GB2587332A - A steering column assembly - Google Patents

Abstract

Provided is a steering column assembly 100 comprising a shroud 102 that supports a steering shaft 104; a support bracket assembly; a clamp pin 112; and a clamp 130. The support bracket assembly, which is to be secured to the vehicle, has two arms 110a, 110b that extend from a base 130 to embrace the shroud 102; and the clamp pin 112 extends through an opening 114 in each arm 110a, 110b and a slot 116 in the shroud 102. In use, the clamp 130 secures the shroud 102 to the two arms of the bracket 108 such that the rake cannot be adjusted. The support bracket assembly comprises mounting 109 and support 108 brackets, and a frangible connector with an associated capsule plate. The frangible connector has a planar base plate that carries a frangible portion that prevents sliding between the connector and a portion of the mounting plate; and a frangible portion that prevents sliding between a portion of the rake bracket and the connector.

Description

A STEERING COLUMN ASSEMBLY

The present invention relates to improvements in steering column assemblies. More particularly, the invention relates to steering column assemblies including a frictional clamping system.

It is known to provide a collapsible steering column assembly comprising a steering shaft that is supported within a steering column shroud. To prevent significant injury to the driver in the event of a crash the steering column should be able to collapse as an axial load is applied through the steering wheel, for instance in a front impact where an unrestrained driver is thrown onto the steering wheel.

A typical collapsible steering column assembly comprises a telescopic shroud, having an outer shroud portion and an inner shroud portion, an end of the inner shroud portion extending into the outer shroud portion. The outer shroud portion may be located closer to the steering wheel, or further from the steering wheel than the inner shroud portion. A telescopic steering shaft, also having an upper and lower shaft part, is supported inside the shroud through one or more bearing assemblies. The steering wheel is fixed to the upper shaft portion. In some cases, the shroud will not include two portions and instead the shroud will simply move relative to the bracket.

The part of the shroud closest to the wheel must be able to move, or collapse, during a crash so as to allow the steering wheel to move forwards relative to the vehicle body but be prevented from moving during normal use. There is also a need to fix the shroud relative to the vehicle body to define the rake position of the steering wheel.

This is typically achieved by a clamp mechanism that secures the shroud to a support bracket that is in turn fixed to the vehicle body, perhaps to a cross beam provided behind the dashboard of the vehicle. The clamp mechanism may be adjustable to permit reach adjustment, or rake adjustment, or both, of the steering wheel. In the event of a crash the shroud must be able to move, and this is achieved if it is able to break free of the clamp mechanism, or for the support bracket to be able to break free of the vehicle body, to allow the steering column assembly to collapse telescopically.

A lever may be provided on an end of the a clamp bolt that forms a part of the clamp mechanism that the driver can push or pull to rotate the clamp bolt and thereby operate the clamp mechanism.

Steering column assemblies are known which include a damp mechanism that relies solely on friction when locked to prevent unwanted movement of the column assembly. The clamp mechanism can be unlocked and locked by movement of a locking lever or, sometimes, electrically using a motor or perhaps hydraulically or pneumatically. These columns can typically resist radial and/or axial forces of 600N applied at the steering wheel before slipping. These radial and axial forces largely pass through the support bracket and into the vehicle body.

