WO1990012722A1

WO1990012722A1 - Steering column decoupler

Info

Publication number: WO1990012722A1
Application number: PCT/GB1990/000616
Authority: WO
Inventors: Ronald Alan Cook; Bryan Jones; Bernard Haldric; Jacques Foulquier; Frédéric LECERF
Original assignee: Ford Motor Company Limited; Ford Werke A.G.; Ford France S.A.; Ford Motor Company; Ford Motor Company Of Canada Limited; Nacam S.A.
Priority date: 1989-04-21
Filing date: 1990-04-20
Publication date: 1990-11-01
Also published as: GB8909167D0; GB2231004A

Abstract

A decoupler for a steering column of a motor vehicle has a collar (40) on one part (26) which holds a neck (42) on the other part (32). A packing (44) is fitted between the two parts to prevent there being any play between them. The collar has a circumferential opening (48), and a shank (46) on the other part can pass through this opening to allow the two parts to completely separate from one another in the event of a crash.

Description

STEERING COLUMN DECOUPLER

TECHNICAL FIELD

This invention relates to a decoupler for a steering column of a motor vehicle. The steering column decoupler normally provides a rigid joint between the upper and lower parts of the column, but is designed so as to release the upper part from the lower part in the event of a crash, in order to prevent injury arising from the driver impacting upon the steering wheel.

BACKGROUND OF THE INVENTION

A steering column decoupler is known from GB-PS-2 028 740. In this patent an inner shaft part is connected to an outer shaft part by a simple push-in coupling. When the steering column described in this patent experiences an impact which tends to move the shaft parts closer to one another, then one part moves inside the other and both the possible distance by which the coupling can be shortened and the possible relative angles which can be accommodated are strictly limited by the construction. Furthermore, the use a widened upper shaft part will take up space in a part of the vehicle where space is at a premium.

Another steering column decoupler is known from GB-A-2 194 922. In this patent two components are held ^'together by a shear pin and by a band which secures one component inside the other. When this decoupler shortens, the shear pin breaks and the band across the components also breaks. However the extent of possible movement after breakage of the shear pin appears to be limited and because of the metal to metal contact between the two parts, it may be difficult to achieve the desired absence of play between the two components under normal operation. -2-

SUMMARY OF THE INVENTION

According to the present invention, there is provided a steering column decoupler comprising a first end having a non-round collar portion, a second end having a shank with a neck at the end of the shank, the neck being non-round and being fitted in the collar, and a packing piece between the neck and the collar to prevent play therebetween, the collar portion having an opening at one part of its circumference, the circumferential width of the opening being less than the a cross-sectional dimension of the neck and greater than a cross-sectional dimension of the shank so that the second end can separate from the first end when the shank is received within the collar portion.

Because the collar is non-round, the form-fitting ,engagement between the collar and the neck transmits the normal, rotationally-acting, forces experienced by the decoupler.

The packing piece is preferably a plastics sleeve which can be fitted aver the end of the neck before the neck is inserted in the collar.

Both the collar portion and the neck portion may be angularly offset from a straight line joining the two ends of the decoupl.gr so that as the two ends of the decoupler approach one another, the neck and the collar are each caused to move in a direction away from the straight line so that the two parts become completely separated from one another.

It may be necessary to incorporate a shear pin between the neck, and the collar to provide an initial resistance to -3-

relative movement which has to be overcome before decoupling action can begin.

The cross section of the collar is preferably formed by folding an initially flat piece of metal to form a non- round cross section, and the neck will have a corresponding cross section which may be formed by forging. The packing piece preferably completely surrounds the neck and has contours which ensure that there is no play between the neck and the collar.

At each end of the decoupler, there is preferably a forked yoke for attachment to another steering column component through a conventional universal or Cardan joint.

