Title of Invention	"RIGIDITY ENHANCING STRUCTURE FOR STEERING COLUMN SUPPORT MEMBER OF IN A VEHICLE"
Abstract	The disclosed structure enhances the rigidity of a support member which supports a steering column in a vehicle and which extends in the direction of the width of the vehicle body and which is connected at two ends thereof to the vehicle body. In this structure, at least one of the two ends of the support member is interference-fitted to a bracket provided on the vehicle body.

Full Text

The present invention relates to a rigidity enhancing structure for a steering column support member of a vehicle and, more particularly, to a structure suitable for enhancing the rigidity of a member that supports a steering column of a passenger vehicle. BACKGROUND Japanese Patent Application Laid open No. HEI 8-183478 discloses a steering column of a passenger vehicle that is supported by a tubular support member extending in the direction of the width of the vehicle body. The support member is connected at both ends, thereof to front pillars by brackets or fixtures. An intermediate portion of the support member is supported by a brace connected to the floor of the vehicle body. During the running of a vehicle, the steering column may vibrate up and down. Vibrations of the steering column propagate to the support member, thereby vibrating the support member. It is conventionally considered that the support member is vibrated up and down by the steering column. Therefore, the two end portions of the support member connected to the front pillars and the brace connected to the intermediate portion of the support member are designed and formed to cope with the up-down vibrations of the support member. However, the present inventors have found that about 80% of the vibrations of the steering column acts on the support member so as to twist the support member and only about 20% thereof acts to vibrate the support member up and down. Accordingly, the conventional countermeasures against vibrations of the steering column have effect only on part of the vibrations that moves the support member up and down. In other words, the effect of the conventional countermeasures is not sufficient. Accordingly, it is the object of the invention to provide a rigidity enhancing structure for a vehicular steering column support member that has good effect particularly on vibrations that act on the support member in a twisting manner. To achieve the said objective this invention provides a rigidity enhancing structure for a steering column support member in a vehicle, comprising: a support member that supports a steering column, and extends in a direction of a width of a vehicle body, said support member is connected at two end portions of the vehicle body, characterized in that at least one of the two end portions of the support member is connected to the vehicle body by a interference fit connection. The support member is further supported at its intermediate portion by a brace such that the brace transmits to the support member a vibration that twists the support member around its axis in a direction opposite to the direction in which a vibration transmitted from a steering column to the support member twists the support member. The brace may be connected to the support member so that the brace receives substantially no bending force that is produced by a vibration that twists the support member. The brace may be connected to an outer surface of the support member so that an axis of the brace extends in a direction of a tangent of the outer surface of the support member. In the conventional art, both ends of a support member are fastened to a vehicle body simply by using fixtures or brackets, whereas, the instant invention employs at least one interference fit connection. When the support member, connected to the vehicle body by interference fit, receives vibrations from the steering column that acts to twist the support member around its axis, friction forces occur on the interface between at least one end portion of the support member and the vehicle body, thereby resisting the twisting caused by the vibrations. Said friction force produced against a twist by the interference-fit connection is greater than the friction force produced by the simply fastened connection, thereby correspondingly enhancing the rigidity. The brace is connected to the support member so that the brace applies to the support member a vibration that acts on the support member in a manner opposite to a manner in which a vibration from the steering column acts on the support member so as to twist the support member around the axis of the support member. For example, when the support member receives from the steering column a twisting vibration that twists the support member, the brace applies to the support member a load that acts in a direction opposite to the twisting direction of the vibration from the steering column, thereby forcibly reducing the twisting of the support member. Thus, the rigidity of the support member can be enhanced. Furthermore, if the brace is connected to the support member so that the brace receives substantially no bending force which is produced by a vibration that twists the support member, the brace is prevented from being deformed by a bending moment. Therefore, the brace applies a correspondingly increased load to the support member and further reduce the twisting. The invention will now be described with reference to the accompanying drawings. Fig. 1 is a sectional view of a rigidity enhancing structure for a steering column support member in a vehicle according to the invention; Fig. 2 is a perspective view of the rigidity enhancing structure shown in Fig. 1, wherein the support member is going to be connected to the vehicle body; Fig. 3 is a partially sectional side view of a sectional view of a rigidity enhancing structure for a steering column support member in a vehicle according to a preferred embodiment of the invention; and Fig. 4 is a perspective view of the rigidity enhancing structure shown in Fig. 3. