HIG OUTER ROTOR SHADOW POCKETS

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This patent application claims priority to U.S. Provisional Patent Application Ser. No. 63/723,404, filed on Nov. 21, 2024, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a gerotor pump, and more particularly, a gerotor pump having a pressure relief feature for preventing axial disengagement between an outer gerotor and a housing of the gerotor pump.

BACKGROUND

A gerotor pump is a form of internal rotary positive-displacement pump that utilizes an inner rotor (georotor) disposed within an outer rotor (georotor) to pump a liquid, such as a lubricating oil, via an interaction between the inner and outer gerotors during mutual rotation thereof. The inner gerotor includes outwardly extending teeth configured to mesh with inwardly extending teeth of the outer gerotor to transfer rotational motion therebetween. The axes of rotation of the inner and outer gerotors are offset from one another and the inner gerotor includes one less tooth than does the outer gerotor in a manner resulting in the continual formation of continuously changing cavities between the inner surface of the outer gerotor and the outer surface of the inner gerotor. More specifically, such cavities first expand in size as a tooth of the inner gerotor starts to withdraw from a notch between adjacent teeth of the outer gerotor for expanding a space therebetween and then such cavities contract in size as the tooth of the inner gerotor eventually starts to enter another notch of the outer gerotor for contracting the space therebetween. A suction pressure resulting from the described expansion of the cavities draws the liquid into the expanding cavities at an inlet side of the gerotor pump while the compression of the liquid resulting from the contraction of the cavities pumps the liquid out of the gerotor pump at an outlet side thereof.

One drawback that has been discovered with respect to such gerotor pumps relates to the variable axial forces acting on the outer gerotor during different modes of operation of the gerotor pump. The effects of such variable forces are summarized with reference to an exemplary configuration of a gerotor pump 1 as shown in FIG. 1, wherein the gerotor pump 1 is shown with respect to each of a plurality of different circumstances A-G that occur in succession during operation of the gerotor pump 1. With reference to the graph of FIG. 2, each of the identified circumstances A-G corresponds a combination of the instantaneous flow rate and pressure of the pumped liquid passing through the gerotor pump 1 as the gerotor pump 1 progresses through a cycle of operation. The gerotor pump 1 includes, in relevant part for the present explanation, a housing wall 2 having an inner face 2a, an outer gerotor 3 having a rim 3a configured to engage the inner face 2a, and a shaft 4 extending through and defining an axis of rotation of the outer gerotor 3. The shaft 4 is partially received within a cylindrical sleeve 5 extending axially inwardly from the inner face 2a of the housing wall 2, and the housing wall 2 further includes each of an inlet opening 6 and an outlet opening 7 formed therethrough to opposing sides of the sleeve 5 and the shaft 4. An end of the shaft 4 opposite the sleeve 5 may be axially constrained by a housing portion 8 facing towards the corresponding end of the shaft 4. Although not pictured, circumferentially progressing cavities are progressively formed between the inner surfaces of the outer gerotor 3 and the outer surfaces of an inner gerotor (not shown) received within the outer gerotor 3, wherein the pumped liquid enters such cavities axially via the inlet opening 6 and then exits such cavities in an opposing axial direction via the outlet opening 7.

One concern associated with the disclosed configuration of the exemplary gerotor pump 1 relates to the manner in which the liquid being pumped typically enters such liquid receiving cavities formed within the outer gerotor 3 while flowing in a single axial direction via the inlet opening 6 and an open end of the outer gerotor 3. As shown with respect to circumstance A, which corresponds to the gerotor pump 1 at the instant of initial start-up thereof, a magnetic force acting on the outer gerotor 3 normally urges the outer gerotor 3 and the shaft 4 to a tilted configuration where only a portion of the rim 3a of the outer gerotor 3 engages the inner face 2a of the housing wall 2. The force of the pumped liquid entering the outer gerotor 3 via the inlet opening 6 and encountering an axial end surface 3b within the outer gerotor 3 also contributes to this same tilting of the outer gerotor 3 and shaft 4 as disclosed with respect to the depiction of circumstance A. This tilting of the outer gerotor 3 further leads to frictional forces being generated between an outer surface of the shaft 4 and an inner surface of the sleeve 5, as well as the formation of an axial gap between the inner face 2a and the rim 3a towards the inlet side of the gerotor pump 1 and at a position diametrically opposite the contact point therebetween on the outlet side of the gerotor pump 1.

