Motor vehicles – Steering gear – With fluid power assist
Utility Patent
1998-12-11
2001-01-02
Swann, J. J. (Department: 3611)
Motor vehicles
Steering gear
With fluid power assist
C180S418000, C180S006240
Utility Patent
active
06167982
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
BACKGROUND OF THE INVENTION
The present invention generally relates to combines and more particularly to a tracked articulated (jointed) combine with improved tracked steering system capability.
Tracked vehicles, which utilize metallic sectioned tracks or rubber traction belts, have been steered historically by establishing a speed differential between the endless tracks on opposite sides of the vehicle. Means causing the track on the right side of the vehicle to stop or run slower than the track on the left side of the vehicle causes the vehicle to turn to the right and vice versa if the progress of the left track is retarded. Such turning regimen initially was accomplished by clutch/brakes affixed to the individual tracks for retarding movement of the track. Such a steering regimen results in abrupt steering changes and in the retarded track sliding sideways with a resulting dirt pile being established on the outside of the sliding track and high stress on the vehicle suspension.
Another tracked vehicle steering system is a proportion steering system. This steering system for tracked vehicles causes a speed differential to be created between the two tracks rather than retarding one of the tracks. This “differential steering” system was an improvement in that the turns were less abrupt, less dirt was piled up because sliding of the inside track was less, and the suspension system was subject to less stress, as some power was being applied to both tracks during the turn. A common implementation of a differential steering system involved driving each track with its own hydraulic motor with the relative flow of hydraulic fluid in a hydrostatic transmission arrangement being diverted to either track utilizing a diverter/divider valve controlled by the vehicle operator. The two hydraulic motors, then, provided both propulsion and steering. In a straight-ahead direction, both motors receive the same percentage of the total flow of fluid from the hydrostatic pump. To perform a turn to the right, say, the percentage of the total hydraulic fluid or oil flow to the right side motor is decreased with a simultaneous and concomitant increase in oil flow to the left side motor. A reverse flow is used for a left turn.
Differential steering also can be achieved by utilizing a hydraulic motor which, when receiving flow from a steering wheel activated pump, applies power to a mechanical differential which is connected to both tracks. Such a steering system is shown in Caterpillar Company brochure # YEDA 3003 (September 1997).
While differential steering represents a definite improvement in the art of tracked vehicle steering, such systems are not without their own problems and limitations. To be effective in guiding a vehicle, particularly an articulated combine, the differential steering system depends on both endless tracks or belts encountering relatively the same traction conditions. Since these vehicles operate in agricultural fields with widely varying soil and soil moisture conditions, a wide differential of track traction can be encountered from one side of the vehicle to the other.
Such differential traction problem is illustrated by the following example. The vehicle operator desires to turn the combine to the right and, accordingly, turns the steering wheel to the right. The ground, however, is firmer and less slippery on the right side of the vehicle under the right track or belt than under the left side. The differential steering system causes the left side track to speed up and the right side track to slow down to effect a turn to the right. However, because the right side track has more traction than the left, increasing the speed (power) of the left track merely causes it to “spin” in the loose soil or mud and it will be overpowered by the slower turning, but better tractioned, right track. The net result of these circumstances is that the vehicle will slide or turn left when the operator is calling for a right turn even though the steering system is trying to turn the vehicle to the right. Moreover, this slide or turn (drift) to the left will continue until the left side track encounters soil with at least as good, or better traction than the right side track. At this point in the turn, however, the operator has probably strongly “oversteered” to the right and the left track is running much faster than the right. When the left track encounters firm soil, the vehicle will lunge to the right before the operator can recover.
This steering limitation can be mitigated somewhat in a tractor application by reducing the load from the towed implement by raising it until more equal left/right soil conditions are encountered. However, the operator of a combine does not have this option since he cannot reduce the load and must follow precisely the rows or position of the crop to be harvested.
Thus, it will be readily apparent that there exists a real need for improving the steering of tracked vehicles in general and of tracked combines specifically.
BRIEF SUMMARY OF THE INVENTION
Broadly, one aspect of the present invention relates to a steering system for an articulated tracked combine composed of (i) a forward unit having a pair of powered non-steering wheels or tracks (fitted with a differential in their axle) and (ii) a tracked rearward unit having powered steerable tracks. This steering system includes a pivoting articulation joint interconnecting the forward unit and the rearward unit. The rearward unit is fitted with a differential tracked steering system in steering connection with an operator steering wheel for steering of the articulated tracked combine.
Another aspect of the present invention is directed to a steering system for an articulated tracked combine composed of (i) a forward unit having a pair of powered non-steering wheels or tracks and (ii) a tracked rearward unit having steerable tracks, wherein steering of said combine is effected by an operator steering wheel in steering connection with the rearward unit tracks. Such novel steering system includes a pair of steering articulation cylinder assemblies connected between the forward unit and the rearward unit. An articulation joint interconnects the forward unit and the rearward unit. An angle sensor is mounted at the joint for sensing the relative position of the forward unit and the rearward unit. Another sensor is mounted at the steering wheel to sense its position. A controller is connected with the angle sensor and with the steering wheel sensor for monitoring their concordance and for activating the steering articulation cylinder assemblies when the concordance varies by a threshold value in order to re-establishes the concordance within the threshold value.
Advantageously, the controller publishes the output of each sensor to the operator so that the operator knows the relative position of the two units at all times. Also, a manual override also is desirably provided so that the operator can actuate the articulation steering cylinder assemblies as is necessary, desirable, or convenient. Additionally, the operator can call for a combination steering approach by using the articulation steering cylinder assemblies full time. Finally, the operator can manually articulate the tracked combine by actuating the articulation steering cylinder assemblies. Thus, a multitude of steering options are available to the operator of the novel articulated tracked combine of the present invention.
Advantages of the present invention include the ability to readily steer the tracked combine in conventional fashion desirably using a conventional differential tracked steering system. Another advantage is the concomitant ability to overcome slippage of a track during such differential steer automatically so that the operator need only concentrate on steering the combine where desired. A further advantage is the ability of the operator to assist the differential tracked steering system by manually actuating the articulation steering cylinder assemblies. These and othe
Lum L.
Mueller & Smith LPA
Swann J. J.
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