CONTROL FACE ARRANGEMENT FOR AN AXIAL PISTON MACHINE
United States Patent 3851669
An axial piston machine, such as a pump or hydraulic motor, has a stationary control face provided with inlet and outlet ports, and a rotary control face provided with cylinder ports. Sealing face portions radial inward and outward of the ports, and separating face portions between the ends of the ports, are worn off by particles entrained in the flow through the ports. A peripheral support rim on one of the control faces would be less worn, but is made so narrow in radial direction that no pressure field can form thereon, and friction wears off the support rim to the same degree as the sealing and separating face portions. The radial width of the support rim is preferably less than 2.5% of its outer diameter.
US Patent References:
Hydraulic pumps and motors
Jonkers et al. - February 1966 - 3232239
Axial piston pump or motor arrangement
Bosch - December 1966 - 3289606
DISTRIBUTOR FOR HYDRAULIC MOTORS
Ortelli - October 1972 - 3696710
HIGH-PRESSURE MULTI-CYLINDER HYDRAULIC MACHINES
Pruvot - November 1972 - 3702576
HYDROSTATICALLY BALANCED PLATE VALVE WITH LOW FLOW RESISTANCE
Friedrichs - December 1972 - 3707169
Hydraulic pumps and motors
Jonkers et al. - February 1966 - 3232239
Axial piston pump or motor arrangement
Bosch - December 1966 - 3289606
DISTRIBUTOR FOR HYDRAULIC MOTORS
Ortelli - October 1972 - 3696710
HIGH-PRESSURE MULTI-CYLINDER HYDRAULIC MACHINES
Pruvot - November 1972 - 3702576
HYDROSTATICALLY BALANCED PLATE VALVE WITH LOW FLOW RESISTANCE
Friedrichs - December 1972 - 3707169
Inventors:
Zellbeck, Gustav (Esslingen-Hegensberg, DT)
Bertsch, Dieter (Stuttgart-Mohringen, DT)
Hofsass, Dieter (Fellbach, DT)
Bertsch, Dieter (Stuttgart-Mohringen, DT)
Hofsass, Dieter (Fellbach, DT)
Application Number:
05/324895
Publication Date:
12/03/1974
Filing Date:
01/18/1973
View Patent Images:
Export Citation:
Assignee:
Robert Bosch GmbH (Stuttgart, DT)
Primary Class:
Other Classes:
91/487
International Classes:
F04B1/20; F01B13/04; F01B1/00
Field of Search:
137/625.21 91/487,485,472,180 251/281,283,368
Primary Examiner:
Cline, William R.
Assistant Examiner:
Miller, Robert J.
Attorney, Agent or Firm:
Striker, Michael S.
Claims:
We claim
1. Control face arrangement for an axial piston machine with suppression of unequal wear of the support rim relative to the sealing face portions, comprising housing means including a first control face; and cylinder body means having a second control face cooperating with said first control face, one of said means being rotary relative to the other means together with the respective control face; said first control face being formed with a pair of part-circular inlet and outlet ports, and having first separating face portions between the ends of said inlet and outlet ports and first outer and inner annular sealing face portions radially outward and inward of said inlet and outlet ports and subjected to wear by particles flowing with fluid through said inlet and outlet ports; said second control face being formed with a plurality of cylinder ports, and having second separating face portions between the ends of said cylinder ports and subjected to wear by said particles; at least one of said first and second control faces having circular axially projecting peripheral support rim means abutting the respective other control face and exteriorly bounding an annular groove and being of a narrow radial width between 0.5% and 2.5% of the outer diameter of said support rim means and operative to suppress the formation of a hydrodynamic pressure field between said support rim means and the corresponding circular peripheral face portion of the respective other control face, whereby due to the suppression of the hydrodynamic pressure field between said support rim means and said corresponding peripheral face portion the rate of wear of said support rim means is substantially equal to the rate of wear of said sealing face portions which is caused by said particles.
2. Control face arrangement as claimed in claim 1, wherein said cylinder body forms a space in said housing means; and wherein said annular groove in said one control face communicates with said space.
