system pipe and the rear wheel system pipe communicating with the second master cylinder chamber; A first position for shutting off the rear wheel system pipe, and shutting off the front wheel system pipe and the rear wheel system pipe and the second master system. A cut valve having a second position communicating with the rear chamber and the rear wheel system pipe, a motor generator connected to the rear wheel and capable of generating regenerative force, and a liquid in the front wheel system pipe or the rear wheel system pipe A liquid leak detection means for detecting a leak; and when the liquid leak detection means does not detect a liquid leak, the cut valve is set to the first position, and when a liquid leak is detected, the cut valve is set to the second position. A controller for switching to a position , wherein the hydraulic unit includes a supply oil passage to which brake fluid from the first master cylinder chamber is supplied, and a reflux oil passage for returning the brake fluid to the first master cylinder chamber. A pressure-increasing proportional valve that is provided on the supply oil passage and controls a differential pressure between the upstream side and the downstream side; and a first master cylinder chamber that is provided downstream of the pressure-increasing proportional valve; A holding valve that shuts off the front wheel system piping, an accumulator that is provided on the return oil passage and can store brake fluid, and is provided on the return oil passage and is closer to the first master cylinder chamber than the accumulator And a pressure reducing valve provided on the reflux oil passage and disposed closer to the front wheel system piping than the accumulator .

  Since the hydraulic pressure generated in the master cylinder is supplied to the wheel cylinders of the front and rear wheels through one hydraulic pipe through the hydraulic pressure unit, the complexity of the hydraulic pressure unit can be avoided. Further, even when liquid leakage occurs in the front wheel system piping or the rear wheel system piping, the hydraulic pressure can be supplied to one system by shutting off the cut valve, and the braking force can be ensured.

1 is a system diagram illustrating an overview of a vehicle brake system according to a first embodiment. 3 is a circuit diagram illustrating a configuration of a hydraulic unit according to Embodiment 1. FIG. It is the schematic when the front-wheel system piping fails in the brake system of Example 1. FIG. It is the schematic when the rear-wheel system piping fails in the brake system of Example 1. FIG. 3 is a flowchart illustrating a regeneration cooperative control process according to the first embodiment. It is a characteristic view showing the relationship between the pedal effort and braking force of Example 1. It is a characteristic view showing the front-rear braking force distribution characteristic of the brake system of the vehicle of the first embodiment.

  FIG. 1 is a system diagram illustrating an outline of a vehicle brake system according to a first embodiment. The vehicle of the first embodiment is a four-wheel small electric vehicle, and is an electric vehicle having an in-wheel motor MD on the rear wheel. Each of the four wheels is equipped with a hydraulic brake device that generates a braking force by the hydraulic pressure of the brake fluid. Since the hydraulic brake device has a known configuration including a brake rotor and a caliper having a brake pad that operates a wheel cylinder and a piston, the description thereof is omitted.

  A master cylinder MC is connected to the brake pedal BP operated by the driver. The master cylinder MC is a tandem type and has a first master cylinder chamber MC1 and a second master cylinder chamber MC2 that generate the same hydraulic pressure. A spring and a stopper are provided between the pistons separating the first master cylinder chamber MC1 and the second master cylinder chamber MC2, and when the hydraulic pressure in one cylinder chamber does not increase, the driver's pedaling force Is a known configuration that acts on the other cylinder chamber.

  A first oil passage 10 and a second oil passage 11 are connected to the first master cylinder chamber MC1. The first and second oil passages 10 and 11 are connected to a hydraulic unit HU that houses a solenoid valve. Details of the hydraulic unit HU will be described later. A third oil passage 12 is connected to the second master cylinder chamber MC2. The third oil passage 12 is connected to a cut valve CV that can shut off the front wheel side brake system and the rear wheel side brake system.

  In the vehicle brake system according to the first embodiment, the front wheel system pipe LF including the FR pipe 14 connected to the front wheel right wheel cylinder and the FL pipe 15 connected to the front wheel left wheel cylinder, and the rear wheel right wheel. It has a RR pipe 16 connected to the cylinder and a rear wheel system pipe LR composed of an RL pipe 17 connected to the rear wheel left wheel cylinder.

