Brake device

A brake device includes: a mechanical pressure regulating part having a high-pressure port, a low-pressure port, a pilot pressure input port, and an output port which outputs fluid pressure corresponding to the pressure supplied to the pilot pressure input port by fluid pressures supplied to both of the high- and low-pressure ports, to a chamber for a master piston; a high-pressure source connected to the high-pressure port and the pilot pressure input port; a low-pressure source connected to the low-pressure port and the pilot pressure input port; and an electrically-operated pilot pressure generating part which includes control valves for controlling flows of the brake fluid between the high-pressure source and the pilot pressure input port, and between the low-pressure source and the pilot pressure input port, respectively, and which outputs desired fluid pressure to the pilot pressure input port by controlling flow of the brake fluid with control valves.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C.§119 to Japanese Patent Application 2010-116279, filed on May 20, 2010, the entire content of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a brake device.

2. Description of Related Art

JP-A No. 2007-182122 describes one type of brake devices. As shown in FIG. 1 of JP-A No. 2007-182122, the brake device has a driving fluid pressure chamber (external fluid pressure chamber90p) that drives a master piston (rear master piston62) and a pressure booster90that is connected to the driving fluid pressure chamber. The pressure booster90has a fluid pressure source90aand a fluid pressure controller90b, which are controlled by an electronic controller13. The fluid pressure controller90bhas proportional solenoid valves96a,96bof a normally close type for pressure boost that are provided in parallel to each other on a fluid passage connected to a boost pressure port16P of a master cylinder60from the fluid pressure source90a, a proportional solenoid valve97of a normally open type for pressure reduction that is provided on a fluid passage connected to a pump reservoir91of the fluid pressure source90afrom the boost pressure port16P, and a proportional solenoid valve pressure gauge95bthat monitors pressure of the boost pressure port16P.

According to the above-described brake device, a brake fluid is supplied from the fluid pressure source90ato the external fluid pressure chamber90pthrough the proportional solenoid valves96a,96bof a normally close type for pressure boost. However, in general, flow rates per unit time of the proportional solenoid valves are relatively low. Accordingly, when high braking force is abruptly required in braking a vehicle, a supply amount of the brake fluid for driving the master piston becomes smaller than a desired amount, so that the sufficient braking force may not be provided in good responsiveness to the braking. In response, it can be considered to make a configuration of increasing the flow rates of the proportional solenoid valves or increase the number of proportional solenoid valves to be provided. However, in this case, the brake device would be enlarged and the cost would be increased.

SUMMARY

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a brake device capable of providing sufficient braking force in good responsiveness to sudden braking without causing the enlargement of the device and the increase of cost.

In order achieve the object, there is provided a brake device which comprises a mechanical pressure regulating part including: a high-pressure port, to which fluid pressure of high pressure is supplied; a low-pressure port, to which fluid pressure of lower pressure than the fluid pressure to be supplied to the high-pressure port is supplied; a pilot pressure input port, to which pilot fluid pressure is supplied; and an output port which outputs fluid pressure corresponding to the pressure supplied to the pilot pressure input port by the fluid pressures supplied to both of the high-pressure port and the low-pressure port, to a driving fluid pressure chamber which drives a master piston; a high-pressure source which is connected to the high-pressure port and the pilot pressure input port, and which accumulates fluid pressure of a brake fluid pumped by an electric pump; a low-pressure source which is connected to the low-pressure port and the pilot pressure input port, and which supplies lower pressure than the high-pressure source; and an electrically-operated pilot pressure generating part which includes a pressure boost control valve for controlling flow of the brake fluid between the high-pressure source and the pilot pressure input port, and a pressure reduction control valve for controlling flow of the brake fluid between the low-pressure source and the pilot pressure input port, and which outputs desired fluid pressure to the pilot pressure input port by controlling the flow of the brake fluid with the pressure boost control valve and the pressure reduction control valve.

According to the brake device as described above, the desired pilot fluid pressure is generated in correspondence to an operating amount of the brake operating member or vehicle state by controlling the pressure boost control valve and the pressure reduction control valve of the electrically-operated pilot pressure generating part and is then input into the pilot pressure input port of the mechanical pressure regulating part. Thereby, the fluid pressure, which corresponds to the output fluid pressure of the electrically-operated pilot pressure generating part applied to the pilot pressure input port, is output from the output port of the mechanical pressure regulating part. Like this, the pressure boost control valve and the pressure reduction control valve having the relatively low flow rate per unit time are used to generate the pilot fluid pressure, which can sufficiently exhibit a function even when a flow rate thereof is low, thereby controlling the mechanical pressure regulating part that can output the relatively high flow rate (per unit time). As a result, it is possible to provide a brake device capable of providing sufficient braking force in good responsiveness to sudden braking without causing the enlargement of the device and the increase of cost.

DETAILED DESCRIPTION

(1) First Illustrative Embodiment

Hereinafter, a first illustrative embodiment where a brake device is applied to a hybrid vehicle will be described with reference to the drawings.FIG. 1is an outline view showing a configuration of the hybrid vehicle,FIG. 2is an outline view showing a configuration of the brake device andFIG. 3is a sectional view showing a regulator that is a mechanical pressure regulating part.

As shown inFIG. 1, the hybrid vehicle is a vehicle that drives driving wheels, for example, left and right front wheels Wfl, Wfr by a hybrid system. The hybrid system has a power train that combines and uses two types of power sources, i.e., an engine1and a motor2. In the first illustrative embodiment, the system is a parallel hybrid system that directly drives the wheels from the engine1and the motor2. In the meantime, there is a series hybrid system in which the wheels are driven by the motor2and the engine1serves as a power supplying source to the motor2.

The hybrid vehicle having the parallel hybrid system mounted thereon has the engine1and the motor2. A driving force of the engine1is transmitted to driving wheels (left and right front wheels Wfl, Wfr, in the first illustrative embodiment) through a power dividing mechanism3and a power transmission mechanism4and a driving force of the motor2is transmitted to the driving wheels through the power transmission mechanism4. The power dividing mechanism3appropriately divides the driving force of the engine1into a vehicle driving force and a generator driving force. The power transmission mechanism4appropriately integrates and transmits the driving forces of the engine1and the motor2in response to traveling conditions. The power transmission mechanism4adjust a ratio of the driving forces of the engine1and the motor2to be transmitted within a range of 0:100 to 100:0. The power transmission mechanism4has a shift transmission function.

