Power plants – Pressure fluid source and motor – Having a mechanical clutch or brake device in the power train
Reexamination Certificate
1999-06-25
2001-03-13
Ryznic, John E. (Department: 3745)
Power plants
Pressure fluid source and motor
Having a mechanical clutch or brake device in the power train
C092S072000, C192S085060
Reexamination Certificate
active
06199377
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydraulic motor comprising:
a stationary case;
a reaction member secured to the case;
a cylinder block mounted to rotate about an axis of rotation relative to said reaction member and having a plurality of assemblies each comprising a cylinder and a piston, the assemblies being disposed radially relative to the axis of rotation and being suitable for being fed with fluid under pressure;
an internal fluid distributor constrained in rotation relative to the case about the axis of rotation and having distribution ducts suitable for putting the cylinders into communication with fluid feed and exhaust ducts; and
a braking device comprising a dog clutch having first and second series of teeth respectively constrained in rotation with the case and with the cylinder block, and a control piston for controlling engagement and disengagement of the teeth of the dog clutch.
By way of example, it comprises a motor that is slow, operating at low speed and high torque, with such a motor under normal conditions conventionally driving the outlet shaft at rotary speeds of about 75 revolutions per minute (rpm) to 200 rpm, and being capable of generating cylinder capacities of up to 6 liters per revolution, or even about 10 liters per revolution.
Such a motor is used in particular for driving a planetary stepdown gearbox shaft for propelling tracked vehicles.
It is known that using a slow motor for driving a planetary stepdown shaft instead of using a fast motor makes it possible to reduce the number of stepdown stages (e.g. only one stage) in order to obtain the same speed of about 30 rpm to 70 rpm at the outlet from the stepdown gearbox.
Thus, the use of a slow motor associated with a stepdown gearbox makes it possible to reduce the axial size of the assembly constituted by the motor and the gearbox.
OBJECTS AND SUMMARY OF THE INVENTION
The invention seeks to further reduce this axial size by seeking to reduce the axial size of the motor or, at least, by proposing a motor assembly that is extremely compact.
This object is achieved by providing an annular space inside the case around the distributor beside the radial face of the cylinder block adjacent to the distributor, disposing the first series of teeth of the dog clutch and its control piston in said annular space, and securing the second series of teeth to said radial face of the cylinder block in the vicinity of the radially outer periphery of said radial face, such that the teeth of the dog clutch occupy a region of the motor that is remote from the axis of rotation.
This disposition presents several advantages. Firstly, the braking dog clutch is not axially in line with the distributor, but is disposed around it, so that the braking device is received within the axial extent of the distributor, thereby reducing the length of the case of the motor. The second series of teeth of the dog clutch is secured to the radial face of the cylinder block, thereby simplifying assembly of the various elements of the motor and making it possible to transmit braking torque directly by the cylinder block. In addition, the teeth of the dog clutch through which the braking torque is transmitted are situated in a large-diameter region of the motor, thereby making it possible to reduce considerably the risk of premature wear or breakage of motor parts, since for given braking torque, the forces exerted on the parts which transmit said torque are inversely proportional to the distance of said parts from the axis of rotation of the motor.
Advantageously, the cylinder capacity selection slide is disposed in an axial bore situated inside the distributor and is movable at least between a first position and a second position inside said bore, the slide having a selection groove which is situated in its radial periphery. Furthermore, the distribution ducts comprise a first series of distribution ducts which are permanently connected to a first distribution enclosure which is itself permanently connected to a first of the two feed and exhaust ducts, a second series of distribution ducts which are permanently connected to a second distribution enclosure which is itself permanently connected to a second of the two feed and exhaust ducts, and a third series of distribution ducts which, in the first position of the selection slide are connected to the ducts of the first series of distribution ducts via the selection groove and are isolated from the ducts of the second series, and which, in the second position of the selection slide are connected to the ducts of the second series of distribution ducts via the selection groove while being isolated from the ducts of the first series, each of the first, second, and third series of distribution ducts comprising at least one duct which opens out into the axial bore.
This disposition makes it possible to further reduce the axial size of the motor compared with a conventional motor having two cylinder capacities. For such conventional motors, the distribution ducts of the first, second, and third series are put into communication with the main feed and exhaust ducts of the motor via three grooves, one for each series, which grooves are disposed successively in the axial periphery of the distributor. In the advantageous configuration of the invention, the first distribution enclosure to which the ducts of the first series are connected can comprise a first groove situated in the outer axial periphery of the distributor and connected to the first feed and exhaust ducts, while the second distribution enclosure can be connected to the second of said ducts via a second groove situated in the outer axial periphery of the distributor. In contrast, there is no need to provide a third groove for connecting the ducts of the third series to one or other of the feed and exhaust ducts, since the slide selection groove, insofar as it is located on the axis of the motor, puts the ducts of the third series directly into communication with the ducts of the first series or of the second series, depending on the position of the slide. For this purpose, it suffices for at least one duct in each of the first, second, and third series to open out into the axial bore in which the slide is mounted to move, and for it to be possible for the ducts of each series to be interconnected.
Advantageously, the cylinder block has a plane radial communication face, while the distributor has a plane radial distribution face which is held pressed against said communication face by axial thrust means, and the motor has a single bearing for taking up radial forces and for taking up forces exerted axially in the thrust direction of said axial thrust means.
Thus, advantage is taken of the thrust applied by the distributor on the cylinder block so as to use only one rotary bearing (the axial bearing and the orthogonal bearing are united in a single bearing). The single bearing can have conical rollers, or balls that roll with two points of contact. Thus, the axial size of the motor is decreased relative to that of more conventional motors, since they have two conical roller bearings placed one after the other.
Advantageously, the single bearing has a center of thrust which is situated, on the axis of rotation of the motor, in the vicinity of the intersection between said axis and the radial plane defined by the radial axes of the pistons of the cylinder block.
When the motor is in operation, because the various pistons co-operate with the cam in succession, the cylinder block is subjected to parasitic forces tending to tilt it relative to the axis of rotation. The rotary bearing and the force exerted axially by the distributor on the cylinder block must enable these parasitic forces to be compensated. When the center of thrust of the bearing is situated in the vicinity of the intersection between the axis of rotation and the radial plane defined by the radial axes of the pistons of the cylinder block, these forces can be compensated more easily, without it being necessary for the distributor to exert a very hig
Allart Bernard
Bigo Louis
Perot Marc
Ladas & Parry
Poclain Hydraulics Industrie
Ryznic John E.
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