WO2010035127A1

WO2010035127A1 - Mounting assembly

Info

Publication number: WO2010035127A1
Application number: PCT/IB2009/006986
Authority: WO
Inventors: Andrew R. Slayne; Mark Famy; Marcus Baker
Original assignee: Saint-Gobain Performance Plastics Rencol Limited
Priority date: 2008-09-25
Filing date: 2009-09-24
Publication date: 2010-04-01
Also published as: GB0817634D0; TW201026964A

Abstract

A torque resisting assembly is attachable between mating inner and outer components to impede relative rotation therebetween. The torque resisting assembly includes a tolerance ring comprising an annular band of resilient material having a plurality of radially extending projections extending therefrom. The projections are compressed between opposed contact surfaces at least one of which is subsequently attachable to the inner or outer component.

Description

MOUNTING ASSEMBLY

FIELD OF THE DISCLOSURE

The present disclosure generally relates to an apparatus comprising mating inner and outer components, which are mounted together using a tolerance ring to provide an interference fit therebetween. More particularly, the disclosure relates to arrangements in which the tolerance ring provides a controllable slip interface arranged to permit relative rotation between the inner and outer components only above a threshold torque.

BACKGROUND

Mating inner and outer components can be connected together using a tolerance ring. For example, a tolerance ring may be sandwiched between a shaft that is located in a corresponding bore formed in a housing, or it may act as a force limiter to permit torque to be transmitted between the shaft and the housing. The use of a tolerance ring accommodates minor variations in the diameter of the inner and outer components without substantially affecting their interconnection.

Typically, a tolerance ring comprises a band of resilient material, e.g. a metal such as spring steel, the ends of which are brought towards one another to form a ring. A strip of projections extends radially from the ring either outwardly or inwardly towards the centre of the ring. The projections can be formations, possibly regular formations, such as corrugations, ridges, waves or fingers. The band thus comprises an unformed region from which the projections extend, e.g. in a radial direction. There may be two or more rows of projections.

In use, the tolerance ring is located between the components, e.g. in the annular space between the shaft and bore in the housing, such that the projections are compressed between the inner and outer components. Typically, all of the projections extend either outwardly or inwardly so that one of the inner and outer component abuts projections and the other abuts the unformed region. Each projection acts as a spring and exerts a radial force against the components, thereby providing an interference fit between them. Rotation of the inner or outer component will produce similar rotation in the other component as torque is transmitted by the ring. In some arrangements, linear movement of either component will produce similar linear movement in the outer component as linear force is transmitted by the ring.

If forces (rotational or linear) are applied to one or both of the inner and outer components such that the resultant force between the components is above a threshold value, the inner and outer components can move relative to one another, i.e. the tolerance ring permits them to slip. Typically tolerance rings comprise a strip of resilient material that is curved to allow the easy formation of a ring, e.g. by overlapping the ends of the strip.

During assembly of apparatus with an interference fit between components, a tolerance ring is typically held stationary with respect to a first (inner or outer) component whilst a second component is moved into mating engagement with the first component, thereby contacting and compressing the projections of the tolerance ring to provide the interference fit. The amount of force required to assemble the apparatus may depend on the stiffness of the projections and the degree of compression required. Likewise, the load transmitted by the tolerance ring in its final position and hence the amount of retention force provided or torque that can be transmitted may also depend on the size of the compression force and the stiffness and/or configuration of the projections.

One example of the use of a tolerance ring is in steering lock columns. In a conventional arrangement, a tolerance ring is mounted between a steering column shaft (inner component) and a splined locking ring (outer component) which engages a protruding pin on an steering lock mechanism when the steering lock is activated (e.g. when the vehicle engine is off or when the ignition key is removed). The pin is retracted when the steering lock is deactivated (e.g. when the engine is started or when the ignition key inserted).

The function of the tolerance ring is twofold. Firstly, it transmits torque from the steering column shaft to the locking ring so that the pin impedes rotation of the shaft when the steering lock is activated. Secondly it permits slipping (relative rotation) between the shaft and locking ring above a certain threshold torque selected to make normal steering impossible but below a torque (e.g. 100 Nm) that would snap the pin to break the steering lock to permit free steering.

