Energy absorbing system for a vehicle steering column

A device is disclosed for adjusting an energy absorbing system of an automobile vehicle steering column mounted in a support assembly which is connected to and attached to the structure of the vehicle by fixing devices each having a respective fixing axis. At least one fixing device includes at least one energy absorbing capsule disposed in the support assembly on a retaining axis and clamped in the support assembly by fastening devices. The fixing axis and the retaining axis coincide. The fastening devices are independent of the fixing devices and include a nut and a rod shoulder in order to allow adjustment to achieve the required clamping of the fastening devices to obtain the required energy absorption. Adjustment of the clamping of the energy absorbing capsule or capsules is therefore independent of the clamping of the devices for fixing the support assembly to the vehicle structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for adjusting an energy absorbing system of an automobile vehicle steering column. The steering column is mounted in a support assembly which is connected and fastened to the structure of the vehicle by fixing means, with at least one energy absorbing capsule disposed on one of the fixing means.

2. Description of the Prior Art

There are steering columns which have one or more energy absorbing capsules mounted directly on the fixing axis or axes. The energy absorption of each capsule therefore depends on clamping the support assembly to the structure of the vehicle.

In mass production, as in the automobile industry, it is difficult to achieve and to guarantee precise and constant fixing tightness and therefore a precise and constant clamping pressure on the energy absorbing capsule or capsules. As the energy absorption of these capsules depends directly on the clamping, this results in imprecise absorption of energy. In existing and future automobile vehicles, however, it is increasingly imperative for passive safety characteristics to be accurate and effective.

OBJECT OF THE INVENTION

The object of the present invention is to provide a device for adjusting an energy absorbing system that avoids the drawbacks described hereinabove and that provides for easy and precise adjustment of the required value of the energy absorption.

SUMMARY OF THE INVENTION

According to an embodiment, the device for adjusting an energy absorbing system relates to an automobile vehicle steering column. The steering column is mounted in a support assembly which is connected to and attached to the structure of the vehicle by plural fixing means each having a respective fixing axis. In this embodiment, at least one of said fixing means includes at least one energy absorbing capsule which is disposed in the support assembly on a retaining axis. Said at least one energy absorbing capsule is clamped in the support assembly by fastening means, the fixing axis and the retaining axis coinciding. Said fastening means are independent of the respective fixing means in order to allow adjustment to achieve the required clamping of the fastening means to obtain the required energy absorption, i.e. adjustment of the clamping of said at least one energy absorbing capsule is independent of a clamping value of the fixing means of the support assembly to the vehicle structure.

Advantageously, at least one of the fixing means includes two energy absorbing capsules.

According to the invention, the fastening means include a retaining rod provided at one end with a shoulder and at its other end with a threaded portion which receives a nut adapted to clamp the energy absorbing capsule or capsules to the support assembly with the required force. The energy absorbing capsule or capsules are provided with a hole through which the retaining rod passes so it can be mounted on the retaining rod between the shoulder and the nut. The retaining rod has a hole through it for the corresponding means for fixing the support assembly to the vehicle structure.

According to an embodiment particularly interesting of the invention, the retaining rod has a circular section whose diameter is slightly less than the diameter of the hole through the energy absorbing capsule or capsules, which are therefore centered on the retaining rod. The shoulder has a circular ring section whose outside diameter is substantially equal to the outside diameter of the circular periphery of the energy absorbing capsule or capsules and whose inside diameter is substantially equal to the diameter of the hole through the capsule or capsules. The retaining rod has at one end a fine pitch thread which receives a nut whose overall size is substantially equal to the overall size of the shoulder so as to have the same surface area of contact with said at least one energy absorbing capsule and one of said nut or said shoulder, or with the two capsules.

Moreover according to the invention, the retaining rod is extended at the same end as the shoulder by a handling portion with at least one handling hole substantially perpendicular to the retaining axis, i.e. the fixing axis; the periphery of the handling portion is a circular cylindrical bearing surface which guides a corresponding energy absorbing winding.

Lastly in order to improve the manufacture cost, the retaining rod, the shoulder and the handling portion constitute one and the same mechanical part.

To facilitate the fitting of the energy absorbing capsule or capsules, each energy absorbing capsule has an axial protuberance penetrating a corresponding hole in the support assembly to prevent metallic contact between fixed parts and mobile parts in the event of an impact.

The adjustment device according to the invention has at least one fixing means including two energy absorbing capsules each disposed against the corresponding face of the support assembly.

