FIELD OF THE DISCLOSURE

[0001] The disclosure relates generally to the field of steering column assemblies for motor vehicles. More specifically, the disclosure relates to spindles for steering column assemblies.

SUMMARY

[0002] The following presents a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to identify critical elements of the disclosure or to delineate the scope of the disclosure. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented elsewhere.

[0003] According to an embodiment, a steering spindle includes a hollow outer tube and a hollow inner tube. The hollow outer tube has a lengthening section and an attachment section, and the attachment section has a transition portion and a connection portion. The lengthening section adjoins the attachment section at an end of the transition portion, and the transition portion is between the lengthening section and the connection portion. An outer diameter of the connection portion is smaller than an outer diameter of the lengthening section. The lengthening section has first and second portions, with the second portion being between the first portion and the transition portion, and the outer tube terminates at an end of the connection portion. The hollow inner tube is press-fit into the outer tube, and an end of the inner tube is adjacent the end of the transition portion. The inner tube does not extend into either the attachment section or the first portion, and a length of the second portion is at least equal to a length of the inner tube.

[0004] In an embodiment, a length of the second portion is greater than a length of the attachment section. The length of the second portion may be at least three times a length of the attachment section.

[0005] In an embodiment, an inner diameter of the inner tube is larger than an inner diameter of the connection portion.

[0006] In an embodiment, the outer tube is constructed of metal and the inner tube is constructed of metal.

[0007] In an embodiment, the natural frequency of the connection portion is at least 55 Hz in a vertical direction and at least 57 Hz in a lateral direction.

[000S] In an embodiment, the natural frequency of the connection portion is at least 69 Hz in a vertical direction and at least 71 Hz in a lateral direction.

[0009] According to another embodiment, a steering column assembly includes a jacket, a bearing, and a steering spindle rotatably supported by the bearing and at least partially extending inside the jacket. The steering spindle includes a hollow outer tube and a hollow inner tube. The hollow outer tube has a lengthening section and an attachment section, and the attachment section has a transition portion and a connection portion. The lengthening section adjoins the attachment section at an end of the transition portion, and the transition portion is between the lengthening section and the connection portion. An outer diameter of the connection portion is smaller than an outer diameter of the lengthening section. The lengthening section has first and second portions, with the second portion being between the first portion and the transition portion, and the outer tube terminates at an end of the connection portion. The hollow inner tube is press-fit into the outer tube, and an end of the inner tube is adjacent the end of the transition portion. The inner tube does not extend into either the attachment section or the first portion, and a length of the second portion is at least equal to a length of the inner tube.

[0010] In an embodiment, at least part of the second portion is cantilevered from the bearing, and a distance between the bearing and the end of the connection portion is at least 70 mm.

[0011] In an embodiment, the natural frequency of the connection portion is at least 55 Hz in a vertical direction and at least 57 Hz in a lateral direction.

[0012] In an embodiment, the natural frequency of the connection portion is at least 69 Hz in a vertical direction and at least 71 Hz in a lateral direction.

[0013] In an embodiment, a length of the second portion is greater than a length of the attachment section, and an inner diameter of the inner tube is larger than an inner diameter of the connection portion.

[0014] In an embodiment, the outer tube is constructed of metal and the inner tube is constructed of metal.

[0015] According to still another embodiment, a method of creating a steering spindle includes the steps of providing a hollow outer tube and a hollow inner tube. The outer tube has a uniform inner diameter and a longitudinal axis, and the outer tube terminates at an end, with an attachment section of the outer tube extending from the end of the outer tube. The inner tube has a uniform outer diameter and a longitudinal axis, and the outer diameter of the inner tube is larger than the inner diameter of the outer tube. The inner tube is press-fit entirely into the outer tube with the longitudinal axis of the inner tube being coaxial with the longitudinal axis of the outer tube. The inner tube is press-fit such that the attachment section is free of the inner tube, and such that an end of the inner tube is adjacent the attachment section. After the inner tube is positioned, transition and connection portions are formed— but only in the attachment section.

[0016] In an embodiment, the natural frequency of the connection portion is at least 55 Hz in a vertical direction and at least 57 Hz in a lateral direction.

[0017] In an embodiment, the natural frequency of the connection portion after the inner tube is press fit into the outer tube is at least 69 Hz in a vertical direction and at least 71 Hz in a lateral direction.

[0018] In an embodiment, a length of the second portion is greater than a length of the attachment section.

[0019] In an embodiment, the step of press-fitting comprises press-fitting the inner tube into the outer tube through the outer tube end and the attachment section.

[0020] In an embodiment, the step of forming comprises hammer-forming.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a perspective view of part of a steering column assembly, according to an embodiment of the present disclosure.

[0022] FIG. 2 is a section view taken from FIG. 1.

