Rotor with a hydraulic overbalancing recess

CROSS-REFERENCE TO RELATED CASES

The present application claims the benefit of the filing date of U. S. Provisional Application Ser. No. 60/410,739 filed Sep. 13, 2002, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a rotary fluid pressure device wherein high pressure fluid is routed from an inlet port through the rotary fluid pressure device to a recess in an externally toothed rotor member in order to overbalance the rotor towards a manifold assembly in order to minimize the leakage of fluid with the rotary fluid pressure device.

BACKGROUND OF THE INVENTION

The use of rotary fluid pressure devices for motors and pumps is well known in the art. One type of rotary fluid pressure devices is generally referred to as gerotors, gerotor type motors, and gerotor type pumps, hereinafter referred to as gerotor motors. Gerotor motors are compact in size, low in manufacturing cost, have a high-torque capacity ideally suited for such applications as turf equipment, agriculture and forestry machinery, mining and construction equipment, as well as winches, etc. Gerotor motors have gerotor sets which have a special form of internal gear transmission consisting of two main elements: an inner rotor and an outer stator.

The inner rotor and the outer stator possess different centers. The inner rotor has a plurality of external teeth which contacts circular arcs on the interior of the outer stator when it revolves. An output shaft is either directly connected to the orbiting inner rotor or is connected thereto by a drive link splined at each end. When pressurized fluid flows into a motor, the resistance of an external torsional load on the motor begins to build differential pressure, which in turn causes the inner rotor to rotate in the desired direction via a timing valve.

Typically, due to the flow of high pressure fluid through the gerotor sets, namely into and out of the volume chambers in the gerotor set, the inner rotor tends to have an imbalance of forces acting upon it. This imbalance of forces will cause the rotor to tilt to one side during its rotation, resulting in unwanted wearing along the surface of the rotor that comes in contact with an adjacent component, e.g. an end cap. Prior art constructions, such as those set forth in U.S. Pat. No. 5,624,248 to Kassen et al. have used an adjacent component, such as a plate, in order to balance the rotor that has tipped in one direction. The plate has hydraulic forces acting on one side, causing it to flex and come in physical contact with the rotor. This contact offsets the differential of forces which tip the rotor, thus allowing the rotor to rotate uniformly. The gerotor set of the present invention uses pressurized fluid to balance the rotor without having an extra component that physically contacts the rotor.

Gerotor motors are commonly comprised of several aligned components for routing fluid for the purpose of supplying a driving force. The gerotor set has adjacent componentry which directs the pressurized fluid into and out of the rotor. A rotating balanced rotor will be spaced apart from the adjacent componentry, thus allowing gaps and cross-port leakage. One of the components typically adjacent to the gerotor set is a manifold assembly. The interface between the gerotor set and the manifold assembly is a common area for leakage due to the continuous valving of fluid that takes places in this location. Prior art constructions, such as that shown in U.S. Pat. No. 4,717,320 to White, Jr., supply a flexible balancing plate, on the opposite side of the gerotor set from the manifold assembly, for reducing the gap between the gerotor set and the manifold assembly. This prior art construction routes pressurized fluid to the backside of the flexible balancing plate in order to bow the balancing plate physically against the rotor and force the rotor against the manifold assembly. The present invention places a rigid, channeling plate on the opposite side of the gerotor set from the manifold assembly. The channeling plate directs pressurized fluid into a recess in the axial surface of the rotor and biases the rotor towards the manifold assembly. This reduces the gap between the gerotor set and the manifold assembly, thus minimizing the leakage at this interface.