3. Control face arrangement as claimed in claim 2, wherein said one control face is said second control face; and wherein said cylinder body means is formed with a channel connecting said annular groove with said space.
4. Control face arrangement as claimed in claim 1 wherein the surface area of all said first separating face portions is not more than one quarter of the surface area of said first annular sealing face portions.
5. Control face arrangement as claimed in claim 1, wherein said second control face has second outer and inner annular sealing face portions radially outward and inward of said cylinder ports.
6. Control face arrangement as claimed in claim 1, wherein the surface area of all said second separating face portions is not more than one quarter of the surface area of said second annular sealing face portions.
7. Control face arrangement as claimed in claim 1, wherein one of said housing and cylinder body means is made of a material having higher thermal conductivity than the respective other means; and wherein said one control face is provided on said one means.
8. Control face arrangement as claimed in claim 1, wherein said housing means is stationary and said cylinder body means is rotary and mounted for rotation in said housing means.
9. Control face arrangement as claimed in claim 8, wherein said one control face is said first control face and is stationary.
10. Control face arrangement as claimed in claim 8, wherein said one control face is said second control face and is rotary.
1. Control face arrangement for an axial piston machine with suppression of unequal wear of the support rim relative to the sealing face portions, comprising housing means including a first control face; and cylinder body means having a second control face cooperating with said first control face, one of said means being rotary relative to the other means together with the respective control face; said first control face being formed with a pair of part-circular inlet and outlet ports, and having first separating face portions between the ends of said inlet and outlet ports and first outer and inner annular sealing face portions radially outward and inward of said inlet and outlet ports and subjected to wear by particles flowing with fluid through said inlet and outlet ports; said second control face being formed with a plurality of cylinder ports, and having second separating face portions between the ends of said cylinder ports and subjected to wear by said particles; at least one of said first and second control faces having circular axially projecting peripheral support rim means abutting the respective other control face and exteriorly bounding an annular groove and being of a narrow radial width between 0.5% and 2.5% of the outer diameter of said support rim means and operative to suppress the formation of a hydrodynamic pressure field between said support rim means and the corresponding circular peripheral face portion of the respective other control face, whereby due to the suppression of the hydrodynamic pressure field between said support rim means and said corresponding peripheral face portion the rate of wear of said support rim means is substantially equal to the rate of wear of said sealing face portions which is caused by said particles.
2. Control face arrangement as claimed in claim 1, wherein said cylinder body forms a space in said housing means; and wherein said annular groove in said one control face communicates with said space.
3. Control face arrangement as claimed in claim 2, wherein said one control face is said second control face; and wherein said cylinder body means is formed with a channel connecting said annular groove with said space.
4. Control face arrangement as claimed in claim 1 wherein the surface area of all said first separating face portions is not more than one quarter of the surface area of said first annular sealing face portions.
5. Control face arrangement as claimed in claim 1, wherein said second control face has second outer and inner annular sealing face portions radially outward and inward of said cylinder ports.
6. Control face arrangement as claimed in claim 1, wherein the surface area of all said second separating face portions is not more than one quarter of the surface area of said second annular sealing face portions.
7. Control face arrangement as claimed in claim 1, wherein one of said housing and cylinder body means is made of a material having higher thermal conductivity than the respective other means; and wherein said one control face is provided on said one means.
8. Control face arrangement as claimed in claim 1, wherein said housing means is stationary and said cylinder body means is rotary and mounted for rotation in said housing means.
9. Control face arrangement as claimed in claim 8, wherein said one control face is said first control face and is stationary.
10. Control face arrangement as claimed in claim 8, wherein said one control face is said second control face and is rotary.
Description:
BACKGROUND OF THE INVENTION
The present invention is concerned with axial piston machines, pumps or motors with a rotary cylinder body in whose cylinder bores, axially movable pistons are located. The cylinder body has a control face with cylinder ports, cooperating with a stationary control face on the housing provided with part-circular inlet and outlet ports.