As explained with respect to the depiction of circumstance B, an increase in the internal pressure forces applied by the pumped liquid to the axial end surface 3b of the outer gerotor 3 leads to disengagement of the entire rim 3a from the inner face 2a when both a backpressure force against the outer gerotor 3 towards the inner face 2a and the frictional forces present between the shaft 4 and the sleeve 5 are not great enough to counteract the internal pressure forces acting opposite the backpressure and frictional forces, which can lead to a large increase to the axial gap present between the rim 3a and the inner face 2a such that pumped liquid can leak about an entirety of the rim 3a. The excessive forces of circumstance B can also lead to the shaft 4 undesirably frictionally engaging the housing portion 8 following axial movement of the shaft 4 away from the housing wall 2.

As shown with respect to the depiction of circumstance C, the back pressure applied to the outer gerotor 3 may eventually counteract the internal pressure forces to an extent necessary to partially reduce the axial gap such that reduced leaking occurs. Eventually, as shown with respect to the depiction of circumstance D1, the back pressure forces eventually overcome the internal pressure forces such that only the nominal tilt of the outer gerotor 3 contributes to the formation of a relatively small gap and to the reengagement of at least a portion of the rim 3a with the inner face 2a as the outer gerotor 3 progresses towards rotating in a more parallel arrangement, which may include the elimination of frictional forces between the shaft 4 and the inner surface of the sleeve 5. As shown throughout the remainder of the depictions of circumstances E-G, variations of the internal pressure forces resulting from entry of the pumped liquid into the cavities via the inlet opening 6 and variations in the formation of an opposing backpressure forces can result in variations to each of the tilt of the outer gerotor 3 and the maximum axial gap present between the rim 3a and the inner face 2a with respect to the different operating conditions of the gerotor pump 1 disclosed in FIG. 2, such as when operating the gerotor pump 1 from the normal operating circumstance E back towards a shut-off condition corresponding to a return to circumstance A as disclosed with respect to each of FIGS. 1 and 2.

One negative outcome associated with the outer gerotor 3 axially disengaging from the inner face 2a of the housing wall 2 is that excessive and undesirable quantities of the pumped liquid are able to leak around the rim 3a such that flow losses occur with respect to the gerotor pump 1. This effect has been discovered to be particularly evident when operating the exemplary gerotor pump 1 at relatively high speeds (>3000 rpm), at relatively low pressures (<1 bar), and with a (pumped) liquid temperature of between 20-120 degrees C. The axial disengagement of the outer gerotor 3 from the inner face 2a also leads to the potential for the outer gerotor 3 to be rotated about an axis that is tilted significantly relative to the intended axis of rotation thereof (such as shown in circumstances A, B, C, F, and E), thereby contributing to the potential for wear to occur where such surfaces are rotationally engaging one another and generating frictional forces therebetween. Such axial disengagement may also lead to wear occurring at additional locations within the gerotor pump 3, such as where the shaft 4 encounters the housing portion 8 during periods where an especially large axial gap is formed.

It would thus be desirable to provide an improved gerotor pump that includes a pressure relief feature suitable for preventing an incidence of disengagement of the outer gerotor from a corresponding seating surface and the resulting excessive leakage of the pumped liquid from the outer gerotor and/or wear of the gerotor pump via the misalignment of components resulting from such disengagement, wherein such a pressure relief feature is configured to provide such pressure relief by reducing the axially applied internal pressure forces occurring within the liquid receiving cavities formed between the inner gerotor and the outer gerotor of the improved gerotor pump.

SUMMARY OF THE INVENTION

In accordance with the present disclosure, an improved gerotor pump having a pressure relief feature has surprisingly been discovered.

According to an embodiment of the present invention, a gerotor pump includes an outer gerotor having an opening defined by an inner surface thereof, an inner gerotor received within the opening of the outer gerotor with a plurality of cavities formed between the inner gerotor and the outer gerotor, and a plurality of first pockets with each of the first pockets formed as an indentation in the inner surface of the outer gerotor. Each of the first pockets forms a first pressure relief feature for preventing an overpressure within each of the cavities formed between the outer gerotor and the inner gerotor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts several different circumstances A-G encountered within a conventional gerotor pump leading to leakage and flow loss of a pumped liquid;

FIG. 2 is a graph showing the conditions corresponding to each of the circumstances A-G depicted in FIG. 1;

FIG. 3 is an elevational cross-sectional view taken through a central plane of a gerotor pump according to an embodiment of the present invention;

FIG. 4 is a front elevational view showing a housing of the gerotor pump in isolation;

FIG. 5 is a rear elevational view of the housing of the gerotor pump;

FIG. 6 is a cross-sectional view showing an inlet opening and an outlet opening of the housing from the perspective of section lines 6-6 in FIG. 4;