BRIEF DESCRIPTIUON OF THE DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a general arrangement of a motor vehicle steering column;

Figure 2 is a side view of a steering column decoupler in accordance with the invention;

Figure 3 is a plan view of the decoupler of Figure 2;

Figure 4 is a cross section through the decoupler of Figures 2 and 3, on the line IV-IV from Figure 3;

Figure 5 is a cross section through the decoupler on the lines V-V from Figure 3; -4-

Figure 6 is a view corresponding to Figure 5 but showing an alternative embodiment;

Figure 7 is a plan view of another embodiment of decoupler in accordance with the invention;

5 ^" Figure 8 is a side view of the decoupler of Figure 7; and

Figures 9, 10 and 11 are cross sectional views through the decoupler of Figure 8 on the section lines IX, X and XI.

10 DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows schematically the location of the decoupler

10 in a car which has a front bulkhead 14, a steering column 16 with a steering wheel 18, a steering gear 20 and ^r rbad wheels 22. The decoupler is fitted between the column

IS 16 and an input member 24 of the steering gear 20. For example, this input member 24 could be the pinion shaft of a rack and pinion steering gear. The two ends of the decoupler are provided with respective universal joints by means of which the decoupler is connected to the column 16

20 and to the input member 24 respectively.

Looking now at Figures 2 and 3, the decoupler 10 has a first part 26 which is to be connected at the bottom end of the steering column 16 through a yoke 28 and a universal joint 30, and a second part 32 which is to be connected to

25 the Input member 24 of the steering gear 20 through a yoke 34 and a universal joint 36. A coupling member 38 is also connected to the universal joint 36 and will be directly connected to a shaft which forms part of the input member 24, in a manner which is not part of this invention. In

30 Figures 1 and 2, the yokes 28 and 34 are shown as being at right angles to one another, but any relative angular rotation is possible, depending on the reguire ents of the steering column 16 and the input member 24. Any required angular position can be set by rotating the yoke 34 on the end of the part 32 before fixing it in position.

The first part 26 has a collar 40 which (as can be seen in Figure 4) does not completely surround a neck 42 on the second part 32. A plastics sleeve 44 acts as a packing between the collar 40 and the neck 42 to take up any play.

The neck 42 is formed on the end of a shaft 46. The shaft has a cross-section in the form of a circle with two opposite flats 47. Figure 3 indicates with "a" the "across-flats" dimension of this shaft 46, and it will be seen from Figure 3 that this dimension is smaller than the width "b" of an opening 48 in the collar 40.

In use, the two parts 26 and 32 will remain in the relative positions shown in Figures 2 and 3 under normal conditions. This position will be maintained partly because the positions of the lower end of the steering column 16 and of the input member 24 are fixed, and partly because of the friction produced by the packing 44 between itself and the neck 42 and the collar 40 respectively. However in the event of an accident where a force is applied which tends to shorten the distance between the two ends of the decoupler, the frictional force between the two parts will be overcome by the externally applied force and the neck 42 will slide axially in the collar. At a certain position, the neck will pass out of the collar so that only the shank 46 lies within the collar. However because the shank dimension "a" is narrower than the collar opening "b" the shank can and will escape from the collar. A line 50 shown in Figure 2 represents the direction in which this relative sliding movement between the two parts will take place, and it will be seen that the end of the part 26 and the end of the part 32 can follow this path when the two parts decouple so that the ends of these two parts do not come into contact with the opposite part (for example as is the case in GB-A-2 194 922) and that therefore there will be no limitation to the relative movement which can take place between the two ends of the decoupler.

Figure 5 shows the packing piece 44 in the form of a plastics sleeve which is either placed over the end of the neck 42 before the neck is inserted in the collar, or is placed in the collar before the neck is inserted.

Figure 6 shows an alternative arrangement where a two-layer plastics packing 52 is moulded onto the outer surface of the neck 46 or onto the inner surface of the collar 40.

