Vehicular braking device

A vehicular braking device can shorten the time between pilot pressure input to a regulator and generation of servo pressure, and reduce product-by-product time variations for servo pressure generation. This vehicular braking device comprises: a servo pressure rising start time measurement unit that measures, in advance, a servo pressure rising start time which is the time from pilot pressure input to a first pilot chamber by opening a pressure increase valve to when a servo pressure starts to rise, and stores the servo pressure rising start time in a storage unit; a pilot pressure increase time calculation unit that calculates a pilot pressure increase time based on the servo pressure rising start time stored in advance in the storage unit; and a pre-fill control unit that increases the pilot pressure for the pilot pressure increase time by opening the pressure increase valve when brake pedal operation is detected.

TECHNICAL FIELD

The present invention relates to a vehicular braking device for applying a friction braking force to a vehicle.

BACKGROUND ART

Examples of a vehicular braking device for applying a friction braking force to a vehicle includes a vehicular braking device described in Patent document 1. In the vehicular braking device, a pressure control valve in a regulator is subjected to a pilot pressure generated through an accumulator and an electromagnetic valve and slides in the regulator, thereby regulating an accumulator pressure to generate a servo pressure. The servo pressure thus generated is inputted to a servo chamber in a master cylinder, thereby feeding a brake fluid from a master cylinder to a wheel cylinder of a friction braking device to generate a friction braking force in the friction braking device.

PRIOR ART DOCUMENT

Patent Document

Japanese Translation of PCT International Application Publication No. 2009-507714

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

While the pilot pressure is generated by the action of the electromagnetic valve, causing no substantial time lag, the servo pressure is generated by the mechanical action that is sliding of the pressure control valve in the regulator, causing a time lag between inputting of the pilot pressure to the regulator and actual generation of the servo pressure. Moreover, due to manufacturing variations in the regulator, the time lag between inputting of the pilot pressure to the regulator and actual generation of the servo pressure varies among products of the regulator.

The present invention is devised in consideration of such circumstances, and its object is to provide a vehicular braking device that can shorten the time between inputting of the pilot pressure to a regulator to generation of the servo pressure; and that can reduce product-by-product variations in the time for generating the servo pressure.

Means for Solving the Problems

To attain the above object, according to a first aspect of the invention, a vehicular braking device includes a master cylinder connected to a wheel cylinder of a friction brake device for applying a braking force to a wheel of a vehicle, the master cylinder supplying a brake fluid to the wheel cylinder; an output piston slidably disposed in the master cylinder, the output piston being driven by a servo pressure that is a fluid pressure in a servo chamber delimited by the master cylinder to change the volume of a master chamber filled with the brake fluid supplied to the wheel cylinder; a regulator that allows the servo pressure corresponding to a pilot pressure that is a fluid pressure in a partitioned pilot chamber to generate in the servo chamber, on the basis of the fluid pressure of the brake fluid accumulated in the accumulator; an electromagnetic valve that adjusts a flow of the brake fluid from the accumulator to the pilot chamber; a braking force generation determination unit that determines a level of probability of generation of the braking force in the friction brake device; a storage unit that stores a servo pressure rising start time that is a time from when the pilot pressure is a value equivalent to an atmospheric pressure to when the servo pressure starts to rise by inputting the brake fluid from the accumulator into the pilot chamber by means of the electromagnetic valve, or a setting time set based on the servo pressure rising start time; a pre-fill control unit that performs pre-fill control to open the electromagnetic valve and input the brake fluid from the accumulator into the pilot chamber for the servo pressure rising start time or the setting time stored in the storage unit, when the braking force generation determination unit determines that the probability of generation of the braking force in the friction brake device is high.

As described above, the storage unit stores the servo pressure rising start time that is a time from when the pilot pressure is the value equivalent to the atmospheric pressure to when the servo pressure starts to rise by inputting the brake fluid from the accumulator into the pilot chamber by means of the electromagnetic valve, or the setting time set based on the servo pressure rising start time. The pre-fill control unit performs pre-fill control to open the electromagnetic valve and input the brake fluid from the accumulator into the pilot chamber for the servo pressure rising start time or the setting time stored in the storage unit, when the braking force generation determination unit determines that the probability of generation of the braking force in the friction brake device is high. Accordingly, when the probability of generation of the braking force in the friction brake device is determined to be high, the brake fluid flows from the accumulator into the pilot chamber for the servo pressure rising start time or the time based on the setting time stored in the storage unit, increasing the pilot pressure. This shortens the time from inputting of the pilot pressure to the regulator to generation of the servo pressure. That is, conventionally, for generating the braking force in the friction brake device by generating the servo pressure, a time lag has occurred in the servo pressure generated by the mechanical action in the regulator. However, according to the present invention, since the pilot pressure increases until the servo pressure occurs, the time required to generate the servo pressure is shortened. Further, since the pilot pressure increases for the time based on the servo pressure rising start time measured by opening the electromagnetic valve in advance, product-by-product variations in the time for generating the master pressure are reduced.

According to a second aspect of the invention, in the first aspect of the invention, the storage unit stores a full-open rising start time, as the servo pressure rising start time, which is a time from when the pilot pressure is the value equivalent to the atmospheric pressure to when the electromagnetic valve is fully opened to input the brake fluid from the accumulator to the pilot chamber and the servo pressure starts to rise, or stores, as the setting time, time set based on the full-open rising start time, and in the pre-fill control, the pre-fill control unit fully opens the electromagnetic valve for the full-open rising start time or the setting time, that is stored in the storage unit.

The flow rate of the brake fluid flowing from the electromagnetic valve in a degree of opening from 0 to full varies among products of the electromagnetic valve. Meanwhile, the flow rate of the brake fluid flowing from the fully-opened electromagnetic valve has less variations in products of the electromagnetic valve. As described above, the storage unit stores, as a servo pressure rising start time, the full-open rising start time in the state where the electromagnetic valve is fully opened. Thus, since variations in the flow rate of the brake fluid flowing from the fully-opened electromagnetic valve are small, variations in the servo pressure rising start time among products of the electromagnetic valves are small. In the pre-fill control, the pre-fill control unit fully opens the electromagnetic valve for the full-open rising start time or the setting time, which is stored in the storage unit. Thus, at full-opening of the electromagnetic valve, the flow rate of the brake fluid does not vary among products of the manufactured electromagnetic valve. This can prevent a lag of the servo pressure, and an excessive servo pressure that is not based on the operating amount of a brake operating member, due to variations in the flow rate of the brake fluid among products of the electromagnetic valve.

According to a third aspect of the invention, in the first or second aspect of the invention, the vehicular braking device further includes an accumulator pressure detection unit that detects an accumulator pressure that is the fluid pressure of the brake fluid stored in the accumulator; and a pressure time correction unit that corrects the servo pressure rising start time or the setting time stored in the storage unit on the basis of the accumulator pressure detected by the accumulator pressure detection unit, and in the pre-fill control, the pre-fill control unit opens the electromagnetic valve for the servo pressure rising start time or the setting time corrected by the pressure time correction unit.

As described above, the pressure time correction unit corrects the servo pressure rising start time or the setting time stored in the storage unit on the basis of the accumulator pressure detected by the accumulator pressure detection unit. This can prevent a lag of the servo pressure, and an excessive servo pressure that is not based on the operating amount of a brake operating member, due to variations in the accumulator pressure in the pre-fill control. As the accumulator pressure decreases, the pilot pressure generated by the electromagnetic valve also decreases, further delaying generation of the servo pressure caused by the mechanical action in the regulator. Thus, the pressure time correction unit corrects servo pressure rising start time or the setting time so as to be longer as the accumulator pressure decreases, preventing the lag of generation of the servo pressure. Further, as the accumulator pressure increases, the pilot pressure caused by the electromagnetic valve also increases, promoting generation of the servo pressure caused by the mechanical action in the regulator. The pressure time correction unit corrects the servo pressure rising start time or the setting time so as to be shorter as the accumulator pressure increases, preventing generation of an excessive servo pressure that is not based on the operating amount of the brake operating member, which is caused by inputting of the pilot pressure increased after generation of the servo pressure into the pilot chamber.

According to a fourth aspect of the invention, in any of the first to third aspects of the invention, the vehicular braking device further includes a temperature detection unit that detects the brake fluid temperature; and a temperature time correction unit that corrects the servo pressure rising start time or the setting time stored in the storage unit on the basis of the brake fluid temperature detected by the temperature detection unit, and in the pre-fill control, the pre-fill control unit opens the electromagnetic valve for the servo pressure rising start time or the setting time that is corrected by the temperature time correction unit.