FIG. 7 is an enlarged view of a portion of FIG. 5 for showing a boundary shape of the inlet opening and the outlet opening of the housing;

FIG. 8 is a right side perspective view showing an assembly of an outer gerotor and a shaft of the gerotor pump in isolation;

FIG. 9 is a front view of the assembly of FIG. 8 showing the interior surfaces of the outer gerotor;

FIG. 10 is an enlarged view of a bounded portion of the outer gerotor as identified in FIG. 9;

FIGS. 11 and 12 are each cross-sectional views of the gerotor pump taken from the perspective of section line 11, 12-11, 12 of FIG. 3, wherein FIG. 11 shows a relationship present between the outer gerotor and an inner gerotor at a first instance and FIG. 12 shows a relationship present between the outer gerotor and an inner gerotor at a second instance subsequent to the first instance;

FIGS. 13 and 14 are each cross-sectional views of the gerotor pump taken from the perspective of section line 13, 14-13, 14 of FIG. 3, wherein FIG. 13 shows a relationship present between the outer gerotor, the inner gerotor, the inlet opening of the housing, and the outlet opening of the housing at a first instance and FIG. 14 shows a relationship present between the the outer gerotor, the inner gerotor, the inlet opening of the housing, and the outlet opening of the housing at a second instance subsequent to the first instance.

DETAILED DESCRIPTION OF THE INVENTION

The following description of technology is merely exemplary in nature of the subject matter, manufacture and use of one or more inventions, and is not intended to limit the scope, application, or uses of any specific invention claimed in this application or in such other applications as may be filed claiming priority to this application, or patents issuing therefrom. Regarding methods disclosed, the order of the steps presented is exemplary in nature, and thus, the order of the steps can be different in various embodiments. “A” and “an” as used herein indicate “at least one” of the item is present; a plurality of such items may be present, when possible. Except where otherwise expressly indicated, all numerical quantities in this description are to be understood as modified by the word “about” and all geometric and spatial descriptors are to be understood as modified by the word “substantially” in describing the broadest scope of the technology. “About” when applied to numerical values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” and/or “substantially” is not otherwise understood in the art with this ordinary meaning, then “about” and/or “substantially” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters.

All documents, including patents, patent applications, and scientific literature cited in this detailed description are incorporated herein by reference, unless otherwise expressly indicated. Where any conflict or ambiguity may exist between a document incorporated by reference and this detailed description, the present detailed description controls.

Although the open-ended term “comprising,” as a synonym of non-restrictive terms such as including, containing, or having, is used herein to describe and claim embodiments of the present technology, embodiments may alternatively be described using more limiting terms such as “consisting of” or “consisting essentially of.” Thus, for any given embodiment reciting materials, components, or process steps, the present technology also specifically includes embodiments consisting of, or consisting essentially of, such materials, components, or process steps excluding additional materials, components or processes (for consisting of) and excluding additional materials, components or processes affecting the significant properties of the embodiment (for consisting essentially of), even though such additional materials, components or processes are not explicitly recited in this application. For example, recitation of a composition or process reciting elements A, B and C specifically envisions embodiments consisting of, and consisting essentially of, A, B and C, excluding an element D that may be recited in the art, even though element D is not explicitly described as being excluded herein.

As referred to herein, disclosures of ranges are, unless specified otherwise, inclusive of endpoints and include all distinct values and further divided ranges within the entire range. Thus, for example, a range of “from A to B” or “from about A to about B” is inclusive of A and of B. Disclosure of values and ranges of values for specific parameters (such as amounts, weight percentages, etc.) are not exclusive of other values and ranges of values useful herein. It is envisioned that two or more specific exemplified values for a given parameter may define endpoints for a range of values that may be claimed for the parameter. For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that Parameter X may have a range of values from about A to about Z. Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if Parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, 3-9, and so on.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

FIGS. 3-14 illustrate a gerotor pump 10 having at least one internal pressure relief feature according to an embodiment of the present invention. The gerotor pump 10 includes, as is relevant to disclosure of the present invention, a housing 11, an outer gerotor 20, an inner gerotor 40, a shaft 60, and an encasement 70. The housing 11 includes a connection wall 12 where fluid connections are established for conveying a pumped liquid to and from the gerotor pump 10. The connection wall 12 includes each of an inlet opening 16 and an outlet opening 17 formed therethrough with each of the openings 16, 17 extending to an inner face 12a of the connection wall 12. A shaft sleeve 13 extends axially inwardly from the inner face 12a and forms a cylindrical opening 13a for rotatably receiving a first end portion of the cylindrically shaped shaft 60 therein. As can be understood with reference to the isolated views of a (front) segment of the housing 11 that includes formation of the connection wall 12 at a front end thereof in FIGS. 4-7, the inlet opening 16 is formed to a first diametric side of the sleeve 13 and the outlet opening 17 is formed to an opposing second diametric side of the sleeve 13. The spacing of the openings 16, 17 is accordingly in a lateral direction of the gerotor pump 10 that would be in a direction extending into the page with respect to the cross-sectional view of FIG. 3, which shows a perspective from a plane disposed directly between the openings 16, 17 with respect to said lateral direction. The orientation of the openings 16, 17 relative to the remainder of the gerotor pump 10 is also evident with respect to the depiction of a method of operation of the gerotor pump 10 as shown in FIGS. 13 and 14, which are described in greater detail hereinafter.

