JP2009161136A - Brake system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a BBW type brake system including two hydraulic pressure lines capable of detecting that a third front cup seal of a front piston is mistakenly not installed. <P>SOLUTION: When a first hydraulic line continuous with a rear liquid chamber 39A fails and is made to open atmosphere at the time of failure of a motor cylinder 23, a forward-facing third front cup seal C5 prevents a brake hydraulic pressure generated by a master cylinder from leaking out from a front supply port 49B through the rear liquid chamber 39A, and a stopper 51 prevents a front piston 38B from moving rearward due to a pressure of a front liquid chamber 39B, thus braking by a second hydraulic pressure line continuous with the front liquid chamber 39B of the motor cylinder 23 can be ensured. When the third front cup seal C5 is mistakenly not installed, brake fluid generated by the master cylinder when a brake pedal is depressed leaks out of an atmospheric chamber 52 arranged between a second front cup seal C4 and the third front cup seal C5, increasing the brake pedal stroke, thus detecting that the cup seal is mistakenly not installed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a brake device including a master cylinder that generates a brake fluid pressure by a driver's braking operation and an electrical fluid pressure generating unit that generates a brake fluid pressure by an electrically controllable actuator.

  A so-called BBW (brake-by-wire) is performed in which the braking operation of the driver is converted into an electric signal to operate the electric hydraulic pressure generating means, and the wheel cylinder is operated with the brake hydraulic pressure generated by the electric hydraulic pressure generating means. ) Type brake device is known from US Pat.

  By the way, in this kind of BBW type brake device, when the electric hydraulic pressure generating means fails, the brake hydraulic pressure generated by the master cylinder is directly transmitted to the wheel cylinder to brake the wheel, thereby fail-safe function. To come to show. Moreover, the master cylinder is a tandem type that supplies brake hydraulic pressure separately to the two hydraulic systems, and even if a leak occurs in one hydraulic system, one of the wheels can be braked by the other hydraulic system. It is like that.

  FIG. 5 shows the structure of a conventional electric hydraulic pressure generating means (motor cylinder 23). A rear piston 38A and a front piston urged in a backward direction by a pair of return springs 37A and 37B inside a cylinder body 36. The part piston 38B is slidably disposed, and a rear liquid chamber 39A is defined on the front surface of the rear piston 38A, and a front liquid chamber 39B is defined on the front surface of the front piston 38B.

  A rear reservoir chamber 38a is formed on the outer periphery of the rear piston 38A to prevent air from entering the rear liquid chamber 39A, and air is prevented from entering the front liquid chamber 39B on the outer periphery of the front piston 38B. A front reservoir chamber 38b is formed. The rear inlet port 40A of the rear liquid chamber 39A and the rear supply port 49A of the rear reservoir chamber 38a communicate with the master cylinder, and the rear outlet port 41A of the rear liquid chamber 39A communicates with the wheel cylinder. The front inlet port 40B of the front liquid chamber 39B and the front supply port 49B of the front reservoir chamber 38b communicate with the master cylinder, and the front outlet port 41B of the front liquid chamber 39B communicates with the wheel cylinder.

A rear first cup seal C1 is provided forward (at the front end of the rear piston 38A so as to exhibit a sealing function during advance), and a rear second cup seal C2 is provided forward at the rear end of the rear piston 38A. A front first cup seal C3 is provided forward at the front end of the front piston 38B, and a front second cup seal C4 is provided rearward at the rear end of the front piston 38B (so as to exhibit a sealing function when moving backward). Is provided.
JP 2003-137084 A

  By the way, in the structure of the conventional motor cylinder 23, when the wheel cylinder is operated with the brake fluid pressure generated by the motor cylinder 23 and the master cylinder is generated, the front supply port 49B is connected to the master cylinder. When the first hydraulic system fails and the rear fluid chamber 39A of the motor cylinder 23 is released to the atmosphere, the brake fluid pressure generated in the master cylinder is changed to the front supply port 49B → the front reservoir chamber 38b → the front portion. There is a possibility that leakage will occur in the path from the second cup seal C4 to the rear liquid chamber 39A, and the second hydraulic system connected to the front liquid chamber 39B will also fail at the same time.