SUMMARY OF THE PRESENT INVENTION

A feature of the present invention is to provide a rotary fluid pressure device comprised of a housing member, a manifold assembly, a gerotor set, a channeling plate, an end plate, and means for routing high pressure fluid from the housing member to the gerotor set. The housing member has a high pressure fluid inlet port, an exhaust fluid outlet port, a first flow passage and an internal bore. The manifold assembly has a first and second fluid passage, and an internal bore with one side of the manifold assembly adjoining the housing member. The gerotor set is positioned next to the manifold assembly and has an internally toothed stator member with at least one axial fluid path extending therethrough, and an externally toothed rotor member eccentrically disposed within the stator member having an internal bore, a first axial end surface, and a second axial end surface having a recess circumferentially surrounding the internal bore. The rotor member includes a plurality of axially extending through holes for fluid flow there through being adapted for hydraulically axially balancing the axial end surfaces of the rotor member relative to the stator member. The channeling plate is positioned between the end plate and the geroter set and has a first side, a second side, a first fluid passage extending therethrough, a second fluid passage extending therethrough, and a plurality of through holes. A cavity is located between the channeling plate and the end plate and receives high pressure fluid. The high pressure fluid routing means directs fluid from one of the housing member's first and second flow passages, through the at least one axial fluid path within the stator member, through the rotor member internal bore, through one of channeling plate's first and second fluid passages, into and subsequently out of the cavity, through the plurality of through holes in the channeling plate, and into the recess in the second axial end surface of the rotor. The high pressure fluid within the recess overbalances the previously axially balanced rotor axially towards the manifold assembly.

In the noted rotary fluid pressure device, the recess can be comprised of multiple convolutions, and the at least one of the plurality of through holes in the channeling plate is axially aligned at all time with the recess during each complete 360° hypocycloidal movement of the rotor. Further in the noted rotary fluid pressure device, the recess can be generally circular. Also in the noted rotary pressure device, the cavity can be located within and concentric with the channeling plate. Further, the cavity could be located within and concentric with the end plate.

Another feature of the noted rotary fluid pressure device includes having the first fluid passage of the manifold assembly being axially aligned with the at least one axial fluid path in the stator member. An additional feature of the noted rotary fluid pressure device includes having the second fluid passage of the manifold assembly being axially aligned with the internal bore of the rotor member.

A further feature of the noted rotary fluid pressure device has the means for routing of the high pressure fluid including a first check valve located with the channeling plate first fluid passage and a second check valve located within the channeling plate second fluid passage.

Another feature of the present invention includes a rotary fluid pressure device similar to the previously noted device wherein the housing member has a fluid inlet port and a first flow passage for receiving one of a high pressure fluid and an exhaust fluid, a fluid outlet port and second flow passage for receiving the other of the high pressure fluid and the exhaust fluid, and an internal bore for receiving one of the high pressure fluid and the exhaust fluid. The manifold assembly has a first fluid passage fluidly connected with the housing member first flow passage for receiving one of the high pressure fluid and the exhaust fluid, a second fluid passage fluidly connected with the housing member second flow passage for receiving the other of the high pressure fluid and the exhaust fluid, and an internal bore fluidly connected with the housing member internal bore for receiving one of the high pressure fluid and the exhaust fluid. The gerotor set has an internally toothed stator member with at least one axial fluid path extending therethrough fluidly connected with the manifold assembly first flow passage for receiving one of the high pressure fluid and the exhaust fluid, and an externally toothed rotor member hydraulically balanced relative to the stator, eccentrically disposed within the stator member, having an internal bore fluidly connected with the manifold assembly second fluid passage for receiving the other of the high pressure fluid and the exhaust fluid. The rotor member also including a first axial end surface, a second axial end surface including a recess circumferentially surrounding the internal bore for receiving the high pressure fluid, and a plurality of axially extending through holes for receiving one of the high pressure fluid and the exhaust fluid. The channeling plate being substantially rigid and having a first side, a second side, a first fluid passage fluidly connected with the stator member at least one axial fluid path. The first fluid passage extending through the channeling plate for receiving one of the high pressure fluid and the exhaust fluid. The channeling plate also including a second fluid passage, fluidly connected with the rotor internal bore, extending through the channeling plate for receiving the other of the high pressure fluid and the exhaust fluid, and a plurality of through holes fluidly connected with the rotor second axial end surface recess for receiving the high pressure fluid. The end plate has a first side adjacent the second side of the channeling plate. The cavity being fluidly connected with the plurality of through holes in the channeling plate, located between the channeling plate and the end plate for receiving the high pressure fluid from one of either the channeling plate first and second fluid passages.