The encasement 70 is substantially cylindrical in shape and includes an open axial end forming a rim 70a configured to extend to and engage the inner face 12a of the connection wall 12. The encasement 70 defines a hollow opening within the gerotor pump 10 that receives each of the outer gerotor 20, the inner gerotor 40, and the shaft 60 therein, wherein the hollow opening is delimited axially by the inner face 12a at the open end of the encasement 70 and by the inner surface of the encasement 70 along a closed axial end thereof. The closed axial end of the encasement 70 may include a shaft opening 72 configured to rotatably receive a second end portion of the shaft 60 opposite the rotatable reception of the shaft 60 within the shaft sleeve 13.

The outer gerotor 20 is divisible axially into a fluid receiving portion 21 and a drive component portion 22, each of which is substantially cylindrical in shape. The fluid receiving portion 21 is formed by an axial end portion of the outer gerotor 20 that is open ended and configured to face towards and cover the inlet opening 16 and the outlet opening 17 at the inner face 12a of the connection wall 12 to allow the pumped liquid to flow axially into and out of the fluid receiving portion 21 via passage through the connection wall 12. The open axial end of the fluid receiving portion 21 forms a rim 23 of the outer gerotor 20 configured to normally face towards and engage the inner face 12a of the connection wall 12 at positions surrounding the inlet and outlet openings 16, 17. The drive component portion 22 includes components associated with operation of a drive mechanism 99 configured to drive rotation of the gerotors 20, 40, wherein the drive mechanism 99 may include electrical and/or magnetic components corresponding to a conventional electric motor assembly or the like that operates in conventional fashion, hence specific description of the drive mechanism 99 is omitted herefrom. It should also be understood that the drive mechanism 99 need not necessarily have the form of an electric motor to remain within the scope of the present invention as the beneficial relationships disclosed herein are not dependent on the method of driving the gerotor pump 10. That is, any drive mechanism for driving the engagement between the gerotors 20, 40 in the manner described may be within the scope of the present invention.

A backpressure chamber 75 is formed between an outer axial end surface of the outer gerotor 20 and an inner axial end surface of the encasement 70. The backpressure chamber 75 is configured to receive portions of the pumped liquid that either leak from the outer gerotor 20 or that are communicated to the backpressure chamber 75 via one or both of an inlet orifice 18 and/or an outlet orifice 19. In the present embodiment, the inlet orifice 18 is formed by an opening through the connection wall 12 positioned radially between the rim 70a of the encasement 70 and the rim 23 of the outer gerotor 20 to fluidly communicate with the cylindrical shape formed therebetween while the outlet orifice 19 is formed by an opening through the housing 11 that extends from a surface defining the outlet opening 17, through the connection wall 12, and to a position between the rim 23 of the outer gerotor 20 and the rim 70a of the encasement 70. Although the outlet orifice 19 is not directly shown relative to the positions of the rims 23, 70a, it should be apparent from a review of FIGS. 4-7 that the orifices 18, 19 are equally spaced apart from a central axis of the outer gerotor 20 and hence would both be positioned relative to the rims 23, 70a in the same manner as depicted with respect to the inlet orifice 18 in FIG. 3. The liquid received within the backpressure chamber 75 applies a pressure force to the outer gerotor 20 in a direction urging the rim 23 thereof towards the inner face 12a of the connection wall 12, thereby preventing a leakage of liquid around the rim 23.