The motor2increases the driving force by assisting the output of the engine1and charges a battery7by performing generation of electricity in braking the vehicle. A generator5generates electricity by the output of the engine1and has a starter function in starting the engine. The motor2and the generator5are electrically connected to an inverter6, respectively. The inverter6is electrically connected to the battery7that is a direct current power supply, and converts alternating current voltages input from the motor2and the generator5into a direct current voltage and supplies the direct current voltage to the battery7or converts a direct current voltage from the battery7into an alternating current voltage and outputs the alternating current voltage to the motor2and the generator5.

In the first illustrative embodiment, the motor2, the inverter6and the battery7configure a regenerative brake device A. The regenerative brake device A generates a regenerative braking force to any of the respective wheels Wfl, Wfr, Wrl, Wrr (left and right front wheels Wfl, Wfr that are driven by the motor2serving as a driving source, in the first illustrative embodiment), based on a brake operating state detected by a pedal stroke sensor11a(or pressure sensor P).

The engine1is controlled by an engine ECU (Electronic Control Unit)8. The engine ECU8outputs a degree-of-opening command to an electronic control throttle in response to an engine output required value from a hybrid ECU9, which will be described later, thereby adjusting the number of revolutions of the engine1. The hybrid ECU9is connected in communication with the inverter6. The hybrid ECU9calculates necessary engine output, electric motor torque and generator torque from a degree of opening of an accelerator and a shift position (which is calculated from a shift position signal input from a shift position sensor (not shown)), outputs the calculated engine output required value to the engine ECU8to control the driving force of the engine1and controls the motor2and the generator5through the inverter6in response to the calculated electric motor torque required value and generator torque required value. Also, the hybrid ECU9is connected with the battery7and monitors a charging state, a charged current and the like of the battery7. In addition, the hybrid ECU9is connected to an accelerator degree-of-opening sensor (not shown) that is assembled to an accelerator pedal (not shown) and detects a degree of opening of a vehicle accelerator and is input with an accelerator degree-of-opening signal from the accelerator degree-of-opening sensor.

In addition, a brake ECU17is connected in communication with the hybrid ECU9and cooperatively controls regenerative braking and hydraulic braking by the motor2so that a total braking force of the vehicle is equivalent to that of a vehicle having a hydraulic brake only. Specifically, the brake ECU17outputs a regeneration required value, which the regenerative brake device should bear from the total braking force, to the hybrid ECU9, as a target value of the regenerative brake device, i.e., a target regenerative braking force, in response to the braking request of a driver, i.e., braking operation state. Based on the input regeneration required value (target regenerative braking force), the hybrid ECU9calculates an actual regenerative execution value that is enabled to actually operate as a regenerative brake while considering vehicle speed, battery charging state and the like, controls the motor2through the inverter6so that the motor generates a regenerative braking force corresponding to the actual regenerative execution value, and outputs the calculated actual regenerative execution value to the brake ECU17.

In addition, the brake ECU17stores a fluid pressure braking force, which is applied to the wheels W when braking fluid pressure is supplied to a wheel cylinder WC, in a memory in a form of a map, table or calculation equation. Also, the brake ECU17stores the target regenerative braking force, which is applied to the wheels W in response to a brake operating state that is a stroke of the brake pedal (or master cylinder pressure), in the memory in a form of a map, table or calculation equation.

Additionally, the hybrid vehicle has a brake device B that directly applies the fluid pressure braking force to the respective wheels Wfl, Wfr, Wrl, Wrr and thus brakes the vehicle. As shown inFIGS. 1 and 2, the brake device B has a brake pedal11that is a brake operating member, a stroke simulator part12, a master cylinder13, a reservoir tank14, a master piston driving fluid pressure regulating device15(hereinafter, referred to as driving fluid pressure regulating device15), a braking fluid pressure regulating device16, the brake ECU17and a wheel cylinder WC.

The wheel cylinder WC regulates rotations of the wheels W, respectively and is provided in a caliper CL. When pressure of the brake fluid (brake fluid pressure) is supplied to the wheel cylinder WC from the master cylinder13, each piston (not shown) of the wheel cylinder WC presses a pair of brake pads (frictional members, not shown) to sandwich a disk rotor DR, which is a rotational member integrally rotating with the wheels W, thereby regulating rotation of the disk rotor. Meanwhile, in this illustrative embodiment, a hydraulic path of only one of the left and right front wheels is shown and the other hydraulic path having the same configuration is omitted. Further, in this illustrative embodiment, a disc-type brake is adopted. However, a drum-type brake may be adopted. The wheel W is one of the left and right front and rear wheels Wfl, Wfr, Wrl, WIT.

A pedal stroke sensor11a, which detects a brake pedal stroke (operating amount) that is a brake operating state resulting from the pedaling of the brake pedal11, is provided adjacent to the brake pedal11. The pedal stroke sensor11ais connected to the brake ECU17and a detection signal thereof is output to the brake ECU17.

The brake pedal11is connected to a stroke simulator part12through a push rod18. The stroke simulator part12has a body12a, a hole12bthat is formed in the body12a, a piston12cthat can slide liquid-tightly in the hole12b, a fluid pressure chamber12dthat is formed by the body12aand the piston12cand a stroke simulator12ethat communicates with the fluid pressure chamber12d.

The body12ais integrally connected to a body13aof the master cylinder13. A connection part12c1to which the push rod18is connected is formed at one end side of a sliding direction (axial direction) of the piston12c. A rod12fis integrally provided at the other end side of the sliding direction of the piston12c, which is opposite to the push rod18. The other end portion12f1of the rod12f, which is opposite to the push rod18, is penetrated into a partition wall12a1, which partitions the fluid pressure chamber12dof the stroke simulator part12and a driving fluid pressure chamber13eof the master cylinder13, and is supported liquid-tightly. The partition wall12a1forms a part of the body12a.

The fluid pressure chamber12dcommunicates with the reservoir tank14through a first input-output port12a2and communicates with the stroke simulator12ethrough an oil passage12gconnected to a second input-output port12a3. The stroke simulator12eis well known and generates a stroke (reaction force) having a magnitude corresponding to an operating state of the brake pedal11to the brake pedal11. The stroke simulator12ehas a piston12e2that slides liquid-tightly in a housing12e1, a fluid pressure chamber12e3that is formed between the housing12e1and the piston12e2and a spring12e4that presses the piston12e2in a direction of reducing a volume of the fluid pressure chamber12e3.

The master cylinder13is a device that forms and supplies fluid pressure (master cylinder pressure) to the wheel cylinder WC in correspondence to an operating force of the brake pedal11, which is a brake operating member, applied by a driver, and generates a fluid pressure braking force to the wheel W by the fluid pressure.

