Steering column assembly for vehicle

Abstract

4. The repairing kit for automotive dents, according to claim 1, wherein the at least one wheel is adapted to move along the side of the steering wheel in a direction of rotation from a point of view of the touch screen. The at least one wheel is adapted to move along the side of the steering wheel in a direction of rotation from a point of view of the touch screen.

Description

Technical Field

[0001] The present invention relates to steering column assemblies and particularly, but not exclusively, to steering column assemblies for use with steer-by-wire hand wheel actuators. Background Art

[0002] In a steer-by-wire device, a hand wheel (steering wheel) is connected to one end of a shaft, the angular displacement of which is measured to generate a signal for controlling the orientation of the steered wheels of the vehicle. Such devices are also usually provided with an electric motor connected to the shaft to apply a torque in a direction opposite to the torque applied at the steering wheel in order to provide the driver with road feel.

[0003] In a steer-by-wire arrangement, it is important to limit the rotation of the steering wheel and the shaft to which it is connected, to ensure that the maximum rotation of the steering wheel in both directions corresponds to the maximum pivoting of the steered wheels in both directions. If the rotation of the steering wheel is not limited, the steering wheel may still rotate when the steered wheels are pivoted to their maximum pivoting angle, so that the rotational position of the steering wheel no longer corresponds to the position of the steered wheels.

[0004] One way to limit the rotation of the steering wheel (and in particular the shaft to which the steering wheel is connected) is to provide a lead screw-threaded rod that rotates with the steering wheel. A nut is threadedly mounted on the lead screw-threaded rod and is prevented from rotating, whereby a rotation of the steering wheel and therefore of the lead screw-threaded rod that rotates with the steering wheel in this manner causes the nut to be displaced longitudinally along the lead screw-threaded rod. By providing end stops, the longitudinal displacement of the nut along the lead screw-threaded rod is limited and thus the maximum rotation of the steering wheel in both directions is limited.

[0005] However, it is important to ensure that the driver's steering feel is not impaired by any friction or inertia within the steering drive train. In particular, it is important to ensure that the longitudinal displacement of the nut along the screw-threaded rod is not impeded, as this will be felt by the driver and in extreme conditions the nut may get stuck or locked in place, which may prevent the driver from steering the vehicle. Summary of the invention

[0006] It is an object of the present invention to overcome or alleviate the problems of such known steering column assemblies.

[0007] According to a first aspect of the present invention, a steering column assembly for a vehicle comprises:

[0008] case;

[0009] a shaft rotatably mounted relative to the housing and configured to attach a steering wheel at one end;

[0010] an elongated rod configured to rotate with the rotatably mounted shaft and including a leadscrew-threaded portion;

[0011] a nut member threadably mounted on the lead screw-threaded portion of the elongated rod;

[0012] an elongate guide for the nut member, the elongate guide limiting rotation of the nut member relative to the housing, whereby rotation of the elongate rod causes axial displacement of the nut member along the rod; and

[0013] an end stop positioned to engage the nut member to limit a maximum axial displacement of the nut member along the elongated rod in both directions;

[0014] Wherein, a gap is provided between the elongated guide and the nut member.

[0015] By providing a gap between the elongated guide and the nut member, misalignment of the screw-threaded rod is tolerated. In particular, it is ensured that any run-out in the screw-threaded rod will not cause the nut member to get stuck on the elongated guide, as any obstruction could be felt by the driver and could cause the nut member to get stuck or otherwise locked in place.

[0016] In one embodiment, the elongate guide comprises a channel for receiving the nut member.

[0017] Preferably, the gap between the channel and the nut member is achieved by oversizing the channel relative to the nut member.

[0018] This allows the nut member to rotate slightly together with the screw-threaded rod until the nut member engages the guide channel, after which further rotation of the screw-threaded rod causes longitudinal displacement of the nut member along the guide channel.

[0019] Preferably, the cross-section of the nut member is non-circular.

[0020] Preferably, the channel and the nut member are complementary in shape, wherein a gap is provided between the channel and the nut member.

[0021] In one embodiment the nut member comprises a plurality of faces.

[0022] One or more of the faces of the nut member may be concave.

[0023] By providing recesses on one or more of the faces of the nut member, a number of lobes are effectively formed on the nut member which are engageable with the guide channel.

[0024] Preferably, the elongate guide is located in the housing.

[0025] Preferably, the elongate rod and the rotatably mounted shaft are coaxial.

