All-wheel steering system and vehicle incorporating the same

• US 8,528,685 B2
• Filed: 07/24/2012
• Issued: 09/10/2013
• Est. Priority Date: 02/05/2007
• Status: Active Grant

• Current Assignee: Toro Company (Toro)
• Original Assignee: Toro Company (Toro)
• Inventors: Scherbring, David J., Gust, Jackie R.
• Primary Examiner(s): Hurley, Kevin
• Application Number:
  US13/556,696
• Publication Number:
  US 20120285753A1
• Time in Patent Office: 413 Days
• Field of Search: 180/408, 180/409, 180/410, 180/412, 180/413, 180/414, 180/415, 180/416, 280/91.1
• US Class Current: 180/408
• CPC Class Codes: A01D 34/64 mounted on a vehicle, e.g. a tractor, or drawn by an animal or a vehicle A01D34/695 takes precedence
• CPC Class Codes: B62D 5/06 fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
• CPC Class Codes: B62D 7/142 specially adapted for particular vehicles, e.g. tractors, carts, earth-moving vehicles, trucks

Abstract

An all-wheel steering system and vehicle, e.g., riding lawn mower, incorporating the same. The system may include a linkage system that operatively connects the vehicle wheels for simultaneous turning. The system, in one embodiment, includes a power steering unit having fixed or variable output for a given steering input. The system may further include a mechanism for reducing speed based upon mower steering angle.

Claims

1. A vehicle comprising:

a frame;

steerable left and right front wheel assemblies both located at or near a forward end of the frame, wherein the left and right front wheel assemblies each comprise;

a front support arm pivotally coupled to the frame; and

a rotatable ground-engaging front wheel coupled to the front support arm;

steerable left and right rear wheel assemblies both located at or near a rearward end of the frame, wherein the left and right rear wheel assemblies each comprise;

a rear support arm pivotally coupled to the frame; and

a rotatable ground-engaging rear wheel coupled to the rear support arm, wherein each of the steerable left and right rear wheel assemblies further includes a wheel motor; and

a steering linkage assembly comprising;

a steering input device coupled to the frame and located proximate an operator station;

a steering actuator coupled to the frame and configured to reposition the steering linkage assembly in response to manipulation of the steering input device;

a rear bell crank pivotally coupled to the frame;

left and right rear tie rods each comprising;

a proximal end pivotally coupled to the rear bell crank; and

a distal end, the distal ends of the left and right rear tie rods pivotally coupled to the left and right rear wheel assemblies, respectively;

a front steering lever arm pivotally coupled to the frame; and

left and right front tie rods each comprising;

a proximal end pivotally coupled to the front steering lever arm; and

a distal end, the distal ends of the left and right front tie rods pivotally coupled to the left and right front wheel assemblies, respectively; and

a longitudinal tie rod comprising an aft end pivotally coupled to the rear bell crank, and a forward end pivotally coupled to the front steering lever arm.

2. The vehicle of claim 1, wherein the steering input device comprises a steering wheel.

3. The vehicle of claim 1, wherein the steering actuator comprises a linear hydraulic cylinder.

4. The vehicle of claim 1, further comprising a hydraulic system, wherein the hydraulic system comprises:

a power steering unit operatively coupled between the steering input device and the steering actuator; and

a hydraulic pump coupled to the power steering unit.

5. The vehicle of claim 4, wherein the power steering unit is selectively configurable between at least a first and a second configuration such that, when in the first configuration, the power steering unit provides a ratio of output of the steering actuator to input of the steering input device that is greater than when the power steering unit is in the second configuration.

6. The vehicle of claim 1, further comprising:

a speed control member selectively movable relative to the frame between a first position corresponding to a first speed of the vehicle, and a second position corresponding to a second speed of the vehicle, the second speed greater than the first speed; and

a cam associated with the rear bell crank, the cam configured to contact the speed control member to limit movement of the speed control member between the first and second positions, wherein the cam is movable in response to movement of the steering input device.

7. The vehicle of claim 6, wherein the cam comprises a cam surface configured to move the speed control member towards the first position when the steering input device is moved from a first position corresponding to a first steering angle toward a second position corresponding to a second steering angle that is greater than the first steering angle.

8. The vehicle of claim 1, further comprising a cutting deck attached to the frame.

9. The vehicle of claim 8, wherein the front and rear wheels are configured to turn the vehicle about a steering center that is located proximate a trim edge of the cutting deck.