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings. Referring to the sectional view in Fig. 1 and the perspective view in Fig. 2, a rigidity enhancing structure is designed to enhance the rigidity of a support member 12 supporting a steering column 10 of a vehicle and extending in the direction of the width of the vehicle body. The support member 12 is equipped with a bracket 13 to which the steering column 10 is connected. A steering wheel 14 is connected to a shaft (not shown) extending through the interior of the steering column 10, whereby the steering wheel 14 is connected to a steering device. The support member 12 is connected at both end portions thereof (only one end portion is shown in Fig. 2) to the vehicle body. The connection of the support member 12 to the vehicle body is achieved by interference fit of at least one end portion 16 of the support member 12. The other end portion of the support member 12 may be connected to the vehicle body by interference fit or by simple fastening using a fixture. In the embodiment shown in Figs. 1 and 2, the support member 12 formed by a first tubular portion 18 and a smaller-diameter second tubular portion 19 that are formed by steel pipes firmly interconnected or formed together as a single unit. The first portion 18 of the support member 12 is positioned near the steering column 10, that is, the end portion 16 of the first portion 18 is at the driver's seat side. The end portion 16 of the first portion 18 is interference-fitted to a bracket 24 connected to a front pillar 22. If one of the two end portions of the support member 12 is connected by interference fit, that end portion is preferably at the drive's seat side. In fig. 1, the bracket 24 is formed from a steel plate so that the bracket 24 has a semi-circular recessed portion 25 that conforms to an outer peripheral surface of the end portion 16 of the first portion 18. The recessed portion 25 has an arcuate inner peripheral surface that has a radius B with the center being on the axis C of the end portion 16 when the end portion 16 of the support member 12 is fitted to the recessed portion 25. The end portion 16 has an outer peripheral surface that has a radius A from the center axis C of the end portion 16. The radius A of the outer peripheral surface of the end portion 16 is greater than the radius B of the inner peripheral surface of the recessed portion 25 of the bracket 24. The difference (A -B) between the two radii may be set to a value within the range of about 0.5 mm to about 1.5 mm. The end portion 16 of the support member 12 and the recessed portion 25 of the bracket 24 are so formed that the aforementioned radius relation is established. A substantially half of the peripheral surface of The end portion 16 is pressingly fitted into the recessed portion 25 to achieve interference fit connection. Subsequently, a fixture 26 is placed over the end portion 16, and bolts 28 are inserted into holes of the fixture 26 and holes 27 of the bracket 24. The bolts 28 are then screwed into nuts 30 fixed to the reverse side of the bracket 24 to tightly fasten the fixture 26 and the end portion 16 of the support member 12. In a rigidity enhancing structure according to the preferred embodiment of the invention shown in the side view in Fig. 3 and the perspective view in Fig. 4, a support member 12 supports a steering column 10 of a vehicle, and extends in the direction of the width of the vehicle body. The support member 12 is connected at both end portions 16, 17 thereof to brackets 32, 34 of the vehicle body, by using fixtures 36, 38. The support member 12 is supported, at its intermediate portion, by a brace 40. It is preferred that the end portion 16 and the bracket 32 or the end portion 17 and the bracket 34 or both pairs be coupled by interference fit connection as described above. The brace 40 is connected to the support member 12 so as to transmit to the support member 12 a vibration that twists the support member 12 around its axis in a direction opposite to the direction in which a vibration transmitted from the steering column 10 to the support member 12 twists the support member 12. That is, the brace 40 is connected to the support member 12 in a manner as follows. When a vibration from the steering column 10 acts on the support member 12 so as to twist the support member 12 clockwise, the brace 40 applies to the support member 12 a vibration in a direction D (counterclockwise) as indicated in Fig. 3. When a vibration from the steering column 10 acts on the support member 12 so as to twist the support member 12 counterclockwise, the brace 40 applies to the support member 12 a vibration in the direction E (clockwise). In this embodiment, the brace 40 has a generally tubular shape, and it is connected to the support member 12 in such a manner that the brace 40 will receive no substantial bending force produced by vibrations that twist the support member 12. The brace 40 may be formed from a cylindrical steel pipe, or by bending a steel plate into a pipe shape and appropriately welding the edges. A mounting seat 42 is welded to a rearward portion of the outer peripheral surface of the support member 12, the rearward portion facing rearward relative to the vehicle body. A bolt 44 is then welded to the mounting seat 42 so that the axis of the bolt 44 lies substantially in the horizontal plane that contains the axis C of the support member 12. In Fig. 3, a front portion of the vehicle is to the left as indicated by an arrow. An upper end portion 41 of the brace 40 is flattened. The brace 40 is substantially vertically disposed so that two opposite flat surfaces 45, 46 of the upper end portion 41 face forward and rearward relative to the vehicle body. The upper end portion 41 is connected to the bolt 44 by inserting the bolt 44 into a hole formed in the upper end portion 41. The upper end portion 41 has been shaped so that when the brace 40 is connected to the bolt 44 as described above, the axis C1 of the brace 40 extends through a center portion between the two surfaces 45, 46 of the upper end portion 41. Subsequently, the brace 40 is fastened to the support member 12 by tightly screwing a nut 48 onto the bolt 44. This manner of connection prevents the brace 40 from receiving a bending force when the support