  Therefore, according to Japanese Patent Application No. 2008-2708 filed on the same day as the present application, the present applicant has a front third cup seal disposed forward and adjacent to the front of the front second cup seal of the front piston of the motor cylinder. And a brake with a stopper that restricts the retreat limit of the front piston. According to this brake device, the brake fluid pressure generated by the master cylinder is prevented from leaking from the front supply port via the rear fluid chamber by the front third cup seal, and the front fluid chamber is pressurized by the pressure of the front fluid chamber. The piston can be prevented from moving backward by the stopper, and braking by the second hydraulic system connected to the front fluid chamber of the motor cylinder can be ensured.

  However, when the brake device is configured as described above, if it is forgotten to attach the front third cup seal at the time of assembly, it can be known until the first hydraulic system actually fails. Therefore, there is a possibility that braking by the second hydraulic system cannot be ensured by forgetting to attach the front third cup seal.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to make it possible to detect forgetting to attach the front third cup seal of the front piston in a BBW brake device having two hydraulic systems. .

  To achieve the above object, according to the first aspect of the present invention, a master cylinder that generates brake fluid pressure by a driver's braking operation, and an actuator that communicates with the master cylinder and is electrically controllable. A hydraulic fluid pressure generating means having a rear fluid chamber and a front fluid chamber for generating a brake fluid pressure, and a plurality of wheels for communicating with the rear fluid chamber and the front fluid chamber to generate a braking force for braking the wheel. A brake device that operates a wheel cylinder with a brake hydraulic pressure generated by a master cylinder when the electric hydraulic pressure generating means fails, wherein the electric hydraulic pressure generating means is advanced by an actuator to move the rear liquid Rear piston and front piston that generate brake fluid pressure in the chamber and front fluid chamber, respectively, and formed in the rear fluid chamber and connected to the master cylinder A rear inlet port connected to the wheel cylinder, a rear outlet port connected to the wheel cylinder, a rear supply port formed adjacent to the rear inlet port and connected to the master cylinder, and a front liquid chamber formed to connect to the master cylinder A front outlet port connected to the front inlet port and the wheel cylinder, a front supply port formed adjacent to the rear of the front inlet port and connected to the master cylinder, and disposed forwardly at the front end of the rear piston Rear first cup seal, rear second cup seal disposed forward at the rear end of the rear piston, front first cup seal disposed forward at the front end of the front piston, and rear end of the front piston The front second cup seal disposed rearward and the front piston disposed adjacent to the front of the front second cup seal of the front piston. What provided the atmospheric pressure chamber between the front 2nd cup seal and front 3rd cup seal of a front piston in what provided the 3rd cup seal and the stopper which controls the retreat limit of a front piston. A featured braking device is proposed.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, a relief valve is provided that opens when a pressure of a predetermined value or more is generated in the atmospheric pressure chamber. A braking device is proposed.

  The motor cylinder 23 according to the embodiment corresponds to the electrical hydraulic pressure generating means of the present invention.

  According to the configuration of the first aspect, when the wheel cylinder is operated with the brake hydraulic pressure generated by the master cylinder due to the failure of the electric hydraulic pressure generating means, the second fluid chamber connected to the rear fluid chamber of the electric hydraulic pressure generating means is provided. When the first hydraulic system fails and the atmosphere is released, braking is performed with the brake hydraulic pressure of the second hydraulic system transmitted from the master cylinder to the wheel cylinder through the front hydraulic chamber of the electrical hydraulic pressure generating means. Is called. At this time, a forward-facing front third cup seal is disposed between the front supply port communicating with the master cylinder and the rear liquid chamber opened to the atmosphere due to a failure, and a stopper for restricting the backward limit of the rear piston is provided. Since the brake fluid pressure generated by the master cylinder leaks from the front supply port through the rear fluid chamber by the front third cup seal, the front piston is controlled by the pressure of the front fluid chamber. Is prevented by a stopper, and braking by the second hydraulic system connected to the front liquid chamber of the electric hydraulic pressure generating means can be secured.

