GB2028740A - A safety steering column for a vehicle - Google Patents

Abstract

In a safety steering column an intermediate shaft 8 comprises two parts 10 and 11 connected to each other by a coupling 12 of square cross-section with a rubber-elastic layer insert (13, Figure 3). The shaft 8 collapses by telescoping, the widening of part 10 and the narrowing of part 11 allowing relative angular displacement. <IMAGE>

Description

SPECIFICATION A safety steering column for a vehicle The invention relates to a safety steering column, for a vehicle, of the kind comprising a steering-shaft portion mounted unyieldingly on the vehicle body and operable by the steering wheel, a steering gear which is mounted on the vehicle frame and of which the input shaft is located substantially in line with said shaft portion and with an intermediate shaft which is disposed between said input shaft and shaft portion, is connected to the latter through a shaft joint and includes a coupling which, in the event of said input shaft closely approaching said shaft portion axially as the result of an accident, becomes automatically disengaged so that the disengaged parts of the intermediate shaft can move freely laterally, at least within limits.German Patent Specification No. 1 927 173 discloses a steering column of the aforesaid kind.

The steering-shaft portion which is unyieldingly mounted on the vehicle body and also the intermediate shaft adjoining it towards the engine compartment and extending towards the steering gear keep away from the interior and from the passengers displacements of the gear-input shaft in the event that the front part of the vehicle becomes collapsed as the result of an accident. Energy-dissipating shaft elements between the steering gear and the unyield ing shaft portion are not required. To reduce the secondary impact of the driver against the steering wheel, impact-absorbing pots, energy-consuming hollow shafts or the like, are provided between the steering wheel and the unyielding shaft portion, forces transmitted to the upper part of the steering column by the impact being diverted into the vehicle body at the point of unyielding mounting.

The divided intermediate shaft, which is in the lower part of the steering column, does not need to absorb any impact energy, but only effectively to keep away from the upper part of the column angular displacements and approaches of the gearinput shaft in the event of accident. It is for this purpose that the automatically disengaging coupling is provided.

In the above-mentioned German Specification, a push-in coupling is provided having axially extend ing torque-transmitting pins on one part of the intermediate shaft and a drive plate into which the pins extend, on the other part. One of the two shaft parts is bent to the side in a Z-shape in the region of the coupling, so that the two coupling halves can engage around each other in hook-like fashion.

When the two shaft parts approach each other, the pins can slide axially out of the plate and the coupling halves become disengaged. After separa tion of said halves, the two shaft parts are free to move laterally and any further displacement of the steering gear, and of the lower part of the intermedi ate shaft connected thereto, due to the accident has no effect on the upper part of the steering column. A disadvantage of this construction is that the coupling and the laterally bent shaft part are relatively complicated and expensive to manufacture.

In another known safety steering column disclosed in German Patent Specification No. 2 315 383, the divided intermediate shaft is a standard telescopic shaft which can be pushed together, but which does not permit of relative angular displacements between the two axially movable shaft halves. In this case, to allow angular displacements of the steering gear on approach thereof to the passenger compartment in the event of an accident, the gear itself is so mounted on the vehicle frame as to be capable of pivoting about a horizontal axis transverse to the direction of travel. This arrangement has the disadvantage that the pivotable mounting of the gear on the vehicle frame requires additional parts with consequent increase in expense.Furthermore, transmission of movement from the steering wheel to the steerable vehicle wheels becomes spongy due to the pivotable mounting of the steering gear. Also, in order to avoid wear and to damp vibration, rubberelastic inserts are fitted at the joints, where particularly high torques occur. Furthermore, lateral movement of the gear-input shaft is possible in a single plane only, namely the vertical plane. It is, however, desirable to have facility for movement in all directions.

Another known safety steering column of the aforesaid kind disclosed in German Specification No.

O.S. 2 535 812 has an undivided intermediate shaft provided with a pre-determined buckling point. This construction has the disadvantage that, in the event of an accident, buckling forces are transmitted from the steering gear rearwardly to the aforesaid steering-shaft portion. Depending on the peripheral location of the steering shaft and on the relative positions of the individual parts in the engine compartment, lateral buckling of the intermediate shaft in the event of an accident may be obstructed so that, despite the buckling point, lateral deflection either does not occur or only after considerable delay and correspondingly high impact forces from the engine compartment act on the unyieldingly mounted portion of the steering shaft.Moreover, this type of construction of the intermediate shaft requires the disposition of shaft joints at both ends of the intermediate shaft, which also involves considerable expense.

