Tokico, Ltd.

Hitachi Automotive Systems, Ltd.

Kabushiki Kaisha Hitachi Seisakusho

Hitachi, Ltd.

Mitsuhiro Endo

Hiromi Ando

Shuzo Watanabe

Kiyoshi Shirahata

Yukou Ono

Toshio Takayama

Atsuya Koshu

Naganori Koshimizu

Takuya Usui

Takato Ogiwara

Atsushi Odaira

Hiroshi Shigeta

Hiroshi Owada

Kunihiro Matsunaga

Naoki Shirakawa

Satohiro Koi

Tetsuya Takahashi

Tadaaki Nakamura

An electric motor is controlled according to the back and forth movement of an input rod, which is caused by brake pedal operation; a primary piston is propelled to generate hydraulic brake pressure in a master cylinder; and the hydraulic brake pressure is fed back to the input rod through an input piston. The input piston is resiliently held by springs with respect to the primary piston. A jump-in clearance is created between the input piston and the input rod by a rearward spring. At the initial stage of braking, hydraulic brake pressure is not transmitted to the input rod due to the jump-in clearance, which provides jump-in characteristics. The jump-in clearance can be set, regardless of the amount of a relative displacement between the primary piston and the input piston, so that the range of adjustment for regenerative braking can be set larger than the jump-in clearance.

Electric booster

An input rod is operated by a brake pedal to introduce the air into a variable-pressure chamber through a control valve to propel a power piston, thereby advancing a primary piston to generate a brake fluid pressure in a master cylinder. A part of the reaction force from the fluid pressure is transmitted to the input rod through a reaction member. The primary piston is provided with an idle stroke in which no fluid pressure is generated, and the reaction force to be transmitted to a plunger is limited by a reaction force adjusting spring. In the region of the idle stroke, a fluid pressure is supplied to a wheel cylinder through a fluid pressure control unit to perform regenerative cooperative control, and a reaction force from a reaction spring is applied to the input rod.

Booster and brake apparatus using the same

A pneumatic booster () disposed between a brake pedal () and a master cylinder () includes a cylindrical member () provided on an outer circumferential side of an output rod (). A seal member () seals between an outer circumferential side of the cylindrical member and a cylindrical portion of a front shell, and an O-ring seals between the cylindrical member and the output rod. The cylindrical member causes a differential pressure between a negative pressure chamber (A) and an atmosphere chamber (C) to be applied to a valve body (). One axial side of the cylindrical member is configured to cause an atmosphere pressure to be applied to the valve body by abutting against a cylindrical protruding portion of the valve body, thereby pushing the valve body with the aid of the differential pressure in the direction as a biasing direction of a return spring.

Pneumatic booster and brake system

A controller controls a hydraulic control device to generate a target braking force corresponding to the stroke of a brake pedal by adjusting a controlled hydraulic braking force portion generated by the hydraulic control device on the basis of the relationship with a master hydraulic braking force portion generated from the brake hydraulic pressure in a master cylinder and a regenerative braking force portion generated by a regenerative brake device. The regenerative brake device maximizes the regenerative braking force portion before the stroke of the brake pedal reaches an idle stroke, and thereafter, the hydraulic control devicestarts braking by the controlled hydraulic braking force portion. When the stroke of the brake pedal reaches the idle stroke, the master cylinder starts braking by the master hydraulic braking force portion.

Brake apparatus

In a pneumatic booster, a front shell and a rear shell are connected by means of a rod. A stud bolt on one end of the rod extends through the front shell to the outside, and a support plate fitted around the stud bolt is engaged with the rod and abutted against an inner surface of the front shell. A seal member is provided in an annular groove formed in the support plate. A projection is formed in the support plate. When the support plate is reversely mounted on the stud bolt, the projection is abutted against the front shell, and the seal member is unable to provide a seal between the stud bolt and the front shell. In a leak inspection, air is flowed into a constant-pressure chamber through a cut portion formed in a distal end of the projection, to thereby detect reverse mounting of the support plate.

Pneumatic booster

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.

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.

A pneumatic booster includes a valve mechanism for introducing atmospheric air into a variable-pressure chamber in accordance with the movement of a plunger, propelling a power piston due to differential pressure generated between the variable-pressure chamber and a constant-pressure chamber and transmitting force by which the power piston is propelled through a valve body to an output shaft. The valve mechanism includes a poppet valve mechanism including a seal surface capable of abutting against an annular atmospheric valve seat formed in the plunger and a seal surface capable of abutting against an annular negative pressure valve seat formed on an inner surface of the valve body. The annular atmospheric valve seat of the plunger is located in a position forward in a direction of propelling of the power piston relative to the negative pressure valve seat and is substantially aligned with the negative pressure valve seat in an axial direction. The poppet valve mechanism has a main poppet valve including the seal surface capable of abutting against the negative pressure valve seat and a sub poppet valve including the seal surface capable of abutting against the atmospheric valve seat. The seal surface of the sub poppet valve is spaced apart in the axial direction from the seal surface of the main poppet valve.

A pressure differential operated brake booster includes a housing, a diaphragm assembly adapted to divide the interior of the housing into a constant pressure chamber and a variable pressure chamber, a valve body carried by the diaphragm assembly, a valve mechanism arranged within the valve body and including a plunger connected to an input rod, and a reaction assembly disposed between the plunger and an output rod. The valve mechanism is operable to develop a pressure differential across the diaphragm assembly to transmit its movement to the output rod and feed part of the resulting reaction force back to the input rod through the reaction assembly and the plunger. The reaction assembly includes a front reaction disk and a separate rear reaction disk having a diameter less than that of the front reaction disk and greater than that of the plunger. The front reaction disk is disposed between the valve body and the output rod. The valve body has at its front end a recess to receive the rear reaction disk. The plunger has a front end extending slightly into the recess.