  When the front third cup seal is not functioning due to forgetting to install, etc., the brake pedal generated by the master cylinder when the driver steps on the brake pedal leaks into the atmospheric pressure chamber, so the brake pedal stroke increases gradually. To do. Thus, the driver can know that the front third cup seal is not functioning, and before the first hydraulic system fails and the second hydraulic system needs to be backed up. Measures can be taken.

  According to the second aspect of the present invention, since the relief valve is provided that opens when a pressure higher than a predetermined value is generated in the atmospheric pressure chamber, the brake fluid pressure generated by the master cylinder when the driver steps on the brake pedal. If the pressure exceeds the specified value, the relief valve opens and the brake fluid leaks all at once, causing the brake pedal stroke to increase sharply. Therefore, the driver ensures that the front third cup seal is not functioning. I can know.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 3 show a first embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram in a normal state of a vehicle brake device, and FIG. 2 is an abnormal hydraulic circuit corresponding to FIG. FIG. 3 and FIG. 3 are enlarged views of essential parts of FIG.

  As shown in FIG. 1, the tandem master cylinder 11 includes two fluid chambers 13A and 13B that output brake fluid pressure in accordance with the pedaling force of the driver stepping on the brake pedal 12, and one fluid chamber 13A is provided. Is connected to the wheel cylinders 16 and 17 of the disc brake devices 14 and 15 of the left front wheel and the right rear wheel, for example, via the liquid paths Pa, Pc, Pd and Pe, and the other liquid chamber 13B is connected to the liquid paths Qa and Qc. , Qd, Qe, for example, are connected to the wheel cylinders 20, 21 of the disc brake devices 18, 19 of the right front wheel and the left rear wheel.

  The motor cylinder 23 is disposed between the liquid paths Pa and Qa and the liquid paths Pc and Qc, and the ABS device 24 is disposed between the liquid paths Pc and Qc and the liquid paths Pd and Pe; Qd and Qe.

  A stroke simulator 26 is connected to the liquid paths Ra and Rb branched from the liquid path Qa via a reaction force permission valve 25 which is a normally closed solenoid valve. The stroke simulator 26 is a cylinder 27 in which a piston 29 urged by a spring 28 is slidably fitted, and a liquid chamber 30 formed on the side opposite to the spring 28 of the piston 29 communicates with a liquid path Rb. .

  The actuator 31 of the motor cylinder 23 includes a drive bevel gear 33 provided on the output shaft of the electric motor 32, a driven bevel gear 34 that meshes with the drive bevel gear 33, and a ball screw mechanism 35 that is operated by the driven bevel gear 34. A pair of pistons 38A and 38B urged in a backward direction by a pair of return springs 37A and 37B are slidably disposed in a cylinder body 36 of the motor cylinder 23, and a rear liquid chamber is provided in front of the rear piston 38A. 39A is defined, and a front liquid chamber 39B is defined on the front surface of the front piston 38B.

  As is apparent from FIGS. 1 and 3, the rear liquid chamber 39A communicates with the liquid path Pa via the rear inlet port 40A and the rear supply port 49A, and communicates with the liquid path Pc via the rear outlet port 41A. . The front liquid chamber 39B communicates with the liquid path Qa through the front inlet port 40B and the front supply port 49B, and communicates with the liquid path Qc through the front outlet port 41B.

  A rear first cup seal C1 is provided forward (at the front end of the rear piston 38A so as to exhibit a sealing function during advance), and a rear second cup seal C2 is provided forward at the rear end of the rear piston 38A. A front first cup seal C3 is provided forward at the front end of the front piston 38B, and a front second cup seal C4 is provided rearward at the rear end of the front piston 38B (so as to exhibit a sealing function during reverse travel). Provided. Furthermore, a front-facing front third cup seal C5 is provided in front of the front second cup seal C4 of the front piston 38B.

