GB2579422A - A steering column assembly - Google Patents

Abstract

A steering column assembly has a mounting bracket 102 securable to a fixed part of a vehicle and a support bracket 104 to which a shaft 108 is secured, directly or indirectly. The assembly is configured to collapse under predetermined conditions, where support bracket 104 moves relative to mounting bracket 102 in a longitudinal direction of support bracket 104. The assembly also has a retaining mechanism 112 which prevents steering column collapse when support bracket 104 is subjected to only a substantially axial force along a longitudinal axis of shaft 108 and allows steering column collapse when support bracket 104 is subjected to both an axial force and a torque in a vertical plane containing the longitudinal axis of shaft 108, for example when both are above thresholds.

Description

A STEERING COLUMN ASSEMBLY

The present invention relates to a steering column assembly, specifically those that can collapse in a controlled manner in the event of a crash by controlled breakaway of a portion of the steering column assembly from a mounting bracket that secures it to the main body of a vehicle.

It is known to provide a steering column assembly comprising a shroud that houses a steering shaft. The steering shaft connects a steering wheel to the road wheels of the vehicle allowing the driver to rotate the steering wheel in turn to move the road wheels. The connection may be through a rack and pinion gearbox, and to assist the driver a hydraulic or electric assistance may be provided. In the case of electric assistance a motor will act upon the steering shaft or a part of the steering between the shaft and the road wheels to apply a torque in the same sense as that applied by the driver.

The shroud may be non-adjustable in a simple arrangement in which it is fixed via a support bracket to a mounting bracket that is secured to the vehicle body, for instance to a beam that extends across the vehicle behind the dashboard. In other cases it may be adjustable for rake or reach or both rake and reach. This may be achieved by connecting the shroud to the support bracket though an adjustable damp mechanism, the support bracket in turn being fixed to the mounting bracket. During adjustment the clamp assembly is released and the shroud can be moved up or down, or along, the support bracket.

Although the steering column assembly must normally be fixed in position relative to the vehicle, in all of these cases, it can be beneficial to allow the shroud and support bracket to break away from the mounting bracket during a crash. Movement of the support bracket relative to the mounting bracket allows energy to be absorbed during a crash, which can help to prevent or limit injuries to a driver of the vehicle.

In many cases, the mechanism that allows the support bracket to break away from the mounting bracket can be damaged by abuse of the steering column assembly. For example, during reach and rake adjustment the forces involved can damage the mechanism that allows break away, resulting in non-optimal behavior during a subsequent impact and collapse. It has also been noted that discharge of an airbag within the steering wheel can apply forces to the steering column assembly that damage the breakaway mechanism, also impacting on the collapse characteristics of the steering column assembly. This effect may be magnified in steering column assemblies configured to collapse under a relatively low force.

According to a first aspect, there is provided a steering column assembly, comprising: a mounting bracket configured to be secured to a fixed part of a vehicle; a support bracket; and a shaft secured, directly or indirectly, to the support bracket; wherein the steering column assembly is configured to collapse under predetennined conditions, whereupon the support bracket is enabled to move relative to the mounting bracket in a longitudinal direction of the support bracket; the steering column assembly further comprising: a retaining mechanism configured to prevent initiation of steering column collapse when the support bracket is subjected to only a substantially axial force along a longitudinal axis of the shaft and to allow initiation of steering column collapse when the support bracket is subjected to both an axial force and a torque in a vertical plane containing the longitudinal axis of the shaft.

By requiring both an axial force and a torque in the vertical plane in order to initiate collapse, accidental initiation due to collapse, airbag deployment, or abuse during adjustment can be prevented or limited. Purely axial forces, such as airbag deployment or steering reach adjustment will be prevented from initiating collapse by the retaining mechanism. This will also be the case in the event of a pure torque, which could be applied during steering rake adjustment or accidentally by a driver in other situations, such as when entering or exiting the vehicle. Thus, the steering column assembly will be protected or substantially protected from collapse in situations other than those in which collapse is desirable.

The torque may cause the support bracket to rotate, twist, or bend relative to the mounting bracket. More specifically, a front portion of the support bracket may rotate, twist, or bend upwards relative to the mounting bracket.

