Steering shaft with a connecting hub and method for its manufacture

Abstract: An assembly method for assembling a hydraulic steering device control shaft (1) for steering columns; the control shaft (1) having a tubular sleeve (2) and two connecting hubs (3, 4) so fitted to the two axial ends (2a, 2b) of the tubular sleeve as to be coaxial with the longitudinal axis (A) of the tubular sleeve (2); and the assembly method including the steps of: knurling the outer lateral surface (6) of the end portion (3a, 4a) of each of the two hubs (3, 4) to be inserted inside the tubular sleeve (2); forming an annular groove (7) on each outer lateral surface (6) ; and inserting the end portions (3a, 4a) of the two hubs (3, 4) inside the tubular sleeve (2), and deforming the axial ends (2a, 2b) of the tubular sleeve (2) on to the end portions (3a, 4a) of the two hubs (3, 4) so as to form respective permanent-deformation mechanical couplings.

Description: The present invention relates to a hydraulic steering device control shaft for steering columns. As is known, in currently marketed steering columns, the hydraulic steering device control shaft is defined by a cylindrical tubular sleeve, and by two connecting hubs so fixed to the two ends of the sleeve as to be coaxial with the longitudinal sleeve axis. Normally, one of the two connecting hubs is designed for connection to the steering wheel or hydraulic steering device, and the other for connection to a universal joint in turn connected to another mechanical member. At present, the connecting hubs are welded to the two ends of the cylindrical tubular sleeve using an assembly method comprising the steps of: forming, in the lateral wall of and close to the two axial ends of the sleeve, through holes perpendicular to the longitudinal sleeve axis; washing the sleeve to remove any leftover grease or debris which might impair the welds; inserting the two hubs partly inside the corresponding axial ends of the tubular sleeve; and fixing the two hubs integrally to the sleeve by welding inside the through holes formed close to the two axial ends of the sleeve. Since the welding step normally results in local deformation in turn resulting in misalignment of the connecting hubs with respect to the cylindrical tubular sleeve, the current assembly method also comprises testing the straightness of hydraulic steering device control shafts, and grinding hydraulic steering device control shafts to ensure that the connecting hubs are perfectly coaxial with the longitudinal axis of the cylindrical tubular sleeve. Hydraulic steering device control shafts of the above type have the major drawback of being extremely expensive to produce and so greatly increasing the overall production cost of the steering column. It is an object of the present invention to provide a hydraulic steering device control shaft which is cheaper to produce. GB-A-1264 707 discloses a shaft comprising a tubular sleeve and at least one connecting hub so fitted to an axial end of said tubular sleeve as to be coaxial with the longitudinal axis of the tubular sleeve; said connecting hub having an end portion so sized as to be inserted inside the tubular sleeve; wherein said end portion of the connecting hub is connected to the tubular sleeve by a permanent-deformation mechanical coupling; said axial end of the tubular sleeve, in fact, being deformed on to said end portion of the connecting hub. The present invention provides the hydraulic steering device control shaft of claim 1 and the method of assembling a hydraulic steering device control shaft for steering columns of claim 4. According to the present invention, there is provided an assembly method for assembling a hydraulic steering device control shaft for steering columns, the control shaft comprising a tubular sleeve and at least one connecting hub so fitted to an axial end of said tubular sleeve as to be coaxial with the longitudinal axis of the tubular sleeve; said connecting hub having an end portion so sized as to be inserted inside the tubular sleeve; and said assembly method being characterized by comprising the steps of: forming an annular groove on the outer lateral surface of the end portion of said connecting hub; diagonally cross - knurling the outer lateral surface of the end portion of said connecting hub; and with the connecting hub maintained coaxial with the longitudinal axis of the tubular sleeve, deforming the axial end of said tubular sleeve on to the end portion of said connecting hub so as to form a permanent-deformation mechanical coupling. A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a side view, with parts in section and parts removed for clarity, of a hydraulic steering device control shaft for steering columns in accordance with the teachings of the present invention; Figure 2 shows an exploded view in perspective of the Figure 1 control shaft. Number 1 in Figures 1 and 2 indicates as a whole a hydraulic steering device control shaft particularly suitable for a known steering column (not shown). Control shaft 1 comprises a cylindrical tubular sleeve 2; and two connecting hubs 3 and 4 so fitted to the two axial ends 2a and 2b of the sleeve as to be coaxial with the longitudinal axis A of tubular sleeve 2. In the example shown, hub 3 is designed for connection to any known steering wheel (not shown); and hub 4 is designed for connection to a universal joint 5 in turn connected to a known hydraulic steering device (not shown). With reference to Figures 1 and 2, both hubs 3 and 4 are cylindrical, variable-diameter elements comprising a first end portion 3a, 4a sized for insertion inside tubular sleeve 2 and for connection to tubular sleeve 2 by permanently deforming the axial ends 2a and 2b of the sleeve; and a second end portion 3b, 4b sized for mechanical connection to the steering wheel, hydraulic steering device or universal joint 5. With reference to Figures 1 and 2, end portion 3a of hub 3 and end portion 4a of hub 4 each have an outside diameter approximately equal to but no larger than the inside diameter of tubular sleeve 2, and each have a knurled outer lateral surface 6 and an annular groove 7 formed on outer lateral surface 6. Axial ends 2a and 2b of tubular sleeve 2 are deformable on to end portion 3a of hub 3 and end portion 4a of hub 4 respectively, so as to make hubs 3 and 4 axially and angularly integral with tubular sleeve 2. The respective knurled outer lateral surfaces 6 and respective annular grooves 7 on end portions 3a and 4a of hubs 3 and 4, in fact, provide for maximizing grip of the permanent-deformation mechanical couplings formed between hubs 3 and 4 and tubular sleeve 2. In the example shown, control shaft 1 also comprises two spacer bushes (or bearings) : a first, indicated 8, is fitted to end portion 3a of hub 3 and interposed between axial end 2a of tubular sleeve 2 and an annular shoulder 9 separating end portions 3a and 3b of hub 3; and a second, indicated 10, is fitted to end portion 4a of hub 4 and interposed between axial end 2b of tubular sleeve 2 and an annular shoulder 11 separating end portions 4a and 4b of hub 4. Control shaft 1 is assembled as follows: the knurling and annular groove 7 are formed on outer lateral surface 6 of end portion 3a of hub 3, and on outer lateral surface 6 of end portion 4a of hub 4; end portions 3a and 4a are then inserted inside axial ends 2a and 2b of tubular sleeve 2 with the interposition of spacer bushes (or bearings) 8 and 10, if provided; and keeping hubs 3 and 4 coaxial with longitudinal axis A of tubular sleeve 2, axial ends 2a and 2b of tubular sleeve 2 are deformed on to end portion 3a of hub 3 and end portion 4a of hub 4 respectively, so as to form respective permanent-deformation mechanical couplings. The knurling on outer lateral surfaces 6 of end portions 3a and 4a makes hubs 3 and 4 angularly integral with tubular sleeve 2, while annular grooves 7 make hubs 3 and 4 axially integral with tubular sleeve 2. When axial ends 2a and 2b of tubular sleeve 2 are deformed, in fact, annular grooves 7 are engaged partly by the wall of tubular sleeve 2 to prevent withdrawal of hubs 3 and 4. The advantages of control shaft 1 as described and illustrated herein are obvious: the manufacturing process is much simpler and faster than those currently employed, thus greatly reducing production cost. Clearly, changes may be made to hydraulic steering device control shaft 1 as described and illustrated herein without, however, departing from the scope of the present invention.

