JP2009067268A - Vehicular brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular brake device capable of increasing the amount of energy recovered during regenerative braking while attaining the miniaturization, simplification and low cost of the whole device. <P>SOLUTION: The vehicular brake device is provided with a motor M for driving drive wheels RL, RR of the vehicle, and performs regenerative braking making the motor M as a generator at regenerative braking. The vehicular brake device is provided with a master cylinder MC; a brake pedal BP interlocked with the master cylinder MC and operated by a stepping force of a driver; a booster BS for operating the master cylinder MC; wheel cylinders 5a-5d provided on respective wheels of the vehicle; and a first brake circuit 1 for feeding brake liquids which is pressure-raised by the booster BS to at least wheel cylinders 5a, 5b of driven wheels FL, FR. The liquid pressure of the brake liquid (fed to the driven wheels FL, FR) is reduced when performing regenerative braking, and regenerative brake forces of the drive wheels RL, RR are increased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a brake device that controls a brake fluid pressure of a vehicle based on a driver's brake operation and a running state of the vehicle.

2. Description of the Related Art Conventionally, as a brake device applied to an electric vehicle or a hybrid vehicle that performs regenerative braking, a device that performs regenerative cooperative control by combining a hydraulic brake device and a regenerative brake device is known. For example, in the brake device described in Patent Document 1 (hereinafter referred to as the prior art), the hydraulic brake device generates brake hydraulic pressure by a master cylinder to which a booster that increases the brake operation force is connected, and a pump. The brake fluid pressure (control fluid pressure) is also generated by the driving of. By executing regenerative cooperative control using such a conventional hydraulic brake device, the above-described conventional technology achieves downsizing, simplification, and cost reduction of the entire brake device.
JP 2006-21745 A

  In the above-described prior art, in a wheel capable of applying regenerative braking force, when performing regenerative braking, the master cylinder pressure corresponding to the brake operation is applied to the wheel cylinder as a basic hydraulic pressure, and the control hydraulic pressure is applied to the wheel cylinder. To grant. Then, the total braking force is obtained by adding the regenerative braking force generated by the regenerative braking device to the braking force by these hydraulic pressures. When the regenerative braking force fluctuates, the fluctuation is corrected by adjusting the control hydraulic pressure. That is, the driver's required braking force is stably realized by compensating for the shortage of the total braking force due to the fluctuation of the regenerative braking force by the control hydraulic pressure (the braking force). On the other hand, in a wheel to which regenerative braking force cannot be applied, a master cylinder pressure corresponding to the brake operation is applied to the wheel cylinder as a basic hydraulic pressure, and a control hydraulic pressure is applied to the wheel cylinder. That is, only the hydraulic braking force is generated.

  However, since the above-mentioned conventional technology is configured to constantly apply the master cylinder pressure as the basic hydraulic pressure to the wheel cylinder in any wheel, it can be generated by the braking force generated by the master cylinder pressure (basic hydraulic pressure). A regenerative braking force is suppressed. Therefore, there has been a problem that the amount of energy that can be recovered by regeneration is reduced by this amount.

  The present invention has been made paying attention to the above-mentioned problem, and the object thereof is a vehicle capable of increasing the amount of energy that can be recovered during regenerative braking while enabling downsizing, simplification, and cost reduction of the entire device. It is in providing a brake device.

  In order to achieve the above object, a vehicle brake device according to the present invention includes a motor that drives a drive wheel of a vehicle, and in the vehicle brake device that performs regenerative braking using the motor as a generator during regenerative braking, a master cylinder; A brake pedal that is operated by a driver's pedaling force in conjunction with the master cylinder, a booster that operates the master cylinder, a wheel cylinder that is provided on each wheel of the vehicle, and a brake fluid that is boosted by the booster And a first brake circuit that supplies at least the wheel cylinder of the driven wheel to reduce the hydraulic pressure of the brake fluid during regenerative braking and to increase the regenerative braking force of the drive wheel.

  In order to use a conventional hydraulic brake device that directly applies the master cylinder pressure (generated by the driver's brake operation) to the wheel cylinder in a state where the brake pedal and the wheel cylinder are mechanically connected in this way. Therefore, the entire brake device can be reduced in size and simplified, and the cost can be reduced. Further, when performing regenerative braking, the brake hydraulic pressure supplied from the master cylinder to the wheel cylinder of the driven wheel is reduced, while the regenerative braking force of the driving wheel is increased by that amount. Therefore, the amount of energy recovered by regeneration can be increased.

  Hereinafter, the best mode for realizing the vehicle brake device of the present invention will be described with reference to the drawings.

[Vehicle system configuration]
FIG. 1 is a system diagram illustrating an overall configuration of a vehicle to which a vehicle brake device (hereinafter referred to as a brake device) according to a first embodiment is applied. This vehicle is a rear-wheel drive hybrid vehicle that drives the rear wheels RL and RR by using two types of power sources of the engine ENG and the motor M together. This hybrid vehicle has a hybrid system α, a hydraulic brake device β, and a plurality of control units CU.

(Hybrid system to regenerative braking device)
The hybrid system α includes a motor M, a generator G, a power split mechanism P, a speed reducer D, an inverter I, and a battery B, in addition to an engine ENG that is a main power source of the vehicle. Among these, the regenerative braking device γ is configured by the motor M, the inverter I, the battery B, and the like.

  The motor M is an auxiliary power source for the engine ENG, and is an AC synchronous motor that also functions as a generator that generates a regenerative braking force (when the driver operates the brake pedal BP).

  The generator G is an AC synchronous type like the motor M, and is driven by the engine ENG to generate AC power (AC current). The generated AC power is used for charging the battery B or driving the motor M.

  The power split mechanism P is composed of a planetary gear mechanism and is connected to the engine ENG, the motor M, the generator G, and the speed reducer D. The power split mechanism P has a function of switching the power transmission path (and direction), and can transmit the driving force of the engine ENG and the driving force of the motor M to the reduction gear D, respectively. The driving force of these power sources is transmitted to the speed reducer D, and further transmitted to the rear wheels RL and RR via the rear wheel power transmission system, thereby driving the rear wheels RL and RR.

  The power split mechanism P is provided so that the driving force of the engine ENG can be transmitted to the generator G. Generator G is driven by transmitting the driving force of engine ENG to generator G.

  Further, the power split mechanism P is provided so that power from the reduction gear D (that is, the rear wheels RL and RR that are drive wheels) can be transmitted to the motor M. When the brake pedal BP is operated, power from the rear wheels RL and RR is transmitted to the motor M, so that the motor M is driven and functions as a generator that generates regenerative braking force.

  The inverter I is electrically connected to the motor M, the generator G, and the battery B, and is controlled according to a control signal from the hybrid control unit HCU. The inverter I is provided so as to convert a high-voltage DC current supplied from the battery B into AC power (AC current) and supply this AC power to the motor M. The motor M is driven by this AC power. Further, the inverter I is provided so that AC power generated by the generator G can be supplied to the motor M. The motor M can also be driven by this AC power.

  Further, the inverter I is provided so as to convert AC power generated by the generator G into DC power and supply the DC power to the battery B. When the charging state of the battery B is lowered, the battery B can be charged by this DC power.

  Further, the inverter I converts AC power generated by the motor M driven as a generator (generating regenerative braking force) into DC power when the brake pedal BP is operated, and converts the DC power into battery power. B can be supplied. Thereby, the kinetic energy of the vehicle is converted into electric energy and is collected (charged) in the battery B. In this case, the electric power charged in the battery B increases as the power generation resistance (that is, regenerative braking force) by the motor M increases.

  A regenerative braking device γ including a motor M, an inverter I, a battery B, and the like causes the motor M to generate a regenerative braking force corresponding to the brake operation state in response to a control command from the hybrid control unit HCU.

(Hydraulic brake device)
The hydraulic brake device β includes a hydraulic pressure supply source (master cylinder MC, etc.) connected to the brake pedal BP, and wheel cylinders 5a to 5a of each wheel FL, FR, RL, RR of the vehicle connected to the hydraulic pressure supply source. A hydraulic pressure control device HU that supplies the brake hydraulic pressure to 5d, and generates a hydraulic braking force (friction braking force) at each wheel. The hydraulic pressure control device HU includes a hydraulic brake actuator (a pump P as another hydraulic pressure supply source that operates independently of the operation of the brake pedal BP, a plurality of electromagnetic valves 6 and the like).

  The hydraulic brake device β is provided so that the brake operation force, that is, the depression operation force of the brake pedal BP is increased by the booster BS, and the brake hydraulic pressure corresponding to the force is applied to the front wheel cylinders 5a and 5b. ing. On the other hand, a brake hydraulic pressure (control hydraulic pressure) corresponding to a control command from the brake control unit BCU is formed by the hydraulic pressure control device HU, and this control hydraulic pressure is provided so as to be applied to the wheel cylinders 5a to 5d of each wheel. As a result, ABS control and automatic brake control can be executed.

  Here, the ABS control means that when it is detected that the wheel has become locked during the braking operation by the driver, the wheel cylinder pressure is reduced or reduced in order to generate the maximum braking force for the wheel while preventing the lock. This control repeats holding and increasing pressure. The automatic brake control also includes vehicle motion control (hereinafter referred to as VDC control) that controls the wheel cylinder pressure of a predetermined wheel to stabilize the vehicle posture when it detects that over-steering or over-understeering occurs when the vehicle is turning. , Inter-vehicle distance control, collision avoidance control, etc. The automatic brake control also includes brake assist control (hereinafter referred to as BA control) in which the wheel cylinder generates a pressure higher than the pressure actually generated in the master cylinder when the driver performs an emergency brake operation.

  FIG. 2 shows a hydraulic circuit configuration of the hydraulic brake device β. The hydraulic brake device β includes a brake pedal BP, a booster BS, a reservoir RES, a master cylinder MC, a hydraulic pressure control device HU, and a wheel cylinder 5.

  Hereinafter, the configurations provided corresponding to each of the four wheels FL, FR, RL, and RR are distinguished by adding symbols a, b, c, and d, where a is the front left wheel FL, b. Is a front right wheel FR, c is a rear left wheel RL, and d is a rear right wheel RR.

  The hydraulic circuit of the hydraulic brake device β is divided into two independent systems, and has a first brake circuit 1 and a second brake circuit 2. The first brake circuit 1 is a normal brake circuit that connects the master cylinder MC and the wheel cylinders 5a and 5b on the front wheel side via the shut-off valve 6. The second brake circuit 2 is a control brake circuit that connects the pump P and the front and rear wheel cylinders 5 a to 5 d via the pressure increase control valve 7. A return circuit that connects the wheel cylinders 5a to 5d and the reservoir RES via the pressure reducing control valves 8a to 8d is provided with a part of the oil passage shared with the second brake circuit 2.

  The brake pedal BP is actuated by the driver's depression force and transmits the driver's brake operation to the booster BS. The brake pedal BP is provided with a stroke sensor 11. The stroke sensor 11 detects the stroke of the brake pedal BP and inputs the detected value to the brake control unit BCU.

  The booster BS amplifies the force transmitted from the brake pedal BP by, for example, engine negative pressure, and transmits the amplified force to the master cylinder MC (piston) to operate the master cylinder MC. Assist the pedaling force. The booster BS is not limited to the negative pressure booster.

  The reservoir RES is a reservoir tank that stores brake fluid, and is connected to the master cylinder MC and the second brake circuit 2.

  The master cylinder MC generates a master cylinder pressure proportional to the force transmitted from the booster BS. The master cylinder MC is a tandem type, and two hydraulic chambers (pressurizing chambers) are separated in the cylinder by two master cylinder pistons arranged in front and rear. The two hydraulic chambers are separately supplied with brake fluid from the reservoir RES. One hydraulic chamber is connected to the first brake circuit 1 </ b> A, that is, the system on the front left wheel FL side of the first brake circuit 1. The other hydraulic pressure chamber is connected to the first brake circuit 1B, that is, the system on the front right wheel FR side of the first brake circuit 1.

