Jidosha Kiki Co., Ltd.

Other

Nissan Motor Company Limited

Bosch Braking Systems Co. Ltd.

Michio Kobayashi

Mamoru Sawada

Hiroyuki Oka

Masahiro Shimada

Yoshiyasu Takasaki

Hiroaki Niino

Yuzo Imoto

Hidefumi Inoue

Kazuya Maki

Ryuji Ohta

Osamu Kanazawa

Masahiro Ikeda

Morihiko Shimamura

Isao Kobayashi

Hiroshi Ohsaki

Satoru Watanabe

Masao Arino

Jun Kubo

Makoto Watanabe

Norio Fujiki

Hiroyuki Yamaga

Satoru Satoh

Yasuo Tsuyuki

Junichi Hirayama

Mitsuru Kakuda

Kazunori Senoh

Hiroshi Osaki

A brake system of the present invention comprises a brake operating means such as a brake pedal for carrying braking operation, a fluid variable stroke means which variably controls the stroke of the brake operating means by using fluid, and a braking force output means which is actuated by the operation of the brake operating means to produce braking forces. By manipulating the brake operating means , the braking force output means performs the braking operation. The traveling rang of the brake operating means i.e. the stroke can be changed variously by the fluid variable stroke means using fluid. Since the stroke of the brake pedal can be changed as mentioned above, a proper pedal stroke can be obtained.

Brake system

In a braking pressure intensifying master cylinder, as an input shaft ( ) travels forwards in a braking maneuver, a control valve ( ) is actuated to develop fluid pressure according to the input in a reaction chamber ( ) and a pressurized chamber ( ). A stepped spool ( ) as a part of the control valve travels such that force produced by the fluid pressure and spring force of a spring ( ) are balanced, whereby the stepped spool ( ) can function as a travel simulator. By changing the pressure receiving areas of the stepped spool and/or changing the spring force of the spring ( ), the travel characteristic of the input shaft ( ) as the input side can be freely changed independently from the output side, without influence on a master cylinder pressure as the output side of the braking pressure intensifying a master cylinder ( ). In addition, the master cylinder pressure can be intensified when necessary with a simple structure.

Braking pressure intensifying master cylinder

A hydraulic-pressure counter-force mechanism which produces a counter force when a brake booster is operated is made up of an input-side member slidable disposed within a valve body , a second constant-pressure chamber formed on the rear side of the input-side member and into which a pressure is introduced from a constant pressure chamber A, and a second constant-pressure chamber formed on the front side of the input-side member and into which a pressure is introduced from a variable pressure chamber B. The counter force from the hydraulic-pressure counter-force mechanism is reduced by an orifice passage as counter-force reducing means in rapid operation for brake.

The invention relates to a brake system including a brake booster. A pneumatic pressure operated brake booster VBB or a liquid pressure operated brake booster includes a valve mechanism which is urged by a force of depression applied to a brake pedal BP to switch a flow path to cause the brake booster to develop an output which depends on the magnitude of the force of depression. A solenoid SOL urges the valve mechanism in the same direction as or in the opposite direction from the force of depression. A controller ECU is responsive to a braking effort increase/decrease demand signal to increase or decrease the urging force which is applied by the solenoid to the valve mechanism, thus increasing or decreasing the output from the brake booster. An output from the brake booster can be freely controlled independently from the force of depression applied to the brake pedal in response to a braking effort increase/decrease demand. The arrangement is applicable to a wide variety of brake systems onboard a vehicle such as a regenerative brake unit, an engine brake or an exhaust gas brake unit or a brake assisting apparatus.

In a brake booster of the present invention, by depression of a brake pedal an input shaft travels to the left, a pedal input converter generates thrust, and a valve element moves to the left. A valve passage is shut off from a valve passage and a valve passage is connected to a valve passage so as to develop output pressure Pr at an output port of a control valve because of the pressure of a pressure source. The output pressure Pr is supplied to a wheel cylinder thereby actuating the brake. At this point, since the displacement of the input shaft required for operating the control valve is defined only by the converter the input side is not affected by the brake rigidity of a circuit from the control valve to the wheel cylinder The output pressure Pr of the control valve acts on the valve element through a first reaction receiving portion and is regulated to pressure proportional to the thrust of the converter The second reaction force is transmitted to a driver through a second reaction receiving portion The control of the output can be conducted during the operation regardless of the input of the input side and the respective characteristics can be varied without being affected by the output side.