  A rear reservoir chamber 38a sandwiched between the rear first and second cup seals C1 and C2 is formed at an intermediate portion of the rear piston 38A, and a rear supply port 49A communicates with the rear reservoir chamber 38a. A front reservoir chamber 38b sandwiched between the front first and third cup seals C3 and C5 is formed at an intermediate portion of the front piston 38B, and a front supply port 49B communicates with the front reservoir chamber 38b. To do.

  The rear liquid chamber 39A is sandwiched between the front-facing rear first cup seal C1 and the rear-facing front second cup seal C4 to ensure liquid tightness, and the backward liquid leakage from the rear reservoir chamber 38a is forward-facing rear. It is blocked by the second cup seal C2. The front liquid chamber 39B is liquid-tight by the forward-facing front first cup seal C3, and backward liquid leakage from the front reservoir chamber 38b is prevented by the forward-facing front third cup seal C5.

  An atmospheric pressure chamber 52 is formed between the front second cup seal C4 and the front third cup seal C5 of the front piston 38B, and this atmospheric pressure chamber 52 is connected via the atmospheric pressure port 53 and the liquid path Rc. The reservoir of the master cylinder 11 is communicated with 50.

  A long hole 38c extending in the front-rear direction is formed in the front piston 38B, and a stopper 51 made of a pin fixed to the cylinder body 36 penetrates the long hole 38c slidably. The length of the long hole 38c is set to a length that does not contact the stopper 51 during normal operation of the motor cylinder 23, that is, a length that does not hinder the movement of the front piston 38B.

  When the motor cylinder 23 is not operated, the rear first cup seal C1 of the rear piston 38A is positioned immediately behind the rear inlet port 40A. When the rear piston 38A is slightly advanced, the rear first cup seal C1 is moved to the rear inlet port 40A. And brake fluid pressure is generated in the first fluid chamber 39A. When the motor cylinder 23 is not operated, the front first cup seal C3 of the front piston 38B is located immediately after the front inlet port 40B, and when the front piston 38B slightly advances, the front first cup seal C3 is moved forward. Passes through the front inlet port 40B, and brake fluid pressure is generated in the front fluid chamber 39B.

  When the electric motor 32 is driven in one direction, the rear and front pistons 38A and 38B move forward through the drive bevel gear 33, the driven bevel gear 34, and the ball screw mechanism 35, and the rear and front connected to the fluid paths Pa and Qa. The brake fluid pressure is generated in the rear and front fluid chambers 39A and 39B at the moment when the part inlet ports 40A and 40B are closed, and the brake fluid pressure is supplied to the fluid passages Pc and Pc via the rear and front outlet ports 41A and 41B. Qc can be output.

  As shown in FIG. 1, the structure of the ABS device 24 is well known, and the system of the left front wheel and right rear wheel disc brake devices 14, 15 and the system of the right front wheel and left rear wheel disc brake devices 18, 19 are shown. Are provided with the same structure. As a representative example, the system of the disc brake devices 14 and 15 for the left front wheel and the right rear wheel will be described. Between the liquid passage Pc and the liquid passages Pd and Pe, in-valves 42 and 42 made up of a pair of normally open solenoid valves are arranged. In addition, out valves 44 and 44, which are normally closed electromagnetic valves, are disposed between the fluid paths Pd and Pe on the downstream side of the in valves 42 and 42 and the reservoir 43. A hydraulic pump 47 sandwiched between a pair of check valves 45 and 46 is disposed between the reservoir 43 and the fluid path Pc. The hydraulic pump 47 is driven by an electric motor 48.