The outer gerotor 20, and more specifically the fluid receiving portion 21 thereof, includes an opening formed by an inner surface of the fluid receiving portion 21. The inner surface of the fluid receiving portion 21 is formed by the cooperation of an inner circumferential surface 24 and a base surface 28 thereof. The inner circumferential surface 24 extends circumferentially about a perimeter of the fluid receiving portion 21 and extends in an axial direction of the outer gerotor 20 from the rim 23 thereof to the base surface 28 of the outer gerotor 20. The base surface 28 is arranged perpendicular to the axial direction of the outer gerotor 20 and faces towards and is arranged opposite the inner face 12a of the connection wall 12. The inner circumferential surface 24 is circumferentially toothed to include a corrugated profile shape including an alternating arrangement of teeth 25 and notches 26 in the circumferential direction thereof, wherein each of the teeth 25 extends radially inwardly away from a substantially cylindrically contoured segment of the inner circumferential surface 24 curving about a central axis of the outer gerotor 20 and each of the notches 26 is formed by one of the substantially cylindrically contoured segments disposed between adjacent ones of the teeth 25. Each of the teeth 25 may include an arcuate shape of a segment of a circle, as desired, as each of the teeth extends radially inwardly from the cylindrical contours forming the notches 26. However, alternative corrugated gear-like configurations of the teeth 25 and the notches 26 from those shown and described may be utilized in forming the inner circumferential surface 24 while remaining within the scope of the present invention.

The inner gerotor 40 is received within the opening of the outer gerotor 20 and extends axially from a first axial end surface 41 configured to face towards and engage the inner face 12a of the connection wall 12 to a second axial end surface 42 configured to face towards and engage the base surface 28 of the outer gerotor 20. Each of the axial end surfaces 41, 42 may be substantially planar in configuration. The inner gerotor 40 further includes an outer circumferential surface 43 connecting the axial end surfaces 41, 42 to one another about a periphery of the inner gerotor 40. The outer circumferential surface 43 is configured to engage the inner circumferential surface 24 of the outer gerotor 20 during rotation of the gerotors 20, 40 via a gear-like transfer of rotational motion. The outer circumferential surface 43 is circumferentially toothed to include a corrugated profile shape including an alternating arrangement of teeth 45 and notches 46 in the circumferential direction thereof, wherein each of the teeth 45 extends radially outwardly relative to either of two adjacent and straddling notches 46. Each of the teeth 45 includes a profile shape substantially similar to that of each of the notches 26 of the outer gerotor 20 while each of the notches 46 includes an arcuate profile shape substantially similar to that of each of the teeth 25 of the outer gerotor 20. The teeth 45 of the outer gerotor 40 may include a shape that is substantially identical to each of the notches 26 with the exception of a radially outermost portion thereof being truncated such that a radial spacing is present between the radially outermost surface of each of the notches 26 and the radially outermost surface of each of the teeth 45 as each of the teeth 45 is received within each of the notches 26 to a maximum extent, thereby allowing for a relatively small flow space to remain present between the teeth 45 and the notches 26 even upon maximum insertion therein.

The axis of rotation of the outer gerotor 20 is defined by the central axis of the shaft 60 while the axis of rotation of the inner gerotor 40 is defined by the central axis of a cylindrically shaped outer circumferential surface 13b of the sleeve 13 such that the axes of rotation of the outer and inner gerotors 20, 40 are offset from one another in a direction perpendicular to the directions of extension of said axes, which is the vertical direction as depicted in the present figures. The inner gerotor 40 also includes one fewer of the teeth 45 than the number of the teeth 26 included in the outer gerotor 20, which in combination with the offset axes of the gerotors 20, 40 presents the ability to form variably shaped and sized cavities 55 between the inner circumferential surface 24 of the outer gerotor 20 and the outer circumferential surface 43 of the inner gerotor 40 during the rotation of each of the gerotors 20, 40, thereby causing a pumping action of the gerotor pump 10 during unified rotation of both of the gerotors 20, 40 relative to the housing 11.

As can be seen by comparison of FIGS. 11 and 12, which show the gerotors 20, 40 at a first instance (FIG. 11) and then at a second instance (FIG. 12) following a slight degree of rotation of each of the gerotors 20, 40 in the identified direction (clockwise from the illustrated perspective between the first instance and the second instance) during typical operation of the gerotor pump 10, rotation of each of the gerotors 20, 40 results in one of the cavities 55 formed towards the inlet opening 16 including one of the teeth 45 of the inner gerotor 40 being removed from inside a corresponding one of the notches 26 of the outer gerotor 20 such that the corresponding cavity 55 expands in size to allow for the liquid being pumped to flow through the inlet opening 16 and into the cavity 55 in an axial direction. As this cavity 55 progresses towards the lateral side of the gerotor pump 10 having the outlet opening 17 via circumferential movement of the cavity 55 about the periphery of the inner circumferential wall 24, one of the teeth 45 of the inner gerotor 40 starts to enter and substantially fill one of the notches 26 of the outer gerotor 20 in a manner compressing and pressurizing the liquid contained within the corresponding cavity 55. This compressed liquid is then able to escape the cavity 55 via axial flow beyond the rim 23 of the outer gerotor 20 and then passage of the pressurized liquid through the outlet opening 17 of the connection wall 12 where the outlet opening 17 intersects the inner face 12a.

