US3699845A

US3699845A - Rotary hydraulic pumps and motors

Info

Publication number: US3699845A
Application number: US58059A
Authority: US
Inventors: Richard Joseph Ifield
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1970-07-24
Filing date: 1970-07-24
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

The port plate of a rotary hydraulic pump or motor has passages between one end of each port and the face of the plate against which the rotary cylinder block of the pump bears. One of the passages has a high resistance to flow from its associated port and the other passage has a high resistance to flow to its associated port. The passages permit a controlled flow between the ports and the pump cylinders prior to full communication therebetween.

Description

United States Patent [54] ROTARY HYDRAULIC PUMPS AND MOTORS [72] Inventor: Richard Joseph Ifield, Beecroft,

New South Wales, Australia [73] Assignee: Joseph Lucas (Industries) Limited,

Birmingham, England 22 Filed: July 24, 1970 21 Appl.N0.: 58,059

[22] Filed: July 24, 1970 [21] Appl. No.: 58,059

[52] U.S. Cl .9l/6.5, 91/499 [51] Int. Cl ..F0lb 13/04 [58] Field of Search ..9l/6.5; 417/312, 487, 499

[56] References Cited UNITED STATES PATENTS 6/1971 Moon ..91/6.5

1151 3,699,845 1451 Oct. 24, 1972 3,199,461 10/1965 Wolf ..91/6.s 2,944,529 7/1960 Wiggermann ..91/6.5 3,520,229 7/1970 Slimm et a] ..9l/6.5

FOREIGN PATENTS OR APPLICATIONS 16,620 12/1969 Japan ..417/312 Primary Examiner-William L. Freeh- Attorriey-Holman & Stern [57] ABSTRACT The port plate of a rotary hydraulic pump or motor has passages between one end of each port and the face of the plate against which the rotary cylinder block of the pump bears. One .of the passages has a high resistance to flow from its associated port and the other passage has a high resistance to flow to its associated port. The passages permit a controlled flow between the ports and the pump cylinders prior to full communication therebetween.

11 Claims, 12 Drawing Figures PATENTEDUBTZMHR 1 3.699.845

SHEET 2 OF 4 IVENTR ATTORNEYS PATENTEnncI 24 1972 3 6 99 845 sum 3 BF 4 I ATTORNEYS %M md gg pi/ ROTARY HYDRAULIC PUMPS AND MOTORS BACKGROUND OF THE INVENTION liquid flow from one port to the other accompanies rotation of the rotor.

PRIOR ART In pumps and motors of this kind, it is known to form notches in the port plate at the ends of the ports with which the passages first come into communication when the rotor is rotating in its normal direction of rotation. Various forms of notches have been suggested in the past but the most commonly used are notches of V-shaped section increasing in depth towards the associated ports. The purpose of these notches has been to avoid a rapid change in pressure in each passage as it comes into communication with a port. In fact, two effects are required. Firstly, in the case of the high pressure port of a pump, there must be flow from the port to the passage, to bring the passage pressure up to the level of the port pressure and there must then be flow from the passage to the port until the passage comes into full communication with the port to prevent the passage pressure rising substantially higher than the port pressure. If a shock wave is to be avoided, the first function should be carried out with a relatively highly restricted flow but the second function must be carried out with a relatively slightly restricted flow. Similar requirements apply to flow to and from the passages to the low pressure port, with restricted flow from the passage being followed by relatively unrestricted flow to the passage. With V-notches, the required conditions are not met since, in the case of the high pressure port, the area available'for flow from the port to the passage increases with the square of the angle of displacement of the rotor from the position in which the tip of the notch first comes into communication with the passage.

Fixed restrictors in the port plate have also been proposed but these do not provide the required difference in the restriction of flow in opposite directions.

It is thus an object of the invention to provide a pump or motor of the kind specified in which improved means are provided for permitting flow between the passages and the ports prior to full communication therebetween.

SUMMARY OF THE INVENTION According to the invention, in a machine of the kind specified, the port plate is formed with a pair of passages, the passages being associated with the ends of the respective ports, each passage connecting the end of the associated port with an opening in the face spaced from end of the port and each passage being of such hydrodynamic design that there is a greater resistance to flow in one direction than in the other direction, with one of the passages having a higher resistance to flow from its associated port than flow to the port and the other passage having a higher resistance to flow to its associated port than from the port.

In the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a section through one example of a pump in accordance with the invention,

FIG. 2 is a view of a port plate from the pump shown in FIG. 1,

FIGS. 3 and 4 are sections on lines 3-3 and 4-4 respectively in FIG. 2, and

FIGS. 5 and 6, 7 and 8, 9 and 10, and 11 and 12, are

sections, like FIGS. 3 and 4 but showing alternative forms of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring firstly to FIG. 1, the pump is of the swash plate type-and comprises a hollow housing 10 having an inlet ll and an outlet 12 at one end. The other end of the housing is closed by an end cover 13 in which is joumalleda shaft'l4. Connected to the shaft 14 and disposed inside the housing 10 is a rotor 15 in which are formed a plurality of angularly spaced bores 16 each containing a plunger 17 backed by a compression spring 18. The bores 16 terminate in passages 16a which open onto one end face of the rotor 15.