However, it is increasingly a requirement from car manufacturers that there should be no substantial movement of the steering column assembly when forces of up to 5000N are applied. The objective is to prevent unwanted movements of the steering wheel in a crash so that the deployment of the air bag is ideally controlled. if the bracket is insufficiently rigid it may twist or otherwise deform allowing the shroud to move. To date, this has been prevented using brackets with relatively massive arms to ensure that the arms do not bend or otherwise flex under load According to a first aspect, there is provided a steering column assembly for a vehicle, the steering column assembly comprising: a shroud; a steering shaft. which is supported by the shroud; a support bracket assembly configured to be secured to a fixed part of the vehicle and including two arms that depend from a base portion to embrace the shroud; a clamp pin that extends through an opening in each of the arms of the support bracket and a slot in the shroud; and a clamp mechanism that is movable between an undamped position in which the shroud can be adjusted for rake relative to the support bracket and a clamped position in which the shroud is fixed relative to the support bracket; and whereby the clamp mechanism in use secures the shroud to the two arms of the bracket; characterised in that the support bracket assembly comprises: a mounting bracket; a support bracket; at least one frangible connector that comprises a planar base plate carrying at least one frangible portion that prevents relative sliding movement between the frangible connector and a portion of the mounting bracket and at least one frangible portion that prevent sliding movement between a portion of the rake bracket and the frangible connector thereby providing a load path between the two brackets through the frangible connector; and a capsule plate associated with the at least one frangible connector in which the base plate of the frangible connector and the portion of the rake bracket are clamped between the capsule plate and the mounting bracket, and at least one fastener which passes through complimentary shaped openings in the mounting bracket and the capsule plates and is placed in tension to squeeze the base plate and the rake bracket in between the clamp plate and the mounting bracket.

Providing a frangible connector having a planar body sandwiched between the mounting bracket and rake bracket that is placed in compression by at least one fastener ensures that there is minimal to zero free play between the brackets. The use of a rivet makes this easy to assure during assembly by appropriate selection of the force required to install the rivet.

The fastener may comprise a screw or bolt and may most preferably comprise a rivet.

The assembly preferably comprises two frangible connectors, and capsule plate for each frangible connector, each frangible connector sandwiched with a respective part of the rake bracket between the mounting bracket and a respective clamp plate.

The portions of each of brackets that are sandwiched together may comprise planar wings which extends away from a central body of the brackets.

Each bracket may comprise two wings, one each side of the central portion, each associated with a respective frangible connector that provides a load path between a pair of wings.

The base plate of the frangible connector may be generally planar and may define a sliding surface over which a facing surface of the mounting bracket will slide in the event of a crash.

The base plate may have a shape that complements the shape of the wings. For instance each wing may be rectangular and the outline of the thin plate may align with the outline of the respective wing. The base plate may be relatively large in both width and height by which we mean it has a width and height of at least 5 cm. Providing a large plate gives a good connection between the two brackets over a correspondingly large area which enhances the stiffness of the assembly but will have a higher friction during a crash than a smaller plate.

The connector may be a plastic component. The base plate and pins may be formed as one moulded component.

The frangible connector may include a raised lip that extends around an opening, the lip fitting into a complimentary open sided U-shaped cut-out in the rake to locate the frangible connector relative to the wing. The cut out may be complimentary to the shape of the raised portion apart from the open end of the U-shape which allows the rake bracket to slide clear of the raised portion during a crash through the open end.

The mounting bracket may include a raised portion that is bumped out of the plane of the mounting bracket where the mounting bracket engages the frangible connector base plate, the raised portion projecting into the opening in the frangible connector and through an opening in the capsule plate to locate the capsule plate such that it cannot move side to side relative to the mounting bracket. The raised portion may comprise a central cap that is bumped out by a cylindrical lip, the cap fitting snugly within a corresponding hole in the capsule plate. The raised portion helps to take the load off the rivet during normal use of the steering by transferring loads caused by any small side to movement of the two brackets relative to one another through the body rather than the load being taken by the rivet. The rivet in this case will primarily act to press the sandwiched parts together rather than resisting any shearing of the parts.

The raised cap may be circular. A smaller hole may be provided in the raised cap for receiving a mounting bolt to secure the mounting bracket to a fixed part of the vehicle.

The mounting bolt may pass through the openings in the capsule plate, rake bracket, frangible connector and mounting bracket such that in the event of a crash the rake bracket can move relative to the support bracket by shearing of the frangible pins without striking the mounting bolts.

Where the fastener is a rivet it may comprise a tubular rivet and the amount of compression applied to the sandwich of components may be determined by appropriate selection of the rivet, in particular the tensile strength of the rivet head.