Another automotive application of tolerance rings which permit slip above a threshold torque is power steering, e.g. to protect the mechanism from shock loads i.e. hitting a curb.

SUMMARY In an embodiment, a unit can include a tolerance ring pre-compressed between contact surfaces which are attachable to mating components to impede relative rotation therebetween. By providing such a unit, control of the tolerance ring function can be greatly improved.

The behaviour of tolerance rings as torque resistors, and in particular the tolerance ring function of permitting slip at a contact interface between the tolerance ring and one of the mating components, can depend on properties of both the tolerance ring and the components it contacts. For example, the size and shape of the projections on the tolerance ring can affect the magnitude of the radial force exerted between the components. Tolerance rings may be manufactured to generate radial forces in a given range for a range of radial compressions, e.g. corresponding to the range of annular separations that are possible given the manufacturing tolerances of the mating components. However, variation in other properties of the mating components, e.g. hardness, surface finishing and the like, can also affect tolerance ring performance. Similarly, variations in assembly methods can also affect subsequent tolerance ring performance. Typically these variables are not controlled in the same way as dimension differences and may not be factored into tolerance ring performance assessment. For example, tolerance ring manufacturers typically have little or no control over manufacture of the mating components or methods of assembling the tolerance ring between those components. This can cause uncertainty over whether a tolerance ring will achieve the required performance.

These uncertainties may be overcome by providing a unit, e.g. created under the control of a single manufacturer, in which the tolerance ring is pre-compressed between the contact surfaces which govern its behaviour. The contact surfaces can be attachable to respective mating components by fixing means capable of withstanding the threshold torque. The performance properties of the unit may therefore remain substantially unchanged between manufacture and use.

A torque resisting assembly attachable between mating inner and outer components to impede relative rotation therebetween may be provided. The assembly can comprise a tolerance ring comprising an annular band of resilient material having a plurality of radially extending projections extending therefrom. The projections can be compressed between opposed contact surfaces at least one of which is attachable to the inner or outer component. With this arrangement, the tolerance ring can be pre-compressed, i.e. compressed and in position before the inner and outer components are assembled (mated).

The opposed contact surfaces may be provided on an inner and outer element respectively. At least one of the inner element or outer element can be separate from the inner and outer components. The assembly may resemble a bearing, in which the inner and outer elements correspond to the races and the tolerance ring to the balls. In an embodiment, the unit can have an opposite function to a bearing in that is restricts rather than facilitates rotation.

In one embodiment, the outer element may be the outer component, and the inner element may be a separate component attachable to the inner component. In an alternative embodiment, the inner element may be the inner component, and the outer element may be a separate component attachable to the outer component.

The tolerance ring may comprise a strip of resilient material that is curved into the split ring configuration, i.e. into an annular band. The strip of material may comprise an unformed region from which all the projections extend in the same direction, e.g. either all radially inward or all radially outward. The projections may be press-formed in the strip of material. With this configuration, the unformed surface of the tolerance ring may abut one of the inner and outer elements, and the projections abut the other of the inner and outer elements. Each projection may be a circumferential hump which can extend inwardly or outwardly in the radial direction. Each hump can have a circumferential width within which it rises to and falls from a peak. In a particular embodiment, there may be two or more series of humps, the series being axially spaced from one another.

One of the contact surface may be the inward facing surface of a bore (e.g. formed in the outer element) arranged to receive the tolerance ring. The diameter of the bore may be smaller than the equilibrium diameter of the annular band so that the tolerance ring is retainable in the bore under its own resilience. The tolerance ring may be arranged to provide an interference fit between the inner and outer elements. The opposed contact surfaces may define an annular region having a radial width that is less than the height of the projections.

In one embodiment, the relative position of the opposed contact surface may be unchanged when the assembly is mounted on the inner or outer component. An advantage of this is that compression of the tolerance ring projections may be substantially the same before and after attachment of the assembly to the inner and/or outer component. Preferably, there can be substantially no or at least minimal change in the factors which affect the performance of the tolerance ring as a torque resisting device.