The master cylinder13is a master cylinder of a tandem-type and has the body13a. The body13ais formed with a cylinder hole13b. In the cylinder hole13b, first and second pistons13c,13dare arranged in line so that they can slide liquid-tightly.

The driving fluid pressure chamber13efor driving the first and second pistons13c,13dis formed between the first piston13cand the partition wall12a1. The other end portion12f1of the rod12freciprocatably faces the driving fluid pressure chamber13e. The partition wall12a1is formed with a step portion12a2and one end of the first piston13cis contacted to the step portion12a2. The driving fluid pressure chamber13eis adapted to secure a volume even when the first piston13cis contacted to the step portion12a2.

A first fluid pressure chamber13fthat forms a master cylinder pressure is formed between the first piston13cand the second piston13dand a second fluid pressure chamber13gthat forms a master cylinder pressure is formed between the second piston13dand a bottom wall13a1. In the first fluid pressure chamber13f, a spring13his provided which is interposed between the first piston13cand the second piston13dand presses the pistons in a direction of enlarging the first fluid pressure chamber13f. In the second fluid pressure chamber13g, a spring13iis provided which is interposed between the second piston13dand the bottom wall13a1and presses the piston in a direction of enlarging the second fluid pressure chamber13g.

When fluid pressure is not supplied to the driving fluid pressure chamber13e(for example, when the brake pedal11is not pedaled), the second piston13dis pressed by the spring13iand is thus located at a predetermined position and the first piston13cis pressed by the spring13hand is thus located at a predetermined position (refer toFIG. 2). The predetermined position of the first piston13cis a position where one end of the first piston13cis contacted to the step portion12a2and is a position just before the other end of the first piston13ccloses a port13k. The predetermined position of the second piston13dis a position just before the other end of the second piston13dcloses a port13l.

The body13aof the master cylinder13is formed with a port13jfor communicating the driving fluid pressure chamber13eand a regulator15c, a port13kfor communicating the first fluid pressure chamber13fand the reservoir tank14, a port13lfor communicating the second fluid pressure chamber13gand the reservoir tank14, a port13mfor communicating the first fluid pressure chamber13fand the wheel cylinder WC and a port13nfor communicating the second fluid pressure chamber13gand the other wheel cylinder (not shown).

The driving fluid pressure regulating device15is to regulate the pressure of the driving fluid pressure chamber13eof the master cylinder13by fluid pressures of both pressure sources, i.e., high-pressure source and low-pressure source and has a pressure supply device15a, an electrically-operated pressure regulating part15b(electrically-operated pilot pressure generating part) and the regulator15c(mechanical pressure regulating part). The driving fluid pressure regulating device15forms fluid pressure (regulator pressure) corresponding to pressure, which is applied to a pilot pressure input port21dby the fluid pressures applied to both ports, i.e., high-pressure port21band low-pressure port21c, and outputs the same to the driving fluid pressure chamber13eof the master cylinder13.

The pressure supply device15ahas the reservoir tank14, which is a low-pressure source, an accumulator15a1, which is a high-pressure source, a pump15a2, which suctions the brake fluid of the reservoir tank14and pumps the same to the accumulator15a1, and an electric motor15a3that drives the pump15a2. The reservoir tank14is opened to the atmosphere and the fluid pressure of the reservoir tank14is same as the atmospheric pressure. The low-pressure source supplies a lower pressure than the high-pressure source.

Although the reservoir tank14is commonly used as the low-pressure source of the pressure supply device15a, a separate reservoir tank may be provided. In the meantime, the pressure supply device15ahas a pressure sensor15a4that detects pressure of the brake fluid supplied from the accumulator15a1and outputs a detection signal thereof to the brake ECU17.

The electrically-operated pressure regulating part15bincludes a pressure reduction control valve15b1of a normally open type that controls the flow of the brake fluid between the reservoir tank14and the pilot pressure input port21d, a pressure boost control valve15b2of a normally close type that controls the flow of the brake fluid between the accumulator15a1and the pilot pressure input port21d, and a pressure sensor15b3that detects the fluid pressure of the driving fluid pressure chamber13e. The pressure reduction control valve15b1and the pressure boost control valve15b2are solenoid valves that are operated in response to commands from the brake ECU17. The pressure sensor15b3outputs a detection signal to the brake ECU17.

While monitoring the detection value by the pressure sensor15b3, the electrically-operated pressure regulating part15bcan supply desired pilot fluid pressure, which corresponds to the stroke amount of the brake pedal11detected by the pedal stroke sensor11aor vehicle state, to a pilot fluid pressure chamber20aby regulating the fluid pressure, which is supplied to the pilot pressure input port21dfrom the accumulator15a1, with the pressure boost control valve15b2, and regulating the discharging of the brake fluid to the reservoir tank14(fluid pressure discharged from the pilot pressure input port21dto the reservoir tank14) with the pressure reduction control valve15b1.

The regulator15cis configured by a regulator20as shown inFIG. 3. A housing21(cylinder) of the regulator20is formed with a cylinder hole21a, the high-pressure port21b, the low-pressure port21c, the pilot pressure input port21dand an output port21e. As shown inFIG. 2, the high-pressure port21bis directly connected to the accumulator15a1through a fluid pressure oil passage31. The low-pressure port21cis directly connected to the reservoir tank14through a fluid pressure oil passage32. Here, the configuration “directly connected” means that a solenoid valve or check valve is not provided on the fluid pressure oil passage.

The pilot pressure input port21dis connected with a fluid pressure oil passage33, which is branched in the middle of the fluid pressure oil passage31, and is connected to the accumulator15a1through the fluid pressure oil passage33and the fluid pressure oil passage31. In addition, a fluid pressure oil passage34that is branched in the middle of the fluid pressure oil passage32is connected to the fluid pressure oil passage33and the pilot pressure input port21dis connected to the reservoir tank14through the fluid pressure oil passage33, the fluid pressure oil passage34and the fluid pressure oil passage32. The pressure boost control valve15b2is provided on the fluid pressure oil passage33. In addition, the pressure reduction control valve15b1is provided on the fluid pressure oil passage34.

The output port21eis connected to the driving fluid pressure chamber13eof the master cylinder13through a fluid pressure oil passage35.