As described in the background section of the present disclosure, the process of compressing the liquid being pumped within such cavities 55 can lead to circumstances where the internal pressure forces resulting from the compression of the liquid can disengage the rim 23 of the outer gerotor 20 from the inner face 12a of the connection wall 12 as such forces act in a direction away from the connection wall 12 and against the backpressure generated within the backpressure chamber 75. This can lead to excessive leakage of the pumped liquid past the rim 23 in a manner reducing the flow rate through the gerotor pump 10. As a solution to this concern, the present invention is characterized by inclusion of at least one pressure relief feature within the gerotor pump 10 whereby a maximized pressure occurring within each of the cavities 55 formed between the gerotors 20, 40 can be beneficially reduced via the formation of additional volumes and/or pressure equalizing flow paths for the compressed liquid to occupy and/or flow through within the gerotor pump 10.

According to a first pressure relief feature, the base surface 28 of the outer gerotor 20 includes a plurality of pockets 30 formed therein. As can be seen in FIG. 3, each of the pockets 30 is formed as an axially indented portion of the base surface 28, which in the present embodiment includes each of the pockets 30 being axially indented into the base surface 28 towards the backpressure chamber 75 relative to an adjacent planar surface of the base structure 28 engaging the second axial end surface 42 of the inner gerotor 40 such that the surface forming each of the pockets 30 is spaced apart from and does not directly engage the second axial end surface 42 of the inner gerotor 40 during movement of the gerotors 20, 40 relative to one another. The distance of the axial indenting of the pockets 30 relative to the adjacent planar surface of the base surface 28 may be about 4 mm, as one non-limiting example. Each of the pockets 30 may include a perimeter shape and size suitable for allowing a portion of the liquid contained within each of the cavities 55 to flow, at some point in the progression of the corresponding cavity 55 around the periphery of the outer gerotor 20 as caused by the relative movement present between the inner and outer gerotors 20, 40, into an adjacent one of the cavities 55 via passage along and through one of the pockets 30 between the second axial end surface 42 of the inner gerotor 20 and the indented surface defining the corresponding pocket 30 along the base surface 28 that is axially spaced apart from the second axial end surface 42.

Each of the pockets 30 may be generally associated with a corresponding one of the notches 26 and may thus extend to cover a majority or an entirety of the base surface 28 at the corresponding one of the notches 26, which may refer to the corresponding pocket 30 covering the majority or the entirety of a portion of the base surface 28 disposed radially outwardly of the radially outermost surface of each of the teeth 45 when fully received within the corresponding one of the notches 26. A boundary of the each of the pockets 30 may extend along the inner circumferential surface 24 along a majority or an entirety of the corresponding one of the notches 26, and may further extend along the inner circumferential surface 24 to extend along at least a portion of each of the teeth 25 straddling the corresponding one of the notches 26 to either circumferential side thereof. The boundary of each of the pockets 30 extending along such features may include the boundary extending directly along the intersection of the base surface 28 with the inner circumferential surface 24 or may include the boundary indented inwardly from the inner circumferential surface 24 along the base surface 28 at an offset while extending along the same general shape as the inner circumferential surface 24. A connecting portion of the boundary of each of the pockets 30 may extend away from extending along the inner circumferential surface 24 to connect the opposing ends of the boundary that extend along the inner circumferential surface 24 to one another across the base surface 28 between adjacent ones of the teeth 25.

As depicted herein, each of the pockets 30 may include a shape comprising a leading portion 30a and a trailing portion 30b, wherein the leading portion 30a refers to a portion of each of the pockets 30 that leads in the circumferential direction during rotation of the outer gerotor 20 while the trailing portion 30b conversely refers to a portion of each of the pockets 30 that trails the associated leading portion 30a in the circumferential direction during rotation of the outer gerotor 20. Each of the pockets 30 may be divided into the leading and trailing portions 30a, 30b by a radially extending axis that passes through a center of the corresponding one of the notches 26, which is shown from the perspective of FIG. 11 to include the leading portion 30a clockwise of the dividing axis and the trailing portion 30b counterclockwise of the dividing axis with respect to one of the pockets 30 identified at the top of the depiction of the outer gerotor 20. FIG. 11 also shows that the connecting portion of the boundary of each of the pockets 30 may be biased such that the connecting portion progressively extends radially inwardly with respect to a central axis of the outer gerotor 20 as the connecting portion extends circumferentially from a leading end to a trailing end of the corresponding one of the pockets 30. This biasing of the connecting portion may include the connecting portion intersecting the inner circumferential surface along the leading portion 30a at a position along the corresponding tooth 25 that is displaced from both a peak of the corresponding tooth 25 and the notch 26 associated with the corresponding pocket 30 and the connecting portion intersecting the inner circumferential surface along the trailing portion 30b at a position of the peak of the trailing tooth 25.