  One main oil passage 13 is connected to the hydraulic unit HU. The main oil passage 13 supplies brake fluid to the front wheel system pipe LF. The main oil passage 13 can supply brake fluid to the rear wheel system pipe LR via the cut valve CV. Between the cut valve CV and the rear wheel system pipe LR, a proportioning valve PV capable of proportionally reducing the hydraulic pressure supplied to the rear wheel system pipe LR is provided. Thereby, even if the wheel load on the rear wheel side decreases due to the load movement during braking, the wheel lock is avoided by suppressing the braking force.

  The cut valve CV connects the main oil passage 13 and the rear wheel system pipe LR when not energized, and disconnects the second master cylinder chamber MC2 and the rear wheel system pipe LR from the first position. The oil passage 12 and the rear wheel system pipe LR are connected to each other, and the second position is provided to block the front wheel system pipe LF and the rear wheel system pipe LR.

  FIG. 2 is a circuit diagram illustrating the configuration of the hydraulic unit according to the first embodiment. The hydraulic unit HU is composed of an aluminum alloy block housing, and a plurality of pipe lines (first oil path 10, second oil path 11, and main oil path 13) are connected to the housing. The housing has a supply oil passage 21 connected to the first oil passage 10 and a reflux oil passage 22 connected to the second oil passage 11.

  A hydraulic pressure sensor 2 that detects a master cylinder pressure is provided on the supply oil passage 21. Further, on the supply oil passage 21, a normally-open pressure-increasing proportional valve HSV that can connect and disconnect the first oil passage 10 and the main oil passage 13, and a pressure-increasing proportional valve HSV and the main oil passage 13 are connected and disconnected. A possible normally open holding valve EV. The pressure-increasing proportional valve HSV is a linear solenoid valve capable of controlling the differential pressure between the upstream side and the downstream side of the supply oil passage 21, and generates a master cylinder pressure on the upstream side and is located on the downstream side. Then, a desired hydraulic pressure is generated. The holding valve EV is provided with a bypass circuit 21a including a check valve 21b that cuts off the supply from the master cylinder side to the wheel cylinder side and allows the opposite flow.

  On the recirculating oil path 22, a check valve 4b that cuts off the supply from the master cylinder side to the wheel cylinder side and allows the opposite flow, and a pump that discharges brake fluid pumped up from the wheel cylinder side to the master cylinder side 4, a motor 3 that drives the pump 4, a check valve 4 a that interrupts the supply from the master cylinder side to the wheel cylinder side and allows the opposite flow, and an accumulator 5 that can store brake fluid at a predetermined pressure, And a normally closed pressure reducing valve AV capable of connecting / disconnecting between the accumulator 5 and the main oil passage 13.

  The controller 100 calculates the brake pedal stroke amount ST detected by the stroke sensor 1, the master cylinder pressure PM detected by the hydraulic pressure sensor 2, the wheel speed Vr detected by the wheel speed sensor (not shown), and the wheel speed. The estimated vehicle speed V and the accelerator pedal opening ACC detected by the accelerator opening sensor are used as input signals. Then, the driving state of the in-wheel motor MD is controlled via the inverter IVT to generate a regenerative braking force, and the electromagnetic valve or the motor in the hydraulic unit HU is driven to generate the friction braking force. Controls the CV position. Details regarding the braking force control will be described later.

(Normal braking during normal operation)
Next, the operation based on the circuit configuration will be described. First, the normal braking action at normal time will be described. When the driver depresses the brake pedal BP, master cylinder pressure is generated. This master cylinder pressure is supplied from the first master cylinder chamber MC1 to the main oil passage 13 via the hydraulic unit HU, and the hydraulic pressure is supplied to the front wheel system pipe LF and the rear wheel system pipe LR. Since the cut valve CV is in the open state, the second master cylinder chamber MC2 and the rear wheel system pipe LR are in a disconnected state. At this time, since the hydraulic pressure is supplied to the rear wheel system pipe LR via the proportioning valve PV, the hydraulic pressure increase gradient is different from that of the front wheel system pipe LF. This avoids the tendency for the rear wheel side to easily lock due to load movement accompanying braking.