A pressure regulating piston22is provided in the cylinder hole21asuch that it can slide liquid-tightly. The pressure regulating piston22has a straight line shape and the pressure-receiving areas of both end surfaces thereof arc the substantially same. The pilot fluid pressure chamber20ais formed between one side end (right side end inFIG. 3) of the pressure regulating piston22and a bottom wall21a1of the cylinder hole21aand a pressure regulating chamber20bis formed at the other side end (left side end inFIG. 3) of the pressure regulating piston22. The pilot fluid pressure chamber20acommunicates with the pilot pressure input port21d, and the pressure regulating chamber20bcommunicates with the output port21e. The pressure regulating piston22is formed with a communication passage22cthat communicates with the low-pressure port21c. The pressure regulating chamber20bis provided with a spring23, so that the pressure regulating piston22is pressed in a direction of enlarging a volume of the pressure regulating chamber20b.

When the fluid pressure is not applied to the pilot fluid pressure chamber20a(for example, when the brake pedal11is not operated), the pressure regulating piston22is pressed in the right direction ofFIG. 3by the pressing force of the spring23and the right side end of the pressure regulating piston22is contacted to the bottom wall21a1and is thus position-determined. At this time, since a pressure reduction valve that will be described later is opened, the output port21ecommunicates with the low-pressure port21cthrough the pressure regulating chamber20band the communication passage22c.

A cylinder member24having a partition part24cthat partitions two holes24a,24bis fixed in the cylinder hole21a. The hole24ais opposed to the pressure regulating chamber20b, and a valve body25is slidably provided in the hole24a. A ball25ais fixed to an end portion of the valve body25facing the pressure regulating chamber20b. The ball25ais detachably provided with respect to a valve seat22dthat is formed at an end portion of the pressure regulating piston22facing the pressure regulating chamber20b. The ball25ais seated on the valve seat22dwhen the pressure regulating piston22is slid by a predetermined distance in a direction of reducing a volume of the pressure regulating chamber20b. The ball25aand the valve seat22dconfigure a pressure reduction valve and allow or cut off communication between the pressure regulating chamber20band the communication passage22c, thereby reducing the fluid pressure (regulator fluid pressure) in the pressure regulating chamber20b. The valve body25is pressed to the valve seat22dby a spring25b. The other end portion of the valve body25, which is opposite to the pressure regulating chamber20b, is integrally provided with a protrusion25chaving a small diameter. In addition, the valve body25is formed with a communication passage25dthat communicates a space formed by the hole24a, the partition part24cand the valve body25and the pressure regulating chamber20b.

A ball-shaped valve body26is movably provided in the hole24bof the cylinder member24and is detachably provided with regard to a valve seat24c2of a valve hole24c1that is formed in the partition part24c. The valve hole24c1is configured so that the protrusion25cof the valve body25can advance and retreat, and an inner diameter of the valve hole24c1is formed to be larger than an outer diameter of the protrusion25c. The valve body26is pressed toward the valve seat24c2by a spring26a. In a normal state, the valve body26is pressed and thus seated on the valve seat24c2. When the valve body25slides in the left direction ofFIG. 3, the valve body26is pressed by the protrusion25cof the valve body25and is thus detached from the valve seat24c2. The cylinder member24is formed with a communication passage24dthat communicates the hole24bwith the high-pressure port21b. The valve body26, the valve seat24c2and the spring26aconfigure a pressure boost valve, which cooperates with the pressure reduction valve to allow or cut off communicate between the pressure regulating chamber20band the communication passage24d, thereby boosting the fluid pressure (regulator fluid pressure) in the pressure regulating chamber20b. In the meantime, the hole24bis plugged by a stopper27and the cylinder member24is fixed by a nut28.

In the meantime, a flow path sectional area in the regulator20is set to be larger than those of the control valves15b1,15b2.

The operations of the regulator20configured as described above will be described with reference toFIG. 3. When the pilot fluid pressure chamber20ais pressure-boosted and a force (=pressure pressure-receiving area) applied to one side end of the pressure regulating piston22facing the pilot fluid pressure chamber20abecomes thus greater than a total sum of a force (=pressure pressure-receiving area) applied to the other side end of the pressure regulating piston22facing the pilot fluid pressure chamber20band the pressing force by the spring23, the pressure regulating piston22is moved leftwards. In addition, when the pressure regulating piston22is moved leftwards, the valve seat22dis contacted to the ball25a, so that the pressure reduction valve is closed. Also, when the pressure regulating piston22is moved leftwards, the pressure regulating piston22is moved against the pressing force of the spring25band the valve body25is thus moved leftwards. When the valve body25is further moved leftwards, the protrusion25cis contacted to the valve body26, and the valve body26is then moved leftwards against the pressing force of the spring26aand a valve closing force (=pressure pressure-receiving area) of the valve body26, so that the pressure boost valve is opened.

When the pressure boost valve is opened, the fluid pressure of high pressure from the accumulator15a1is supplied to the pressure regulating chamber20bvia the high-pressure port21b, the communication passage24d, the valve hole24c1and the communication passage25d. When the fluid pressure in the pressure regulating chamber20bis increased and the force applied to the one side end of the pressure regulating piston22becomes thus smaller than the total sum of the force applied to the other side end of the pressure regulating piston22and the pressing force of the spring23, the pressure regulating piston22is moved rightwards. Then, the pressure boost valve is closed and the valve body25is contacted to a regulating member24e, so that the pressure reduction valve is opened. Thereby, the pressure regulating chamber20bis enabled to communicate with the low-pressure port21cthrough the communication passage21c, so that the fluid pressure in the pressure regulating chamber20bis lowered.

When the fluid pressure in the pressure regulating chamber20bis lowered and the force applied to the one side end of the pressure regulating piston22becomes thus greater than the total sum of the force applied to the other side end of the pressure regulating piston22and the pressing force of the spring23, the pressure regulating piston22is again moved leftwards. Like this, as the pressure regulating piston22is repeatedly moved leftwards and rightwards, the regulator20can output the fluid pressure corresponding to the fluid pressure, which is supplied to the pilot fluid pressure chamber20a, from the output port21eby the pressure applied to both of the high-pressure port21band the low-pressure port21c.

As shown inFIG. 2, the braking fluid pressure regulating device16has a holding valve16a, a pressure reduction valve16b, a reservoir tank16c, a pump16dand an electric motor16e. The holding valve16ais a solenoid opening and closing valve of a normally open type that is provided between the port13mof the master cylinder13and the wheel cylinder WC and allows or cuts off communication between the master cylinder13and the wheel cylinder WC. The holding valve16ais configured as a two-position valve that can control the master cylinder and the wheel cylinder into the communication state (which is shown) under off-state and the master cylinder and the wheel cylinder into the cut-off state under on-state, in response to commands from the brake ECU17. A check valve16fthat permits the flow from the wheel cylinder WC to the master cylinder13and regulates the flow of a reverse direction thereof is provided in parallel with the holding valve16a.