The connecting portion is also depicted as being substantially L-shaped with an offset segment extending radially inwardly from the peak of the trailing tooth 25 and a cross segment extending from the offset segment to the position along the leading tooth 25 offset from the peak thereof. This radial inward indenting of the cross segment from the peak of the trailing tooth 25 via introduction of the offset segment may be included to ensure that a radial dimension of the pocket 30 at the trailing end thereof, which corresponds to the width of a circumferentially extending flow path along the pocket 30 from one cavity 55 to another as each of the teeth 45 of the outer gerotor 40 first uncover the trailing portion 30b of the pocket 30, is great enough to allow for the rapid flow of the pumped liquid between the cavities 55 upon the pocket 30 initially being placed in direct fluid communication with both adjoining cavities 55. The clockwise-most identified pocket 30 in FIG. 11 is shown where the trailing portion 30b is first uncovered and where the radial extension of the offset segment leads to the pocket 30 having an increased mouth width and hence flow area therethrough in comparison to the uncovering of an expanding cross-section as may be provided by a pointed or triangular shape being uncovered initially.

As can be seen in FIGS. 11 and 12, each of the pockets 30 is shaped to extend across an area of the base surface 28 where at least one position of each of the teeth 45 of the inner gerotor 40 relative to each of the notches 26 of the outer gerotor 20 includes the pumped liquid being able to be communicated between one of the cavities 55 instantaneously overlapped with and directly fluidly coupled to the leading portion 30a of the corresponding one of the pockets 30 and another adjacent one of the cavities 55 instantaneously overlapped with and directly fluidly coupled to the trailing portion 30b of the corresponding one of the pockets 30. It should also be apparent that at least some positions of each of the teeth 45 of the of the inner gerotor 40 relative to each of the notches 26 of the outer gerotor 20 will include a corresponding one of the pockets 30 directly fluidly coupled to only one of the cavities 55 at a given instant, such as when a corresponding tooth 45 is first encountering or completing passage beyond a corresponding one of the pockets 30 at the leading or trailing ends thereof. An example of this circumstance is shown with respect to the top-most identified pocket 30 of FIG. 11 where one of the teeth 45 has only begun to pass over the trailing portion 30b of the pocket 30 such that fluid communication can not yet be established past the second axial end surface 42 of the inner gerotor 40.

As can be seen by review of FIGS. 11 and 12, each of the cavities 55 is always in direct fluid communication with at least one of the pockets 30 regardless of the rotational position of the outer gerotor 20 relative to the inner gerotor 40, and at other instances in direct fluid communication with two of the pockets 30 with respect to some rotational positions of the outer gerotor 20 relative to the inner gerotor 40. In fact, in limited circumstances the disclosed configuration of the pockets 30 includes the pumped liquid being capable of fluid communication from a first cavity 55 to a second cavity 55 via a first pocket 30 and then from the second cavity 55 to a third cavity 55 via a second pocket 30, such as is shown as being the case with respect to the three pockets 30 disposed to the right half of the outer gerotor 20 as depicted in FIG. 11. The disclosed pockets 30 are accordingly capable of providing pressure equalization across as many as three of the cavities 55 when encountering such limited circumstances.

The inclusion of the pockets 30 in the outer gerotor 20 reduces the maximum pressure experienced within each of the cavities 55 by forming an extra volume for the liquid to occupy while also providing an additional flow path for the liquid to flow through when progressing to another of the cavities 55 having a lower pressure than that instantaneously experienced in the cavity 55 from which the liquid is escaping by way of the intervening and connecting pocket 30. Each of the pockets 30 can accordingly aid in lowering the described internal pressure at times when adjacent cavities 55 are positioned to be fluidly coupled to one another via a corresponding one of the pockets 30 extending therebetween as well as at times where the corresponding one of the pockets 30 is positioned relative to the inner gerotor 40 such that the corresponding one of the pockets 30 primarily relies upon the expanded flow volume provided by the inclusion of the corresponding one of the pockets 30 within the outer gerotor 20 in lowering the internal pressure relative to a circumstance where the outer gerotor 20 is devoid of such pockets 30. The cavity 55 from which the liquid is escaping by way of the corresponding one of the pockets 30 may accordingly not experience an undesirably high internal pressure consistent with separation of the outer gerotor 20 from the inner face 12a of the connection wall 12 and corresponding leakage of the liquid from the outer gerotor 20 throughout each incidence of one of the teeth 45 compressing the pumped liquid relative to one of the notches 26 via a corresponding cavity 55 formed therebetween.