As described above, the temperature time correction unit corrects the servo pressure rising start time or the setting time stored in the storage unit on the basis of the brake fluid temperature detected by the temperature detection unit. This can prevent a lag of generation of the servo pressure, and generation of an excessive servo pressure that is not based on the operating amount of the brake operating member, due to variations in the brake fluid temperature in the pre-fill control. As the brake fluid temperature lowers, flowing of the brake fluid is further inhibited, delaying generation of the servo pressure by the mechanical action in the regulator. Thus, the temperature time correction unit corrects servo pressure rising start time or the setting time so as to be longer as the brake fluid temperature decreases, preventing the lag of generation of the servo pressure. Further, as the brake fluid temperature rises, the flowing resistance of the brake fluid lowers, promoting generation of the servo pressure by the mechanical action in the regulator. The temperature time correction unit corrects the servo pressure rising start time or the setting time so as to be shorter as the brake fluid temperature increases, preventing generation of an excessive servo pressure that is not based on the operating amount of the brake operating member, which is caused by inputting of the pilot pressure increased after generation of the servo pressure into the pilot chamber.

According to a fifth aspect of the invention, in any of the first to fourth aspects of the invention, the vehicular braking device further includes a determination unit that determines whether or not the servo pressure starts to rise; and a measurement unit that opens the electromagnetic valve from a time when the pilot pressure is the value equivalent to the atmospheric pressure to a time when the determination unit determines that the servo pressure starts to rise, and measures the servo pressure rising start time, and the storage unit stores the servo pressure rising start time measured by the measurement unit, or the setting time set based on the servo pressure rising start time measured by the measurement unit.

As described above, the determination unit determines that the servo pressure starts to rise. The measurement unit opens the electromagnetic valve from the time when the pilot pressure is the value equivalent to the atmospheric pressure to the time when the determination unit determines that the servo pressure starts to rise, and measures the servo pressure rising start time. Therefore, even when the servo pressure rising start time changes due to deterioration of the vehicular braking device over time, the determination unit and the measurement unit can measure the servo pressure rising start time. In this manner, such change of the servo pressure rising start time due to deterioration of the vehicular braking device over time can be addressed.

According to a sixth aspect of the invention, in the fifth aspect of the invention, the vehicular braking device further includes an accumulator pressure detection unit that detects an accumulator pressure that is the fluid pressure of the brake fluid stored in the accumulator, and the storage unit associates the servo pressure rising start time or the setting time with the accumulator pressure detected by the accumulator pressure detection unit, when the measurement unit measures the servo pressure rising start time, and stores the associated servo pressure rising start time or the setting time, and in the pre-fill control, the pre-fill control unit opens the electromagnetic valve for the servo pressure rising start time or the setting time that is associated with the accumulator pressure detected by the accumulator pressure detection unit.

As described above, the storage unit associates the servo pressure rising start time or the setting time with the accumulator pressure detected by the accumulator pressure detection unit when the measurement unit measures the servo pressure rising start time, and stores the associated servo pressure rising start time or the setting time. In the pre-fill control, the pre-fill control unit opens the electromagnetic valve for the servo pressure rising start time or the setting time that is associated with the accumulator pressure detected by the accumulator pressure detection unit. Thereby, the pre-measured servo pressure rising start time is stored in association with the accumulator pressure at measurement. Then, the pre-fill control is performed in consideration with the accumulator pressure at measurement of the servo pressure rising start time. This can prevent a lag of generation of the servo pressure, and generation of an excessive servo pressure that is not based on the operating amount of the brake operating member, due to a difference between the accumulator pressure at measurement of the servo pressure rising start time and the accumulator pressure in the pre-fill control.

According to a seventh aspect of the invention, in the fifth or sixth aspect of the invention, the vehicular braking device further includes a temperature detection unit that detects the brake fluid temperature, and the storage unit associates the servo pressure rising start time or the setting time with the brake fluid temperature, which is detected by the temperature detection unit when the measurement unit detects the servo pressure rising start time, and the pre-fill control unit opens the electromagnetic valve for the servo pressure rising start time or the setting time that is associated with the brake fluid temperature in the pre-fill control.

As described above, the storage unit associates the servo pressure rising start time or the setting time with the brake fluid temperature, which is detected by the temperature detection unit when the servo pressure rising start time is measured, and stores the associated servo pressure rising start time or the setting time. In the pre-fill control, the pre-fill control unit opens the electromagnetic valve for the servo pressure rising start time or the setting time associated with the brake fluid temperature. In this manner, the pre-measured servo pressure rising start time is associated with the brake fluid temperature at measurement, and stored. Then, the pre-fill control is performed in consideration with the brake fluid temperature at measurement of the servo pressure rising start time. This can prevent a lag of generation of the servo pressure, and generation of an excessive servo pressure that is not based on the operating amount of the brake operating member, due to a difference between the brake fluid temperature at measurement of the servo pressure rising start time and the brake fluid temperature in the pre-fill control.

According to an eighth aspect of the invention, in any of the fifth to seventh aspects of the invention, the vehicular braking device further includes a servo pressure detection unit that detects the servo pressure, and the determination unit determines that the servo pressure starts to rise on the basis of the servo pressure detected by the servo pressure detection unit.

As described above, since the servo pressure detection unit that directly detects the servo pressure determines that the servo pressure starts to rise, the servo pressure rising start time can be correctly detected.

According to a ninth aspect of the invention, in any of the fifth to eighth aspects of the invention, the vehicular braking device further includes an accumulator pressure detection unit that detects an accumulator pressure that is the fluid pressure of the brake fluid stored in the accumulator, and the determination unit determines that the servo pressure starts to rise on the basis of the accumulator pressure detected by the accumulator pressure detection unit.

Therefore, without using the servo pressure detection unit that detects the servo pressure, the servo pressure can be detected using the accumulator pressure detection unit that detects the accumulator pressure. That is, since the accumulator pressure decreases with an increase in the servo pressure, the accumulator pressure detection unit can detect a decrease in the accumulator pressure to detect an increase in the servo pressure.

DESCRIPTION OF EMBODIMENTS

A vehicular braking device1000in accordance with an embodiment of the present invention will be described below with reference to figures. In figures for description, shape and size of each component may not be necessarily precise.

As illustrated inFIG. 1, the vehicular braking device1000includes a friction braking force generator BF for generating a friction braking force in wheels5FR,5FL,5RR, and5RL, and a brake ECU6for controlling the friction braking force generator BF.

The friction braking force generator BF includes a master cylinder1, a reaction force generator2, a first control valve22, a second control valve23, a servo pressure generator4, a fluid pressure controller53, various sensors71to76and the like.

The master cylinder1serves to a brake fluid to the fluid pressure controller53according to the operating amount of a brake pedal10(corresponding to “brake operating member”), and includes a main cylinder11, a cover cylinder12, an input piston13, a first master piston (corresponding to “master piston”)14, and a second master piston15and the like.

The main cylinder11is a substantially cylindrical closed-end housing that is closed at its front and opened at its rear. The main cylinder11is provided with an inner wall111inwardly protruding like a flange, in the rear of the inner circumference of the main cylinder11. A through hole111apenetrating in the forward and rearward direction is formed at the center of the inner wall111. Further, a small-diameter portion112(rear) and a small-diameter portion113(front) that have a smaller diameter than the main cylinder11are provided in front of the inner wall111. That is, the small-diameter portions112,113protrude inward circularly from the inner circumferential face of the main cylinder11. The first master piston14that is axially slidable on the small-diameter portion112is disposed in the main cylinder11. Similarly, the second master piston15that is axially slidable on the small-diameter portion113is disposed in the main cylinder11.

The cover cylinder12includes a substantially cylindrical cylinder portion121, a bellows tube-like boot122, and a cup-like compression spring123. The cylinder portion121is disposed at the rear end of the main cylinder11, and is coaxially fitted in a rear opening of the main cylinder11. A front part121aof the cylinder portion121has a larger inner diameter than the through hole111aof the inner wall111. Further, a rear part121bof the cylinder portion121has a smaller inner diameter than the front part121a.

The bellows tube-like dustproof boot122can contract and extend in the forward and rearward direction, and abut on an opening of the rear end of the cylinder portion121at the front side. A through hole122ais formed at the center of main cylinder in the rear of the boot122. The compression spring123is a coil-like biasing member disposed around the boot122, and is contracted such that its front side abuts the rear end of the main cylinder11, and its rear side comes close to the through hole122aof the boot122. The rear end of the boot122and the rear end of the compression spring123are connected to an operating rod10a. The compression spring123biases the operating rod10arearward.