In axial piston pumps of this type, it is difficult to hold leakage losses low, particularly if the machine is operated at high pressures up to 300 atm. Impurities and foreign particles contained in the pressure fluid, enter the gap between the rotary control face and the stationary control face, and cause great wear particularly in face portions adjacent the inlet and outlet control ports. When a peripheral support rim is provided, it is subjected to less wear due to its greater radial distance from the control ports. Consequently, the control faces are worn unevenly, increasing leakage losses, which may result in failure of the pump.
The U.S. Pat. 3,051,093 discloses an axial piston machine in which a divided peripheral support rim is provided. Since the portions of the support rim are slide bearings, the wear thereon is less than on the sealing face portions adjacent the control ports, irrespective of the low pressure of the hydrodynamic pressure field formed thereon. Since the portions of the supporting rim are cooled by the leakage flow, but not in the center, thermal expansion becomes greater, and increased pressure in this region may cause damage.
SUMMARY OF THE INVENTION
It is one object of the invention to provide an axial piston machine which during its entire span of life, has small leakage losses and is consequently very reliable.
Another object of the invention is to uniformly wear off all face portions of a control face which cooperates with another control face.
With these objects in view, the present invention provides a peripheral support rim on at least one of the control faces, whose radial width is so small, that no hydrodynamic pressure field can be developed thereon when the cylinder body rotates. In accordance with the invention, the narrow peripheral rim can be provided either on the stationary control face, or on the rotary control face of an axial piston machine.
The arrangement of the invention has the advantage that the supporting function of the peripheral support rim is maintained, but its wear corresponds substantially to the wear on the sealing face portions of the respective control faces.
In the preferred embodiment of the invention the radial width of the support rim is less than 2.5%, and preferably at least 0.5% of the outer diameter of the support rim.
It is advantageous if the surface area of all separating face portions between the ends of the control ports is not more than one-quarter of the surface area of the respective annular sealing face portions inward and outward of the control ports.
When the control faces are accordingly constructed, the lubricating clearance between the control faces is substantially constant, and all sliding faces are uniformly worn. In this manner, the object of the invention, a constant low leakage loss, is obtained.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an axial sectional view illustrating an axial piston pump;
FIG. 2 is an end view taken in the direction of the arrow II in FIG. 1, and illustrating a stationary control face; and
FIG. 3 is an end view taken in the direction of the arrow III, and illustrating the rotary control face of the cylinder body of a modified embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The axial piston pump shown in FIG. 1, has a housing 1 closed by a cover 2. A shaft 3 is mounted in the cover 2 and in the end wall 4 of the housing 1, and connected by annular key means 5 with the rotary cylinder body 6. Shaft 3 has a stepped portion on which one end of a spring 7 abuts, the other end of spring 7 abutting a ring 7a inserted into a recess in the inner bore of the cylinder body 6. Spring 7 biasses the rotary control face 6a of the cylinder body 6 into sliding contact with the stationary control face 8 of a non-rotatable control valve body 9, which abuts the end wall 4 of the housing, and may be made integral therewith. Cylinder bores 10 are provided in the cylinder body 6 along a circle concentric with the axis of shaft 3, and contain pistons 13 with slide shoes 11 abutting a wobble plate 12 whose slant causes reciprocation of the pistons 13, 11 during rotation of the cylinder body 6. The cylinder bores 10 have cylinder ports 14 which cooperate with the part-circular inlet and outlet ports 17 and 18 in the control valve plate 8. Inlet and outlet means 19, 20 for the supply and discharge of the fluid, open into the part-circular inlet and outlet slots 17 and 18.
The stationary control face 8 has an outer sealing face portion 22 and an inner sealing face portion 21 on opposite sides of the inlet and outlet ports 17 and 18. The outer annular sealing face portion 22 is separated by an annular and circular groove 23 from a circular peripheral support rim 24. The abutment faces of the sealing face portions 21, 22 and of the support rim 24 are located in a common plane perpendicular to the axis of shaft 3.
As best seen in FIG. 1, a connecting channel or duct 25 is formed in the cylinder body 6 and connects the annular groove 23 with a space formed in housing 1 between the housing walls and the cylinder body 6. FIG. 1 shows channel 25 to open in the outer surface of cylinder body 6.