The pressure reduction valve16bis a solenoid opening and closing valve of a normally close type that allows or cuts off communication between the wheel cylinder WC and the reservoir tank16c. The pressure reduction valve16bis configured as a two-position valve that can control the wheel cylinder and the reservoir tank into the cut off state (which is shown) under off-state and the wheel cylinder and the reservoir tank into the communication state under on-state, in response to commands from the brake ECU17.

The reservoir tank16cstores the brake fluid and communicates with the port13mof the master cylinder13. The pump16dis provided between the reservoir tank16cand the master cylinder13. The pump16dhas a suction port that communicates with the reservoir tank16cand an ejection port that communicates between the master cylinder13and the holding valve16athrough a check valve16g. The check valve16gis a check valve that permits the flow from the pump16dto the master cylinder13and regulates the flow of a reverse direction thereof. The pump16dis driven as the electric motor16eis operated in response to the command from the brake ECU17. The pump16dsuctions the brake fluid stored in the wheel cylinder WC or brake fluid stored in the reservoir tank16cand returns the same to the master cylinder13, under pressure reduction mode of ABS control. In order to alleviate pulsation of the brake fluid ejected from the pump16d, a damper16his provided upstream of the pump16d.

The braking fluid pressure regulating device16has a wheel speed sensor16ithat is provided adjacent to the wheel W and detects wheel speed of the wheel W. A detection signal indicating the wheel speed detected by the wheel speed sensor16iis output to the brake ECU17.

In the braking fluid pressure regulating device16configured as described above, the brake ECU17performs ABS control (anti lock brake control) of switching the opening and closing of the respective solenoid valves16a,16b, based on the master cylinder pressure, the wheel speed and the longitudinal acceleration, and operating the electric motor16e, as required, to adjust the brake fluid pressure applied to the wheel cylinder WC, i.e., the braking force applied to the wheel W.

According to the above illustrative embodiment, by controlling the pressure boost control valve15b2and the pressure reduction control valve15b1of the electrically-operated pilot pressure generating part15b, the desired pilot fluid pressure is generated in correspondence to the operating amount of the brake pedal11(brake operating member) or vehicle state and is then input to the pilot pressure input port21dof the regulator15c(mechanical pressure regulating part). Thereby, the fluid pressure corresponding to the output fluid pressure of the electrically-operated pilot pressure generating part15bapplied to the pilot pressure input port21dof the regulator15cis output from the output port21e. Like this, the pressure boost control valve15b2and the pressure reduction control valve15b1having the relatively low flow rate per unit time are used to generate the pilot fluid pressure that can sufficiently exhibit a function even though the flow rate thereof is low, thereby controlling the regulator15ccapable of outputting a relatively high flow rate (per unit time). Accordingly, it is possible to provide a brake device capable of providing sufficient braking force in good responsiveness to sudden braking without causing the enlargement of the device and the increase of cost.

(2) Second Illustrative Embodiment

Next, the brake device according to a second illustrative embodiment of the present invention is described with reference toFIGS. 4 and 5.FIG. 4is an outline view showing a configuration of the brake device B, andFIG. 5is a sectional view showing a regulator120. The second illustrative embodiment is different from the first illustrative embodiment, in that the regulator120is operated by inputting pilot fluid pressures of two types from separate pilot pressure input ports. The same configurations are indicated with the same reference numerals and the descriptions thereof are omitted.

Specifically, a second pressure regulating piston29is provided liquid-tightly and slidably between the pressure regulating piston22(first pressure regulating piston) and the bottom wall21a1. The second pressure regulating piston29is a piston that partitions neighboring pilot fluid pressure chambers20a,20cof a plurality of pilot fluid pressure chambers20a,20cand slides in the cylinder hole21a. Specifically, the pilot fluid pressure chamber20a(first pilot fluid pressure chamber) is formed between the second pressure regulating piston29and the bottom wall21a1. The second pilot fluid pressure chamber20cis formed between the second pressure regulating piston29and the first pressure regulating piston22. The second pilot fluid pressure chamber20ccommunicates with a pilot pressure input port21f. The pilot pressure input port21fis connected to the oil passage12gthrough a fluid pressure oil passage36.

In other words, the pilot pressure input port21dis connected with the reservoir tank14(low-pressure source) through the pressure reduction control valve15b1and with the accumulator15a1(high-pressure source) through the pressure boost control valve15b2. The pilot fluid pressures, which are generated as the pressure reduction control valve15b1and the pressure boost control valve15b2are operated, are applied to the pilot pressure input port21d.

In the meantime, the pilot pressure input port21fdifferent from the pilot pressure input port21dis connected with the stroke simulator part12that is the mechanical pilot pressure generating part to generate the pilot fluid pressure corresponding to the operating amount of the brake pedal11. The pilot fluid pressure generated in the stroke simulator part12is applied to the pilot pressure input port21f.

That is, the regulator15ehas the plurality of pilot pressure input ports21d,21fand outputs the fluid pressure, which corresponds to the highest fluid pressure of the fluid pressures applied to the pilot pressure input ports21d,21f, to the output port21e. Specifically, when the pressure reduction control valve15b1and the pressure boost control valve15b2are operated without the failure of the electric system, the fluid pressure that is supplied from the pressure reduction control valve15b1and the pressure boost control valve15b2to the input port21dis set to have a pressure value higher than the fluid pressure that is supplied from the stroke simulator part12to the pilot pressure input port21f. Thereby, the pedaling force of the brake pedal11is increased in a predetermined ratio.

Accordingly, when the pilot fluid pressure is supplied from the pressure reduction control valve15b1and the pressure boost control valve15b2to the first pilot fluid pressure chamber20athrough the pilot pressure input port21d, the second and first pressure regulating pistons29,22are pressed against the pressing force of the spring23. At this time, the first pressure regulating piston22is pressed by the resultant force of the force, which is applied to the end surface of the first pressure regulating piston22facing the second pilot fluid pressure chamber20cby the pilot fluid pressure supplied to the second pilot fluid pressure chamber20c, and the force, which is directly applied from the second pressure regulating piston22being contacted. In the meantime, since the pressure-receiving areas of both end surfaces of the second pressure regulating piston29are the substantially same, the force that is directly applied from the second pressure regulating piston22is the same as the force that the first pressure regulating piston22is applied at the end surface facing the first pilot fluid pressure chamber20aby the pilot fluid pressure supplied to the first pilot fluid pressure chamber20a. In addition, the pressure-receiving areas of both end surfaces of the second pressure regulating piston29are the substantially same and the pressure received at the end surface of the second pressure regulating piston20facing the second pilot fluid pressure chamber20cis smaller than the pressure received at the opposite side thereof. Accordingly, even when the pilot fluid pressure is supplied from the stroke simulator part12, the second pressure regulating piston29is not returned toward the bottom wall21a1.

