Motor vehicles – Power – Including traction motor of kind driven by noncompressible...
Reexamination Certificate
1999-10-21
2001-11-27
Hurley, Kevin (Department: 3619)
Motor vehicles
Power
Including traction motor of kind driven by noncompressible...
C180S197000, C180S308000
Reexamination Certificate
active
06321866
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a control system and circuit for use with a vehicle having one or more axles. More particularly, the invention relates to a hydrostatic drive circuit where a controller and hydrostatic motors and pumps are used for propelling and controlling the torque of wheels or drive tracks in a vehicle such as an agricultural vehicle, row crop sprayer, or off-road vehicle.
U.S. Pat. No. 5,931,078 entitled Hydrostatic Drive System, relates to a hydrostatic drive system with a demand-responsive pump and at least one hydraulic circuit or consumer connected to it. U.S. Pat. No. 5,890,982 entitled Continuous Hydrostatic-Mechanical Branch Power Split Transmission Particularly For Power Vehicles, relates to a hydrostatic/mechanical branch power split transmission for power vehicles. U.S. Pat. No. 5,823,072 entitled Vehicle Drive System, discloses a vehicle drive system for mobile hydraulics having a hydrostatic power transmission and a multi-speed selector gear. U.S. Pat. No. 5,782,091 entitled Hydrostatic Continuously Variable Transmission, concerns a continuously variable hydrostatic transmission including a constant displacement type swash plate hydraulic pump and a variable displacement type swash plate hydraulic motor. U.S. Pat. No. 5,683,322 entitled Continuous Hydrostatic-Mechanical Branch Power Split Transmission Particularly For Power Vehicles, relates to a hydrostatic/mechanical branch power split transmission for power vehicles. U.S. Pat. No. 5,628,188 entitled Torque Control Of Hydrostatic Machines Via The Pivot Angle Or The Eccentricity Of Said Machines, discloses a circuit arrangement for controlling the output torque of a hydrostatic machine connected to a hydraulic system having an impressed operating pressure. U.S. Pat. No. 5,615,748 entitled Earth-Based Vehicle concerns a vehicle including a main frame structure, a track assembly mounted to the main frame structure and having an single, endless ground-engaging track extending in a longitudinal direction. A pair of steerable ground-engaging wheels flank the track, and are constructed and arranged to exert a ground bearing pressure sufficient to change a direction of travel of the track in response to turning of the wheels to steer the vehicle.
The above and other documents cited herein are incorporated herein by reference in their entireties and for all purposes. They disclose systems having utility, but leaving an unmet need for a system that tends to optimally distribute torque among vehicle wheels under a variety of operating conditions.
SUMMARY OF THE INVENTION
The invention relates to a control system and hydrostatic drive circuit for controlling displacement of motors and pumps and causing adjustments in the torque of wheels or drive tracks in a vehicle. An accelerometer is used to measure fore and aft accelerations along the longitudinal axis of the vehicle. The real-time acceleration output of the accelerometer is provided as an input to the controller. This enables recognition of when the vehicle is either accelerating in a forward direction or climbing a hill or other incline, as opposed to either decelerating in the forward direction or descending a slope. In use, as a vehicle encounters mud, accelerates, or climbs hills, one or more of the wheels spins faster than the other wheels. The controller, incorporating power distribution control logic and displacement control logic, reduces the torque of the motors that are spinning faster, and increases the torque of the motors that either are not spinning or spinning at a slower speed. When this differential occurs during a forward acceleration or ascent, torque to the faster spinning motors is reduced according to a positive acceleration logic. By contrast, if the vehicle is decelerating in the forward direction or is traveling down an incline, the controller causes an increase in the torque of the motors that are spinning faster, and decreases the torque of the motors that are spinning at a slower speed or are stopped. This can be thought of as a negative acceleration logic. The accelerometer output determines whether the positive or negative acceleration logic is applied. In either event, the controller tends to maintain all wheels rotating at about the same rotational speed within a controllable or desirable tolerance while maximizing tractive effort and power distribution. The controller may be used with electronically controlled variable displacement pumps and motors and open or closed loop hydrostatic circuits. The fluid in the hydrostatic circuit is contained and carried through the hydrostatic circuit in tubes or hoses.
The invention further relates to a vehicle and hydrostatic drive circuit assembly including a frame, axle and at least one hydrostatic drive circuit. The hydrostatic drive circuit includes at least two hydrostatic motors configured to produce a torque and cause a rotation of one or more members. Wheels or tracks are operatively connected to the members. A hydrostatic pump distributes fluid to the hydrostatic motors and transfers power through the hydrostatic drive circuit. The hydrostatic drive circuit can include four motors, with each motor having a displacement during operation ranging from about 1 cc to about 10,000 cc and a hydrostatic pump having a displacement during operation ranging from about 1 cc to about 10,000 cc. The hydrostatic pump or the hydrostatic motors can include finite displacement motors. The hydrostatic motor may be a radial piston motor or an axial piston motor.
A controller causes adjustments of displacement in the motors or pumps, to change the torque applied to a wheel rotating at a first rate, and further causes adjustments of displacement in the motors or pumps to change torque applied to a second wheel rotating at a second rate different than the first rate. The adjustments in displacement and torque of the second wheel may be substantially equal and opposite to the adjustments made to the displacement and torque of the first wheel. The controller may reduce the torque of at least one of the hydrostatic motors associated with the one or more wheels rotating at a first rate, and increase the torque of at least one of the hydrostatic motors associated with the one or more other wheels rotating at the second rate if the second rate is less than the first rate. Preferably the hydrostatic motors and hydrostatic pumps each have a variable range of displacement during operation. The sum of the displacements of the hydrostatic motors and hydrostatic pumps can be substantially constant during operation.
The controller can be used to maintain a substantially fixed ground speed of the vehicle. The controller also can regulate the hydrostatic pump and the hydrostatic motors for torque distribution about the vehicle based on a comparison of the rotational speed of the hydrostatic motors, or based on a comparison of the rotational speed of the hydrostatic motors to the vehicle ground speed. The controller can have an input relating to the speed control lever position and ground speed. The inputs are monitored either sequentially or simultaneously. The controller may compare the rotational speed of the hydrostatic motors with the speed control lever position, and regulate the hydraulic drive circuit such that adjustments are made to the displacements or positions of the swashplates. In response to an indication that ground speed of the vehicle is to be reduced, the controller signals an increase of the displacement of the hydrostatic motors and a decrease of the displacement of the hydrostatic pump. In response to an indication that ground speed is to be increased, the controller signals an increase in the hydrostatic pump displacement and a decrease in the hydrostatic motor displacements. Displacements of motors and pumps preferably are adjusted after exceeding a predetermined difference in rotational speed between hydrostatic motors.
The controller, receiving an indication that a first member has a rotational speed greater than one or more of the other members, can adjust a di
Ag-Chem Equipment Co., Inc.
Hurley Kevin
Kinney & Lange , P.A.
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