  The master cylinder MC has two back pressure chambers separated by two master cylinder pistons. Each of these back pressure chambers communicates with the reservoir RES.

  When the brake pedal BP is depressed, the two master cylinder pistons stroke to generate the same master cylinder pressure in the two hydraulic chambers. The master cylinder pressure is supplied to the first brake circuits 1A and 1B, respectively.

  A well-known cup-shaped seal member is provided on the outer circumference of each master cylinder piston, and during the piston stroke, the communication between each hydraulic chamber and the reservoir RES is blocked by this seal member, so that each liquid Pressurization in the pressure chamber is possible. At this time, the brake fluid is not supplied from the reservoir RES to the first brake circuits 1A and 1B, and the brake fluid is supplied to the first brake circuits 1A and 1B only from the hydraulic chamber of the master cylinder MC.

  On the other hand, when the brake pedal BP is returned, each master cylinder piston is returned by the force of the return spring. At this time, due to the structure of the seal member, the hydraulic chamber of the master cylinder MC communicates with the reservoir RES. As a result, the brake fluid in the reservoir RES can be supplied again to the hydraulic chamber (pressurizing chamber) of the master cylinder MC.

  If the reservoir RES side is the upstream side and the wheel cylinder 5 side is the downstream side, the wheel cylinders 5a and 5b are connected to the downstream ends of the first brake circuits 1A and 1B, respectively. Further, shutoff valves 6a and 6b are provided on the first brake circuits 1A and 1B, respectively. That is, the first brake circuit 1A connected to the master cylinder MC is connected to the wheel cylinder 5a of the front left wheel FL via the shut-off valve 6a. The first brake circuit 1B connected to the master cylinder MC is connected to the wheel cylinder 5b of the front right wheel FR via the shutoff valve 6b.

  A master cylinder pressure sensor 12 is provided in the first brake circuit 1B on the upstream side of the shutoff valve 6b. The master cylinder pressure sensor 12 detects the master cylinder pressure and inputs the detected value to the brake control unit BCU.

  The shut-off valve 6 is a normally open electromagnetic valve (= open when not energized and closed when energized), and is a so-called proportional valve in which the valve opening varies in proportion to the value of the current flowing through the coil. The shut-off valves 6a and 6b perform an opening / closing operation by a command current from the brake control unit BCU, and communicate / shut off the first brake circuits 1A and 1B, respectively. When the master cylinder pressure is higher than the pressure of the wheel cylinders 5a and 5b (wheel cylinder pressure), the master cylinder pressure is supplied to the wheel cylinders 5a and 5b by opening the valve, and the supply is shut off by closing the valve. On the other hand, when the wheel cylinder pressure is higher than the master cylinder pressure, the wheel cylinder pressure is supplied to the master cylinder MC by opening the valve, and the supply is shut off by closing the valve.

  A pump P is connected to the downstream side of the second brake circuit 2 connected to the reservoir RES. The pump P supplies the brake fluid sucked from the reservoir RES to the downstream side (pressure increase control valves 7a to 7d) at a high pressure. The motor M1 is an electric type, and the rotation speed is controlled by a command current from the brake control unit BCU to drive the pump P. The pump P may be driven using a driving force source other than the motor M1.

  The second brake circuit 2 on the downstream side of the pump P is provided with a check valve 9 that prevents the flow of brake fluid from the downstream side to the upstream side.

  The second brake circuit 2 branches downstream of the check valve 9 into a second brake circuit 2A that is a system on the front wheel side and a second brake circuit 2B that is a system on the rear wheel side. The downstream side of the second brake circuit 2A is branched into oil passages 2a and 2b. Similarly, the downstream side of the second brake circuit 2B is branched into oil passages 2c and 2d. The oil passages 2a and 2b are respectively connected to the first brake circuits 1A and 1B on the downstream side of the shutoff valves 6a and 6b, and are connected to the wheel cylinders 5a and 5b on the front wheel side via the first brake circuits 1A and 1B. Has been. Similarly, the oil passages 2c and 2d are respectively connected to the wheel cylinders 5c and 5d on the rear wheel side.

  Thus, the first brake circuit 1 is not connected to the wheel cylinders 5c, 5d of the rear wheels RL, RR, and only the second brake circuit 2 is connected. Therefore, the first and second brake circuits 1 and 2 can be selected only on the front wheel side, and on the rear wheel side, the wheel cylinder pressure is always increased only by the second brake circuit 2 (pump pressure). .

  Pressure increase control valves 7a to 7d are provided on the oil passages 2a to 2d, respectively. The pressure-increasing control valves 7a to 7d are normally closed (= closed when not energized, opened when energized) proportional solenoid valves, which are opened and closed by a command current from the brake control unit BCU and communicate with the oil passages 2a to 2d, respectively. ·Cut off. The pump pressure is supplied to the wheel cylinders 5a to 5d by opening the valve, and the supply is shut off by closing the valve.

  One ends of oil passages 3a to 3d are connected to the oil passages 2a to 2d on the downstream side of the pressure increase control valves 7a to 7d, respectively. The other ends of the oil passages 3a to 3d are each connected to the second brake circuit 2 on the upstream side of the pump P, and are connected to the reservoir RES via the second brake circuit 2. Decompression control valves 8a to 8d are provided on the oil passages 3a to 3d, respectively. “Wheel cylinders 5a to 5d (→ oil passages 2a to 2d → oil passages 3a to 3d) → pressure reduction control valves 8a to 8d (→ oil passages 3a to 3d → second brake circuit 2) → reservoir RES” A return circuit for returning from the wheel cylinder 5 to the reservoir RES is formed.

  The pressure reduction control valves 8a and 8b provided in the oil passages 3a and 3b on the front wheel side are normally closed proportional solenoid valves, and the pressure reduction control valves 8c and 8d provided in the oil passages 3c and 3d on the rear wheel side are normally open. This is a proportional solenoid valve. The pressure-reducing control valves 8a to 8d are opened and closed by a command current from the brake control unit BCU, and communicate and block the oil passages 3a to 3d, respectively. By opening the valve, the brake fluid is returned from the wheel cylinders 5a to 5d to the reservoir RES, and the wheel cylinder pressure is released and reduced. In the valve closed state, the above-mentioned decompression / decompression is not performed.

  A relief oil passage 2 e is connected to the second brake circuit 2 between the pump P and the check valve 9. The oil passage 2e is connected to the oil passages 3a to 3d (any one) upstream of the pressure reduction control valves 8a to 8d, and is connected to the reservoir RES via the oil passages 3a to 3d and the second brake circuit 2. ing. The oil passage 2e may be directly connected to the second brake circuit 2 on the upstream side of the pump P. A relief valve 10 is provided on the oil passage 2e. The relief valve 10 opens when the pump pressure exceeds a predetermined value (for example, a predetermined pressure resistance of the hydraulic circuit), and connects the discharge side of the pump P to the reservoir RES. As a result, the pump pressure is released to the reservoir RES, and the pump pressure is prevented from exceeding the predetermined value.

  A wheel for detecting the pressure of each of the wheel cylinders 5b to 5d (wheel cylinder pressure = brake hydraulic pressure) on the downstream side of the pressure increasing control valve 7 and the pressure reducing control valve 8 corresponding to each wheel FR, FL, RR, RL. Cylinder pressure sensors 13a to 13d are provided. The detected value is input to the brake control unit BCU. Each wheel FR, FL, RR, RL is provided with wheel speed sensors 14a to 14d (see FIG. 1), and each detected wheel speed is input to the brake control unit BCU.

  When a brake failure occurs in either front wheel FL or FR, this is detected by the wheel cylinder pressure sensors 13a and 13b, and the failure is dealt with by a command from the brake control unit BCU. The shut-off valves 6a and 6b are shut off.

(Shutoff valve)
Hereinafter, the configuration of the shutoff valve 6 will be described. FIG. 3 is an axial cross-sectional view of the shutoff valves 6a and 6b. For the sake of explanation, the x-axis is provided in the axial direction of the valve, and the armature 67 side with respect to the plunger 64 is defined as the positive direction. The shutoff valve 6 includes a housing 61, a first port 62, a valve seat 63, a plunger 64, a second port 65, a return spring 66, an armature 67, and a coil (solenoid) 68.

  A coil 68 is provided on the outer periphery of the housing 61 on the x-axis positive direction side. Inside the housing 61, a first cylinder chamber 61a having a large diameter is formed on the x-axis positive direction side, and a second cylinder chamber 61b having a small diameter is formed on the x-axis negative direction side.

  A first port 62 is formed in the housing 61 on the x-axis negative direction side with respect to the second cylinder chamber 61b so as to penetrate in the x-axis direction and open to the end surface on the x-axis negative direction side of the second cylinder chamber 61b. . The first port 62 is connected to the upstream side of the first brake circuits 1A and 1B, and is connected to the master cylinder MC via the first brake circuits 1A and 1B. That is, the first port 62 = master cylinder pressure port.

  A second port 65 is formed in the housing 61 so as to penetrate in the radial direction of the valve, and is open to the inner peripheral surface of the second cylinder chamber 61b. The second port 65 is connected to the downstream side of the first brake circuits 1A, 1B, and is connected to the wheel cylinders 5a, 5b of the front wheels FL, FR via the first brake circuits 1A, 1B. That is, the second port 65 = the wheel cylinder pressure port.

  An armature 67 is accommodated in the first cylinder chamber 61a so as to be slidable in the x-axis direction. A plunger 64 is accommodated in the second cylinder chamber 61b so as to be slidable in the x-axis direction. A return spring 66 is installed in a compressed state in the x-axis direction between the stepped portion 64B of the plunger 64 and the end surface on the x-axis negative direction side of the second cylinder chamber 61b. The plunger 64 is pressed toward the x-axis positive direction side by the spring force of the return spring 66. With this pressing force, the end surface of the plunger 64 on the x-axis positive direction side is in contact with the end surface of the armature 67 on the x-axis negative direction side.

  A valve seat (valve seat) 63 is provided at the opening of the first port 62 to the second cylinder chamber 61b. The tip 64A of the plunger 64 on the x axis negative direction side faces the valve seat 63 in the x axis direction. When the plunger 64 moves in the negative x-axis direction, the tip end portion 64A comes into contact with and closely contacts the valve seat 63 (that is, the plunger 64 serving as the valve element is seated on the valve seat 63 serving as the valve seat). 63 is closed. Thereby, the communication between the first port 62 and the second cylinder chamber 61b is blocked. The second port 65 and the second cylinder chamber 61b are always in communication.

  Next, the operation of the shutoff valve 6 will be described. The plunger 64 and the armature 67 are slid in the x-axis direction in the housing 61 and displaced by the action of the following electromagnetic force and oil pressure in addition to the spring force. Due to the displacement, the distance Xv between the tip 64A of the plunger 64 and the valve seat 63 changes. The distance Xv corresponds to a so-called valve opening.

  When Xv is larger than zero and the distal end portion 64A is away from the valve seat 63, the first port 62 and the second cylinder chamber 61b communicate with each other. As a result, the brake fluid can flow between the first port 62 (master cylinder MC) and the second port 65 (wheel cylinders 5a, 5b), and the shutoff valves 6a, 6b are opened. In this valve open state, the first brake circuits 1A and 1B communicate with each other, and the master cylinder MC communicates with the wheel cylinders 5a and 5b. When Xv reaches the maximum value, the shutoff valves 6a and 6b are fully opened.

  When Xv is zero and the tip 64A and the valve seat 63 are in contact with each other, the brake fluid cannot flow between the first port 62 and the second port 65, and the shutoff valves 6a and 6b are closed. It becomes a valve state. In this closed state, the first brake circuits 1A and 1B are shut off, and the communication between the master cylinder MC and the wheel cylinders 5a and 5b is shut off.

  Therefore, the spring force acting on the plunger 64 in the positive x-axis direction acts in a direction to open the shutoff valves 6a and 6b and to communicate the first brake circuits 1A and 1B.