Brake booster

In a brake fluid pressure boosting device of the present invention, by operation, an input shaft is moves forward to rotate a lever to actuate a control valve so that the control valve produce working fluid pressure corresponding to the input. The working fluid pressure is introduced into the power chamber By this working fluid pressure, the primary piston is actuated to develop master cylinder pressure. On the other hand, the fluid pressure of the power chamber is introduced into the first annular groove of the valve spool By the difference between pressure receiving areas of the first annular groove the valve spool is subjected to rightward force. The position of the pivot of the lever is fixed and the valve spool is controlled in such a manner that the force applied to the valve spool and the spring force of the spool return spring balances with the input, thereby exhibiting the function as a stroke simulator. Because of this function as a stroke simulator, the stroke characteristic on the input side can be changed without affecting the output side.

Fluid pressure boosting device and brake system employing the same

A counter-force mechanism (,), which produces a counter force when a brake booster is operated, is made up of an input-side member (,) slidably disposed within a valve body (,), a second constant-pressure chamber (,) formed on the rear side of the input-side member and into which a pressure is introduced from a constant pressure chamber (A), and a second constant-pressure chamber (,) formed on the front side of the input-side member and into which a pressure is introduced from a variable pressure chamber (B). The counter force from the counter-force mechanism (,) is reduced by an orifice passage (,) as a counter-force reducing means in rapid operation of the brake.

A fluid pressure boosting device of the present invention performs jumping action at a higher servo ratio until fluid pressure in a power chamber (,) reaches a first predetermined value and a rear end (,e) of a reaction piston (,)comes in contact with a step of an input shaft (,). Since a switching valve is set in a first position I until the fluid pressure in the power chamber (,) reaches a second predetermined pressure, a reaction chamber (,) is connected to the reservoir (,) so as to be at atmospheric pressure. In this state, the normal brake control at a lower servo ratio is performed. As the fluid pressure in the power chamber (,) reaches a second predetermined value, the switching valve is set in a second position II by the fluid pressure so that the pressurized fluid in the power chamber is introduced into the reaction chamber (,). The fluid pressure in the reaction chamber,acts on the step between the reaction piston (,) and the input shaft (,) so that the servo ratio becomes higher. Then, the servo control at a higher servo ratio is performed. The fluid pressure boosting device can be provided with the reversed two-stage servo characteristic, so with simple structure, output larger than the normal output can be obtained when input exceeds a predetermined value.

Fluid pressure boosting device and brake pressure boosting system employing the device

The collar 13 for slidably supporting and guiding a valve body of the control valve 55 of the hydraulic pressure type booster 1 is press-fitted into the small diameter portion 9a of the stepped hole 9 of the power piston 8. The valve seat member 10 of the control valve 55 is also press-fitted into the small diameter portion 9a. Further, the small diameter protrusion 6b of the stepped cylindrical protrusion 6a of the plug 6, which divides the power chamber 25, is also press-fitted into the small diameter portion 4a of the stepped hole 4 of the housing 3. In the cylindrical member 17 in which the second valve seat 17a of the control valve 55 is formed, the stopper 17b to restrict a limit of retraction of the input shaft 18 is integrally formed. Further, the cylindrical fixing member 11 to fix the flange 10a of the valve seat member 10 is fixed to the power piston 8 with C ring 12 in the axial direction.

