Patents by Inventor Yoshio Tobisawa

Yoshio Tobisawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6192783
    Abstract: A brake booster which permits a booster ratio to be changed in two stages. A first spring 25 is disposed between a first plunger plate 24 and the bottom of a stowage 8A of a valve plunger 8. Toward its front end, the outer periphery of the first plunger plate 24 slidably extends through a second plunger plate 26, which is in turn located at its inoperative position shown by a second spring 28 having a greater spring constant than the first spring 25. When the brake booster 1 is actuated, a reaction disc 33 which bulges rearward initially abuts against the first plunger 24, and subsequently, as the first spring 25 is compressed, it abuts against the end faces of the both plunger plates 24, 28. 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.
    Type: Grant
    Filed: July 14, 1999
    Date of Patent: February 27, 2001
    Assignee: Jidosha Kiki Co., Ltd.
    Inventor: Yoshio Tobisawa
  • Patent number: 6042199
    Abstract: 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.
    Type: Grant
    Filed: July 1, 1997
    Date of Patent: March 28, 2000
    Assignee: Jidosha Kiki Co., Ltd.
    Inventor: Yoshio Tobisawa
  • Patent number: 5947566
    Abstract: 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.
    Type: Grant
    Filed: August 12, 1997
    Date of Patent: September 7, 1999
    Assignee: Jidosha Kiki Co., LTD.
    Inventors: Yoshio Tobisawa, Yoshiyasu Takasaki
  • Patent number: 4835970
    Abstract: 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.
    Type: Grant
    Filed: August 7, 1986
    Date of Patent: June 6, 1989
    Assignee: Nissan Motor Co. Ltd.
    Inventors: Morihiko Shimamura, Jun Kubo, Hitoshi Kubota, Norio Fujiki, Yoshio Tobisawa, Yasuki Ishikawa, Kazuyoshi Fukawa
  • Patent number: 4664016
    Abstract: 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.
    Type: Grant
    Filed: February 14, 1985
    Date of Patent: May 12, 1987
    Assignee: Jidoshakiki Co., Ltd.
    Inventors: Yoshio Tobisawa, Hitoshi Kubota, Masatoshi Nakamura
  • Patent number: 4428399
    Abstract: 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.
    Type: Grant
    Filed: July 16, 1981
    Date of Patent: January 31, 1984
    Assignee: Jidosha Kiki Co., Ltd.
    Inventors: Naosuke Masuda, Yoshio Tobisawa, Tadaaki Fujii