Machine element or mechanism – Control lever and linkage systems – Hand operated
Reexamination Certificate
1999-11-10
2001-05-01
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Hand operated
C188S371000, C464S162000
Reexamination Certificate
active
06223619
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering shaft which is telescopically contractible to secure the safety of a driver during an accident, such as a collision of a vehicle.
2. Description of the Related Art
Conventionally, a steering shaft which is made telescopically contractible to secure the safety of a driver during an accident, such as a collision of a vehicle, is known as the steering shaft of a steering apparatus. This steering shaft is arranged such that corresponding end portions of a plurality of shafts are fitted over and coupled to each other by means of splines such that the shafts are slidable relative to each other in their axial direction.
Further, a steering shaft is known in which an injection-molded portion which is formed of a synthetic resin is provided in its sliding portion. The injection-molded portion prevents the occurrence of looseness in a fitting coupling section of the steering shaft in a rotating direction.
An inner shaft and an outer shaft are coupled to each other in the axial direction by a splined structure, and the outer shaft and the inner shaft are fixed in the axial direction by shear pins which are formed of a synthetic resin.
The above-described structure is provided for dampening an axially thrusting force applied from a lower portion of the vehicle during a primary collision, e.g., a thrusting force applied from wheels against the steering shaft via a steering gear box.
A sliding member formed of a synthetic resin for supporting favorable sliding is provided between an opening portion of the outer shaft and the inner shaft in a sliding coupling section of the outer shaft and the inner shaft.
Further, the structure provided is such that shear pins formed by injection of a synthetic resin are provided at appropriate positions on the innermost inner peripheral side of the outer shaft, and the shear pins are sheared during a collision, allowing the outer shaft and the inner shaft to telescopically contract and move relative to each other.
However, the steering shafts of the conventional type have the following drawbacks. First, an appropriate clearance is provided in a splined coupling section between the outer shaft and the inner shaft so as to ensure the slidability of the shafts.
In addition, the axial slidability is made stable and favorable by means of the resin sliding member provided between the opening portion of the outer shaft and the inner shaft. Further, the resin sliding member at the opening portion of the outer shaft blocks the clearance occurring between teeth in the splined fitting section. As a result, it is possible to prevent the looseness in the rotating direction which occurs due to a slight clearance in the rotating direction, which is present between the outer shaft and the inner shaft.
However, in the operation of injecting a resin material into the slight clearance, the maintenance of precise molding conditions is required, and the margin of allowance in the setting of the molding conditions has been very strict.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, it is an object of the present invention to provide a steering shaft which is telescopically contractible during an accident, such as a collision of a vehicle, and which makes it possible to prevent the occurrence of looseness of the inner shaft in the sliding coupling section by filling the sliding coupling section with a sliding resin member, and which allows the inner shaft to operate stably while guiding the axial movement of the shaft, thereby overcoming the above-described drawbacks of the conventional art.
To this end, in accordance with the present invention, there is provided a steering shaft comprising: an outer shaft having an inner splined portion; an inner shaft having a shaft portion and an outer splined portion which are arranged continuously along an axial direction; a retaining portion formed on at least one of the outer splined portion and the shaft portion; a sliding coupling section formed by a coupling portion of the outer shaft and a coupling portion of the inner shaft so as to allow the outer shaft and the inner shaft to be telescopically slidable in the axial direction relative to each other by means of splines; and a sliding resin member which is filled in a space formed in the sliding coupling section between an opening portion of the outer shaft and the retaining portion of the inner shaft.
In accordance with the above-described steering shaft, it is possible to obtain the following advantages. Namely, the movement in the rotating direction of the outer splined portion and the inner splined portion in the sliding coupling section due to a clearance in the rotating direction can be firmly suppressed by the sliding resin member which is provided in the opening portion of the outer shaft in the same way as in the conventional example.
Further, the sliding resin member is provided on the outer splined portion of the inner shaft, and the retaining portion is formed on at least one of the outer splined portion and the shaft portion, with the result that it is possible to prevent the rattling in the axial rotation of the sliding coupling section with a simple arrangement.
In addition, in the processing in which the sliding resin member is filled in the opening portion of the outer shaft of the steering shaft, it is possible to make substantially uniform the influx of the molten sliding resin member in a liquid form into the space between the opening portion of the outer shaft and the inner shaft, thereby improving the moldability.
Furthermore, it is possible to facilitate the management of various molding conditions, such as pressure, when the molten sliding resin member in the liquid form is poured. Additionally, it is possible to further stabilize and improve the slidability in the axially moving direction of the inner shaft.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 4674354 (1987-06-01), Brand
patent: 5228720 (1993-07-01), Sato et al.
patent: 5464251 (1995-11-01), Castellon
patent: 5575501 (1996-11-01), Moriyama et al.
patent: 5640884 (1997-06-01), Fujiu et al.
patent: 5-41700 (1993-02-01), None
patent: 5-332386 (1993-12-01), None
patent: 2513589 (1996-07-01), None
Fujita Katuhiko
Hoshino Mitsuo
Matsumoto Hitoshi
Shibata Kenji
Fenstermacher David
Kabushiki Kaisha Yamada Seisakusho
Lowe Hauptman & Gilman & Berner LLP
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