  The coil 68 generates electromagnetic force when supplied with a control current from the brake control unit BCU. This electromagnetic force changes in accordance with the current value I, and increases as the current value I increases, and acts on the armature 67 (and the plunger 64) on the x-axis negative direction side. Attract to. That is, the shutoff valves 6a and 6b are closed to act in the direction of shutting off the first brake circuits 1A and 1B.

  The plunger 64 has a hydraulic force, that is, a differential pressure Δp between the master cylinder pressure and the wheel cylinder pressure (= master cylinder pressure−wheel cylinder pressure), and a sectional area of the plunger 64 (pressure receiving area in the direction perpendicular to the axis). The force multiplied by S acts. When the master cylinder pressure> the wheel cylinder pressure, the differential pressure Δp> 0, and the oil pressure acts in the positive direction of the x axis, that is, in the direction in which the shut-off valves 6a and 6b are opened and the first brake circuits 1A and 1B are communicated. To do. On the contrary, when the master cylinder pressure <the wheel cylinder pressure, the differential pressure Δp <0, and the hydraulic pressure closes the first brake circuit 1A, 1B by closing the shut-off valves 6a, 6b on the x-axis negative direction side. Acts on direction.

  The displacement amount of the plunger 64, that is, the distance Xv (valve opening) is determined by the balance of the above spring force, electromagnetic force, and oil pressure. For example, the shutoff valve 6 is closed when “the force in the x-axis positive direction due to {spring force + oil pressure} <the force in the negative x-axis direction due to electromagnetic force”.

  FIG. 4 is a graph showing the relationship between the current value I of the coil 68 and the valve opening pressure in the shutoff valves 6a and 6b. Here, the valve opening pressure corresponds to the differential pressure Δp (= master cylinder pressure−wheel cylinder pressure) and indicates the oil pressure that opens the shutoff valve 6 (acting in the positive direction of the x-axis). As the current value I increases, the electromagnetic force (acting in the negative x-axis direction) increases, and the valve opening pressure (acting in the positive x-axis direction) of the shut-off valve 6 also increases in proportion thereto. In other words, the electromagnetic force (in the negative x-axis direction) required to close the cutoff valve 6 increases in proportion to the increase in the valve opening pressure (acting in the positive x-axis direction) of the cutoff valve 6. The current value I increases.

  The pressure-increasing control valve 7 and the pressure-reducing control valve 8 have the same configuration as that of the shutoff valve 6 except that it is normally closed or normally opened.

(Control system configuration)
As shown in FIG. 1, the plurality of control units CU include a hybrid control unit HCU, a brake control unit BCU, and an engine control unit ECU, and these control units can exchange information. They are connected to each other via a communication line. Further, the battery B is provided with a battery control unit BatCU. The battery control unit BatCU detects the charging state (battery SOC) of the battery B, the charging current, and the like and outputs them to the hybrid control unit HCU.

  The engine control unit ECU controls the operation of the engine ENG. Specifically, based on information such as the engine speed Ne detected by the engine speed sensor and the target engine torque Te * input from the hybrid control unit HCU, a command for controlling the engine operating point (Ne, Te) For example, it outputs to the throttle valve actuator.

(Hybrid control unit)
The hybrid control unit HCU mainly has the function of managing the energy consumption of the entire vehicle and running the vehicle with the highest efficiency. The hybrid control unit HCU calculates a target driving force based on the accelerator opening input from the accelerator opening sensor and the vehicle speed input from the vehicle speed sensor. Further, the motor M is provided with a rotation speed sensor for detecting the motor rotation speed, and the detected value is input to the hybrid control unit HCU.

  The hybrid control unit HCU calculates target values for the motor rotational speed Nm and the motor torque Tm based on the target driving force and the like. Based on the calculated target motor rotation speed Tm * and the like, a command for controlling the operating point (Nm, Tm) of the motor M is output to the inverter I, and the operation of the motor M is controlled. Further, the engine torque target value Te * is calculated based on the target driving force and the like, and this is output to the engine control unit ECU to control the operation of the engine ENG.

  Further, the hybrid control unit HCU calculates a target charge / discharge power based on the battery SOC using a predetermined target charge / discharge amount map.

  Further, the hybrid control unit HCU calculates a command value for the regenerative braking force on the rear wheel side in consideration of the battery charge state (battery SOC) input from the battery control unit BatCU and the vehicle speed. The motor M (regenerative braking device γ) is controlled via the inverter I so as to generate a regenerative braking force corresponding to the regenerative braking force command value (target regenerative braking force). If the vehicle speed is low and only a small regenerative braking force can be obtained, or if the amount of charge (battery SOC) is nearly full and the power generated by regeneration cannot be charged to battery B, it is determined that regenerative braking is impossible. Therefore, regenerative braking is not performed. Further, the hybrid control unit HCU outputs the calculated regenerative braking force command value and a signal determined to be incapable of regenerative braking to the brake control unit BCU.

(Brake control unit)
The brake control unit BCU has various information regarding the detected values inputted from the stroke sensor 11, the master cylinder pressure sensor 12, the wheel cylinder pressure sensors 13a to 13d, the wheel speed sensors 14a to 14d, and the running state inputted from the vehicle side. The information processing is performed according to the built-in program. In addition, a control command is output to each actuator of the hydraulic pressure control device HU according to the processing result, and the hydraulic braking force of each wheel is controlled by controlling the shutoff valve 6, the pressure increase control valve 7, the pressure reduction control valve 8, and the motor M1. (Foil cylinder pressure) is controlled.

  The brake control unit BCU calculates the driver's required braking force based on the driver's brake operation state. The brake operation state of the driver is detected by a stroke sensor 11 provided on the brake pedal BP. It may be detected by the master cylinder pressure sensor 12 or a brake switch. During normal braking without ABS control, the braking force of the entire vehicle is determined according to the driver's required braking force.

(When regenerative cooperative control is not performed)
FIG. 5 shows the braking force distribution of the front and rear wheels when the regenerative cooperative control is not performed during normal braking. On the front wheel side, a hydraulic braking force is generated by directly supplying a master cylinder pressure corresponding to the pedal stroke (stroke Sp) to the wheel cylinders 5a and 5b. On the other hand, on the rear wheel side, a hydraulic braking force having a magnitude obtained by subtracting the hydraulic braking force on the front wheel side from the braking force of the entire vehicle is generated by the hydraulic pressure (wheel cylinder pressure) controlled by the flowchart shown in FIG. Specifically, the brake control unit BCU sets a target value for the wheel cylinder pressure on the rear wheel side based on a characteristic map as shown in FIG. 6, and controls the wheel cylinder pressure based on this target value.

  FIG. 6 shows the relationship between the wheel cylinder pressure (target value) on the rear wheel side and the master cylinder pressure. The wheel cylinder pressure of the rear wheel is a value substantially proportional to the hydraulic braking force on the rear wheel side. The master cylinder pressure is a value substantially proportional to the hydraulic braking force on the front wheel side. In the region where the master cylinder pressure is from 0 to a predetermined value Pmc1, the inclination a1 of the rear wheel wheel cylinder pressure with respect to the master cylinder pressure is 1, and the rear wheel wheel cylinder pressure is equal to the master cylinder pressure. On the other hand, in the region where the master cylinder pressure is Pmc1 or more, the slope a2 of the rear wheel wheel cylinder pressure with respect to the master cylinder pressure is set to about 0.4, for example, and the increment of the rear wheel wheel cylinder pressure is smaller than the increment of the master cylinder pressure. It has become. The predetermined value Pmc is set to a value of about 3 to 5 MPa, for example.

(When performing regenerative cooperative control)
The brake control unit BCU controls the hydraulic brake device β in cooperation with the regenerative brake device γ so as to maintain the braking force of the entire vehicle when the brake pedal BP is depressed to brake. For example, when the regenerative braking force is insufficient with respect to the driver's required braking force, a control signal is output to the hydraulic pressure control device HU to generate the hydraulic braking force that compensates for the shortage.

  FIG. 7 shows the braking force distribution of the front and rear wheels when performing regenerative cooperative control during normal braking. As will be described later, on the front wheel side to which no regenerative braking force is applied, a target value of the wheel cylinder pressure is set according to the characteristic map shown in FIG. 8, and a hydraulic braking force is generated by controlling the wheel cylinder pressure based on this target value. To do. On the other hand, a predetermined regenerative braking force is generated on the rear wheel side, and the hydraulic cylinder braking force controlled by the flowchart shown in FIG. 15 and the hydraulic braking force on the front wheel side and the regenerative braking on the rear wheel side are controlled from the braking force of the entire vehicle. Generates hydraulic braking force with the power subtracted. Thereby, the braking force of the whole vehicle equivalent to the case where regenerative cooperative control is not performed (FIG. 5) is generated. Hereinafter, these hydraulic pressure controls will be specifically described.

  For the rear wheels RL and RR (drive wheels) to which regenerative braking force is applied, the brake control unit BCU determines the rear wheel side regenerative braking force command value and the front wheel side (wheel cylinder pressure target value) from the braking force of the entire vehicle. The hydraulic braking force target value on the rear wheel side is calculated by subtracting the hydraulic braking force target value (calculated from (1)). And the wheel cylinder pressure target value of each rear wheel RL and RR is calculated by converting the calculated hydraulic braking force into the hydraulic pressure. The brake control unit BCU controls the wheel cylinder pressures of the rear wheels RL and RR based on the wheel cylinder pressure target value calculated in this way.

  For the front wheels FL, FR (driven wheels), the target value of the wheel cylinder pressure (generated by the master cylinder pressure) is set lower than when the regenerative cooperative control is not performed. Based on the wheel cylinder pressure target value set in this way, the wheel cylinder pressure of each front wheel FL, FR is controlled. The decrease in the hydraulic braking force on the front wheel side is compensated by increasing the regenerative braking force command value on the rear wheel side to maintain the braking force of the entire vehicle. That is, as shown in FIG. 7, the rear wheel side regenerative braking force is increased by the above-described decrease in the front wheel side hydraulic braking force while the magnitude of the rear wheel hydraulic pressure braking force remains substantially unchanged.

(Relationship between stroke and pressure)
FIG. 8 shows the relationship between the stroke Sp of the brake pedal BP and the pressure (master cylinder pressure, front wheel side wheel cylinder pressure) in the first embodiment. These relationships are stored as characteristic maps in the brake control unit BCU, and are referred to when calculating the master cylinder pressure target value and the front wheel side wheel cylinder pressure target value.

  A slow braking stroke range (0 ≦ Sp ≦ Spo) equal to or less than a predetermined stroke Spo is determined in advance as a stroke range during slow braking in which the driver does not require a high braking force. Further, a sudden braking stroke region (Sp> Spo) larger than the predetermined stroke Spo is determined in advance as a stroke region during sudden braking that requires a high braking force by the driver. Spo is set to a value of 30 to 40 mm or less so that the braking G in the stroke range (0 ≦ Sp ≦ Spo) is, for example, 0.3 G or less.

  The target value of the wheel cylinder pressure (hydraulic braking force) is set according to the stroke Sp of the brake pedal BP. A slow braking stroke region (0 ≦ Sp ≦ Spo) is set in the pressure reduction control region of the front wheels FL and FR, and in this region, the wheel cylinder pressure target value = 0. The sudden braking stroke region (Sp> Spo) is set as the pressure increase control region of the front wheels FL, FR. In this region, the wheel cylinder pressure target value starts to gradually increase from 0 as the stroke Sp increases from Spo. Further, the increasing gradient of the wheel cylinder pressure target value also gradually increases. When the stroke Sp exceeds a predetermined value, the increasing gradient becomes constant, and the wheel cylinder pressure target value increases in proportion to the stroke Sp.

