Technical Field

The present disclosure generally relates to a gerotor pump assembly, an engine fluid delivery system using a gerotor pump assembly and miscellaneous components therefor.

Background

Gerotor type hydraulic pumps typically include an internally toothed outer gerotor and an externally toothed inner gerotor disposed in a pump housing. The teeth on the respective gerotors cooperate to define a plurality of variable volume chambers. When the gerotors are rotated, a variable volume chamber will initially increase in volume to create a low pressure or suction area, and subsequently decrease in volume to create a high pressure or compression area. An inlet port communicates with the low pressure area so that fluid in the inlet port is drawn into the variable volume chamber. Upon further rotation, whereupon the variable volume chamber decreases in volume, the fluid is discharged through an outlet port at an elevated pressure. When the gerotors rotate at high speeds, the fluid pressure may increase to undesirable levels. Accordingly, a relief valve may be used to reduce fluid overpressure.

Summary of the disclosure

According to a first aspect of the present disclosure there is provided a gerotor pump assembly, comprising: a pump housing defining a suction portion and a compression portion; a pump outlet in fluid communication with the compression portion of the pump housing; and a gerotor rotatably disposed within the pump housing and defining a gerotor front face, a gerotor rear face and a gerotor side wall; the gerotor comprising an outer gerotor and an inner gerotor, with the inner gerotor operably engaging the outer gerotor to define a plurality of variable volume chambers, wherein during rotation of the inner and outer gerotors the variable volume chambers located in the suction portion of the pump housing increase in volume and the variable volume chambers located in the compression portion of the pump housing decrease in volume; wherein the compression portion of the pump housing extends into fluid communication with both the gerotor front face and the gerotor rear face to allow, in use, exit of an engine fluid from the variable volume chambers via both the gerotor front face and the gerotor rear face. In another aspect there is provided a valve element for a relief valve of a gerotor pump assembly comprising a valve element inlet at a first end and one or more valve element outlets located in a side wall of the valve element; wherein the side wall of the valve element further comprises a circumferential groove located at a point along the side wall to at least partially coincide with the one or more valve element outlets.

In another aspect there is provided a relief valve for a gerotor pump assembly comprising: a relief valve housing defining a relief valve inlet and a relief valve outlet; a valve element as described above in the previous aspect which is movable within the relief valve housing between closed and open configurations to control transmission, in use, of an engine fluid through the relief valve assembly; and a resilient member for biasing the valve element into the closed configuration. In another aspect there is provided the combination of a gerotor pump assembly and a relief valve.

In another aspect there is provided a gerotor pump assembly, comprising: a pump housing defining a suction portion and a compression portion; a pump outlet in fluid communication with the compression portion of the pump housing; a gerotor rotatably disposed within the pump housing; and a relief valve assembly in fluid communication with the compression portion of the pump housing; the gerotor comprising an outer gerotor and an inner gerotor, with the inner gerotor operably engaging the outer gerotor to define a plurality of variable volume chambers, wherein during rotation of the inner and outer gerotors the variable volume chambers located in the suction portion of the pump housing increase in volume and the variable volume chambers located in the compression portion of the pump housing decrease in volume; the relief valve assembly comprising: a relief valve housing defining a relief valve inlet and a relief valve outlet; and a valve element movable within the relief valve housing between closed and open configurations to control transmission, in use, of an engine fluid through the relief valve assembly; wherein the relief valve inlet directly communicates with the compression portion of the pump housing. ln another aspect there is provided a gerotor pump assembly, comprising: a pump housing defining a suction portion and a compression portion; a pump inlet in fluid communication with the suction portion of the pump housing; a pump outlet in fluid communication with the compression portion of the pump housing; and a gerotor rotatably disposed within the pump housing; the gerotor comprising an outer gerotor and an inner gerotor, with the inner gerotor operably engaging the outer gerotor to define a plurality of variable volume chambers, wherein during rotation of the inner and outer gerotors the variable volume chambers located in the suction portion of the pump housing increase in volume and the variable volume chambers located in the

compression portion of the pump housing decrease in volume; wherein the suction portion of the pump housing defines a suction cavity which provides fluid communication between the pump inlet and the variable volume chambers as the gerotor rotates within the pump housing; wherein the suction cavity extends through an angle greater than 140° about the rotational axis of the outer gerotor

In another aspect there is provided a gear shaft for an idle gear of a gerotor pump assembly comprising a cylindrical shaft having a head at one end defined by an outwardly extending flange; the cylindrical shaft comprising: a circumferential oil entry groove arranged in a surface of the cylindrical shaft; an oil outlet port arranged in the surface of the cylindrical shaft at a distance from the circumferential oil entry groove; and an oil transmission conduit extending internally through the cylindrical shaft and providing fluid communication from the circumferential oil entry groove to the oil outlet port. In another aspect there is provided an idle gear for a gerotor pump assembly comprising a toothed idle gear wheel rotatably mounted on a gear shaft as described above in the previous aspect.