The base plate of the connector element may be resilient so that it compresses under load from the rivet, taking up any free play that may otherwise exist in the components. It may, for example, include one or more crushable ribs on one side or both sides of the plate that engage a respective bracket, the ribs deforming during assembly as the rivet is applied. Preferably the plate is more resilient than the portions of the brackets it is sandwiched between so that the plate deforms rather than the bracket portions.

According to a second aspect the invention provides support bracket assembly for supporting a steering column shroud, the support bracket assembly comprising: a mounting bracket for securing to a fixed part of a vehicle; a support bracket; at least one frangible connector; and a capsule plate associated with the at least one frangible connector; in which the frangible connector comprises a planar base plate carrying at least one frangible pin that prevents relative sliding movement between the frangible connector and a portion of the mounting bracket and at least one further frangible pin that prevent sliding movement between a portion of the rake bracket and the frangible connector; in which the base plate of the frangible connector and the portion of the rake bracket are clamped between the capsule plate and the mounting bracket by at least one fastener placed in tension which passes through complimentary shaped openings in the mounting bracket and the capsule plates to clamp the base plate and the rake bracket in between the clamp plate and the mounting bracket.

There will now be described by way of example only one embodiment of the present invention with reference to and as illustrated in the accompanying drawings of which Figure 1 is a cross section view of an embodiment of a steering column assembly in accordance with the first aspect looking along a length of the steering shaft of the assembly; Figure 2 is a side view of the assembly.' of Figure 1 with the shroud in a mid-height rake position; Figure 3 is perspective view of the support bracket assembly with the shroud removed for clarity; Figure 4 is an exploded view corresponding to the view of Figure 3; Figure 5 is an exploded view from an opposite angle of the support brackct assembly shown in Figure 3; Figure 6 is an enlarged partial sectional view of the support bracket assembly along the vertical plane A-A in Figure 3; Figure 7 (a) and (b) arc alternate views of the mounting bracket; Figure 8(a) and (b) arc alternate views of the frangible connector; Figure 9 is an enlarged sectional view of the support bracket assembly along the vertical plane B-B in Figure 3 Figure 10 is a view of the capsule plate; Figure II is a view of the rivet prior to installation; and Figure 12 is an enlarged section view of the support bracket assembly along the vertical plane.C-C in Figure 3.

Referring firstly to Figure 1, there is shown a steering column assembly 100 comprising a shroud 102 that houses a shaft 104. The shaft 104 is configured to be attached to a steering wheel (not shown). The shaft 104 is supported by a bearing assembly (not shown) that allows rotation of the shaft 104 relative to the shroud 102. The shroud is fixed pivotally at one end and supported along its length by a support bracket assembly.

The support bracket assembly 108 is shown in more detail in Figures 2 to 12, and comprises a mounting bracket 109, a rake bracket 200, a pair of clamp plates 300, a pair of capsule elements 400 and two rivets 500.

The mounting bracket 109 is shown clearly in Figures 7(a) and 7(b). The mounting bracket 109 comprises a base portion 130 that is generally planar and extends across the top of the shroud 102. Each end of the base portion 130 projects outwards to define a wing 132,134 portion. The wings defined outboard fixing points for securing the bracket to the body of the vehicle. In the example shown bolts (not shown) may pass through holes 136,138 in the wings. The mounting bracket, when secured with the mounting bolts to a fixed part of the vehicle, cannot move even when a crash force is applied to collapse the steering column assembly.

The rake bracket 200 is clearly shown in Figure 4 and 5 of the drawings. it comprises a base portion that is complimentary to the base portion 130 of the mounting plate, and includes a base portion and two ends of the base portion projects outwards to define a wing 210,220 portion. Each wing overlays a wing of the mounting plate, spaced apart therefore by one of the capsule elements as will be explained below. The rake bracket also includes two arms 110a and 110b that depend in a substantially vertical direction and provide support and stability to the shroud 102, in use these arms extend down opposite sides of the steering column shroud as shown in Figures 1 and 2. Slots in the arms accommodate a clamp pin, allowing the clamp pin to move up and down the slots for rake adjustment of the shroud.