The rotation, twisting, or bending may act about a horizontal axis of the support bracket. The horizontal axis may be defined by a portion of the retaining mechanism. The portion of the retaining mechanism defining the horizontal axis may be a wing, runner, or horizontal protrusion of the support bracket.

The retaining mechanism may be configured to allow initiation of steering column collapse when the axial force and the torque are above respective thresholds.

By implementing thresholds, the level of force and torque required to initiate collapse can be controlled. The thresholds may be predetermined. They may be chosen to be equal to the forces and torques experienced in a particular type of impact. The thresholds may be chosen to be above the maximum typical force experienced during rake-and reach-adjustment of the steering column assembly.

The retaining mechanism may have an engaged position and a disengaged position whereby, in the engaged position, the retaining mechanism is configured to prevent initiation of steering column collapse and, in the disengaged position, the support bracket is configured to enable initiation of steering column collapse.

The retaining mechanism may be biased into the engaged position and may be configured to move from the engaged position to the disengaged position upon application of the torque in the vertical plane.

By biasing the retaining mechanism into the engaged position, any torque applied will only temporarily place the retaining mechanism into the disengaged position, unless it is accompanied by an axial force sufficient to initiate collapse. The retaining mechanism will then return to the engaged position once the torque is removed, further preventing initiation of collapse and effectively resetting the assembly.

The retaining mechanism may include a biasing mechanism configured to bias the retaining mechanism into the engaged position.

The biasing mechanism may include a retaining spring.

The retaining mechanism may be moved to the disengaged position by the torque.

The retaining mechanism may be moved to the disengaged position by bending of the support bracket.

The support bracket may bend relative to the mounting bracket, for example when a torque is applied, which can then put the retaining mechanism in the disengaged position.

The retaining mechanism may include a latch engageable with an abutment or obstruction.

The abutment may be formed by a notch or recess. For example, the abutment may be a wall of the notch or recess.

The use of a combination of a latch and abutment can provide a positive-lock for the retaining mechanism, which prevents accidental movement of the support bracket relative to the mounting bracket.

The latch may be configured to disengage from the abutment upon application of the torque in the vertical plane.

The abutment may be aligned perpendicular to a direction of travel of the support bracket during steering column collapse.

By aligning the abutment perpendicularly, axial forces may be prevented from forcing the retaining mechanism into the disengaged position.

The abutment may be aligned at an angle to a direction of travel of the support bracket during steering column collapse.

By aligning the abutment at an angle, the torque may additional provide a force to move the column axially. In this way, it may be possible to require a larger axial force to cause collapse of the steering column assembly, preventing accidental collapse through abuse, whilst a combined axial force with a torque will collapse the steering column due to the torque being transformed into an additional axial force.

The retaining mechanism may include a fastener that prevents initiation of steering column collapse when the axial force is below a threshold axial force.

The use of a fastener may provide an easily tunable component that can allow the steering column assembly to collapse only when an axial force above a threshold is applied. The tuning of the fastener can mean that a single assembly can provide different breakaway forces for collapse by changing only the fastener.

Where a fastener is used with an angled abutment, the fastener may be made stronger than would normally be required, in order that the steering column may be prevented from collapsing under abuse conditions or during deployment of an airbag, but will still allow collapse when a combined axial force and torque are applied.

The fastener may comprise a frangible coupling.

The frangible coupling may include a rivet.

The steering column assembly may further comprise a rake-adjustment mechanism.

The steering column assembly may further comprise a reach-adjustment mechanism.

The steering column assembly may further comprise an energy-absorption mechanism.

An energy-absorption mechanism allows energy to be absorbed during collapse in a controlled manner. Energy-absorption mechanisms may include energy-absorbing straps, deformable components, or other such features.

The retaining mechanism may include a runner configured to move within a channel during collapse of the steering column assembly. The channel may be aligned with the longitudinal direction of the support bracket.

The runner may be formed on the support bracket and the channel may be formed in the mounting bracket.

The runner may extend along a horizontal axis about which the support bracket is configured to twist, bend, or rotate in response to the torque.

