Tokico, Ltd.

Kunihiro Matsunaga

Toshio Takayama

Hiromi Ando

Takuya Obata

Masaru Sakuma

Kenji Sano

Satoru Suga

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

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 brake control system includes a master cylinder for developing a brake fluid pressure in response to brake pedal displacement, wheel cylinders mounted to front and rear wheels and adapted to develop a braking force, an actuator for feeding the brake fluid pressure to the respective wheel cylinders, and a controller adapted to enable the actuator to provide a controlled brake fluid pressure to the respective wheel cylinders. Two switch valves are adapted to normally prevent fluid communication between the master cylinder and the wheel cylinders and in the event of a system failure, permit fluid communication between the master cylinder and the wheel cylinders and prevent fluid communication between the actuator and the wheel cylinders. The switch valves are mounted solely to the wheel cylinders of the front wheels.

Brake control system

A fluid passage switching valve includes a core structure provided with an input passage extending from an input port. The input passage opens on an outer peripheral surface of the core structure at such a position that when a plunger is in a fluid cut-off position, the input passage is closed by an inner surface of the plunger, and as the plunger moves toward a fluid passing position, the input passage is opened and communicated with an input port-side fluid chamber. An output port is communicated with an output port-side fluid chamber. The plunger has a communicating bore which provides communication between the input and output port-side fluid chambers. The pressure-receiving area of the plunger in relation to the input port-side fluid chamber is approximately the same as that of the plunger in relation to the output port-side fluid chamber over the entire travel range of the plunger. A seal device blocks communication between the input passage and the input port-side fluid chamber when the plunger is in the fluid cut-off position.

Hydraulic fluid passage switching valve

A brake fluid pressure adjustment device is presented for controlling the wheel lock of a vehicle by controlling the flow of the brake fluid from the main fluid path to the bypass path by means of a pumping mechanism which is in constant operation. The pumping mechanism includes a suction valve which only allows a unidirectional flow of brake fluid from the pump, and a reservoir to the pump; an electromagnetic device which forces open the bypass path between the pump and the reservoir by attracting the bypass path control valve element in one direction; and a discharge valve which allows only the flow of brake fluid from the pump to the main fluid path. Therefore, by controlling the actions of the electromagnetic means, it is possible to control the decrease, holding and increase actions of the pressure adjustment device, without stopping and starting the pump. The device thereby provides a delicate and timely response to the brake pressure variation needs without being affected by the inertial effects of the pump.

Fluid pressure control device for antiskid brake system

A load-responsive hydraulic control apparatus includes a valve operating member for opening a valve portion capable of permitting and preventing a master cylinder from communicating with the rear wheel cylinders of a rear wheel brake system. A plunger is provided for receiving hydraulic pressure from a branch path branched from the rear wheel brake system between the valve portion and the master cylinder and for opening the valve portion via the valve operating member when the received hydraulic pressure reaches predetermined hydraulic shifting pressure. An inertia valve blocks the branch path when predetermined deceleration is achieved.

Hydraulic control apparatus of load-response type

The present invention relates to a brake fluid pressure control apparatus provided with a flow valve which, during the normal operation, when a spool is in the stationary position, a master cylinder communication port is communicated with a wheel cylinder communication port while the pump communication port is closed, and during an antiskid control operation, a pump communication port and a wheel cylinder communication port are communicated, as well as a switching device to switch between the first and the second conditions. In the first condition, a master cylinder communication port is communicated with the output fluid passage of the master cylinder while the communication between the pump communication port and the master cylinder communication port is shut off. In the second condition, the communication between the master cylinder communication port and the output fluid passage of the master cylinder is shut off while the pump communication port and the master cylinder communication port are communicated. Therefore, when two functions, antiskid and traction controls, are to be provided to a brake fluid pressure control apparatus having an antiskid control capability, there is no need to change the flow valve itself, in particular the spool, to provide the two functions.

Brake fluid pressure control apparatus for antiskid control and traction

The present invention presents an economical fluid pressure control device particularly applicable to controlling the fluid pressure in the wheels of an automobile provided with an antiskid capability so that the unpleasant pedal kickbacks are prevented under various operating conditions of the wheels. This is achieved by providing at least two wheel cylinders for one pressure generation source, a reservoir and a pump. A flow valve provided on each of the wheel cylinders is provided with a simple flow switching device which control the position of a spool, disposed inside the flow valve, which assumes a stationary position for non-antiskid operation mode and a operation position for antiskid operation mode. When one of the wheels is in the antiskid operation mode, and the other wheel is in non-antiskid operation mode, the brake fluid discharged from the pump is not allowed to enter the flow valve disposed in the non-antiskid operation mode. Therefore, the fluid pressure pulsations generated in the fluid circuit in the antiskid operation mode are not transmitted back to the pressure generation source through the flow valve in the non-antiskid operation mode. Therefore, there in no transmission of unpleasant pedal kickbacks at the pressure generation source.

Fluid pressure control apparatus for antiskid brakes

The present invention relates to a brake fluid pressure control apparatus in which a casing contains a pump communication port separately from a master cylinder communication port. A spool is also provided which limits the communication between the pump communication port and the master cylinder communication port in a manner such that the discharge pressure from the pump is not added directly to the master cylinder. Additionally, in the intake and discharge sides of the pump, a bypass channel is provided. In this bypass channel, a relief valve is provided which allows the escape of pressure force to the intake side of the pump in the case when the pressure force between the discharge side of the pump and the flow control valve increases to a high pressure. Furthermore, because the brake fluid is normally designed to be discharged from the pump to the flow control valve at approximately a fixed flow rate by means of the relief valve, there is no return of brake fluid to the master cylinder via the flow control valve, and stroke fluctuations of the master cylinder can be eliminated. Additionally, the necessity for providing an orifice between a pump communication port and the master cylinder communication port disappears.

Brake fluid pressure control apparatus

The present invention relates to a brake fluid pressure control apparatus in which a casing contains a pump communication port separately from a master cylinder communication port. A spool is also provided which limits the communication between the pump communication port and the master cylinder communication port in a manner such that the discharge pressure from the pump is not added directly to the master cylinder. Additionally, in the intake and discharge sides of the pump, a bypass channel is provided. In this bypass channel, a relief valve is provided which allows the escape of pressure force to the intake side of the pump in the case when the pressure force between the discharge side of the pump and the flow control increases to a high pressure. Furthermore, because the brake fluid is normally designed to be discharged from the pump to the flow control valve at approximately a fixed flow rate by means of the relief valve, there is no return of brake fluid to the master cylinder via the flow control valve, and stroke fluctuations of the master cylinder can be eliminated. Additionally, the necessity for providing an orifice between a pump communication port and the master cylinder communication port disappears.

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Yamanashi-ken, Japan

Kunihiro Matsunaga