In another aspect there is provided the combination of a gerotor pump assembly and an idle gear.

In another aspect there is provided an engine fluid delivery system for a machine, comprising: a sump for holding an engine fluid; a gerotor pump assembly as described above in the previous aspects; and a suction pipe for fluid communication between the sump and the gerotor pump assembly. Brief description of the drawings

An embodiment of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a gerotor pump assembly according to the present disclosure;

Figure 2 is an exploded perspective view of the gerotor pump assembly of Figure

1 ;

Figure 3 is a cross-sectional view of the gerotor pump assembly of Figure 1 ;

Figure 4 is an end elevation of the of the gerotor pump assembly of Figure 1 with certain components omitted for clarity;

Figure 5 is an end elevation as shown in Figure 4 but with further components omitted for clarity;

Figure 6 is a perspective view of a valve element of the gerotor pump assembly of Figure 1 ;

Figure 7 is an enlarged view of a portion of the valve element of Figure 6;

Figure 8 is a cross-sectional view through a relief valve assembly of the gerotor pump assembly of Figure 1 in a closed configuration;

Figure 9 is a cross-sectional view through the relief valve assembly of Figure 8 in an open configuration;

Figure 10 is a cross-sectional view through certain gear train components of the gerotor pump assembly of Figure 1 ;

Figure 1 1 is a perspective view of an idle gear shaft of the gerotor pump assembly of Figure 1 ;

Figure 12 is a cross-sectional view through the idle gear shaft of Figure 1 1 ; and Figure 13 is a perspective view through a portion of the gerotor pump assembly of Figure 1 with hidden detail shown. Detailed description

An embodiment of a gerotor pump assembly is disclosed for use in an engine fluid delivery system. The engine fluid delivery system is described herein as an engine oil pump system, however it will be appreciated that the gerotor pump assembly may be used to deliver fuel or other types of fluids to the engine. Additionally, the engine fluid delivery system may be used on any type of machine, stationary or mobile, that requires a circulating fluid.

The engine oil pump system may typically in use be coupled to an engine and may comprise the gerotor pump assembly so configured to retrieve oil from a sump and deliver it to the engine at an elevated pressure.

Figures 1 and 2 illustrate a gerotor pump assembly 1 which may be used in such a manner. The gerotor pump assembly 1 comprises a pump inlet 2 and a pump outlet 3. A suction tube of the engine oil pump system may be coupled to the pump inlet 2. The gerotor pump assembly 1 is operable to draw oil from the sump through the suction tube and discharge it through the pump outlet 3 at an elevated pressure.

The gerotor pump assembly 1 includes a pump housing 4 which may be formed from one or more castings. As shown in Figure 3, the pump housing 4 defines a pumping section 1 0 having a suction portion 5 defining a suction cavity 40 and a compression portion 6 defining a compression cavity 41 which may be at one end of the pump housing 4. In addition, the pump housing 4 may include one or more conduits for transferring oil to and from the pumping section 10. For example, the pump housing 4 may comprise an inlet conduit 7 fluidly linking the pump inlet 2 to the suction portion 5, an outlet conduit 8 fluidly linking the compression portion 6 to the pump outlet 3, and a relief valve conduit 9, the function of which will be described further below. The pump inlet 2 and the pump outlet 3 may be located at an end of the pump housing 4 opposite the pumping section 1 0.

