Motor vehicles – Steering by driving – Combined with manual steering
Reexamination Certificate
2000-02-02
2001-05-15
Hurley, Kevin (Department: 3619)
Motor vehicles
Steering by driving
Combined with manual steering
C180S308000
Reexamination Certificate
active
06230829
ABSTRACT:
The present invention relates to vehicle transmission apparatus comprising first and second drivable axles, each drivable axle having two hydraulic motors, one on each side of the vehicle, the apparatus comprising two analogous closed transmission circuits, one for each side of the vehicle, each closed circuit having a hydraulic pump as well as a motor of the first axle and a motor of the second axle.
BACKGROUND OF THE INVENTION
Apparatus of that type is known from Document EP 0 627 335 which shows a hydrostatic transmission vehicle having a plurality of axles, two pumps feeding respective ones of the motors that drive the wheels on each of the two sides of the vehicle. That apparatus offers the advantage of adjusting the respective cylinder capacities of the two pumps in identical manner for travelling straight ahead, or in different manners when, for example, to make a tight turn, it is necessary for the motors driving the wheels on one side of the vehicle to deliver torque that is higher than the torque delivered by the motors driving the wheels on the other side.
Thus, the apparatus disclosed by Document EP 0 627 335 makes it possible to obtain a behavior that differs between the wheels on one side of the vehicle and the wheels on the other side. Unfortunately, it does not make it possible to manage differences in behavior between the wheels situated on the same side of the vehicle.
Document EP 0 547 947 also discloses a vehicle having hydrostatic transmission including three-port dual-capacity motors. All of the motors are fed by the same pump, and it is possible to avoid undesirable differences in behavior between the wheels of the various axles, e.g. wheel spin. Thus, it is possible to achieve a differential lock effect between the front axle and the rear axle, but not to manage in different manners the feed to the motors driving the wheels on one side or the other of the vehicle.
The above-mentioned known apparatus thus offers certain advantages which unfortunately have corresponding drawbacks that are problematic to various extents depending on the conditions under which the vehicle is used.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to provide apparatus that offers the advantages of the above-mentioned known apparatus, but that is free or substantially free from the drawbacks thereof.
This object is achieved by the fact that the hydraulic motors of the second axle are dual-capacity motors, each of which comprises two elementary motors, each elementary motor having first and second elementary connections, for feed or discharge purposes, the first elementary connections being in common to form a first main connection of the dual-capacity motor, while the second elementary connections are separate and form respectively a second main connection and a third main connection of the dual-capacity motor, each of the hydraulic motors of the first axle having at least first and second main connections, for feed or discharge purposes, by the fact that, in each closed circuit, the first main connection of the dual-capacity motor and the first main connection of the motor of the first axle are connected continuously to respective ones of the two ports of the pump of the circuit in question, and by the fact that each closed circuit further includes a selector having at least two positions, disposed on interconnection ducts between the pump, the second and third main connections of the dual-capacity motor and the second main connection of the motor of the first axle.
The invention thus provides an original interconnection between the motors of each of the two closed circuits of the apparatus which includes dual-capacity motors and makes provision, for each closed circuit, to place the selector precisely on interconnection ducts between the pump, the second and third main connections of the dual-capacity motor, and the second main connection of the motor of the first axle. Depending on the configuration of the selectors, it is possible, for example, for each closed circuit, to connect one of the elementary motors of the second axle in series with the motor of the first axle, while the other elementary motor of the second axle can be fed in parallel or can be deactivated.
In any event, insofar as the first main connection of the dual-capacity motor and the first main connection of the motor of the first axle are connected continuously to respective ones of the two ports of the pump of the closed circuit in question, provision is made for one of these two motors always to be fed before the other, it being possible however to chose the selector such that, in one of its positions, it makes it possible to deactivate both elementary motors of the dual-capacity motor, when the vehicle is to travel at high speeds with drive being provided by the motor of the first axle only.
Thus, advantageously, for each closed circuit, the selector has a position for deactivating the second axle, in which position it puts in communication the second and third main connections of the dual-capacity motor and causes them to communicate with that port of the pump to which the first main connection of said dual-capacity motor is connected.
Advantageously, for each closed circuit, the selector has a flow-rate sharing position in which the second main connection of the dual-capacity motor is connected to that port of the pump which is connected to the first main connection of the motor of the first axle, in parallel therewith.
Thus, one of the elementary motors of the dual-capacity motor is fed in parallel with the motor of the first axle, so that the flow rate is shared between said elementary motor which belongs to the second axle and the motor of the first axle.
In this position, it is possible, for example, to chose to connect the third main connection of the dual-capacity motor to the second main connection of the motor of the first axle. This is then a flow-rate sharing and differential lock position because the second elementary motor of the dual-capacity motor is disposed in series relative to the motor of the first axle, while the first elementary motor is disposed in parallel relative to said motor of the first axle.
It is also possible to choose that, for each closed circuit, the selector has a flow-rate sharing and maximum torque position in which the second and third main connections of the dual-capacity motor and the first main connection of the motor of the first axle are connected in parallel to the same port of the pump while the first main connection of the dual-capacity motor and the second main connection of the motor of the first axle are connected in parallel to the other port of the pump.
In which case, for each closed circuit, all of the motors are fed in parallel, so that the total cylinder capacity fed by the pump is equal to the sum of the cylinder capacity of the motor of the first axle and of the cylinder capacity of the dual-capacity motor of the second axle. The vehicle can then develop maximum torque, which is particularly suitable when it is being used under working conditions, on a building site or on difficult terrain. This position thus corresponds to the flow-rate being shared and to maximum torque being obtained.
It is also advantageous that, for each closed circuit, the selector has a flow-rate transfer position for transferring the flow rate to the second axle, in which position the first main connection of the motor of the first axle is connected to a port of the pump, while the second main connection of the dual-capacity motor communicates with that port of the pump which is connected to the first main connection of said dual-capacity motor, and that the third main connection of the dual-capacity motor is connected to the second main connection of the motor of the first axle. In which case, the first elementary motor of the dual-capacity motor is deactivated, and the flow rate of the motor of the first axle is transferred to the second elementary motor, so that both of the motors rotate at the same speed, which amounts to obtaining a differential
Cousin Jean-Claude
Martin Louis
Hurley Kevin
Ladas & Parry
Poclain Hydraulics Industrie
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