Claims: A hydraulic steering device control shaft (1) comprising a tubular sleeve (2) and at least one connecting hub (3, 4) so fitted to an axial end (2a, 2b) of said tubular sleeve (2) as to be coaxial with the longitudinal axis (A) of the tubular sleeve (2); said connecting hub (3, 4) having an end portion (3a, 4a) so sized as to be inserted inside the tubular sleeve (2) and the axial end (2a, 2b) of the tubular sleeve (2) being deformed on to said end portion (3a, 4a) of the connecting hub (3, 4) to connect the said connecting hub (3, 4) to the tubular sleeve (2) by a permanent-deformation mechanical coupling; said hydraulic steering device control shaft (1) being characterized in that said end portion (3a, 4a) of the connecting hub (3, 4) has an outside diameter approximately equal to but no larger than the inside diameter of the tubular sleeve (2); and that the outer lateral surface (6) of said end portion (3a, 4a) is diagonally cross-knurled. A hydraulic steering device control shaft as claimed in Claim 1, characterized in that the outer lateral surface (6) of said end portion (3a, 4a) of the connecting hub (3, 4) has an annular groove (7). A hydraulic steering device control shaft as claimed in any one of the foregoing Claims, characterized by comprising two connecting hubs (3) (4), each of which is so fitted to a respective axial end (2a)(2b) of the tubular sleeve (2) as to be coaxial with the longitudinal axis (A) of the tubular sleeve. An assembly method for assembling a hydraulic steering device control shaft (1) for steering columns, the control shaft (1) comprising a tubular sleeve (2) and at least one connecting hub (3, 4) so fitted to an axial end (2a, 2b) of said tubular sleeve (2) as to be coaxial with the longitudinal axis (A) of the tubular sleeve (2); said connecting hub (3, 4) having an end portion (3a, 4a) so sized as to be inserted inside the tubular sleeve (2); and said assembly method being characterized by comprising the steps of: forming an annular groove (7) on the outer lateral surface (6) of the end portion (3a, 4a) of said connecting hub (3, 4); diagonally cross-knurling the outer lateral surface (6) of the end portion (3a, 4a) of said connecting hub (3, 4); and with the connecting hub (3, 4) maintained coaxial with the longitudinal axis (A) of the tubular sleeve (2), deforming the axial end (2a, 2b) of said tubular sleeve (2) on to the end portion (3a, 4a) of said connecting hub (3, 4) so as to form a permanent-deformation mechanical coupling.

Inventors: CAVAZZONI PIERO, CAVAZZONI, PIERO
Applicants: IM EL S R L, IM.EL. S.R.L.
Application year: 2001
Main classification: B62D1
IPC codes: F16B17, B62D1, F16D1