(Action at the time of failure)
Next, the operation at the time of failure of the brake pipe will be described. FIG. 3 is a schematic diagram when the front wheel system piping fails in the brake system of the first embodiment. In the controller 100, if the master cylinder pressure does not increase by the hydraulic pressure sensor 2 when the stroke sensor 1 detects that the brake pedal stroke amount is equal to or greater than a predetermined value, the front wheel system pipe LF or the rear wheel system pipe LR Judge that liquid leakage has occurred due to pipe breakage. At this time, a command to switch the cut valve CV to the second position is output and a command to shut off the holding valve EV is output. As a result, the hydraulic pressure in the second master cylinder chamber MC2 is supplied to the rear wheel system pipe LR via the cut valve CV. That is, it is possible to ensure the braking force of the rear wheel system pipe LR while blocking the brake fluid outflow to the front wheel system pipe LF by the holding valve EV and the cut valve CV.

  FIG. 4 is a schematic diagram when the rear-wheel system piping has failed in the brake system of the first embodiment. As in the case of the failure of the front wheel system pipe LF, when the value of the stroke sensor 1 and the value of the hydraulic pressure sensor 2 are not matched, a command for switching the cut valve CV to the second position is output. Thereby, the hydraulic pressure in the first master cylinder chamber MC1 is supplied to the front wheel system pipe LF, and the supply to the rear wheel system pipe LR is shut off. That is, the braking force of the front wheel system pipe LF can be ensured.

(Regenerative cooperative control processing)
Next, regenerative cooperative control processing between the in-wheel motor MD and the hydraulic brake device will be described. FIG. 5 is a flowchart illustrating the regeneration cooperative control process according to the first embodiment.
In step S1, it is determined whether or not the accelerator pedal opening is equal to or greater than a predetermined value. If it can be determined that the driver has released the accelerator pedal, the process proceeds to step S2, and otherwise, the process proceeds to step S18. Set to uncontrolled state. This is because the regeneration enhancement is not controlled in the accelerator-on state, and the vehicle can be stably decelerated only by the friction brake when the accelerator and the brake are stepped on simultaneously.
In step S2, the master cylinder pressure PM, the vehicle body speed V, and the wheel speed Vr are read. As the vehicle body speed V, an average value or a maximum value of each wheel speed Vr may be selected as appropriate, or the vehicle body speed may be estimated from a vehicle body deceleration or the like, and is not particularly limited.

In step S3, it is determined whether the master cylinder pressure PM is positive and the brake pedal stroke amount DT is larger than the predetermined stroke amount STopt. If this condition is satisfied, it is determined that there is no failure of the brake system. The process proceeds to S5. Otherwise, it is determined that a failure has occurred in the brake system because the master cylinder pressure is not generated even when the brake pedal is depressed, and the process proceeds to Step S4.
In step S4, a control command for closing the cut valve CV is output. Thereby, even if a failure occurs in the front wheel system pipe LF or the rear wheel system pipe LR, the braking force of one system can be secured.

In step S5, the driver's pedaling force is calculated based on the master cylinder pressure, and the required braking force BA is calculated from the map shown in FIG.
In step S6, the maximum regenerative force BMM of the in-wheel motor MD, the allowable regenerative force BMC, and the slip ratio λ are calculated. Specifically, various braking forces are determined based on the pedaling force-braking force characteristics. FIG. 6 is a characteristic diagram showing the relationship between the pedal effort and the braking force of the first embodiment. First, the braking force of various actuators (in-wheel motor MD and hydraulic brake device) corresponding to the necessary braking force set in step S5 is determined.

