Patent Application
20100072738
The present invention relates to a steering apparatus for turning the steerable wheels on a vehicle in response to rotation of a vehicle steering wheel.
Vehicle power steering systems have commonly included a hydraulic motor which is supplied with fluid (oil) from a reservoir by a pump. The pump is driven by an engine of a vehicle. Steering systems having this known construction have been utilized in heavy duty vehicles, such as trucks.
The present invention provides a new and improved apparatus for use in turning steerable vehicle wheels under the influence of force transmitted through a steering column. The steering column extends between a steering wheel and a steering gear which is connected with steerable vehicle wheels. Since the force for operating the steering gear is transmitted through the steering column, a separate pump and hydraulic motor does not have to be provided in association with the steering gear to effect operation of the steering gear.
The apparatus for turning the steerable vehicle wheels includes first and second motors which are connected with the steering column at locations disposed between a steering wheel and the steering gear. A closed loop assembly may be connected with the steering column. In addition, an open loop assembly may be connected with the steering column.
The closed loop assembly includes a first control unit and the first motor. The first control unit is connected with a first sensor which is disposed at a location between the steering wheel and a first gear unit. The first sensor provides an output to the first control unit as a function of torque applied to and rotation of the steering wheel. A feedback sensor is connected with a first control unit and the steering column adjacent to an output from the first gear unit.
The open loop assembly includes a second control unit and the second motor. The second control unit is connected with a second sensor. The second sensor is connected with the steering column at a location between the first gear unit and a second gear unit.
The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings in which:
An apparatus 10 (
Upon rotation of the steering wheel 18, force is transmitted through the steering column 22 to the manually actuated steering gear 20. This force effects operation of the manually actuated steering gear 20. Upon operation of the manually actuated steering gear 20, an output member 24 from the steering gear effects turning movement of the steerable vehicle wheels 12 and 14 through a known linkage 26.
The manually actuated steering gear 20 is operated under the influence of force transmitted to the manually actuated steering gear through the steering column 22. The manually actuated steering gear 20 does not contain a source of force or power, such as a hydraulic motor and/or electric motor. All of the force which is transmitted from the manually actuated steering gear 20 to the linkage 26 and steerable vehicle wheels 12 and 14 is transmitted to the manually actuated steering gear through the steering column 22.
It is contemplated that the apparatus 10 will advantageously be associated with a heavy duty vehicle, such as a truck. Therefore, the manually actuated steering gear 20 must be capable of transmitting relatively large forces from the steering column 22 to the linkage 26 and steerable vehicle wheels 12 and 14.
To enable relatively large forces to be transmitted from the manually actuated steering gear 20 to the steerable vehicle wheels 12 and 14, it is contemplated that the manually actuated steering gear 20 will be constructed with a steering gear ratio of approximately twenty-eight to one (28:1). This results in an input member to the manually actuated steering gear 20 rotating through twenty-eight (28) revolutions for each revolution of the output member 24. Of course, the manually actuated steering gear 20 may be constructed with a gear ratio which is different than this specific gear ratio.
In the embodiment of the invention illustrated in
The apparatus 10 includes a closed loop assembly 32 which is connected with the steering column 22 at a location adjacent to the steering wheel 18. In addition, the apparatus 10 includes an open loop assembly 34. The open loop assembly 34 is connected with the steering column 22 at a location between the manually actuated steering gear 20 and the location where the closed loop assembly 32 is connected with the steering column 22.
In the embodiment of the invention illustrated in
Although the closed loop assembly 32 is connected with the upper link 36 and the open loop assembly 34 is connected with the lower link 38, it is contemplated that the closed loop assembly and open loop assembly may both be connected with a single link in the steering column 22. If desired, the steering column 22 may contain either a greater or lesser number of links.
The closed loop assembly 32 is a control system which automatically acts to maintain a desired output through the steering column 22 in response to rotation of the steering wheel 18. The closed loop assembly includes an electronic control unit (ECU) 46 which is connected with a sensor 48. The sensor 48 has an output which is a function of torque applied to the steering wheel 18 and angular rotation of the steering wheel.
The control unit 46 effects operation of a reversible electric motor 52 as a function of the output from the sensor 48. The electric motor 52 is connected with a gear assembly 56. The gear assembly 56 is a differential gear assembly having a known construction.
A rigid upper portion 60 of the upper link 36 is connected to an input of the gear assembly 56. A rigid lower portion 62 of the upper link 36 is connected with an output from the gear assembly 56. The reversible electric motor 52 is connected to and drives a second input to the gear assembly 56.
The gear assembly 56 may have a construction which is different from the construction of a differential gear assembly. For example, the gear assembly 56 may include a first spur gear which is connected with the upper and lower portions 60 and 62 of the upper link 36. A second spur gear, which is driven by the motor 52, may be disposed in meshing engagement with the first spur gear.
The motor 52 may be operated to cause the gear assembly 56 to assist the operator in rotating the steering wheel 18. The motor 52 may also be operated to resist rotation of the steering wheel 18 to provide ‘feel” to the operator rotating the steering wheel. The control unit 46 effects operation of the motor 52 to either assist or resist steering wheel rotation as a function of vehicle operating conditions.
A feedback sensor 66 is connected with the lower portion 62 of the upper link 36 and with the output from the gear assembly 56. The feedback sensor provides an output to the control unit 46 as a function of angular rotation of the lower portion 62 of the upper link 36. The control unit 46 is operable to effect operation of the reversible electric motor 52 as a function of both the output from the first or upper sensor 48 and the feedback sensor 66. Additional inputs may be provided to the control unit 46 over conductors 68 and 70. The inputs to the control unit 46 over the conductors 68 and 70 may be a function of vehicle speed, lateral acceleration, and/or other operating conditions associated with the vehicles in which the apparatus 10 is disposed.
The open loop assembly 34 uses only the torque and rotational input to a rigid upper portion 76 of the lower link 38 to control an input to a rigid lower portion 78 of the lower link 38. The open loop control assembly 34 does not sense torque and rotation of the lower portion 78 of the lower link 38. The lower portion 78 of the lower link 38 is connected to an input member of the manually actuated steering gear 20.
The open loop assembly 34 includes an input sensor 82 which senses torque and rotation transmitted from the gear assembly 56. The input sensor 82 is connected with a control unit (ECU) 86. The control unit 86 controls operation of a second or lower reversible electric motor 88. The lower motor 88 is connected to the input of a gear assembly 92.
The illustrated gear assembly 92 is a differential gear assembly having an input connected to the upper portion 76 of the lower link 38. The differential gear assembly 92 also has an input connected to the lower reversible electric motor 88. The output from the gear assembly 92 is connected to the lower portion 78 of the lower link 38.
Although the gear assembly 92 is a differential gear assembly having a known construction, it is contemplated that the gear assembly 92 may have a different construction if desired. For example, the gear assembly 92 may be formed by a first spur gear which is connected with the upper and lower portions 76 and 78 of the lower link 38. The reversible electric motor 88 may be connected with the first spur gear by a second spur gear which is disposed in meshing engagement with the first spur gear.
The closed loop assembly 32 is responsive to changes in input torque to the steering wheel 18 and to changes in the rate of rotation of the steering wheel. The open loop assembly 34 senses and modifies the rate of rotation and torque applied to the lower link 38 in the steering column 22. In the event of a malfunctioning of the closed loop assembly 32, the open loop assembly 34 is operable in response to changes in the input torque to and rate of rotation of the steering wheel 18. Since the apparatus 10 includes both the closed loop assembly 32 and open loop assembly 34 redundancy is provided in the control system.
