Hydraulically operated power steering system

• US 5,044,456 A
• Filed: 01/31/1990
• Issued: 09/03/1991
• Est. Priority Date: 01/31/1989
• Status: Expired due to Fees

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Hayashi, Yasuhito, Hachisuka, Hiroshi
• Primary Examiner(s): Marmor, Charles A.
• Assistant Examiner(s): Johnson, Victor E.
• Application Number:
  US07/472,872
• Time in Patent Office: 580 Days
• Field of Search: 180/132, 180/141, 180/146, 180/147, 74/388 PS, 60/384, 91/378, 91/380
• US Class Current: 180/417
• CPC Class Codes: B62D 5/087 Sliding spool valves
• CPC Class Codes: B62D 5/24 for worm type

Abstract

A power steering system is provided in which the rack portion of the power piston is strengthened while still shortening the axial length of the power piston associated therewith. This is accomplished by providing a control valve which includes a valve lever received in a power piston of the device which is relatively rotatable with respect to the power piston and moves in an axial direction of the housing with the power piston in response to rotation from an input shaft connected with the steering wheel. The valve lever has an engaging portion which projects outside of the power piston so as to be connected therewith when the valve reciprocates. The reciprocation of the valve will assist in the operation of the power steering unit and provide the power assist. The valve lever has a portion engageable with a pin member received in the valve spool of the control valve so as to reciprocate the control valve. This arrangement permits the rack portion of the power steering unit to be provided with increased strength even though the axial length of the power piston is decreased and the rack and valve operating lever are positioned on the same side of the power steering unit and still permits the size of the system to be decreased.

Claims

1. A hydraulically operated power steering system comprising:

a housing;

an input shaft rotatably mounted in the housing;

a reciprocal hydraulic operating cylinder means for moving a steering link mechanism and having first and second fluid chambers defined in an inner bore of the housing;

a power piston slidably disposed in the inner bore;

a reservoir containing hydraulic fluid;

a fluid pump feeding hydraulic fluid in the reservoir to the cylinder means;

a control valve device including a valve lever disposed in the power piston so as to be relatively rotatable with respect to the power piston and to move in an axial direction of the housing with the power piston in response to rotation of said input shaft, the valve lever having an engaging portion provided with an engaging surface extending in a direction of sliding movement of the power piston;

a valve spool slidably disposed in a bore separate from and perpendicular with respect to the inner bore and slidably engaged with the engaging portion of the valve lever so as to reciprocatingly slide in response to rotation of the input shaft, wherein the hydraulic fluid from the fluid pump is introduced into the first fluid chamber upon the rotation of the input shaft in a first direction and the hydraulic fluid in the second fluid chamber is discharged to the reservoir, the hydraulic fluid from the fluid pump is introduced into the second fluid chamber upon rotation of the input shaft in a second direction when the hydraulic fluid in the first fluid chamber is discharged to the reservoir;

the engaging portion of the valve lever having a slot portion provided with the engaging surface at an inner circumferential portion and connected at an opposite end to the power piston; and

a pin member having a first end portion slidably engaged with the slot portion and a second end portion secured to the valve spool so as to connect the valve lever with the valve spool for movement therewith.

2. A hydraulically operated power steering system as recited in claim 1, wherein the power piston is of a right circular cylinder configuration and the inner bore is formed so as to correspond therewith.

3. A hydraulically operated power steering system as recited in claim 2 wherein the power piston is provided with a slot and the engaging portion extends in the axial direction the slot and is received therein.

4. A hydraulically operated power steering system as recited in claim 3, wherein the pin member protrudes through a hole formed in the housing and the engagement of the engaging portion with the slot is completed before the engagement of the pin with the hole.