Pumps – Three or more cylinders arranged in parallel – radial – or...
Patent
1997-03-04
1999-10-26
Freay, Charles G.
Pumps
Three or more cylinders arranged in parallel, radial, or...
92144, 92154, F04B 112, F04B 2708
Patent
active
059717173
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an axial piston machine.
Such axial piston machines are known in practice. In particular with swash plate machines, the normal force supporting each piston at the swash plate contains a radial component which acts upon the piston as on a beam mounted in the cylinder drum and skewing the piston within the cylinder. In particular with a lack of piston lubrication, such as occurs for example during the start-up phase, this leads to metallic contact between piston and cylinder wall with the consequence of corresponding heating through the frictional forces arising, and the danger of seizing of the piston.
2. Discussion of the Prior Art
From DE-OS 14 03 754 there is known an axial piston machine with which, for the purpose of avoiding the metallic contact between piston and cylinder, there are formed at the periphery of each cylinder or of the associated piston symmetrically formed pressure pockets which are connected via respective chokes and axial through-bores in the piston with the working chamber of the cylinder. The piston is lubricated and hydrostatically balanced by means of the oil, under high pressure, flowing into the pressure pockets from the working chamber during the compression stroke, and in this way the piston is centrally guided in the cylinder without the danger of skewing. The quantity of oil necessary for the hydrostatic balancing is absent from the working circuit of the axial piston machine and thus leads to a reduction of the efficiency of the machine.
The axial piston motor described in DE-OS 18 04 529 has the same advantages and disadvantages, in which axial piston motor there is formed in the wall of each cylinder a circumferential groove which is connected via connection channels in the cylinder drum and in the connection block to the high pressure line of an axial piston pump driving this axial piston motor.
It is the object of the invention to so further develop an axial piston machine of the kind mentioned in the introduction that while maintaining the efficiency of the machine, seizing of the pistons in the cylinders is avoided.
SUMMARY OF THE INVENTION
Instead of the principle known from the state of the art of hydraulic balancing and lubrication of the pistons, the solution in accordance with the invention is based on the principle of cooling of the critical points of metallic contact between pistons and cylinders and can thus be employed not only in oil operated axial piston machines but also in those machines which are intended for operation with a non-lubricating fluid. This cooling is effected by means of a cooling circuit which is connected to the leakage chamber, i.e. completely separated from the working circuit of the axial piston machine, and in this manner does not adversely affect its efficiency. The leakage fluid in the leakage chamber manifests its strongest cooling effect in the start-up phase, that is when the danger of piston seizure is greatest, because in this phase the temperature of the leakage fluid corresponds approximately to the surrounding room temperature. Although, with continuing operation of the axial piston machine, the leakage fluid in the leakage chamber is warmed to higher temperatures, its cooling effect is sufficient to counter the danger of piston seizure--which is significantly reduced due to the piston lubrication which has now come into action--because of the temperature difference, corresponding to the pressure difference, with regard to the fluid standing under high pressure in the working circuit.
In this context it is possible to provide a cooling device for cooling the leakage fluid in the cooling circuit. This cooling device may be constituted in the form of a further leakage fluid receiving chamber in a connection block placed on the housing and containing pressure and suction channels of the axial piston machine.
The cooling regions are preferably formed as annular chambers which surround the cylinders with slight radial spacing. With axial piston ma
REFERENCES:
patent: 3089426 (1963-05-01), Budzich
patent: 5088897 (1992-02-01), Kawai et al.
patent: 5354181 (1994-10-01), Porel
patent: 5486098 (1996-01-01), Kimura et al.
Brueninghaus Hydromatik GmbH
Evora Robert Z.
Freay Charles G.
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