10. The vehicle of claim 1, wherein the operator station comprises a seat configured to receive a sitting operator.

11. The vehicle of claim 1, wherein the left and right front wheel assemblies and the left and right rear wheel assemblies are configured such that, when both the front support arms pivot relative to the frame in a clockwise direction, both the rear support arms pivot relative to the frame in a counterclockwise direction.

12. A vehicle comprising:

a frame;

steerable left and right front wheel assemblies both located at or near a forward end of the frame, wherein the left and right front wheel assemblies each comprise;

a front support arm pivotally coupled to the frame; and

a rotatable ground-engaging front wheel coupled to the front support arm;

steerable left and right rear wheel assemblies both located at or near a rearward end of the frame, wherein the left and right rear wheel assemblies each comprise;

a rear support arm pivotally coupled to the frame; and

a rotatable ground-engaging rear wheel coupled to the rear support arm; and

a steering linkage assembly comprising;

a steering wheel rotatably coupled to the frame and located proximate an operator station, the steering wheel configured to control vehicle direction;

a steering actuator coupled to the frame and configured to displace the steering linkage assembly in response to manipulation of the steering wheel;

a rear bell crank pivotally coupled to the frame;

left and right rear tie rods each comprising;

a proximal end pivotally coupled to the rear bell crank; and

a distal end, the distal ends of the left and right rear tie rods pivotally coupled to the left and right rear wheel assemblies, respectively;

a front steering lever arm pivotally coupled to the frame;

left and right front tie rods each comprising;

a proximal end pivotally coupled to the front steering lever arm; and

a distal end, the distal ends of the left and right front tie rods pivotally coupled to the left and right front wheel assemblies, respectively; and

a longitudinal tie rod comprising an aft end pivotally coupled to the rear bell crank, and a forward end pivotally coupled to the front steering lever arm;

a left hydraulic motor to power the rear wheel of the left rear wheel assembly; and

a right hydraulic motor to power the rear wheel of the right rear wheel assembly, wherein the left hydraulic motor and the right hydraulic motor are hydraulically coupled in parallel.

13. The vehicle of claim 12, wherein the left and right front wheel assemblies and the left and right rear wheel assemblies are configured such that when both the front support arms pivot relative to the frame in a clockwise direction, both the rear support arms pivot relative to the frame in a counterclockwise direction.

14. The vehicle of claim 12, wherein the steering actuator comprises a linear hydraulic cylinder coupled between the frame and the rear bell crank.

15. The vehicle of claim 12, wherein the steerable left and right front wheel assemblies are connected to ends of a front frame rail, the front frame rail pivotally coupled to the frame so that the front frame rail pivots about a horizontal pivot axis that is parallel to a longitudinal axis of the vehicle.

16. A vehicle comprising:

a frame;

steerable left and right front wheel assemblies both located at or near a forward end of the frame, wherein the left and right front wheel assemblies each comprise;

a front support arm pivotally coupled to the frame; and

a rotatable ground-engaging front wheel coupled to the front support arm;

steerable left and right rear wheel assemblies both located at or near a rearward end of the frame, wherein the left and right rear wheel assemblies each comprise;

a rear support arm pivotally coupled to the frame; and

a rotatable ground-engaging rear wheel coupled to the rear support arm, wherein the steerable left and right rear wheel assemblies are connected to ends of a front frame rail, the front frame rail pivotally coupled to the frame so that the front frame rail pivots about a horizontal pivot axis that is parallel to a longitudinal axis of the vehicle; and

a steering linkage assembly comprising;

a steering input device coupled to the frame and located proximate an operator station;

a steering actuator coupled to the frame and configured to reposition the steering linkage assembly in response to manipulation of the steering input device;

a rear bell crank pivotally coupled to the frame;

left and right rear tie rods each comprising;

a proximal end pivotally coupled to the rear bell crank; and

a distal end, the distal ends of the left and right rear tie rods pivotally coupled to the left and right rear wheel assemblies, respectively;

a front steering lever arm pivotally coupled to the frame; and

left and right front tie rods each comprising;

a proximal end pivotally coupled to the front steering lever arm; and

a distal end, the distal ends of the left and right front tie rods pivotally coupled to the left and right front wheel assemblies, respectively; and

a longitudinal tie rod comprising an aft end pivotally coupled to the rear bell crank, and a forward end pivotally coupled to the front steering lever arm.