Tokico, Ltd.

Kabushiki Kaisha Hitachi Seisakusho

Toshio Takayama

Kunihiro Matsunaga

Masaru Sakuma

Hiromi Ando

Takuya Obata

Hirotaka Oikawa

Yukio Matsumoto

Mitsuhiro Endo

Takato Ogiwara

Shuzo Watanabe

Yutaka Kitano

Mitsuhiro Endou

Tetsuo Haraikawa

Tohma Yamaguchi

Youichi Kumemura

Tadaaki Nakamura

Mitsuhiro Nagasaka

Osamu Sumiya

Tetsuya Takahashi

Kazumoto Sano

A master cylinder apparatus for a BBW system is provided, which enables accurate detection of a piston stroke without substantial increase in the size of a master cylinder. A master cylinder apparatus includes a master cylinder adapted to be connected to wheel cylinders through fail-safe valves, a stroke simulator for ensuring a desired stroke of a brake pedal upon receiving a brake fluid introduced from a fluid pressure chamber in the master cylinder through a simulator passage, and an opening/closing device for opening and closing the simulator passage. A stroke sensor for detecting a stroke of a primary piston is formed by a rotation angle detector, a sensor arm having one end connected to a rotary shaft of the rotation angle detector and a sensor pin extending from the primary piston. Linear motion of the primary piston is converted to rotational motion through engagement between the sensor pin and the sensor arm and is transmitted to the rotation angle detector.

Master cylinder apparatus

A master cylinder apparatus for a BBW system is provided, which eliminates a risk of brake delay, even with the use of a plunger-type master cylinder, and which therefore is able to achieve a reduction in size of a master cylinder. The master cylinder apparatus comprises a tandem-type master cylinder connected to wheel cylinders through fail-safe valves and a stroke simulator for ensuring a desired stroke of a brake pedal upon receiving a brake fluid introduced from a fluid pressure chamber in the master cylinder. The master cylinder is arranged in the form of a plunger-type master cylinder in which cup seals are provided on an inner surface of a bore of the cylinder body. A spring force of a second return spring for a secondary piston is set to be larger than that of a first return spring for a primary piston. A retracted position of the secondary piston is limited by a stopper pin extending through an oblong hole formed in the secondary piston.

An elastic member is interposed between a reaction disk and a plunger. By moving the plunger to open a poppet seal such that atmospheric air is introduced into the variable pressure chambers, a pressure differential is created between the variable pressure chambers and constant pressure chambers (negative pressure). As a result, servo power is applied to an output rod, and a resulting reaction force is partly transmitted back to an input rod through the reaction disk. During a rapid braking operation, a piston is caused to retract by a pin, thus pushing the elastic member into an outer peripheral groove formed on the piston so that the elastic member is axially compressed. As a result, the movement amount of the plunger can be increased without receiving a reaction force, enabling the rapid development of servo power.

Pneumatic booster

A valve bodyis connected to a power piston, which divides a housing into a constant pressure chamber (negative pressure) and a variable pressure chamber. In the valve bodythere is provided a brake assisting mechanismbetween a reaction diskand a plungerA poppet sealis opened by movement of the plungerto thereby introduce atmospheric air into the variable pressure chamber and generate a thrust force in the power piston. During rapid braking, a plunger rodadvances relative to a sleeveand ballsshift outward and the plunger roddirectly abuts against a reaction rodresulting in contraction of the brake assisting mechanismTherefore, the amount of movement of the plungercan be increased without being affected by a reaction force from the reaction diskthus enabling rapid development of servo power.