Various embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of a steering column assembly; Figure 2 is a perspective view of the steering column assembly of Figure 1, with the mounting bracket, shroud, shaft, and rake-and reach-adjustment mechanisms omitted; Figure 3 is a side view of the steering column assembly of Figure 1, showing the forces involved in collapse; Figures 4a to 4c show the retaining mechanism of the steering column assembly of Figure 1 in various stages of collapse; Figure 5 is a perspective view of a second embodiment of a steering column assembly; Figure 6 is a side view of the steering column assembly of Figure 5, showing the forces involved in collapse; Figures 7a to 7c show the retaining mechanism of the steering column assembly of Figure 5 in various stages of collapse; Figure 8 is a perspective view of a third embodiment of a steering column assembly; Figure 9 is a side view of the steering column assembly of Figure 8, showing the forces involved in collapse; Figures 10a to 10c show the retaining mechanism of the steering column assembly of Figure 8 in various stages of collapse; Referring firstly to Figure 1, a steering column assembly 100 is shown. The steering column assembly 100 includes a mounting bracket 102 that is connectable to a fixed part of a vehicle (not shown) and a support bracket 104 secured to the mounting bracket 102. A shroud 106 is supported by the support bracket 104. The shroud 106 houses and supports a shaft 108, which is rotatable and is configured to interconnect a steering wheel (not shown) and a steering rack (not shown) of a vehicle.

A rake-and reach-adjustment mechanism 110 interconnects the shroud 106 and the support bracket 104, allowing both an angle of the shroud 106 relative to the support bracket 104 and the reach-position of the shaft 108 to be adjusted. Although combined in this embodiment, the reach-adjustment mechanism could be separate to or be combined with the rake-adjustment mechanism.

A retaining mechanism 112 interconnects the support bracket 104 and the mounting bracket 102. In normal use, the retaining mechanism 112 secures the support bracket 104 to the mounting bracket 102, preventing relative movement of the two. However, in a crash scenario, the retaining mechanism 112 is configured to allow the support bracket 104 to move relative to the mounting bracket 102, at least in a longitudinal direction, i.e. in a direction towards the front of the vehicle. By doing so, injuries sustained by a driver impacting the steering column assembly 100 may be minimized.

Although the retaining mechanism is described in the singular, a second retaining mechanism is also provided on the other side of the support bracket, forming a symmetrical assembly. In practical use, a one-sided or two-sided retaining mechanism may be provided and the invention is not intended to be limited to a symmetrical assembly.

In the depicted embodiment, an energy-absorption mechanism 114 is included that absorbs energy when the support bracket moves relative to the mounting bracket. This energy-absorption mechanism I14 takes the form of an energy-absorbing strap, although alternatives will be known to the skilled person.

The retaining mechanism 112 is configured to prevent initiation of steering column collapse in any situation where only an axial force is applied to the steering column assembly 100 or where only a torque in the vertical plane containing a longitudinal axis of the shaft 108 is applied to the steering column assembly 100. in this way, abuse of the steering column assembly 100 will not result in accidental initiation of collapse of the steering column assembly 100. Instead, the retaining mechanism 112 will only allow the initiation of collapse when both an axial force and a torque are applied.

The torque that is applied to the support bracket 104 in the vertical plane containing the longitudinal axis of the shaft 108 may be applied deliberately during adjustment of the steering column assembly 100 for rake or may be more accidental, for example when a driver is entering or exiting the vehicle and may pull themselves uses the steering wheel, exerting a torque on the support bracket 104 via the shaft 108. The torque need not be purely in the vertical plane, but a substantial component of the torque must act in this plane.

Similarly, when we refer to axial forces, the force need not necessarily be purely axial, but a substantial component of the force must be in an axial direction.

The first embodiment will now be further described with reference to Figures 2, 3, and 4a to 4c, which show the retaining mechanism 112 in greater detail.

The support bracket 104 comprises a wing 116 and a runner 118 that protrudes horizontally from the wing 116. The runner 118 is received within a channel 120 of a retaining capsule 122. The retaining capsule 122 is secured to the mounting bracket 102, such that movement is prevented. The mounting bracket 102 is only shown in Figure 1.

