Gerotor Type Motor With Pressure Biased Rotary Valve

Abstract

The invention relates to a gerotor type rotary piston machine. The casing has a main axis and the gerotor gear set includes an externally toothed star member which is rotatable about its own axis and orbital about the casing main axis. A main drive shaft is rotatable about the casing axis and a universal type wobble shaft connects the main shaft to the gerotor star member. An annularly shaped valve is mounted in said casing for rotation about the casing main axis. The valve is in surrounding relation to the wobble shaft and is driven by the wobble shaft. An annularly shaped pressure plate which is nonrotatable but is capable of a small amount of axial movement is positioned behind the valve. The pressure plate is biased against the valve by pressurized fluid from the inlet port to provide sealing for both sides of the valve. Sealing rings are provided at the rear of the pressure plate betwen it and the casing to prevent leakage from the high pressure inlet regions to the low pressure outlet regions.

Description

The invention relates to a rotary piston machine with an internal splined shaft and wherein an internally toothed ring fast with the casing engages a rotatable externally toothed wheel which is coupled with a disc shaped rotary slide so as to rotate therewith, the rotary slide being disposed between a plate having axial ducts and a part of the casing, which plate and casing part are held in spaced relationship by a ring on the casing, which ring surrounds the rotary slide.

Machines of this kind operate as pumps or motors. Since the cycle of filling and emptying the displacement chambers formed between the toothed wheel and the toothed ring proceeds at a greater speed than that at which the main shaft rotates, the machine has as a pump a large delivery volume and as a motor a large torque. The valve plate cooperates with the plate having ducts as a distributor valve in order to supply pressurized fluid to the displacement chambers and to discharge it therefrom in the correct sequence, despite the slow speed of revolution of the rotary slide. For this purpose the rotary slide generally has valve openings, the number of which is equal to twice the number of teeth on the toothed wheel, whereas the plate having ducts contains valve openings which cooperate with the aforementioned valve openings and the number of which is equal to the number of teeth on the toothed ring.

In a known construction (German Pat. application Ser. No. 1,931,143, as laid open), the rotary slide is inserted between the plate having ducts and the casing part, in a sliding fit. At higher pressures however there arises the danger of a slight increase in the size of the gap between the plate having ducts and the casing part, particularly as a result of elastic stretching of the axially extending fixing screws. Consequently, gaps of increased size are created between the rotary slide and the plate having ducts and the casing part respectively, and leakage fluid can pass along these gaps. The quantity of leakage fluid increases with the third power of the width of gap. This is particularly troublesome in the case of the rotary slide since the openings at which differing pressures obtain are located very closely to each other.

The object of the invention is to provide a machine of the above described kind in which the leakage losses occurring at the rotary slide can be kept very small.

According to the invention, this object is achieved by providing between the rotary slide and the casing part a pressure plate which is non-rotatable but axially displaceable and which has supply and discharge ducts and, on that of its faces remote from the rotary slide, a limited annular surface which communicates with the pressurized port.

In this construction, the pressure plate is acted upon by an axial force which is equal to the product of the area of the annular surface and the working pressure of the machine. Consequently, the pressure plate is pressed against the rotary slide, and the rotary slide against the plate having ducts. The gaps between these parts can therefore be kept small and the leakage losses can be kept correspondingly low. As the working pressure rises, the pressure-applying force also increases, so that substantially constant conditions are achieved over the entire working range. The pressure plate of course covers that end face of the rotary slide remote from the plate having ducts; however, since the non-rotatable pressure plate is provided with supply and discharge ducts, the supply to the rotary slide is not impaired.

It is particularly advantageous if the annular surface adjoins an annular distributing channel which supplies one set of valve openings in the rotary slide. Since the one set of valve openings and therefore also the associated annular distributing channel must in any case communicate with the pressure port, this arrangement results in the annular surface being supplied with pressurized fluid in a very simple manner.

In very many cases a rotary piston machine can be driven in both rotary directions, and this means that one or other of the ports can be selectively used as the pressure port. Assuming that this is so, an extremely simple construction is obtained if two concentric annular surfaces are present on that face of the pressure plate remote from the rotary slide, those annular faces being separated from each other by an O-ring and each of them extending from an annular distributing channel, the channels each communicating with a port. It has been found that it generally suffices to use one half of the end face as the pressure transmitting annular surface, so that both annular surfaces are located on that face of the pressure plate remote from the rotary slide.

In a preferred embodiment, one of the annular distributing channels is of the end face and the other at the peripheral surface of the pressure plate in the housing part. In this arrangement, one of the annular surfaces can extend to the outer edge of the pressure plate and this results in good utilization of space. Furthermore, two annular distributing channels of relatively large cross section can be accommodated in the casing part.

Preferably at least one set of the supply and discharge ducts in the pressure plate is formed by an annular aperture which is divided by axial partitions. The partitions make it possible for the pressure plate to be a one piece element despite the presence of the aperture. These partitions can also contribute towards the application of pressure to the pressure plate if they extend to the face of the pressure plate that is presented to the rotary slide. To ensure correct operation they should then however be disposed opposite the mouths of the axial ducts in the duct plate.