Therefore, the regulator15cforms the regulator pressure corresponding to the pilot fluid pressure supplied to the first and second pilot fluid pressure chambers20a,20cand outputs the same to the driving fluid pressure chamber13eof the master cylinder13.

In the meantime, when the pressure reduction control valve15b1and the pressure boost control valve15b2cannot operate due to the failure of the electric system and the like, the pilot fluid pressure is not supplied from the pressure reduction control valve15b1and the pressure boost control valve15b2to the first pilot fluid pressure chamber20athrough the pilot pressure input port21d. However, the pilot fluid pressure is supplied from the stroke simulator part12to the second pilot fluid pressure chamber20cthrough the pilot pressure input port21f. At this time, the regulator15cforms the regulator pressure corresponding to the pilot fluid pressure supplied to the second pilot fluid pressure chamber20conly and outputs the same to the driving fluid pressure chamber13eof the master cylinder13.

According to the second illustrative embodiment, the regulator15c(mechanical pressure regulating part) outputs the fluid pressure, which corresponds to the highest fluid pressure of the fluid pressures applied to the pilot pressure input ports21d,21f, to the output port21e, and the stroke simulator part12(mechanical pilot pressure generating part) is connected to the pilot pressure input port21fthat is different from the port21dof the plurality of pilot pressure input ports21d,21fto which the electrically-operated pilot pressure generating part15bis connected.

Therefore, it is possible not only to apply the output fluid pressure of the electrically-operated pilot pressure generating part15bto the pilot pressure input port21dof the regulator15cbut also to apply the output fluid pressure of the separately provided stroke simulator part12to the pilot pressure input port21fof the regulator15c.

In addition, the pressure boost control valve15b2of the electrically-operated pilot pressure generating part15bis a control valve of a normally close type, the pressure reduction control valve15b1of the electrically-operated pilot pressure generating part15bis a control valve of a normally open type, and the regulator15coutputs the fluid pressure corresponding to the highest fluid pressure of the fluid pressures applied to the plurality of pilot pressure input ports21d,21f.

Accordingly, under off-state resulting from the failure of the electric system, the pressure boost control valve15b2of the electrically-operated pilot pressure generating part15bis closed and the pressure reduction control valve15b1thereof is opened, so that the fluid pressure of the low-pressure source14is output, and the fluid pressure corresponding to the fluid pressure of the stroke simulator part12is output from the output port21eof the regulator15c. Like this, even when the electric system fails, the fluid pressure of the stroke simulator part12is applied to the pilot pressure input port21fof the regulator15cand the fluid pressure corresponding to the applied fluid pressure is applied to the driving fluid pressure chamber13e, so that it is possible to generate the braking force corresponding to the operating amount of the brake pedal11inasmuch as the fluid pressure remains in the accumulator15a1(high-pressure source).

In addition, the regulator15chas the cylinder21, the plurality of pistons22,29(two pistons in this illustrative embodiment), which slide in the cylinder21, and the plurality of pilot fluid pressure chambers20a,20c, which are formed by the cylinder21and the plurality of pistons22,29and communicate with the plurality of pilot pressure input ports21d,21f, respectively. The stroke simulator part12(mechanical pilot pressure generating part) is connected to the pilot pressure input port21fthat communicates with the pilot fluid pressure chamber20cthat is formed by the piston22driven by the output fluid pressure of the stroke simulator part12. The electrically-operated pilot pressure generating part15bis connected to the pilot pressure input port21dthat communicates with the pilot fluid pressure chamber20a, which is a fluid pressure chamber that is formed by the piston29driven by the output fluid pressure of the electrically-operated pilot pressure generating part15b, different from the piston22driven by the output fluid pressure of the stroke simulator part12, and which is different from the pilot fluid pressure chamber20cthat is formed by the piston22driven by the output fluid pressure of the stroke simulator part12. The piston22driven by the output fluid pressure of the stroke simulator part12is also driven by the pressing force of the piston29that is driven by the output fluid pressure of the electrically-operated pilot pressure generating part15b.

Thereby, it is possible to hold the sliding resistance of the piston22small, which is driven by the output fluid pressure of the stroke simulator part12, and to thus prevent the fixation of the piston22. Accordingly, it is possible to surely generate the braking force corresponding to the operating amount of the brake pedal11even when the electric system fails.

Additionally, in the second illustrative embodiment, the first pressure regulating piston22having the substantially same pressure-receiving areas on both left and right end surfaces may be replaced with a first pressure regulating piston122having different pressure-receiving areas on left and right end surfaces. As shown inFIG. 6, the first pressure regulating piston122has a large diameter part122aand a small diameter part122bhaving a diameter smaller than the large diameter part122a, which are integrally formed. The large diameter part122afaces the second pilot fluid pressure chamber20cand the small diameter part122bfaces the pressure regulating chamber20b. Accordingly, when the pressure reduction control valve15b1and the pressure boost control valve15b2are not operated due to the failure of the electric system and the like, it is possible to output the regulator pressure of a predetermined ratio (pressure-receiving area ratio) with respect to the fluid pressure that is supplied from the stroke simulator12to the second pilot fluid pressure chamber20c. In other words, the pedaling force of the brake pedal11is increased in a predetermined ratio.

In addition, the respective pressure-receiving areas on the end surface of the large diameter part122aof the first pressure regulating piston122and the end surface of the small diameter part122bare set such that the regulator15ccan output the fluid pressure corresponding to the pressure applied to the pilot pressure input port21dfrom the output port21eby the fluid pressures applied to both the high-pressure port21band the low-pressure port21c.

In the second illustrative embodiment, two pistons are provided as the plurality of pistons22,29that slides in the cylinder21. However, three or more pistons may be provided.

(3) Third Illustrative Embodiment

Next, the brake device according to a third illustrative embodiment of the present invention is described with reference toFIGS. 7 and 8.FIG. 7is an outline view showing a configuration of the brake device B, andFIG. 8is a sectional view showing a regulator220. The third illustrative embodiment is different from the second illustrative embodiment, in that the pilot fluid pressures to be supplied to the two neighboring pilot fluid pressure chambers20a,20care configured to be opposite to the second illustrative embodiment. The same configurations are indicated with the same reference numerals and the descriptions thereof are omitted.