A further feature of the noted rotary fluid pressure device includes having the channeling plate with a first check valve located with the first fluid passage and a second check valve located with the second fluid passage. Also, an additional feature includes having one of the first and second check valves opening for allowing high pressure flow to pass therethrough. Another feature includes having the cavity being located with and concentric with one of the channeling plate and the end plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of a hydraulic motor according to the present invention.

FIG. 2

is a sectional view of the hydraulic motor.

FIG. 3

a

is a cross-sectional view of a gerotor, a component of the hydraulic motor, shown from a first axial end.

FIG. 3

b

is a cross-sectional view of the gerotor, similar to

FIG. 3

a

, but shown from the opposite axial end.

FIG. 4

a

is an elevational view of the rotor, as viewed from a first axial end.

FIG. 4

b

is an elevational view of the rotor, similar to

FIG. 4

a

, but shown from the opposite axial end as that in

FIG. 4

a.

FIG. 5

a

is a frontal view of a manifold plate adjacent the shaft housing of the hydraulic motor.

FIG. 5

b

is a frontal view of the middle manifold plate.

FIG. 5

c

is a frontal view of a manifold plate adjacent the gerotor.

FIG. 6

a

is an end view showing the rotor relative to the stator at 0°.

FIG. 6

a

′ shows

FIG. 6

together with the manifold plate.

FIG. 6

b

is an end view showing the rotor relative to the stator at 18° counterclockwise.

FIG. 6

b

′ shows the rotor relative to the adjacent manifold plate at 18° counterclockwise.

FIG. 6

c

is an end view showing the rotor relative to the stator at 36° counterclockwise.

FIG. 6

c

′ shows the rotor relative to the adjacent manifold plate at 36° counterclockwise.

FIG. 7

a

is a frontal view of a channeling plate of the present invention taken along line

7

a

-

7

a

in FIG.

2

.

FIG. 7

b

is a sectional view of the flexible balancing plate taken along line G—G of

FIG. 7

a.

FIG. 7

c

is a rear view of the channeling plate taken along line

7

c

-

7

c

in FIG.

2

.

FIG. 8

a

is a rear view of an end cover of the present invention.

FIG. 8

b

is a cross-sectional side view of an alternate embodiment of end cover taken along line

8

b

-

8

b

of

FIG. 8

c.

FIG. 8

c

is a frontal view of the alternate embodiment of the end cover.

FIG. 9

is a schematic illustration of the fluid circuit of the hydraulic motor of this invention showing the high pressure inlet flow and the exhaust flow.

FIG. 10

is a further embodiment of the present invention, showing a sectional view of the hydraulic motor.

FIG. 11

shows a cross-sectional view of a gerotor of the further embodiment, shown from a first axial end.

FIG. 12

shows a cross-sectional view of the gerotor of the further embodiment, similar to

FIG. 11

, but shown from the opposite axial end.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, and initially to

FIG. 1

, it illustrates a compact rotary fluid pressure device

10

utilizing an IGR (Internally Generated Rotor), such as a hydraulic motor or pump (hereinafter referred to as “hydraulic motor” for ease of description) according to the present invention. Hydraulic motor

10

is designed for various applications, but is especially adapted for high torque, low speed use. As is discussed in detail below, hydraulic motor

10

is fully hydraulically balanced, has a simplified flow distribution through the manifold and gerotor set, and has a reduced number of individual components. In addition, this new design provides high starting torque while retaining high durability.

As shown in

FIGS. 1 and 2

, hydraulic motor

10

includes the following main components: Shaft housing

13

is located at one end (front) of rotary fluid pressure device

10

and surrounds a torque-transfer shaft which could be comprised of a coupling shaft

20

or a straight shaft

120

(shown in FIG.