The invention will now be described in greater detail by reference to a preferred embodiment illustrated in the annexed drawing which shows a longitudinal section through a rotary piston machine in accordance with the invention.

The casing consists of an end plate 1, a casing part 2, a duct plate 3, a toothed ring 4, and a further end plate 5, these elements being interconnected by means of screw bolts 6, 7 and 8, and the gaps between them being closed with the aid of O-rings 9, 10, 11 and 12. A main shaft 13 is mounted in the casing part 2 by means of a roller bearing unit and in the duct plate 3 by means of a plain bearing. A sealing element seals off the zone through which the main shaft 13 projects from the casing. A cavity 14 in the main shaft 13 accommodates a universal joint shaft 15. The coupling head 16 of this shaft meshes with teeth 17 in the main shaft 13, and a further coupling head 18 of the shaft meshes with teeth 19 on a wheel 20 which, by means of teeth in the form of cylindrical rollers 21, meshes with the toothed ring 4, displacement chambers being formed between the teeth of the wheel 20 and those of the ring 4. The outer periphery of the main shaft 13 carries keys 22 which engage in axial grooves 23 in a disc shaped rotary slide 24 and drive this slide.

The casing part 2 has an annular extension 25 which in addition to surrounding the rotary slide 24 also surrounds a pressure plate 26, which is prevented from rotating by pins 27 but can move slightly in the axial direction. Also provided in the casing part 2 are two ports 28 and 29. The port 28 communicates with an annular distributing channel 30, and the port 29 with an annular distributing channel 31. The annular distributing channel 30 extends along the face of the pressure plate 26, and the annular distributing channel 31 along the outer circumferential surfaces of this pressure plate 26 and the rotary slide 24. Two O-rings 32 and 33 define a first annular surface 34 which communicates directly with the annular distributing channel 30. Disposed outwardly of the O-ring 33 is a second annular surface 35 which extends to the outer circumference of the pressure plate 23 and communicates directly with the annular distributing channel 31. The pressure plate has supply and discharge ducts 36 and 37. These are formed by an annular aperture which is divided by axial partitions 38. These partitions extend to that face of the pressure plate presented to the rotary slide 24 and are disposed where the oppositely positioned face of the duct plate 3 is not interrupted. The same applies in the case of the ducts 36 which begin at the periphery of the pressure plate and likewise have partitions 39.

The rotary slide 24 has valve passages 40 and 41 which communicate alternately with the annular distributing channel 30 and the annular distributing channel 31. The number of these passages is equal to twice the number of teeth on the wheel 20. They form valve openings which cooperate with corresponding valve openings of axial ducts 42 in the duct plate 3. The number of these axial ducts is equal to the number of teeth on the ring, and each terminates at the outer part of a gap between two teeth fixed in the casing.

If the machine is operated as a motor and is supplied with pressurized fluid through the port 28, the annular surface 34 transmits pressure. The force thus applied to the pressure plate 26 presses the latter against the rotary slide 24 and presses this slide against the duct plate 3. The gaps between these parts are therefore kept small. If pressurized fluid is passed to the port 29 when the direction of rotation is changed, the annular surface 35 transmits the pressure. The annular surface 35 is approximately as large as the annular surface 34 and likewise leads to compression of the pressure plate 26, the rotary slide 24 and the duct plate 3.

Claims

We claim:

1. A gerotor type rotary piston machine comprising a casing having a main axis, expansible chamber means having cyclically movable chamber forming means, rotatable shaft means connected to said chamber forming means, an annularly shaped valve mounted in said casing for rotation about said main axis, said valve being in surrounding relation to said shaft between the opposite ends thereof, fluid passages in said casing between said valve and said expansible chamber means, drive means connecting said rotatable shaft means and said valve in driving relation, said valve having first and second sets of circumferentially extending and alternately arranged inlet and outlet ports cooperable with said casing passages, said second set of valve ports being spaced from the inner and outer circumferences of said valve, an annularly shaped pressure plate in abutting engagement with said valve, said pressure plate being rotationally fixed relative to said casing and axially movable relative to said valve, said pressure plate having first and second fluid passage means having fluid communication with said first and second sets of valve ports, said second fluid passage means being spaced from the inner and outer circumferences of said pressure plate, first and second annularly shaped channels in said casing having respectively fluid communication with said first and second pressure plate fluid passage means, said second annularly shaped channel having the mouth thereof in radial registration with said second fluid passage means, said pressure plate having first and second surface portions respectively radially inwardly of said first and second annular channels with at least one of said surface portions being subjected to pressurized fluid in either of said annular channels to axially bias said pressure plate into abutting engagement with said valve.

2. A gerotor type rotary piston machine according to claim 1 wherein said first set of valve passages has the form of recesses relative to the periphery of said valve.

3. A gerotor type rotary piston machine according to claim 1 wherein said pressure plate first fluid passage means has the form of recesses relative to the periphery of said pressure plate.