Earth working – Automatic power control – Draft responsive
Reexamination Certificate
1999-04-01
2001-03-06
Novosad, Christopher J. (Department: 3671)
Earth working
Automatic power control
Draft responsive
C701S050000
Reexamination Certificate
active
06196327
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to controlling the ride of a tractor coupled to a suspended implement. In particular, the present invention relates to controlling the ride of the tractor by controlling the height of the implement with respect to the tractor.
BACKGROUND OF THE INVENTION
Agricultural tractors provide a variety of functions on a modern farm, including cultivating fields with a variety of implements, towing implements and trailers, and excavating with front end loaders. The implements are typically coupled to the tractor using several mechanical linkages, which permit the implement to be raised and lowered with respect to the tractor by hydraulic cylinders or other actuators. A common hitch provided on many agricultural tractors is the “three-point hitch.” This hitch permits an implement to be coupled to the tractor and supported as an overhanging load, or lowered and forced into the ground. Plows and other ground cultivating implements are typically supported in this manner.
During typical farm operations, tractors with their attached implements in a raised position travel over roads at relatively high speeds to go from field to field. During these transport phases, with the implement raised the suspension, or the lack thereof, causes the tractor to bounce and pitch as it travels. Depending upon the weight of the implement, and the corresponding degree of bouncing and pitching, it can be difficult to control the tractor.
In an attempt to improve roadability, various systems have been developed for interacting with the implements, their associated mechanical linkages and hydraulics to control bouncing and pitching while operating at road speeds. One such system includes circuitry for lifting and tilting an implement combined with a shock absorbing mechanism. This system permits relative movement between the implement and the vehicle to reduce pitching of the vehicle during road travel. Other systems for improving the performance of vehicles have included accumulators, which are connected and disconnected to the hydraulic system depending upon the speed of the vehicle.
Some systems use existing instrumentation on the vehicle, such as load sensors adapted to measure the load on the hitch and position sensors adapted to measure the height of the hitch, to actively control the position of the implement with respect to the vehicle while the vehicle is moving down the road. For example, U.S. Pat. No. 4,924,943 (issued to Maichle, May 15, 1990) discloses an Automatic Pitch Vibration Damping Mechanism for an agricultural tractor that monitors the hitch position and load using position and load sensors that are employed when the implement is being pulled through the earth to control the load and the depth of the implement. In the Maichle reference, the control system provides a signal to the control valve that lifts or lowers the implement. This valve signal is the sum of two signals, a position signal that is a function of the difference between the actual position of the hitch and a nominal hitch position, and a force signal that is a function of the difference between the actual force on the hitch and a nominal force. The force regulating circuit 36 provides a signal to the control valve related to the force on a load pin, and the position regulating circuit 42 provides a signal to the control valve that is related to the distance the hitch is from a nominal position. These two signal components are summed at block 39 and applied to the control valve to move the hitch.
The Maichle reference describes several limitations to his system. The force signal is based on a nominal force created by low-pass filtering the actual force. This nominal force is perturbed when the vehicle goes around a curve causing the implement to rise until it hits a mechanical stop or abutment in the curve, and causing the implement to fall until it hits the pavement once out of the curve. The curve-hitting problem is limited by preventing the nominal force value from changing rapidly. Whenever the system raises the implement up high (e.g. when the control system overcorrects upwardly in the curve) the nominal force value is permitted to change quite slowly by providing a large time constant. These problems arise from the use of a reference hitch force created by taking the time average (i.e. low pass filtering) of the actual hitch force.
What is needed is an improved system for reducing the pitching of a tractor that positions the tractor hitch without requiring a hitch position-based variable low-pass filter time constant for calculating a nominal force value that is combined with an actual force value and presented to a regulator to be later combined with a position error calculation and applied to a valve constant.
SUMMARY OF THE PRESENT INVENTION
In accordance with a first embodiment of the invention a system for reducing the pitching of a tractor having a hitch is provided, including an agricultural tractor, a hitch coupled to the tractor and couplable to an implement that is disposed to raise and lower the implement with respect to the tractor, a force transducer to provide a force signal indicative of a force applied to the hitch by an implement, a position transducer disposed to provide a position signal indicative of a position of the hitch with respect to the tractor, a hydraulic actuator disposed between the tractor and the hitch to raise and lower the hitch, a control valve disposed to control the flow rate of hydraulic fluid to and from the hydraulic actuator in response to a valve signal, and a control circuit that is coupled to and responsive to the force and position transducers to generate the valve signal where the control circuit is configured to receive the force signal and derive the valve signal therefrom and apply it to the control valve.
In accordance with the second embodiment of the invention, a method for reducing the pitching of a tractor having a hitch and an overhanging implement attached to that hitch is provided including the steps of monitoring a force indicative of a load applied to the hitch, monitoring the position of the hitch with respect to the tractor, and deriving a pitch-reducing control valve signal from the position of the hitch and the force.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.
REFERENCES:
patent: 3516498 (1970-06-01), Schowalter
patent: 4108463 (1978-08-01), Old
patent: 4132273 (1979-01-01), Mortonson et al.
patent: 4236724 (1980-12-01), Schillings
patent: 4271910 (1981-06-01), Schafer
patent: 4385353 (1983-05-01), Schneider
patent: 4470121 (1984-09-01), Ebert
patent: 4502708 (1985-03-01), Taplin
patent: 4553605 (1985-11-01), Katayama et al.
patent: 4667744 (1987-05-01), Kauss et al.
patent: 4679633 (1987-07-01), Kauss
patent: 4715012 (1987-12-01), Mueller, Jr.
patent: 4796712 (1989-01-01), Rutkowski et al.
patent: 4807136 (1989-02-01), Rutkowski et al.
patent: 4809179 (1989-02-01), Klinger et al.
patent: 4852657 (1989-08-01), Hardy et al.
patent: 4878543 (1989-11-01), Kauss
patent: 4924943 (1990-05-01), Maichle
patent: 4979092 (1990-12-01), Bergene et al.
patent: 5116188 (1992-05-01), Kurohashi et al.
patent: 5143159 (1992-09-01), Young et al.
patent: 5147172 (1992-09-01), Hosseini
patent: 5372204 (1994-12-01), Scheiss
patent: 5421416 (1995-06-01), Orbach et al.
patent: 5469921 (1995-11-01), Orbach et al.
patent: 5549166 (1996-08-01), Orbach et al.
patent: 5810095 (1998-09-01), Orbach et al.
patent: 5884204 (1999-03-01), Orbach et al.
patent: 5890870 (1999-04-01), Berger et al.
patent: 15 57 862 (1970-04-01), None
patent: 28 56 583 C2 (1980-06-01), None
patent: 29 10 180 A1 (1980-10-01), None
patent: 33 46 892 C2 (1985-07-01), None
patent: 35 01 568 C2 (1985-09-01), None
patent: 34 46 811 C2 (1986-07-01), None
patent: 38 16 166 C2 (1989-11-01), None
patent: 39 42 057 A1 (1991-06-01), None
patent: 41 19 414 A1 (1992-12-01), None
patent: 42 21 943 C2 (1993-03-01), None
pat
Berger Alan D.
Farag Wael
Khan Aftab Ali
Lin Hong Chin
Patel Ketan B.
Case Corporation
Foley & Lardner
Novosad Christopher J.
LandOfFree
EDC draft force based ride controller does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with EDC draft force based ride controller, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and EDC draft force based ride controller will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2496396