Rotary expansible chamber devices – Working member has planetary or planetating movement – Plural working members or chambers
Patent
1995-11-27
1997-01-21
Vrablik, John J.
Rotary expansible chamber devices
Working member has planetary or planetating movement
Plural working members or chambers
F03C 208, F04C 210
Patent
active
055954790
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a hydraulic machine having an annular gear with internal teeth and a gearwheel with external teeth mounted eccentrically therein, the internal teeth comprising one more tooth than the external teeth and the teeth of at least one set of teeth being formed by rotatably mounted rollers. A hydraulic machine according to the invention may operate as either a pump or a motor.
In a known machine of this kind (DE-OS 21 40 962) the tooth tips are subjected to relatively intense wear and tear because the tooth tips of gearwheel and annular gear slide on one another during the relative movement of gearwheel and annular gear. The co-operating teeth of gear wheel and annular gear form individual pressure chambers. Greater wear occurs in the regions of the chambers at low pressure because the teeth of the gearwheel are here pressed additionally by the higher pressure on the opposite side against the teeth of the annular gear. To reduce wear, the teeth of the annular gear are in the form of rotatably mounted rollers. The rotatable mounting can very quickly lead, however, to slight play between rollers and annular gear, which in turn causes leakage between individual pressure chambers which are formed by the co-operation of the teeth of the annular gear and the gearwheel. To reduce the play and facilitate rotation of the rollers, and consequently to decrease the slip between gearwheel and the rollers, each depression in which a roller is mounted is supplied with oil under pressure, so that between the roller and its recess a film of oil forms, which improves the seal and increases the mobility of the roller. Although virtual freedom from slipping and therefore a reduction in wear is achieved by this measure, wear still remains considerable because it is precisely in the region in which the teeth of gearwheel and annular gear together separate a chamber of higher pressure from a chamber of lower pressure that the seal is formed by two opposing convex surfaces, namely the tooth tips. Contact here is therefore virtually only a line contact, in which a tight seal can be achieved only at the cost of a relatively large pressure with which the two tooth tips are pressed against one another. The inner seal is a parameter determining the efficiency of the pump.
GB 602 836 describes a hydraulic machine of a different type with a rotatable rotor which is centrally mounted in a bore of a stator, an annular space being formed between the rotor and stator. Two diametrically opposite projections project from the rotor into this annular space as far as the inner wall of the stator, against which they rest. Mounted rotatably in the stator are gearwheels which together with the projections define a pair each of suction chambers, neutral chambers and pressure chambers. The gearwheels have recesses which take up virtually half of their volume. The gearwheels are driven synchronously by the rotor, which for that purpose has external teeth, so that the recesses open the way at the right time for the projections to travel past.
The invention is based on the problem of providing a hydraulic machine which achieves a relatively good inner seal combined with relatively low wear.
This problem is solved in a hydraulic machine of the kind mentioned in the introduction in that each roller has in its surface at least three axially parallel recesses in which the teeth of the other set of teeth engage.
These recesses have several advantages. Firstly, they allow a better seal between the teeth of one part and the rollers of the other part. Two convex surfaces, which permit only line contact, are no longer positioned opposite one another. On the contrary, a convex surface is now positioned opposite a concave surface, so that the seal is in fact formed by face-to-face contact. The drive of the rollers is no longer effected by friction. On the contrary, the rollers engage with the opposing teeth and are therefore driven directly. As the rollers rotate, the recesses moreover also transport hydraulic fluid, which is consequently forced
REFERENCES:
patent: 3591320 (1971-07-01), Woodling
patent: 3917437 (1975-11-01), Link
Hansen Gunnar L.
Petersen Hans C.
Danfoss A/S
Vrablik John J.
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