  Further, the master cylinder pressure target value for the stroke Sp is set so that an ideal brake pedal reaction force can be obtained when the driver depresses the brake pedal BP. In the front wheel pressure reduction control region, the master cylinder pressure target value is the minimum value Pmo when the stroke Sp is 0, and gradually increases as the stroke Sp increases from 0, and the increasing gradient also increases gradually. When the stroke Sp becomes greater than or equal to a predetermined value (<Spo), the increasing gradient becomes constant, and the master cylinder pressure target value increases in proportion to the stroke Sp. The master cylinder pressure target value when the stroke Sp is Spo is set to Pm1. On the other hand, in the front wheel pressure increase control region, the master cylinder pressure target value continues to increase in proportion to the stroke Sp (with substantially the same increase gradient as the wheel cylinder pressure target value).

  Further, the differential pressure Δp (= master cylinder pressure−wheel cylinder pressure) corresponds to the valve opening pressure of the shutoff valve 6 (acting in the positive x-axis direction). In the front wheel pressure reduction control region, since the wheel cylinder pressure is controlled to 0, the differential pressure Δp = master cylinder pressure. Therefore, the valve opening pressure of the shutoff valve 6 gradually increases from the value Pmo as the stroke Sp increases from 0, and becomes the value Pm1 at the stroke Spo.

(When performing automatic brake control, etc.)
The brake control unit BCU is provided so as to be able to execute automatic brake control. For example, in VDC control, the braking force required for controlling the vehicle yaw moment based on a signal indicating the vehicle behavior input from the vehicle behavior sensor provided on the vehicle side (this is called the required braking force 1) is set for each wheel. Calculate every time. Then, the VDC braking force is calculated by adding the driver's required braking force and the required braking force 1 for each wheel. In the BA control, an assist request braking force is calculated based on an input from other logic such as collision avoidance control, and the BA braking force is calculated by adding this to the driver's required braking force.

  Then, a wheel cylinder pressure target value (such as a VDC command pressure) in each wheel is calculated from these VDC braking force and BA braking force. Automatic brake control is executed by controlling the wheel cylinder pressure based on the calculated wheel cylinder pressure target value and the detection value input from the wheel cylinder pressure sensor 13.

  The brake control unit BCU is provided so as to be able to execute ABS control. In ABS control, the road surface μ is estimated based on the detected value of the wheel cylinder pressure. Based on a predetermined tire model, the wheel cylinder pressure that can obtain the maximum braking force while preventing the wheel from being locked is set as a target value. Calculate. The wheel cylinder increasing / decreasing amount that realizes the optimum slip ratio is calculated based on the wheel speed and wheel acceleration of each wheel detected by the wheel speed sensor 14 and the pseudo vehicle body speed estimated based on each wheel speed. The method may be adopted. Note that ABS control is executed with priority over automatic brake control.

  Also, regenerative cooperative control is not performed during execution of automatic brake control or ABS control.

  Next, a flow of hydraulic pressure control in regenerative cooperative control executed by the brake control unit BCU will be described. First, front wheel side control will be described based on FIGS. 9 to 14, and then rear wheel side control will be described based on FIG.

(Front wheel master cylinder pressure: control of shut-off valve)
FIG. 9 shows a control flowchart of the shutoff valve 6 provided in the first brake circuit 1 on the front wheel side.

  In step S11, based on the brake operation state of the driver and a signal sent from the vehicle side, it is determined whether or not to start the control on the front wheel side. FIG. 10 shows the specific contents of S11.

  First, in S41, the brake operation state of the driver is detected. When it is detected that the brake pedal BP is depressed by the driver, the process proceeds to S42. If the depression of the brake pedal BP is not detected, the process proceeds to S44 and it is determined that the front wheel side control is not started.

  In S42, based on the signal from the hybrid control unit HCU, it is determined whether or not regenerative braking can be executed. If regenerative braking is possible, the process proceeds to S43 and it is determined that the front wheel side control is started. If regenerative braking is not possible, the process proceeds to S44 and it is determined that the front wheel side control is not started.

  If it is determined in S11 (S43) that the front wheel side control is started, the process proceeds to S12. On the other hand, if it is determined in S11 (S44) that the front wheel side control is unnecessary, the process proceeds to S18 and the shutoff valve control is not performed. That is, the shutoff valves 6a and 6b are kept fully open with the current value I = 0. As a result, the master cylinder pressure corresponding to the stroke Sp is directly supplied to the wheel cylinders 5a and 5b, thereby generating a hydraulic braking force on the front wheel side.

  In S12, the valve opening pressures of the shutoff valves 6a and 6b are set to the initial value Pm0. That is, according to the graph of FIG. 4, the current value I that realizes the valve opening pressure Pm0 is passed through the coils 68 of the shutoff valves 6a and 6b. Thereafter, the process proceeds to S13.

In S13, the detection value of the stroke Sp is received from the stroke sensor 11, and the process proceeds to S14.
In S14, the detected value of the front wheel cylinder pressure is received from the wheel cylinder pressure sensors 13a and 13b, and the process proceeds to S15.

  In S15, based on the detected stroke Sp, the master cylinder pressure target value is calculated using the characteristic map of FIG. 8, and the process proceeds to S16.

  In S16, the valve opening pressure of the shutoff valves 6a and 6b is set to (master cylinder pressure target value−wheel cylinder pressure detection value). That is, according to the graph of FIG. 4, a current value I that realizes the valve opening pressure = (master cylinder pressure target value−wheel cylinder pressure detection value) is passed through the coils 68 of the shutoff valves 6a and 6b. Thereafter, the process proceeds to S17.

  In S17, based on the brake operation state of the driver and a signal sent from the vehicle side, it is determined whether or not to end the control on the front wheel side. FIG. 11 shows the specific contents of S17.

  First, in S51, the magnitude of deceleration (braking force) requested by the driver is determined. If the requested deceleration is less than the predetermined value, the process proceeds to S52. If the requested deceleration is equal to or greater than the predetermined value, the process proceeds to S54 and it is determined that the front wheel side control is to be terminated. The driver's required deceleration is detected based on the detection value of the stroke sensor 11 or the master cylinder pressure sensor 12. The predetermined value is set to a deceleration (for example, 0.4 G or more) at which the vehicle deceleration increases and the stability of the vehicle behavior starts to decrease.

  S52 to S54 are the same as S42 to S44. If it is determined in S52 that regenerative braking is possible, the process proceeds to S53 and it is determined not to end the control on the front wheel side. If it is determined that the regenerative braking is not possible, the process proceeds to S54 and it is determined that the control on the front wheel side is terminated.

  When it is determined in S17 (S54) that the front wheel side control is to be terminated, the process proceeds to S100 to execute a termination process. If it is determined in S17 (S53) that the front wheel side control is not terminated, the process returns to S13. That is, the processes from S13 to S17 are repeated until it is determined that the front wheel side control is finished.

  By repeating the processes from S13 to S17 in this way, the actual master cylinder pressure is controlled so as to coincide with the master cylinder pressure target value corresponding to the stroke Sp in the characteristic map of FIG. Thus, an ideal brake pedal reaction force can be obtained according to the stroke Sp of the brake pedal BP operated by the driver.

(Front wheel cylinder pressure: Control of pressure reducing control valve)
FIG. 12 shows a control flowchart of the pressure reduction control valves 8a and 8b provided in the return circuit on the front wheel side.

  In step S21, as in S11, it is determined whether or not to start front wheel side control. When starting control, the process proceeds to S22. When the front wheel side control is unnecessary, the process proceeds to S26 and the pressure reduction control valves 8a and 8b are not controlled. That is, the current value = 0 and the decompression control valves 8a and 8b are kept in the fully closed state. In S26, the pressure increase control valves 7a and 7b are not controlled, and the pressure increase control valves 7a and 7b are kept in a fully closed state.

  In S22, the detection value of the stroke Sp is received from the stroke sensor 11, and the process proceeds to S23.

  In S23, it is determined whether or not the detected stroke Sp is in the slow braking stroke region (0 ≦ Sp ≦ Spo), that is, whether it is in the front wheel pressure reduction control region. When 0 ≦ Sp ≦ Spo, the process proceeds to S24, and when Sp> Spo, the process proceeds to S26.

  In S24, the pressure increase control valves 7a and 7b are kept in a fully closed state, while the pressure reduction control valves 8a and 8b are opened. Thereafter, the process proceeds to S25.

  In S25, similarly to S17, it is determined whether or not to end the control on the front wheel side. When the process ends, the process proceeds to S100, and the end process is executed. If not, return to S22.

  Thus, while the stroke Sp is in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo), the wheel cylinder pressure of the front wheels FL and FR is reduced and the target value = 0 until the control end of the front wheel side is determined. (S22 to S25). This value (= 0) is detected by the wheel cylinder pressure sensors 13a and 13b, inputted to the brake control unit BCU, and used for the control logic (S16) of the shutoff valves 6a and 6b.

  On the other hand, while the stroke Sp is in the front wheel pressure increase control region (Sp> Spo), the pressure increase control valves 7a and 7b and the pressure reduction control valves 8a and 8b are kept closed (S23 → S26) to control the front wheels. Until the end is determined, the valve opening pressure of the shutoff valves 6a and 6b is controlled in this state (S13 to S16). As a result, the master cylinder pressure is controlled to coincide with the target value, and the front wheel cylinder pressure is also increased from 0 and controlled to the target value (characteristic map in FIG. 8) corresponding to the stroke Sp.

(Front wheel end processing)
FIG. 13 is a flowchart showing a flow of a front wheel control end process. In the end process, the front wheel cylinder pressure is controlled.

  In step S101, a master cylinder pressure detection value (when the front wheel control is finished) is input from the master cylinder pressure sensor 12, and the process proceeds to S102.

  In S102, the wheel cylinder pressure target value for the front wheels is set to the detected value of the master cylinder pressure, and the process proceeds to S103.

  In S103, it is determined whether or not to increase the front wheel cylinder pressure based on the detection values of the wheel cylinder pressure sensors 13a and 13b and the wheel cylinder pressure target value. When the pressure is increased, the process proceeds to S104, and when the pressure is not increased, the process proceeds to S109.

  In S104, the front wheel side pressure increase control valves 7a and 7b are opened, and the second brake circuit 2 (oil passages 2a and 2b) is brought into communication. Further, the pressure reduction control valves 8a and 8b on the front wheel side are closed, and the pump M is driven by controlling the motor M1. The motor rotation speed (pump discharge amount) is maintained at the maximum value that can reliably obtain the wheel cylinder pressure target values for the front and rear wheels (hereinafter the same). As a result, the pump pressure is supplied to the wheel cylinders 5a and 5b via the second brake circuit 2, and the front wheel wheel cylinder pressure is increased. Thereafter, the process proceeds to S105.

  In S105, it is determined whether or not the wheel cylinder pressure has reached the target value based on the detection values of the wheel cylinder pressure sensors 13a and 13b. When the target value is reached, the process proceeds to S106. If not reached, the process returns to S104, and the wheel cylinders 5a and 5b are continuously pressurized.

  In S106, the pressure increase control valves 7a and 7b are closed, and the second brake circuit 2 (oil paths 2a and 2b) is shut off. Further, the motor M1 is turned off, the driving of the pump P is stopped, and the increase of the wheel cylinder pressure by the pump pressure is finished. Thereafter, the process proceeds to S107.

  In S107, it is determined that the front wheel cylinder pressure control is finished. That is, when the detected value of the wheel cylinder pressure does not coincide with the detected value of the master cylinder pressure, the process returns to S103 and the control of the wheel cylinder pressure is continued. If the detected value of the wheel cylinder pressure matches the detected value of the master cylinder pressure, the process proceeds to S108.

  In S108, the shutoff valves 6a and 6b are fully opened. Further, the pressure increase control valves 7a and 7b and the pressure reduction control valves 8a and 8b are fully closed, and the motor M1 is turned off. That is, these valves 6, 7, and 8 are returned to the initial state, and the wheel cylinder pressure control is finished.

  In S109, it is determined whether to reduce the front wheel cylinder pressure based on the target value and the detected value of the wheel cylinder pressure. When the pressure is reduced, the process proceeds to S110, and when the pressure is not reduced, the process proceeds to S113.