As most clearly shown in Figures 4 and 5, the gerotor pump assembly 1 further includes within the pumping section 10 a gerotor formed from an outer gerotor 1 1 and an inner gerotor 1 2 for generating a pressure differential within the pump housing 4. The outer gerotor 1 1 has inwardly extending teeth 1 3, while the inner gerotor 1 2 has outwardly extending teeth 14 that operably engage the inwardly extending teeth 1 3 of the outer gerotor 1 1 . The outer gerotor 1 1 is supported for rotation about a first axis 15, while inner gerotor 1 2 is supported for rotation about a second axis 1 6 that is spaced from the first axis 15 to effect a gear eccentricity that permits proper operation of the gerotor pump assembly 1 . In addition, the inner gerotor 12 may have one less tooth than the outer gerotor 1 1 . A plurality of variable volume chambers 20 are defined between engaged pairs of inwardly extending teeth 13 and outwardly extending teeth 14. When the outer gerotor 1 1 and inner gerotor 12 are rotated, a variable volume chamber 20 will increase in volume as it travels through the suction portion 5 of the pumping section 10, thereby to produce a relatively low pressure that draws fluid into the variable volume chambers 20. Subsequently, as the outer gerotor 1 1 and inner gerotor 12 continue to rotate, the variable volume chamber 20 will decrease in volume as it travels through the

compression portion 6 of the pumping section 10, thereby to produce a relatively high pressure that discharges fluid from the variable volume chambers 20. As most clearly shown in Figure 3, in one aspect of the disclosure the compression portion 6 of the pump housing 4 extends into fluid communication with both a gerotor front face 31 and a gerotor rear face 32 of the gerotor to allow, in use, exit of oil from the variable volume chambers 20 via both the gerotor front face 31 and the gerotor rear face 32. To permit this, the gerotor front face 31 may be spaced from a front wall 34 of the compression portion 6 of the pump housing 4 and the gerotor rear face 32 may be spaced from a rear wall 35 of the compression portion 6 of the pump housing 4. In addition, a gerotor side wall 33 of the outer gerotor 1 1 may be spaced from a side wall 36 of the compression portion 6 of the pump housing 4. Thus, the compression cavity 41 of the compression portion 6 of the pumping section 10 may extend in a contiguous manner around the front, side and rear of the gerotor.

In addition, the suction portion 5 of the pump housing 4 may extend into fluid

communication with both the gerotor front face 31 and the gerotor rear face 32 to allow, in use, entry of oil into the variable volume chambers 20 via both the gerotor front face 31 and the gerotor rear face 32. To permit this, the gerotor front face 31 may be spaced from a front wall 37 of the suction portion 5 of the pump housing 4 and the gerotor rear face 32 may be spaced from a rear wall 38 of the suction portion 5 of the pump housing 4. In addition, the gerotor side wall 33 may be spaced from a side wall 39 of the suction portion 5 of the pump housing 4. Thus, the suction cavity 40 of the suction portion 5 of the pumping section 10 may extend in a contiguous manner around the front, side and rear of the gerotor.

As most clearly shown in Figure 5, in another aspect of the disclosure the suction cavity 40 may extend through an angle a greater than 140 ° about the first axis 15 about wHch the outer gerotor 1 1 rotates. Optionally, the suction cavity 40 extends through an angle a greater than 1 50 ° about the first axis 15. Thus, the suction cavity 40 may encompass greater than 140 ° , optionally greater than 1 50 ° , ofthe 360 ° circumferential extent of the pumping chamber 10. The suction cavity 40 may comprise an arcuate portion 50 which is curved about the first axis 1 5. The arcuate portion 50 may comprise a first end 51 which has a bicuspid shape. In particular, the first end 51 having a bicuspid shape may comprise a first tongue section 52 and a second tongue section 53. The second tongue section 53 may be elongated relative to the first tongue section 52. The first tongue section 52 and/or the second tongue section 53 may be shallower than a remainder of the arcuate portion 50 of the suction cavity 40.

In another aspect of the disclosure, as shown in Figures 6 to 9, the gerotor pump assembly 1 may comprise a relief valve assembly 60 in fluid communication with the compression portion 6 of the pump housing 4. The relief valve assembly 60 may comprise a relief valve housing 61 defining a relief valve inlet 62 and a relief valve outlet 63. A valve element 64 may be movable within the relief valve housing 61 between closed and open configurations to control transmission, in use, of oil through the relief valve assembly 60. A resilient member 66 may be provided for biasing the valve element 64 into the closed configuration. For example, a helical spring may be provided extending between the valve element 64 and an end cap 67 which may close off one end of the relief valve housing 61 .

The relief valve inlet 62 may directly communicate with the compression portion 6 of the pump housing 4. For example, the relief valve inlet 62 may be fluidly linked to the compression cavity 41 of the compression portion 6 by the relief valve conduit 9.