As shown in FIG. 2, between the ends of the part-circular inlet and outlet ports 17 and 18, and also between the annular sealing face portions 21 and 22, separating face portions 15 and 16 are located.
During rotation of the cylinder body 6, the pistons 13 reciprocate, and suck fluid from one of the inlet and outlet ports 17, 18 into the respective cylinder bores 10, and discharge the fluid from the respective other cylinder bores 10. Between the stationary control face 8 and the rotary control face 6a of the cylinder body 6, a lubricating gap is formed, which permits flow of pumped fluid from the inlet and outlet ports 17, 18 to the groove 23, from where the fluid leaks through the channel 25 into the interior of housing 1.
Impurities and foreign particles contained in the pressure fluid, also enter the gap or clearance between the control face 6a of the cylinder body 5 and the control face 8 of the stationary valve plate 9. The foreign particles cause wear particularly on the sealing face portions 21, 22 and separating face portions 15 and 16 which bound the inlet and outlet ports 17 and 18.
The wear of the inner face portions 15, 16, 21, 22 near the center of the control face 8 is greater than in the peripheral region of the control face 8 where the narrow support rim 24 cooperates with the corresponding face portion of the rotary control face 6a.
In accordance with the invention, the radial width of the support rim 24 is made so small that, irrespective of the friction acting thereon, the generation of heat is so low that there is no tendency to binding. The composite friction acting on the support rim 24, together with the effect of the foreign particles in the fluid, have the effect that the wear of the support rim is substantially the same as the wear at the sealing face portions 21 and 22. The total surface of the separating face portions 15, 16 between the ends of the inlet and outlet ports 17, 18 is selected to be small, and not more than one-quarter of the surface area of the sealing face portions 21, 22. The wear on the separating face portions 15, 16, caused by impurities of the fluid, corresponds substantially to the wear of the sealing face portions 21, 22. The radial width of the support rim 24 is made so small, namely less than 2.5% of its outer diameter, that in all operational conditions, no hydrodynamic pressure field forms between the support rim 24 and the corresponding peripheral face portion of the rotary control face 6a. Preferably, the width of support rim 24 is more than 0.5% of the outer diameter of support rim 25.
FIG. 1 illustrates an axial piston pump in which the control face 8 is constructed in accordance with the invention, as shown and described with reference to FIG. 2. However, in a modified embodiment, the control face of the control body 6 is provided with the peripheral support rim 38, as shown in FIG. 3 in which the rotary control face 31 is shown which could be provided instead of the rotary control face 6a of the embodiment of FIGS. 1 and 2. Under some circumstances, it may be desirable to construct the stationary and rotary control faces with peripheral support rims which in accordance with the invention are very narrow in radial direction. Referring now to the modification illustrated in FIG. 3, the cylinder body 30 has a rotary control face 31 provided with cylinder ports 32a to 32g which communicate with the cylinder bores 33a to 33g, are separated by separating face portions 34a to 34g, and are bounded by inner and outer annular sealing face portions 35, 36. A circular groove 37 is formed between a circular endless peripheral support rim 38 and the outer sealing face portion 36. A bore or channel 39 connects the groove 37 with the outer surface of the cylinder body 30 so that the groove 37 communicates with the interior of housing 1.
The radial width of the support rim 38 of the modification of FIG. 3 is small, and between 0.5% and 2.5% of the outer diameter thereof. The surface area of the separating face portions 34a to 34g between the cylinder ports and the annular inner and outer sealing face portions, is also small and maximal one-quarter of the surface area of the annular sealing face portions 35, 36.
Assuming that the control face 31 cooperates with a stationary control face without support rim 24 and sealing face portions 21, 22, the support rim 38 is worn to the same degree as the separating face portions 34a to 34g and the annular sealing face portions 35 and 36 corresponding to the wear of the stationary control face 8 in the embodiment of FIGS. 1 and 2.