  An electronic control unit (not shown) that controls the operation of the reaction force permission valve 25, the motor cylinder 23, and the ABS device 24 includes a hydraulic pressure sensor Sa that detects the brake hydraulic pressure generated by the master cylinder 11, a disc brake device 18, A hydraulic pressure sensor Sb that detects the brake hydraulic pressure transmitted to the vehicle 19 and a wheel speed sensor Sc that detects the wheel speed of each wheel are connected.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  When the system functions normally, the reaction force permission valve 25 formed of a normally closed solenoid valve is excited and opened. In this state, when the hydraulic pressure sensor Sa provided in the liquid path Qa detects the depression of the brake pedal 12 by the driver, the actuator 31 of the motor cylinder 23 is operated, and the rear and front pistons 38A and 38B move forward. Brake fluid pressure is generated in the rear and front fluid chambers 39A and 39B. The brake fluid pressure is transmitted to the wheel cylinders 16, 17, 20, and 21 of the disc brake devices 14, 15, 18, and 19 via the in-valves 42 that are opened by the ABS device 24, and brakes each wheel.

  When the rear and front pistons 38A and 38B of the motor cylinder 23 are slightly advanced, the rear and front inlet ports 40A and 40B are closed, and the fluid paths Pa and Qa communicate with the rear and front liquid chambers 39A and 39B. As a result, the brake fluid pressure generated by the master cylinder 11 is not transmitted to the disc brake devices 14, 15, 18, 19. At this time, the brake fluid pressure generated in the other fluid chamber 13B of the master cylinder 11 is transmitted to the fluid chamber 30 of the stroke simulator 26 via the opened reaction force permitting valve 25, and the piston 29 resists the spring 28. Thus, the stroke of the brake pedal 12 can be allowed and a pseudo pedal reaction force can be generated to eliminate the driver's uncomfortable feeling.

  Then, the brake fluid pressure by the motor cylinder 23 detected by the fluid pressure sensor Sb provided in the fluid passage Qc has a magnitude corresponding to the brake fluid pressure by the master cylinder 11 detected by the fluid pressure sensor Sa provided in the fluid passage Qa. As described above, by controlling the operation of the actuator 31 of the motor cylinder 23, it is possible to cause the disc brake devices 14, 15, 18, 19 to generate a braking force corresponding to the pedaling force input to the brake pedal 12 by the driver.

  During the braking described above, when it is detected that the slip ratio of any wheel has increased due to the output of the wheel speed sensor Sc..., The motor cylinder 23 is maintained in an operating state. The ABS device 24 is operated in the state to prevent the wheels from being locked.

  That is, when a predetermined wheel tends to be locked, the in-valve 42 connected to the wheel cylinder of the disc brake device of the wheel is closed and the out-valve 44 is opened with the transmission of the brake fluid pressure from the motor cylinder 23 blocked. The wheel does not lock by performing a pressure reducing action to release the brake fluid pressure of the wheel cylinder to the reservoir 43 and a holding action to close the out valve 44 and hold the brake fluid pressure of the wheel cylinder. So as to reduce the braking force.

  As a result, when the wheel speed recovers and the slip ratio decreases, the braking force of the wheel is increased by opening the in-valve 42 and increasing the brake fluid pressure of the wheel cylinder. When the wheel becomes locked again by this pressure increasing action, the pressure reduction, holding, and pressure increasing are executed again, and the maximum braking force can be generated while suppressing the wheel lock by repeating the operation. In the meantime, the brake fluid that has flowed into the reservoir 43 is returned to the upstream fluid paths Pc and Qc by the hydraulic pump 47.

  When the motor cylinder 23 becomes inoperable due to a power failure or the like, braking is performed by the brake fluid pressure generated by the master cylinder 11 instead of the brake fluid pressure generated by the motor cylinder 23.

