Abstract: An improvement of a variable pressure passage formed in the valve body of a brake booster is disclosed. A variable pressure passage including a first radial passage in which a key member is inserted and a second radial passage continuing from and located rearward of the first radial passage is the basis of the invention. According to the invention, a third radial passage, which also forms the variable pressure passage, is located forwardly of and continues from the first radial passage, and has a circumferential width less than that of the key member. This allows a corresponding increase in the channel area of the variable pressure passage, thereby improving the operational response of the brake booster without the need to increase the axial size of the valve body since the third passage is formed forwardly of the key member.

Abstract: Apparatus for preventing percussion beats in a brake booster is disclosed. The apparatus prevents percussion beats from occurring as a result of an abutment of a valve plunger, which forms part of a valve mechanism, against a key member which is used to prevent the valve plunger from being withdrawn from the valve body. An elastic member is formed on at least one of the key member and the valve plunger. The key member and the valve plunger are formed with abutting surfaces thereon which are adapted to abut against each other. A normal spacing between the abutting surfaces is chosen to be greater than a spacing as measured between the elastic member and the other member which is abutted by the elastic member. In this manner, the occurrence of percussion beats as the key member abuts against the valve plunger is prevented while also preventing a reduction in the durability of the elastic member.

Abstract: A sheath heater includes a metal sheath, a coil-like heater, and a heat-resistant insulating powder. The starting form of the metal sheath has a small-diameter cylindrical portion at its distal end and is formed to have a substantially tubular shape as a whole. The heater is fabricated by inserting the coil-like heater in the sheath. The heat-resistant insulating powder is charged in the sheath and holds the coil-like heater in the sheath so that the coil-like heater is electrically insulated from the sheath. The distal end portion of the sheath is melted and so that the confronting end of the coil-like heater is buried so as not to be exposed on the outer wall of a closing portion at the distal end of the sheath. The melting of the sheath end can be done by using plasma, electron-beam or laser welding techniques.

Abstract: An improvement of a variable pressure passage which is formed in a valve body of a booster, for example, a brake booster, is disclosed. The valve body which is disposed within a shell of the booster comprises a first and a second tubular member which are connected together. An axial space is defined by the outer peripheral surface of the first tubular member and the inner peripheral surface of the second tubular member when they are integrally connected together, and forms a variable pressure passage providing a communication between forwardly and rearwardly located, variable pressure chambers. This avoids the formation of an axial bore and a radial opening which are formed in a solid portion of a single member valve body, as occurs in the prior art, thus allowing the mechanical strength of the valve body to be improved.

Abstract: The temperature-dependent pressure detection switch according to the present invention comprises a pressure receiving member to receive hydraulic pressure, on which spring force of the predetermined value is permanently applied to the direction reverse to the operating direction of said hydraulic pressure and the spring force is varied according to temperature change, and a switch unit, which is operated by the movement of said pressure receiving member against said spring force when predetermined hydraulic pressure is received. Accordingly, when ambient temperature changes, spring force is changed, and the switchover setting pressure related to the on-off switchover operation of the switch unit can be changed according to temperature change. Namely, the pressure detection switch can be provided with temperature-dependent property.

Abstract: A fluid control valve device includes a sleeve, a rotor, and a first recess groove. The sleeve has an inner circumferential surface in which two types of axial channel grooves communicating with an input port and a return port are formed in the circumferential direction, and left and right output ports are open in land portions between the channel grooves. The rotor is inserted in the inner circumferential surface of the sleeve so as to be rotatably held relative to the sleeve and has an outer circumferential surface in which channel grooves communicating with the axial channel grooves of the sleeve are formed in the circumferential direction at positions opposite to the land portions in which the output ports of the sleeve are open, and first and second land portions are formed at positions opposite to the channel grooves of the sleeve.

Abstract: In the negative pressure booster equipment according to the present invention, a valve plunger 17 and an input shaft 18 are incorporated in a single member. Also, the axial length of the guide 17a of the valve plunger in relation to the valve body 4 is set to such size as to allow the angle of the maximum inclination of the input shaft 18 during operation. Further, a retainer 27 to support a spring 33 of a control valve 22 is removably mounted on the input shaft 18 from the atmospheric air inlet of the valve body 4. Accordingly, in the case of valve disc 24 is to be replaced, valve disc 24 and other rubber products can be readily replaced by removing the retainer 27 without disassembling the valve plunger 17 or the input shaft 18 from the valve body 4. Because the valve plunger 17 and the input shaft 18 are incorporated, the caulking process for the members 17 and 18 are not required.

Abstract: A seal unit for a brake booster such as of a tendem type including a centerplate disposed within a shell is disclosed. Annular seal means maintains a hermetic seal between the centerplate and a valve body. According to the invention, the annular seal means is formed with a passage which provides a communication between the inner and the outer periphery thereof. This allows a communication between the inner and the outer periphery of the annular seal means to be maintained by the passage formed therein in the event the opening of a constant pressure passage (or variable pressure passage) formed in the valve body is closed by the annular seal means. This allows a spacing between the annular seal means and a power piston or pistons mounted on the valve body to be reduced, contributing to reducing the overall length of the brake booster.

Abstract: A brake booster includes a center plate disposed within a shell. A seal member is provided to interrupt a communication between a variable and a constant pressure chamber which are located across the center plate. The seal member is formed with a lip, acting as a check valve which releases to the variale pressure chamber any pressure developed in the constant pressure chamber which is to be sealed by the seal member and which rises above the pressure in the variable pressure chamber.