According to an architecture of the invention, the steering column comprises a steering shaft rotably mounted about a steering axis in a body tube. The body tube is disposed between two uprights connected by a connecting member. The two uprights and the connecting member form part of the support assembly. The two uprights are substantially parallel to the vertical plane passing through the steering axis. Each upright has an external flange substantially perpendicular to said upright. In each of the external flanges, there is an oblong hole whose cross section axis is the clamping axis of the corresponding energy absorbing capsules, i.e. the fixing axis, the oblong hole having a shape which is elongate parallel to the upright in order to allow the required movement of the mobile support member in the event of an impact.

Moreover, each of the two oblong holes is open at the same end as the steering wheel.

According to a variant of embodiment of the invention, the two external flanges are parts of a common base which is welded to the connecting member and to each of the two uprights and the support assembly fixing means are fixing bolts.

Lastly according to an architecture of the invention, and for each of the two fixing axes, the fixing means, the energy absorbing capsule or capsules and the fastening means are identical.

The device in accordance with the invention for adjusting an energy absorbing system of a steering column therefore has the advantage of allowing the mobile support member to slide in the fixed support member with a controlled force. The capsule fixing system is adjustable in the factory and is independent of the mounting on the vehicle.

The two capsules disposed on each side of the U-shaped lug of the mobile support member have a rod passed through them with a shoulder whose outside diameter is substantially equal to the outside diameter of the capsules and whose inside diameter is substantially equal to the inside diameter of the capsules.

The endless thread for adjusting the clamping of the nut as a function of the required sliding force is formed in alignment with the outside diameter serving to center the capsules.

Choosing the dimensions of each of the rods enables the steering column to be fixed to the vehicle by fixing bolts passing through the rods without affecting the previously set sliding force of the U-shaped lug.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The device in accordance with the invention for adjusting an energy absorbing system relates more particularly to an automobile vehicle steering column, one embodiment of which is shown inFIGS. 1 and 2.

In all embodiments of the invention the steering column is always made up of a steering shaft1which turns about a steering axis3. This steering shaft is rotably mounted in a body tube2. A vertical plane passing through the steering axis is denoted4.

The body tube is disposed in a support assembly7which is fixed to the structure10of the vehicle. The support assembly7comprises two members: A fixed support member8and a mobile support member9. The fixed support member8and the mobile support member9are connected to the vehicle structure or chassis10and remain fixed relative to the structure10in normal use of the vehicle. It is only in the event of an impact that the mobile support assembly9is moved relative to the fixed support assembly8via the energy absorbing system.

In the remainder of the description, and for the same member, terms such as “internal” or “interior” in relation to the steering axis3or the vertical plane4containing the steering axis3mean nearer that axis or that plane, and terms such as “external” or “exterior” mean farther away from it. For the same member, terms such as “front” mean nearer the steering box26, and terms such as “rear” mean nearer the steering wheel25.

In another embodiment of the invention, not shown in the figures, the support assembly comprises only the mobile support member, which is fixed directly to the structure of the vehicle.

The body tube2is disposed between two uprights11and12which are joined by a connecting member13. The two uprights11,12and the connecting member13are parts of the mobile support member9.

The two uprights11,12are substantially parallel to the vertical plane4passing through the steering axis3, and the connecting member13is substantially perpendicular to said vertical plane4. Each upright11,12(FIGS. 5 and 6) has a respective external flange15and16that is substantially perpendicular to the corresponding upright11,12and to the vertical plane4.

In each of the external flanges15and16there is an oblong hole or slot17,18whose shape is elongate parallel to the vertical plane4, i.e., to the corresponding upright11,12. Each of the two oblong slots17and18is open at the same end as the steering wheel25.

The two external flanges15and16are part of a common base14. The base14is welded to the connecting member13and to each of the two uprights11and12.

In the case of a steering column whose position can be adjusted, as shown inFIGS. 1 and 2, the body tube2is clamped and immobilized in the chosen position by a clamping system27whose clamping axis28is substantially perpendicular to the vertical plane4.

The support assembly7is connected and attached to the structure of the vehicle10by plural fixing means each having a respective fixing axis. In the figures there are two fixing means in the form of fixing bolts53each of which has a respective fixing axis5,6.

According to the invention, at least one of the fixing means includes at least one annular energy absorbing capsule31,32. (FIGS. 3 and 4) which is disposed in said support assembly7, along its retaining axis, and which is clamped in said support assembly7by fastening means.