Each plunger 17 has a spherical end portion 19 having its end directed away from the opposite end face of the rotor 15 flattened. A bore 20 in each spherical end portion 19 opens into the interior of the plunger 17 at one end and onto the flattened face of the end portion 19 at the other end. The end portions 19 are respectively engaged in complementary sockets in slippers 21. Each slipper has a face which is formed with an hydrostatic bearing pocket 23 which communicates, via a bore 24 in the slipper, with the space within the slipper defined by the flattening of the associated end-portion 19.

The slippers 21 bear against an inclined swash plate 22 disposed adjacent the end cover 13. As the rotor is rotated, in use, the swash plate causes reciprocation of the plungers 19 in their respective bores 16.

' Interposed between said one end of the rotor and the end of the housing in which said inlet 11 and outlet 12 are formed is an annular port plate 25. This plate 25 is formed with two

arcuate ports

26, 27 through the intermediary of which liquid can pass between the inlet 11 and outlet 12 and the passages 16a in the rotor 15. The port 26 is in communication with the inlet 11, while the port 27 is in communication with the outlet 12.

As shown in FIG. 3, a passage is formed in the port plate at one end of the low pressure port 26. This passage is formed by a sharp-edged drilling 28 in the face of the port plate at a position spaced from the end of the port, and a streamlined profiled bore 29 in the wall of the port and communicating with the drilling 28. A passage of this nature has a higher resistance to flow to the port than to flow from the port, since in the first direction liquid must enter the passage through what is effectively a sharp-edged orifice, whereas liquid flowing in the-opposite direction will enter through a streamlined orifice. A flow number ratio of about 2:1 can be achieved with this configuration.

A similar passage is formed at the end of the high pressure port 27. As shown in FIG. 4, however a sharpedged drilling 30 opens into the port wall, whereas a streamlined profiled bore 31 opens onto the port plate face.

The arrangement shown in FIGS. and 6 utilizes the same principle as that illustrated in FIGS. 3 to 4 except that the passages are replaced by grooves in the port plate face which grooves form passages when the port plate face lies against theend face of the rotor. The passage in the case of the low pressure port is formed by a relatively large diameter recess 32 spaced from the end of the port and a groove 33 of semi-circular section opens into the port to provide a streamline entry 33a but opening into the recess 32 to provide a sharp-edged entry 33b. In the case of the high pressure port, groove 34 has a sharp-edged entry into the port and astrearnlined entry into recess 35.

In the example shown in FIGS. 7 and 8, a slightly different principle of operation is employed. In this case, each port has a passage converging from each end to a throat intermediate the ends, the throat being closer to one end of the passage than the other. Thus, when liquid flows from said one end to the other there is a recovery of the pressure in the passage before discharge. No recovery of pressure before discharge is possible when the flow direction is reversed, so that, for a given flow rate, there will be a smaller pressure drop for flow in said one direction than for flow in said other direction.

In the case of the low pressure port (FIG. 7), a throat 36a is closer to the end of a passage 36 opening into the port. In the case of the high pressure port a throat 37a is closer to the end of a passage 37 which opens onto the port plate face.

In FIGS. 9 and 10,

grooves

38, 39 connecting recesses 40,41 in the port plate face to the respective ports replace the passages 36, 37 of FIGS. 7 and 8.

Turning finally to FIGS. 11 and 12,

passages

42, 43 each include a

cylindrical chamber

44, 45. One branch 42a 43a of the passage has a sharp-edged entry and opens tangentially into the chamberIThe other branch 42b, 43b of the passage has a streamlined profiled entry and opens into the center of the associated chamber. The swirling motion which is set up in the chamber when liquid is caused to flow from the

passage

42a or 43a causes the resistance to flow in this direction to be increased considerably. No corresponding increase occurs when liquid is caused to flow in the opposite direction.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A rotary hydraulic machine comprising a housing, a rotor within the housing, a port plate in the housing, against a face of which plate one axial end of the rotor bears, a pair of ports in the plate, bores in the rotor which communicate with the ports alternately as the rotor is rotated, liquid displacing means associated with the rotor whereby liquid flow from one port to the other accompanies rotation of the rotor, and a pair of passages for liquid in the port plate, the passages being associated with the ends of the respective ports, each passage connecting the end of the associated port with an opening in the face spaced from end of the port and each passage including hydro-dynamically asymmetrical surfaces providing a greater resistance to flow in one direction than in the other direction, one of the passages having a higher resistance to flow from its associated port thanflow to the associated port and the other passage having a higher resistance to flow to its associated port than from the associated port.