The input piston13slides in the cover cylinder12according to the operation of the brake pedal10. The input piston13is a substantially cylindrical closed-end piston having a front bottom face and a rear opening. A bottom wall131forming the bottom face of the input piston13has a larger diameter than the other parts of the input piston13. The input piston13is axially slidable in the rear part121bof the cylinder portion121in a fluid-tight manner, and the bottom wall131is disposed on the inner circumferential side of the front part121aof the cylinder portion121.

The operating rod10alinked to the brake pedal10is disposed in the input piston13. A pivot10bat the front end of the operating rod10acan press the input piston13forward. The rear end of the operating rod10aprotrudes outward through the rear opening of the input piston13and the through hole122aof the boot122, and is connected to the brake pedal10. When the brake pedal10is pressed, the operating rod10aadvances while axially pressing the boot122and the compression spring123. With advancement of the operating rod10a, the input piston13also advances in conjunction.

The first master piston14is disposed so as to be axially slidable along the inner wall111of the main cylinder11. The first master piston14is unitarily formed of a pressing tubular portion141, a flange portion142, and a protrusion portion143in this order from the front. The pressing tubular portion141is a substantially cylindrical closed-end portion having a front opening, has a gap from the inner circumferential face of the main cylinder11, and is slidingly contact with the small-diameter portion112. A biasing member144that is a coil spring is disposed in an internal space of the pressing tubular portion141away from the second master piston15. The biasing member144biases the first master piston14rearward. In other words, the first master piston14is biased toward a set initial position by the biasing member144.

The flange portion142has a larger diameter than the pressing tubular portion141, and is slidingly contact with the inner circumferential face of the main cylinder11. The protrusion portion143has a smaller diameter than the flange portion142, and is slidingly contact with the through hole111aof the inner wall111in a fluid-tight manner. The rear end of the protrusion portion143protrudes into an internal space of the cylinder portion121through the through hole111a, and is separated from the inner circumferential face of the cylinder portion121. The rear end face of the protrusion portion143is separated from the bottom wall131of the input piston13, and a distance d between them is variable.

A first master chamber1D is defined by the inner circumferential face of the main cylinder11, the front side of the pressing tubular portion141of the first master piston14, and the rear side of the second master piston15. Further, a rear chamber in the rear of the first master chamber1D is defined by the inner circumferential face (inner circumferential portion) of the main cylinder11, the small-diameter portion112, the front surface of the inner wall111, and the outer circumferential face of the first master piston14. The front end and the rear end of the flange portion142of the first master piston14divide the rear chamber into a front part and a rear part, the front part defines a second fluid pressure chamber1C, and the rear part defines a servo chamber1A. Further, a first fluid pressure chamber1B is defined by the inner circumferential portion of the main cylinder11, the rear face of the inner wall111, the inner circumferential face (inner circumferential portion) of the front part121aof the cylinder portion121, the protrusion portion143(rear end) of the first master piston14, and the front end of the input piston13.

The second master piston15is disposed in front of the first master piston14in the main cylinder11so as to be axially slidable along the small-diameter portion113. The second master piston15is unitarily formed of a tubular pressing tubular portion151having a front opening, and a bottom wall152that closes the rear side of the pressing tubular portion151. The bottom wall152and the first master piston14support the biasing member144. A coil spring-like biasing member153is disposed in an internal space of the pressing tubular portion151away from a closed inner bottom face111dof the main cylinder11. The biasing member153biases the second master piston15rearward. In other words, the second master piston15is biased toward a set initial position by the biasing member153. A second master chamber1E is defined by the inner circumferential face of the main cylinder11, the inner bottom face111d, and the second master piston15.

The master cylinder1is formed with ports11ato11ithat communicates the inside with the outside of the master cylinder1. The port11ais formed in the rear of the inner wall111in the main cylinder11. The port11bis formed at the same axial position as the port11aas opposed to the port11a. The port11acommunicates with the port11bvia an annular space between the inner circumferential face of the main cylinder11and the outer circumferential face of the cylinder portion121. The port11aand the port11bare connected to a pipe161as well as a reservoir171.

The port11bcommunicates with the first fluid pressure chamber1B via a passage18formed in the cylinder portion121and the input piston13. When the input piston13advances, the passage18is blocked, disconnecting the first fluid pressure chamber1B from the reservoir171.

The port11cis formed in the rear of the inner wall111and in front of the port11a, and communicates the first fluid pressure chamber1B with a pipe162. The port11dis formed in front of the inner wall111and in front of the port11c, and communicates the servo chamber1A with a pipe163. The port11eis formed in front of the port11d, and communicates the second fluid pressure chamber1C with a pipe164.

The port11fis formed between sealing members91,92of the small-diameter portion112, and communicates a reservoir172with the inside of the main cylinder11. The port11fcommunicates with the first master chamber1D via a passage145formed in the first master piston14. The passage145is formed so as to disconnect the port11ffrom the first master chamber1D when the first master piston14advances. The port11gis formed in front of the port11f, and communicates the first master chamber1D with a pipe51.

The port11his formed between sealing members93,94of the small-diameter portion113, and communicates a reservoir173with the inside of the main cylinder11. The port11hcommunicates with the second master chamber1E via a passage154formed in the pressing tubular portion151of the second master piston15. The passage154is positioned so as to disconnect the port11hfrom the second master chamber1E when the second master piston15advances. The port11iis formed in front of the port11h, and communicates the second master chamber1E with a pipe52.

Sealing member such as O-rings (black circles in this figure) are disposed in the master cylinder1as appropriate. The sealing members91,92are disposed on the small-diameter portion112, and abut the outer circumferential face of the first master piston14in a fluid-tight manner. Similarly, the sealing members93,94are disposed on the small-diameter portion113, and abut the outer circumferential face of the second master piston15in a fluid-tight manner. Further, sealing members95,96are disposed between the input piston13and the cylinder portion121.

A stroke sensor71detects the operating amount (brake operating amount, pedal stroke) of the brake pedal10by the driver, and transmits a detection signal to the brake ECU6. A brake stop switch72detects whether the driver operates the brake pedal10using a binary signal, and transmits a detection signal to the brake ECU6.

The reaction force generator2serves to generate a reaction force that counteracts an operating force of the brake pedal10, and is configured of mainly a stroke simulator21. The stroke simulator21generates a reaction force fluid pressure in the first fluid pressure chamber1B and the second fluid pressure chamber1C in response to the operation of the brake pedal10. The stroke simulator21is configured by slidably fitting a piston212into a cylinder211. The piston212is biased forward by a compression spring213, and a reaction force fluid pressure chamber214is formed on the side of the front surface of the piston212. The reaction force fluid pressure chamber214is connected to the second fluid pressure chamber1C via the pipe164and the port11e, and is connected to the first control valve22and the second control valve23via the pipe164.

The first control valve22is an electromagnetic valve that is closed in the nonconducting state, and is opened/closed under control of the brake ECU6. The first control valve22is connected between the pipe164and the pipe162. Here, the pipe164communicates with the second fluid pressure chamber1C via the port11e, and the pipe162communicates with the first fluid pressure chamber1B via the port11c. When the first control valve22opens, the first fluid pressure chamber1B is opened, and when the first control valve22closes, the first fluid pressure chamber1B is closed tightly. Thus, the pipe164and the pipe162are provided to communicate the first fluid pressure chamber1B with the second fluid pressure chamber1C.

The first control valve22closes in the nonconducting state to disconnect the first fluid pressure chamber1B from the second fluid pressure chamber1C. Accordingly, the first fluid pressure chamber1B is closed tightly and thus, the brake fluid has nowhere to go, and the input piston13and the first master piston14work together while keeping a constant distance d therebetween. The first control valve22is opened in the conducting state to communicate the first fluid pressure chamber1B with the second fluid pressure chamber1C. As a result, a change in the volume of the first fluid pressure chamber1B and the second fluid pressure chamber1C due to advance/retreat of the first master piston14is absorbed by movement of the brake fluid.

A brake fluid sensor73serves to detect the reaction force fluid pressure in the second fluid pressure chamber1C and the first fluid pressure chamber1B, and is connected to the pipe164. The brake fluid sensor73detects the pressure in the second fluid pressure chamber1C when the first control valve22is in the closed state, and also detects the pressure in the first fluid pressure chamber1B (or the reaction force fluid pressure) when the first control valve22is in the opened state. The brake fluid sensor73detects temperature of the brake fluid flowing through the pipe164. The brake fluid sensor73transmits a detection signal to the brake ECU6.