  In the reduced speed region where the pedaling force is 65 (N) or less (first predetermined value or less), the braking force is achieved only by the regenerative braking force of the in-wheel motor MD, and the pedaling force is 65 (N) to 175 (N) or less ( The braking force is achieved by the regenerative cooperative control using both the regenerative braking force and the hydraulic braking force in the middle deceleration region (the second predetermined value or less), and in the high deceleration region higher than 175 (N), the hydraulic pressure control is achieved. A braking force is achieved only by power (see FIG. 6). The maximum regenerative force BMM and the allowable regenerative force BMC are set to the same initial value, and the allowable regenerative force BMC is appropriately corrected based on the slip ratio in the next steps S7 and S8. Further, the slip ratio λ represents the degree of deviation between the vehicle body speed V and the wheel speed Vr, and is calculated by, for example, λ = (V−Vr) / V. Basically, the friction force with the road surface increases until the slip ratio λ reaches the slip ratio threshold λopt, and when the slip ratio λ exceeds the slip ratio threshold λopt, the friction force decreases greatly.

In step S7, it is determined whether or not the slip ratio λ is equal to or less than the slip ratio threshold λopt. If the slip ratio λ is equal to or less than λopt, the process proceeds to step S7-1, and the braking force BM is set to BMM. That is, in a situation where no drive wheel slip occurs, the maximum regenerative force can be generated. Otherwise, the process proceeds to step S8.
In step S8, the maximum regenerative force BMM is multiplied by the slip ratio sensitivity Kd (0 <Kd <1) and the allowable regenerative force BMC (initial value is BMM) to calculate a new allowable regenerative force BMC. Next, proceeding to step S8-1, the braking force BM is set to BMC. This is because the regenerative force needs to be reduced in a situation where the RR drive wheel slip occurs, and the new allowable regenerative force BMC reduces the regenerative force so that the ideal braking force distribution is achieved (RR regenerative force in FIG. 7). See: BMM → BMC).

In step S12, it is determined whether the required braking force BA is less than or equal to the regenerative force set in step S10 or S11. If BF ≦ BM, the process proceeds to step S16, and if BF> BM, the process proceeds to step S13.
In step S13, the regenerative amount is set to BM, and in step S14, the control hydraulic pressure Pf controlled by the hydraulic unit HU is determined from the following equation.
Friction braking force BP = required braking force BA−regenerative force BM
Friction braking force BP = front wheel friction braking force BF + rear wheel friction braking force BR
Note that BF and BR are uniquely determined by the characteristics of the proportioning valve PV, for example, there is a relationship such as BR = k · BF (k is a characteristic coefficient determined by PV: see the gradient in FIG. 7). Therefore, the friction braking force of the front and rear wheels can be determined.

  In step S15, an opening / closing control command for the pressure increase proportional valve HSV is output. Specifically, an electromagnetic force based on the differential pressure is applied to the pressure increase proportional control valve HSV so that the upstream side becomes the master cylinder pressure and the downstream side becomes the hydraulic pressure that generates the friction braking force calculated in step S14. Control. If the slip ratio λ exceeds the slip ratio threshold λopt when the differential pressure control is executed by the pressure increasing proportional valve HSV, the holding cylinder EV is closed and the pressure reducing valve AV is opened to quickly reduce the wheel cylinder. To achieve. This achieves a pressure reduction that is quicker than the control response of the pressure increase proportional valve HSV to avoid wheel lock. At this time, the pump 4 is also driven at the same time, whereby the brake fluid stored in the accumulator 5 is returned to the first master cylinder chamber MC1.

In step S16, the regenerative force BM is set to the required braking force BA.
In step S17, a close control command for the pressure increase proportional valve HSV is output. Specifically, an electromagnetic force based on the differential pressure is applied to the pressure-increasing proportional control valve HSV so that the master cylinder pressure is set on the upstream side and the hydraulic pressure is set to 0 on the downstream side. At this time, by opening the pressure reducing valve AV and driving the pump 4, the brake fluid flowing out from the pressure increasing proportional valve HSV is stored in the accumulator 5 and recirculated into the first master cylinder chamber MC1. Thus, only the regenerative braking force is generated while the brake pedal stroke amount is secured to some extent.

