Jidosha Kiki Co., Ltd.

Other

Nissan Motor Company Limited

Tohru Satoh

Masahiro Ikeda

Makoto Watanabe

Kazuo Kobayashi

Atushi Satoh

Hidefumi Inoue

Shintaro Uyama

Haruo Suzuki

Naohito Saito

Hiroya Gotoh

Masaru Konishi

Hiroya Goto

Shigeo Shingyoji

In accordance with the invention, a booster is not provided with a mechanism which transmits a braking reaction, and accordingly, a reaction cannot be transmitted to a brake pedal. On the other hand, a pseudo-reaction imparting means is provided to impart a pseudo-reaction which depends on an amount of depression of the brake pedal. The pseudo-reaction imparting means imparts a pseudo-reaction having a reduced rate of increase to the brake pedal when a travel of the brake pedal is small, and imparts a pseudo-reaction having an increased rate of increase to the brake pedal when a travel of the break pedal is higher. This arrangement avoids the drawback of the prior art that an abnormally high braking reaction is transmitted to a driver as a result of an operational lag of a conventional booster during a quick braking operation. The invention prevents such braking reaction from being transmitted to a driver, but enables a reaction of a required magnitude to be transmitted to the driver by means of pseudo-reaction imparting means. In this manner, a required high braking effort can be obtained with a reduced force of depression during a quick braking operation. The pseudo-reaction imparting means which exhibit such characteristic is capable of realizing an operation feeling, as experienced in a normal operation in the prior art, independently from a quick and a slow braking operation.

Reaction mechanism for booster

Reaction transmitting means of a brake booster includes a parallel combination of a first and a second reaction transmitting path each transmitting a brake reaction from a reaction disc to a valve plunger. The first reaction transmitting path includes a spring charged to a preset load, and the second reaction transmitting path includes a viscoelastic member as may be formed of rubber. With this construction, a hysteresis is obtained in both a low range of servo ratio during an initial phase of operation of a brake booster and a higher range of servo ratio during a later phase of operation, which occur before and after the spring in the reaction transmitting mechanism is compressed, thus allowing a good brake feeling to be maintained.

Brake booster

An improvement of a reaction transmitting mechanism for a booster is disclosed. A spring charged to a preset load is disposed between a stepped end face of value body and a plunger plate to urge the latter forwardly. This separates the plunger plate and a value plunger from each other in the inoperative condition of the booster. As an input shaft is driven forward to operate the booster, a reaction disc bulges into abutment against the plunger plate. Subsequently when the spring is compressed, the plunger plate abuts against the value plunger, which defines a jumping point. From this point on, a reaction from the output is transmitted to a driver. Since the output upon the jumping is determined by the preset load to which the spring is charged, a variation in the output upon jumping is minimized for any variation in the hardness of the reaction disc.

Brake booster having a reaction force mechanism

A brake booster includes a reaction transmitting means which includes a spring that is compressed when a brake reaction from a reaction disc exceeds a preset load. A holder is mounted on a valve body, and a brake reaction which is transmitted from the reaction disc is accepted by the valve body through the holder. A plate plunger is slidably fitted in the holder to allow a brake reaction which is transmitted to the reaction disc to be transmitted to the reaction transmitting means and the valve plunger through the plate plunger. A larger outer diameter can be chosen for the spring in order to achieve a preferred preset load, and a servo ratio can be freely established by the choice of areas of contact between the reaction disc on one hand and the holder and the plate plunger on the other hand.

According to the invention, a first spring abutment which extends radially outward is formed on a valve plunger, which forms part of a reaction mechanism for brake booster. A second spring abutment which extends radially outward is formed on a plate plunger. A plurality of coiled springs are disposed in parallel across the pair of spring abutments, and a brake reaction is transmitted to the valve plunger through the plate plunger, the second spring abutment, the plurality of the coiled springs and the first spring abutment. With this construction, the plurality of coiled springs which are disposed in parallel provide a combined spring constant, which is given as a sum of spring constants of individual coiled springs, whereby a combined spring constant of an increased magnitude can be obtained. This allows a servo ratio of the brake booster while the plurality of coiled springs are being compressed to be freely chosen as compared with the prior art.

Reaction mechanism for brake booster

A brake booster is disclosed which functions as an automatic brake as required. Bellows is disposed within a constant pressure chamber of the brake booster, and has a front end which is connected, by a first support member, to a bulge which is formed in the axial portion of a shell. A seal member is connected to the outer periphery of the first support member, and is held in abutment against the wall surface of the shell at a location radially outward of an inlet for the atmosphere. A communication channel is formed by a space between the first support member and an opposing wall surface of the shell and the bulge and the like. A communication is established between the internal space of the bellows and the inlet through the communication channel. This construction allows the overall length of the brake booster to be reduced as compared with the prior art in which a spacer is provided outside the shell.