Either the control face as shown in FIG. 2 is provided as a stationary control face, or the control face shown in FIG. 3 is provided as a rotary control face.
In a preferred embodiment of the invention, the thermal conductivity of the housing means and cylinder body means 6 is different, and the support rim 24 or 38 is provided on the control face of the means which has the higher thermal conductivity.
From the above description of preferred embodiments of the invention, it will become apparent that a control face arrangement according to the invention comprises housing means 1 including a first control face 8; and cylinder body means 6 having a second control face 6a or 31 cooperating with the first control face 8, one of said means 6 being rotary relative to the other means 1 together with the respective control face 6a or 31; the first control face 8 being formed with a pair of part-circular inlet and outlet ports 17, 18, and having first separating face portions 15, 16 between the ends of the inlet and outlet ports 17, 18 and first outer and inner annular sealing face portions 22, 21 radially outward and inward of the inlet and outlet ports 17, 18 and subjected to wear by particles flowing with fluid through the inlet and outlet ports 17, 18;
the second control face 6a or 31 being formed with a plurality of cylinder ports, and having second separating face portions 34a between the ends of the cylinder ports 32a, 32b and in a preferred embodiment with second outer and inner annular sealing face portions 36, 35 radially outward and inward of the cylinder ports 32a and subjected to wear by the particles;
at least one of the first and second control faces 8, 31 having a circular peripheral narrow support rim 24, 38 abutting the respective other control face 31, 8 and forming with the respective outer sealing face portion 22, 36 an annular groove 23, 37;
the radial width of the support rim 24, 38 being selected so that no hydrodynamic pressure field forms between the support rim and the corresponding circular peripheral face portion of the respective other control face.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of control face arrangements for axial piston machines differing from the types described above.
While the invention has been illustrated and described as embodied in a control face provided with a peripheral support rim which is narrow in radial direction so as to be worn off to the same degree as sealing face portions of the control face, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.
The present invention is concerned with axial piston machines, pumps or motors with a rotary cylinder body in whose cylinder bores, axially movable pistons are located. The cylinder body has a control face with cylinder ports, cooperating with a stationary control face on the housing provided with part-circular inlet and outlet ports.
In axial piston pumps of this type, it is difficult to hold leakage losses low, particularly if the machine is operated at high pressures up to 300 atm. Impurities and foreign particles contained in the pressure fluid, enter the gap between the rotary control face and the stationary control face, and cause great wear particularly in face portions adjacent the inlet and outlet control ports. When a peripheral support rim is provided, it is subjected to less wear due to its greater radial distance from the control ports. Consequently, the control faces are worn unevenly, increasing leakage losses, which may result in failure of the pump.
The U.S. Pat. 3,051,093 discloses an axial piston machine in which a divided peripheral support rim is provided. Since the portions of the support rim are slide bearings, the wear thereon is less than on the sealing face portions adjacent the control ports, irrespective of the low pressure of the hydrodynamic pressure field formed thereon. Since the portions of the supporting rim are cooled by the leakage flow, but not in the center, thermal expansion becomes greater, and increased pressure in this region may cause damage.
SUMMARY OF THE INVENTION
It is one object of the invention to provide an axial piston machine which during its entire span of life, has small leakage losses and is consequently very reliable.
Another object of the invention is to uniformly wear off all face portions of a control face which cooperates with another control face.
With these objects in view, the present invention provides a peripheral support rim on at least one of the control faces, whose radial width is so small, that no hydrodynamic pressure field can be developed thereon when the cylinder body rotates. In accordance with the invention, the narrow peripheral rim can be provided either on the stationary control face, or on the rotary control face of an axial piston machine.
The arrangement of the invention has the advantage that the supporting function of the peripheral support rim is maintained, but its wear corresponds substantially to the wear on the sealing face portions of the respective control faces.
In the preferred embodiment of the invention the radial width of the support rim is less than 2.5%, and preferably at least 0.5% of the outer diameter of the support rim.
It is advantageous if the surface area of all separating face portions between the ends of the control ports is not more than one-quarter of the surface area of the respective annular sealing face portions inward and outward of the control ports.
