Rotary expansible chamber devices – Working member has planetary or planetating movement – Plural working members or chambers
Patent
1995-12-05
1998-06-30
Vrablik, John J.
Rotary expansible chamber devices
Working member has planetary or planetating movement
Plural working members or chambers
418150, 418171, F01C 110
Patent
active
057724199
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a hydraulic machine with two displacement elements rotatably movable relative to one another, namely, a gearwheel and an annular gear of which the number of teeth is one more than the number of teeth of the gearwheel, in which machine the tooth form of at least one displacement element is defined at least over sections by a trochoid-type curve T=f (RC, E, RT) as the function of a reference circle radius RC, an eccentricity E and a generating circle radius RT.
A machine of that kind is known, for example, from U.S. Pat. No. 2,421,463. The (N+1) teeth of the toothed ring, which project inwards and are consequently also referred to in the following as internal teeth, consist either of free cylindrical rollers or of fixed cylinder segments. The N external teeth of the gearwheel are produced by a circle system, the circles of which lie with their midpoints on a cycloid. The cycloid is created in that a rolling circle rolls on a base circle without slipping, the base circle having a diameter n-times that of the rolling circle. The cycloid is generated from a point in the rolling circle which is spaced a distance from the centre of the rolling circle corresponding to the eccentricity.
The same cycloid can also be created in that a different pair of circles roll on one another; here too, one circle is referred to as a base circle or reference circle and the other circle is referred to as the rolling circle. In this case, however, the rolling circle encloses the base circle or reference circle (Dubbel, 13th edition, 1970, page 144, FIG. 138). Both methods of producing a trochoid are equivalent and can be transformed into one another.
From the time of the first embodiments of this kind of hydraulic machine, there have been attempts to improve the machine, for example, in respect of wear, efficiency, running noise and similar features. Here, efforts include matching the individual parameters to one another, and in some cases ratios are specified within which the individual parameters have to move (EP 0 079 156 B1).
Not all the demands made of such a machine, however, can be met by specifying relationships of parameters or by selecting parameter ranges.
It is admittedly known from DE 14 26 751 A1 to correct the radii of the rolling curves of the two displacement elements with the period of a tooth pitch with respect to a constant value, but this leads only to evening-out of the torque generated in motor operation and to a greater uniformity of the amount of fluid discharged in pump operation, without noticeable improvement in efficiency or noticeable reduction in wear.
The invention is therefore based on the problem of providing a hydraulic machine with which demands that could not previously be met are now satisfied in an improved manner.
This problem is solved in a hydraulic machine of the kind mentioned in the introduction in that of the parameters determining the function f, at least one parameter varies in the circumferential direction periodically with the period of a tooth pitch.
The parameters are therefore no longer constant in the circumferential direction. The tooth profile can now be matched over sections or in areas to the specific local requirements. For example, individual parts of the tooth profile can be better dimensioned in respect of a flank contact pressure whereas other regions can now be formed in such a way that they satisfy the sealing requirements. Previously, this was impossible or only possible to a very limited extent. Generally, a compromise had to be found which fulfils both requirements fairly well. This restriction ceases to apply by virtue of the variation of the parameters in the circumferential direction. Besides the improvement in tightness and consequently the increase in volumetric efficiency, wear can also be reduced and operating characteristics of the machine can be improved, for example, a more uniform torque when the machine is being used as a motor, or a more uniform pumping capacity when the machine is being used as a pump.
In a preferred embodimen
REFERENCES:
patent: 3424095 (1969-01-01), Hansen
patent: 5368455 (1994-11-01), Eisenmann
Hansen Gunnar Lysh.o slashed.j
Petersen Hans Christian
Danfoss A/S
Vrablik John J.
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