The second control valve23is an electromagnetic valve that opens in the nonconducting state, and is opened/closed under control of the brake ECU6. The second control valve23is connected between the pipe164and the pipe161. Here, the pipe164communicates with the second fluid pressure chamber1C via the port11e, and the pipe161communicates with the reservoir171via the port11a. Accordingly, the second control valve23communicates the second fluid pressure chamber1C with the reservoir171in the nonconducting state, generating no reaction force fluid pressure, and disconnects the second fluid pressure chamber1C from the reservoir171in the conducting state, generating the reaction force fluid pressure.

The servo pressure generator4includes a pressure decrease valve41, a pressure increase valve42, a high-pressure feed portion43, a regulator44and the like. The pressure decrease valve41is an electromagnetic valve that opens in the nonconducting state, and its flow rate is controlled by the brake ECU6. One side of the pressure decrease valve41is connected to the pipe161via a pipe411, and the other side of the pressure decrease valve41is connected to a pipe413. That is, one side of the pressure decrease valve41communicates with the reservoir171via the pipes411,161, and the ports11a,11b. The pressure increase valve42is an electromagnetic valve that closes in the nonconducting state, and its flow rate is controlled by the brake ECU6. One side of the pressure increase valve42is connected to a pipe421, and the other side of the pressure increase valve42is connected to a pipe422. The pressure decrease valve41and the pressure increase valve42are pilot fluid pressure generators that adjust the flow of the brake fluid from the accumulator431to a first pilot chamber4D.

The high-pressure feed portion43is a portion that feeds the high-pressure brake fluid to the regulator44. The high-pressure feed portion43includes an accumulator431, a fluid pressure pump432, a motor433, a reservoir434and the like.

The accumulator431is a tank that stores the high-pressure brake fluid, which has the fluid pressure of the brake fluid as “accumulator pressure”. The accumulator431is connected to the regulator44and the fluid pressure pump432via the pipe431a. The fluid pressure pump432is driven by the motor433, and pressure-feeds the brake fluid stored in the reservoir434to the accumulator431. A brake fluid sensor75provided on the pipe431adetects the accumulator fluid pressure of the accumulator431. The accumulator fluid pressure corresponds to the amount of the brake fluid stored in the accumulator431. The brake fluid sensor75detects temperature of the brake fluid flowing through the pipe431a. The brake fluid sensor75transmits a detection signal to the brake ECU6.

When the brake fluid sensor75detects that the accumulator fluid pressure lowers to a predetermined value or less, the motor433is driven according to an instruction from the brake ECU6. Thereby, the fluid pressure pump432pressure-feeds the brake fluid to the accumulator431, and returns the accumulator fluid pressure to a predetermined value or more.

FIG. 2is a partial sectional view illustrating internal configuration of a mechanical regulator44configuring the servo pressure generator4. As illustrated, the regulator44includes a cylinder441, a ball valve442, a biasing portion443, a valve seat444, a control piston445, a sub piston446and the like. The regulator44generates the “servo pressure” corresponding to the “pilot pressure” inputted to the first pilot chamber4D in the servo chamber1A on the basis of the “accumulator pressure” stored in the accumulator431.

The cylinder441includes a substantially cylindrical closed-end cylinder case441ahaving a bottom face on one side (right side in the figure) and a cover member441bthat closes an opening (left side in the figure) of the cylinder case441a. The cylinder case441ais formed with a plurality of ports4ato4hthat communicate the inside with the outside of the cylinder case. The cover member441bis a substantially cylindrical closed-end body, and has ports opposed to the plurality of ports4ato4hof the cylinder case.

The port4ais connected to a pipe431a. The port4bis connected to the pipe422. The output port4cis connected to the pipe163. The pipe163connects the servo chamber1A to the output port4c. The port4dis connected to the pipe161via a pipe414. The port4eis connected to a pipe424, and is connected to the pipe422via a relief valve423. The port4fis connected to the pipe413. The port4gis connected to the pipe421. The port4his connected to a pipe511branching from the pipe51.

The ball valve442is a ball-shaped valve, and is disposed on the side of the bottom face of the cylinder case441ain the cylinder441(also referred to as cylinder bottom face side). The biasing portion443is a spring member that biases the ball valve442toward the side of an opening of the cylinder case441a(also referred to as cylinder opening side), and is provided on the bottom face of the cylinder case441a. The valve seat444is a wall member provided on the inner circumferential face of the cylinder case441a, and divides the cylinder opening side from the cylinder bottom face side. A penetration passage444athat communicates the cylinder opening side with the cylinder bottom face side is formed at the center of the valve seat444. The valve seat444holds the ball valve442from the cylinder opening side such that the biased ball valve442closes the penetration passage444a. A valve seat face444b, on which the ball valve442is removably seated (contact), is formed in an opening of the penetration passage444aon the cylinder bottom face side.

A space defined by the ball valve442, the biasing portion443, the valve seat444, and the inner circumferential face of the cylinder case441aof the cylinder bottom face side is defined as a “first chamber4A”. The first chamber4A is filled with the brake fluid, is connected to the pipe431avia the port4a, and is connected to the pipe422via the port4b.

The control piston445includes a substantially cylindrical body portion445aand a substantially cylindrical protruding portion445bhaving a smaller diameter than the body portion445a. The body portion445ais coaxially and fluid-tightly disposed in the cylinder441on the cylinder opening side of the valve seat444so as to be axially slidable. The body portion445ais biased toward the cylinder opening side by a biasing member not shown. A passage445cthat is opened on the circumference face of the body portion445aat both ends and radially (vertically in this figure) extends is formed substantially at the axial center of the body portion445a. The inner circumferential face of the part of the cylinder441, which corresponds to the openings of the passage445c, has the port4d, and is dented. The dented is defined as a “third chamber4C”.

The protruding portion445bprotrudes toward the cylinder bottom face side from the center of the end face of the body portion445aon the cylinder bottom face side. The protruding portion445bhas a smaller diameter than the penetration passage444aof the valve seat444. The protruding portion445band the penetration passage444aare coaxially disposed. A front end of the protruding portion445bis separated from the ball valve442by a predetermined distance on the cylinder opening side. The protruding portion445bis formed with a passage445dthat is opened at the center of the end face of the protruding portion445bon the cylinder bottom face side and axially extends. The passage445dextends into the body portion445a, and is connected to the passage445c.

A space delimited by the end face of the body portion445aon the cylinder bottom face side, the outer circumferential face of the protruding portion445b, the inner circumferential face of the cylinder441, the valve seat444, and the ball valve442is defined as a “second chamber4B”. The second chamber4B communicates with the ports4d,4evia the passages445d,445c, and the third chamber4C.

The sub piston446includes a sub body portion446a, a first protruding portion446b, and a second protruding portion446c. The sub body portion446ais substantially cylindrical. The sub body portion446ais coaxially and fluid-tightly disposed in the cylinder441on the cylinder opening side of the body portion445aso as to be axially slidable.

The first protruding portion446bis substantially cylindrical, has a smaller diameter than the sub body portion446a, and protrudes at the center of the end face of the sub body portion446aon the cylinder bottom face side. The first protruding portion446babuts the end face of the body portion445aon the cylinder opening side. The second protruding portion446chas the same shape as the first protruding portion446b, and protrudes at the center of the end face of the sub body portion446aon the cylinder opening side. The second protruding portion446cabuts the cover member441b.

A space delimited by the end face of the sub body portion446aon the cylinder bottom face side, the outer circumferential face of the first protruding portion446b, the end face of the control piston445on the cylinder opening side, and the inner circumferential face of the cylinder441is defined as a first pilot chamber4D. The first pilot chamber4D communicates with the pressure decrease valve41via the port4fand the pipe413, and communicates with the pressure increase valve42via the port4gand the pipe421.

A space delimited by the end face of the sub body portion446aon the cylinder opening side, the outer circumferential face of the second protruding portion446c, the cover member441b, and the inner circumferential face of the cylinder441is defined as a “second pilot chamber4E”. The second pilot chamber4E communicates with the port11gvia the port4hand the pipes511,51. Each of the chambers4A to4E is filled with the brake fluid. A brake fluid sensor74serves to detect the “servo pressure” fed to the servo chamber1A, and is connected to the pipe163. The brake fluid sensor74detects temperature of the brake fluid flowing through the pipe163. The brake fluid sensor74transmits a detection signal to the brake ECU6.

