Expansible chamber devices – Rotating cylinder – Plural cylinders
Patent
1995-06-06
1996-07-30
Denion, Thomas E.
Expansible chamber devices
Rotating cylinder
Plural cylinders
417269, 74 60, F01B 1304
Patent
active
055401392
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a hydraulic axial piston machine with a cylinder drum, which has at least one cylinder, in which a piston is mounted so as to be axially displaceable, and with a control counter-plate which on rotation of the cylinder drum and the control counter-plate relative to one another connects the cylinder in dependence upon its position with a fluid inlet and a fluid outlet.
The control counter-plate normally has arcuate or kidney-shaped control slots of which one, which is arranged in a region in which the piston moves away from the control counter-plate, is connected to the fluid inlet, while the other, which is arranged in another region in which the piston moves towards the control counter-plate, is connected to the fluid outlet. To prevent the fluid flowing out of or into the cylinder from escaping laterally, that is, to ensure that the fluid flows only from the cylinder to the fluid outlet or from the fluid inlet to the cylinder, the cylinder drum is pressed against the control counter-plate with a certain force. This force is produced by the pressure prevailing in the cylinder which acts on a part of the cylinder end face, optionally assisted by a compression spring, which also presses the cylinder drum against the control counter-plate. The control slots are only partially masked by the end-face openings of the cylinder. Areas remain in which the slots is masked by the end face of the cylinder drum, namely, in the region between the end-face cylinder openings. In these regions the pressure in the cylinders acts in the opposing direction, that is, in a direction to lift the cylinder drum away from the control counter-plate. Thus one seeks to equalise the forces acting on the cylinder drum from the two opposing directions so that the cylinder drum is pressed with the required force against the control counter-plate. The force on the cylinder drum generated by the pressure in the control slots therefore has to be less than the force acting in the opposing direction. This can be achieved, for example, by giving the faces on which the pressure acts suitable dimensions.
In practice, however, it is relatively difficult to achieve the correct equilibrium of forces because, inter alia, frictional forces act between the piston and the cylinder, and exert on the cylinder drum additional tensile or pressure forces, as seen from the cylinder drum looking towards the control counter-plate. These forces can be managed only with difficulty. They are in some cases temperature-dependent and override in particular the forces that are exerted by the pressure of the hydraulic fluid on the cylinder drum. Instabilities can then occur which lead on the one hand to an increased contact pressure between the cylinder drum and the control counter-plate, resulting in a reduction in mechanical efficiency, and on the other hand lift the cylinder drum away from the control counter-plate, resulting in a reduction in the volumetric efficiency. Both cases are undesirable. If such operating conditions occur repeatedly in succession, they can lead to increased wear and tear or even to destruction of the machine.
The invention is therefore based on the problem of equalizing the forces on the control counter-plate in a simple and improved manner.
This problem is solved in a hydraulic axial piston machine of the kind mentioned in the introduction in that between the cylinder drum and the control counter-plate there is arranged a pressure plate which engages the cylinder drum via the intermediary of a spring element, the pressure plate having a through-opening associated with the cylinder, which through-opening is connected to the cylinder in a fluid-tight manner.
A single additional element is therefore joined to the cylinder drum by way of a spring. The spring separates the cylinder drum and the pressure plate. This means that stray forces which arise, for example from friction of the piston in the cylinder, are no longer transmitted directly to the control counter-plate but are absorbed by the spring or by bearings. Th
REFERENCES:
patent: 3131605 (1964-05-01), La Borde
patent: 4838765 (1989-06-01), Wusthof et al.
Jepsen Hardy P.
Martensen Lars
Danfoss A/S
Denion Thomas E.
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