The compression portion 6 of the pump housing 4 may comprise a first compression portion outlet 70 providing fluid communication from the compression portion 6 to the pump outlet 3 and a second compression portion outlet 71 providing fluid communication from the compression portion 6 to the relief valve conduit 9 and relief valve inlet 62. The second compression portion outlet 71 may communicate solely with the relief valve inlet

62. In other words, the fluid communication to the relief valve assembly 60 may not be via a portion of the outlet conduit 8 taking fluid flow towards the pump outlet 3.

The second compression portion outlet 71 may be provided in the rear wall 35 of the compression portion 6 of the pump housing 4. The second compression portion outlet 71 may be located in the rear wall 35 of the compression portion 6 of the pump housing 4 at a location at least partially over-swept by the rotating gerotor. As can be seen in Figure 3, the relief valve conduit 9 between the compression portion 6 of the pump housing 4 and the relief valve inlet 62 may be devoid of any bends having an angular deviation of greater than 30 ° . Thus a straight or relatively s aight path for the oil from the

compression cavity 41 to the relief valve assembly 60 may be provided.

The relief valve outlet 63 may fluidly communicate with the suction portion 5 of the pump housing 4. For example, this may be via a bypass conduit 1 7 which may lead from the relief valve outlet 63 to join part-way along the inlet conduit 7.

In another aspect of the disclosure the valve element 64 may comprise a valve body 81 having a valve element inlet 89 at a first end and one or more valve element outlets 84 located in a side wall 90 of the valve body 81 . As shown in Figure 6, a boss 82 may be provided at an opposite end from the valve element inlet 89 to serve as a mounting for one end of the resilient member 66. The valve body 81 may be tubular and the one or more valve element outlets 84 may comprise a plurality, preferably four, radially- orientated apertures in the side wall 90 of the valve element 64. As shown in Figures 6 and 7, the side wall 90 of the valve element 64 may further comprise a circumferential groove 83 located at a point along the side wall 90 to at least partially coincide with the one or more valve element outlets 84. The circumferential groove 83 may define a front lip 85 that may be aligned at, or in front of, a foremost longitudinal position of the one or more valve element outlets 84. The circumferential groove 83 may define a rear lip 86 that may be aligned within the longitudinal extent of the one or more valve element outlets 84. A forward portion of the circumferential groove 83 at or near the front lip 85 may be provided with a chamfer 87, which may be angled at 45 ° to a longitudinal axis of the valve element 64.The rear lip 86 may be provided with a radiused filet 88.

In the closed configuration of Figure 8, the valve element 64 is located within the relief valve housing 61 such that the valve element outlets 84 are sealed against an inner face of a narrowed bore 92 of the relief valve housing 61 . When exposed to a sufficient pressure rise at the relief valve inlet 62 to overcome the bias of the resilient member 66, the valve element 64 may slide into the open configuration of Figure 9 wherein the valve element outlets 84 have moved into an enlarged bore 93 of the relief valve housing 61 such that fluid communication is established from the relief valve inlet 62 to the relief valve outlet 63 via the valve body 81 and the valve element outlets 84 and

circumferential groove 83. Once the pressure rise has been removed the valve element 64 may return to the closed configuration. On closure, the circumferential groove 83 may retain oil which may lubricate movement of the valve element 64 within the narrowed bore 92.

In another aspect of the disclosure the gerotor pump assembly 1 may further comprise one or more gear train components. As shown in Figures 1 and 2, the pump housing 4 may be provided with a toothed gerotor drive gear 1 00 and an idle gear 1 01 . The toothed gerotor drive gear 100 and the idle gear 101 may be rotatably mounted within apertures of a pump housing cover 102 which may form a part of the pump housing 4. The idle gear 101 may comprise a toothed idle gear wheel 103 which may be rotatably mounted on a gear shaft 1 04 as shown in detail in Figures 1 0 to 13. A bushing 105 may be interposed between the gear shaft 1 04 and the toothed idle gear wheel 1 03.