There is provided a pneumatic booster having an ejector, which achieves space-saving and enables easy piping. An ejectoris provided within a constant-pressure chamberformed in an outer shell. A connecting pipecommunicated with an outlet of a diffuser and a connecting pipe communicated with an inlet of a nozzle extend outward of the shell, and a suction port is open to the inside of the constant-pressure chamberthrough a check valve. The connecting pipeis communicated with the constant-pressure chamberthrough a check valve, and is connected to a suction pipe of an engine (a source of a negative pressure). The connecting pipe on the inlet side of the nozzle is connected to an air cleaner (the atmosphere). A negative pressure is directly supplied from the connecting pipeto the constant-pressure chamberthrough the check valve. The ejectoris operated to supply a high degree of vacuum to the constant-pressure chamberthrough the suction port. The ejectoris provided within the constant-pressure chamberso as to achieve space-saving. The check valveis provided in the ejectorand the connecting pipeis extended outward of the shell, so as to enable easy piping.

The present invention provides a brake booster that, although simple in construction, capable of adjusting the braking force derived by operation of a solenoid mechanism without worsening the braking response. In the brake booster according to the present invention, when a movable member ( ) is shifted toward the rear side by electromagnetic force of a solenoid ( ), the shifting movement is transmitted to a valve seat member ( ) through pins ( ) to open an atmospheric valve ( ) through which air is introduced into a variable pressure chamber ( ), whereby a pressure difference is created between the variable pressure chamber and a constant pressure chamber and generates booster output (thrust output force). In the present invention, pressure in the constant pressure chamber is introduced into a chamber ( ) formed at one end of the movable member ( ) through a passage ( ), and atmosphere is introduced into a chamber ( ) formed at the other end of the movable member ( ) through a passage ( ), thereby exerting on the movable member ( ) a reaction force caused by the pressure difference between the variable pressure chamber and the constant pressure chamber. Thus, the booster output becomes proportional to the electric current supplied to the solenoid ( ). Further in the present invention, the size of the passage ( ) is determined properly so as to limit air introduced therethrough into the chamber ( ) and keep the reaction force small until the booster output reaches an adequately level, thereby preventing the breaking response from deteriorating.

Brake booster

A solenoid-controlled valve has first and second valve bodies axially movably provided in a bore of a cylinder. A first spring is interposed between an end of th valve and the first valve body, a second spring is interposed between the two valve bodies, and an electromagnetic force generating device has a movable member which causes the two valve bodies to move in association with each other. Valve opening and closing modes of the two valve bodies are changed in a plurality of stages according to the displacement of the movable member. A restricting portion restricts relative displacement of the two valve. bodies away from each other so that the influence of the urging force of the second spring on the driving force of the electromagnetic force generating device becomes zero in the valve opening and closing mode in the final stage.

Solenoid-controlled valve

The present invention provides a control booster which is capable of appropriately detecting a pedal-operated brake operation during an automatic brake operation. For moving a stop key from a position on a side of a rear-side abutment surface (where a reaction force of a switch acting on a switch operating rod and a spring force of a switch spring are balanced) toward an intermediate position, when the stop key is located on a side of the rear-side abutment surface, only a return force of the spring acts on a contact operating element of the switch. On the other hand, when the stop key moves toward the intermediate position, an abutment portion is separated from the contact operating element (that is, the switch operating rod moves in a direction for separation relative to the switch), so that no load is applied to the contact operating element. Breakage of the switch can be avoided when the brake pedal is operated during the automatic brake operation and operation of the brake pedal can be detected from the turning-off of the switch.

Control booster

In a cylinder body of a cylinder apparatus of the present invention for a brake fluid pressure control system, primary and secondary pistons having different pressure-receiving areas are provided. A pressure chamber between the primary and secondary pistons is communicated with a reservoir through flow passages formed between the cylinder body and a sleeve and between the sleeve and the secondary piston. In normal operation of the brake fluid pressure control system, the cylinder apparatus serves as a stroke simulator by releasing the fluid in the pressure chamber through the flow passages to the reservoir and contracting a spring in the pressure chamber. In the event of a failure of the system, the cylinder apparatus serves as a tandem master cylinder in which the flow passages are closed by a seal member in accordance with movement of the secondary piston, and the primary and secondary pistons move, while substantially no contraction of the spring in the pressure chamber occurs.