  When the power supply fails, as shown in FIG. 2, the reaction force permission valve 25 made of a normally closed solenoid valve is automatically closed, and the in-valve 42 made of a normally open solenoid valve is automatically opened. The out valves 44, which are normally closed solenoid valves, are automatically closed. In this state, the brake fluid pressure generated in the fluid chambers 13A and 13B of the master cylinder 11 is not absorbed by the stroke simulator 26 and passes through the rear portion of the motor cylinder 23, the front fluid chambers 39A and 39B, and the in-valves 42. Thus, the wheel cylinders 16, 17, 20, and 21 of the disc brake devices 14, 15, 18, and 19 of each wheel can be operated to generate a braking force without any trouble.

  At the time of the above-described abnormality, the disc brakes for the left front wheel and the right rear wheel from the one fluid chamber 13A of the master cylinder 11 through the fluid passage Pa, the rear fluid chamber 39A of the motor cylinder 23, the fluid passage Pc and the fluid passages Pd and Pe. When the first hydraulic system connected to the wheel cylinders 16, 17 of the devices 14, 15 fails and the brake fluid leaks, the fluid path Qa from the other fluid chamber 13 B of the master cylinder 11, the front part of the motor cylinder 23 The second hydraulic system connected to the wheel cylinders 20 and 21 of the disc brake devices 18 and 19 of the right front wheel and the left rear wheel is operated via the liquid chamber 39B, the liquid path Qc, and the liquid paths Qd and Qe. A braking force can be generated on at least two of the wheels to enable fail-safety.

  At this time, in the conventional example shown in FIG. 5, when the first hydraulic system fails and the rear fluid chamber 39A of the motor cylinder 23 is released to the atmosphere, the brake fluid generated in the fluid chamber 13B of the master cylinder 11 is released. The pressure leaks through the path of the front supply port 49B → the front reservoir chamber 38b → the front second cup seal C4 → the rear liquid chamber 39A, and the second hydraulic system connected to the front liquid chamber 39B also loses at the same time. There is a possibility of falling.

  However, in the first embodiment shown in FIG. 3, when the first hydraulic system fails and the brake fluid leaks at the time of abnormality, the brake fluid leaks from the other fluid chamber 13B of the master cylinder 11 via the fluid channel Qa. The brake fluid pressure is transmitted to the front fluid chamber 39B and the front reservoir chamber 38b of the motor cylinder 23. At this time, since the front reservoir chamber 38b is disconnected from the rear liquid chamber 39A opened to the atmosphere by the front third cup seal C5, the brake fluid pressure in the front liquid chamber 39B is passed through the rear liquid chamber 39A. And the front piston 38B is prevented from retreating by the contact between the long hole 38c and the front end of the stopper 51, so that the volume of the front liquid chamber 39B is prevented from expanding without limit. . Therefore, the brake fluid pressure is normally generated in the front fluid chamber 39B, and the second fluid pressure system connected to the front fluid chamber 39B does not fail simultaneously with the first fluid pressure system.

  By the way, in the conventional case, when the front third cup seal C5 is forgotten to be attached when the motor cylinder 23 is assembled (or when the front third cup seal C5 is damaged and the sealing performance is lost), the first When the hydraulic system fails and backup by the second hydraulic system becomes necessary, it becomes clear that the front third cup seal C5 is not attached for the first time because the backup is impossible. There was a problem.

  On the other hand, according to the present embodiment, the atmospheric pressure chamber 52 is formed between the front second cup seal C4 and the front third cup seal C5 of the front piston 38B. 12, a part of the brake fluid sent from the fluid chamber 13 </ b> B of the master cylinder 11 is not absorbed by the stroke simulator 26, and the fluid path Qa, the front supply port 49 </ b> B, the front reservoir chamber 38 b, and forget to install In addition, the reservoir leaks to 50 via the position of the front third cup seal C5, the atmospheric pressure chamber 52 and the liquid path Rc. As a result, the stroke of the brake pedal 12 gradually increases by the amount of brake fluid that has leaked, so that the driver can know that the front third cup seal C5 is not functioning, and a backup is required. It becomes possible to attach the front third cup seal C5 before this occurs.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  The atmospheric pressure chamber 52 of the first embodiment communicates with the reservoir 50, but the atmospheric pressure chamber 52 of the second embodiment communicates with the atmosphere via a relief valve 54. When the driver steps on the brake pedal 12 and the brake fluid pressure generated in the fluid chamber 13B of the master cylinder 11 exceeds a predetermined value, the relief valve 54 opens and the brake fluid leaks suddenly. By rapidly increasing the stroke, the driver can surely know that the front third cup seal C5 is not functioning.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