Hydraulic pressure type booster

In a brake-pressure producing device of the present invention, a power piston 10 of a hydraulic booster 2 comprises a stepped piston including a large-diameter portion 10a on which fluid pressure of a power chamber 30 is exerted and a small-diameter portion 10b having the same diameter as the master cylinder piston 53. Both the pistons 10, 53 are interlocked with each other through an aligning rod 62. The pressurized fluid of the power chamber 30 is introduced into an annular chamber 51 formed on the circumference of the small-diameter portion 10b and the fluid pressure of the pressurized fluid is exerted on a stepped portion 10c between the large-diameter portion 10a and the small-diameter portion 10b in the direction opposite to the direction of the fluid pressure of the power chamber 30. When the braking operation is performed, the fluid pressure in the power chamber 30 introduced into wheel cylinders 33, 34 relating to one of the circuits and the master cylinder pressure introduced into wheel cylinders 58, 59 relating to the other circuit balance to be equal to each other, thereby uniformly and properly distributing braking forces to the respective wheel cylinders.

Brake-pressure producing device

In a hydraulic brake system of the present invention, the communication between a power chamber 30 of a hydraulic booster 2 and wheel cylinders (WCY) 58, 59 is allowed by a switching valve 64 when fluid pressure of an accumulator (ACC) 46 exceeds predetermined pressure. During braking operation, the fluid pressure of the ACC 46 introduced in the power chamber 30 is introduced directly to the WCYs 58, 59, thereby rapidly actuating brakes and thus improving the response. When the fluid pressure of the ACC 46 is less than the predetermined pressure, the communication between a fluid chamber 57 of a master cylinder (MCY) 3 and the WCYs 58, 59 is allowed by the switching valve 64. During braking operation, MCY pressure developed by a MCY piston 53 operated by an input shaft 21 through a power piston 10 is introduced into the WCYs 58, 59 through the switching valve 64. The brakes can securely work even when the fluid pressure of the ACC 46 is less than the predetermined pressure.

Hydraulic brake system

An improvement of a liquid pressure booster provided with a reaction piston is disclosed. A guide formed on a housing (plug) is caused to project into a tubular section of a power piston. A reaction piston is slidably supported by the guide, and an input shaft is slidably supported by the reaction piston. A spring which urges the reaction piston is disposed in a clearance defined between the outer periphery of the guide and the inner periphery of the tubular section of the power piston. In this manner, the guide, a sliding portion of the reaction piston, a sliding portion of the input shaft and the spring can be disposed radially of each other while overlapping each other in the axial direction to minimize the axial size of the liquid pressure booster.

Liquid pressure booster

The invention relates to a hydraulic pressure booster which can be used to perform servo control of input and output at the preset servo ratio in, for example, a brake booster. In particular, the invention relates to a hydraulic pressure booster, which is designed to reduce the loss stroke of an input shaft in the initial stage of operation. This can be achieved by providing a stopper which directly abuts the input shaft when it is non-operational and which maintains the input shaft at the preset advance position separated from the detent in relation to the power piston.

Hydraulic pressure booster

A power piston assembly of a brake booster includes a power piston including a stepped cylindrical portion having a through-hole. A diaphragm is provided on the rear surface of the power piston. The diaphragm has an inner-circumferential bead which is connected to the rear end of the cylindrical portion of the power piston. The valve body has a stepped cylindrical portion which engages with the stepped portion of the power piston and is disposed in the through-hole of the power piston with the diaphragm bead in sealing contact with the valve body. A retainer is pressed fitted into the cylindrical portion of the power piston so as to abut the front surface of the valve body to secure the valve body in close contact with the power piston.

Power piston assembly of a brake booster

A parking maintaining apparatus includes a solenoid-operated open/close valve which opens or closes a constant pressure passage providing a communication between a valve mechanism and a constant pressure chamber of a brake booster. A relief valve is provided which relieves a pressure within the constant pressure passage into the constant pressure chamber when such pressure exceeds a given value. The provision of the relief valve allows the pressure within a variable pressure chamber to be maintained at or below the given value through the valve mechanism under a parking maintaining condition, whereby the pressure within the variable pressure chamber can be rapidly displaced as the parking maintaining condition is to be terminated, thus eliminating a partly braked condition.

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Higashimatsuyama, Japan

Michio Kobayashi