[0026] The steering column assembly preferably further comprises a sensor configured to generate an electrical signal in response to rotation of the rotatably mounted shaft.

[0027] The steering column assembly preferably further comprises a motor configured to apply a torque to the rotatably mounted shaft in an opposite direction to the externally applied torque.

[0028] The nut member is preferably formed from a non-metallic material, such as a plastic material.

[0029] The nut member may be formed from a material that is less dense than the lead screw-threaded rod.

[0030] By having a low mass nut member, the inertia of the nut transitioning from one direction to the other is low and will not be felt by the driver as any form of disturbance.

[0031] According to a second aspect of the present invention, a steering column assembly for a vehicle comprises:

[0032] case;

[0033] a shaft rotatably mounted relative to the housing and configured to attach a steering wheel at one end;

[0034] a sensor configured to generate an electrical signal in response to rotation of the rotatably mounted shaft;

[0035] a motor configured to apply a torque to the rotatably mounted shaft in a direction opposite to the externally applied torque;

[0036] an elongated rod disposed coaxially with the rotatably mounted shaft and configured to rotate therewith and including an external lead screw-threaded portion;

[0037] a nut member threadably mounted on the lead screw-threaded portion of the elongated rod, the cross-section of the nut member being non-circular;

[0038] an elongated guide channel in which the nut member is located, the elongated guide channel limiting rotation of the nut member relative to the housing, whereby rotation of the elongated rod causes axial displacement of the nut member along the rod, wherein the guide channel is coaxial with the elongated rod and complementary in shape to the nut member, wherein there is a gap between the channel and the nut member; and

[0039] An end stop is positioned to engage the nut member to limit a maximum axial displacement of the nut member along the elongated rod in both directions.

[0040] Preferably, the nut member comprises a plurality of faces.

[0041] Preferably, one or more of the faces of the nut member are concave.

[0042] The nut member is preferably formed from a non-metallic material, such as a plastic material.

[0043] The nut member may be formed from a material that is less dense than the lead screw-threaded rod.

[0044] The invention also comprises a vehicle comprising a steering column assembly according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Illustrative embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0046] Figure 1 is a perspective view of an embodiment of a steer-by-wire handwheel actuator according to the present invention;

[0047] Figure 2 Viewed along the direction of arrow II-II Figure 1 A transverse cross-section of the actuator;

[0048] Figure 3 is along Figure 2 View from the direction of arrow III-III Figure 1 A longitudinal cross section of an actuator;

[0049] Figure 4 is along Figure 2 Arrow IV-IV View Figure 1 a longitudinal cross-section of the actuator; and

[0050] Figure 5 is formed Figure 1 A perspective view of the nut and lead screw on an enlarged scale of a portion of the actuator. DETAILED DESCRIPTION

[0051] The steer-by-wire handwheel actuator 10 comprises an elongated metal steering column housing 12 and an actuator assembly 14 secured to one end of the steering column housing 12. A steering shaft 16 passes coaxially through the elongated metal housing 12 and, in use, a steering wheel (not shown) is connected to an outer end 18 of the steering shaft 16. The steering shaft 16 is rotatably supported on bearings (not shown) within the housing 12.

[0052] The inner end 22 of the steering shaft 16 is connected to a conventional torque / angle sensor 24 which generates an electrical signal based on the rotational position of the steering wheel and steering shaft 16. The electrical signal is used in a known manner to control the angular position of the vehicle's steered wheels in a steer-by-wire control arrangement.

[0053] The inner end 22 of the steering shaft 16 is also connected by way of a tubular shaft 26 to an internal splined bore 28 of a hub 32 to which a steering shaft pulley 34 is connected.

[0054] The hub 32 is rotatably mounted within the housing 14. The opposite end of the splined bore 28 is enlarged and receives one end of a lead screw 36 which is coaxially aligned with the steering shaft 16 and rotatably mounted within an actuator housing 43 of the actuator assembly 14 by bearings 38, 40 at its opposite ends.

[0055] The electric motor 42 is also mounted in the actuator housing 43 and is configured to drive an output shaft 44, which is arranged parallel to the lead screw 36 and to which an output pinion 46 is connected. A drive belt 48 is fed around the output pinion 46 and around the steering shaft pulley 32, and the motor 42 is actuated to apply torque to provide feedback to the steering shaft 16, thereby giving the driver a road feel. The applied torque is felt by the driver as tactile feedback or controlling the angle of the steering wheel.