Pressure differential operated brake booster

A brake booster includes a housing, a partition adapted to divide the interior of the housing into two chambers, and two diaphragms adapted to divide the two chambers into constant and variable pressure chambers. A control valve includes a valve body carried by the diaphragms, and a plunger slidably received in the valve body. The control valve is operatively connected to the variable pressure chambers to develop a pressure differential across the diaphragms to cause the diaphragms to move in response to actuation of an input rod. A reaction disk is disposed between an output rod and the valve body to transmit the reaction of movement of the output rod to the input rod. An adjusting mechanism is disposed between the plunger and the reaction disk and compressible so as to develop a greater degree of pressure differential when a force applied by the input rod exceeds a predetermined level. The reaction disk is caused to make contact with the contact disk and held out of contact with the spring and the plunger when the plunger is actuated.

A booster apparatus of a vacuum type for a brake device has a housing including therein a chamber, a diaphragm for dividing the chamber of the housing into a constant pressure chamber and a variable pressure chamber, an input shaft including a distal end, an output shaft including a proximal end, a plunger which is engageable with the distal end of the input shaft for transmitting force from the input shaft to the output shaft, a reaction disk disposed between the plunger and the proximal end of the output shaft for transmitting reaction from the output shaft to the plunger, and a valve body mounted on the diaphragm. The valve body includes a hole for slidably receiving the plunger, a recess for fixedly receiving the reaction disk and the proximal end of the output shaft which recess is larger than the plunger hole in inner diameter, and an intermediate hole portion disposed between the plunger hole and the recess. The intermediate hole portion is smaller than the recess and is larger than the plunger hole in inner diameter.

Booster apparatus of vacuum type

A tandem pneumatic booster having a shell body, the inside of which is divided into two, front and rear, chambers by a center shell. Each chamber includes a negative pressure chamber and a working pressure chamber. A valve body is slidably fitted in the shell body and the center shell with seal members therebetween. The valve body is provided with an air passage for communication between the front and rear working pressure chambers. A valve mechanism is actuated in association with an input shaft to introduce atmospheric air into the front and rear working pressure chambers through the air passage so as to apply thrust to front and rear power pistons. The diaphragm of the front power piston has a bead on an inner periphery thereof. The valve body has a groove on an outer periphery thereof. A portion of the air passage which leads to the front working pressure chamber has a main passage portion extending axially in the valve body, and a bypass extending radially outward from the main passage portion. A communicating port leading to the front working pressure chamber extends axially from the bypass. The bypass opens into the groove, and the radially outer end of the bypass is sealed with the bead.

A plunger moved with an input shaft is movably fitted in an axial bore of a valve body made of resin, and a valve mechanism selectively establishes and cuts off communication in a negative pressure passage and an atmosphere passage formed in the valve body according to the movement of the plunger. Also, a pair of radial holes formed to have a circular cross section are provided in the valve body by drilling work, and a plate type stop key formed in a fork shape having two claw branches is mounted by loosely inserting the branches in the radial holes. The stop key limits a movement range of the plunger. Also, a guide portion is formed on an outer circumference of the valve body to guide side surfaces of the stop key. The movement of the stop key is restricted by the guide portion and a step formed in the axial bore of the valve body. Therefore, a smooth operation of the pneumatic booster can be guaranteed.

A pneumatic booster for use, for example, in a brake system of a vehicle, and designed so that the overall axial length is reduced without interfering with the operation thereof. The booster comprises a valve body which is movable back and forth between first and second positions in a housing that is divided by a diaphragm with a power piston into front and rear chambers communicated with respective pressure sources, a valve which allows at least one of the front and rear chambers to selectively communicate with the pressure sources which differ from each other in the level of pressure, and a guide which slidably fits on the outer periphery of the valve body. The valve body has a passage one end of which opens on the outer periphery thereof to connect one of the front and rear chambers to the associated pressure source, the opening of the passage being positioned in the axial direction of the valve body so that the guide overlaps the opening when the valve body is at either the first or second position. The guide has a guide member and a seal member. The guide member has a plurality of axial grooves provided in the inner periphery thereof at predetermined spacings in the circumferential direction so that the passage communicates with the one chamber through the grooves when the valve body is at either the first or second position where the guide overlaps the opening.

A pneumatic booster has a housing which includes a forward shell and a rearward shell, and a diaphragm which is installed inside the housing and secured at the outer peripheral portion thereof to the housing. The diaphragm has a bead formed on the outer peripheral portion thereof. The rearward shell has a bead retaining portion which has a bead retaining groove that opens radially outward. The forward shell has an outer peripheral portion. The bead is received into the bead retaining groove across one edge portion of the bead retaining groove and clamped between the groove and the outer peripheral portion of the forward shell. The dimensions of the bead and the bead retaining portion are set so that the inner diameter of the bead is greater than the outer diameter of the edge portion of the bead retaining groove. Thus, the rearward shell and the diaphragm can be assembled together without the need to bend the diaphragm in advance, and the assembly process is correspondingly facilitated.

Growing community of inventors

Yamanashi-ken, Japan

Mitsuhiro Endo