(Action of braking force control)
Next, the action of the braking force control based on the control process will be described. FIG. 7 is a characteristic diagram illustrating the front-rear braking force distribution characteristics of the vehicle brake system according to the first embodiment. Hereinafter, this characteristic diagram will be used to explain.
[Brake force control in the reduced speed range]
A case where the driver's brake pedal depression force is 50 (N) will be described as an example. In this case, the necessary braking force is about 500 (N), and all is secured by the regenerative braking force (see FIG. 6). Therefore, since it is not necessary to generate the hydraulic braking force, the necessary braking force is ensured only by the regenerative braking force of the rear wheels. Thus, the relationship between the front and rear wheel braking forces shown at point A in FIG. 7 is shown, and the braking force characteristics greatly deviate from the ideal braking force distribution line. However, when the deceleration is low, the load moves forward in the vehicle. However, there is no problem because the rear wheel slip is less likely to occur even if the braking force is secured only by the rear wheel.

  Since the driver is depressing the brake pedal BP, the brake fluid flows into the hydraulic unit HU from the master cylinder MC by depressing. At this time, the pressure reducing valve AV is opened, the pump 4 is driven, and the pressure difference is maintained while flowing a certain amount of brake fluid by the pressure difference control of the pressure increasing proportional valve HSV. Since the flowing brake fluid is stored in the accumulator 5, an excessive flow rate is returned to the first master cylinder chamber MC1, so that only a regenerative braking force can be generated while securing a certain brake pedal stroke.

[Brake force control in medium deceleration range]
A case where the brake pedal force of the driver is 100 (N) will be described as an example. In this case, the necessary braking force is about 1250 (N), and the regenerative cooperative control is performed by both the regenerative braking force and the hydraulic braking force. As shown in FIG. 6, the maximum regenerative power BMM at the time of pedaling force 100 (N) is about 500 (N). At this time, the front wheel hydraulic braking force is 500 (N) and the rear wheel hydraulic braking force is 250 (N). As a result, the relationship between the front and rear wheel braking forces indicated by point B in FIG. 7 is shown.

  The brake system of the first embodiment is configured such that hydraulic pressure acts on both the front wheel system piping and the rear wheel system piping from one hydraulic pressure unit HU. Therefore, in the region where the regenerative cooperative control is executed, the pressure increase proportional valve HSV is controlled so that the hydraulic braking force set according to the pedal effort is obtained. At this time, the regenerative force is basically controlled so that the braking force on the rear wheel side is constant. In other words, the regenerative force is reduced as the hydraulic braking force on the rear wheel side increases, and the total braking force on the rear wheel side is controlled to be constant. When the road surface friction coefficient is high, the braking force on the rear wheel side is set higher than the ideal braking force distribution characteristic, but there is no problem as long as there is no slip on the rear wheel.

  When the rear wheel starts to slip, the regenerative force is reduced from BMM to BMC according to the slip rate. In this case, control is performed so that the braking force of the rear wheels approaches the ideal braking force distribution characteristic shown in FIG.

[Brake force control in high deceleration range]
A case where the driver's brake pedal depression force is 200 (N) will be described as an example. In this case, the necessary braking force is about 2800 (N), and the braking force is secured only by the hydraulic braking force. At this time, the hydraulic braking force on the front wheel side is 2000 (N), and the hydraulic braking force on the rear wheel side is 800 (N). This relationship is determined by the characteristics of the proportioning valve PV. As a result, the relationship between the front and rear wheel braking forces indicated by point C in FIG. 7 is shown. Since no regenerative braking force is generated, no cooperative control is performed, and the pressure-increasing proportional control valve HSV is also opened.

As described above, the effects listed below can be obtained in the first embodiment.
(1) Connected to the tandem master cylinder MC that generates the master cylinder pressure in the first master cylinder chamber MC1 and the second master cylinder chamber MC2 by the brake pedal operation, and the first master cylinder chamber MC1, and can store the brake fluid. A hydraulic unit HU, connected to the hydraulic unit HU, supplies brake fluid to the wheel cylinder on the front wheel side to generate a hydraulic braking force, and is connected to the front wheel system pipe LF to connect the rear wheel side foil. The rear wheel system piping LR that supplies brake fluid to the cylinder and generates hydraulic braking force, the front wheel system piping LF, and the rear wheel system piping LR are communicated with each other and the second master cylinder chamber MC2 and the rear wheel system piping LR are shut off. The first position, the front wheel system pipe LF and the rear wheel system pipe LR are shut off and the second master cylinder chamber MC2 and the rear wheel system system are arranged. Cut valve CV having a second position communicating with LR, in-wheel motor MD (motor generator) connected to the rear wheel and capable of generating regenerative force, and liquid in front wheel system pipe LF or rear wheel system pipe LR Step S3 (liquid leakage detection means) for detecting leakage, and when no liquid leakage is detected in step S3, the cut valve CV is set to the first position, and when liquid leakage is detected, the cut valve CV is set to the second position. And a controller 100 for switching to.