2. The machine as claimed in claim 1 in which said one passage and said other passage are associated with the ports which respectively form, in use, a high pressure and a low pressure port.

3. The machine as claimed in claim 2 in which the passage associated with the low pressure port includes a substantially cylindrical bore communicating with said opening.

4. The machine as claimed in claim 3 in which the passage associated with the low pressure port includes a streamlined profiled bore between the cylindrical bore and the port, said streamlined bore having a sharp-edged entry into the cylindrical bore and a streamlined entry into the port.

5. The machine as claimed in claim 3 in which the passage associated with the low pressure port includes a groove in said face of .the port between the cylindrical bore and the port, said groove co-operating with said axial end of the rotor to define a part of the passage and having a sharp-edged entry into the cylindrical bore and a streamlined entry into the port.

6. The machine-as claimed in claim 2 in which the passage associated with the low pressure port comprises a streamlined bore formed with a throat adjacent the end of the passage which opens into the port.

7. The machine as claimed in claim 4 in which said opening communicates with thecylindrical bore via a branch which enters said bore tangentially.

8. The machine as claimed in claim 2 in which the passage associated with the high pressure port includes a substantially cylindrical bore communicating with the port and a streamlined profiled bore between the cylindrical bore and said opening.

9. The machine as claimed in claim 8 in which the cylindrical bore communicates with the high pressure port via a branch which 'enters the cylindrical bore tangentially.

10. A rotary hydraulic machine comprising, a rotor within the housing, a port plate in the housing, against a face of which plate one axial end of the rotor bears, a pair of ports in the plate, bores in the rotor which communicate with the ports alternately as the rotor is rotated, liquid displacing means associated with the rotor whereby liquid flow from one port to the other accompanies rotation of the rotor, and a pair of passages for liquid in the port plate, the passages being associated with the ends of the respective ports, each passage connecting the end of the associated port with an opening in the face spaced from the end of the port and each passage being of hydro-dynamically asymmetrical design so that there is a greater resistance to flow in one direction than in the other direction, one of the passages having a higher resistance to flow from its associated port than flow to the port and the other passage having a higher resistance to flow to its associated port than from the port, said one passage and said other passage being associated with the ports which respectively form, in use, a high pressure and a low pressure port, the passage associated with the high pressure port including a substantially cylindrical bore communicating with said opening and a groove in said face of the port plate between the cylindrical bore and the port, said groove co-operating with said axial end of the rotor to define a part of the passage and having a sharp-edged entry into the port and a streamlined entry into the cylindrical bore.

11. A rotary hydraulic machine comprising, a rotor within the housing, a port plate in the housing, against a face of which plate one axial end of the rotor bears, a pair of ports in the plate, bores in the rotor which communicate with the ports alternately as the rotor is rotated, liquid displacing means associated with the rotor whereby liquid flow from one port to the other accompanies rotation of the rotor, and a pair of passages for liquid in the port plate, the passages being associated with the ends of the respective ports, each passage connecting the end of the associated port with an opening in the face spaced from the end of the port and each passage being of hydro-dynamically asymmetrical design so that there is a greater resistance to flow in one direction than in the other direction, one of the passages having a higher resistance to flow from its associated port than flow to the port and the other passage having a higher resistance to flow to its associated port than from the port, said one passage and said other passage being associated with the ports which respectively form, in use a high pressure and a low pressure port, the high pressure port comprising a streamlined bore formed with a throat adjacent an end of the passage which forms said opening in the face of the port plate.

Claims

1. A rotary hydraulic machine comprising a housing, a rotor within the housing, a port plate in the housing, against a face of which plate one axial end of the rotor bears, a pair of ports in the plate, bores in the rotor which communicate with the ports alternately as the rotor is rotated, liquid displacing means associated with the rotor whereby liquid flow from one port to the other accompanies rotation of the rotor, and a pair of passages for liquid in the port plate, the passages being associated with the ends of the respective ports, each passage connecting the end of the associated port with an opening in the face spaced from end of the port and each passage including hydro-dynamically asymmetrical surfaces providing a greater resistance to flow in one direction than in the other direction, one of the passages having a higher resistance to flow from its associated port than flow to the associated port and the other passage having a higher resistance to flow to its associated port than from the associated port.

5. The machine as claimed in claim 3 in which the passage associated with the low pressure port includes a groove in said face of the port between the cylindrical bore and the port, said groove co-operating with said axial end of the rotor to define a part of the pAssage and having a sharp-edged entry into the cylindrical bore and a streamlined entry into the port.

6. The machine as claimed in claim 2 in which the passage associated with the low pressure port comprises a streamlined bore formed with a throat adjacent the end of the passage which opens into the port.

7. The machine as claimed in claim 4 in which said opening communicates with the cylindrical bore via a branch which enters said bore tangentially.

9. The machine as claimed in claim 8 in which the cylindrical bore communicates with the high pressure port via a branch which enters the cylindrical bore tangentially.