Specifically, the pilot fluid pressure chamber20a(first pilot fluid pressure chamber) formed between the second pressure regulating piston29and the bottom wall21a1communicates with the pilot pressure input port21f. In addition, the second pilot fluid pressure chamber20cformed between the second pressure regulating piston29and the first pressure regulating piston22communicates with the pilot pressure input port21d.

In other words, the second pilot fluid pressure chamber20cis connected with the reservoir tank14(low-pressure source) through the pilot pressure input port21dand the pressure reduction control valve15b1and with the accumulator15a1(high-pressure source) through the pressure boost control valve15b2. The pilot fluid pressures, which are generated as the pressure reduction control valve15b1and the pressure boost control valve15b2are operated, are applied to the pilot pressure input port21d(second pilot fluid pressure chamber21c).

In the meantime, the first pilot fluid pressure chamber20ais connected with the stroke simulator part12, which is a mechanical pilot pressure generating part that generates the pilot fluid pressure corresponding to the operating amount to the brake pedal11, through the pilot pressure input port21fdifferent from the pilot pressure input port21d. The pilot fluid pressure that is generated in the stroke simulator part12is applied to the pilot pressure input port21f(first pilot fluid pressure chamber20a).

In this case, when the pressure reduction control valve15b1and the pressure boost control valve15b2are operated without the failure of the electric system and the like, the fluid pressure that is supplied from the pressure reduction control valve15b1and the pressure boost control valve15b2is basically set to have a pressure value higher than the fluid pressure that is supplied from the stroke simulator part12to the pilot pressure input port21f. At this time, accordingly, it is possible to operate the regulator15cby operating only the first pressure regulating piston22without the operating (moving) the second pressure regulating piston29. In the meantime, when the electric system fails, it is possible to operate the regulator15cby operating the second and first pressure regulating pistons29,22only with the fluid pressure that is supplied from the stroke simulator part12to the pilot pressure input port21f.

Next, the brake device according to a fourth illustrative embodiment of the present invention is described with reference toFIG. 9.FIG. 9is an outline view showing a configuration of the brake device B. The fourth illustrative embodiment is different from the second illustrative embodiment, in that a pilot pressure control valve41is provided. The same configurations are indicated with the same reference numerals and the descriptions thereof are omitted.

Specifically, the pilot pressure control valve41is a solenoid control valve of a normally open type that is provided on fluid pressure oil passage36and controls the flow of the brake fluid between the stroke simulator part12(mechanical pilot pressure generating part) and the pilot pressure input port21f. The pilot pressure control valve41is opened and closed based on the command from the brake ECU17.

The operations of the fourth illustrative embodiment will be described. When the electric system fails, the pilot pressure control valve41of a normally open type is opened and the fluid pressure chamber12dof the stroke simulator part12and the pilot pressure input port21fcommunicate with each other. At this time, similarly to the second illustrative embodiment, insofar as the high pressure is supplied from the accumulator15a1, the regulator15c(mechanical pressure regulating part) outputs the fluid pressure corresponding to the pressure applied to the pilot pressure input port21ffrom the output port21eby the fluid pressures applied to both of the high-pressure port21band the low-pressure port21c.

In addition, the brake ECU17(control unit) closes the pilot pressure control valve41when regeneration is requested at the state where the failure of the electric system does not occur. Since the pilot pressure control valve41is closed, the pilot pressure input port21fof the regulator15c(mechanical pressure regulating part) is not applied with the output fluid pressure corresponding to the operating amount of the brake operating member of the stroke simulator part12(mechanical pilot pressure generating part) and is applied with only the pilot fluid pressure generated by the electrically-operated pilot pressure generating part15b. Thus, it is possible to perform a desired regenerative braking by generating the pilot fluid pressure corresponding to the regeneration request with the electrically-operated pilot pressure generating part15b. In the meantime, as described above, since the regeneration request value is set with respect to the braking request of the driver, i.e., the braking operation state, the brake ECU17sets the regeneration request corresponding to the operating amount that is detected based on the pedal stroke sensor11a. Accordingly, the brake ECU17serves as a vehicle state detection unit that detects the regeneration request.

In addition, under anti lock brake control at the state where the failure of the electric system does not occur, the brake ECU17(control unit) opens the pilot pressure control valve41. Since the pilot pressure control valve41is opened, the pilot pressure input port21fof the regulator15c(mechanical pressure regulating part) is applied with the output fluid pressure of the stroke simulator part12and the pilot pressure input port21dis applied with the output fluid pressure of the electrically-operated pilot pressure generating part15b. Thus, even when the brake fluid of high flow rate is necessary for the anti lock brake control, it is possible to sufficiently cope with the situation because it is possible to generate the pilot fluid pressure in good responsiveness by both pilot pressure generating parts of the stroke simulator part12and the electrically-operated pilot pressure generating part15b. In the meantime, as described above, the brake ECU17performs ABS control (anti lock brake control) of switching the opening and closing of the respective solenoid valves16a,16b, based on the master cylinder pressure, the wheel speed and the longitudinal acceleration, and operating the electric motor16e, as required, to adjust the brake fluid pressure applied to the wheel cylinder WC, i.e., the braking force applied to the wheel W. Accordingly, the brake ECU17serves as a vehicle state detection unit that detects the anti lock brake control state.

That is, when the electric system normally operates, the brake ECU17, which is the control unit, controls the flow of the brake fluid between the stroke simulator part12(mechanical pilot pressure generating part) and the pilot pressure input port21fby the pilot pressure control valve41in response to the vehicle state that is detected by the brake ECU17that is the vehicle state detection unit, thereby appropriately adjusting a ratio of the fluid pressure corresponding to the operating amount of the brake pedal11, which occupies in the fluid pressure output from the regulator15c(mechanical pressure regulating part), in response to the vehicle state. In the meantime, the vehicle state includes an on-state or off state of an ignition switch. When the ignition switch is on, the control of the pilot pressure control valve resulting from a detection result of the vehicle state includes the control of closing the pilot pressure control valve all the time inasmuch as the failure of the electric system does not occur.

In addition, the pilot pressure control valve41is a control valve of a normally open type. Accordingly, even when the electric system fails, it is possible to output the fluid pressure corresponding to the pilot pressure of the stroke simulator part12to the output port21e, thereby driving the master piston13c.

Further, in the above illustrative embodiment, the stroke simulator part12(mechanical pilot pressure generating part) has the piston12cthat is interlockingly operated with the brake pedal11(brake operating member), the body12a(cylinder) in which the piston12cslides, the fluid pressure chamber12dthat is formed by the piston12cand the cylinder12aand the stroke simulator12ethat is connected to the fluid pressure chamber12d, and generates fluid pressure of the fluid pressure chamber12das the pilot fluid pressure. Thereby, it is possible to appropriately generate the pilot fluid pressure corresponding to the operating amount of the brake pedal11with a simple configuration.