As mentioned above, at least one of the opposed contact surfaces can be attachable to the inner or outer component. The apparatus may comprise an attachment element arranged to fix the angular position of the assembly to one or both of the inner and outer components, i.e. to prevent slipping between the opposed contact surfaces and the inner and outer components. Preferably, the attachment element can have a higher torque transfer limit than the tolerance ring. This ensures that slipping can happen first at an interface between the tolerance ring and either the inner contact surface or the outer contact surface.

The attachment element may be any conventional arrangement suitable for providing the necessary torque transfer. For example, it may be a splined connection between the inner or outer component and the inner or outer element respectively. Alternatively the attachment element may interlock with one or both of the inner and outer components, e.g. by means of a protruding key (provided on one of the assembly or the inner and/or outer component) and a corresponding slot (provided on the other of the assembly or the inner and/or outer component). Preferably, the attachment element can be a mechanical fixing, but may be achieved by welding or other bonding techniques.

Providing the assembly of the invention as a unit can give the manufacturer more control over three major factors which influence tolerance ring performance.

Firstly, variation in the dimensions of components (e.g. inner of outer surface diameter, wall thickness, etc.) can affect the compression of the tolerance ring projections which directly relates to the level of torque resistance (i.e. the level of torque required to cause slip). Greater control of the compression force can permit greater control of the torque resistance.

Secondly, properties of the materials which contact the tolerance ring, e.g. the inner and outer components in conventional arrangements, and in particular their respective hardness relative to the hardness of the material of the ring, may affect the location of the slip interface, i.e. which contact surface the tolerance ring will slip against. Similarly, surface treatments may affect the friction experienced by the tolerance ring. Greater control of the properties of the contact surfaces can permit greater control of the torque resistance.

Thirdly, variations in the assembly method of a tolerance ring in conventional arrangements may affect the compression of the projections and in certain circumstances can even damage the ring. Providing the unit with a pre-compressed tolerance ring can provide greater control of those variations and can remove or minimize the risk of damage.

In a particular aspect, one of the contact surfaces may be provided by a clamp element arranged to grip the inner or outer component. The clamp element may be the attachment element discussed above, i.e. the grip function may serve to prevent relative rotation between the clamp element and the component it grips. The clamp element may be a one piece resilient split clip (e.g. similar to a circlip) arranged to grip onto the outward facing surface of an inner component or to be retained (gripped) within the inward facing surface of an outer component. The inner or outer surface of the clamp element may provide one of the opposed contact surfaces.

One advantage of the torque resisting assembly of the invention is that the same device may be attachable to inner and outer components having a wide range of different shapes, e.g. by using suitable adaptors. For example, the assembly may be mountable on a shaft (inner component) having a non-circular cross-section, e.g. by introducing an adaptor between the outer surface of the shaft and the inner surface of the assembly. The adaptor may be have an outward facing surface arranged to match the inner surface of the assembly. The inner surface of the assembly may itself be non-circular, e.g. polygonal (hexagonal or octagonal) to provide the attaching function mentioned above. Indeed, the adaptor may be optional; the shape of the inner surface of the assembly may be matched with the shape of the outer surface of the shaft. The same considerations apply mutatis mutandis to arrangements where the outer surface of the assembly is attached to the outer component.

In another aspect, a torque resisting apparatus can include a torque resisting assembly attached between mating inner and outer components to impede relative rotation therebetween. The apparatus may be suitable for use in steering columns. For example, the inner component may be a shaft and the outer component a lock collar for engaging a fixed locking pin, wherein the apparatus permit relative rotation of the inner and outer components above a threshold torque of 100 Nm but below the torque required to snap the pin. In another aspect, a method of assembling torque resisting apparatus can include attaching a torque resisting assembly having a pre-compressed tolerance ring between an inner or an outer component.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.

Fig. 1 is a cross-sectional side view of a torque resisting assembly according to an aspect;

Fig. 2 is a cross-sectional top view of the torque resisting assembly shown in Fig. 1 taken along the line 2-2;

Fig. 3 is a top view of a torque resisting assembly according to another aspect; and

Fig. 4 is a torque resisting apparatus according to an aspect.