The first master chamber1D and the second master chamber1E that generate the fluid pressure of the master cylinder (master fluid pressure) communicate with the wheel cylinders541to544via the pipes51,52and the fluid pressure controller53. The wheel cylinders541to544configure the friction brake devices BFR to BRL provided on the wheels5FR to5RL, respectively. Specifically, the port11gof the first master chamber1D and the port11iof the second master chamber1E are coupled to the fluid pressure controller53for anti-lock brake control, anti-skid control, and anti-collision control via the pipe51and the pipe52, respectively. The fluid pressure controller53is coupled to the wheel cylinders541to544that activate the respective friction brake devices BFR to BRL for braking the wheels5FR to5RL.

In the fluid pressure controller53thus configured, the brake ECU6switches each of the holding valves and the pressure decrease valve according to the master pressure, the wheel speed, and longitudinal acceleration, and activates the motor as necessary to adjust the brake fluid pressure applied to the wheel cylinders541to544, that is, the braking force applied to the wheels5FR to5RL, thereby performing anti-lock brake control, anti-skid control, and anti-collision control. The fluid pressure controller53adjusts the amount and timing of the brake fluid supplied from the master cylinder1according to an instruction of the brake ECU6, and supplies the adjusted brake fluid to the wheel cylinders541to544.

The fluid pressure sent from the accumulator431of the servo pressure generator4is controlled by the pressure increase valve42and the pressure decrease valve41, generating the “servo pressure” in the servo chamber1A. Then, the first master piston14and the second master piston15advance to pressurize the first master chamber1D and the second master chamber1E. The fluid pressure in the first master chamber1D and the second master chamber1E is inputted as the master pressure from the ports11g,11ito the wheel cylinders541to544via the pipes51,52and the fluid pressure controller53and thus, a friction braking force is applied to the wheels5FR to5RL.

The brake ECU6is an electronic control unit, and has a microcomputer. The microcomputer includes an input/output interface, and a storage unit such as CPU, RAM, ROM, or nonvolatile memory, which are interconnected via a bus.

To control the electromagnetic valves22,23,41, and42, the motor433and the like, the brake ECU6is connected to the various sensors71to76. The brake ECU6receives inputs of information detected by the various sensors71to76.

Brake control of the brake ECU6will be described below. The brake ECU6calculates a “demand braking force” required by the driver on the basis of the operating amount of the brake pedal10(movement of the input piston13) or the operating force of the brake pedal10, which is detected by the stroke sensor71. Then, the brake ECU6calculates a “target servo pressure” that is an intended “servo pressure” on the basis of the “demand braking force”. In the state where the first control valve22is opened and the second control valve23is closed, the brake ECU6feedback-controls the pressure decrease valve41and the pressure increase valve42such that the “servo pressure” inputted to the servo chamber1A becomes the “target servo pressure”, according to the detection signal from the brake fluid sensor74.

Describing in detail, when the brake pedal10is not pressed, the above-mentioned state occurs. That is, the ball valve442closes the penetration passage444aof the valve seat444. The pressure decrease valve41is opened, and the pressure increase valve42is closed. That is, the first chamber4A is separated from the second chamber4B.

The second chamber4B communicates with the servo chamber1A via the pipe163, and these chambers are at the same pressure. The second chamber4B communicates with the third chamber4C via the passages445c,445dof the control piston445. Accordingly, the second chamber4B and the third chamber4C communicate with the reservoir171via the pipes414,161. One side of the first pilot chamber4D is closed with the pressure increase valve42, and the other side of the first pilot chamber4D communicates with the reservoir171via the pressure decrease valve41. The first pilot chamber4D and the second chamber4B are at the same pressure. The second pilot chamber4E communicates with the first master chamber1D via the pipes511,51, and these chambers are at the same pressure.

When the brake pedal10is pressed, as described above, the brake ECU6feedback-controls the pressure decrease valve41and the pressure increase valve42such that the “servo pressure” inputted to the servo chamber1A becomes the “target servo pressure”, according to the detection signal from the brake fluid sensor74. That is, the brake ECU6performs control to close the pressure decrease valve41and open the pressure increase valve42.

The pressure increase valve42is opened to communicate the accumulator431with the first pilot chamber4D. The pressure decrease valve41is closed to disconnect the first pilot chamber4D from the reservoir171. The high-pressure brake fluid fed from the accumulator431increases the pressure in the first pilot chamber4D. The increase in the pressure in the first pilot chamber4D causes the control piston445to slide to the cylinder bottom face side. Then, the front end of the protruding portion445bof the control piston445abuts the ball valve442, and the ball valve442closes the passage445d. Accordingly, the second chamber4B is disconnected from the reservoir171.

When the control piston445slides to the cylinder bottom face side, the protruding portion445bpushes the ball valve442to the cylinder bottom face side, to separate the ball valve442from the valve seat face444b. Thus, the first chamber4A communicates with the second chamber4B via the penetration passage444aof the valve seat444. Since the first chamber4A receives the high-pressure brake fluid from the accumulator431, the pressure in the second chamber4B increases due to the communication. It is noted that as a distance between the ball valve442and the valve seat face444bincreases, the passage of the brake fluid becomes larger, and the fluid pressure in the passage downstream from the ball valve442becomes higher. That is, as the fluid pressure (“pilot pressure”) of the brake fluid inputted to the first pilot chamber4D becomes larger, a travel of the control piston445becomes larger and the distance between the ball valve442and the valve seat face444bbecomes larger to make the fluid pressure (“servo pressure”) of the second chamber4B higher.

With the increase in the pressure in the second chamber4B, the pressure in the servo chamber1A communicating with the second chamber4B also increases. Due to the increase in the servo chamber1A, the first master piston14advances, and the pressure in the first master chamber1D increases. Then, the second master piston15also advances, and the pressure in the second master chamber1E increases. Due to the pressure increase in the first master chamber1D, the high-pressure brake fluid is supplied to the fluid pressure controller53and the second pilot chamber4E. Although the pressure in the second pilot chamber4E increases, the pressure in the first pilot chamber4D also increases and thus, the sub piston446does not travel. As described above, the high-pressure (master pressure) brake fluid is supplied to the fluid pressure controller53, activating a frictional brake to brake the vehicle.

To release the braking operation, conversely, the pressure decrease valve41is opened and the pressure increase valve42is closed, to communicate the reservoir171with the first pilot chamber4D. As a result, the control piston445retreats to return to the state before pressing of the brake pedal10.

Summary of this Embodiment

Summary of this embodiment will be described below using a time chart inFIG. 3. A “target pilot pressure” inFIG. 3is a “pilot pressure” that is not calculated by the brake ECU6, but is necessary for generating “target servo pressure” in the regulator44. First, operations of the conventional servo pressure generator4will be described below. As described above, when the brake pedal10is pressed, the pressure increase valve42is opened, such that the “pilot pressure” inputted to the first pilot chamber4D starts to rise (T1inFIG. 3). Immediately after the “pilot pressure” starts to rise, due to a frictional force generated between a sealing member445gbetween the control piston445and the cover member441b, and a member in close contact with the sealing member445g(in this embodiment, cover member441b), the control piston445does not slide to the cylinder bottom face side (illustrated inFIG. 2), and the “pilot pressure” continues to rise (f1inFIG. 3).

When the “pilot pressure” reaches the fluid pressure at which the control piston445slides to the cylinder bottom face side against the frictional force, the control piston445slides to the cylinder bottom face side. Then, the “pilot pressure” becomes constant (T2to T4, f2inFIG. 3). While the control piston445slides to the cylinder bottom face side, the “pilot pressure” is constant at the fluid pressure at which the control piston445starts to slide to the cylinder bottom face side (f2inFIG. 3).

Then, the control piston445slides to the cylinder bottom face side, and the front end of the protruding portion445bof the control piston445abuts the ball valve442. Then, the constant “pilot pressure” starts to rise (T4, f3inFIG. 3). With the increase in the “pilot pressure” (f4inFIG. 3), the protruding portion445bpushes the ball valve442to the cylinder bottom face side, to separate the ball valve442from the valve seat face444b. Then, the “servo pressure” generates in the second chamber4B (T4, f5inFIG. 3), and rises (f6inFIG. 3).

As described above, the frictional force generated between the sealing member445gand the member in close contact with the sealing member and sliding of the control piston445to the cylinder bottom face side causes a time lag between the time when the “pilot pressure” is inputted to the first pilot chamber4D and the time when the “servo pressure” is actually generated. The time lag will be hereinafter referred to as “servo pressure rising start time”.

