Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Patent
1995-06-06
1996-12-17
Lopez, F. Daniel
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
74 60, F01B 300
Patent
active
055842283
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a slanting plate arrangement in a hydraulic axial piston machine having a slanting plate and a pressure plate, between which at least one slider shoe of a piston axially movable in a cylinder body is held, the pressure plate being rotatably connected to the slanting plate by means of an axle element limiting axial movement of the pressure plate with respect to the slanting plate in at least one direction.
In a known slanting plate arrangement of that kind (DE 32 12 402 A1) the axle element is formed by a screw bolt which is guided from the side remote from the pressure plate through the slanting plate and projects through the pressure plate. A nut is screwed onto the end projecting from the pressure plate. The screw bolt is rotatably mounted in the slanting plate.
When the cylinder body rotates, the slider shoes of the pistons, which are arranged in bores in the pressure plate, carry the pressure plate with them, that is to say, the pressure plate is rotated with respect to the slanting plate. During this movement, friction occurs between the slanting plate and the screw bolt. This friction causes wear and tear on the machine. If no preventative measures are taken, it can also lead to the parts that move relative to one another seizing up. To avoid this, the surfaces that rub against one another are lubricated. This lubrication is normally carried out by the hydraulic fluid.
A hydraulic fluid that has a lubricating action is therefore an essential requirement here. This lubricating action is without exception a property of the hydraulic oils until now used as hydraulic fluids. Such oils, in particular those on a synthetic basis, are in some cases toxic, however. Their range of application is therefore limited. From the point of view of their effect on the environment they are being used with increasing reluctance.
The problem on which the invention is based is to be able to use a slanting plate arrangement of the kind mentioned in the introduction even when hydraulic fluids having little lubricating action or even no lubricating action are to be used, for example, water.
This problem is solved in a slanting plate arrangement of the kind mentioned in the introduction in that in the region of contact between the axle element and the pressure plate and/or axle element and slanting plate, a material combination of a metal and a high-strength thermoplastic plastics material is provided.
The use of such a combination of material enables an extremely low-friction sliding contact of the parts moved relative to one another. Lubrication is largely superfluous. In most cases, lubrication is not required at all. For the rest, a film of fluid, such as that provided by water, for example, will be sufficient for lubrication. The function of friction prevention or reduction, which has previously had to be taken on by an operating substance to be supplied from the outside, namely, the hydraulic fluid, is now assumed by parts of the machine. This considerably facilitates control of the operational behaviour. Provision no longer has to be made for the hydraulic fluid to reach the surfaces to be lubricated.
The plastics material is preferably selected from the group of polyaryl ether ketones, especially polyether ether ketones, polyamides or polyamide imides. Such plastics materials are particularly low-friction in combination with metals, so that when they are used, further lubrication by means of oils, greases or similar substances can be omitted without problems.
The plastics material is preferably reinforced by glass, graphite, polytetrafluoroethylene or carbon in fibre form. This measure enables the piston to be stressed by higher forces. Wear is reduced. In particular, the tensile and compressive strength of the plastics material is increased as a result.
In a preferred construction, the axle element is formed by a screw screwed into the slanting plate. It is a simple matter to screw a screw into the slanting plate.
In a preferred construction, a bearing element of plastics material is arranged
REFERENCES:
patent: 3139037 (1964-06-01), Budzich
patent: 3221564 (1965-12-01), Raymond
patent: 3450058 (1969-06-01), Stein
International Plastics Handbook, 2nd ed. New York, Oxford University Press, 1989, pp. 234-235, TP1130.s2413 1987b.
Danfoss A/S
Lopez F. Daniel
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