Device for turning steerable wheels

Abstract

The present invention relates to a device for turning a steerable wheel, comprising a steering member connected to at least one steerable wheel. The steering member moves axially to achieve the turning movement of the at least one steerable wheel. The steering member has a portion with an external thread. A ball nut assembly is connected to the portion with an external thread of the steering member. The ball nut assembly can rotate relative to the steering member to enable the steering member to move axially. A first gear member can rotate in response to the rotation of a steering wheel. A second gear member arranged to mesh with the first gear member rotates in response to the rotation of the first gear member. The ball nut assembly rotates relative to the steering member in response to the rotation of the second gear member.

Description

Technical Field

[0001] The present invention relates to an apparatus for turning a steerable wheel, and more particularly to an electric power steering gear mechanism for turning a steerable wheel of a vehicle, particularly a commercial vehicle such as a heavy truck. Background Art

[0002] A known vehicle steering apparatus includes a steering member that is axially movable to effect turning movement of a steerable wheel. A pinion is arranged to meshingly engage with a rack portion of the steering member. A steering column interconnects the pinion and the vehicle steering wheel. A ball nut assembly is connected to the externally threaded portion of the steering member. A motor is connected to the ball nut assembly. The motor is operable to effect rotation of the ball nut assembly relative to the steering member to cause the steering member to move axially relative to the vehicle. A steering apparatus having this general configuration is disclosed in U.S. Patent No. 7,055,646. Summary of the invention

[0003] The present invention relates to a device for turning a steerable wheel, the device comprising a steering member connected to at least one steerable wheel. The steering member moves axially to achieve the turning movement of the at least one steerable wheel. The steering member has a portion with an external thread. A ball nut assembly is connected to the portion with an external thread of the steering member. The ball nut assembly can rotate relative to the steering member to enable the steering member to move axially. A first gear member can rotate in response to the rotation of a steering wheel. A second gear member arranged to mesh with the first gear member rotates in response to the rotation of the first gear member. The ball nut assembly rotates relative to the steering member in response to the rotation of the second gear member.

[0004] The apparatus for turning a steerable wheel may include an electric motor connected to the ball nut assembly. The motor is operable to apply a rotational force to the ball nut assembly to cause the ball nut assembly to rotate relative to the steering member.

[0005] The second gear member may have a first gear meshingly engaged with the first gear member and a second gear meshingly engaged with a third gear member, the third gear member being connected to the ball nut assembly. The third gear member may be connected to the ball nut assembly and may rotate relative to the steering member together with the ball nut assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The foregoing and other features of the present invention will become more apparent to those skilled in the art after reading the following description with reference to the accompanying drawings, in which:

[0007] Figure 1is a schematic illustration of an apparatus for turning a steerable wheel constructed in accordance with a first embodiment of the present invention; and

[0008] Figure 2 yes Figure 1 An enlarged portion of the device. DETAILED DESCRIPTION

[0009] Figure 1 and Figure 2 1 shows an apparatus 10 for turning a steerable wheel constructed in accordance with the present invention. The apparatus 10 includes a steering column 14 connected to a steering wheel 16. The steering column 14 is also connected to an input member 18 of a gearbox 20. The input member 18 ( Figure 2 ) is supported by bearings 22 for rotation about an axis 24 of the input member relative to a housing 26 of the gearbox 20. When the steering wheel 16 rotates, force is transmitted to the input member 18 through the steering column 14 to rotate the input member relative to the housing 26.

[0010] The input member 18 is connected to a first end of a torsion bar 30. A second end of the torsion bar 30 is connected to a first gear member 32. The first gear member 32 is supported by a bearing 34 for rotation relative to the housing 26 about the axis 24. The torsion bar 30 allows relative rotation between the input member 18 and the first gear member 32. Although the apparatus 10 is described as including a torsion bar 30 that allows relative rotation between the input member 18 and the first gear member 32, it is contemplated that the first gear member may be directly connected to the input member 18. The first gear member 32 may be a bevel gear that is rotatable relative to the housing 26 under the action of forces transmitted through the steering column 14 and the input member 18.