As described above, before the “servo pressure rising start time” elapses from inputting of the “pilot pressure” to the first pilot chamber4D, the “servo pressure” is not generated and thus, no friction braking force occurs in the friction brake devices BFR to BRL. In this embodiment, the “servo pressure rising start time” is shortened by performing the pre-fill control to fully open the pressure increase valve42until the “servo pressure” is generated (T1to T3inFIG. 3), and to input the maximum “pilot pressure” to the first pilot chamber4D.

Depending on the manufactured regulator44, the distance between the front end of the protruding portion445bof the control piston445and the ball valve442varies. For this reason, the “servo pressure rising start time” at the time when the pressure increase valve42is fully opened to input the maximum “pilot pressure” to the first pilot chamber4D varies among products of the regulator44. Thus, in this embodiment, for example, before shipment of the vehicle, the “servo pressure rising start time” at the time when the pressure increase valve42is fully opened to input the maximum “pilot pressure” to the first pilot chamber4D is previously measured for each product of the friction braking force generator BF. Then, when the brake pedal10is pressed, the pressure increase valve42is fully opened to increase the “pilot pressure” inputted to the first pilot chamber4D for the “pilot pressure increase time” (setting time) calculated based on the “servo pressure rising start time”. In this manner, product-by-product variations in “servo pressure rising start time” are absorbed.

The “pilot pressure increase time” is a time during which the “pilot pressure” is increased to rapidly put the front end of the protruding portion445bof the control piston445into contact with the ball valve442. The “pilot pressure increase time” is a time during which the “pilot pressure” is increased to prevent the “pilot pressure” increased after the ball valve442is separated from the valve seat face444bto generate the “servo pressure” from being inputted to the first pilot chamber4D. This will be described below in detail using a flow chart.

(Servo Pressure Rising Start Time Measurement Processing)

“Servo pressure rising start time measurement processing” will be described below using a flow chart inFIG. 4. The “servo pressure rising start time measurement processing” is executed, for example, before shipment of the vehicle, or after an elapse of a predetermined time from execution of the “servo pressure rising start time measurement processing”. When the “servo pressure rising start time measurement processing” starts, the brake ECU6(servo pressure rising start time measurement unit6b), in Step S11, calculates the brake fluid temperature on the basis of the detection signal from at least one of the brake fluid sensor73to75and in Step S12, detects the “accumulator pressure” on the basis of the detection signal from the brake fluid sensor75, and a program goes to Step S13.

In Step S13, in the closed state of the pressure decrease valve41, the brake ECU6(servo pressure rising start time measurement unit6b) fully opens the pressure increase valve42to generate a maximum “pilot pressure”. Upon termination of Step S13, the program proceeds to Step S14.

In Step S14, the brake ECU6(servo pressure rising start time measurement unit6b) measures the “servo pressure rising start time” (full-open rising start time) on the basis of the detection signal from the brake fluid sensor74. The servo pressure rising start time means a period from a time when the first pilot chamber4D is the value equivalent to the atmospheric pressure, the brake fluid flows into the first pilot chamber4D, and the “pilot pressure” is inputted to the first pilot chamber4D (“pilot pressure” is generated), to a time when the “servo pressure” is actually generated. In this embodiment, when the fluid pressure (“servo pressure”) detected by the brake fluid sensor74becomes a specified pressure (for example, 0.1 Mpa) or more, the brake ECU6(servo pressure rising start time measurement unit6b) determines that the “servo pressure” starts to rise, and the “servo pressure” is generated. The value equivalent to the atmospheric pressure includes the atmospheric pressure and pressures that are higher than the atmospheric pressure, but do not cause the “servo pressure”. Upon termination of Step S14, the program proceeds to Step S15.

In Step S15, the brake ECU6(servo pressure rising start time measurement unit6b) associates the “servo pressure rising start time” measured in Step S14with the brake fluid temperature detected in Step S11, and the “accumulator pressure” detected in Step S12, and stores them in a storage unit6aof the brake ECU6. Upon termination of Step S15, “servo pressure increase start measurement time processing” finishes.

“Servo pressure control processing” will be described below using a flow chart inFIG. 5. When an ignition of the vehicle is turned ON to make the vehicle drivable, “servo pressure control processing” starts, and the program proceeds to Step S21.

In Step S21, when the brake ECU6(braking force generation determination unit6e) determines that there is a probability of generation of the braking force in the friction brake devices BFR to BRL on the basis of the detection signal from the stroke sensor71(Step S21: YES), the program proceeds to Step S22. When the brake ECU6(braking force generation determination unit6e) determines that there is no probability of generation of the braking force in the friction brake devices BFR to BRL (Step S21: NO), processing in Step S21is repeated. In this embodiment, when the driver presses the brake pedal10, and the operating amount detected by the stroke sensor71is larger than a specified operating amount A, the brake ECU6determines that there is the probability of generation of the braking force in the friction brake devices BFR to BRL. On the contrary, when the operating amount detected by the stroke sensor71is the specified operating amount A or less, the brake ECU6determines that there is no probability of generation of the braking force in the friction brake devices BFR to BRL. The specified operating amount A is a value that is a braking force generation start operating amount B or less. The braking force generation start operating amount B actually generates the braking force in the friction brake devices BFR to BRL through pressing of the brake pedal10by the driver. That is, the operating amount (deadband) of the brake pedal10, which is smaller than the braking force generation start operating amount B, generates no braking force in the friction brake devices BFR to BRL.

The brake ECU6, in Step S22, calculates the brake fluid temperature on the basis of the detection signal from at least one of the brake fluid sensor73to75, and in Step S23, detects the “accumulator pressure” on the basis of the detection signal from the brake fluid sensor75, and the program goes to Step S24.

In Step S24, the brake ECU6(pilot pressure increase time calculation unit6c) calculates the “pilot pressure increase time” on the basis of the “servo pressure rising start time” (full-open rising start time), the brake fluid temperature, and the “accumulator pressure” (Step S15inFIG. 4), which are associated and stored in the storage unit6a, the brake fluid temperature detected in Step S22, and the “accumulator pressure” detected in Step S23. This will be specifically described below.

First, the brake ECU6(pilot pressure increase time calculation unit6c, pressure time correction unit) refers to the “pilot pressure increase time mapping base data” (dot-and-dash lines inFIG. 6) that indicates relationship between the “accumulator pressure” and the “pilot pressure increase time”, which is previously stored in the storage unit6afor each the brake fluid temperature. Then, referring to the “pilot pressure increase time mapping base data”, the brake ECU6generates “pilot pressure increase time mapping data” (represented by a solid line inFIG. 6) on the basis of the “accumulator pressure” (1inFIG. 6), the “servo pressure rising start time” (2inFIG. 6), and the brake fluid temperature (Step S15inFIG. 4), which are associated and stored in the storage unit6a.

The relationship between the “accumulator pressure” and the “pilot pressure increase time” (dot-and-dash lines inFIG. 6) is previously identified for each the brake fluid temperature, and is previously stored in the brake ECU6. In the “pilot pressure increase time mapping base data”, as the “accumulator pressure” decreases, the “pilot pressure increase time” becomes longer. This is due to that as the “accumulator pressure” decreases, the generated “pilot pressure” decreases and the control piston445is harder to slide, requiring a longer “pilot pressure increase time”. In the “pilot pressure increase time mapping base data”, the “pilot pressure increase time” is set to be longer as the “servo pressure rising start time” increases. This is due to that as the “servo pressure rising start time” increases, the “pilot pressure increase time” necessary for starting to rise the “servo pressure” increases. In the “pilot pressure increase time mapping base data”, the “pilot pressure increase time” is set to be longer as the brake fluid becomes cooler. This is due to that as the brake fluid becomes cooler, the passage of the brake fluid is inhibited. Therefore, the generated “pilot pressure” becomes lower and the control piston445is harder to slide, requiring a longer “pilot pressure increase time”.