Cylinder apparatus for a brake fluid pressure control system

The present invention provides a booster in which magnitude of output can be adjusted also by an operation of a solenoid mechanism. An armature (,) is shifted to the right (in FIG.,) in opposition to a returning spring by applying electricity to a solenoid (,), with the result that a space (,) on one end of the armature is communicated with a constant pressure chamber (,) through a passage (T,). When an electromagnetic force acting on the armature (,) exceeds a predetermined value, a distal end of a valve member (,) is shifted to the right (in FIG.,) via a cylindrical member (,) to open an atmospheric valve (,), thereby introducing the atmosphere into a variable pressure chamber (,). The pressure in the variable pressure chamber is applied to the other end of the armature and the difference in the pressure tends to move the armature toward its home position.

Booster

A master cylinder realizes a stroke simulator function without the need to change the structure around a brake pedal and without impairing brake pedal feel, is easy to form by machining, and also facilitates a hydraulic fluid charging and air bleeding operation. A secondary piston is split to make the axial length thereof variable, thereby imparting the stroke simulator function to the secondary piston. By doing so, brake pedal feel is improved more than by separately adding a stroke simulator.

Master cylinder

A vehicle brake control system includes a brake booster divided into a constant pressure chamber permanently communicating with a vacuum source, and a variable pressure chamber selectively communicating with the constant pressure chamber. The brake booster includes a first servo mechanism designed to develop a differential pressure between the two chambers, and a second servo mechanism. A master cylinder is operatively connected to the brake booster to create hydraulic pressure in response to the output of the brake booster, and hydraulic lines connect the master cylinder and the wheel cylinders. Pressure charging valves allow and block communication between the master and the wheel cylinders. Pressure relief valves between the pressure charging valves and the wheel cylinders selectively release the hydraulic pressure from the hydraulic lines. A controller controls the second servo mechanism, the pressure charging valves and the pressure relief valves, and is operable to cause the second servo mechanism to develop a differential pressure between the two chambers.

Vehicle brake control system

A motor-driven brake apparatus has a motor and a ball screw that converts rotational motion of the motor into rectilinear motion of a screw member. A position detector detects a stroke position of the screw member. A controller controls the motor on the basis of the result of detection by the position detector. The controller controls the motor so as to change the clearance between an inner pad (outer pad) and a disk according to vehicle running conditions.

Motor-driven brake apparatus

When a stroke speed exceeds a reference value of a stroke speed threshold value, a solenoid is energized to tract an armature, thereby opening an atmospheric valve independently of the position of a plunger. Consequently, power pistons, together with an output rod, are moved forward by a thrust corresponding to a pressure difference between a constant-pressure chamber and a variable-pressure chamber to perform a full-power braking operation. A reaction-adjusting mechanism contributes to an improvement in safety by functioning in such a way that when the part of the reaction force from the output shaft that is transmitted to an input rod reaches a predetermined value, a boosting ratio is increased, so that the reference value of the stroke speed threshold value can be set high to prevent unnecessary braking.

Braking system

A device for detecting a fault in a solenoid valve prevents a feeding system from supplying a drive current to a solenoid valve coil which actuates the solenoid valve from being damaged at the time of detection of the fault. The feeding system is provided with a first switch installed between one end of the solenoid valve coil and a battery, a second switch installed between the other end of the solenoid valve coil and a ground, and a plurality of wires for connecting the battery, the first and second switches and the solenoid valve coil. A test power supply system is connected to one end or the other end of the solenoid valve coil and supplies a micro test current to the solenoid valve coil when a current from the battery to the solenoid valve coil is cut off. A controller controls an operation of the first and second switches, and detects a fault in the feeding system on the basis of a voltage at the end of the solenoid valve coil opposite the end which the test power supply system is connected in accordance with the operating state.

Growing community of inventors

Yamanashi-ken, Japan

Toshio Takayama