[0011] The first gear member 32 can mesh with a gear 40 on a first axial end of a second gear member 42. The second gear member 42 is supported by a bearing 46 for rotation relative to the housing 26 about an axis 44. The axis 44 extends transverse to the axis 24 and can extend generally perpendicular to the axis 24. The gear 40 on the second gear member 42 can be a bevel gear that can rotate relative to the housing 26 about the axis 44 under the action of forces transmitted through the steering column 14, the input member 18, and the first gear member 32. The gear members 32, 42 can increase the torque applied to the input member 18 and the steering column 14.

[0012] The second gear member 42 has a gear 48 on a second axial end. The gear 48 rotates with the gear 40 and the second gear member 42 relative to the housing 26 about the axis 44. The gear 48 meshes with the third gear member 50, which is connected to the ball nut assembly 52. ​​The ball nut assembly 52 rotates with the third gear member 50 under the action of the force transmitted through the steering column 14, the input member 18, and the first gear member 32 and the second gear member 42. Although the third gear member 50 is described as being connected to the ball nut assembly 52, it is contemplated that the third gear member can be formed on the ball nut assembly 52.

[0013] The ball nut assembly 52 extends within a tubular housing 60. The ball nut assembly 52 is supported for rotation relative to the housing 60 by a bearing 62. The bearing 62 supports the ball nut assembly 52 for rotation about an axis 64 extending generally parallel to the axis 44 of the second gear member 42. The bearing 62 engages a shoulder 66 on the interior of the housing 60 and an end cap 68 of the housing to prevent axial movement of the ball nut assembly 52 relative to the housing.

[0014] The ball nut assembly 52 extends around the externally threaded portion 70 of the steering member 72. The steering member 72 is connected to at least one steerable wheel in any desired manner. The steering member 72 is axially movable within the housing 60 along the axis 64. The ball nut assembly 52 includes a plurality of balls configured to engage the externally threaded portion 70 of the steering member 72. Rotation of the ball nut assembly 52 relative to the housing 60 and the steering member 72 effectively moves the steering member axially relative to the ball nut assembly and axially relative to the housing.

[0015] The reversible electric motor 80 is operable to apply a rotational force to the ball nut assembly 52 to cause the ball nut assembly to rotate relative to the steering member 72 and the housing 60. The electric motor 80 ( Figure 2 ) has an output shaft 82 connected to a drive pulley 84. The drive pulley 84 is connected to a driven pulley 88 by a drive belt 90. The driven pulley 88 is connected to the ball nut assembly 52. ​​It is contemplated that the driven pulley 88 can be connected to the gear 50. Therefore, the driven pulley 88 rotates with the ball nut assembly 52 relative to the housing 60 and the steering member 72. The drive belt 90 transmits force to the ball nut assembly 52 to rotate the ball nut assembly about the axis 64 during operation of the motor and rotation of the drive pulley 84. It is contemplated that the motor 80 can apply rotational force to the ball nut assembly 52 in any desired manner.

[0016] It is contemplated that the gearbox 20 may be connected to a cover 96 for the drive belt 90 and the pulleys 84, 88. The cover 96 may be connected to a support member or plate 98. The electric motor 80 and the housing 60 may be connected to the support member 98. The electric motor 80 may be connected to the support member 98 with the output shaft 82 extending generally parallel to the steering member 72. The support member 98 connects the gearbox 20, the housing 60, and the motor 80 to the vehicle.

[0017] Device 10( Figure 1 ) may include two vehicle condition sensors 100, 102 and an electronic control unit 104 (ECU) for controlling the motor 80 based on the sensed vehicle condition. The vehicle condition sensors 100, 102 may include a torque sensor 100 and a position sensor 102 electrically connected to the ECU 104. The torque sensor 100 may sense the torque applied to the steering wheel 16 and generate a signal indicating the torque. The position sensor 102 may sense the rotational position of the steering wheel 16 and generate an electrical signal indicating the position of the steering wheel. The electrical signals from the torque sensor 100 and the position sensor 102 are sent to the ECU 104. The ECU 104 analyzes the outputs of the sensors 100, 102 and implements the operation of the motor 80 based on the outputs of these sensors. Although the sensors 100 and 102 are shown as being connected to the gearbox 20, it is contemplated that these sensors may be connected to the steering column 14. It is also contemplated that the operation of the motor 80 may be implemented using only the torque sensor 100 or only the position sensor 102.