10

). A first and a second port,

15

,

16

, are integrated into shaft housing

13

and alternately provide, depending on the direction of rotation of shaft

20

, an inlet and outlet port for hydraulic motor

10

. An end cover

70

is located at the other end (rear) of hydraulic motor

10

. A channeling plate

90

is located inwardly adjacent to end cover

70

. A drive assembly

30

is interposed between shaft housing

13

and channeling plate

90

. A drive link

25

extends through drive assembly

30

and into shaft housing

13

. A plurality of peripherally-spaced bolts

80

extend through holes

81

(shown in

FIG. 3

) and connect end cover

70

, channeling plate

90

, drive assembly

30

and shaft housing

13

.

Shaft housing

13

has a stepped internal bore

17

for receiving and rotatably supporting coupling shaft

20

. Within an axial front portion of internal bore

17

, a dirt seal

21

is positioned surrounding shaft

20

and prevents outside contaminants from entering internal bore

17

. Two axially-spaced radial bearings

22

are located within internal bore

17

for rotatably supporting shaft

20

. A high pressure shaft seal

23

is provided in a fluid-tight arrangement around shaft

20

in order to prevent any internal fluid from leaking into the front portion of bore

17

. Two axially-spaced thrust bearings

24

are located within internal bore

17

and prevent coupling shaft

20

from moving axially. Extending axially from an inner end of second port

16

is an axial passageway

36

that connects port

16

with a circumferential fluid chamber

37

abutting one end of drive assembly

30

.

Coupling shaft

20

has a rear clevis portion

27

having a hollow center with internal splines. Coupling shaft rear portion

27

includes an axial passageway

28

that extends from its hollow center into a radial passageway

29

, which in turn is in fluid communication with a fluid chamber

18

located within shaft housing internal bore

17

. Coupling shaft rear portion

27

also includes radial flow passages

19

connecting fluid chamber

26

and fluid chamber

18

.

Drive link

25

has a front portion

25

a

and a rear portion

25

b

, both having external splines. The external splines on front portion

25

a

mate with complementary internal splines on coupling shaft rear portion

27

. The external splines on rear portion

25

b

mate with complementary internal splines in drive assembly

30

. A fluid chamber

26

surrounds drive link

25

and extends along a major portion of its axial extent.

Drive assembly

30

includes a manifold

32

and a gerotor set

40

. Manifold

32

is comprised of a series of apertured individual plates

33

a-c

(shown in detail in

FIGS. 5

a-c

) which are affixed together (e.g. by brazing or via peripherally-spaced bolts) in order to form two separate flow paths. The flow through all three affixed plates is shown in

FIG. 9

and will be discussed in greater detail below. Each individual plate has a different path configuration extending therethrough. Referring cursorily to

FIG. 9

, these affixed plates provide a first flow path

38

extending between shaft housing

13

and gerotor set

40

, and a second flow path

39

extending between gerotor set

40

and shaft housing

13

respectively. Referring now to apertured affixed plates

33

a-c

,

FIG. 5

a

shows plate

33

a

, one side of which is directly adjacent to shaft housing

13

. The darker shaded apertures or areas

39

a

signify fluid from second flow path

39

(

FIG. 9

) through a central bore and the lighter shaded apertures or areas

38

a

signify fluid from first flow path

38

(

FIG. 9

) through a set of apertures radially spaced from central bore. The lighter shaded areas

38

a

align with fluid chamber

37

of shaft housing

13

when the components are assembled.

FIG. 5

b

shows intermediate plate

33

b

, one side of which is adjacent to, and aligned with, the other side plate

33

a

, on the side opposite shaft housing

13

. As in

FIG. 5

a

, the lighter shaded areas

38

a

signify fluid from first flow path

38

and the darker shaded areas

39

a

signify fluid from second flow path

39

. As can be seen, lighter shaded areas

38

a

are in a series of comb-like apertures having inwardly directed radial tooth-like members. Darker shaded areas

39

a

are in a single aperture comprised of a plurality of circumferentially spaced outwardly radially directed finger-like openings in communication with the center. It should be noted that the aperture continues from the center of plate

33

b

to the finger-like extensions. As previously noted, plates

33

a-c

are aligned, and affixed together.

