GB2575994A

GB2575994A - Steering column assemblies

Info

Publication number: GB2575994A
Application number: GB1812440.4A
Authority: GB
Inventors: Appleyard Michael
Original assignee: TRW Ltd
Current assignee: TRW Ltd
Priority date: 2018-07-31
Filing date: 2018-07-31
Publication date: 2020-02-05
Anticipated expiration: 2038-07-31
Also published as: GB2575994B; GB201812440D0; CN110775143B; CN110775143A; DE102019210382A1

Abstract

A steering column assembly for a vehicle has a housing (120, 122, Figure 2) and a shaft 118 rotatably mounted with respect to the housing to which a steering wheel is attachable at one end. An engagement portion 136 is connected to and rotates with shaft 118, and an end stop 140 is located in the path of engagement portion 140 to engage with engagement portion 136 upon rotation of shaft 118 through a predetermined angle in both directions. End stop 140 is displaceable in opposing directions, which may compensate for the width of the end stop and provide a full 180° rotation of the steering wheel in each direction. Resiliently deformable stops 150 may be provided to cushion end stop 140 close to its maximum displacement. The arrangement is particularly suitable for use in a steer-by-wire vehicle.

Description

Steering Column Assemblies

The present invention relates to steering column assemblies and in particular, but not exclusively, to steering column assemblies for use with a steer-by-wire hand wheel actuator.

Autonomous vehicles are intended to be used primarily in an autonomous mode, in which control of the vehicle is carried out without manual intervention. However, it is desirable for autonomous vehicles to be controllable manually if necessary or desired, and for that reason, vehicle controls such as a steering vehicle (typically having a “steer-by-wire” operation) must be provided.

In such steer-by-wire arrangements, a hand wheel (steering wheel) is connected to one end of a shaft whose angular displacement is measured to generate a signal which is used to control the orientation of the steering wheels of the vehicle.

One problem which occurs with such steer-by-wire arrangements arises from the fact that the vehicle wheels are not physically connected to the steering wheel, in contrast to a conventional mechanical steering arrangement. The steered wheels can only pivot through a given range of motion, and it is therefore important to limit the maximum rotational of the steering wheel so that it corresponds to the maximum extent of pivoting of the steered wheels, otherwise a driver of the vehicle would be able to rotate the steering wheel indefinitely when the steered wheels are at their maximum steering angle.

In accordance with the present invention, a steering column assembly for a vehicle comprises a housing, a shaft rotatably mounted with respect to the housing and being configured for attachment of a steering wheel at one end, an engagement portion connected to and configured to rotate with the shaft, and end stop means located in the path of the engagement portion and engageable with the engagement portion upon rotation of the shaft through a predetermined angle, wherein the engagement portion is engageable with end stop means upon rotation of the shaft through predetermined angles in both directions and wherein the end stop means is displaceable in a straight line in opposite directions.

With a fixed end stop means, the maximum displacement of the engagement member and the shaft is limited by the thickness of the end stop means. By having a displaceably mounted end stop means, it is possible to compensate for the width of the part of the end stop means with which the engagement means comes into contact, thereby providing a full 180°rotation of the steering wheel in each direction.

In one embodiment, the end stop means comprises an elongate member slidably disposed in recesses in the housing and the projection extending radially outwardly from the elongate member with which the elongate portion is engageable.

Displacement of the elongate member is preferably limited in both directions by the recesses in which it is mounted.

Preferably, resiliently deformable means are provided to cushion the end stop means as it approaches its maximum displacement.

The resiliently deformable means may conveniently comprise resiliently deformable members, for example elastomeric members, located in the recesses in which the elongate member is slidably mounted.

In one embodiment, the engagement means comprises a collar rotatable with the shaft and having a radially-extending projection engageable with the end stop means.

Preferably, the collar is secured to, and rotates with, the shaft.

By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings, in which:

Figures 1(a) and 1(b) are transverse and longitudinal cross sections respectively through an embodiment of steer-by-wire steering wheel turn limiting mechanism in accordance with the present invention; and

Figure 2 is a longitudinal cross-section through a portion of a steering column of a steer-bywire steering mechanism, to which the turn limiting mechanism of Figure 1 has been fitted.

An embodiment of steer-by-wire steering wheel turn limiting mechanism 110 in accordance with the present invention is illustrated in Figures 1 and 2. The mechanism is installed inside a steering column 112 of a hand wheel actuator assembly which is part of a steer-by-wire system for a road vehicle.