An improvement of a retainer which constitutes a valve mechanism for booster is disclosed. The retainer is used to secure the rear end of a valve element against a tubular terminal end of a valve body by abutment. The retainer comprises a tubular holder supporting the inner peripheral surface of the rear end and urging its outer peripheral surface into tight contact with the inner peripheral surface of the tubular terminal end, a securing portion, disposed rearward of the tubular holder and extending radially outward to be secured to the inner peripheral surface of the tubular terminal end, an anti-withdrawal portion disposed forwardly of the tubular holder and projecting radially outward, and a tapered portion disposed forwardly of the anti-withdrawal portion and extending radially inward and axially so as to be narrowed into a conical configuration. The construction, in particular, the provision of the tapered portion, facilitates fitting the rear end around the outer periphery of the tubular holder.

Retainer in valve mechanism of booster

An improvement of a valve mechanism used in a brake booster is disclosed. A valve element comprises a first and a second annular member, both formed of a metal and which are connected together in an axial orientation, and an elastic deformation which is connected to the rear side of the second annular member. A rubber piece mounted on the first annular member defines a first seat area, and a rubber piece mounted on the second annular member defines a second seat area. With this construction, a spring which is used to urge either seat area of the valve element into seating engagement with the respective valve seat may be compressed to a lower load than in the prior art, thus allowing an input required to initiate the operation of the brake booster to be reduced.

Booster

A brake booster, specifically, an improvement of a valve mechanism for booster is disclosed. According to the invention, the rear side of a curved portion of a valve element is surrounded by a retainer to be interrupted from the atmosphere. This prevents the atmospheric pressure from acting upon the curved portion of the valve element owing to the presence of the retainer.

Valve mechanism for booster

An improvement of an axial portion of a power piston and a retainer engaging therewith for a booster. An axial portion of the power piston is formed with a first tubular portion, which is provided with a second tubular portion located outward of the first tubular portion. The first tubular portion is fitted over a flange of a valve body from the rear side, and an annular retainer engages the second tubular portion from the front side, thereby securing the axial portion of the power piston, which is formed with the both tubular portions, on the flange of the valve body. The retainer includes a plurality of engaging pawls, which engage the outer peripheral surface of the second tubular portion of the power piston by point contact. This reduces the axial size of the valve body, and hence the axial size of the booster.

Power piston assembly for booster

An improvement of a recess formed in one end of an output shaft of a brake booster is disclosed. At its one end, the rear extremity of the output shaft is formed with a flange-like stop, which is formed of an annular sheet material. The engagement of the stop with the retainer is effective to prevent said one end of the output shaft from being disengaged from an annular projection on a valve body. This allows the diameter of a reaction disc to be increased without requiring an increase in the diameter of the valve body. Accordingly, a brake feeling can be adjusted over an increased extent than before by increasing the diameter of the reaction disc.

Brake booster with reaction disk retainer

A power piston assembly for booster, in particular, an improvement of an axial portion of a power piston and a retainer which is engaged therewith is disclosed. A front power piston is formed with a first and a second tubular section around its inner periphery, and the first tubular section is fitted around a flange of a valve body and is prevented from disengagement therefrom by an annular retainer. Around its outer peripheral edge, the retainer is formed with a peripheral tubular portion, which is disposed as a press fit around the second tubular section of the front power piston from the front side, thereby connecting the front power piston to the flange of the valve body. With this arrangement, the front end of the first tubular section of the front power piston may be located rearward of the front end of the valve body (or its flange). Accordingly, the axial size of the first tubular section and hence of the booster may be reduced as compared with a conventional arrangement.

Power piston assembly for booster with diaphragm retainer

An enclosed shell is divided by a center plate and a pair of front and rear diaphragms which are disposed on the opposite sides of the center plate into four chambers. A center body is fitted over a valve body which internally houses a valve mechanism. The center body slides relative to the central portion of the center plate with a seal member interposed therebetween. The inner periphery of the front diaphragm is inserted inside the center body, and is held between the valve body and the center body at a location rearward of the seal member, whereby the overall length of the brake booster is reduced.

Brake booster of tandem type

A brake booster such as of a tandem type having a center plate disposed within a shell is disclosed. A valve body has a stepped end face, from which a cylindrical portion extends rearwardly. The cylindrical portion extends through a rear power piston and a rear diaphragm while maintaining a hermetic seal therebetween, with a distal end of the cylindrical portion being disposed within a variable pressure chamber of a rear chamber. The internal space of the cylindrical portion defines the rear end of a variable pressure passage. This arrangement allows the rear end of the variable pressure passage (the cylindrical portion) to be disposed in radially overlapping relationship with the rear power piston, thereby allowing the external diameter of the valve body to be reduced. In this manner, the effective area of the front power piston connected to the valve body may be increased as compared with the prior art.

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Saitama-Ken, Japan

Tohru Satoh