  In S110, the pressure increase control valves 7a and 7b are closed, and the second brake circuit 2 (oil paths 2a and 2b) is shut off. Further, the decompression control valves 8a and 8b are opened, the reservoir RES and the wheel cylinders 5a and 5b are communicated, and the wheel cylinder pressure is extracted into the reservoir RES and decompressed. Thereafter, the process proceeds to S111.

  In S111, it is determined whether or not the wheel cylinder pressure has reached a target value. When the target value is reached, the process proceeds to S112. If not, the process returns to S110, and the wheel cylinders 5a and 5b are continuously depressurized.

  In S112, the pressure-reducing control valves 8a and 8b are closed and the reservoir RES and the wheel cylinders 5a and 5b are shut off to finish the wheel cylinder pressure reduction. Thereafter, the process proceeds to S107.

  In S113, the wheel cylinder pressure is neither increased nor reduced, that is, maintained. The pressure increase control valves 7a and 7b are closed to shut off the second brake circuit 2 (oil passages 2a and 2b), and the pressure reduction control valves 8a and 8b are closed. Therefore, the brake fluid in the front wheel wheel cylinders 5a, 5b is contained by the pressure increase control valve 7 and the pressure reduction control valve 8, and the wheel cylinder pressure is maintained. Thereafter, the process proceeds to S107.

  FIG. 14 shows a time chart of the master cylinder pressure and the front wheel wheel cylinder pressure when the above end processing is performed at the end of front wheel control.

  During front wheel control, the stroke Sp of the brake pedal BP is assumed to be in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo). During front wheel control, the master cylinder pressure is controlled to a predetermined value corresponding to the stroke Sp by controlling the valve opening pressure of the shutoff valve 6. Further, the wheel cylinder pressure is controlled to 0 by opening the pressure reducing control valves 8a and 8b.

  When the end of the front wheel control is determined and the end process (S100) is started, the target value of the front wheel wheel cylinder pressure is set to the master cylinder pressure (detected value), and the front wheel wheel cylinder pressure is set to this target value (= master cylinder). The pressure increase is controlled so as to coincide with (pressure) (S101 to S105). Note that the balance of the braking force of the entire vehicle is maintained by reducing the regenerative braking force on the rear wheel side in accordance with the increase in the hydraulic braking force on the front wheel side by this pressure increase control.

  When the front wheel wheel cylinder pressure matches the master cylinder pressure, it is determined that the control of the front wheel wheel cylinder pressure is finished (S107), and the shutoff valve 6 is fully opened (S108). Thereafter, as the brake pedal BP is returned, the hydraulic pressure chamber (pressurizing chamber) of the master cylinder MC communicates with the reservoir RES by the cup-shaped seal member, and the wheel cylinder pressure is reduced while keeping the master cylinder pressure. The

  Thus, in the termination process of the first embodiment, the shutoff valve 6 is opened after eliminating the differential pressure between the master cylinder pressure and the wheel cylinder pressure. Therefore, a sudden change in the stroke Sp of the brake pedal BP when the shutoff valve 6 is opened is suppressed, and a natural pedal operation feeling is realized.

(Rear wheel wheel cylinder pressure)
FIG. 15 shows a flowchart of wheel cylinder pressure control on the rear wheel side.

  In step S201, similarly to step S11 for determining control start on the front wheel side, it is determined whether or not to start wheel cylinder pressure control on the rear wheel side based on the brake operation state of the driver and a signal sent from the vehicle side. . If the control start on the rear wheel side is determined, the process proceeds to S202. If the control start is not determined, the process proceeds to S207.

  In S202, it is determined whether or not to increase the wheel cylinder pressure based on the separately calculated rear wheel wheel cylinder pressure target value and the detected values of the wheel cylinder pressure sensors 13c and 13d. If the pressure is increased, the process proceeds to S203, and if not, the process proceeds to S208.

  In S203, the pressure increase control valves 7c and 7d are opened, and the second brake circuit 2 (oil passages 2c and 2d) is communicated. Further, the pressure reduction control valves 8c and 8d are closed, and the pump M is driven by controlling the motor M1. As a result, the pump pressure is supplied to the wheel cylinders 5c and 5d via the pressure increase control valves 7c and 7d (second brake circuit 2), and the wheel cylinder pressure of the rear wheel is increased. Thereafter, the process proceeds to S204.

  In S204, it is determined whether or not the wheel cylinder pressure has reached the target value based on the detection values of the wheel cylinder pressure sensors 13c and 13d. When the target value is reached, the process proceeds to S205. If not, the process returns to S203, and the pressure increase of the wheel cylinders 5c and 5d is continued.

  In S205, the pressure increase control valves 7c and 7d are closed, and the second brake circuit 2 (oil paths 2c and 2d) is shut off. Further, the motor M1 is turned off, the driving of the pump P is stopped, and the increase of the rear wheel cylinder pressure by the pump pressure is finished. Thereafter, the process proceeds to S206.

  In S206, it is determined whether or not to end the wheel cylinder pressure control on the rear wheel side in the same manner as the control end determination step S17 on the front wheel side. When the control is continued, the process returns to S202, and when the control is terminated, the process proceeds to S207.

  In S207, the motor M1 is turned off, the pressure increase control valves 7c and 7d are closed, and the pressure reduction control valves 8c and 8d are opened. As a result, the rear wheel cylinder pressure is reduced to zero. That is, these valves 7 and 8 are returned to the initial state to end the wheel cylinder pressure control.

  In S208, it is determined whether or not to reduce the wheel cylinder pressure based on the separately calculated rear wheel wheel cylinder pressure target value and the detected value. If the pressure is reduced, the process proceeds to S209. If the pressure is not reduced, the process proceeds to S212.

  In S209, the pressure increase control valves 7c and 7d are closed, and the second brake circuit 2 (oil paths 2c and 2d) is shut off. Further, the decompression control valves 8c and 8d are opened, the reservoir RES and the wheel cylinders 5c and 5d are communicated, and the wheel cylinder pressure is reduced to the reservoir RES to reduce the pressure. Thereafter, the process proceeds to S210.

  In S210, it is determined whether or not the wheel cylinder pressure has reached the target value based on the detection values of the wheel cylinder pressure sensors 13c and 13d. When the target value is reached, the process proceeds to S211. If not, the process returns to S209, and the wheel cylinders 5c and 5d are continuously depressurized.

  In S211, the pressure reduction control valves 8c and 8d are closed, and the pressure reduction of the wheel cylinder pressure is finished by shutting off between the reservoir RES and the wheel cylinders 5c and 5d. Thereafter, the process proceeds to S206.

  In S212, the rear wheel wheel cylinder pressure is neither increased nor reduced, that is, maintained. The pressure increase control valves 7c and 7d are closed to shut off the second brake circuit 2 (oil passages 2c and 2d), and the pressure reduction control valves 8c and 8d are closed. Therefore, the brake fluid in the rear wheel cylinders 5c and 5d is contained by the pressure increase control valve 7 and the pressure reduction control valve 8, and the wheel cylinder pressure is maintained. Thereafter, the process proceeds to S206.

  The above control flow is basically the same not only for regenerative cooperative control but also for automatic brake control such as VDC control. In addition, a step for closing the shutoff valve 6 is provided between S201 and S202, and a process for opening the shutoff valve 6 (and closing the pressure reducing control valve 8) in S207 is added, so that the front wheel side in automatic brake control such as VDC control can be performed. The control flow can be realized.

[Effect of Example 1]
Hereinafter, effects of the vehicle brake device according to the present invention ascertained from the first embodiment will be listed.

  (1) The vehicle brake device according to the present invention includes a motor M that drives the drive wheels RL and RR of the vehicle. In the vehicle brake device that performs regenerative braking using the motor M as a generator during regenerative braking, , A brake pedal BP that is operated by a driver's pedaling force in conjunction with the master cylinder MC, a booster BS that operates the master cylinder MC, wheel cylinders 5a to 5d provided on each wheel of the vehicle, and a booster BS And the first brake circuit 1 for supplying the brake fluid boosted by at least the wheel cylinders 5a, 5b of the driven wheels FL, FR, and the brake fluid (supplied to the driven wheels FL, FR) when regenerative braking is performed. The regenerative braking force of the drive wheels RL and RR is increased while the hydraulic pressure of the engine is reduced.

  That is, conventionally, a so-called brake-by-wire (hereinafter referred to as “BBW”) system has been used as a vehicle brake device that controls hydraulic braking force in coordination with regenerative braking force and ensures a brake pedal operation feeling. . In this system, the brake pedal and the wheel cylinder are not mechanically connected, the amount of brake pedal operation by the driver is electrically detected, and the wheel cylinder pressure is electrically detected based on the detected value and various vehicle information. Control. In other words, the hydraulic pressure generated in the master cylinder by the operation of the brake pedal is not supplied to the wheel cylinder as it is, and the wheel cylinder pressure (hydraulic braking force) is generated by an electric pressurizing means (electric pump) different from the master cylinder. ) Is controlled. Further, the brake pedal operation feeling is ensured by applying the master cylinder pressure generated by the driver operation to a pseudo load (stroke simulator).

  However, since the above-mentioned BBW system does not have a booster and electrically controls the wheel cylinder pressure, it is necessary to ensure the reliability of the power supply system and the control unit. In order to ensure reliability, it is common to build an electrical redundant system. Therefore, in addition to the necessity of providing the pseudo load, there is a problem that the entire system becomes large and complicated, and the cost is increased.

  On the other hand, the vehicle brake device according to the first embodiment includes a booster BS, and the brake pedal BP and the wheel cylinder 5 are mechanically connected to each other, and is generated by a driver's brake operation. A conventional hydraulic brake device β (different from BBW) in which the master cylinder pressure is directly applied to the wheel cylinder 5 is used. For this reason, the whole brake device that performs regenerative cooperative control can be reduced in size and simplified, and the cost can be reduced.

  That is, even when the electrical system that operates the hydraulic pressure source (pump P) fails (when the pressure increase by the second brake circuit 2 is impossible), the driver is driven by the booster BS that operates the master cylinder MC. Therefore, there is no possibility that the braking force will be reduced. Therefore, it is not necessary to make the electrical system (CPU and sensor system) redundant to ensure reliability, and no pseudo load is required. Therefore, the apparatus can be reduced in size and simplified, and the cost can be reduced.

  Further, when performing regenerative braking and performing regenerative cooperative control, the brake hydraulic pressure supplied from the master cylinder MC to the wheel cylinders 5a and 5b of the front wheels (driven wheels) is reduced, while the hydraulic braking force on the front wheels is reduced. The regenerative braking force on the rear wheel side is increased by the decrease. Specifically, the regenerative braking force command value is set to a value larger than normal (but not more than the mechanical / electrical maximum value), and a regenerative braking force corresponding to this value is generated on the rear wheels. Therefore, it is possible to increase the kinetic energy (regenerative energy) recovered by regeneration while maintaining the braking force of the entire vehicle.

  (2) Specifically, an operation amount detection means (stroke sensor 11) for detecting the operation amount (stroke Sp) of the brake pedal BP is provided, and the detected operation amount (stroke Sp) is a predetermined value when regenerative braking is performed. When it is equal to or lower than Spo, the hydraulic pressure of the brake fluid (supplied to the driven wheels FL and FR) is set to 0, while the regenerative braking force of the drive wheels RL and RR is increased.

  That is, a predetermined slow braking stroke region (0 ≦ Sp ≦ Spo) is used as the front wheel pressure reduction control region, and in this region, the wheel cylinder pressure of the front wheel is reduced to 0, while the regenerative braking force on the rear wheel side is correspondingly reduced. Increase. Thus, the decrease in the wheel cylinder pressure (hydraulic braking force) of the front wheels is not compensated by increasing the hydraulic braking force of the rear wheels, but is compensated by increasing the regenerative braking force. Therefore, regenerative energy can be increased while maintaining the braking force of the entire vehicle in a normal stroke range (0 ≦ Sp ≦ Spo).

