Abstract: A valve mechanism comprises a first valve seat formed on a valve body and facing rearward, a second valve seat formed on a sleeve which is urged rearward of a spring and facing rearward, and a valve element urged by a popped return spring to be seated upon either valve seat. An effective diameter D1 of a rolling part of the valve element, an effective diameter D2 of a seal member and an effective diameter D3 of the second valve seat are chosen to be equal to each other. This arrangement allows a differential pressure which urges the sleeve and the valve element forward in the inoperative condition of the brake booster to be cancelled out, thereby allowing a load to which an urging spring must be charged to be reduced and thus allowing the use of a solenoid which is reduced in size, weight and heating value and hence which is inexpensive.

Abstract: An object of the present invention is to reduce the work cost of a piston, and to decrease the resistance of flow in a communicating passage between a pressure chamber and a reservoir, and to reduce the ineffective stroke, too, and the means is as flows: a small outside diameter portion (28) whose outside diameter is reduced by forming a step surface (27) on the periphery of a piston (24) and a sleeve (30) to be fitted onto the periphery of the small outside diameter portion (28) are provided; and a radial passage groove (32) formed along the radial direction between the step surface (27) and the end surface of the sleeve (30) opposite to the step surface (27) and an axial passage groove (33) formed along a direction crossing the radial passage groove (32) between the inner surface of the sleeve (30) and the peripheral surface of the small outside diameter portion (28) are provided; and the radial passage groove (32) and the axial passage groove (33) are used as a communicating hole.

Abstract: In a brake system, a controller closes solenoid shut-off valves to shut off a communication between a master cylinder and wheel cylinders by pressing a brake pedal, and at the same time, drives a pump and controls the operation of brake fluid pressure control means to supply brake fluid through the pump to the wheel cylinders, thereby performing braking action. Idle travels of the wheel cylinders can be cancelled by the brake fluid from the pump, and a very short pedal stroke can be obtained. Since the brake characteristics are set by considering three factors, i.e. pedal characteristics, travel of a brake pedal, and deceleration (brake fluid pressure) of a vehicle, the brake system has a very short stroke of the brake pedal as compared to a conventional one and has optimal brake characteristics.

Abstract: According to the invention, a servo ratio regulating member is disposed on the front end face of the valve body for abutment against the rear end face of a reaction disc. The servo ratio regulating member comprises an engaging portion which is engaged with a portion of a reduced diameter formed on the front end face of the valve body, and an abutment portion continuing from the engaging portion and projecting forwardly for abutment against the reaction disc. An external diameter D″ of the abutment portion as well as an external diameter of the reaction disc which is seated thereon are greater than an external diameter D of the outer periphery of the valve element, reducing the proportion of a brake reaction which is transmitted to a driver. With this arrangement, a higher servo ratio can be established with an arrangement which is simplified and inexpensive as compared with the prior art.

Abstract: A brake system 1 of the invention comprises a brake pedal 2, a booster 3 which boosts the input force applied by the brake pedal 2 and outputs the boosted force, a travel amplifying mechanism 4 which amplifies the travel of an output shaft of the booster 3 and outputs the amplified travel, a master cylinder 5 which develops master cylinder pressure when the output from the travel amplifying mechanism 4 is applied to the master cylinders 5, and wheel cyclinders 6 which develop braking forces when the master cyclinder pressure is introduced into the wheel cyclinders. By the travel amplifying mechanism 4, the travel of the brake pedal 3 in the initial stage of operation is amplified by the travel amplifying mechanism and is then transmitted to the master cylinder 5, whereby the idle stroke of the operating member caused by various idle portions in stroke in the brake system can be effectively shortened.

Abstract: In a power steering device, a pump supplies a pressure fluid. A power cylinder has left and right chambers and is driven in accordance with a pressure difference between a pressure fluid supplied to the left chamber and that to the right chamber. A flow channel selector valve selectively switches a supply direction of the pressure fluid from the pump to the chambers of the power cylinder in response to steering operation of a steering wheel. Fluid paths connect the flow channel selector valve and the corresponding chambers of the power cylinder to each other. Variable restrictors are disposed in the fluid paths, respectively, to control flow rate of the pressure fluid from the power cylinder to the flow channel selector valve. Check valves are respectively connected to the fluid paths in parallel to the corresponding variable restrictors to prevent a flow of the pressure fluid from the power cylinder to the flow channel selector valve.

