Steering arrangement for a work machine

A steering arrangement is provided for a work machine that includes a braking device, actuated by an actuation switch, to hold an operator input device in a predetermined position during operation. The braking force of the braking device can be overcome by the operator to make steering adjustments. The work machine may include a second steering arrangement on an opposite side of the work machine to improve operator visibility during close operation. A selector switch is used to select between one or the other steering arrangements.

TECHNICAL FIELD

The present invention relates generally to a steering arrangement, and more particularly to a steering device with a spring return and position locking arrangement.

BACKGROUND

Steering arrangements not having a mechanical connection between the steering wheel and the ground engaging support members are commonly known in work machines. These known arrangements accept steering input commands from the operator through the use of a lever, joystick, steering wheel, or other input device. The steering input commands are transformed to an electric signal that is then transmitted to a controller that sends an electronic signal, responsive to the magnitude of the steering command, to a pump, valve, motor or other mechanical device to turn wheels, speed or slow tracks to actually perform the turning operation.

One example of such a steering apparatus is disclosed in U.S. Pat. No. 4,771,846 issued on Sep. 20, 1988 to Fredrick Venable et al. and is assigned to TRW, Inc. This patent shows a steering system for controlling a vehicle with steerable wheels. The system includes a steering wheel having a steering sensor attached thereto. A signal representative of a desired turning command is transferred from the sensor to a controller. The controller in turn delivers a signal to a hydraulic control valve that controls the flow of fluid to a hydraulic motor that is in turn connected to the steerable wheels.

This steering system also provides the operator with a steering feedback/feel that is provided by an electromagnetic friction brake. The controller in response to a steering wheel position sensor and a steered wheel position sensor controls the electromagnetic brake. The amount of friction force created by the electromagnetic brake depends upon and is limited by the strength of the electromagnet. However this patent is directed towards automobiles that travel at much higher speeds that require constant operator intervention. The patent is also absent any way of dealing with operator fatigue and multi-tasking that an operator of a work machine faces during operation of such a machine.

SUMMARY OF THE INVENTION

In one aspect of the present invention a steering arrangement is provided for a work machine. The work machine includes at least two ground engaging support members positioned on opposite sides of the work machine. A steering motor is connected to each of the ground engaging support members. Each steering motor operatively propels and steers the ground engaging support members in response to a control signal. The steering arrangement includes a support member and a steering input device movable relative to the support member. A biasing mechanism is positioned between the support member and the steering input device. A sensor is positioned to sense the position of said input device and produces an electrical signal indicative of the position. An electromagnetic brake is connected to the input device and the support. A switch is connected to the electromagnetic brake.

DETAILED DESCRIPTION

Referring now to the drawings and particularly toFIG. 1, a work machine10such as an asphalt paver is shown having at least two ground engaging support members12one each positioned on opposite sides thereof. The ground engaging support members12are shown as being tracks, however wheels, rubber belts or other suitable support members12would work equally as well.

A steering system14for the work machine10is shown and includes a steering motor16connected with each of the ground engaging support members12for supplying power thereto. Steering motors16are shown as being fixed displacement fluid motors but alternatively may be electric motors and still function in a similar manner. Each steering motor16is connected to a multi-speed planetary gear arrangement18having a drive wheel20that directly operatively engages one of the ground engaging support members12. The multi-speed planetary gear arrangements18allow for at least two speed ranges such as roading and paving. Individual propel pumps22supply operative power to a respective steering motor16. The propel pumps22are shown for example as being variable displacement pumps but could be other known devices that would supply a variable amount of power output, such as electrical generators, to propel work machine10. In the example shown inFIG. 1the propel pumps22are connected to and draw fluid from and are connected to a fluid reservoir24via conduits26. An engine28is operatively connected to the propel pumps22in a known manner.

A steering arrangement30is connected to an electric control module32. The steering arrangement30supplies a steering signal responsive to the magnitude and direction of an operator steering input request to the electric control module32as will be described below. Control module32is connected and sends electrical signals to each of the propel pumps22. The control module32in turn, supplies a steering output command signal to each of the propel pumps22that is responsive to the magnitude and direction of the desired input request from the operator.

Steering direction is thus controlled by actuation of the propel pumps22. The steering rate and direction is proportional to the amount of fluid flow supplied to and from the steering motors16, which are controlled by controlling the displacement of the respective propel pumps22. The propel pumps22are responsive to the magnitude of the signal from control module32being outputted to the pumps22. For example, if a right hand turn is desired the propel pump22that supplies pressurized fluid to the right steering motor16reduces output and the propel pump22that supplies pressurized fluid to the left steering motor16increases output respectively in response to the magnitude of the turn request. Thus speeding the rotation of the left hand support member12and slowing the rotation of the right hand support member12to maneuver the desired right hand turn.