FIG. 5

c

shows plate

33

c

that is positioned between the other side of plate

33

b

and one end of gerotor set

40

. Again the lighter shaded areas

38

a

signify fluid from first flow path

38

and the darker shaded areas

39

a

signify fluid from second flow path

39

.

Referring now to

FIG. 3

a

, which shows gerotor set front side

40

a

, and

FIG. 3

b

, which shows gerotor set back side

40

b

, gerotor set

40

consists of an outer stator

41

and an inner rotor

45

. Outer stator

41

has a plurality, N+1, of internal gear teeth

42

, that provide conjugate interaction with a plurality, N, of gear teeth

46

on the outer periphery of inner rotor

45

. Rotor gear teeth

46

preferably have a circular arc shape and can be replaced with hardened rollers for high efficiency gerotor set motors. The use of hardened rollers for rotor gear teeth

46

reduces wear, friction, and leakage in the hydraulic motor.

Referring to

FIG. 4

a

, the front side

58

, or the side adjacent manifold plate

33

c

, of rotor

45

is shown. Front side

58

shows two sets of pluralities of passages, axial passages

48

and axial through orifices

51

, both extending through the rotor. Both sets of passages

48

and

51

have openings on both axial sides of rotor

45

(as shown in

FIGS. 4

a-b

). As will be discussed in detail below, each axial passage

48

is used as a passageway for high-pressure fluid and exhaust fluid. As will also be discussed below, each axial through orifice

51

is used for improving the rotary movement of rotor

45

. The outer periphery of rotor

45

is defined by a series, nine in the example shown in

FIG. 4

a

, of equally circumferentially-spaced intermediate portions

52

separated via a series of semi-cylindrical pockets or recesses

53

which serve to receive rotor gear teeth or rollers

46

. Spaced portions

52

have a radial outer surface which preferably is substantially perpendicular (but not limited thereto) to rotor front side

58

, rotor back side

63

, and any radial plane emanating from the axial center line of the rotor internal bore, or apertured center. The apertured center of rotor

45

is provided with internal splines

50

located at its peripheral surface for mating engagement with the external splines of drive line rear portion

25

b

. This engagement transfers high torque from rotor

45

to drive link

25

and from same to coupling shaft

20

.

FIG. 4

b

shows the rear side surface

63

, or the side adjacent channeling plate

90

, of rotor

45

. Axial passages

48

and axial through orifices

51

, both extending from front side surface

58

, are shown. Surrounding each through orifice

51

and extending slightly axially into rotor rear side

63

is a recess

51

a which can be trapezoidal in shape and is coaxial with orifice

51

. The radial upper or outer portion of each axial passage

48

is provided with another recess

48

a

, which also can be trapezoidal in shape, and extends radially outward into flat portion

52

. During operation, recesses

48

a

and

51

a

are filled with fluid for the purpose of reducing the viscous friction between rotating rotor

45

and non-rotating channeling plate

90

. Viscous friction is also reduced due to the reduction of the outer annular area of rotor rear side surface

63

via recesses

48

a

and

51

a

. A flower-shaped or multiple-convoluted recess

64

is positioned radially outward of rotor internal splines

50

in rotor rear side surface

63

and continues along the whole circumference thereof. As will be discussed below, recess

64

always receives high pressure fluid in order to overbalance rotor

45

, thus axially biasing rotor

45

towards manifold

32

in order to reduce fluid leakage between manifold

32

and gerotor set

40

, which interface is referred to as the valve interface.