The channel 120 of the retaining capsule 122 includes two notches 124 that receive the runner 118 of the support bracket in normal use, i.e. with no forces or torques applied to the support bracket 104. With the runner 118 received within the notches 124, it can be seen that the runner is not free to move relative to the retaining capsule 122 due to the side wall of the upper notch 124 forming an abutment 126, and thus the runner 118 is prevented from moving within the channel 120.

in Figure 3, a typical axial force applied to the support bracket 104 is shown. As can be seen, with the runner 118 received within the notches 124, the axial force will simply result in the force passing from the support bracket 104, through the runner 118 and to the retaining capsule 122 via the notches 124. Thus, no movement will be allowed. A typical applied torque is also shown in Figure 3, acting in an upwards direction as would be typical during an adjustment of the rake direction of the steering column assembly 100. The effects of this torque and axial force can be seen in more detail in Figures 4a to 4c.

Figure 4a shows the retaining mechanism 112 in an engaged position. In this position, the runner 118 of the support bracket 104 is prevented from moving relative to the retaining capsule 122 -and therefore the mounting bracket 102 -due to its receipt within the notches 124 and engagement with the abutment 126. The corners of the runners 118 therefore act as latches 130 within the notches 124.

Once a torque, which is sufficient to elastically deflect the support bracket 104, is applied to the support bracket 104, for example by application of a force to a steering wheel attached to the end of the shaft 108, the runner 118 of the support bracket 104 will be rotated within the retaining capsule 112, thus releasing the runner 118 from the notches 124 of the retaining capsule 122. The runner 118 will therefore be aligned with the channel 120 within the retaining capsule 122 and the retaining mechanism 112 can be considered as being in a disengaged position. As can be seen in Figure 4b, not only will the runner 118 of the support bracket be deflected, but also a larger portion of the support bracket 104 including the front portion 128 and the wing 116.

As will be clear, in such a scenario, the runner 118 defines a horizontal axis about which the support bracket 104 rotates, bends, and/or twists.

in the event that the torque is released prior to the application of an axial force, the support bracket 104 will elastically recoil to its original position, the elastic deformation providing a biasing force to bias the runner 118 back into the engaged position. As such, an applied torque will not cause collapse of the steering column assembly 100 without the concurrent application of an axial force.

In the event that an axial force is applied concurrently with the torque, the runner 118 of the support bracket 104 is then enabled to slide within the channel 120 of the retaining capsule 122, allowing collapse of the steering column assembly 100 through relative movement of the support bracket 104 and mounting bracket 102. It will be apparent that once the axial force applied is sufficient to move the runner 118 clear of the notches 124, removal of the torque will not result in re-engagement of the retaining mechanism 112, as the runner 118 will no longer be able to rotate back to engage with the notches 124 and abutment 126. Thus, the collapse mechanism will be initiated and further collapse will be possible solely through application of an axial force.

In the first embodiment, a threshold torque will be defined as the torque required to bend the support bracket 104 through the required angle to release the runners 118 of the wings 116 from the notches 124 of the retaining capsule 122 to prevent the runners 118 engaging the abutment 126. This will depend on the geometry and material making up the support bracket 104, and will be tunable by a skilled person through design of the support bracket 104 and retaining mechanism 112.

The second embodiment of a steering column assembly 200, shown in Figures 5, 6, and 7a to 7c, differs from the first embodiment in that the support bracket 204 is supported directly by the mounting bracket 202. A channel 220 is formed in the mounting bracket 202 within which is received a runner 218, which protrudes from the support bracket 204. The runner 218 fits snugly within the channel 220 at one end and tapers towards the other, allowing slight rotation of the runner 218 within the channel 220, enabling rotation of the support bracket 204. During collapse, the runner 218 is able to slide within the channel 220.

A notch 224 extends perpendicularly from the direction of the channel 220 and is shaped to receive a latch 230 formed in the end of the support bracket, the latch 230 being held against an abutment 226 formed by a wall of the notch 224. in the engaged position, the latch 230 is held within the notch 224, disallowing relative translation of the support bracket 204 and mounting bracket 202. As in the first embodiment, a disengaged position is provided by the movement of the latch 230 out of engagement with the abutment 226 of the notch 224.

In the second embodiment, torque applied in the vertical plane, as shown in Figure 6, causes rotation of the support bracket 204 about an axis defined by the runner 218. This rotation causes the latch 230 to move downwards and out of engagement with the notch 224, placing the retaining mechanism 212 formed by the support bracket 204 and mounting bracket 202 into the disengaged position.