[0018] Additionally, ECU 104 may have inputs that vary based on sensed lateral acceleration of the vehicle (not shown) or other vehicle operating conditions. ECU 104 receives the signals generated by the sensors and actuates motor 80 to apply axial force to steering member 72 to assist the steerable wheels in turning.

[0019] From the above description of the invention, those skilled in the art will recognize improvements, changes and modifications. The appended claims are intended to cover such improvements, changes and modifications within the technical scope of the art.

Claims

1. A device for turning a steerable wheel, the device comprising: The steering column is connected to the steering wheel. a steering member connected to at least one steerable wheel, the steering member moving axially to achieve a turning movement of the at least one steerable wheel, the steering member having a portion with an external thread; a ball nut assembly connected to a portion of the steering member having an external thread, the ball nut assembly being rotatable relative to the steering member to allow the steering member to move axially; a first gear member rotatable in response to rotation of a steering wheel; a second gear member disposed in meshing engagement with the first gear member, the second gear member rotating in response to rotation of the first gear member, the ball nut assembly rotating relative to the steering member in response to rotation of the second gear member, The invention is characterized in that the second gear member has a first gear meshingly engaged with the first gear member and a second gear meshingly engaged with a third gear member, the third gear member is connected to the ball nut assembly, and the third gear member is connected to the ball nut assembly and can rotate relative to the steering member together with the ball nut assembly, wherein the first gears of the first gear member and the second gear member are bevel gears, and the first gears of the first gear member and the second gear member increase the torque applied to the steering column, Wherein, a diameter of the first gear member is greater than a diameter of the first gear of the second gear member.

2. The apparatus for turning a steerable wheel as claimed in claim 1 further comprising an electric motor connected to the ball nut assembly, the motor being operable to apply a rotational force to the ball nut assembly to cause the ball nut assembly to rotate relative to the steering member.

3. The device for turning a steerable wheel according to claim 2, wherein: The first gear member is rotatable about a first axis, and the second gear member is rotatable about a second axis extending transverse to the first axis.

4. The device for turning a steerable wheel as claimed in claim 3, wherein: The second axis extends generally parallel to an axis of the steering member.

5. The device for turning a steerable wheel as claimed in claim 3, wherein: A gear box supports the first gear member and the second gear member for rotation about the first axis and the second axis.

6. The device for turning a steerable wheel as claimed in claim 5, wherein: The gearbox has an input shaft connected to the first gear member, the input shaft being connected to a steering wheel and rotatable relative to a housing of the gearbox in response to rotation of the steering wheel.

7. The device for turning a steerable wheel as claimed in claim 5, wherein: A support member connects the gear box, the electric motor, and a housing that supports the ball nut assembly for rotation to a vehicle.

8. The device for turning a steerable wheel as described in claim 2 further includes at least one vehicle condition sensor and a control unit connected to the at least one vehicle condition sensor, the at least one vehicle condition sensor providing an output to the control unit, the control unit being connected to the motor and operable to control the operation of the motor based on the output from the at least one vehicle condition sensor.

9. The device for turning a steerable wheel as described in claim 2 further includes at least one of a torque sensor and a position sensor and a control unit, wherein the torque sensor is used to sense the torque applied to the steering wheel, the position sensor is used to sense the position of the steering wheel, the control unit is connected to the at least one of the torque sensor and the position sensor, the at least one of the torque sensor and the position sensor provides an output to the control unit, and the control unit is connected to the motor and is operable to control the operation of the motor according to the output from the at least one of the torque sensor and the position sensor.

10. The device for turning a steerable wheel according to claim 1, wherein: The ball nut assembly extends within a tubular housing, the ball nut assembly being supported for rotation relative to the housing and restricted from axial movement relative to the housing.

11. The device for turning a steerable wheel as claimed in claim 2, wherein: The first gear member is rotatable about a first axis, and the second gear member is rotatable about a second axis extending transverse to the first axis.

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