[0056] The lead screw 36 is made of metal (e.g., steel) and is threaded over most of its length, as shown at 50. Like the electric motor 42, a plastic lead screw nut 52 is disposed within the actuator housing 43 (see FIG. Figure 2 and Figure 4 ). The plastic lead screw nut 52 is easily received on the threaded portion 50 of the lead screw 36. Accordingly, as Figure 2 and Figure 3 As shown in FIG. 4 , the threaded portion 50 of the lead screw 36 is also disposed within the actuator housing 43. The actuator housing 43 defines a chamber 51 for accommodating the electric motor 42 and a cavity 53 (adjacent to the chamber 51). The cavity 53 is configured to accommodate the threaded portion 50 of the lead screw 36 and the lead screw nut 52. The partition wall portion 45 of the actuator housing 43 is disposed between the chamber 51 and the cavity 53. Figure 2 As shown in FIG. 4 , the cavity 53, the partition wall portion 45, and the chamber 51 may be integrated with each other to form the actuator housing 43. Figure 2 , the cavity 53 may include a first wall portion 47 and a second wall portion 49 extending from the partition wall portion 45. The first cover 55 may be attached to the first wall portion 47 and the second wall portion 49 of the actuator housing 43 during the assembly process to enclose the plastic lead screw 52 within the actuator housing 43. Similarly, as Figure 1 As shown in the figure, a second cover 57 can be provided separately to easily enclose the electric motor 42 within the actuator housing 43 during the assembly process. The aforementioned arrangement of the actuator assembly 14 (the arrangement of the electric motor 42, the lead screw 36, and the lead screw nut 52 relative to the actuator housing 43) requires minimal vehicle packaging space relative to conventional arrangements.

[0057] like Figure 2 As best seen, the nut 52 is generally square in cross-section, but four of its faces are slightly concave, so that the four corners of the nut form convex corners 54. Figures 2 to 4 As shown in FIG. 1 , the nut 52 is constrained to move within a cavity 53 which is formed by Figure 2 and Figure 3 The elongated channel 56 is provided in the form of a Figure 2 and Figure 3 , the elongated channel 56 is defined by the dividing wall portion 45 and the first wall portion 47 and the second wall portion 49 of the actuator housing 43. As shown, the elongated channel 56 can be generally square in shape to at least partially constrain the nut 52. However, the nut 52 is not tightly fitted within the channel 56. Instead, the channel 56 is oversized relative to the nut 52 (or the nut 52 is undersized relative to the channel 56) so that there is a gap between the nut 52 and the channel 56, so that the nut 52 is loosely fitted in the channel 56.

[0058] As the lead screw 36 is rotated by the steering shaft 16, the nut 52 may rotate slightly by a few degrees before engaging the wall of the passage 56. When the nut 52 engages the wall of the passage 56, the nut is prevented from further rotation, and further rotation of the lead screw 36 causes the nut 50 to shift longitudinally along the lead screw.

[0059] The maximum displacement of the nut 52 along the lead screw 56 is determined by a first end stop 60 and a second end stop 62 positioned within the housing 14. A corresponding pair of rubber O-rings 64, 64' is positioned behind each end stop 60, 62 to provide a damping effect to cushion the contact between the nut 52 and the end stops 60, 62. In addition, the end stops 60, 62 include thrust bearings 38, 40 that prevent the nut 52 from locking when reaching the end of its travel along the lead screw 56.

[0060] By providing a clearance between the passage 56 and the nut 52, any misalignment of the screw-threaded rod 36 is tolerated. In particular, it is ensured that any runout in the screw-threaded rod 36 will not cause the nut 52 to get caught on the wall of the passage 56, as any hindrance could be felt by the driver and could cause the nut 52 to get stuck or otherwise locked in place.

[0061] In addition, by forming the nut 52 from a lightweight material (e.g., a plastic material), the driver's steering feel is not compromised by friction or inertia in the steering drive train. In addition, the nut 52 with low mass helps in reverse steering situations because the inertia when transitioning from one direction to another is small and will not be felt as a disturbance by the driver. However, the nut 52 can be formed from one or more other lightweight materials. For example, the nut can be formed from one or more lightweight materials having a density less than that of the screw-threaded rod 36 installed in a threaded manner.

[0062] The invention is not restricted to the details of the foregoing embodiments.