When the control faces are accordingly constructed, the lubricating clearance between the control faces is substantially constant, and all sliding faces are uniformly worn. In this manner, the object of the invention, a constant low leakage loss, is obtained.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an axial sectional view illustrating an axial piston pump;
FIG. 2 is an end view taken in the direction of the arrow II in FIG. 1, and illustrating a stationary control face; and
FIG. 3 is an end view taken in the direction of the arrow III, and illustrating the rotary control face of the cylinder body of a modified embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The axial piston pump shown in FIG. 1, has a housing 1 closed by a cover 2. A shaft 3 is mounted in the cover 2 and in the end wall 4 of the housing 1, and connected by annular key means 5 with the rotary cylinder body 6. Shaft 3 has a stepped portion on which one end of a spring 7 abuts, the other end of spring 7 abutting a ring 7a inserted into a recess in the inner bore of the cylinder body 6. Spring 7 biasses the rotary control face 6a of the cylinder body 6 into sliding contact with the stationary control face 8 of a non-rotatable control valve body 9, which abuts the end wall 4 of the housing, and may be made integral therewith. Cylinder bores 10 are provided in the cylinder body 6 along a circle concentric with the axis of shaft 3, and contain pistons 13 with slide shoes 11 abutting a wobble plate 12 whose slant causes reciprocation of the pistons 13, 11 during rotation of the cylinder body 6. The cylinder bores 10 have cylinder ports 14 which cooperate with the part-circular inlet and outlet ports 17 and 18 in the control valve plate 8. Inlet and outlet means 19, 20 for the supply and discharge of the fluid, open into the part-circular inlet and outlet slots 17 and 18.
The stationary control face 8 has an outer sealing face portion 22 and an inner sealing face portion 21 on opposite sides of the inlet and outlet ports 17 and 18. The outer annular sealing face portion 22 is separated by an annular and circular groove 23 from a circular peripheral support rim 24. The abutment faces of the sealing face portions 21, 22 and of the support rim 24 are located in a common plane perpendicular to the axis of shaft 3.
As best seen in FIG. 1, a connecting channel or duct 25 is formed in the cylinder body 6 and connects the annular groove 23 with a space formed in housing 1 between the housing walls and the cylinder body 6. FIG. 1 shows channel 25 to open in the outer surface of cylinder body 6.
As shown in FIG. 2, between the ends of the part-circular inlet and outlet ports 17 and 18, and also between the annular sealing face portions 21 and 22, separating face portions 15 and 16 are located.
During rotation of the cylinder body 6, the pistons 13 reciprocate, and suck fluid from one of the inlet and outlet ports 17, 18 into the respective cylinder bores 10, and discharge the fluid from the respective other cylinder bores 10. Between the stationary control face 8 and the rotary control face 6a of the cylinder body 6, a lubricating gap is formed, which permits flow of pumped fluid from the inlet and outlet ports 17, 18 to the groove 23, from where the fluid leaks through the channel 25 into the interior of housing 1.
Impurities and foreign particles contained in the pressure fluid, also enter the gap or clearance between the control face 6a of the cylinder body 5 and the control face 8 of the stationary valve plate 9. The foreign particles cause wear particularly on the sealing face portions 21, 22 and separating face portions 15 and 16 which bound the inlet and outlet ports 17 and 18.
The wear of the inner face portions 15, 16, 21, 22 near the center of the control face 8 is greater than in the peripheral region of the control face 8 where the narrow support rim 24 cooperates with the corresponding face portion of the rotary control face 6a.
In accordance with the invention, the radial width of the support rim 24 is made so small that, irrespective of the friction acting thereon, the generation of heat is so low that there is no tendency to binding. The composite friction acting on the support rim 24, together with the effect of the foreign particles in the fluid, have the effect that the wear of the support rim is substantially the same as the wear at the sealing face portions 21 and 22. The total surface of the separating face portions 15, 16 between the ends of the inlet and outlet ports 17, 18 is selected to be small, and not more than one-quarter of the surface area of the sealing face portions 21, 22. The wear on the separating face portions 15, 16, caused by impurities of the fluid, corresponds substantially to the wear of the sealing face portions 21, 22. The radial width of the support rim 24 is made so small, namely less than 2.5% of its outer diameter, that in all operational conditions, no hydrodynamic pressure field forms between the support rim 24 and the corresponding peripheral face portion of the rotary control face 6a. Preferably, the width of support rim 24 is more than 0.5% of the outer diameter of support rim 25.