  Note that the control to reduce the wheel cylinder pressure of the front wheels to 0 is limited to the slow braking stroke range (0 ≦ Sp ≦ Spo) where the driver does not require a high braking force, so the front wheels (driven wheels) By setting the hydraulic braking force of the vehicle to 0, there is no inconvenience that the vehicle behavior becomes unstable.

  (3) A decompression circuit (return circuit) that communicates with the low pressure part (reservoir RES) when the wheel cylinder pressure is reduced, and a decompression circuit (return circuit), and disconnects the wheel cylinders 5a, 5b and the low pressure part (reservoir RES). The pressure reducing control valves 8a and 8b are in contact with each other. When the brake fluid pressure is reduced, the pressure reducing control valves 8a and 8b are opened.

  That is, the brake fluid discharged from the wheel cylinders 5a to 5b by opening the decompression control valves 8a to 8b is returned to the reservoir RES. When the brake pedal BP is returned, the hydraulic chamber (pressurizing chamber) of the master cylinder MC communicates with the reservoir RES, and the returned brake fluid is again sucked into the hydraulic chamber of the master cylinder MC. Therefore, it is possible to smoothly reduce the wheel cylinder pressure (S24, S110, S207, S209) without causing the problem of the liquid volume balance. In particular, since the pressure can be reduced without going through the first brake circuit 1, the following effects can be obtained.

  Unlike the brake device of the present invention, the first brake circuit also serves as a pressure reducing circuit, that is, the brake fluid from the wheel cylinder is returned to the hydraulic pressure chamber (pressurizing chamber) of the master cylinder when the wheel cylinder pressure is reduced. In the conventional hydraulic brake device, the brake pedal is pushed back when the wheel cylinder pressure is reduced, which may give the driver a sense of incongruity. That is, it has been difficult to control the wheel cylinder pressure while keeping the reaction force of the brake pedal properly.

  On the other hand, in the hydraulic brake device β of the present invention, the reservoir RES communicates with the back pressure side of the master cylinder MC, and when the wheel cylinder pressure is reduced by the return circuit, the brake fluid is stored in the reservoir RES (the master cylinder MC). Return to the back pressure side. For this reason, when reducing the wheel cylinder pressure in regenerative cooperative control or ABS control, it is not necessary to consider the reaction force acting on the brake pedal BP, and it is only necessary to open the pressure reduction control valves 8a and 8b. Therefore, the pressure reduction control of the wheel cylinder pressure is simple and reliable, and the pressure reduction can be executed smoothly and accurately.

  (4) In the first brake circuit 1, the operation amount detecting means (stroke sensor 11) for detecting the operation amount (stroke Sp) of the brake pedal BP and the first brake circuit 1 are disconnected between the master cylinder MC and the wheel cylinders 5a and 5b. The first control valve (shutoff valves 6a and 6b) that are in contact with each other is provided, and when the regenerative braking is performed, the valve opening pressure of the first control valve (shutoff valves 6a and 6b) is set according to the detected operation amount (stroke Sp) I decided to control it.

  In this way, by controlling the valve opening pressure of the shutoff valve 6 according to the stroke Sp, the magnitude of the master cylinder pressure that transmits the reaction force to the brake pedal BP can be arbitrarily controlled according to the stroke Sp. Therefore, the brake pedal reaction force according to the driver's brake operation can be arbitrarily generated without providing a pseudo load generating means such as a stroke simulator. Therefore, even when the hydraulic brake device β mechanically connected between the brake pedal BP and the wheel cylinder 5 is used, regenerative cooperative control can be realized while ensuring an appropriate brake pedal operation feel.

  When combined with the configuration (3) above, the reduction of the front wheel cylinder pressure does not interfere with the valve opening pressure control of the shut-off valve 6, so it is necessary for generating the brake pedal reaction force and increasing the regenerative braking force. The front wheel wheel cylinder pressure can be reduced independently of each other.

  (5) A first control valve (shutoff valve 6a, 6b) provided in the first brake circuit 1 for connecting / disconnecting between the master cylinder MC and the wheel cylinders 5a, 5b, and a low pressure portion (reservoir) when the wheel cylinder pressure is reduced. A pressure reducing circuit (return circuit) communicating with RES), and pressure reducing control valves 8a and 8b provided in the pressure reducing circuit (return circuit) for connecting and disconnecting between the wheel cylinders 5a and 5b and the low pressure part (reservoir RES), I decided to have it.

  Since the pressure reducing circuit (return circuit) and the pressure reducing control valves 8a and 8b are thus provided, the wheel cylinder pressure can be reduced without going through the first brake circuit 1. Moreover, the brake pedal reaction force can be arbitrarily generated by controlling the first control valves (shutoff valves 6a and 6b). Since the master cylinder pressure (brake pedal reaction force) and the front wheel wheel cylinder pressure (hydraulic braking force) can be controlled independently as described above, the front wheel wheel cylinder pressure is reduced (necessary for increasing the regenerative braking force) Both generation of brake pedal reaction force can be achieved. Therefore, even when the hydraulic brake device β mechanically connected between the brake pedal BP and the wheel cylinders 5a and 5b is used, the hydraulic braking force on the front wheel side is reduced while ensuring an appropriate brake pedal operation feel. Thus, the regenerative braking force on the rear wheel side can be increased.

  (6) A hydraulic pressure source (pump P) provided separately from the booster BS and provided in parallel to the first brake circuit 1 and boosted by the hydraulic pressure source (pump P). Second brake circuit 2 for supplying the brake fluid to the wheel cylinders 5a to 5d, and an increase / decrease between the hydraulic pressure source (pump P) and the wheel cylinders 5a to 5d provided in the second brake circuit 2. And a control unit (brake control unit BCU) for controlling the operation of the pressure control valves 7a to 7d, the pressure increase control valves 7a to 7d and the hydraulic pressure source (pump P), and the control unit (brake control unit BCU). When at least one of the pressure increase control valves 7a to 7d is controlled to open, the hydraulic pressure source (pump P) is operated to increase the pressure in the wheel cylinders 5a to 5d (S104, S203). .

Therefore, even if the rear wheels RL and RR are not mechanically connected to the master cylinder MC, the wheel cylinder pressure of the rear wheels can be arbitrarily controlled.
Further, in the end process (S100) after reducing the wheel cylinder pressure of the front wheel and increasing the amount of regenerative energy, the hydraulic pressure source (pump P) is operated before the shutoff valve 6 is opened, and the inside of the wheel cylinders 5a and 5b. If the pressure is increased, the differential pressure between the master cylinder pressure and the wheel cylinder pressure can be eliminated in advance (S101 to S105), so that the pedal operation feeling when the shut-off valve 6 is opened can be improved.

  Also, as a brake fluid supply path to the front wheel cylinders 5a and 5b, the first brake circuit 1 by the driver's operation (master cylinder MC) and the second brake circuit 2 by the hydraulic pressure source (pump P) are separately provided. The first brake circuit 1 and the second brake circuit 2 are appropriately selected (by controlling the shutoff valves 6a and 6b and the pressure increase control valves 7a and 7b) when the front wheel wheel cylinder pressure is increased. did. Therefore, interference between the pressure increase by the driver's operation and the pressure increase by the hydraulic pressure source can be prevented, and the controllability and pedal operation feeling can be improved. Specifically, the following effects can be obtained.

  First, for example, during VDC control, the second brake circuit 2 is selected for the wheel cylinder (eg, 5a) of the control wheel, and the first brake circuit 1 is selected for the wheel cylinder (eg, 5b) of the non-control wheel. Therefore, when the driver steps on during the VDC control, the brake fluid can be directly supplied from the master cylinder MC to the wheel cylinder 5b of the non-control wheel. Therefore, the driver's intention can be directly reflected and the controllability can be improved. Moreover, since the stroke of the brake pedal BP is ensured, pedal operation feeling is good.

  Secondly, at the time of normal braking in which pressure is increased by the driver's operation, the first brake circuit 1 is selected and pressure is increased via the shut-off valve 6 by the master cylinder pressure. On the other hand, at the time of control brake (VDC control or the like) in which pressure is increased by the hydraulic pressure source (pump P), the pressure is increased via the pressure increase control valve 7 by the pump pressure in the second brake circuit 2. Thereby, the characteristics of the first brake circuit 1 and the second brake circuit 2 can be set independently of each other. For example, the valve seat diameter of the shutoff valve 6 is set to be suitable for a normal brake (for example, the pressure increase response is improved by increasing the seat diameter), and the valve seat diameter of the pressure increase control valve 7 is set as a control brake (wheel cylinder pressure control). A suitable setting (for example, the control accuracy is improved by reducing the sheet diameter) can be achieved. Therefore, the response during normal braking can be improved, and the control accuracy during control braking can be improved.

  Third, during the BA control, the master cylinder pressure generated by the driver's brake operation is supplied to the wheel cylinders 5a and 5b via the first brake circuit 1 while the brake fluid is supplied regardless of the driver's brake operation. Pump pressure is supplied to the wheel cylinders 5a, 5b via the second brake circuit 2 (which can be supplied). In the second brake circuit 2, the hydraulic pressure source (pump P) sucks brake fluid directly from the reservoir RES without passing through the master cylinder MC, so the wheel cylinder pressure is increased regardless of the moving speed of the master cylinder MC (piston). The pressure can be increased. Thus, during BA control, the wheel cylinder pressure can be increased at a speed higher than the operating speed of the driver by operating the hydraulic pressure source (pump P) while increasing the pressure by the master cylinder MC. Therefore, the wheel cylinder pressure increase response in BA control can be improved.

  (7) At the end of regenerative braking, the first control valve (shutoff valve 6) is controlled according to the wheel cylinder pressure.

  That is, in the termination process (S100) of the first embodiment, the shut-off valve 6 is opened (S108) after the front wheel cylinder pressure is matched with the master cylinder pressure (S101 to S107). Therefore, a sudden change in the stroke Sp of the brake pedal BP when the shutoff valve 6 is opened is suppressed, and a natural pedal operation feeling can be realized.

  The vehicle brake device of the second embodiment changes the relationship between the stroke Sp of the brake pedal BP and the master cylinder pressure (target value) in the characteristic map (FIG. 8) of the first embodiment, and controls the shutoff valve 6 accordingly. The logic is changed. Other configurations are the same as those in the first embodiment.

  FIG. 16 is a characteristic map of the second embodiment and shows the relationship between the stroke Sp and the pressure (master cylinder pressure and front wheel cylinder pressure). The characteristics of the front wheel cylinder pressure are set in the same manner as in the first embodiment (FIG. 8). The slow braking stroke region (0 ≦ Sp ≦ Spo) is a front wheel pressure reduction control region, and the front wheel wheel cylinder pressure target value is set to 0 in this region.

  On the other hand, regarding the characteristics of the master cylinder pressure, in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo), the master cylinder pressure target value is set to a constant value Pm2. In the front wheel pressure increase control region (Sp> Spo), the master cylinder pressure characteristic curve is parallel to the front wheel wheel cylinder pressure characteristic curve, and as the stroke Sp increases from Spo. It starts to increase gradually from Pm2. When the stroke Sp becomes a predetermined value (> Spo) or more, the increase gradient of the master cylinder pressure becomes constant (substantially the same as the increase gradient of the wheel cylinder pressure), and the master cylinder pressure increases in proportion to the stroke Sp.

(Front wheel master cylinder pressure: shut-off valve control)
FIG. 17 shows a control flowchart of the shutoff valve 6 executed by the brake control unit BCU of the second embodiment.

  In S31, as in S11 (FIG. 9) of the first embodiment, it is determined whether or not to start front wheel side control. When starting control, the process proceeds to S32. If control on the front wheel side is unnecessary, the process proceeds to S39, and the shutoff valve 6 is kept fully open.

  In S32, the input of the detected value of the stroke Sp is received from the stroke sensor 11, and the process proceeds to S33.

