Other

Bosch Braking Systems Co. Ltd.

Jidosha Kiki Co., Ltd.

Bosch Automotive Systems Corporation

Hiroyuki Oka

Yoshiyasu Takasaki

Mamoru Sawada

Hidefumi Inoue

Michio Kobayashi

Masahiro Shimada

Yuzo Imoto

Hiroaki Niino

Kazuya Maki

Isao Kobayashi

Osamu Kanazawa

Masahiro Ikeda

Hiroshi Ohsaki

Makoto Watanabe

Satoru Watanabe

Hiroyuki Yamaga

Yasushi Mori

Junichi Hirayama

Mitsuru Kakuda

Hiroshi Osaki

A tubular memberis slidably fitted into a valve body, and is formed with a vacuum valve seat. The tubular member, a valve plungerand the valve bodyare maintained in their inoperative positions shown by abutment against a key member. A holderis formed with a tapered surfaceto assist in allowing an elastic deformation of a reaction disc. Immediately after the commencement of operation of a valve mechanismas an input shaftis driven forward, the input shaftand the tubular memberare maintained in their inoperative positions until a rear end face of a variable pressure passageabuts against the key member. The operating stroke of an input shaftcan be chosen to be less than the operating stroke of an output shaftwhile preventing the jumping value from increasing to an excessively high value.

Negative pressure brake booster

In a fluid pressure boosting device of the present invention, a control valve is composed of a supply valve and a discharge valve the supply valve comprises an annular valve cone of a poppet type and a first valve seat and the discharge valve comprises an annular valve cone of a poppet type and a second valve seat Inside a rear end portion of a primary piston of a master cylinder a reaction disk made of an elastic material such as rubber is fitted. An input shaft penetrating the control valve is arranged such that, in the inoperative state, an end thereof confronts the reaction disk with a predetermined space therebetween and, in the operative state, the end comes in contact with said reaction disk so that a reaction force is transmitted to the input shaft The passage for discharging hydraulic fluid of the power chamber is composed of annular passages Therefore, a fluid pressure boosting device of a center valve type can be provided of which the structure for attaining the jumping characteristic and the structure of passage for discharging hydraulic fluid are simple.

Fluid pressure boosting device

A brake fluid pressure generating device includes a first valve element connected to an input shaft, a first force device connected to the first valve element to provide a counter force relative to a force applied to the first valve, a second valve element situated adjacent to the first valve element, a power cylinder unit actuated by the first valve, a second force device situated between a power cylinder unit and the second valve element to move the second valve element, and a third force device connected to the second valve element to provide a counter force relative to a force applied to the second valve. A master cylinder is connected to the power piston to generate a master cylinder pressure to thereby output a regulated control valve output pressure. A desired stroke characteristic of the brake can be obtained.

Brake fluid pressure generating device

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

As the primary piston is driven forward, a cup seal moves forwardly of a communication path in a first sleeve to interrupt a communication between a first reservoir chamber and the first liquid pressure chamber thus generating a liquid pressure in the first liquid pressure chamber As the secondary piston is driven forward, a cup seal moves forwardly of a communication path interrupting a communication between a second reservoir chamber and a second liquid pressure chamber thus generating a liquid pressure in the second liquid pressure chamber The invention provides a master cylinder which is simple in construction and inexpensive to manufacture.

Master cylinder

A brake system including an intensifying arrangement which allows a master cylinder pressure to be intensified by feeding a discharge pressure from a pump to an intensifying chamber. The brake system includes a master cylinder having a primary piston, on the rear portion of which a sleeve is fitted, with a spool valve slidably fitted into the sleeve. The spool valve has a rear end which abuts against the bottom of a bottomed opening formed in an input shaft. The invention allows a misalignment between the axes of the primary piston and the input shaft.

A brake system including a negative pressure booster, a master cylinder of tandem type and an intensifying arrangement. The intensifying arrangement defines an intensifying chamber disposed rearward of a primary piston, a pump for supplying a braking liquid to the intensifying chamber, and a reaction piston and a sleeve for controlling the pressure of the braking liquid which is supplied to the intensifying chamber. As a brake pedal is depressed and the intensifying arrangement is actuated, a sum of an urging force from the negative pressure booster and an urging force from the intensifying arrangement operates the primary piston to develop a master cylinder pressure. The sum is proportional to the input or a force depressing the brake pedal. In this manner, a simple arrangement assures a satisfactory booster function even after the negative pressure booster has reached a full load point or the limit of its assistance or in the event of the failure of a source of a negative pressure for the negative pressure booster.

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

In a brake boosting system the present invention, as it is decided that brake assist is necessary, a pump,is driven, and a solenoid valve,is switched to its communication position, and a solenoid shut-off valve,is opened. Then, the pump,sucks brake fluid from a reservoir,through the solenoid valve,and sends out the brake fluid to the pressure intensifying chamber,through the solenoid shut-off valve,At this point, an output shaft,has already advanced and a radial hole,is positioned ahead of a seventh cup sealing member,so that the pressure intensifying chamber,and the reaction chamber,are shut off from the reservoir,so as to be in the sealed state. Therefore, pump discharge pressure is supplied to the pressure intensifying chamber,and the reaction chamber,so that the pressure in these chambers is intensified. Since the intensified pressure acts on the primary piston,the master cylinder pressure is intensified to a value greater than that of normal braking. As mentioned above, by intensifying the master cylinder pressure when necessary, large braking force can be obtained with a simple structure.

Growing community of inventors

Higashimatsuyama, Japan

Hiroyuki Oka