Stroke absorbing type intermediate shaft for vehicular steering column and method for assembling the same

A structure of a shaft applicable to a steering column, comprising:

• a) a rigid body integrally formed with a first body and a second body, said first body having a substantially circular cross-section, one end of said first body being linked to a first universal joint yoke portion and said second body having a substantially elliptic cross section comprising two generally planar parallel surfaces interconnected with two arcuate surfaces, one end of said second body being integrally linked to the other end of said first body;
• b) an outer tubular envelope one end of which is linked with a second universal joint yoke portion, having a cross section analogous to said elliptic cross section of said second body, and in which said second body is located, a space being provided between the other end of said second body and a peripheral edge of said second universal joint yoke portion;
• c) a vibration damping member intervened between said outer tubular envelope and second body for damping vibrations transmitted from said second body via said first universal joint yoke portion toward said outer tubular envelope;
• d) a housing member intervened between said vibration damping member and said outer tubular envelope for enclosing said vibration damping member;
• and
• e) first means for preventing displacement of said second body from a position within said outer tubular envelope toward a position outside of said outer tubular envelope, the first means including a ring-shaped member, together with said outer tubular envelope, for transmitting rotational force from said second universal joint yoke portion to said first body when said ring-shaped member is contacted with said outer tubular envelope;
• wherein the ring-shaped member is coaxially fitted around a step portion formed on one end of said second body with a gap normally provided against the inner side of said outer tubular envelope and wherein said first means includes a stopper member formed on the other end of said outer tubular envelope for preventing said ring-shaped member from coming out of said second body by said ring-shaped member contacting said stopper member.

A structure of a shaft applicable to a steering column, comprising:

• a) a rigid body integrally formed with a first body and a second body, said first body having a substantially circular cross-section, one end of said first body being linked to a first universal joint yoke portion and said second body having a substantially elliptic cross section comprising two generally planar parallel surfaces interconnected with two arcuate surfaces, one end of said second body being integrally linked to the other end of said first body;
• b) an outer tubular envelope one end of which is linked with a second universal joint yoke portion, having a cross section analogous to said elliptic cross section of said second body, and in which said second body is located, a space being provided between the other end of said second body and a peripheral edge of said second universal joint yoke portion;
• c) a vibration damping member intervened between said outer tubular envelope and second body for damping vibrations transmitted from said second body via said first universal joint yoke portion toward said outer tubular envelope;
• d) a housing member intervened between said vibration damping member and said outer tubular envelope for enclosing said vibration damping member;
• and
• e) first means for preventing displacement of said second body from a position within said outer tubular envelope toward a position outside of said outer tubular envelope, the first means including a ring-shaped member, together with said outer tubular envelope, for transmitting rotational force from said second universal joint yoke portion to said first body when said ring-shaped member is contacted with said outer tubular envelope;
• wherein said housing member has one end linked with a corresponding end edge of said second universal joint yoke portion, said structure further including an inner tubular envelope intervened between the peripheral surface of said second body and vibration damping member, said ring member being fitted around a peripheral surface of a shoulder step portion formed on one end of said inner tubular envelope via a step portion formed on said one end of said second body.

A method for assembling an intermediate shaft located between a steering gear box and a steering shaft of a steering column, comprising the steps of:

• a) forming a shaft body including an axle portion linked to said steering gear box and a portion having approximately elliptic shape of cross section comprising two generally planar parallel surfaces interconnected with two arcuate surfaces, both major and minor axes of which being longer than a diameter of said axle portion;
• b) forming a ring-shaped member having a cross-sectional shape analogous to said elliptic cross-section portion;
• c) providing a housing member;
• d) intervening a vibration damping member between said housing member and elliptic cross-section portion, said vibration damping member damping vibrations transmitted from said steering gear box;
• e) fitting said housing and said vibration damping members and said elliptic cross-section portion into an outer tubular envelope, said ring-shaped member normally having a gap against said outer tubular envelope and transmitting a rotational torque from said outer tubular envelope to said elliptic cross-section portion when said ring-shaped member is contacted with said outer tubular envelope;
• f) linking said outer tubular envelope to a universal joint yoke portion and facing said outer tubular envelope against opposing ends of said housing and vibration damping members, said universal joint yoke portion being contactable against ends of said housing and vibration damping members;
• g) forming a stopper member extended from the end edge of said outer tubular envelope so as to prevent said ring-shaped member from separating from said elliptic cross-section portion;
• wherein said elliptic cross-section portion is formed to have a cross-sectional shape such that two substantially straight sides are parallel to each other and two semi-circular sides are opposite to each other and wherein a length of the major axis of said elliptic cross-section portion is formed to be approximately 1.5 times or more the diameter of the axle portion having a circular cross section;
• wherein said outer tubular envelope is formed so that said outer tubular envelope has one internal end into which said yoke portion is fitted and has the same cross section as said elliptic cross section portion so as to enable insertion of said housing member thereinto under pressure;
• and
• wherein said elliptic cross-section portion is formed to have a step portion, said method further including a step of intervening an inner tubular envelope between said vibration damping member and said elliptic cross-section portion, said inner tubular envelope having a step portion engaging the step portion of said elliptic cross-section portion, said ring-shaped member being fitted around said inner tubular envelope.