Rotor

45

has a plurality, N, of central, individual radial fluid channels

47

within flat portions

52

. Radial fluid channels

47

are preferably at least one of substantially axially centered between rotor front side

58

and rear side

63

, and substantially circumferentially centered relative to their adjacent rotor gear teeth

46

(

FIG. 3

a

), and preferably both substantially axially and substantially circumferentially centered. One (inner) end of each radial fluid channel

47

opens into an axial passage

48

, extending through rotor

45

, and the other (outer) end opens radially into a gerotor set volume chamber

54

(as shown in

FIGS. 3

a-b

). The end of passage

48

that opens into gerotor set volume chamber

54

is preferably centered within equally circumferentially spaced intermediate portions

52

. Each volume chamber

54

is bounded by two nearby inner rotor gear teeth

46

, circumferentially-spaced portion

52

of the rotor outer peripheral surface, and the undulating internal surface of stator

41

. Gerotor set

40

has N volume chambers, which coincides with the number of fluid channels

47

. Rotor

45

also has a plurality, N, of individual radial fluid channels

55

located at either, or both, rotor front side

58

or rotor rear side

63

of rotor

45

. Radial fluid channels

55

are shown at rotor front side

58

, but can also be placed on rotor rear side

63

. Radial fluid channels

55

are preferably circumferentially centered in the manner preferably described with reference to channels

47

, and preferably parallel with channels

47

.

Referring to

FIGS. 2

,

3

a

and

3

b

, stator

41

is shown in detail. As mentioned above, stator

41

has internal gear teeth

42

, that interact with gear teeth

46

of inner rotor

45

. Located radially outward of gear teeth

42

are bolt holes

81

for receiving bolts

80

, which affix stator

41

between a channeling plate

90

and manifold

32

. A through hole

43

extends axially through stator

41

. Positioned radially outward of through hole

43

are two circumferential seal cavities

44

, located on both axial end surfaces of stator

41

, for receiving seals

67

.

Referring to

FIGS. 7

a-c

, channeling plate

90

is shown with bolt holes

81

, for receiving bolts

80

(not shown), extending therethrough. A first check valve opening

91

extends through channeling plate

90

, with check valve opening

91

being defined by a first portion

91

a

and a second portion

91

b

. First portion

91

a

has a diameter larger than second portion

91

b

such that it can receive a check ball (not shown) having a diameter larger than that of second portion

91

b

. When assembled, as shown in

FIG. 2

, second portion

91

b

is aligned with stator through hole

43

and is in fluid communication with first flow path

38

(as shown in FIG.

9

). A second check valve opening

92

also extends through channeling plate

90

, and, similar to check valve opening

91

, opening

92

has a first portion

92

a

and a second portion

92

b

. First portion

92

a

has a diameter larger than second portion

92

b

such that it can also receive a check ball (not shown) having a diameter larger than that of second portion

92

b

. When assembled, as shown in

FIG. 2

, second portion

92

b

is coaxial with the center of gerotor set

40

and is in fluid communication with second flow path

39

(as shown in FIG.

9

). At least one further through hole

93

and preferably a plurality of circularly spaced holes

93

extend through channeling plate

90

and are situated in a location between but not radially aligned with both first and second check valve openings

91

and

92

. When assembled, (not shown), at least one through hole

93

is aligned with multiple-convoluted recess

64

on the rotor back side

63

(as shown in

FIG. 4

b

). It should be understood that the convoluted shape of recess

64

is due to the fact that rotor

45

both rotates and orbits at the same time. At least one through hole

93

supplies high pressure fluid to multiple-convoluted recess

64

.

FIG. 7

c

shows the inner axial surface

90

b

of channeling plate

90

which is directly adjacent end cover

70

. A coaxial circular recess

96

for receiving high pressure fluid, detailed below, is shown. A recessed coaxial annular seal cavity

97

is positioned, radially outside of bolt holes

81

with seal cavity

97

receiving seal

67

(not shown). Recess

96

has a flow channel

96

a

extending radially outward and terminating into seal cavity

97

. Check valve opening

91

, and more specifically first portion

91

a

, is centered within flow channel

96

a.

