Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Radially disposed cylinders
Patent
1983-09-06
1987-01-13
Croyle, Carlton R.
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Radially disposed cylinders
91491, F01B 1306
Patent
active
046355359
DESCRIPTION:
BRIEF SUMMARY
This invention relates to rotary radial piston hydraulic pumps and motors which are for convenience herein referred to as "hydraulic machines".
A rotary radial piston machine may be defined for the purposes of this specification as including a rotary cylinder unit surrounding and mounted to rotate on a ported pintle. The cylinder unit includes a number of generally radial cylinders each containing a piston and each piston engages a slipper which contacts a surrounding annular track ring. The ports in the pintle are connected to external fluid inlet and outlet passages and thus rotary movement of the cylinder unit is accompanied by radial displacement of the pistons and corresponding displacement of fluid through the passages. Existing radial piston hydraulic machines suffer from a number of problems and disadvantages and it is an object of the invention to provide an improved radial piston design which will at least partly overcome the existing difficulties.
One of the problems concerns the positioning of the rotary cylinder unit in an axial direction on the pintle. According to a first aspect of the invention the cylinder unit is free to float (within limits) in an axial direction.
Surprisingly it is found that this freedom to float is quite acceptable since the cylinder unit can be designed to provide a self-centering or positioning effect. Thus, according to a preferred feature of the invention the opposing end faces of the cylinder unit and/or the casing are inclined towards the axis or otherwise shaped to provide a hydrodynamic self-centering effect.
Another problem arises from the eccentric position of the track ring with respect to the pintle. It follows that the enclosed fluid volume between adjacent pistons is continually changing during each revolution and the hydraulic fluid in these zones is continually displaced at high speed, which can cause fluid friction and internal energy losses. According to another aspect of the invention the cylinder unit is formed with a smooth rounded external contour to reduce turbulence and encourage fluid flow around the unit.
The cylinder unit may have rounded corners, thus reducing "wetted surface" area and encouraging oil transfer, and conveniently the opposite axial end faces of the cylinder unit are at least partly inclined in relation to the end faces of the casing. Alternatively or in addition the cylinder unit or its casing may be formed with oil swirl grooves extending circumferentially around the axis to facilitate transfer of oil from one side of the axis to the other as the machine rotates.
Hydraulic machines are often included in complete hydraulic power transmissions, and it is important that the cost of the transmission system should be held to a minimum, but it is equally important that the system should have a satisfactory working life. These requirements conflict and it is an object of the invention to provide an effective solution or compromise.
Thus, according to a further aspect of the invention the cylinder unit includes a separately formed ported sleeve arranged to communicate with the ports on the pintle and with the cylinders of the rotary unit.
This affords the possibility of a large number of useful design features. By providing a separately formed ported sleeve, it is comparatively easy to design porting and fluid flow passages which will materially improve the performance. Also, the sleeve and the other components of the cylinder unit can be formed in specially selected materials and formed by selected procedures to establish long life, light weight, economy in cost, and other features.
One particular important feature is that the valve porting in the sleeve may include non-circular ports which are elongate and extended in a circumferential direction. This is a fundamentally novel approach. Conventionally the ports in the cylinder unit are circular and produced by drilling, but if the sleeve is formed separately the ports can be made elongate. It follows that for any particular port area a narrower longer port is possible Since the axi
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Arnold George D. M.
Thoma Christian H.
Croyle Carlton R.
Neils Paul F.
Unipat AG
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