Land vehicles – Wheeled – Running gear
Reexamination Certificate
1999-09-21
2001-05-29
Rice, Kenneth (Department: 2167)
Land vehicles
Wheeled
Running gear
Reexamination Certificate
active
06237955
ABSTRACT:
This application claims the benefit of Japanese Patent Application No. 10-266249 which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shock absorbing type steering column apparatus for an automobile.
2. Related Background Art
In the event of a collision of an automobile, subsequent to a so-called primary collision that the car collides against another car, there happens a so-called secondary collision that a driver collides against a steering wheel. For the purpose of protecting a life of the driver by minimizing an impact on the driver when the secondary collision happens, there has generally been adopted a system in which a steering shaft with the sheering wheel being fixed to one side end thereof is constructed as a so-called collapsible steering shaft of which an entire length is reduced when a strong impact is applied, and a steering column through which the steering shaft is inserted is structured as a shock absorbing steering column.
What is known as a shock absorbing steering column apparatus used for the purpose described above, is disclosed in, e.g., Japanese Utility Model Laid-Open Publication Nos. 63-76578 and 5-75057. The shock absorbing steering column apparatus, which has hitherto been known by the disclosures in those Publications, has a shock absorbing member provided between the steering column and a member for fixation to a car body etc. Upon the secondary collision, the shock absorbing member permits while being plastically deformed the steering column to displace forward, thereby relieving the impact exerted on the driver's body colliding against the steering wheel.
The conventional shock absorbing steering column apparatus explained above involves the use of the shock absorbing member independently of the steering column, which makes laborious all of parts manufacturing, a parts management and an assembly work and inevitably leads to a rise in costs.
SUMMARY OF THE INVENTION
It is a primary object of the present invention, which was devised under such circumstances, to provide a shock absorbing steering column apparatus capable of its being actualized at low costs by simplifying all of the parts manufacturing, the parts management and the assembly work.
To accomplish the above object, according to one aspect of the present invention, a shock absorbing steering column apparatus comprises a steering column member admitting an insertion of a steering shaft, and a shock absorbing member for permitting the steering column member to displace in an axial direction while being plastically deformed by an impact load applied in the axial direction of the steering column member. The steering column member and the shock absorbing member are integrally formed of a non-ferrous metal.
What can be preferably utilized as this non-ferrous metal may be a light alloy such as a magnesium die casting alloy of which a tensile strength is on the order of 220 MPa (210-230 MPa) and an elongation is approximately 6-10%. Further, what is specifically exemplified as this type of magnesium die casting alloy may be MD2B (magnesium alloy die cast 2-type B) specified by JIS H 5303, or AM50A, AM60A, AM60B etc specified by ASTM. Note that a lower limit of the tensile strength is required to be on the order of 210 MPa in terms of making it compatible to reduce a weight and ensure the strength of the steering column apparatus. By contrast, an upper limit thereof is not particularly regulated. As far as the elongation can be ensured, it is preferable that the tensile strength be higher. Similarly, a lower limit of the elongation is required to be approximately 6% for making the shock absorbing member plastically deformed without causing any cracks in order to ensure a necessary shock absorbing capability. In contrast with this, an upper limit thereof is not particularly regulated. So far as the tensile strength required can be secured, it is preferable that the elongation be larger. To summarize, a physical property required of the non-ferrous metal such as the magnesium die casting alloy etc for carrying out the present invention is that the elongation is over 6% and the tensile strength is over 210 MPa.
Further, a variety of structures of the shock absorbing member may be adopted on condition that the shock absorbing member permits the steering column member to displace forward when an impact load acting forward is applied to the steering column. For example, the following structures (1)-(4) can be considered.
(1) A pair of support walls extend forward at a front side end of the steering column member in a state where a steering shaft inserted through the steering column member is sandwiched in between the support walls from both sides, and one edges of a pair of bent portions each having a convex surface on its front surface side are formed in continuity from the front side ends of these support walls. Then, the other edges of these bent portions are formed in continuity from a fitting member for a fixing support on a car body.
(2) A honeycombed hollowed portion having multiplicity of cylindrical pieces nested in widthwise directions and in front and rear directions, is provided at a front or intermediate portion of the steering column.
(3) A fitting member for a fixing support on the car body through a suspension arm is provided on an upper surface of the front or intermediate portion of the steering column.
(4) The front or intermediate portion of the steering column is inserted through a through-hole formed in an annular or frame-like suspension arm. Then, a lower edge of the through-hole is connected via a connecting member to a lower surface of the steering column. Moreover, a fitting member for the fixing support on the car body is provided at an upper side end of the suspension arm.
In the thus structured shock absorbing steering column apparatus according to the present invention, the steering column member and the shock absorbing member are integrally formed of the non-ferrous metal, whereby the shock absorbing steering column apparatus can be actualized at low costs by simplifying all of the parts manufacturing, the parts management and the assembly work.
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patent: 5378021 (1995-01-01), Yamaguchi et al.
patent: 5497675 (1996-03-01), Brown et al.
patent: 0 240 116 (1987-10-01), None
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patent: 2 247 652 (1992-03-01), None
patent: 2 323 146 (1998-09-01), None
patent: 63-76578 (1988-05-01), None
patent: 5-75057 (1993-10-01), None
Chikuma Isamu
Matsumoto Sakae
Sato Kenji
NSK Ltd.
Rice Kenneth
Vorys Sater Seymour and Pease LLP
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