Abstract: A brake booster 1 of tandem type includes a solenoid 16 within a valve body 6. The solenoid 16 is provided with a forwardly disposed holder 42 and a rearwardly disposed yoke 43, with a spool 44 held sandwiched therebetween and with a piston 56 disposed to be moveable around the inner periphery. A tubular guide 56A is formed on the front portion of the piston 56 while an annular guide 56B is formed on the rear portion of the piston 56. The tubular guide 56A is slidably fitted into the inner periphery of the holder 42 while the annular guide 56B is slidably fitted into the inner periphery of the yoke 43. When the solenoid 16 is energized to cause the piston 56 to move back and forth relative to the holder 42 and the yoke 43, this movement is guided by the both guides 56A, 56B. This arrangement permits a smooth back-and-forth movement of the piston 56 as compared with the prior art.

Abstract: A rack-pinion type power steering apparatus includes a cylindrical stub shaft, a torsion bar, a pinion shaft, a rotor, and a sleeve. The stub shaft rotates in a steering body upon a steering operation. The torsion bar has one end fixed at one end of the stub shaft and extends toward the other end of the stub shaft. The pinion shaft is pivotally connected to the other end of the torsion bar and has pinion teeth that mesh with a rack of a steering wheel. The rotor is arranged to cover the torsion bar from the stub shaft along an extending direction of the torsion bar. The sleeve has one end integrally connected to the pinion shaft, extends from the pinion shaft along the stub shaft, and is arranged around the rotor to constitute a rotary type channel selector valve between the rotor and the sleeve. At least two ends of an inner circumferential portion of the sleeve integrally connected to the pinion shaft have slidable contact surfaces that slidably support the rotor integrally connected to the stub shaft.

Abstract: A variable displacement pump includes pump bodies, a cam ring, first and second fluid pressure chambers, a rotor, a driving shaft, a pump chamber, a compression coil spring, a metering restrictor portion, and a control valve. A plunger damper is formed to incorporate the compression coil spring such that a distal end of the plunger damper abuts against a side portion of the cam ring in the second fluid pressure chamber. A small hole constituting the metering restrictor portion is formed at such a position that it is opened/closed by a slidable motion of the plunger damper during a swing motion of the cam ring, and such that it is partitioned from the second fluid pressure chamber, so that an opening area of the small hole changes in an interlocking manner to the swing motion of the cam ring.

Abstract: A ball bearing includes a rotary member, an outer ring, and a plurality of balls. Part of the rotary member serves as an inner ring. The outer ring is fitted on an outer circumferential portion of the inner ring. The plurality of balls are incorporated in ball holding grooves between the inner and outer rings. At least one of the inner and outer rings has a stepped portion in a circumferential surface thereof close to the ball holding grooves. The stepped portion prevents positional shift of the balls incorporated through a gap between the inner ring and the outer ring set eccentric with respect to the inner ring. A method of assembling a ball bearing is also disclosed.

Abstract: A fluid pressure boosting device of the present invention performs jumping action at a higher servo ratio until fluid pressure in a power chamber (25) reaches a first predetermined value and a rear end (20e) of a reaction piston (20)comes in contact with a step of an input shaft (18). Since a switching valve is set in a first position I until the fluid pressure in the power chamber (25) reaches a second predetermined pressure, a reaction chamber (41) is connected to the reservoir (33) 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 (25) 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 (41). The fluid pressure in the reaction chamber 41 acts on the step between the reaction piston (20) and the input shaft (18) so that the servo ratio becomes higher.

Abstract: In a brake boosting system the present invention, as it is decided that brake assist is necessary, a pump 53 is driven, and a solenoid valve 72 is switched to its communication position, and a solenoid shut-off valve 75 is opened. Then, the pump 53 sucks brake fluid from a reservoir 9 through the solenoid valve 72 and sends out the brake fluid to the pressure intensifying chamber 21 through the solenoid shut-off valve 75. At this point, an output shaft 11 has already advanced and a radial hole 38 is positioned ahead of a seventh cup sealing member 31 so that the pressure intensifying chamber 21 and the reaction chamber 33 are shut off from the reservoir 9 so as to be in the sealed state. Therefore, pump discharge pressure is supplied to the pressure intensifying chamber 21 and the reaction chamber 33 so that the pressure in these chambers is intensified. Since the intensified pressure acts on the primary piston 12, the master cylinder pressure is intensified to a value greater than that of normal braking.

Abstract: In this invention, an idea is adopted in which the pressure at a forward portion and a backward portion of valve device is steppingly dropped twice. The valve device of the present invention includes, on the axis of a spool 600, a first valve 710 located nearer an inlet port and a second valve 720 located nearer an outlet port. A throttling area made by the second valve 720 is larger than a throttling area made by the first valve 710. For example, of all the pressure difference equal to 120 kg/cm.sup.2 or more required at the forward and backward portions of the valve device, a portion in the range where the problem of an occurrence of a foreign noise is not encountered (for example, a portion ranging from 100 to 120 kg/cm.sup.2) is undertaken by the first valve 710, and the remaining portion ranging from 20 to 30 kg/cm.sup.2 is undertaken by the second valve 720.