Jidosha Kiki Co., Ltd.

Nissan Motor Company Limited

Yoshio Tobisawa

Hitoshi Kubota

Jun Kubo

Yasuki Ishikawa

Masatoshi Nakamura

Yoshiyasu Takasaki

Norio Fujiki

Naosuke Masuda

Tadaaki Fujii

Morihiko Shimamura

Kazuyoshi Fukawa

A brake booster which permits a booster ratio to be changed in two stages. A first spring,is disposed between a first plunger plate,and the bottom of a stowage,A of a valve plunger,. Toward its front end, the outer periphery of the first plunger plate,slidably extends through a second plunger plate,, which is in turn located at its inoperative position shown by a second spring,having a greater spring constant than the first spring,. When the brake booster,is actuated, a reaction disc,which bulges rearward initially abuts against the first plunger,, and subsequently, as the first spring,is compressed, it abuts against the end faces of the both plunger plates,. If a brake pedal is released under this condition, a hysteresis is substantially nullified. The invention provides an improved brake controllability in a region of a greater depression (or input) of the brake pedal.

Brake booster

In case of reducing pressures according to an ABS of the present invention, solenoid valves 14, 15 are turned on and the pressure difference between chambers 24, 23 of a vacuum booster 4 becomes smaller, thereby reducing the brake pressures. Further, solenoid valves 7, 9 are turned on so that brake fluid in W/Cs 8 is discharged to sumps 10, thereby further reducing the brake pressures. At this point, the pressure difference between chambers 55, 56 of a vacuum driven pump 51 also becomes smaller so as to move pistons 54, 61, 62 backward and the brake fluid of the sumps 10 is thus sucked into fluid chambers 63, 64. In case of increasing pressures by the ABS control, the solenoid valves 14, 15, 7, 9 are turned off and the pressure difference between the chambers 24, 23 becomes larger, thereby increasing the brake pressures. At this point, the pressure difference between the chambers 55, 56 becomes larger so as to move the pistons 54, 61, 62 forward and the brake fluid in the fluid chambers 63, 64 is sent to a MCY. Therefore, a pump driven by a motor is no longer required, thereby allowing the ABS to be manufactured lighter and at a lower cost and, in addition, allowing both smaller noise and smaller kick back.

Anti-skid brake control system with vacuum driven pump

In a brake booster system of the present invention, just after a MCY produces MCY pressure Pi according to the pedal pressure of a brake pedal, a valve piston of a pressure-intensifying valve moves so that a valve portion is seated in a rubber valve seat. In addition, a pedal switch detects the pedaling of the brake pedal to drive a motor and a pressure-intensifying pump. Therefore, W/C pressure Po of a W/C is intensified by the discharge pressure of the pressure-intensifying pump. The intensified W/C pressure Po causes the upward movement of a stepped piston of a pedal stroke shortening cylinder. The brake fluid is transferred toward the MCY corresponding to the movement of the stepped piston, thereby restricting the stroke of the piston of the MCY and thus shortening the pedal stroke of the brake pedal.

Brake booster system

A relay valve is operatively disposed between a pressurized air source and a work chamber of a brake booster. The relay valve has a pilot chamber so that the relay valve can feed the work chamber with a pressurized air, the pressure of which corresponding to that of a pressure applied to the pilot chamber. Electromagnetic valves are arranged to selectively connect the pilot chamber with the pressurized air source and the atmosphere. The valves are so controlled by an electronic control unit that the pilot chamber is supplied with pressurized air the pressure of which being determined in accordance with a brake pedal force applied from a brake pedal to an input means of the booster.

Pneumatic power brake system

A brake booster of positive pressure type includes a valve mechanism to which a positive pressure such as compressed air from a source located externally of a shell is fed for switching a flow path, through a conduit disposed within a constant pressure chamber disposed forwardly of a power piston and a supply passage which is formed in a valve body. The supply passage according to the invention comprised a radial passage which extends radially outward through the valve body from a shank portion thereof, and an axial passage which communicates with the radial passage, which an opening of the radial passage into the peripheral surface of the valve body being closed by a seal member which may be formed of an elastic material such as rubber. The seal member is covered by part of the power piston. This construction permits the supply passage to be formed in an inexpensive manner as compared with a formation of a supply passage which extends obliquely through the valve body. The power piston reliably prevents the withdrawal of the seal member from the radial passage.

Supply passage for brake booster of positive pressure type

A power steering apparatus is provided including a control valve or rotary type which controls the supply to or discharge from a power cylinder of a hydraulic fluid. A valve rotor is integrally formed with a projection within the region of a valve sleeve, which is formed with an opening therein to permit the free end of the projection to extend therethrough to the exterior thereof, with the projection being disposed in the opening to leave a given spacing therebetween, as viewed in the direction of rotation of the valve sleeve. Another projection is integrally provided on the valve sleeve, and the both projections are maintained at given positions by the resilience of a spring which is disposed in surrounding relationship with the valve sleeve. As a result, the both projections are provided at axially close locations and in a region where an input and an output shaft abut against each other. This arrangement is preferred in consideration of the mechanical strength. Since the spring is disposed in surrounding relationship with the valve sleeve, the involved construction may be made compact while assuring a resilience of a sufficient magnitude. The C-shaped spring is configured in a manner such that stresses produced therein remain to be uniform throughout the entire body thereof. This allows the spring and hence its mounting structure to be reduced in size.

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Higashimatsuyama, Japan

Yoshio Tobisawa