As the retaining mechanism 212 is not moved to the disengaged position by bending, it is necessary to separately bias the retaining mechanism 212 in order to ensure that with the torque removed, prior to initiation of collapse, the retaining mechanism 212 will move back into the engaged position. A biasing mechanism 232 comprising a biasing spring 234 is therefore provided to bias the retaining mechanism 212 into the engaged position. The biasing spring 234 is provided as a leaf spring that loops around the runner 218 and the latch 230 and rests against the mounting bracket 202. As the support bracket 204 rotates, the biasing spring 234 is deformed by the movement of the latch 230 relative to the mounting bracket 202, storing energy that biases the latch 230 back into engagement with the notch 224.

As the biasing spring 234 requires energy to deform, it also acts to provide a defined threshold torque for moving the retaining mechanism 212 into the disengaged position. By changing the size and shape of the biasing spring 234, a predetermined threshold torque can be provided.

The retaining mechanism 212 of the second embodiment also includes a fastener 236 that acts to prevent collapse -even in the disengaged position -when the axial force provided is below a predetermined threshold. The fastener 236, which takes the form of a frangible coupling, which in this case is a rivet, fractures when an axial force above the predetermined threshold is applied. When the retaining mechanism 212 is in the engaged position, the fastener 236 will be protected from the axial force, as this will preferentially be passed through the latch 230 to the mounting bracket 202, via the abutment 226. However, with the retaining mechanism 212 in the disengaged position, the axial force is transmitted through the fastener 236, which can then fracture, allowing the support bracket 204 to move relative to the mounting bracket 202 with the runner 218 sliding within the channel 220. As with the first embodiment, when collapse has been initiated by movement of the support bracket 204, the latch 230 will no longer be able to engage with the notch 224 and thus the abutment 226 does not prevent movement of the support bracket 204.

Figure 7a shows the retaining mechanism 212 of the second embodiment in the engaged position. in Figure 7b, combined torque in the vertical plane -directed anticlockwise as shown -and axial force has caused the latch 230 to disengage from the notch 224 and the fastener 236 to fracture. Figure 7c then shows the retaining mechanism 212 once the support bracket 204 has moved relative to the mounting bracket 202 in a longitudinal direction of the support bracket 204 and mounting bracket 202.

Although each of the embodiments thus far described realises the invention through use of some level of bending of the support bracket, this is not necessarily required. Alternative methods of engaging and disengaging of the retaining mechanism could be used, such as parts movable through the action of hinges, springs, joints, or other features. Such possibilities will be apparent to the skilled person in the context of the present invention.

A third embodiment of a steering column assembly 300 is shown in Figures 8, 9, and 10a to 10c. The third embodiment is similar to the second embodiment in that a notch 324 and latch 330 are provided along with the channel 320 in the mounting bracket 302 and a corresponding runner 318 on the support bracket 304. A fastener 336 is also provided that is frangible above a threshold force. However, the third embodiment differs in that a spring is not provided and there is no active biasing of the retaining mechanism 312.

Rather than providing a biased retaining mechanism, the retaining mechanism 312 of the third embodiment operates to prevent any motion of the support bracket 304 at all unless there are sufficient levels of both torque and axial force. This is provided by use of a notch 324 and latch 330 that are angled relative to the longitudinal direction of the channel 320. The angle of the notch 324 means that the abutment 326 formed is not perpendicular to the direction of travel of the support bracket 304 but is instead at an angle. The angle of the latch 330 and notch 324 -more specifically the angle of the abutment 326 -is approximately 50 degrees from the longitudinal direction of the channel 320, but may differ depending on the desired characteristics of the assembly 300. For example, the angle may be between 30 and 60 degrees or between 20 and 70 degrees, or at any other angle that can be determined by the operating requirements of the assembly 300.

When just a torque is provided, this torque is transformed into a force in the axial direction by the reaction of the latch 330 on the angled abutment 326. The axial force provided in this situation is weaker than the force required to fracture the fastener 336 and therefore no movement of the retaining mechanism 312 is enabled. Similarly, the solely axial force required to break the fastener 336 is configured to be sufficiently high that the abuse forces from either reach-adjustment of the steering column assembly 300 -where provided -or deployment of the airbag, are not sufficient to initiate collapse of the steering column.