Abstract: A brake booster is disclosed. Specifically, an apparatus for preventing withdrawal of a key member, which is used to prevent the withdrawal of a valve plunger, forming a valve mechanism, from a valve body includes a retainer which prevents the withdrawal of the key member from the valve body. An insertion groove is formed in the valve body, and radially extending slits are formed in the end faces defined by the sides of the insertion groove. The retainer is formed with a locking portion, the free end of which is formed with an engaging portion, which is inserted into the slit to prevent an axial displacement of the free end of the locking portion. In this manner, the withdrawal of the key member from the valve is positively prevented.

Abstract: 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.

Abstract: A liquid pressure booster which may be used in a brake booster or the like is disclosed. A second supply passage is provided which allows a power chamber of the liquid pressure booster to communicate with an external source of pressure fluid without passing through a valve mechanism of the liquid pressure booster. A first open/close valve is operative to open or close the second supply passage, and a second open/close valve is effective to open or close a discharge passage of the liquid pressure booster. A controller controls the first and the second open/close valve. With this construction, the controller may be caused to open the first valve and to close the second valve to allow the pressure fluid to be introduced into the power chamber through the second supply passage without depressing a brake pedal to cause a forward movement of an input shaft. In this manner, the liquid pressure booster can be operated automatically, and thus such booster can be advantageously used in an automatic braking unit.

Abstract: In a master cylinder for use in various braking devices of an automatic vehicle and the like, a cylinder housing is constituted by a body having an opening at one end thereof and by a cap which is coupled with the body to close the opening. A piston is inserted through the cap and is freely slidably arranged inside the cylinder housing and is guided by a piston guide or a sleeve having a path which is in communication with an external fluid path. The master cylinder has a single groove or a plurality of grooves with a micro-sized depth defined in the surface of the piston guide where it engages the cylinder housing between the external fluid path and a pressure chamber defined by the master cylinder and piston. The master cylinder also has a tapered portion provided on the inner surface of the cylinder housing, and another tapered portion is provided on the end of the sleeve.

Abstract: A rotary valve for power steering apparatus includes an input shaft, an output shaft disposed in axial alignment with the input shaft and connected thereto by a torsion bar, a valve rotor formed on the input shaft, and a valve sleeve connected to the output shaft and fitted over the valve rotor. A return oil path in the input shaft is formed inside a step defined in the internal surface of the valve sleeve while a return oil path in the valve sleeve is formed in a cylindrical portion of an increased internal diameter and extends therefrom along the step to define a return flow groove.

Abstract: A valve sleeve is fitted around valve rotor to define a rotary valve. The valve sleeve is characterized by the configuration of axially extending grooves which are formed in its internal surface. Specifically, the axial groove has a bottom surface which includes a lengthwise portion having a constant depth. The bottom surface of the groove is connected to the wall surfaces which are located at the opposite lengthwise ends as well as with the opposite lateral side walls by arcuate surfaces. At least one of the wall surfaces which are located at the lengthwise ends has an angle of inclination which exceeds 60.degree..

Abstract: The hydraulic brake pressure control valve is provided including a valve casing mounted on a master cylinder of a hydraulic brake system. A valve piston is provided with a stepped configuration with an enlarged diameter portion and a reduced diameter portion. The valve piston is mounted slidably and longitudinally along the longitudinal bore of the valve casing. The valve piston is normally urged into a non-operating position and is shiftable longitudinally in an opposite direction from the non-operating position under the effect of a difference in the cross-sectional areas of the enlarged and reduced diameter portions, upon which hydraulic brake fluid pressure acts. The stepped valve piston is defined with a brake fluid passage extending longitudinally therein providing communication between brake fluid passages adjacent the reduced diameter portion and the enlarged diameter portion of the stepped valve piston.

Abstract: An improvement relating to a front shell of a brake booster and a reinforcing plate which is connected to and extends along the inner surface of the front shell is disclosed. A radially inward portion of the front shell is formed with a cylindrical section which extends rearwardly, and an end face which provides a mounting surface for a master cylinder is defined adjacent to the rear end of the cylindrical section. The reinforcing plate is formed with a cylindrical portion which is fitted around the cylindrical section of the front shell, and an end face which is disposed in overlapping relationship with the end face of the front shell. This allows the rigidity of the front shell to be increased without requiring the welding of the reinforcing plate to the front shell.

Abstract: In a master cylinder, a sleeve for guiding the piston and a cap for forming a cylinder housing are connected with each other and integrally formed, and a primary piston and a secondary piston are coupled with via a retainer and thus integrally formed. Consequently, when the master cylinder is disassembled, the sleeve and the piston can be pulled out simultaneously, thereby allowing the simultaneous withdrawal of the secondary and primary pistons.

Abstract: In a method of controlling a power steering system, which controls a steering force in accordance with an engine revolution when no vehicle velocity signal is supplied, after the engine revolution becomes a first predetermined value or more, and subsequently becomes a second predetermined value or less and a third predetermined value or more, the steering force is controlled in accordance with the engine revolution.

Abstract: A seal unit is provided for a brake booster such as of a tandem type which includes a center plate within its shell. The brake booster includes annular means disposed within the shell for maintaining a hermetic seal between the center plate and a valve body. An axial portion of the center plate is formed with an axially extending cylindrical portion, the end of which is folded radially inward to define a U-shaped fold. The annular seal means is fitted inside the cylindrical portion, with its part disposed between the inner peripheral surface of the cylindrical portion and the outer peripheral surface of the fold. This effectively prevents the annular seal means from being withdrawn from the center plate.