The use of the same reference symbols in different drawings indicates similar or identical items.

DETAILED DESCRIPTION Fig. 1 shows a torque resisting assembly 10 comprising an inner element 12, an outer element

14, and a tolerance ring 16 sandwiched therebetween. The inner element 12 can be a tubular member having an outward facing contact surface 20 for abutting the tolerance ring 16. The outer element 14 can be a lock collar having a bore therethrough which receives the inner element 12 therein. The bore can have an inward facing contact surface 18 which opposes the outward facing surface 20 of the inner element 12 to define an annular gap between the elements in which the tolerance ring 16 is received. In this embodiment, the outer element 14 can have outward extending projections 22 at one end.

The tolerance ring 16 can comprise an annular band of resilient material having two rows of radially outward extending projections 17, which are located between annular unformed regions 19. In the embodiment, the axial edges of the tolerance ring 16 are flared outwards to facilitate assembly. This is an optional feature, in other embodiments the axial edge strips of the tolerance ring 16 may be unformed regions parallel with the outward facing surface 20.

The annular gap between the inner and outer elements 12, 14 can be smaller than (can have a smaller radial extent than) the radial distance that the projections 17 extend away from the unformed regions 19. When the tolerance ring 16 is sandwiched between the inner and outer elements 12, 14 the projections can be compressed. The reaction force to the compression can be sufficient to retain the inner element 12, outer element 14 and tolerance ring together as a unit. The projections 17 can abut the inward facing contact surface 18 of the outer element 14 and the unformed regions 19 can abut the outward facing surface 20 of the inner element 12. When torque is experienced between the inner and outer elements 12, 14 relative rotation can be resisted by friction at the contact points between the tolerance ring 16 and the inner and outer elements 12, 14 unless the torque exceeds a threshold level. The magnitude of the frictional force can be related to the magnitude of the radial retention force exerted by the tolerance ring 16.

In this embodiment, the inner element 12 can have an attachment element 21 for attaching the inner element in a non-rotatable fashion to an inner component of an apparatus in which the torque resisting assembly is to be mounted. In this embodiment, the attachment element 21 can be a protruding key to be received in a corresponding slot in the inner component. Other attachment methods are possible so long as they are strong enough to withstand torques beyond the threshold level.

In this embodiment, the outer element can be combined with an outer component of the apparatus in which the torque resisting assembly is to be mounted. In an alternative embodiment, the outer element may be a plain sleeve having an attachment element for attaching in a non-rotating manner to an outer component comprising a ring having the splines 22.

Fig. 2 shows a top view of the assembly shown in Fig. 1. The same reference numbers are used for common components. Since the tolerance ring 16 is a split ring, its axial gap 23 is visible in this drawing. Fig. 2 also shows that in this embodiment the inner element 12 can be an unbroken tube having a circular cross-section. However, whilst the outward facing surface 20 can preferably have a circular cross-section for permitting even abutment with the tolerance ring, the inner surface 25 of the inner element 12 may be non-circular. For example, if the inner component to which the inner element is to be attached itself has a non-circular cross-section, the inner surface of the inner element may have a matching cross-sectional shape. In some embodiments the mating of parts with non-circular cross- sections in this way may achieve the non-rotatable attachment can function without an attachment element. In other embodiments, an adaptor (not shown) may be attached on the inside surface of the inner element, e.g. to retro-fit (i.e. match its shape after manufacture) to the inner component.