FIG. 1 illustrates an axial piston pump in which the control face 8 is constructed in accordance with the invention, as shown and described with reference to FIG. 2. However, in a modified embodiment, the control face of the control body 6 is provided with the peripheral support rim 38, as shown in FIG. 3 in which the rotary control face 31 is shown which could be provided instead of the rotary control face 6a of the embodiment of FIGS. 1 and 2. Under some circumstances, it may be desirable to construct the stationary and rotary control faces with peripheral support rims which in accordance with the invention are very narrow in radial direction. Referring now to the modification illustrated in FIG. 3, the cylinder body 30 has a rotary control face 31 provided with cylinder ports 32a to 32g which communicate with the cylinder bores 33a to 33g, are separated by separating face portions 34a to 34g, and are bounded by inner and outer annular sealing face portions 35, 36. A circular groove 37 is formed between a circular endless peripheral support rim 38 and the outer sealing face portion 36. A bore or channel 39 connects the groove 37 with the outer surface of the cylinder body 30 so that the groove 37 communicates with the interior of housing 1.
The radial width of the support rim 38 of the modification of FIG. 3 is small, and between 0.5% and 2.5% of the outer diameter thereof. The surface area of the separating face portions 34a to 34g between the cylinder ports and the annular inner and outer sealing face portions, is also small and maximal one-quarter of the surface area of the annular sealing face portions 35, 36.
Assuming that the control face 31 cooperates with a stationary control face without support rim 24 and sealing face portions 21, 22, the support rim 38 is worn to the same degree as the separating face portions 34a to 34g and the annular sealing face portions 35 and 36 corresponding to the wear of the stationary control face 8 in the embodiment of FIGS. 1 and 2.
Either the control face as shown in FIG. 2 is provided as a stationary control face, or the control face shown in FIG. 3 is provided as a rotary control face.
In a preferred embodiment of the invention, the thermal conductivity of the housing means and cylinder body means 6 is different, and the support rim 24 or 38 is provided on the control face of the means which has the higher thermal conductivity.
From the above description of preferred embodiments of the invention, it will become apparent that a control face arrangement according to the invention comprises housing means 1 including a first control face 8; and cylinder body means 6 having a second control face 6a or 31 cooperating with the first control face 8, one of said means 6 being rotary relative to the other means 1 together with the respective control face 6a or 31; the first control face 8 being formed with a pair of part-circular inlet and outlet ports 17, 18, and having first separating face portions 15, 16 between the ends of the inlet and outlet ports 17, 18 and first outer and inner annular sealing face portions 22, 21 radially outward and inward of the inlet and outlet ports 17, 18 and subjected to wear by particles flowing with fluid through the inlet and outlet ports 17, 18;
the second control face 6a or 31 being formed with a plurality of cylinder ports, and having second separating face portions 34a between the ends of the cylinder ports 32a, 32b and in a preferred embodiment with second outer and inner annular sealing face portions 36, 35 radially outward and inward of the cylinder ports 32a and subjected to wear by the particles;
at least one of the first and second control faces 8, 31 having a circular peripheral narrow support rim 24, 38 abutting the respective other control face 31, 8 and forming with the respective outer sealing face portion 22, 36 an annular groove 23, 37;
the radial width of the support rim 24, 38 being selected so that no hydrodynamic pressure field forms between the support rim and the corresponding circular peripheral face portion of the respective other control face.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of control face arrangements for axial piston machines differing from the types described above.
While the invention has been illustrated and described as embodied in a control face provided with a peripheral support rim which is narrow in radial direction so as to be worn off to the same degree as sealing face portions of the control face, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.