Rotary expansible chamber devices – Working member has planetary or planetating movement – Plural working members or chambers
Patent
1995-10-03
1997-05-13
Freay, Charles G.
Rotary expansible chamber devices
Working member has planetary or planetating movement
Plural working members or chambers
418150, 418171, F04C 1810
Patent
active
056286260
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a hydraulic machine with a gearwheel, which has a midpoint and a predetermined number of external teeth with tooth tips and tooth flanks separated by tooth spaces, and an annular gear, which has a midpoint offset by an eccentricity with respect to the midpoint of the gearwheel and a number of internal teeth with tooth tips and tooth flanks separated by tooth spaces which exceeds by one the number of external teeth, the gearwheel and annular gear orbiting and/or rotating relative to one another and at least the form of the external teeth being created using a set of circles lying with their midpoints on a trochoid.
Such a machine is known, for example from U.S. Pat. No. 2,421,463. The (n+1) internal teeth of the annular gear consist either of free cylindrical rollers or of fixed cylinder segments. The n external teeth of the gearwheel are produced by a set of circles, 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 (FIG. 2) in that a different pair of circles (RH, RK) roll on one another; here the rolling circle (RK) encloses the base circle (RH) (Dubbel, 13th edition, 1970, page 144, FIG. 138).
In the known machine, all the teeth of the gearwheel mesh simultaneously with the corresponding teeth of the annular gear. As many chambers sealed with respect to one another are formed as there are internal teeth in the annular gear. In theory only two pressure regions separated from one another are necessary, however, of which one is pressurized with the pressure on the discharge side and the other is pressurized with the pressure on the inlet side. The larger number of contact points can lead to overdefinition of the system and thus to an increase in leakages. The known construction is also unfavourable because in one position, in which two tooth tips of an internal tooth and an external tooth lie opposite one another, a good seal is required between the pressures on the discharge and inlet sides, but in the opposing region forces between the gearwheel and the annular gear have to be accommodated. In this position, the gearwheel is, as it were, clamped in the annular gear. The tip of the external tooth touches the bottom land of the tooth space, which leads to tangential contact between tooth tip and bottom land (see FIG. 1a). This contact is poorly suited to transfer of forces. The transfer of force between gearwheel and annular gear on the opposite side is effected by line contact between two convex surfaces of relatively small radius of curvature, which leads to high Hertzian stresses. This can lead to damage to the lubricating film and consequently to increased friction, which, if it does not result in lasting damage, significantly reduces the efficiency of the machine.
The invention is therefore based on the problem of improving the efficiency, service life and noise properties of a machine of the kind mentioned in the introduction.
This problem is solved in a hydraulic machine of the kind mentioned in the introduction in that there are provided at least two trochoids, displaced relative to one another in the circumferential direction, for generating a tooth profile, the rolling circles of which and the base circles of which differ from one another.
The tooth form of the external teeth of the gearwheel is now no longer determined exclusively by a single trochoid on which the set of curves is arranged. On the contrary, at least two trochoids are provided. The form of the teeth can thereby be changed, in order, for example, to avoid unnecessary contact between external teeth and internal teeth, without having to forfeit the advantageous effect of tooth generation by means of trochoids. It is not only the base circles of the
REFERENCES:
patent: 3424095 (1969-01-01), Hansen
patent: 4504202 (1985-03-01), Saegusa
patent: 4518332 (1985-05-01), Saegusa
patent: 4673342 (1987-06-01), Saegusa
patent: 5368455 (1994-11-01), Eisenmann
Danfoss A/S
Freay Charles G.
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