  In S33, it is determined whether or not the detected stroke Sp is in the slow braking stroke region (0 ≦ Sp ≦ Spo), that is, the front wheel pressure reduction control region. If 0 ≦ Sp ≦ Spo, the process proceeds to S37, and if Sp> Spo, the process proceeds to S34.

  In S37, the valve opening pressure of the shutoff valve 6 is set to Pm2. That is, a constant current value I that realizes the valve opening pressure = Pm2 is passed through the coils 68 of the shutoff valves 6a and 6b. Thereafter, the process proceeds to S38.

  In S34, the detection value of the front wheel cylinder pressure is received from the wheel cylinder pressure sensors 13a and 13b, and the process proceeds to S35.

  In S35, based on the detected stroke Sp, a master cylinder pressure target value is calculated using the characteristic map of FIG. 16, and the process proceeds to S36.

  In S36, the valve opening pressure of the shutoff valves 6a and 6b is set to (master cylinder pressure target value−wheel cylinder pressure detection value). That is, according to the graph of FIG. 4, a current value I that realizes the valve opening pressure = (master cylinder pressure target value−wheel cylinder pressure detection value) is passed through the coils 68 of the shutoff valves 6a and 6b. Thereafter, the process proceeds to S38.

  In S38, as in S17 (FIG. 9) of the first embodiment, it is determined whether or not the front wheel side control is to be terminated. When the process ends, the process proceeds to S100 (FIG. 13), and the end process is executed. If not, return to S32. That is, in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo), the process of S37 is repeated until the end of control on the front wheel side is determined, and the valve opening pressures of the shutoff valves 6a and 6b are kept at a constant value Pm2. On the other hand, in the front wheel pressure increase control region (Sp> Spo), the brake pedal reaction force corresponding to the stroke Sp is obtained by repeating the processes from S34 to S36 until it is determined that the control on the front wheel side is finished.

  As described above, in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo), a constant control current is supplied to the shutoff valves 6a and 6b. Since the front wheel cylinder pressure is also controlled to 0 at this time, the master cylinder pressure is controlled to a constant value, and a constant brake pedal reaction force can always be obtained. At this time, since only S37 is repeatedly executed (only the constant current value I is output), it is possible to simplify the control logic in a stroke region (0 ≦ Sp ≦ Spo) that is normally used frequently.

[Effect of Example 2]
(8) During regenerative braking, if the detected brake pedal actuation amount (stroke Sp) is less than or equal to a predetermined value Spo, the valve opening pressure of the first control valve (shutoff valves 6a and 6b) is controlled to a constant value Pm2. It was decided.

  Therefore, a constant brake pedal reaction force can always be obtained in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo). At this time, in order to control the valve opening pressure to a constant value Pm2, it is only necessary to keep a constant current flowing through the first control valve (shut-off valves 6a, 6b). The control logic in the region (0 ≦ Sp ≦ Spo) can be simplified, and the capacity of operations and the like can be reduced.

  The vehicle brake device according to the third embodiment is obtained by changing the relationship between the stroke Sp of the brake pedal BP and the wheel cylinder pressure in the characteristic map of the first embodiment (FIG. 8), and changing the control logic on the front wheel side accordingly. It is. Other configurations are the same as those in the first embodiment.

  FIG. 18 is a characteristic map of Example 3, showing the relationship between the stroke Sp and the pressure (master cylinder pressure and front wheel wheel cylinder pressure). The characteristics of the master cylinder pressure are set in the same manner as in the first embodiment (FIG. 8).

  On the other hand, regarding the characteristics of the front wheel cylinder pressure, the slow braking stroke area of 0 ≦ Sp ≦ Spo is the minute pressure increase control area of the front wheels FL and FR. In this area, the front wheel cylinder pressure is proportional to the stroke Sp. It is set so as to rise gently, that is, with a small constant increase gradient. That is, while the front wheel cylinder pressure is reduced to 0 in the first embodiment in the slow braking stroke region, the pressure is slightly increased in the third embodiment.

  Therefore, the valve opening pressure of the shut-off valve 6 increases from the constant value Pmo as the stroke Sp increases from 0 in the front wheel minute pressure increase control region, and is slightly smaller than Pm1 when Sp = Spo.

  On the other hand, the sudden braking stroke region of Sp> Spo is set in the pressure increase control region of the front wheels FL and FR (due to a large increase gradient) as in the first embodiment. Specifically, the increasing gradient of the front wheel cylinder pressure gradually increases as the stroke Sp increases from Spo, and is constant when the stroke Sp exceeds a predetermined value (> Spo) (approximately the same as the increasing gradient of the master cylinder pressure). It becomes.

  FIG. 19 shows a flowchart of wheel cylinder pressure control on the front wheel side in the third embodiment.

  In step S301, it is determined whether or not the front wheel side control is to be started in the same manner as in S21 of the first embodiment (FIG. 12). When starting the control, the process proceeds to S302. When it is determined in S301 that the front wheel side control is not performed, the process proceeds to S313, the pressure increase control valves 7a and 7b and the pressure reduction control valves 8a and 8b are kept in a fully closed state, and this control flow is ended.

  In S302, the detection value of the stroke Sp is received from the stroke sensor 11, and the process proceeds to S303.

  In S303, it is determined whether or not the detected stroke Sp is in the slow braking stroke region (0 ≦ Sp ≦ Spo), that is, the front wheel minute pressure increase control region. If 0 ≦ Sp ≦ Spo, the process proceeds to S304, and if Sp> Spo, the process proceeds to S313.

  In S304, the wheel cylinder pressure target value for the front wheels is calculated based on the characteristic map of FIG. 18 according to the detected stroke Sp, and the process proceeds to S305.

  In S305, it is determined whether to increase the front wheel cylinder pressure based on the target value and detection value of the wheel cylinder pressure. If the pressure is increased, the process proceeds to S306. If the pressure is not increased, the process proceeds to S308.

  In S306, the decompression control valves 8a and 8b are not controlled, and are kept in the fully closed state. Further, the motor M1 is controlled to drive the pump P. The brake fluid is supplied to the wheel cylinders 5a and 5b by controlling the pressure increase control valves 7a and 7b. Thereafter, the process proceeds to S307.

  In S307, it is determined whether or not the wheel cylinder pressure has reached the target value in the characteristic map (FIG. 18) based on the detected values of the wheel cylinder pressure sensors 13a and 13b. When the target value is reached, the process proceeds to S311. If not reached, the process returns to S306, and the wheel cylinders 5a and 5b are continuously increased in pressure. By repeating S306 and S307, a slight increase in the wheel cylinder pressure is realized.

  In S311, the pressure increase control valve 7 and the pressure reduction control valve 8 are closed to maintain the wheel cylinder pressure. Thereafter, the process proceeds to S312.

  In S312, the end of front wheel control is determined in the same manner as in S25 (FIG. 12) of the first embodiment. When continuing control, it returns to S302 and continues control. When the process ends, the process proceeds to S100 (FIG. 13), and the end process is executed.

  In S308, it is determined whether to reduce the front wheel cylinder pressure based on the target value and the detected value of the wheel cylinder pressure. When the pressure is reduced, the process proceeds to S309, and when the pressure is not reduced, the process proceeds to S311.

  In S309, the pressure-reducing control valves 8a and 8b are opened while the pressure-increasing control valves 7a and 7b are closed, and the reservoir RES and the wheel cylinders 5a and 5b are communicated to reduce the pressure of the front wheel wheel cylinder to the reservoir RES. Thereafter, the process proceeds to S310.

  In S310, based on the detected values of the wheel cylinder pressure sensors 13a and 13b, it is determined whether or not the front wheel cylinder pressure has reached the target value in the characteristic map (FIG. 18). When the target value is reached, the process proceeds to S311 and the wheel cylinder pressure reduction is terminated. If not, the process returns to S309, and the wheel cylinders 5a and 5b are continuously depressurized.

  That is, in the front wheel minute pressure increase control region (0 ≦ Sp ≦ Spo), the processing from S304 to S310 is repeated until it is determined that the front wheel side control is finished. As a result, the wheel cylinder pressure of the front wheels FL and FR is increased or decreased, and the wheel cylinder pressure matches the target value in the characteristic map (FIG. 18). In other words, when the detected stroke Sp is in the stroke range (0 ≦ Sp ≦ Spo) during slow braking, the front wheel wheel cylinder pressure is not reduced to 0, but is increased slightly according to the stroke Sp. That is, a slight hydraulic braking force by the brake fluid supplied from the master cylinder MC is generated on the front wheels.

[Effect of Example 3]
(9) If the detected brake pedal operation amount (stroke Sp) is less than or equal to the predetermined value Spo during regenerative braking, the brake fluid pressure (wheel cylinder pressure) is slightly increased according to the operation amount (stroke Sp). On the other hand, the regenerative braking force of the drive wheels (rear wheels RL, RR) is increased.

  Therefore, at the time of slow braking, the hydraulic braking force corresponding to the stroke Sp can be left on the front wheel side while increasing the regenerative braking force on the rear wheel side by the amount corresponding to the reduction in the wheel cylinder pressure on the front wheel side. In other words, it is possible to secure a higher braking force for the entire vehicle during the regenerative cooperative control. Therefore, the brake device of the present invention is also applied to a vehicle that requires a high braking force during slow braking (compared to the first and second embodiments) due to a large vehicle weight, etc. Regenerative energy can be increased while stabilizing.

  The vehicle brake device according to the fourth embodiment differs from the processing according to the first to third embodiments (FIG. 13) in the end processing (S100) at the end of front wheel control. Other configurations are the same as those in the first or second embodiment.

  FIG. 20 illustrates a termination process according to the fourth embodiment. The termination process (S100) has only step S120. In S120, the front wheel side pressure reduction control valves 8a, 8b (and pressure increase control valves 7a, 7b) are closed, and the shutoff valves 6a, 6b are opened to complete the termination process. At this time, the current value I flowing through the coil 68 of the shutoff valves 6a and 6b is controlled to control the amount of change per hour of the valve opening Xv of the shutoff valve 6. Thereby, the time change of the front wheel wheel cylinder pressure and the master cylinder pressure after the end of front wheel control is adjusted.

  FIG. 21 is a time chart showing temporal changes in the valve opening Xv of the shutoff valves 6a and 6b. During the control on the front wheel side, the valve opening Xv is controlled to a predetermined value. When the front wheel control ends, the end process (S120) is started. In this termination process, the valve opening Xv is increased to a maximum opening at a predetermined speed. FIG. 21 (a) shows a time chart when the amount of time change (increase in gradient) of the valve opening degree Xv is large, that is, when the shutoff valve 6 is rapidly opened. FIG. 21B shows a time chart in the case where the amount of time change (increase in gradient) of the valve opening Xv is small and the shutoff valve 6 is opened gently.

  22 and 23 show time charts of the master cylinder pressure and the front wheel wheel cylinder pressure when the above end processing is performed at the end of front wheel control. FIG. 22A and FIG. 23 show a case where the shutoff valve 6 is rapidly opened, and corresponds to FIG. FIG. 22B shows a case where the shutoff valve 6 is gently opened, and corresponds to FIG.

  22 (a) and 22 (b) show a case where the brake operation state (stroke Sp) of the driver is constant, but the control on the front wheel side is terminated when the signal sent from the vehicle side indicates that the regenerative braking is not possible. The time chart of is shown. It is assumed that the stroke Sp is in the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo) at all times.

  In FIG. 22, during the control of the front wheels, the front wheel wheel cylinder pressure is controlled to zero by opening the pressure reduction control valves 8a and 8b. When the front wheel control is terminated and the termination process (S120) is started, the pressure reducing control valves 8a and 8b are closed, and the shutoff valves 6a and 6b are opened at a predetermined speed. As a result, the first brake circuit 1 communicates and brake fluid is supplied from the high pressure master cylinder MC (pressure chamber) toward the low pressure wheel cylinders 5a and 5b. At this time, the master wheel pressure decreases and at the same time the front wheel cylinder pressure increases, and finally they coincide at a predetermined pressure corresponding to the depression amount (stroke Sp) of the brake pedal BP.