Next, the brake device according to a fifth illustrative embodiment of the present invention is described with reference toFIG. 10.FIG. 10is an outline view showing a configuration of the brake device B. The fifth illustrative embodiment is different from the third illustrative embodiment, in that the pilot pressure control valve41is provided. The same configurations are indicated with the same reference numerals and the descriptions thereof are omitted.

Specifically, the pilot pressure control valve41is a solenoid control valve of a normally open type that is provided on the fluid pressure oil passage36and controls the flow of the brake fluid between the stroke simulator part12(mechanical pilot pressure generating part) and the pilot pressure input port21f. The pilot pressure control valve41is opened and closed based on the command from the brake ECU17.

The operations of the fifth illustrative embodiment are the same as those of the fourth illustrative embodiment. Thus, the descriptions thereof are omitted.

Next, the brake device according to a sixth illustrative embodiment of the present invention is described with reference toFIGS. 11 and 12.FIG. 11is an outline view showing a configuration of the brake device B, andFIG. 12is a sectional view showing a regulator320. The sixth illustrative embodiment is different from the fifth illustrative embodiment, in that the first fluid pressure chamber13fof the master cylinder13is adopted as the mechanical pilot pressure generating part. The same configurations are indicated with the same reference numerals and the descriptions thereof are omitted.

Specifically, the mechanical pilot pressure generating part of the sixth illustrative embodiment has the first piston13cthat is a master piston and the master cylinder13in which the master piston13cslides. The fluid pressure of the first fluid pressure chamber13f, which is a master chamber formed by the master piston13cand the master cylinder13, is generated as the pilot fluid pressure. The fluid pressure oil passage36connects the pilot pressure input port21fand the port13m. Thereby, it is possible to use the configuration of the existing master cylinder without adopting a special configuration for generating the pilot fluid pressure, so that it is possible to make the device small and at low cost. In the meantime, the second fluid pressure chamber13gof the master cylinder13may be adopted as the mechanical pilot pressure generating part. Further, the pilot pressure control valve41is provided on the fluid pressure oil passage36.

In this case, it is preferable to adopt a regulator320shown inFIG. 12, as the regulator15c. The regulator320is different from the regulator220, in that a second pressure regulating piston129has a diameter smaller than the second pressure regulating piston29of the third illustrative embodiment. The other configurations are the same and are indicated with the same reference numerals and the descriptions thereof are omitted.

In the regulator320, the fluid pressure of the pilot fluid pressure chamber20aand the fluid pressure of the first fluid pressure chamber13fare the same and the fluid pressure of the pressure regulating chamber20band the fluid pressure of the driving fluid pressure chamber13eare the same. In addition, the regulator320is configured such that the fluid pressure of the driving fluid pressure chamber13einfluencing the first piston13cin the left direction of the drawing is smaller than the fluid pressure of the first fluid pressure chamber13finfluencing the first piston13cin the right direction of the drawing. In the meantime, in this case, the pressure-receiving areas of both end surfaces of the first piston13care the substantially same. In addition, even when the pressure-receiving areas of both end surfaces of the first piston13care different, the regulator320is preferably configured such that the fluid pressure of the driving fluid pressure chamber13einfluencing the first piston13cin the left direction of the drawing is smaller than the fluid pressure of the first fluid pressure chamber13finfluencing the first piston13cin the right direction of the drawing.

The operations of the sixth illustrative embodiment will be described. When the pressure boost control valve15b2and the pressure reduction control valve15b1are under off-state due to the failure of the electric system and the like, the pressure reduction control valve15b1of a normally open type is opened and the pressure boost control valve15b2of a normally close type is closed at the off-state. Accordingly, the pilot fluid pressure is not supplied to the second pilot fluid pressure chamber20c. The pilot pressure control valve41provided on the fluid pressure oil passage36is opened. Thereby, even when the electric motor15a2cannot operate under off-state, the pressure from the accumulator15a1is supplied to the high-pressure port21band the pressure from the reservoir tank14(low-pressure source) is supplied to the low-pressure port21, insofar as the high pressure remains in the accumulator15a1.

When the brake pedal11(brake operating member) is operated, the rod12fdirectly presses the first piston13c, before the regulator15cstarts to supply the regulator pressure, so that the master cylinder pressure is formed in the first fluid pressure chamber13f. When the master cylinder pressure is supplied from the first fluid pressure chamber13f, the master cylinder pressure (pilot fluid pressure) corresponding to the operating amount of the brake pedal11is input to the pilot pressure input port21f. Therefore, the regulator15coutputs the fluid pressure (regulator pressure) corresponding to the master cylinder pressure from the output port21e. Thus, inasmuch as the high pressure is supplied from the accumulator15a1, the regulator15ccan supply the fluid pressure having a regulated pressure to the driving fluid pressure chamber13eand can suppress the lowering of the braking force.

In the meantime, when failure of the electric system does not occur and the electric motor15a2, the pressure boost control valve15b2and the pressure reduction control valve15b1normally operate, the master cylinder pressure (pilot fluid pressure) corresponding to the operating amount of the brake pedal11is input to the pilot pressure input port21dby the operations of the pressure boost control valve15b2and the pressure reduction control valve15b1, before the regulator15cstarts to supply the regulator pressure. In addition, since the regulator15coperates as described above, it is possible to perform the pressure regulation by the regulator15cand the pressure regulation by the operations of the pressure boost control valve15b2and the pressure reduction control valve15b1.

In the sixth illustrative embodiment, the pilot pressure control valve41may be omitted and the pilot fluid pressures that are input to the pilot pressure input ports20a,20cmay be the same as the fourth illustrative embodiment.

In the respective illustrative embodiments, it has been described that the invention is applied to the brake device mounted on the hybrid vehicle. However, the present invention may be applied to a brake device of a vehicle to which only an engine is mounted.

In addition, the present invention can be applied to a brake device capable of performing ESC control as well as the brake device capable of performing the ABS control. The brake device capable of performing ESC control has such a configuration that a differential pressure control valve is provided between the master cylinder13and the braking fluid pressure regulating device16in the first illustrative embodiment.

In the respective illustrative embodiments, regarding the regulator15c, the other configuration may be adopted insofar as it is a mechanical pressure regulating part.

In the respective illustrative embodiments, the spring may be replaced with the other press member (for example, press member made of rubber) inasmuch as the press member can press.