Next, the brake ECU6(pilot pressure increase time calculation unit6c) corrects the generated “pilot pressure increase time mapping data” on the basis of a difference between the brake fluid temperature detected in Step S11inFIG. 4and the brake fluid temperature detected in Step S22, and temperature correction data. The temperature correction data is, for example, a map that uniquely associates the temperature difference with an offset amount, and is stored in the storage unit6a. The brake ECU6acquires the offset amount for offsetting the generated “pilot pressure increase time mapping data” in the direction of increasing or decreasing the pilot pressure increase time, from the temperature correction data on the basis of the difference between the detected temperatures of the brake fluid. Then, as illustrated inFIG. 7, the brake ECU6corrects the generated “pilot pressure increase time mapping data” by offsetting the pilot pressure increase time of the generated “pilot pressure increase time mapping data” by the acquired offset amount. In correction using the temperature correction data, the “pilot pressure increase time mapping data” is corrected to decrease the “pilot pressure increase time” as the brake fluid temperature detected in Step S22is higher than the brake fluid temperature detected in Step S11of the “servo pressure rising start time measurement processing” inFIG. 4. On the contrary, the “pilot pressure increase time mapping data” is corrected to increase the “pilot pressure increase time” as the brake fluid temperature detected in Step S22becomes lower than the brake fluid temperature detected in Step S11inFIG. 4. In the example illustrated inFIG. 7, the brake fluid temperature detected in Step S22is 40° C., and the brake fluid temperature detected in Step S11inFIG. 4is 25° C. For this reason, the “pilot pressure increase time mapping data” is corrected to decrease the “pilot pressure increase time” by the offset amount calculated based on a difference (15° C.) between the brake fluid temperature (40° C.) detected in Step S22and the brake fluid temperature (25° C.) detected in Step S11inFIG. 4, and the temperature correction data. Dot-and-dash lines and a solid line inFIG. 7indicate the “pilot pressure increase time mapping data” corrected based on the difference between the brake fluid temperature detected in Step S11inFIG. 4and the brake fluid temperature detected in Step S22, and the temperature correction data.

Referring to the temperature-corrected “pilot pressure increase time mapping data”, the brake ECU6(pilot pressure increase time calculation unit6c, pressure time correction unit) calculates the “pilot pressure increase time” (setting time) (2inFIG. 7) corresponding to the “accumulator pressure” (1inFIG. 7) detected in Step S23. Upon termination of Step S24, the program proceeds to Step S25.

In Step S25, in the state where the pressure decrease valve41is closed, the brake ECU6(pre-fill control unit6d) fully opens the pressure increase valve42to input the brake fluid to the first pilot chamber4D, thereby starting the pre-fill control to generate the “pilot pressure” (increase the “pilot pressure”). Upon termination of Step S25, the program proceeds to Step S26.

In Step S26, when determining that the “pilot pressure increase time” calculated in Step S24elapses from generation of the “pilot pressure” in Step S25(Step S26: YES), the brake ECU6moves the program to Step S27. On the contrary, when determining that the “pilot pressure increase time” calculated in Step S24does not elapse from generation of the “pilot pressure” in Step S25(Step S26: NO), the brake ECU6returns the program to Step S25.

In Step S27, the brake ECU6feedback-controls the pressure increase valve42and the pressure decrease valve41on the basis of the detection signals detected by the stroke sensor71and the brake fluid sensor74, such that the “servo pressure” becomes the “target servo pressure”. Upon termination of Step S27, the program proceeds to Step S28.

In Step S28, when determining that the driver releases the brake pedal10on the basis of the detection signal from at least one of the stroke sensor71and the brake stop switch72(Step S28: YES), the brake ECU6returns the program to Step S21. On the contrary, when determining that the driver presses the brake pedal10(Step S28: NO), the brake ECU6returns the program to Step S27.

Effects of this Embodiment

As apparent from the above description, when the brake pedal10is pressed (Step S21inFIG. 5: YES), in Step S25inFIG. 5, the “pre-fill control” to increase the “pilot pressure” for the “pilot pressure increase time” (setting time) set based on the “servo pressure rising start time” is performed. Thus, as illustrated inFIG. 3, the time from inputting of the “pilot pressure” to the first pilot chamber4D of the regulator44to the generation of the “servo pressure” (“servo pressure rising start time”) is shortened than conventional.

That is, conventionally, even before generation of the “servo pressure”, the “pilot pressure” corresponding to the stroke of the brake pedal10is generated, delaying generation of the “servo pressure” caused by the mechanical action that is sliding of the control piston445in the regulator44. However, in this embodiment, during a time when the brake pedal10is pressed to generate the “servo pressure”, the brake fluid is flown from the accumulator431to the first pilot chamber4D to increase the “pilot pressure”, thereby shortening the time necessary for generating the “servo pressure”.

Since the “pilot pressure increase time” is calculated based on the “servo pressure rising start time” previously measured by opening the pressure increase valve42(electromagnetic valve) (Step S24inFIG. 5), product-by-product variations in the time for generating the servo pressure can be reduced.

The flow rate of the brake fluid flowing from the pressure increase valve42(electromagnetic valve) in the degree of opening from 0 to full varies among products of the pressure increase valve42. Variations in the flow rate of the brake fluid flowing from the fully-opened pressure increase valve42among products of the pressure increase valve42are small. As described above, in Step S15inFIG. 4, the storage unit6astores the “servo pressure rising start time” (full-open rising start time) in the state where the pressure increase valve42is fully opened. Since the variations in the flow rate of the brake fluid flowing from the fully-opened pressure increase valve42are small, small variations in the “servo pressure rising start time” (full-open rising start time) among products of the pressure increase valve42can be acquired. Then, in Step S24inFIG. 5, the brake ECU6calculates the “pilot pressure increase time” (setting time) on the basis of the “servo pressure rising start time” (full-open rising start time) stored in the storage unit6a. Then, in Step S25(pre-fill control) inFIG. 5, the brake ECU6(pre-fill control unit) fully opens the pressure increase valve42(electromagnetic valve) for the “pilot pressure increase time” (setting time). Thereby, at fully opening of the pressure increase valve42, the flow rate of the brake fluid hardly varies among products of the pressure increase valve42. This prevents a lag of generation of the “servo pressure”, and generation of an excessive “servo pressure” that is not based on the operating amount of the brake pedal10(brake operating member), due to variations in the flow rate of the brake fluid among products of the pressure increase valves42. Since the pressure increase valve42is fully opened in the pre-fill control, the brake fluid can be flown at the maximum flow rate from the pressure increase valve42into the first pilot chamber4D in the pre-fill control. Therefore, the “servo pressure rising start time” taken from pressing of the brake pedal10to generation of the “servo pressure” can be shortened as much as possible.

Also in Step S25inFIG. 5, since the “pilot pressure” is increased by fully opening the pressure increase valve42, the flow rate flowing to the pressure increase valve42becomes stable in any manufactured pressure increase valve42, preventing an excessive “servo pressure” that is not based on the operating amount of the brake pedal10, which is caused by the fact that the “pilot pressure” increased after generation of the “servo pressure” is inputted to the first pilot chamber4D.

The “pilot pressure increase time” (setting time) is calculated based on the “accumulator pressure” in the pre-fill control (at braking). This prevents a lag of generation of the “servo pressure” and an excessive “servo pressure” that is not based on the operating amount of the brake pedal10due to variations in the “accumulator pressure” in the pre-fill control. That is, as the “accumulator pressure” decreases, the “pilot pressure” generated at the pressure increase valve42decreases, further delaying generation of the “servo pressure” caused by the mechanical action in the regulator44. Thus, in Step S24inFIG. 5, the brake ECU6(pilot pressure increase time calculation unit6c, pressure time correction unit) calculates and corrects the “pilot pressure increase time” (setting time) stored in the storage unit6aon the basis of the “accumulator pressure” detected by the brake fluid sensor75(accumulator pressure detection unit). In this embodiment, as illustrated inFIG. 7, the “pilot pressure increase time” is calculated using the “pilot pressure increase time mapping data” in which the “pilot pressure increase time” becomes longer as the “accumulator pressure” decreases. This prevents a lag of generation of the “servo pressure”.

As the “accumulator pressure” increases, the “pilot pressure” occurring in the pressure increase valve42also increases, promoting generation of the “servo pressure” caused by the mechanical action in the regulator44. However, in this embodiment, as illustrated inFIG. 7, the “pilot pressure increase time” is calculated using the “pilot pressure increase time mapping data” in which the “pilot pressure increase time” decreases as the “accumulator pressure” increases, preventing an excessive “servo pressure” that is not based on the operating amount of the brake pedal10, which is caused by inputting the “pilot pressure” increased after generation of the “servo pressure” into the first pilot chamber4D.