  As shown in FIG. 22 (a), when the shut-off valves 6a and 6b are opened rapidly, the master cylinder pressure decreases rapidly while the wheel cylinder pressure increases rapidly. It becomes. Therefore, both pressures are stabilized in a short time after the front wheel control is completed. On the other hand, as shown in FIG. 22 (b), when the shut-off valves 6a and 6b are opened gently, the master cylinder pressure gradually decreases while the wheel cylinder pressure gradually increases, so that both pressures reach the predetermined pressure. Converge slowly. Therefore, after the front wheel control is finished, the time change (decrease gradient) of the master cylinder pressure becomes gentle, and the rapid fluctuation of the stroke Sp is suppressed.

  In FIG. 23, the value of the stroke Sp shifts from the front wheel pressure reduction control region (0 ≦ Sp ≦ Spo) to the front wheel pressure increase control region (Sp> Spo), and then the front wheel control is terminated by returning the brake pedal BP. A time chart for the case is shown. In the pressure reduction control region (0 ≦ Sp ≦ Spo), the front wheel wheel cylinder pressure is maintained at zero by the valve opening control of the pressure reduction control valves 8a and 8b (S24 in FIG. 12). In the pressure increase control region (Sp> Spo), the front wheel wheel cylinder pressure is controlled to a value corresponding to the stroke Sp by the control of the shutoff valves 6a and 6b (S13 to S16 in FIG. 9).

  When the control of the front wheels is completed by returning the brake pedal BP, an end process (S120) for opening the shutoff valves 6a and 6b is started. When the brake pedal BP is returned with the shut-off valves 6a and 6b opened as described above, the hydraulic chamber (pressurizing chamber) of the master cylinder MC and the reservoir RES communicate with each other via the cup-shaped seal member, and the master cylinder. The pressure is reduced. Along with this, the brake fluid supplied to the front wheel cylinders 5a and 5b is also returned to the reservoir RES via the first brake circuit 1 and the shutoff valve 6, and the front wheel cylinder pressure is also reduced.

  That is, in the fourth embodiment, when the control of the front wheel is finished, the opening of the shut-off valve 6 is controlled in accordance with the operating direction of the brake pedal BP (whether it is a depressing direction or a returning direction). On the other hand, in Examples 1 to 3, after the brake pedal BP is returned, the wheel cylinder pressure is matched with the master cylinder pressure (that is, according to the front wheel cylinder pressure), and then the shut-off valve 6 is opened. Control.

  Thus, when the shutoff valve 6 is opened in the termination process (S120), the brake pedal BP is being returned. Here, in the return direction of the brake pedal BP, unlike the depression direction, fluctuations in the reaction force acting on the brake pedal BP rarely give the driver an uncomfortable feeling as a pedal operation feeling. Further, the wheel cylinder pressure is lower than the master cylinder pressure during the front wheel control (regenerative cooperative control) and at the end thereof. For this reason, even if the shut-off valve 6 is rapidly opened at the end of front wheel control, the wheel cylinder pressure does not increase the master cylinder pressure, and the reaction force in the return direction of the brake pedal BP does not occur. There is no possibility that the operation feeling will deteriorate.

  As described above, in the fourth embodiment, the front wheel cylinder pressure is reduced to zero in the slow braking stroke range (0 ≦ Sp ≦ Spo) as in the first and second embodiments. In this case, the following effects can be obtained.

[Effect of Example 4]
(10) At the end of regenerative braking, the first control valve (shutoff valve 6) is controlled in accordance with the operating direction of the brake pedal BP.

  Therefore, at the end of regenerative braking (front wheel control), the shutoff valve 6 is controlled only in accordance with the operating direction of the brake pedal BP without depending on the front wheel cylinder pressure. Natural pedal operation feeling in the end process can be realized.

  Note that, as shown in FIG. 22, in this termination process, the amount of change (increase in gradient) per hour in the valve opening Xv of the shutoff valve 6 may be controlled. For example, when the shut-off valve 6 is opened rapidly after the front wheel control is finished (FIG. 22A), the master cylinder pressure and the wheel cylinder pressure can be stabilized in a short time. Therefore, it is effective when an emergency case is assumed, such as when a failure occurs. On the other hand, when the shut-off valve 6 is opened gently (FIG. 22B), the change per hour in the master cylinder pressure can be moderated, and the rapid fluctuation of the stroke Sp can be suppressed. In this case, especially when regenerative braking is terminated with the brake pedal BP depressed, the pedal operation feeling can be further improved, so that the change time of the master cylinder pressure and the wheel cylinder pressure may be long. It is effective for.

[Other embodiments]
The best mode for carrying out the present invention has been described based on the first to fourth embodiments. However, the specific configuration of the present invention is not limited to the first to fourth embodiments. Even if there is a design change or the like within a range not departing from the gist, it is included in the present invention.

  For example, in Examples 1 to 4, the brake fluid boosted by the booster BS is supplied to the wheel cylinders 5a and 5b of the front wheels FL and FR that are driven wheels. The RR side may have a hydraulic circuit configuration similar to that of the front wheels FL and FR, and the brake fluid boosted by the booster BS may be supplied to the wheel cylinders 5c and 5d of the rear wheels RL and RR that are drive wheels. . Also in this case, during regenerative braking, the hydraulic pressure of the supplied brake fluid is reduced, and the regenerative braking force of the drive wheels is increased by this reduction, so that the same effect as described above can be obtained.

  In the first to fourth embodiments, the rear wheel is the driving wheel and the front wheel is the driven wheel. Conversely, the front wheel may be the driving wheel and the rear wheel may be the driven wheel. For example, the master cylinder MC and the wheel cylinders 5c and 5d only on the rear wheel side are connected via the first brake circuit 1, and the hydraulic pressure source (pump P) and the wheel cylinders for the front and rear wheels are connected via the second brake circuit 2. 5a to 5d may be connected, and the front wheels FL and FR (wheel cylinders 5a and 5b) may be increased only through the second brake circuit 2. In this case, the same effect as described above can be obtained.

  In Examples 1 to 4, so-called proportional valves in which the valve opening varies in proportion to the current value are used as the shutoff valve 6, the pressure increase control valve 7, and the pressure reduction control valve 8. A so-called on / off valve that takes only two closed positions may be used. Further, for example, the on / off valve and the proportional valve may be used in combination such that the shutoff valve 6 is an on / off valve, and the pressure increase control valve 7 and the pressure reduction control valve 8 are proportional valves.

1 is an overall system diagram of a hybrid vehicle to which a vehicle brake device is applied. 1 shows a hydraulic circuit configuration of a hydraulic brake device. It is an axial sectional view of a cutoff valve. It is a graph which shows the relationship between the valve opening pressure of a cutoff valve, and an electric current value. The distribution of braking force between the front and rear wheels when regenerative cooperative control is not performed during normal braking is shown. It is a characteristic map which shows the relationship between a rear-wheel wheel cylinder pressure and a master cylinder pressure. The distribution of braking force between the front and rear wheels when regenerative cooperative control is performed during normal braking is shown. 3 is a characteristic map showing a relationship between a brake pedal stroke, a master cylinder pressure, and a front wheel cylinder pressure in the first embodiment. It is a control flowchart of a shut-off valve. It is a start judgment flow of control on the front wheel side. It is an end judgment flow of front wheel side control. It is a control flowchart of front wheel wheel cylinder pressure. It is a flowchart of the completion | finish process of front-wheel control. 3 is a time chart at the end of front wheel control in the first embodiment. It is a control flowchart on the rear wheel side. It is a characteristic map which shows the relationship between the brake pedal stroke in Example 2, a master cylinder pressure, and a front wheel wheel cylinder pressure. 6 is a control flowchart of a shut-off valve in Embodiment 2. It is a characteristic map which shows the relationship between the brake pedal stroke in Example 3, a master cylinder pressure, and wheel cylinder pressure. 10 is a control flowchart of a front wheel cylinder pressure in the third embodiment. 14 is a flowchart of a front wheel control end process according to the fourth embodiment. It is a time chart of the shut-off valve opening degree at the time of the end of front wheel control in Example 4. It is a time chart of master cylinder pressure and wheel cylinder pressure at the time of the end of front wheel control in Example 4 (when a brake pedal is not returned). It is a time chart of master cylinder pressure and wheel cylinder pressure at the time of the end of front wheel control in Example 4 (when a brake pedal is returned).

Explanation of symbols

1 First brake circuit 2 Second brake circuit 3 Oil passage (return circuit)
5 Wheel cylinder 6 Shut-off valve 7 Pressure increase control valve 8 Pressure reduction control valve 11 Stroke sensor 12 Master cylinder pressure sensor 13 Wheel cylinder pressure sensor 68 Coil
B Battery
BCU brake control unit
BP brake pedal
BS booster
HU hydraulic controller
I inverter
M motor
M1 motor (for pump drive)
MC master cylinder
P pump
RES reservoir β Hydraulic brake device γ Regenerative brake device

Claims (8)

In a vehicle brake device that includes a motor that drives a drive wheel of a vehicle and that performs regenerative braking using the motor as a generator during regenerative braking,
A master cylinder,
A brake pedal that is operated by a driver's pedaling force in conjunction with the master cylinder;
A booster for operating the master cylinder;
A wheel cylinder provided on each wheel of the vehicle;
A first brake circuit that supplies at least the brake fluid boosted by the booster to the wheel cylinder of the driven wheel,
A vehicular brake device characterized by reducing the hydraulic pressure of the brake fluid during regenerative braking and increasing the regenerative braking force of the drive wheels. The vehicle brake device according to claim 1,
A pressure reducing circuit communicating with the low pressure portion when the wheel cylinder pressure is reduced;
A pressure reducing control valve provided in the pressure reducing circuit, for connecting and disconnecting the wheel cylinder and the low pressure portion;
A vehicular brake device that opens the pressure-reducing control valve when the brake fluid pressure is reduced. The vehicle brake device according to claim 1 or 2,
An operation amount detecting means for detecting an operation amount of the brake pedal;
In the first brake circuit, a first control valve for connecting and disconnecting between the master cylinder and the wheel cylinder is provided,
A vehicular brake device that controls a valve opening pressure of the first control valve in accordance with the detected operation amount when the regenerative braking is performed. The vehicle brake device according to claim 3,
When the regenerative braking is performed, if the detected operation amount is equal to or less than a predetermined value, the valve opening pressure of the first control valve is controlled to a constant value. The vehicle brake device according to claim 3,
When the detected amount of operation is less than or equal to a predetermined value when the regenerative braking is performed, the hydraulic pressure of the brake fluid is slightly increased according to the amount of operation, and the regenerative braking force of the drive wheel is increased. Brake device for vehicles characterized by this. The vehicle brake device according to any one of claims 3 to 5,
The vehicle brake device according to claim 1, wherein when the regenerative braking is finished, the first control valve is controlled according to a wheel cylinder pressure or an operating direction of a brake pedal. The vehicle brake device according to claim 1,
A first control valve provided in the first brake circuit for connecting and disconnecting between the master cylinder and the wheel cylinder;
A pressure reducing circuit communicating with the low pressure portion when the wheel cylinder pressure is reduced;
A vehicular brake device, comprising: a pressure reducing control valve provided in the pressure reducing circuit and connecting and disconnecting the wheel cylinder and the low pressure portion. In the vehicle brake device according to any one of claims 1 to 7,
A hydraulic pressure source provided separately from the booster for boosting the brake fluid;
A second brake circuit that is provided in parallel to the first brake circuit and supplies brake fluid boosted by the hydraulic pressure source to a wheel cylinder;
A pressure-increasing control valve provided in the second brake circuit for connecting / disconnecting between the hydraulic pressure source and the wheel cylinder;
A control unit for controlling the operation of the pressure increase control valve and the hydraulic pressure source,
The vehicle brake device according to claim 1, wherein the control unit operates the hydraulic pressure source to increase the pressure in the wheel cylinder at least when the pressure increase control valve is controlled to open.

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