Referring to

FIG. 8

a

, the substantially flat outer axial surface of end cover

70

is shown. In the present invention, the inner axial surface of end cover

70

is substantially similar to that of the axial outer surface shown in

FIG. 8

a

. Bolt holes

81

extend through end cover

70

and receive bolts

80

, not shown, which align end cover

70

with channeling plate

90

. As part of another embodiment of the invention,

FIGS. 7

b-c

show how recess

96

and seal cavity

97

of channeling plate

90

can alternately be incorporated into the inner axial surface of end cover

70

rather than being incorporated in channel plate

90

. Similar to the design of

FIGS. 7

b

and

7

c

, a coaxial circular recess

72

is incorporated into the inner axial surface of end cover

70

for receiving high-pressure fluid. A recessed coaxial annular seal cavity

71

is positioned, radially outside of bolt holes

81

, in end cover

70

, with seal cavity

71

receiving a seal, similar to seal

67

.

FIG. 8

c

shows the inner axial surface of end cover

70

, as part of the alternate embodiment, which is directly adjacent channeling plate

90

. Recess

72

has a flow channel

73

extending radially outward, with flow channel

73

having its radial outer portion

74

terminating into end cover seal cavity

71

. When assembled, flow channel radial outer portion

74

is radially and axially aligned with first portion

91

a of first check valve opening

91

.

The hydraulic circuit and operation of hydraulic motor

10

will now be discussed. Referring first to

FIG. 9

, the fluid path for hydraulic motor

10

is shown when it operates in a first direction. High pressure fluid

38

enters second port

16

and follows the path indicated by darker shading with triangular shapes. It should be noted that although fluid

38

is shown entering port

16

in

FIG. 9

, this path could be reversed with exhaust fluid emanating therefrom. Ports

15

and

16

can be either inlet or outlet ports, depending on the desired direction of rotation of hydraulic motor

10

. For sake of description, the triangular shaded path was chosen to represent high pressure inlet fluid

38

, with fluid

38

, entering port

16

, traveling axially through passageway

36

and entering fluid chamber

37

. Fluid

38

then travels into manifold

32

through the axially aligned passages in manifold plate

33

a

(as seen and indicated by

38

a

in

FIG. 5

a

). Fluid

38

further flows axially from plate

33

a

into plate

33

b

(as shown and indicated by

38

a

in

FIG. 5

b

) and travels radially inwardly while passing through this plate. Fluid

38

continues its flow into and axially through a plurality, N+1, of aligned openings

34

in plate

33

c

(as shown and indicated by

38

a

in

FIG. 5

c

), with openings

34

being aligned with rotor axial passages

48

and fluid

38

passing into these passages. Finally, fluid

38

then flows radially outwardly through fluid channels

47

(

FIG. 4

b

) within rotor

45

into gerotor set volume chambers

54

. Fluid

38

also flows radially outward through fluid channel

55

(

FIGS. 4

a

and

9

) into volume chambers

54

. The pressurized fluid

38

causes volume chambers

54

to expand. As well known to those skilled in the art, this fluid communication causes rotor

45

to rotate and orbit within fixed stator

41

. The expanding volume chambers, coupled with the rotation and orbiting of rotor

45

, i.e., hypocloidal movement, will cause other volume chambers

54

to contract. Contraction of volume chambers

54

provides the exhausting, or return fluid flow indicated by second flow path

39

.

Exhausting fluid

39

is indicated with dotted shading, and begins its flow with the contraction of gerotor set volume chambers

54

forcing exhaust fluid

39

radially inwardly through rotor fluid channels

47

. Fluid

39

enters axial fluid passages

48

(

FIG. 4

b

), flows towards plate

33

c

and enters the aligned openings

34

therein (as shown and indicated by

39

a

in

FIG. 5

c

). Fluid

39

then travels into manifold plate

33

b

and flows radially inwardly while passing therethrough (as shown and indicated by

39

a

in

FIG. 5

b

). Fluid

39

continues its flow axially through the center of plate

33

a

(as shown and indicated by

39

a

in

FIG. 5

a

).

Drive link

25

(

FIG. 9

) extends freely through the center of manifold plates

33

a-c

and its rear end

25

b

is linked to rotor

45

, via the previously-described cooperating spline arrangement, and rotates and orbits with rotor

45

. Therefore, the portion of drive link

25

that extends through the center of manifold plates

33