The present invention seeks to improve the safety steering column so that it requires as few as possible push-in connections, shaft joints, couplings and the like and so that indispensable connections and elements are of very simple and easily produced designs, whilst the safety function of the steering column is nevertheless fully ensured.

According to the invention, in a safety column of the aforesaid kind, the co-acting ends of the parts of the intermediate shaft, of which parts at least one is hollow, are inserted telescopically one in the other in torsionally fast shape-engaged fashion and telescopically by their inter-engagement constitute the automatically disengageable coupling, the outer shaft part being widened beyond said coupling to its other end to such an extent as will permit of relative axial angular displacements of said shaft parts, while the inner shaft part is narrow over its entire length beyond said coupling.

The joint between the intermediate shaft and the shaft portion unyieldingly mounted on the vehicle body is preferaly a cardan joint.

As a result of the widening of the hollow part of the intermediate shaft and the narrowing of the inner shaft part, a very simple push-in coupling is provided which will become disengaged when the shaft parts approach each other and which also readily allows angular displacements of said shaft parts when the coupling is in the disengaged position. The coupling is itself very simple in construction and said shaft parts are also of very simple design. Their machined ends are integral components of the coupling. Bent formations at parts of the intermediate shaft are avoided. Only a single shaft joint is required in connection with the intermediate shaft and this may be provided by using a rubber elastic coupling. The inner, lower, shaft part, which is preferably solid, may be made in one piece with the input shaft of the steering gear.

One embodiment of invention by way of example will now be more fully described with reference to the accompanying drawings, in which: Figure 1 is a side view of a safety steering column shown in its normal condition, Figure2 is a similar view of the same column in a collapsed condition following an accident, and Figure 3 is a cross-section to a larger scale through the column at the location Ill-Ill in Figure 1.

In the motor car indicated in Figures 1 and 2, a safety steering column is provided which extends from the steering wheel 2 to steering gear 6 mounted on the vehicle chassis 5. It has a steeringshaft portion 4 which is unyieldingly mounted on the vehicle body 3. Between the input shaft 7 of the gear 6 and the shaft portion 4 there is a two-part intermediate shaft 8 which is connected to said shaft portion 4 by a shaft joint 9 in the form of a cardan joint. The parts 10 and 11 of the shaft 8 are connected to each other by a simple push-in coupling 12 which disengages automatically when the shaft parts move closer to each other as the result of an accident. In the example illustrated, the upper shaft part 10 is hollow, while the lower shaft part 11, towards the gear6, is solid and made in one piece with the input shaft 7 of that gear.In the normal condition of the steering column, shown in Figure 1, the horizontal distance between the joint 9 and the centre of the output shaft of the gear 6, measured in the direction of travel of the vehicle, is A. As may be seen the steering column is of substantial length.

By virtue of the coupling 12, the two shaft parts 10 and 11 of the shaft 8 are telescopically collapsible.

From the coupling 12, the hollow shaft part 10 widens towards the joint 9 by the dimension a Figure 3, whereas the solid shaft part 11 is reduced in diameter by the dimension e. In the example, the coupling 12 is of square cross section (Figure 3) with a rubber elastic layer 13 subject to radial pre stressing located between the faces of the square coupling parts whose engagement affords a positive shape-produced connection. As a result, vibrations from the lower shaft part 11 are isolated from the steering column. The layer 13 or, more specifically, its dimension in the radial direction also contributes to the benefit from the amount e of narrowing. The axial extent / (Figure 1 ) of the engaging faces in the coupling 12 is substantially equal to the effective diameter d (Figure 3) at which those faces are located, i.e. the coupling is relatively short in its axial direction.Because of this shortness of the coupling faces and because of the widening of the outer shaft 10 beyond the coupling and the narrowing of the inner shaft part 11, relative angular diaplacements within an angle a (Figure 1) are readily possible between the shaft parts after disengagement of the coupling 12 by approach of the shaft parts to each other as the result of an accident. The horizontal distance A (Figure 1) present when the steering column is in its normal condition can be reduced to the small distance A' (Figure 2) when the front part of the vehicle is crumpled, without effect on the rigidly mounted shaft portion 4.