The control module32receives operating power from a battery34through an ignition switch36when the ignition switch36is placed in a closed/run position. The work machine10may include an additional steering arrangement30′. The additional steering arrangement30′ is connected to the control module32in the same manner as steering arrangement30and allows the operator to sit on either side of the work machine10during operation and still retain steering control of the work machine10while working close to curbs bridge railings and the like. A selector switch38positioned on the operator control panel (not shown) is used to select between steering arrangement30or steering arrangement30′. In this example, the term selector switch38means any of a number of known switching devices that may be used to select between steering arrangement30and steering arrangement30′. Steering arrangement30′ is substantially operatively and structurally similar to steering arrangement30and therefore only steering arrangement30will be described in detail.

Referring now toFIGS. 2 and 3steering arrangement30includes an operator input device40, which is for example a steering wheel, that is connected to one end of an input shaft42. Input shaft42is positioned within a support tube43and rotatably supported at both ends by means of a pair of bearings/bushings44(only one shown inFIG. 3). Support tube43is connected to a stationary support46by a mounting plate45that holds one of the bearing/bushings44in the end of the support tube43. Stationary support46includes a biasing mechanism50disposed about the input shaft42at the opposite end of the operator input device40.

The biasing mechanism50includes a first abutting member52that is contacted by a post54when the operator input device40is rotated in a first direction. When the operator input device40is rotated in the first direction a second abutting member56makes contact with a stationary post58. Post54is connected to a transition plate57that is operatively connected to the input shaft42. While stationary post58is connected to the support46. The second abutting member56of the biasing mechanism50also makes contact with post54when the operator device40is rotated in a second direction and the first abutting member52contacts stationary post58. The outer circumferential surface59of the transition plate57also includes a pair of stops (not shown) that make contact with the stationary post58so as to only allow the operator input device40to rotate a predetermined amount. In this manner the biasing mechanism50causes the operator input device40to be self-centering when not being held and controlled by the operator.

Still referring toFIGS. 2 and 3, a braking device60, which in this example is an electromagnetic brake but may be any of a number of braking arrangements, is operatively connected to input shaft42and the support46. A position sensor62monitors the rotational position of the input shaft42relative to the support44and produces an electrical signal indicative thereof. Position sensor62is a rotary position senor that is connected to the end of the input shaft42and to the control module32as by cable/wire. Position sensor62sends an output signal to the control module32responsive to the magnitude and direction of the rotation of input shaft42. The braking device60is controlled and connected to an activation switch64. In this example, the term activation switch64means any of a number of known switches that may be used to energize the braking device60from fully off position to a position were the braking device60holds biasing mechanism50from causing the operator input device40to rotate bake to a centered position. Activation switch64may be positioned in an operator control panel (not shown) and when activated supplies a current to the braking device60having a force sufficient enough to hold the input shaft42in a stationary manner without allowing the biasing mechanism50to center the operator input device40. However, the operator can overcome the braking force exerted by the braking device60during operation of the work machine10so as to make steering adjustments.

INDUSTRIAL APPLICABILITY

In operation, the steering arrangement14used on a work machine10such as an asphalt paver reduces operator fatigue and offers flexibility in several different ways. For example, if the work machine is operating in a straight-ahead operation or a slow curve, minimal operator input to the steering system14through the use of the operator input device40is required. During these types of operations the operator may choose to lock the steering arrangement30in a predetermined specific position. Closing the activation switch64energizes the braking device60. The force exerted by the braking device60prevents the biasing mechanism50from returning the operator input device40to a centered position, thus holding the operator input device40in a stationary position relative to said support46. As stated above, the force exerted by the braking device60is greater than the biasing mechanism50, however, if steering adjustments are required the operator can reposition the input device40even with the braking device60energized. Thus, no change in signal from the position sensor62will be sent to the control module32unless the operator desires a steering correction.

The steering arrangement14also allows the operator to steer the work machine from either the left or right hand side of the work machine10. When the selector switch38is positioned to allow control signals from the position sensor62of steering arrangement30′, the operator can be seated on the right hand side of the work machine10. This allows the work machine10to be maneuvered close to obstacles such as curbing on the right side of the machine10. When the work machine10is shut down at the end of operation and the ignition switch36is positioned in the off position, the braking60is de-energized. This prevents any inadvertent steering requests at the next work machine10start up.