DETAILED DESCRIPTION

[0023] The natural frequency and stiffness of an automobile’s steering column, and in particular an automobile’s steering spindle, have a substantial effect on driver satisfaction.

Higher natural frequencies and stiffness aid in minimizing shake and the transmission of vibrations, and significantly contribute to a pleasurable driving experience. Natural frequency and stiffness has traditionally be increased through material selection or by increasing the thickness of the spindle’s cross section. Yet non-traditional materials may be expensive or have other limitations, increasing cross-section thickness may undesirably increase weight or cost, and designs for modem steering column assemblies require increasingly longer spindles.

[0024] FIGs. 1 and 2 illustrate a steering column assembly 100 according to one embodiment. The steering column assembly 100 broadly includes a jacket 110 and a bearing 115 rotatably supporting a steering shaft (or“spindle”) 120 such that the spindle 120 at least partially extends inside the jacket 110.

[0025] The spindle 120 has hollow outer tube 122 and a hollow inner tube 142 press- fit into the outer tube 122. While the outer and inner tubes 122, 142 may be constructed of any appropriate materials, it may be particularly desirable for the tubes 122, 142 to be constructed of metal (including metal alloys). The outer tube 122 has a lengthening section 123 and an attachment section 133, and the attachment section 133 in turn has a transition portion 135 and a connection portion 137.

[0026] The lengthening section 123 adjoins the attachment section 133 at an end l35a of the transition portion 135, and the transition portion 135 is between the lengthening section 123 and the connection portion 137. The outer tube 122 terminates at an end 137b of the connection portion 137, and the connection portion 137 has an outer diameter l37a that is smaller than an outer diameter 123 a of the lengthening section 123.

[0027] The lengthening section 123 has first and second portions 124, 126, and the second portion 126 is between the first portion 124 and the transition portion 135. A length l26a of the second portion 126 is at least equal to (i.e., is not less than) a length l42a of the inner tube 142, and the length l26a of the second portion 126 is greater than a length l33a of the attachment section 133. In some embodiments, it may be particularly desirable for the length l26a of the second portion 126 to be at least three times the length 133a of the attachment section 133. At least part of the second portion 126 is cantilevered from the bearing 115, and in some embodiments it may be particularly desirable for a distance 118 between the bearing 115 and the end 137b of the connection portion 137 to be at least 70 mm and for the natural frequency of the connection portion 137 to be at least 55 Hz in a vertical direction and at least 57 Hz in a lateral direction. In some embodiments, it may be desirable for the natural frequency of the connection portion 137 to be at least 69 Hz in a vertical direction and at least 71 Hz in a lateral direction.

[0028] The inner tube 142 does not extend into either the attachment section 133 or the first portion 124, and an end l42b of the inner tube 142 is adjacent the end l35a of the transition portion 135. An inner diameter l42c of the inner tube 142 is larger than an inner diameter 137c of the connection portion 137.

[0029] To create the steering spindle 120, the hollow outer tube 122 initially has generally uniform inner and outer diameters and terminates at the end 137b (from which the attachment section 133 extends). And the hollow inner tube 142 initially has generally uniform inner and outer diameters, with the outer diameter of the inner tube being larger than the inner diameter of the outer tube. The inner tube 142 is press-fit entirely into the outer tube 122 with a longitudinal axis 149 of the inner tube 142 being coaxial with a longitudinal axis 129 of the outer tube 122. The inner tube 142 is sufficiently press-fit into the outer tube 122 such that the attachment section 133 is free of the inner tube 142 and the end l42b of the inner tube 142 is adjacent the attachment section 133. It may be particularly desirable for the inner tube 142 to be press-fit into the outer tube 122 by being inserted through the end 137b and the attachment section 133. Once the inner tube 142 is appropriately located, the transition portion 135 and the connection portion 137 are formed only in the attachment section 133. The transition portion 135 and the connection portion 137 may be hammer- formed or created in any other appropriate manner, whether now existing or later developed. It may be particularly desirable in some embodiments for the natural frequency of the connection portion 137 after the inner tube 142 is press-fit into the outer tube 122 and the transition and connection portions 135, 137 are formed to be at least 55 Hz in a vertical direction and at least 57 Hz in a lateral direction. It may be particularly desirable in other embodiments for the natural frequency of the connection portion 137 after the inner tube 142 is press-fit into the outer tube 122 and the transition and connection portions 135, 137 are formed to be at least 69 Hz in a vertical direction and at least 71 Hz in a lateral direction.

[0030] The outer tube 122 may be coupled with an inner shaft for torque transmitting, which is connectable with an input shaft of a steering gear, and a universal joint may be arranged between the inner shaft and the input shaft of the steering gear. In an embodiment, the outer tube 122 and the inner shaft are telescopic to each other.

[0031] Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present disclosure. Embodiments of the present disclosure have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present disclosure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. The specific configurations and contours set forth in the accompanying drawings are illustrative and not limiting.