Sandwiched between the wings of the rake bracket and the respective wings of the mounting plate 109 are the pair of capsule elements. These are shown clearly in Figures 8(a) and 8(b). Each capsule element comprises a planar base plate that determines the spacing between the wings, the plate having four frangible pins that extend away from the base, two on each side. One pair engages small holes formed in the wing of the mounting plate and the other pair engages small holes in the wing of the rake bracket and pass into holes formed in a clamp plate as will be explained below. The width of the plate may be selected as a function of the diameter of the bolts that will pass through the plate to fix the brackets to the vehicle body, with extra width resulting in an increase in the ride-down friction and stiffness, so a balance needed. The whole capsule element is constructed from a frangible material such as plastic allowing the pins to shear when sufficient side load is applied. The base plate is resilient and also includes a number of ridges on the side facing the mounting plate which can deform slightly as the capsule plate is compressed between the mounting plate and rake bracket taking up tolerances and ensuring there is no free play. The other side of the base plate that contacts the wing of the rake bracket is both flat and highly polished to define a sliding surface with a complimentary flat and smooth part of the wing of the rake bracket.

The clamp plate 300 is best seen in Figure 10. It comprises a rectangular plate with a central hole 310. A raised annular lip of the mounting plate projects through a correspondingly open sided shaped opening in the rake bracket and a corresponding close sided opening in the capsule element far enough to also project into the central hole, the lip being a snug fit as so as to locate the clamp plate 300. The stem of the mounting bolt passes through the aligned holes.

The capsule plate, rake bracket wing, capsule element and mounting plate wing are clamped together in that order by a rivet in this example. In alternatives one or more screws or small bolts may be used instead of rivets to give fine control of the clanp force. Figure 11 shows a suitable rivet 500 and rivet stem 510 prior to use. The rivet shown is of the type known as a blind rivet, with a mandrel that passes through a tube, allowing it to be placed in position and then the mandrel pulled through to upset the end of the tube. This action also cause the rivet to compress the components together and the amount of compression can be pre-set by selection of an appropriate rivet.

Each rivet passes through three aligned openings 220,320,420 in the clamp plate, the capsule plate and the mounting plate respectively but does not pass through a similar hole the rake bracket wing. Instead the rivet passes through the much larger open ended opening in the rake bracket that accommodates the mounting bolt. This can best be seen in Figure 12. The rivet prevents any side to side movement between the clamp plate, capsule plate and mounting plate. It does not prevent any side to side movement of the rake bracket. The rake bracket is only prevented from moving side to side by the engagement of the frangible pins into the mounting plate and clamp plate.

A clamp pin 112 passes through vertical slots 114 in the rake bracket 200 and a horizontal slot 116 in a clamp rail 118 of the shroud 102. The clamp pin 112 has a stop 120 at one end that prevents the clamp pin 112 being drawn through the support bracket 108. At the other end, a cam mechanism 122 that is rotated by use of a lever 124 enables an effective length of the clamp pin 112, i.e. the length of the clamp pin 112 between the cam mechanism 122 and the stop 120, to be varied. The cam mechanism 122 comprises a fixed cam part 126 and a moving cam part 128, the moving cam part 128 being rotated by the rotation of the lever 124, pushing against the fixed cam part 126 and extending the length of the cam mechanism 122. The clamp pin and the cam and end stops together with the bracket arms and rail define a clamp mechanism.

In the undamped position of the clamp mechanism 130, there is sufficient freedom of movement of the arms to allow adjustment of the reach and rake position of the steering column assembly 100 without undue exertion from a user. The clamping mechanism 130 is shown in the clamped position in all of the accompanying Figures.

To move from the undamped to the clamped condition the user rotates the level 124. Rotation of the lever 124 leads to extension of the cam mechanism 122 along the clamp pin 112 and thus the cam mechanism 122 extends through the slot 114 in the support bracket 108 and presses on the outside of one of the arms 110a. This arm is pressed into contact with the shroud 102. The shroud 102 is thus pushed over towards the right side of the support bracket 108 and presses the other arm 110b onto the end stop 120 on the damp pin thus locking the shroud 102 in a desired position relative to the support bracket 108.