The cross sectional shape of the neck 42 and of the collar

40 are shown in Figure 4. It will be seen that the collar has two opposite recesses in which lobes 54 of the neck are received. Figure 4 also indicates with a chain-dotted circle 56 the "swept diameter" of the decoupler, that is the diameter of the cylindrical space which is required to enabl x.e the decoupler to rotate fully to transmit steering actions from the steering wheel 18 to the steering gear 20. It will be seen that this swept diameter 56 is only very slightly larger than the largest dimension of the collar 40. This is a considerable advantage in vehicle construction, because it means that other components can be positioned close to the decoupler without interfering with the normal rotational action of the decoupler. In Figures 7 and 8, the parts which correspond to parts already described with reference to Figures 2 and 3 are indicated by the same reference numerals, but with the prefix "1".

The dimensions of the shank 132 which connects the neck 142 with the yoke 128 need to be related to the dimensions of the collar 140 in order for the decoupler to be effective. The width A of the shank 132 is slightly narrower than the width A' of the gap 144 in the collar 140, and the length B of the straight shank should be greater than the length B¹ of the gap 144. As a result of these conditions, the two parts can be completely decoupled by the shank 132 moving in a radial direction out of the collar after a relative axial movement.

In addition to the sleeve 144, the two parts 126 and 146 are secured together by means of two shear pins 141. These shear pins, if found to be necessary, may be of metal or plastics. There may be one or two or even more shear pins, but it is desirable to keep the number to a minimum to avoid unnecessary complexity, and indeed the embodiment of Figures 2 and 3 operates without any shear pin at all.

The decouplers shown in the drawings have a small number of component parts and can be manufactured and assembled without any complicated manufacturing techniques. Moreover the force required to produce separation can be easily set by suitable choice of the material of the plastics sleeve and by controlling the shaping of the collar.

Claims

WHAT IS CLAIMED IS:

1. A steering column decoupler (10, 110) comprising a first end (26, 126) having a non-round collar portion (40, 140), a second end (32, 132) having a shank (46, 146) with a neck (42, 142) at the end of the shank, the neck being non-round and being fitted in the collar, and a packing piece (44, 144), between the neck and the collar to prevent

: * play therebetween, characterized in that the collar portion (40, 140) has an opening (48, 148) at one part of its 10 circumference, the circumferential width (b) of the opening being less than a cross-sectional dimension of the neck and greater than a cross-sectional dimension (a) of the shank so that the second end can separate from the first end when the shank is received within the collar portion.

15 .

2. ^~~The steering column decoupler of Claim 1 wherein the packing piece is a plastics sleeve (44, 144) which can be fitted over the end of the neck (42, 142) before the neck

^•. , ^* is. inserted in the collar (40, 140).

3. ^" The steering column decoupler of Claim 1 wherein both 20 the collar portion (40, 140) and the neck portion (42, 142) are angularly offset from a straight line joining the two ends of the -decoupler so that as the two ends of the decoupler approach one another, the neck (40, 140) and the

_.collar (42, 142) are each caused to move in a direction

25 away from the straight line so that the two ^'parts become

, completely separated from one another.

4. The steering column decoupler of Claim 1 wherein a shear pin (141) is incorporated between the neck (142) and the collar (140) to provide an initial resistance to

30 relative movement which has to be overcome before decoupling action can begin.

5. The steering column decoupler of Claim 1 wherein the cross section of the collar (40, 140) is formed by folding an initially flat piece of metal to form a non-round cross section, and wherein the neck (42, 142) has a corresponding cross section.

6. The steering column decoupler of Claim 5 wherein the neck (42, 142) is formed by forging.

7. A steering column decoupler as claimed in Claim 2 wherein the packing piece (44, 144) completely surrounds the neck (42, 142) and has contours which ensure that there is no play between the neck and the collar (40, 140).

8. A steering column decoupler as claimed in Claim 1 wherein a forked yoke (28, 34, 128, 134) for attachment to another steering column component through a conventional universal or Cardan joint is provided at each end of the decoupler (10) .