However, where both a torque and an axial force are provided, their combined values when transformed into a combined axial force by the shape of the latch 330 and abutment 326 are sufficient to fracture the fastener 336 and thus to initiate collapse of the steering column assembly 300. The specific values of the fracture force for the frangible fastener 336 and the angle of the latch 330 and abutment 326 will be readily determined by the skilled person, without any undue burden.

in this embodiment, the force required to fracture the fastener 336 can be made higher than would normally be required where only an axial force is required to initiate collapse of the assembly 300. With a stronger fastener, abuse conditions of the steering column assembly are less likely to inadvertently initiate collapse of the assembly but, when an axial force is combined with a torque, such as in a typical crash scenario, the combination will still be great enough to cause collapse.

Claims (19)

1. CLAIMS1. A steering column assembly, comprising: a mounting bracket configured to be secured to a fixed part of a vehicle; a support bracket; and a shaft secured, directly or indirectly, to the support bracket; wherein the steering column assembly is configured to collapse under predetermined conditions, whereupon the support bracket is enabled to move relative to the mounting bracket in a longitudinal direction of the support bracket; the steering column assembly further comprising: a retaining mechanism configured to prevent initiation of steering column collapse when the support bracket is subjected to only a substantially axial force along a longitudinal axis of the shaft and to allow initiation of steering column collapse when the support bracket is subjected to both an axial force and a torque in a vertical plane containing the longitudinal axis of the shaft.
2. 2. A steering column assembly according to claim 1, wherein the retaining mechanism is configured to allow initiation of steering column collapse when the axial force and the torque are above respective thresholds.
3. 3. A steering column assembly according to claim 1 or claim 2, wherein the retaining mechanism has an engaged position and a disengaged position whereby, in the engaged position, the retaining mechanism is configured to prevent initiation of steering column collapse and, in the disengaged position, the support bracket is configured to enable initiation of steering column collapse.
4. 4. A steering column assembly according to claim 3, wherein the retaining mechanism is biased into the engaged position and is configured to move from the engaged position to the disengaged position upon application of the torque.
5. 5. A steering column assembly according to any preceding claim, wherein the retaining mechanism includes a biasing mechanism configured to bias the retaining mechanism into the engaged position.
6. 6. A steering column assembly according to claim 5, wherein the biasing mechanism includes a retaining spring.
7. 7. A steering column assembly according to any preceding claim, wherein the retaining mechanism is moved to the disengaged position by the torque.
8. 8. A steering column assembly according to any preceding claim, wherein the retaining mechanism is moved to the disengaged position by bending of the support bracket.
9. 9. A steering column assembly according to any preceding claim, wherein the retaining mechanism includes a latch engageable with an abutment.
10. 10. A steering column assembly according to claim 9, wherein the abutment is formed by a wall of a notch.
11. 11. A steering column assembly according to claim 9 or claim 10, wherein the latch is configured to disengage from the abutment upon application of the torque.
12. 12. A steering column assembly according to any of claims 9 to 11, wherein the abutment is aligned perpendicular to a direction of travel of the support bracket during steering column collapse.
13. 13. A steering column assembly according to any of claims 9 to II, wherein the abutment is aligned at an angle to a direction of travel of the support bracket during steering column collapse.
14. 14. A steering column assembly according to any preceding claim, wherein the retaining mechanism includes a fastener that prevents initiation of steering column collapse when the axial force is below a threshold axial force.
15. 15. A steering column assembly according to claim 14, wherein the fastener comprises a frangible coupling.
16. 16. A steering column assembly according to claim 15, wherein the frangible coupling includes a rivet.
17. 17. A steering column assembly according to comprising a rake-adjustment mechanism.
18. 18. A steering column assembly according to comprising a reach-adjustment mechanism.
19. 19. A steering column assembly according to comprising an energy-absorption mechanism.any preceding claim, further any preceding claim, further any preceding claim, further 20. A steering column assembly according to any preceding claim, wherein the retaining mechanism includes a runner configured to move within a channel during collapse of the steering column assembly.22. A steering column assembly according to claim 20, wherein the runner is formed on the support bracket and the channel is formed in the mounting bracket.23. A steering column assembly according to claim 20 or claim 21, wherein the runner extends along a horizontal axis about which the support bracket is configured to twist, bend, or rotate in response to the torque.