  Since the hydraulic pressure generated in the master cylinder MC is supplied from the hydraulic unit HU to the front and rear wheels through a single pipe, it is possible to avoid complication of the hydraulic unit HU. In other words, it is not necessary to provide a plurality of solenoid valves corresponding to each wheel in the hydraulic unit that executes regenerative coordination. Further, even when liquid leakage occurs in the front wheel system pipe LF or the rear wheel system pipe LR, the hydraulic pressure can be supplied to one system by shutting off the cut valve CV, and the braking force can be ensured.

(2) The stroke sensor 1 for detecting the stroke amount ST of the brake pedal BP and the hydraulic pressure sensor 2 for detecting the master cylinder pressure are provided. In step S2 (liquid leakage detecting means), the sensor value of the stroke sensor 1 is Liquid leakage is detected when the sensor value of the hydraulic pressure sensor 2 does not increase despite the increase.
In the configuration of the first embodiment, the braking force is generated in the front and rear wheels through the hydraulic unit HU in the normal state, and if the relationship between the stroke amount ST and the master cylinder pressure is observed, somewhere in the piping It can be estimated that a failure has occurred. Moreover, the braking force of the location which has not failed can be ensured only by interrupting the cut valve CV without verifying where the failure has occurred.

(3) The hydraulic unit HU includes a supply oil passage 21 to which brake fluid from the first master cylinder chamber MC1 is supplied, a reflux oil passage 22 for returning the brake fluid to the first master cylinder chamber MC1, and a supply oil passage. 21 is a pressure increasing proportional valve HSV that controls the differential pressure between the upstream side and the downstream side, and is provided downstream of the pressure increasing proportional valve HSV between the first master cylinder chamber MC1 and the front wheel system pipe LF. Holding valve EV to be shut off, accumulator 5 provided on recirculation oil passage 22 and capable of storing brake fluid, and provided on recirculation oil passage 22 and arranged closer to first master cylinder chamber MC1 than accumulator 5 A pump 4 and a pressure reducing valve AV provided on the reflux oil passage 22 and disposed on the front wheel system pipe LF side with respect to the accumulator 5 were provided.
Therefore, the brake pedal stroke can be secured by the accumulator 5 while restricting the hydraulic pressure to the front wheel system pipe LF and the rear wheel system pipe LR, and regenerative cooperative control is executed without causing the driver to feel uncomfortable. Can do.

(4) Step S5 (necessary braking force setting means) for detecting the required braking force requested by the driver is provided, and when the braking force set in step S5 is in the reduced speed range equal to or less than the first predetermined value. Only the regenerative force generated by the in-foil motor MD is generated, and the regenerative force generated by the in-foil motor MD is greater than the first predetermined value and is in the middle deceleration range that is greater than the first predetermined value and less than the second predetermined value. Regenerative cooperative control is executed with the hydraulic braking force, and only the hydraulic braking force is generated when the deceleration region is higher than the second predetermined value.
Therefore, regeneration efficiency can be improved by generating a braking force only with the regenerative force of the rear wheels in a reduced speed range where the load movement is small. In the middle deceleration range, the front and rear wheel braking force distribution characteristics can be improved by operating the hydraulic brake device. In the high deceleration range, braking is performed only by the hydraulic brake device, so that it is possible to approach a more ideal front / rear wheel braking force distribution characteristic.

  (5) When the slip ratio λ exceeds the slip ratio threshold λopt in the middle deceleration range (when a slip more than a predetermined amount occurs in the rear wheel), the regenerative force is reduced. As a result, the rear wheel slip can be avoided without changing the hydraulic pressure control, and a stable braking state can be obtained by approaching the ideal front and rear wheel braking force distribution characteristics.