For example, although the brake device of the embodiment includes the ABS device 24, the present invention can also be applied to a brake device that does not have the ABS device 24.
The stopper 51 is not limited to the one that engages with the long hole 38c of the front piston 38B, and a stopper having an appropriate structure can be adopted.

Hydraulic circuit diagram of normal state of vehicle brake device according to first embodiment Hydraulic circuit diagram at the time of abnormality corresponding to FIG. 1 is an enlarged view of the main part of FIG. The figure corresponding to the said FIG. 3 based on 2nd Embodiment. Cross section of conventional motor cylinder

Explanation of symbols

11 Master cylinder 16 Wheel cylinder 17 Wheel cylinder 20 Wheel cylinder 21 Wheel cylinder 23 Motor cylinder (electrical fluid pressure generating means)
38A Rear piston 38B Front piston 39A Rear fluid chamber 39B Front fluid chamber 40A Rear inlet port 40B Front inlet port 41A Rear outlet port 41B Front outlet port 49A Rear supply port 49B Front supply port 51 Stopper 52 Atmospheric pressure chamber 54 Relief valve C1 Rear first cup seal C2 Rear second cup seal C3 Front first cup seal C4 Front second cup seal C5 Front third cup seal

Claims (2)

A master cylinder (11) that generates a brake fluid pressure by a driver's braking operation;
Electrical hydraulic pressure generating means (39A) having a rear fluid chamber (39A) and a front fluid chamber (39B) communicating with the master cylinder (11) and generating brake fluid pressure by an electrically controllable actuator (31) 23)
A plurality of wheel cylinders (16, 17, 20, 21) that generate braking force to brake the wheels in communication with the rear liquid chamber (39A) and the front liquid chamber (39B), respectively.
A brake device for operating a wheel cylinder (16, 17, 20, 21) with a brake hydraulic pressure generated by a master cylinder (11) when an electric hydraulic pressure generating means (23) fails.
The electrical hydraulic pressure generating means (23)
A rear piston (38A) and a front piston (38B) which are advanced by an actuator (31) to generate brake fluid pressure in the rear liquid chamber (39A) and the front liquid chamber (39B), respectively;
A rear inlet port (40A) formed in the rear liquid chamber (39A) and connected to the master cylinder (11) and a rear outlet port (41A) connected to the wheel cylinders (16, 17);
A rear supply port (49A) formed adjacent to the rear of the rear inlet port (40A) and connected to the master cylinder (11);
A front inlet port (40B) connected to the master cylinder (11) formed in the front liquid chamber (39B) and a front outlet port (41B) connected to the wheel cylinders (20, 21);
A front supply port (49B) formed adjacent to the rear of the front inlet port (40B) and connected to the master cylinder (11);
A rear first cup seal (C1) disposed forwardly at the front end of the rear piston (38A);
A rear second cup seal (C2) disposed forward at the rear end of the rear piston (38A);
A front first cup seal (C3) disposed forward at the front end of the front piston (38B);
A front second cup seal (C4) disposed rearward at the rear end of the front piston (38B);
A front third cup seal (C5) disposed forward and adjacent to the front of the front second cup seal (C4) of the front piston (38B);
A stopper (51) for restricting the retreat limit of the front piston (38B);
In those with
Brake device characterized in that an atmospheric pressure chamber (52) is provided between the front second cup seal (C4) and the front third cup seal (C5) of the front piston (38B).   The brake device according to claim 1, further comprising a relief valve (54) that opens when a pressure equal to or higher than a predetermined value is generated in the atmospheric pressure chamber (52).

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