In normal use the rake bracket is prevented from movement by the frangible pins of the capsule plate locking it to the mounting plate. if a crash occurs the places a high axial load onto the shroud, this is transferred through the clamp pin onto the arms of the rake bracket, which causes the rake bracket to shear the frangible pins. The rake bracket can then slide relative to the mounting plate

Claims (9)

1. CLAIMS1. A steering column assembly for a vehicle, the steering column assembly cornprising: a shroud; a steering shaft, which is supported by the shroud; a support bracket assembly configured to be secured to a fixed part of the vehicle and including two arms that depend from a base portion to embrace the shroud; a clamp pin that extends through an opening in each of the arms of the support bracket and a slot in the shroud; and a clamp mechanism that is movable between an unclamped position in which the shroud can be adjusted for rake relative to the support bracket and a clamped position in which the shroud is fixed relative to the support bracket; and whereby the clamp mechanism in use secures the shroud to the two arms of the bracket; characterised in that the support bracket assembly comprises: a mounting bracket; a support bracket; at least one frangible connector that comprises a planar base plate carrying at least one frangible portion that prevents relative sliding movement between the frangible connector and a portion of the mounting bracket and at least one frangible portion that prevent sliding movement between a portion of the rake bracket and the frangible connector thereby providing a load path between the two brackets through the frangible connector; and a capsule plate associated with the at least one frangible connector; in which the base plate of the frangible connector and the portion of the rake bracket are clamped between the capsule plate and the mounting bracket, and at least one fastener placed in tension which passes through complimentary shaped openings in the mounting bracket and the capsule plates to squeeze the base plate and the rake bracket in between the clamp plate and the mounting bracket.
2. 2. A steering column assembly according to claim 1 which comprises two frangible connectors, and a respective capsule plate associated each frangible connector, each frangible connector sandwiched with a respective part of the rake bracket between the mounting bracket and a respective capsule plate.
3. 3. A steering column assembly according to claim 2 in which the portions of each of the brackets that are sandwiched together comprise planar wings which extend away from a central body of the brackets.
4. 4. A steering column assembly according to any preceding claim in which the base plate of the frangible connector is generally planar and defines a sliding surface over which a facing surface of the moimting bracket will slide in the event of a crash.
5. 5. A steering column assembly according to any preceding claim in which the frangible connector includes a raised lip portion around an opening which fits into a complimentary open sided U-shaped cut-out in the rake bracket to locate the frangible connector relative to the wing.
6. 6. A steering column assembly according any preceding claim in which the mounting bracket includes a raised portion that is bumped out of the plane of the mounting bracket where the mounting bracket engages the frangible connector base plate, the raised portion projecting though an opening in the frangible connector and into a complimentary shaped opening in the capsule plate to locate the capsule plate such that it cannot move side to side relative to the mounting bracket.
7. 7. A steering column assembly according to any preceding claim in which the base plate of the connector element is resilient so that it compresses under load from the rivet, taking up any free play that may otherwise exist between the two brackets.
8. 8. A steering column assembly according to any preceding claim in which the fastener comprises a rivet.
9. 9. A support bracket assembly for supporting a steering column shroud, the support bracket assembly comprising: a mounting bracket for securing to a fixed part of a vehicle; a support bracket; at least one frangible connector; and a capsule plate associated with the at least one frangible connector; in which the frangible connector comprises a planar base plate carrying at least one frangible pin that prevents relative sliding movement between the frangible connector and a portion of the mounting bracket and at least one further frangible pin that prevent sliding movement between a portion of the rake bracket and the frangible connector; in which the base plate of the frangible connector and the portion of the rake bracket are clamped between the capsule plate and the mounting bracket by at least one fastener placed in tension which passes through complimentary shaped openings in the mounting bracket and the capsule plates to clamp the base plate and the rake bracket in between the clamp plate and the mounting bracket.