For each of the two fixing means, consisting of the corresponding fixing bolt53with the corresponding fixing axis5,6, the fastening means include a retaining rod41. Each retaining rod41has a first end portion44, an intermediate portion49provided with an annular shoulder42, and a second end portion50having an externally threaded portion43, which receives a nut51in order to clamp the two energy absorbing capsules31,32to the support assembly7with the required value. Each of the energy absorbing capsules31,32has a hole39,40through which the retaining rod41passes so that the capsule can be mounted on said retaining rod41between the shoulder42and the adjacent lower surface52of the nut51. Said retaining rod41has a bore or hole46through which the corresponding fixing bolt53of the support assembly7on the structure of the vehicle10passes.

The retaining rod41has a circular section whose diameter is slightly less than the diameter of the holes39and40through the two energy absorbing capsules31and32which are thus centered on said retaining rod41. The shoulder42has a circular ring section whose outside diameter is substantially equal to the outside diameter of the circular periphery of the energy absorbing capsules31and32and whose inside diameter is substantially equal to the diameter of the holes39and40through said capsules31and32. The retaining rod41has one end50with a fine pitch thread43which receives the nut51whose overall size is substantially equal to the overall size of the shoulder42, so as to have the same surface area of contact with each of the two capsules31and32, or when there is only one capsule, with said capsule31and the nut51, or with said capsule32and the shoulder42.

The retaining rod41is extended on the same side as the shoulder42by the first end portion44that defines a handling portion with a handling hole45substantially perpendicular to the retaining axis, i.e. to the fixing axis5or6.

The retaining rod41, the shoulder42and the handling portion44constitute one and the same mechanical part.

Each energy absorbing capsule31,32has a corresponding axial protuberance37,38which enters a corresponding oblong slot or hole17,18in the support assembly7.

Accordingly, as shown inFIGS. 3 and 4, each retaining rod41, is provided with a first energy absorbing capsule31, of which a bearing face33is pressed against the bearing face47of the shoulder and another bearing face35is pressed against a lower face21,22of the corresponding external flange15,16, the protuberance37of said capsule31engaging in the oblong hole17,18in the external flange15,16. Each oblong hole17,18has a cross section whose axis is the corresponding fixing axis5,6of the energy absorbing capsules31and32and is slightly larger than axial protuberance37and38.

In the same way, each retaining rod41is provided with a second energy absorbing capsule32, a bearing face36of which is pressed against an upper face19,20of the corresponding external flange15,16. The protuberance38of said capsule32engages in the oblong hole17,18in the external flange15,16and is slightly smaller than said oblong hole17,18. The axial protuberances37and38prevent metallic contact between the fixed parts and the mobile parts in the event of an impact.

The corresponding nut51screws onto the threaded end43of the corresponding retaining rod41, pressing against the bearing face34of the second energy absorbing capsule32. The clamping of the two energy absorbing capsules31,32against the upper face19,20and against the lower face21,22of the corresponding external flange15,16is adjusted by tightening the nut51to the required value, the retaining rod41being prevented from rotating by means of the handling hole45. Each fixing bolt53with its shank54and its threaded part57then immobilizes this assembly on the fixed support member8and the structure of the vehicle10. The bearing face56of the head55of the fixing bolt53, which can be hexagonal, is pressed against the handling portion44via a conical washer58, in order to retain a corresponding energy absorbing elastic helical spring59which is previously mounted on the circular cylindrical bearing surface constituting the periphery of said handling portion44, in order to guide said helical spring59.

The fixing bolt53is immobilized by the bearing face48of the threaded end50pressed against the lower face24of the fixed support member8, whose upper face23is pressed against the structure10of the vehicle.

The fastening means are therefore independent of the corresponding fixing means, in order to adjust the clamping force of said fastening means to obtain the required energy absorption, i.e. so that the clamping of the energy absorbing capsules31and32can be adjusted independently of the clamping of said fixing means53of the support assembly7to the structure10of the vehicle.

The two capsules31and32disposed one on each side of the U-shaped lug of the mobile support member9have a rod41passed through them provided with a shoulder42whose outside diameter is substantially equal to the outside diameter of the capsules31and32and whose inside diameter is substantially equal to the inside diameter of the capsules31and32.

The fine pitch thread43for adjusting the clamping of the nut51as a function of the required sliding force is aligned with the exterior diameter for centering said capsules31and32.

The dimensions of each of the rods41mean that the steering column can be fixed to the vehicle by fixing bolts53passing through said rods41without affecting the previously set sliding force of the U-shaped lug.

In the embodiment shown in the figures, the fixing means, the energy absorbing capsules and the fastening means for said capsules are identical on each of the two fixing axes5and6.