Motor vehicles – Steering gear – With electric power assist
Reexamination Certificate
2000-03-10
2001-08-14
Dickson, Paul N. (Department: 3618)
Motor vehicles
Steering gear
With electric power assist
C180S400000, C280S093515
Reexamination Certificate
active
06273210
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a center take-off type power steering apparatus such as a hydraulic power steering apparatus, an electromotive power steering apparatus, and the like.
2. Description of the Related Art
Conventionally, in power steering apparats, a rack shaft is supported by a gear housing to be linearly movable, a power cylinder is coupled to the gear housing, the rack shaft is caused to pass through the power cylinder and propelling force generated by the power cylinder is imparted on the rack shaft, so that steering force can be assisted. In a center take-off type power steering apparatus of the power steering apparatuses which has been disclosed in Japanese Utility Model Application Laid-Open (JU-A) No. 57174275, a coupling member for coupling left and right tie-rods to an intermediate portion of the rack shaft is provided so as to be movable in a reciprocating manner within a window-shaped portion formed in a side wall of the power cylinder.
In the conventional art, however, there are the following drawbacks. (1) In the center takeoff type power steering apparatus, when positions of a gear housing and a power cylinder relative to each other regarding rotation direction about a common central axis thereof are even slightly deviated from each other at a connecting portion between the gear housing and the power cylinder, a coupling member between tie-rods and a rack shaft can not be moved smoothly due to the coupling member striking a window-shaped portion in an offset manner and the like so that the coupling member may be damaged. (2) A bellows-shape boot covering the window-shaped portion of the power cylinder comprises a singly body, one end of the boot being fastened to a mounting boss provided at the gear housing and the other end thereof being fastened to a mounting boss provided at the power cylinder. Bolts or the like for fixing tie-rod mounting members to the above-mentioned coupling member penetrate an intermediate portion of the boot. For this reason, holes of the boot which the above bolts or the like penetrate expand due to repetition of movement of the coupling member following leftward and rightward movements of the rack shaft, so that the boot is fatigued. As a result, the water-proof sealing property of the boot is damaged so that water or other foreign material may enter into the boot. (3) In the center take-off type power steering apparatus, the tie-rods are arranged in the vicinity of the boot, while the boot comprises an elastic body such as rubber. In order to prevent an intermediate portion of the boot positioned between both end portions thereof from deforming or hanging, it is desired to make the outer diameter of the boot large and make the inner diameter thereof small. In this case, however, the likely drawback is that the outer surface of the boot and the tie-rods interfere with each other, and the inner face of the boot and the rack shaft come in contact with each other.
SUMMARY OF THE INVENTION
An object of the present invention is to secure relative positioning between a gear housing and a power cylinder to allow a coupling portion between tie-rods and a rack shaft to move smoothly within a window-shaped portion of the power cylinder in a center take-off type power steering apparatus.
Also, another object of the invention is to improve durability of a boot in a center take-off type power steering apparatus.
Furthermore, still another object of the invention is to prevent a boot and tie-rods from interfering with each other, or the boot and a rack shaft from contacting each other, in a center take-off type power steering apparatus.
According to the present invention, there is provided a center take-off type power steering apparatus where a rack shaft is supported by a gear housing so as to be linearly movable, a power cylinder is coupled to the gear housing, and the rack shaft penetrates the power cylinder, so that propelling force generated by the power cylinder can be imparted on the rack shaft to assist steering force. A coupling member for coupling left and right tie-rods to an intermediate portion of the rack shaft is provided so as to be movable in a reciprocating manner within a window-shaped portion formed at a side wall of the power cylinder. The gear housing and the power cylinder are positioned regarding rotation direction of the power cylinder about a common center axis of the both by a pin forcibly fitted into one of the gear housing and the power cylinder. The gear housing and the power cylinder are fixed regarding the axial direction of the power cylinder by causing a stopper ring provided at one of the gear housing and the power cylinder and a lock nut screwed to the other to abut on each other.
According to the present invention, there is provided a center take-off type power steering apparatus where a rack shaft is supported by a gear housing so as to be linearly movable, a power cylinder is coupled to the gear housing, and the rack shaft penetrates the power cylinder, so that propelling force generated by the power cylinder can be imparted on the rack shaft to assist steering force. A coupling member for coupling left and right tie-rods to an intermediate portion of the rack shaft is provided so as to be movable in a reciprocating manner within a window-shaped portion formed at a side wall of the power cylinder. A boot holder fixed to the coupling member for the left and right tie-rods is disposed so as to surround the power cylinder. Each of the left and right boots for covering the window-shaped portion of the power cylinder at left and right sides of the boot holder respectively extends between one of first mounting portions of the gear housing and the power cylinder, and a corresponding one of second mounting portions of the boot holder.
Furthermore, according to the present invention, there is provided a bellows-shaped boot used for a power steering apparatus where a rack shaft is supported by a gear housing so as to be linearly movable, a power cylinder is coupled to the gear housing, and the rack shaft penetrates the power cylinder, so that propelling force generated by the power cylinder can be imparted on the rack shaft to assist steering force. Where a boot extends between a first mounting portion and a second mounting portion, an outer shape of the boot is made straight from the first mounting portion towards the second mounting portion, and an inner shape thereof comprises a tapered portion with a diameter reduced gradually from the first mounting portion and a straight portion, with almost the same diameter as the minimum inner diameter of the tapered portion extending straight to the second mounting portion.
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patent: 10-315995 (1998-12-01), None
Hamano Satoshi
Saito Tatsuya
Dickson Paul N.
Orum & Roth
Showa Corporation
Yeagley Daniel
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