Fig. 3 shows the top view of another embodiment of a torque resisting assembly 30. This embodiment is similar to that shown in Fig. 2 except that the inner element 32 in this case can have a split ring configuration, e.g. can be formed from a strip of resilient material wound into an annular band. The axial split 34 is visible in Fig. 3. In this embodiment, the inner element 32 can be arranged to grip the inner component, e.g. by providing the inner element with an inner diameter smaller than the outer diameter of the inner component. The diameter of the outward facing contact surface 36 can be arranged to be large enough to create an annular gap between the outward facing contact surface 36 and the inward facing contact surface of the outer element. The annular gap can be small enough to retain the tolerance ring when the inner element is in its unmounted state. Preferably, the change in shape (in particular the change in outer diameter) of the inner component between its unmounted state and its mounted state is kept to a minimum. Fig. 4 shows a torque resisting apparatus 100 that is an embodiment of the invention. The apparatus 100 may be suitable for use in a steering column. The apparatus 100 can include an inner component (shaft) 102 and a lock mechanism 104 having a retractable pin 106 that is insertable between splines 22 of an outer component. The torque resisting assembly e.g. as shown in Fig. 1 can be mounted on the shaft 102 through non-rotatable attachment of the inner element 12 to the shaft 102. In this embodiment, the outer element and the outer component can be formed in one piece; in other embodiments the outer element may be mounted on a separate outer component though a non-rotatable attachment.

The shaft 102 can be a tubular piece of material received in a bore formed through the inner element 12. As mentioned above, the internal cross-section shape of bore may be matched with the outer cross-section shape of the shaft 102, e.g. using an adaptor.

In this embodiment, the tolerance ring can already be compressed between the contact surfaces 18, 20 when it is mounted on the inner component. Since the behaviour of the tolerance ring, in particular the torque range at which slipping will occur, is governed by the size of the compression force it experiences and the properties of the surfaces it contacts, using the assembly provides greater control over the behaviour of the apparatus when compared with an apparatus in which the tolerance ring is mounted directly between the shaft 102 and the outer element 14.

Claims

WHAT IS CLAIMED IS:

1. A torque resisting assembly attachable between mating inner and outer components to impede relative rotation therebetween, the assembly comprising a tolerance ring comprising an annular band of resilient material having a plurality of radially extending projections extending therefrom, which projections are compressed between opposed contact surfaces at least one of which is subsequently attachable to the inner or outer component.

2. An assembly according to claim 1 comprising mating inner and outer elements which provide the opposed contact surfaces.

3. An assembly according to claim 2, wherein the outer element is the outer component, and the inner element is a separate component attachable to the inner component.

4. An assembly according to any preceding claim, wherein the tolerance ring comprises a strip of resilient material that is curved into an annular band comprising an unformed region from which all the projections extend in the same direction, the unformed surface of the tolerance ring abutting one of opposed contact surfaces, and the projections abutting the other of opposed contact surfaces.

5. An assembly according to claim 2, wherein the compression of the tolerance ring between the inner and outer elements retains inner element, outer element and tolerance together as a single unit for attachment to an inner or outer component.

6. An assembly according to claim 5, wherein the opposed contact surfaces define an annular region having a radial width that is less than the height of the projections.

7. An assembly according to any preceding claim comprising an attachment element arranged to fix the angular position of the assembly to one or both of the inner and outer components.

8. An assembly according to any preceding claim, wherein one of the contact surfaces may be provided by a clamp element arranged to grip the inner or outer component.

9. An assembly according to claim 8, wherein the clamp element comprises a one piece resilient split clip arranged to grip onto the outward facing surface of an inner component or to be retained within the inward facing surface of an outer component.

10. An assembly according to claim 2, wherein the inner element has a mounting interface adapted to fit against an outer surface of inner component.

11. An assembly according to claim 10, wherein the mounting interface comprises a bore for receiving the inner component, the inner surface of the bore having a cross-section shape that matches the cross-sectional shape of the outer surface of the inner component.

12. Torque resisting apparatus comprising a torque resisting assembly according to any preceding claim mounted between mating inner and outer components to impede relative rotation therebetween.

13. Apparatus according to claim 12, wherein the torque resisting assembly comprises an inner element and an outer element, at least one of which is separate from the inner component and the outer component respectively.

14. Apparatus according to claim 12 or 13, wherein the relative position of the opposed contact surfaces is unchanged when the assembly is mounted on the inner or outer component.

15. A method of assembling torque resisting apparatus, comprising attaching a torque resisting assembly having a pre-compressed tolerance ring between an inner or an outer component.

16. A method according to claim 15, wherein the torque resisting assembly is a torque resisting assembly according to any one of claims 1 to 11.