member 12 receives twisting vibrations. A lower end portion of the brace 40 is flattened so that the flattened lower end portion is twisted 90° from the upper end portion 41. The lower end portion of the brace 40 is connected to a floor of the vehicle body. When the steering column 10 vibrates up and down during the running of the vehicle, the support member 12 vibrates in such a manner that the support member 12 is twisted around its axis, and simultaneously vibrates up and down. In the embodiment shown in Figs. 1 and 2, since the end portion 16 of the support member 12 is interference-fitted to the bracket 24 of the vehicle body, friction forces occur there between to act against twisting vibrations, thereby reducing the twisting vibrations of the support member 12. In the embodiment shown in Figs. 3 and 4, the brace 40 is connected to the support member 12 so that the brace 40 applies to the support member 12 vibrations in a manner opposite to the manner in which twisting vibrations from the steering column 10 act on the support member 12. Therefore, this embodiment reduces the twisting vibrations of the support member 12 in an active manner. In experiments, a structure in which at least one end portion of a support member was interference-fitted to a bracket of a vehicle body, as in the embodiment shown in figs 1 & 2, increased the resonance frequency by 2.4 Hz in comparison with a structure in which both ends of a support member were fastened to brackets simply by using fixtures. Thus, the structure according to this embodiment substantially enhanced the rigidity. A structure in which a brace was provided for applying to a support member vibrations in directions opposite to the directions of twisting vibrations from a steering column as in the second embodiment increased the resonance frequency by 0.6 Hz in comparison with a structure in which a brace was disposed under a support member. Thus, the structure according to the second embodiment also substantially enhanced the rigidity. In the embodiment shown in figs. 3 & 4, the brace 40 is disposed rearward of the support member 12 and connected to the bolt 44 protruding rearward from the support member 12. This construction allows the brace 40 to be mounted from the rear of the support member 12, thereby improving the workability. However, it is also possible to dispose the brace 40 forward of the support member 12 and connect the brace 40 thereto so that the brace 40 applies to the support member 12 vibrations in a manner opposite to the manner in which twisting vibrations from the steering column 10 act on the support member 12 so as to twist the support member 12 around its axis. While the present invention has been described with reference to what are presently considered to be preferred embodiments thereof, it is to be understood that the claimed invention is not limited to the disclosed embodiments or constructions and that the discussed combination of features might not be absolutely necessary for the inventive solution. We Claim: A rigidity enhancing structure for a steering column support member of a vehicle, comprising: a support member that supports a steering column, and extends in a direction of a width of a vehicle body, said support member is connected at two end portions of the vehicle body, characterized in that at least one of the two end portions of the support member is connected to the vehicle body by a interference fit connection. A rigidity enhancing structure for a steering column support member in a vehicle as claimed in claim 1 wherein the interference fit connection consists of a fixing bracket having a semi-circular recessed portion that conforms to an outer peripheral surface of the end portion of the support member, the radius of inner peripheral surface of the said recessed portion is smaller than the radius of the outer peripheral surface of the end portion of the support member for press fitting the said support member and the difference between the two radii range from 0.5 mm to 1.5 mm. 3 A rigidity enhancing structure for a steering column support member in a vehicle as claimed in claim 1 wherein the said support member is formed by two tubular members formed by steel pipes firmly interconnected or formed together as a single unit, the diameter of one tubular member is greater than the other tubular member. 4. A rigidity enhancing structure for a steering column support member in a vehicle as claimed in claim 1 wherein the other end portion of the support member is connected to the vehicle body by a known fastening means or a fixture provided on the vehicle body. 5. A rigidity enhancing structure for a steering column support member in a vehicle as claimed in claim 1 wherein the support member is supported at its intermediate portion by a brace such that the brace transmits to the support member a vibration that twists the support member around its axis in a direction opposite to the direction in which a vibration transmitted from a steering column to the support member twists the support member. 6. A rigidity enhancing structure for a steering column support member in a vehicle as claimed in claim 5, wherein the brace is connected to the support member in a manner, as herein described, such that brace receives substantially no bending force produced by vibrations that twists the support member. 7. A rigidity enhancing structure for a steering column support member in a vehicle as claimed in claim 5, wherein the brace is connected to an outer surface of the support member so that an axis of the brace extends in a direction of a tangent of the outer surface of the support member. 8. A rigidity enhancing structure for a steering column support member in a vehicle substantially as herein described with reference to the accompanying drawings.

Documents:

3615-del-1998-abstract.pdf

3615-del-1998-claims.pdf

3615-del-1998-correspondence-others.pdf

3615-del-1998-correspondence-po.pdf

3615-del-1998-description (complete).pdf

3615-del-1998-drawings.pdf

3615-del-1998-form-1.pdf

3615-del-1998-form-19.pdf

3615-del-1998-form-2.pdf

3615-del-1998-form-3.pdf

3615-del-1998-form-4.pdf

3615-del-1998-form-6.pdf

3615-del-1998-gpa.pdf