The widening of the outer shaft part 10 may be of equal extent over the whole length of that part, so that a cylindrical or prismatic section of tube can be used for the widened part. However, starting from the coupling 12, it is also possible to widen the shaft part 10 steadily as in the example illustrated. In any case, the widening, at least in the region directly beyond the coupling 12, must be so great that considerable angular displacements of the shaft parts 10, 11 are possible immediately after complete disengagement of the coupling faces. The length of periphery of the tubular outer shaft part 10 must, therefore be substantially less in the coupling 12 than in a cross section immediately beyond the coupling.In the case of normal telescopic tubular shaft parts shown in longitudinal section, there is, apparently only, a widening beyond the coupling faces, but such appearance is misleading because differences in diameter possibly shown are due to the fact that in the region of the coupling faces, one telescopic tube has been pressed to a square ended shape, whereas, in the region beyond them, there is a circular cross-section with the same length of periphery but a slightly larger diameter. Such apparent widening-out is not intended for, not would it be effective, at least not to an adequate extent, for the purposes of the present invention. A small degree of angular displacement between the shaft parts is also possible, without the widening of the outer shaft part 10, by virtue of the narrowness of the inner shaft part 11.

Because of the simplicity of the connection at the coupling 12, the inner shaft part 11 may, without difficulty, be made in one piece with the gear-input shaft 7, so that additional simplification can be achieved due to the absence of any joint between these two shaft components. Furthermore, because of the simplicity of the push-in connection at the coupling 12, the outer shaft part 10 itself can easily be produced as a tube brought to the required shape. The upper edge of the outer shaft part 10, towards the joint 9, also serves as an integral component of the cardan joint 9. The cross-piece 14 of the cardan joint is pivotably connected to the upper edge of the shaft part 10, for which purpose small bearings lugs 15 are provided on said shaft part at opposite points on its circumference (Figure 3).

Thus the following advantages can be achieved with the above described steering column. The intermediate shaft parts 10, 11 can be of very simple construction and can be easily manufactured and assembled. The inner shaft part 11 may be made in one piece with the intput shaft of the steering gear, so that a push-in connection or other joint between them is obviated. The coupling 12 between the shaft parts 10, 11 is itself simple and inexpensive, but without detriment to the functioning of this coupling.

furthermore, the shaft joint 9 (only one such joint is needed) can be of simpler construction than with conventional designs of safety steering column.

Nevertheless the functional advantages of a safety steering column are fully retained.

The above-described safety steering column has the further advantage that if, in the event of a collision, the lower shaft part 11 becomes detached and approaches the bulkhead 3, it is retained within the hollow shaft part 10 and so cannot dangerously pierce the bulkhead and cause injury to the feet or legs of the driver.

For absorbing impact of the driver in the event of an accident, the wheel 2 may be mounted on the steering column in known manner by means of evergy-dissipating means such, for example, as the deformable frusto-conical pot indicated in the drawings.

Claims (9)

1. A safety steering column for a vehicle comprising a steering-shaft portion mounted unyieldingly on the vehicle body and operable by the steering wheel, a steering gear which is mounted on the vehicle frame and of which the input shaft is located substantially in line with said shaft portion and with an intermediate shaft which is disposed between said input shaft and shaft portion, is connected to the latter through a shaft joint and includes a coupling which, in the event of said input shaft closely approaching said shaft portion axially as the result of an accident, becomes automatically disengaged, so that the disengaged parts of the intermediate shaft can move freely laterally, at least within limits, wherein the co-acting ends of the parts of the intermediate shaft, of which parts at least one is hoilow, are inserted telescopically one in the other in torsionally fast shape-engaged fashion and telescopically by their inter-engagement constitute the automatically disengageable coupling, the outer shaft part being widened beyond said coupling to its other end to such an extent as will permit of relative axial angular displacement of the said shaft parts, while the inner shaft part is narrow over its entire length beyond said coupling.

2. A steering column according to Claim 1, wherein said outer shaft part widens out steadily from said coupling.

3. A steering column according to Claim 1 or 2, wherein said outer shaft part is connected to said steering-shaft portion and said inner shaft part to said gear-input shaft.

4. A steering column according to Claim 1,2 or 3, wherein said inner shaft part is solid and in one piece with said gear-input shaft:

5. A steering column according to any one of Claims 1 to 4, wherein the edge of said outer shaft part remote from said coupling forms an integral part of said shaft joint.

6. A steering column according to any one of Claims 1 to 5, wherein the parts of the intermediate shaft are inserted one in the other with interposition of a rubber-elastic layer.

7. A steering column according to claim 6, wherein the rubber-elastic layer is radially prestressed.

8. A steering column according to any one of Claims 1 to 7, wheren the axial extent of interengagement between said shaft parts in said coupling is not substantially greater than the effective diameter at the shape-engaged faces thereof.

9. A safety steering column substantially as hereinbefore described with reference to the accompanying drawings.