The gear shaft 104 may comprise a cylindrical shaft 1 06 having a head 1 07 at one end defined by an outwardly extending flange 1 08. The cylindrical shaft 1 06 may comprise a circumferential oil entry groove 109 arranged in a surface 1 10 of the cylindrical shaft, an oil outlet port 1 1 1 arranged in the surface 1 1 0 of the cylindrical shaft at a distance from the circumferential oil entry groove, and an oil transmission conduit 1 12 extending internally through the cylindrical shaft 1 06 and providing fluid communication from the circumferential oil entry groove 109 to the oil outlet port 1 1 1 . The circumferential oil entry groove 109 may be located distal the head 107 and the oil outlet port 1 1 1 may be located proximal the head 107. The oil transmission conduit 1 1 2 may be defined by a straight, diagonally-orientated conduit. When assembled, the bushing 105 may overlie the oil outlet port 1 1 1 of the gear shaft

104. As shown in Figure 1 3, when the idle gear 101 is assembled to the pump housing the circumferential oil entry groove 1 09 may be aligned with an outlet of an idle gear oil feed conduit 120 which extends into fluid communication with the compression portion 6 of the pump housing 4. Industrial Applicability

The present disclosure is applicable to machines that include a gerotor pump assembly to deliver an engine fluid to an engine. The gerotor pump assembly may provide oil, fuel, or other engine fluid needed by the engine. The engine may be provided on a mobile or stationary machine. Where the engine fluid is oil the gerotor pump assembly may provide oil to support hydrostatic bearings and lubricated moving parts of the engine.

In one aspect a gerotor pump assembly 1 is provided wherein, in use, an engine fluid may exit from the variable volume chambers 20 via both the gerotor front face 31 and the gerotor rear face 32. This may permit a more balanced axial force loading on the gerotor during use since both the gerotor front face 31 and the gerotor rear face 32 are exposed to the same fluid pressure as opposed to having one face of the gerotor exposed to a different pressure level. The more balanced axial force loading may allow for smoother operation of the gerotor pump assembly 1 and reduced wear of the gerotor front and rear faces. In addition, the increased number of points of exit for the engine fluid from the gerotor, in both the gerotor front face 31 and the gerotor rear face 32, may result in a smoothing of pressure fluctuations in the delivered engine fluid.

In another aspect the suction cavity 40 may extend through an angle a greater than 140 ° . The increased angular length of the suction cavity 40 permits for easier engine fluid entry into the variable volume chambers 20. This is particularly advantageous when the gerotor is rotating at high speeds since it allows for a longer period for the engine oil to enter the variable volume chambers 20 as the teeth of the outer gerotor 1 1 and the inner gerotor are moving apart. This may help to reduce cavitation within the gerotor.

In another aspect the gerotor pump assembly 1 the relief valve assembly 60 directly communicates with the compression portion 6 of the pump housing 4. In particular, the second compression portion outlet 71 that leads to the relief valve assembly 60 may be located in the rear wall 35 of the compression portion 6 of the pump housing 4 at a location at least partially over-swept by the rotating gerotor. In this way, pressure fluctuations may be reduced, and pressure rises, produced by the rotating gerotor, may be more directly transmitted to the relief valve assembly 60. This may result in a faster and more accurate response of the relief valve assembly 60. Further, a straight or relatively straight path for the engine fluid from the compression cavity 41 to the relief valve assembly 60 may be provided. Again, this may result in a faster and more accurate response of the relief valve assembly 60.

In another aspect the circumferential groove 83 and chamfer 87 of the valve element 64 may help to reduce pressure fluctuations and jamming of the relief valve assembly 60 by providing a more gradual increase in the open flow area of the relief valve assembly 60 during opening. In addition, On closure, oil which may be retained in the circumferential groove 83 can lubricate movement of the valve element 64 within the narrowed bore 92 which may allow for a smoother operation of the relief valve assembly 60 and reduced component wear.

In another aspect when the idle gear 101 is assembled to the pump housing 4 the circumferential oil entry groove 109 may be easily aligned with the outlet of the idle gear oil feed conduit 120 since the circumferential oil entry groove 109 may extend completely around the circumference of the gear shaft 104. Thus there is no need to determine a specific angular orientation of the gear shaft 104 when mounting it with the pump housing 4 since alignment between the circumferential oil entry groove 109 and the idle gear oil feed conduit 120 is assured. It will be appreciated that the foregoing description provides examples of the disclosed assemblies, apparatus and methods. These examples are not to be understood as limiting on the present disclosure. Instead, it will be understood that the examples may be varied without departing from the scope of the present disclosure as set out in the appended claims. In particular, elements of one aspect may be combined with elements of other aspects unless explicitly excluded in the foregoing description.

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.