Claims

1. A steering column assembly for a vehicle, the steering column assembly comprising: case; a shaft rotatably mounted relative to the housing and configured to attach a steering wheel at one end; an elongated rod configured to rotate with the rotatably mounted shaft and including a leadscrew-threaded portion; a nut member threadably mounted on the lead screw-threaded portion of the elongated rod, wherein the nut member is non-circular in cross-section; an elongated guide for the nut member, the elongated guide limiting rotation of the nut member relative to the housing, whereby rotation of the elongated rod causes axial displacement of the nut member along the rod; as well as an end stop positioned to engage the nut member to limit a maximum axial displacement of the nut member along the elongated rod in both directions; Wherein, the elongated guide is larger in size than the nut member, and a gap is provided between the elongated guide and the nut member to tolerate misalignment and jump of the elongated rod, so that as the elongated rod rotates through the axis, the nut member can rotate before the nut member engages with the wall of the elongated guide, and when the nut member engages with the wall of the elongated guide, the nut member is prevented from further rotation, and further rotation of the elongated rod causes the nut member to shift longitudinally along the elongated rod.

2. The steering column assembly of claim 1, wherein: The elongated guide includes a channel that receives the nut member.

3. The steering column assembly of claim 2, wherein: The passage is oversized relative to the nut member.

4. The steering column assembly of claim 3, wherein: The channel is complementary in shape to the nut member, wherein a gap is provided between the channel and the nut member.

5. The steering column assembly of claim 1, wherein: The nut member includes a plurality of faces.

6. The steering column assembly of claim 5, wherein: One or more of the faces of the nut member are concave.

7. A steering column assembly according to any one of claims 1 to 6, wherein: The elongated guide is located in the housing.

8. The steering column assembly according to any one of claims 1 to 6, wherein: The nut member is formed of a non-metallic material.

9. The steering column assembly according to any one of claims 1 to 6, wherein: The nut member is formed from a material with a lower density than the screw-threaded portion.

10. The steering column assembly according to any one of claims 1 to 6, wherein: The elongated rod is coaxial with the rotatably mounted shaft.

11. The steering column assembly according to any one of claims 1 to 6, further comprising: A sensor is configured to generate an electrical signal in response to rotation of the rotatably mounted shaft.

12. The steering column assembly of claim 11, further comprising a motor configured to apply torque to the rotatably mounted shaft to provide tactile feedback to a driver or to control an angle of the steering wheel.

13. A steering column assembly for a vehicle, the steering column assembly comprising: case; a shaft rotatably mounted relative to the housing and configured to attach a steering wheel at one end; a sensor configured to generate an electrical signal in response to rotation of the rotatably mounted shaft; a motor configured to apply torque to the rotatably mounted shaft to provide tactile feedback to a driver or to control an angle of the steering wheel; an elongated rod disposed coaxially with the rotatably mounted shaft and configured to rotate therewith and including an external lead screw-threaded portion; a nut member threadably mounted on the lead screw-threaded portion of the elongated rod, the cross-section of the nut member being non-circular; an actuator housing defining a chamber and a cavity, the chamber housing the motor, the cavity being in the form of an elongated guide channel in which the nut member is located, the elongated guide channel limiting rotation of the nut member relative to the housing whereby rotation of the elongated rod causes axial displacement of the nut member along the rod, wherein the guide channel is coaxial with the elongated rod and complementary in shape to the nut member, wherein by being oversized relative to the nut member, there is a gap between the channel and the nut member to accommodate misalignment and run-out of the elongated rod, such that as the elongated rod is rotated by the shaft, the nut member is able to rotate before the nut member engages a wall of the elongated guide, when the nut member engages the wall of the elongated guide, the nut member is prevented from further rotation and further rotation of the elongated rod causes longitudinal displacement of the nut member along the elongated rod; and An end stop is positioned to engage the nut member to limit a maximum axial displacement of the nut member along the elongated rod in both directions.

14. The steering column assembly of claim 13, wherein: The nut member includes a plurality of faces.

15. The steering column assembly of claim 14, wherein: One or more of the faces of the nut member are concave.

16. A steering column assembly as claimed in any one of claims 13 to 15, wherein: The nut member is formed of a non-metallic material.

17. A steering column assembly as claimed in any one of claims 13 to 15, wherein: The nut member is formed from a material with a lower density than the screw-threaded portion.

18. A vehicle comprising a steering column assembly as claimed in any preceding claim.

Images