A steering wheel (not illustrated) is attached to one end of a main shaft 118 (the right-hand end of the shaft as shown in Figure 2) and is rotatably mounted in a tubular extension 120 of a main housing 122 by means of a bearing 124 and another bearing (beyond the right of Figure 2 - not illustrated). The main housing 122 also carries a motor 128 whose output is connected to the inner end of the main shaft 118 in order to provide a sensation of road feel to the driver.

A closely-fitting annular steel hub 130 is fitted onto the main shaft 118 at a location near the end removed from the steering wheel, and is locked to the main shaft 118 by means of a rectangular key 132. The outer face of the hub 130 is splined and a rotation limiting member 134 is overmoulded onto the outer face of the hub 130. The rotation limiting member 134 is generally tubular, but is provided with a radially extending projection 136. The hub 130 and rotation limiting member 134 are mounted on the main shaft 118 such there the radially extending projection 136 is in its lowermost position when the steering wheel to which the main shaft 118 is connected is in the straight ahead position.

An end stop member 140 is mounted in the tubular extension 120 of the main housing 122 and comprises a straight, solid metal cylinder 142 having an integrally-formed radially extending circular rib 144 at its longitudinal centre. The end stop member is mounted at a position diametrically opposite the radially extending projection 136 when the steering wheel is in the straight ahead position, with the two portions of the solid metal cylinder 142 on either side of the rib 144 each being slidably mounted in a respective complementarilyshaped recess 146, 148 in the tubular extension 120. The end stop member 140 is therefore able to shuttle longitudinally between two extreme positions in which the two elements of the end stop member 140 abut rubber stops 150, 152 secured in the bottom of the recesses 146, 148.

As the steering wheel, and the main shaft 118 to which the steering wheel is attached, is rotated, the rotation limiting member 134 is also rotated. When the main shaft 118 is rotated through 180° in a first direction, the radially extending projection 136 of the rotation limiting member 134 abuts a first face of the rib 144 of the end stop member 140 and displaces the end stop member until its opposite end abuts its associated rubber stop 150, 152, thereby limiting rotation of the steering wheel in the first direction. Turning the steering wheel in the opposite direction causes the radially extending projection 136 to engage the opposite face of the rib 144 of the end stop member 140 and displaces it until the opposite end of the end stop member abuts its associated rubber stop 150, 152, thereby limiting rotation of the steering wheel in the second direction.

By allowing the end stop member 140 to be displaceable longitudinally after engagement with the radially extending projection 136, it is possible to compensate for the width of the projection 136, thereby allowing a full 180° of travel in each direction. In addition, the rubber stops 150, 152 provide cushioning at the extremes of travel.

Claims

1. A steering column assembly for a vehicle, comprising a housing, a shaft rotatably mounted with respect to the housing and being configured for attachment of a steering wheel at one end, an engagement portion connected to and configured to rotate with the shaft, and end stop means located in the path of the engagement portion and engageable with the engagement portion upon rotation of the shaft through a predetermined angle, wherein the engagement portion is engageable with end stop means upon rotation of the shaft through predetermined angles in both directions and wherein the end stop means is displaceable in a straight line in opposite directions.

2. A steering column assembly as claimed in claim 1, wherein the end stop means comprises an elongate member slidably disposed in recesses in the housing and a projection extending radially outwardly from the elongate member with which the engagement portion is engageable.

3. A steering column assembly as claimed in claim 2, wherein the displacement of the elongate member by the engagement portion is limited in both directions by the recesses in which it is mounted.

4. A steering column assembly as claimed in any of claims 1 to 3, further comprising resiliently deformable means to cushion the end stop means as it approaches maximum displacement.

5. A steering column assembly as claimed in claim 4 when appendant to claim 2 or claim 3, comprising a resiliently deformable member located in the recesses in which the elongate member is slidably mounted.

6. A steering column assembly as claimed in claim 5, wherein the resiliently deformable means comprises an elastomeric member.

7. A steering column assembly as claimed in any of the preceding claims, wherein the engagement means comprises a collar rotatable with the shaft and having radially extending projection engageable with the end stop means.

5

8. A steering column assembly as claimed in claim 7, wherein the collar is secured to, and rotates with, the shaft.