Hydraulic axial piston machine with an inclined plate

Expansible chamber devices – Displacement control of plural cylinders arranged in... – Parallel cylinders

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Details

92 57, 92 71, 417269, 74 60, 91499, F01B 300

Patent

active

055883478

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a hydraulic axial piston machine, having a inclined plate, on which a slider shoe of at least one piston slides on relative movement between a cylinder body receiving the piston and the inclined plate, and a pressure plate articulated on the cylinder body and holding the slider shoe in engagement with the inclined plate.
In machines of that kind, on rotation of the cylinder body with respect to the inclined plate, or on rotation of the inclined plate with respect to the cylinder body, the piston is moved axially. During the pressure stroke, that is to say, on decrease in the volume of the cylinder moved by the piston, the inclined plate exerts a pressure on the slider shoe. During a suction stroke, on the other hand, the pressure plate has to hold the slider shoe in engagement with the inclined plate. In accordance with the axial back and forth movements of the piston, the pressure plate must also tilt back and forth, the tilting angle range extending, for example, from about -15.degree. to about +15.degree.. On each rotation, the entire tilting angle range has to be passed through, once in the positive direction and once in the negative direction.
Since the articulated connection between the cylinder body and the pressure plate has to accommodate considerable forces, considerable friction is generated there. So that the losses and the wear and tear caused by the friction are not allowed to become too great, it is known to lubricate this articulation. The oil that is already present, serving as hydraulic fluid, is normally used for that purpose. But this leads to the disadvantage that the selection of hydraulic fluids is restricted to hydraulic oils. Even here, choice is not unlimited since not all oils have the same good lubricating properties. In the past, there has therefore been an increasing tendency to use synthetic oils, but these are being regarded with growing disfavour from the point of view of compatibility with the environment.


SUMMARY OF THE INVENTION

The invention is therefore based on the problem of being able to operate a hydraulic axial piston machine even with a hydraulic fluid that has relatively poor or even no lubricating properties.
This problem is solved in a hydraulic axial piston machine of the kind mentioned in the introduction in that between pressure plate and cylinder body there is arranged a bearing element with a bearing surface of plastics material, which slides with low friction on a counterpart made of metal lying against the bearing surface.
The lubricating function, which was otherwise performed by a continually freshly supplied hydraulic fluid, for example, an oil, is now replaced by the use of a machine element, namely, the bearing element, which works together with the counterpart with low friction. Since the plastics material is provided only in the bearing element, the machine can also be subjected to the same forces as before. Mechanical stability is virtually unaffected by the bearing element, especially as the bearing element has only relatively small dimensions compared with the remaining parts. In that case, the strength and stability can continue to be determined by the construction of the pressure plate and the cylinder body.
In an advantageous construction, the bearing element is formed from plastics material. A peripheral face of the bearing element then forms the bearing surface. Such a bearing element can be manufactured relatively easily.
The plastics material is preferably selected from the group of high-strength thermoplastic plastics materials on the basis of polyaryl ether ketones, in particular polyether ether ketones, polyamides, polyacetals, polyaryl ethers, polyethylene terephthalates, polyphenylene sulphides, polysulphones, polyether sulphones, polyether imides, polyamide imide, polyacrylates, and phenol resins, such as novolak resins. Such plastics materials can work together with metals with relatively low friction, even when there is no lubrication by oil.
The plastics material preferab

REFERENCES:
patent: 5017095 (1991-05-01), Burgess et al.

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