Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
2000-03-03
2003-06-10
Hong, John C. (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C029S505000, C285S001000, C280S777000
Reexamination Certificate
active
06574850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shock absorbing type steering shaft which is capable of contracting in the axial direction upon collision of the car owing to the impact of the collision, and a method of manufacturing such steering shaft. Particularly, the present invention relates to a shock absorbing type steering shaft capable of stabilizing a collapse load which acts at the time of collision of the car even when the inner shaft of the car is a solid shaft so as to reduce the manufacturing cost, as well as a method of manufacturing such steering shaft.
2. Related Background Art
In a steering apparatus for a car, there is provided a shock absorbing type steering shaft which can be contracted in the axial direction upon collision, by the impact of the collision.
An example of a method for manufacturing such shock absorbing type steering shaft is disclosed in Japanese Patent Application Laid-Open No. 52-25330, in which a solid inner shaft having a non-circular cross section in a substantially oval form is inserted into a tubular outer shaft having a non-circular cross section in a substantially oval form, the outer shaft is pressed by a pressing member inwardly from the outer side thereof in the radial direction to plastically deform the both shafts locally, and then both the shafts are pressure-fixed to each other elastically by the portions thus plastically deformed. In this manner, while a relative movement between the both shafts in the axial direction is prevented normally, the plastically deformed portions are caused to collapse at the time of collision of the car, whereby the inner shaft is moved into the outer shaft to contract the entire length of the steering shaft, thereby absorbing the shock.
However, according to the manufacturing method disclosed above, since the plastic deforming is conducted in the state that the solid inner shaft is inserted in the outer shaft, an amount of plastic deformation of the outer shaft is not sufficient, so that there is a possibility of backlash in the pressure contact and fixation of both the shafts.
In Japanese Patent Application Laid-Open No. 1-58373, in the state that a jig is inserted in a tubular outer shaft having a circular cross section, the outer shaft is pressed inwardly in the radial direction by the pressing member from the outer side thereof, so that the outer shaft is plastically deformed locally to have a non-circular cross section. Subsequently, the jig is removed, and the solid inner shaft having a circular cross section is inserted into the outer shaft, whereby the inner shaft is pressure-fixed to the portion of the outer shaft which has been plastically deformed to the non-circular cross section.
However, according to the manufacturing method disclosed above, it is required to once insert the jig into the outer shaft and, after the plastic processing, to remove the jig. Thus, the manufacturing process becomes complicated for such steps of inserting and removing the jig and, as a result, the manufacturing cost is increased.
Further, in Japanese Patent Application Laid-Open No. 9-272447, an inward protrusion is formed in the radial direction on a tubular outer shaft having a circular cross section with a female serration, an annular recess from which a serration has been removed is formed on the outer peripheral surface of a solid inner shaft having a circular cross section with a male serration, and the annular recess of the inner shaft is caused to engage with the inward protrusion in the radial direction of this outer shaft in such a manner that the both shafts are pressure-contacted and fixed with pressure to each other.
However, according to the manufacturing method disclosed above, it is required to remove a part of the serration from the male serration formed on the outer peripheral surface of the inner shaft and to form the annular recess, which may result in an increase in the manufacturing cost.
Further, according to Japanese Patent Application Laid-Open. No. 10-181615 (which has been converted from an application for a Japanese Utility Model Registration filed in 1992), the tip end of a tubular outer shaft having a circular cross section and the tip end of a solid inner shaft having a circular cross section are plastically deformed to have non-circular (flat or elliptic) cross sections, respectively. On the other hand, inner portions other than the tip ends of the both shafts are maintained to have circular cross sections. Then, the inner shaft is inserted into the outer shaft, and the portion having the non-circular cross section of the outer shaft is strongly pressure-contacted and fixed to the portion having the circular cross section of the inner shaft and the portion having the circular cross section of the outer shaft is strongly pressure-contacted and fixed to the portion having the non-circular cross section of the inner shaft, respectively, whereby the both shafts are pressure-contacted and fixed to each other.
However, according to the manufacturing method disclosed above, the plastic deforming of the tip end of the outer shaft and the plastic deforming of the tip end of the inner shaft are conducted separately, so that the manufacturing process becomes complicated, which may bring about an increase in the manufacturing cost.
Further, in Japanese Patent Application Laid-Open No. 8-91230, like in Japanese Patent Application Laid-Open No. 10-181615, the tip end of the outer shaft and the tip end of the inner shaft are plastically deformed to have non-circular cross sections. However, as a step of this plastic deforming, the tip end of the inner shaft is inserted in the tip end of the outer shaft to be maintained in an overlapping state, and these both overlapping tip ends are pressed inwardly in the radial direction by the pressing members to be plastically deformed to have non-circular cross sections. Thus, the both tip ends are plastically deformed at a time to simplify the manufacturing process.
However, according to the manufacturing method disclosed above, the inner shaft is required to be hollow and, when the inner shaft is solid, even if the tip end of the solid inner shaft is inserted into the tip end of the tubular outer shaft and the both overlapping tip ends are pressed inwardly in the radial direction by the pressing members, the plastic deforming can not be conducted satisfactorily with respect to the solid inner shaft.
Further, according to Japanese Patent Application Laid-Open No. 10-147245, like in Japanese Patent Application Laid-Open No. 8-91230 mentioned above, the both tip ends are plastically deformed by the pressing members at a time in the state that the both tip ends of the outer shaft and the inner shaft overlap each other. It is further arranged to adjust the collapse load by adjusting the press load of the pressing members.
However, according to the manufacturing method disclosed above, like in Japanese Patent Application Laid-Open No. 8-91230, when the inner shaft is solid, the plastic deforming can not be conducted satisfactorily.
Incidentally, when the inner shaft is a solid shaft, it is comparatively difficult to plastically deform the both tip ends at a time in the state that the tip ends of the both shafts overlap each other, like Japanese Patent Application Laid-Open no. 8-91230. However, a part of the above Japanese Patent Application Laid-Open No. 8-91230 discloses a method for pressure-contacting and fixing the solid inner shaft and the tubular outer shaft to each other, as shown in FIG.
19
.
A bottomed hole
103
is formed at the tip end
101
a
of the solid inner shaft
101
having a circular cross section with a male serration
102
, and the tip end
101
a
of this inner shaft
101
is fitted in the tip end
104
a
of the tubular outer shaft
104
having a circular cross section with a female serration
105
. These both overlapping tip ends
101
a
and
104
a
are pressed by the pressing members
106
and
106
from the upper and lower directions thereof so that the both tip ends
101
a
and
104
a
Hong John C.
Miles & Stockbridge P.C.
NSK Ltd.
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