DESCRIPTION OF SYMBOLS 1 Stroke sensor 2 Hydraulic pressure sensor 3 Motor 4 Pump 5 Accumulator 10 1st oil path 11 2nd oil path 13 Main oil path 21 Supply oil path 22 Recirculation oil path 100 Controller AV Pressure-reducing valve BA Necessary braking force BF Front wheel friction braking force BM Regenerative force BMC Allowable regenerative force BMM Maximum regenerative force BP Brake pedal BP Friction braking force BR Rear wheel friction braking force CV Cut valve EV Holding valve HSV Boosting proportional control valve HU Hydraulic unit LF Front wheel system piping LR Rear wheel system piping MC Master Cylinder MC1 First master cylinder chamber MC2 Second master cylinder chamber MD In-foil motor PV Proportioning valve

Claims (4)

A tandem master cylinder that generates master cylinder pressure in the first master cylinder chamber and the second master cylinder chamber by operating the brake pedal;
A hydraulic unit connected to the first master cylinder chamber and capable of storing brake fluid;
A front-wheel system pipe connected to the hydraulic unit and supplying brake fluid to a wheel cylinder on the front wheel side to generate a hydraulic braking force;
A rear wheel system pipe connected to the front wheel system pipe, supplying brake fluid to a wheel cylinder on the rear wheel side and generating a hydraulic braking force;
A first position that communicates the front wheel system piping and the rear wheel system piping and blocks the second master cylinder chamber and the rear wheel system piping, and blocks the front wheel system piping and the rear wheel system piping. And a cut valve having a second position for communicating the second master cylinder chamber and the rear wheel system piping;
A motor generator connected to the rear wheel and capable of generating regenerative power;
Liquid leakage detection means for detecting liquid leakage in the front wheel system piping or the rear wheel system piping;
A controller that switches the cut valve to the first position when a liquid leak is not detected by the liquid leak detection means; and switches the cut valve to the second position when a liquid leak is detected;
Equipped with a,
The hydraulic unit is
A supply oil passage through which the brake fluid from the first master cylinder chamber is supplied;
A reflux oil passage for returning brake fluid to the first master cylinder chamber;
A pressure-increasing proportional valve that is provided on the supply oil passage and controls a differential pressure between the upstream side and the downstream side;
A holding valve provided downstream of the pressure-increasing proportional valve and blocking between the first master cylinder chamber and the front wheel system piping;
An accumulator provided on the reflux oil passage and capable of storing brake fluid;
A pump provided on the reflux oil passage and disposed closer to the first master cylinder chamber than the accumulator;
A pressure reducing valve provided on the reflux oil passage and disposed on the front wheel system piping side from the accumulator;
Brake system for a vehicle, characterized in that it comprises a. The vehicle brake system according to claim 1,
A stroke sensor for detecting a stroke amount of the brake pedal;
A hydraulic pressure sensor for detecting the hydraulic pressure in the master cylinder chamber;
Provided,
The vehicle brake system according to claim 1, wherein the liquid leak detection means detects a liquid leak when the sensor value of the hydraulic pressure sensor does not increase despite the increase of the sensor value of the stroke sensor. The vehicle brake system according to claim 1 or 2,
Provide necessary braking force setting means for detecting the required braking force requested by the driver,
When the braking force set by the necessary braking force setting means is in a reduced speed range below a first predetermined value, only the regenerative force by the motor generator is generated,
When the vehicle is in a medium deceleration range that is greater than the first predetermined value and less than or equal to a second predetermined value that is greater than the first predetermined value, regenerative cooperative control is executed by the regenerative force and hydraulic braking force of the motor generator. ,
The vehicle brake system according to claim 1, wherein only a hydraulic braking force is generated in a high deceleration range larger than the second predetermined value . The vehicle brake system according to claim 3,
A braking system for a vehicle, characterized in that when the slip more than a predetermined amount occurs on the rear wheel in the middle deceleration range, the regenerative force is reduced .

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