In Step S24inFIG. 5, the brake ECU6(pilot pressure increase time calculation unit6c, temperature time correction unit) corrects the “pilot pressure increase time mapping data” on the basis of the brake fluid temperature detected by at least one of the brake fluid sensors73to75(temperature detection unit), and calculates and corrects the “pilot pressure increase time” (setting time) stored in the storage unit6a. This prevents a lag of generation of the “servo pressure” and generation of an excessive “servo pressure” that is not based on the operating amount of the brake pedal10, due to variations in the brake fluid temperature in the pre-fill control. That is, as the brake fluid becomes cooler, the brake fluid is harder to flow, further delaying the “servo pressure” caused by the mechanical action in the regulator44. However, in this embodiment, as illustrated inFIG. 7, the “pilot pressure increase time” is calculated using the “pilot pressure increase time mapping data” in which the “pilot pressure increase time” increases as the brake fluid temperature lowers. This can prevent a delay of generation of the “servo pressure”.

As the brake fluid becomes hotter, a flowing resistance of the brake fluid lowers, further promoting the “servo pressure” caused by the mechanical action in the regulator44. However, in this embodiment, as illustrated inFIG. 7, the “pilot pressure increase time” is calculated using the “pilot pressure increase time mapping data” corrected such that the “pilot pressure increase time” decreases as the brake fluid temperature rises. This can prevent generation of an excessive “servo pressure” that is not based on the operating amount of the brake pedal10, which is caused by inputting the “pilot pressure” increased after generation of the “servo pressure” into the first pilot chamber4D.

In Step S14inFIG. 4, the servo pressure rising start time measurement unit6b(determination unit) determines that the “servo pressure” starts to rise. Then, the servo pressure rising start time measurement unit6b(measurement unit) opens the pressure increase valve42(electromagnetic valve) from the time when the “pilot pressure” is the value equivalent to the atmospheric pressure to the time when the “servo pressure” is determined to start to rise, and measures the “servo pressure rising start time”. Therefore, even when the “servo pressure rising start time” changes due to a change in the vehicular braking device1000over time, the servo pressure rising start time measurement unit6b(determination unit, measurement unit) can measure the “servo pressure rising start time” without putting the vehicle into a maintenance shop. This can address the change in the servo pressure rising start time” due to the change in the vehicular braking device1000over time.

In Step S15inFIG. 4, the storage unit6aassociates the “pilot pressure increase time” (setting time) with the “accumulator pressure” detected by the brake fluid sensor75(accumulator pressure detection unit) at measurement of the “pilot pressure increase time”, and stores them. Then, in Step S24inFIG. 5, the brake ECU6(pilot pressure increase time calculation unit6c, pressure time correction unit) calculates the “pilot pressure increase time” on the basis of the accumulator pressure” and the “servo pressure rising start time” (setting time), which are associated and stored in the storage unit6a, and the “accumulator pressure” detected by the brake fluid sensor75(accumulator pressure detection unit). Then, in Step S25, the brake ECU6(pre-fill control unit6d) opens the pressure increase valve42(electromagnetic valve) for the “pilot pressure increase time” (setting time). This prevents a delay of generation of the “servo pressure” and generation of an excessive “servo pressure” that is not based on the operating amount of the brake pedal10due to a difference between the “accumulator pressure” at measurement of the “servo pressure rising start time” and the “accumulator pressure” in the pre-fill control.

In Step S15inFIG. 4, the “servo pressure rising start time” and the brake fluid temperature at measurement are associated with each other, and are stored in the storage unit6a. Then, in Step S24inFIG. 5, the “pilot pressure increase time” is calculated based on the brake fluid temperature and the “servo pressure rising start time”, which are associated and stored in the storage unit6a, and the detected brake fluid temperature. This prevents a delay of generation of the “servo pressure” and generation of an excessive “servo pressure” that is not based on the operating amount of the brake pedal10, due to a difference between the brake fluid temperature at measurement of the “servo pressure rising start time” and the brake fluid temperature in the pre-fill control.

In Step S14inFIG. 4, the brake ECU6(servo pressure rising start time measurement unit6b) determines that the “servo pressure” starts to rise on the basis of the “servo pressure” detected by the brake fluid sensor74(servo pressure detection unit). As described above, since the brake fluid sensor74(servo pressure detection unit) that directly detects the “servo pressure” determines that the “servo pressure” starts to rise, the “servo pressure rising start time” can be correctly detected.

Other Embodiments

In the above-mentioned embodiment, in Step S14inFIG. 4, the brake fluid sensor74that detects the “servo pressure” measures the “servo pressure rising start time”. However, the brake fluid sensor75that detects the “accumulator pressure” may measure the “servo pressure rising start time”. When the ball valve442is separated from the valve seat face444bto generate the “servo pressure”, the “accumulator pressure” decreases. In this embodiment, the brake fluid sensor75detects a decrease in the “accumulator pressure”, thereby detecting generation of the “servo pressure” to measure the “servo pressure rising start time”.

In the above-mentioned embodiment, the brake fluid temperature is calculated according to the detection signal from at least one of the brake fluid sensors73to75. However, the brake fluid temperature may be calculated based on conducting time of the pressure increase valve42or the pressure decrease valve41, travelling time of the vehicle, driving time of the engine, outdoor temperature, and so on.

In the above-mentioned embodiment, in Step S21, the brake ECU6(braking force generation determination unit) detects whether or not there is the probability of generation of the braking force in the friction brake devices BFR to BRL according to the detection signal from the stroke sensor71. However, the brake ECU6(braking force generation determination unit, pre-fill control unit) may determine the level of the probability of generation of the braking force in the friction brake devices BFR to BRL according to the detection signal from the stroke sensor71, and when determining that the probability of generation of the braking force in the friction brake devices BFR to BRL is high, may perform the pre-fill control. Further, when determining start of anti-skid control or anti-collision control, the brake ECU6may determine that the probability of generation of the braking force in the friction brake devices BFR to BRL is high (YES in Step S21). Alternatively, the brake ECU6may detect whether or not there is the probability of generation of the braking force in the friction brake devices BFR to BRL according to the detection signal from the brake stop switch72.

In the above-mentioned embodiment, in Step S24inFIG. 5, the brake ECU6calculates the “pilot pressure increase time” by referring to the “pilot pressure increase time mapping data” that indicates relationship between the “accumulator pressure” and the “pilot pressure increase time”. However, the brake ECU6may calculate the “pilot pressure increase time” by using an arithmetic expression. Further, the brake ECU6may calculate the “pilot pressure increase time” on the basis of the “accumulator pressure” detected in Step S23referring to the non-temperature corrected “pilot pressure increase time mapping data”, and may temperature correct the “pilot pressure increase time” on the basis of the brake fluid temperature detected in Step S22.

In the above-mentioned embodiment, the “pre-fill control” to increase the “pilot pressure” for the “pilot pressure increase time” (setting time) set based on the “servo pressure rising start time” is performed. However, “pre-fill control” to increase the “pilot pressure” for the “servo pressure rising start time” may be performed.

In the above-mentioned embodiment, the vehicular braking device1000is provided with the servo pressure rising start time measurement unit6bthat fully opens the pressure increase valve42, determines start of rise of the “servo pressure”, and measures the “servo pressure rising start time”. However, the servo pressure rising start time measurement unit6bmay not be provided in the vehicular braking device1000or a vehicle equipped with the vehicular braking device1000, and may be provided outside of the vehicular braking device1000or the vehicle. In such embodiment, before shipment of the vehicular braking device1000or the vehicle, or at putting the vehicular braking device1000or the vehicle into a maintenance shop, the servo pressure rising start time measurement unit6bprovided outside of the vehicular braking device1000or the vehicle may measure the “servo pressure rising start time”.

In the above-mentioned embodiment, in Step S25inFIG. 5, the brake ECU6fully opens the pressure increase valve42. However, the brake ECU6may open the pressure increase valve42at any degree of opening of non-full (for example, 80% of full). As illustrated inFIG. 8, when a supply current is a predetermined current A or less, the flow rate of the pressure increase valve42varies with respect to the supply current. However, when a supply current R1that causes the pressure increase valve42to fully open as well as a supply current R2that is the predetermined current A or more are supplied to the pressure increase valve42, the flow rate of the pressure increase valve42becomes constant with respect to the supply current. In this manner, the supply current R2that makes the flow rate constant may be supplied to the pressure increase valve42. Alternatively, the brake ECU6may amplify the operating amount of the brake pedal10detected by the stroke sensor71a few times (for example, 100 times) and opens the pressure increase valve42.

In the above-mentioned embodiment, the brake operating member for transmitting the operating force of the driver to the input piston13is the brake pedal10. However, the brake operating member is not limited to the brake pedal10, and may be a brake lever or a brake handle. As a matter of course, the vehicular braking device1000in this embodiment is applicable to a motorcycle and other vehicles to achieve the technical concept of the present invention.

REFERENCE SIGNS LIST