According to a second pressure relief feature of the present invention, each of the notches 26 formed between adjacent ones of the teeth 25 of the outer gerotor 20 may further include the formation of a pocket 35 therein. Each of the pockets 35 may be formed by a portion of the inner circumferential surface 24 of the outer gerotor 20 that is indented radially outwardly along a corresponding one of the notches 26 relative to an adjacent and axially extending surface of the same one of the notches 26 to expand the flow volume of a corresponding one of the cavities 55 in the radial outward direction. Each of the pockets 35 thus forms a portion of the circumferential surface 24 that does not contact one of the teeth 45 of the inner gerotor 40 due to each of the pockets 35 being disposed radially outwardly of the teeth 45 under all circumstances. That is, each of the notches 26 includes a radially outwardly disposed first portion formed by one of the pockets 35 and a radially inwardly disposed second portion devoid of the formation of one of the pockets 35, wherein the first portion having the one of the pockets 35 includes a larger inner (root) radius from the axis of rotation of the outer gerotor 20 than does the second portion devoid of one of the pockets 35, which is thus more closely spaced to the teeth 45 of the inner gerotor 40 than the surface defining the adjacent pocket 35 with respect to the radial direction of the outer gerotor 20. Each of the pockets 35 extends axially from the rim 23 of outer gerotor 20 towards the base surface 28 before terminating therebetween and transitioning radially inwardly to the configuration of the remainder of the corresponding notch 26, hence each of the notches 26 includes the relatively enlarged radial dimension towards the rim 23 and a relatively reduced radial dimension towards the base surface 28. In the present embodiment, each of the pockets 35 transitions to the second portion of the corresponding one of the notches 26 devoid of one of the formation of one of the pockets 35 about halfway between the base surface 28 and the rim 23 with respect to the axial direction of the outer gerotor 20. However, the pockets 35 may extend along different axial lengths of the inner circumferential surface 24 while remaining within the scope of the present invention, as desired.

As shown in FIG. 7, which is an enlarged view of the connection wall 12 showing the inner face 12a thereof, the formation of the pockets 35 in the outer gerotor 20 may be coupled with the inclusion of a radially outwardly expanded portion 17a of a periphery of the outlet opening 17 where the outlet opening 17 intersects the inner face 12a of the connection wall 12. The periphery of the outlet opening 17 includes a radially outer side that, when progressing in a counter-clockwise direction from an upper end of the outlet opening 17 at depicted in FIG. 7, includes a first portion having a constant radius of curvature relative to the central axis of the outer gerotor 20 that then transitions radially outwardly at an offset in forming the radially outwardly expanded portion 17a along a second portion, which in the depicted embodiment also continues in the counter-clockwise direction to include its own constant radius of curvature that is larger than that of the remainder of the boundary of the outlet opening 17 relative to the central axis of the outer gerotor 20. The radially outwardly expanded portion 17a is indented radially outwardly beyond a radially outermost surface of each of the second portions of the notches 26 devoid of one of the pockets 35 relative to the axis of rotation of the outer gerotor 20. The radially outwardly expanded portion 17a extends radially outwardly to an extent overlapping the expanded portion 17a with an axial end of each of the pockets 35 disposed along the rim 23 of the outer gerotor 20, thereby allowing for liquid to flow directly from within one of the pockets 35 to within the outlet opening 17 in the axial direction once the corresponding pocket 35 reaches the radially outwardly expanded portion 17a of the periphery of the outlet opening 17 during circumferential movement thereof as occurs during rotation of the gerotors 20, 40.

This effect can most easily be understood by comparison of FIGS. 13 and 14, which are cross-sectional views taken immediately adjacent the inner face 12a of the connection wall 12 to show the shape of the boundary of each of the inlet opening 16 and the outlet opening 17 at the inner face 12a and relative to the formation and subsequent compression of the cavities 55 formed between the inner and outer gerotors 20, 40. In FIG. 13, one of the pockets 35 (shown in outline via broken lines) is axially aligned with a portion of the inner face 12a of the connection wall 12 for blocking direct axial flow into the outlet opening 17 from the pocket 35 while in FIG. 14 the same one of the pockets 35 has orbited (clockwise) to a position where the liquid contained within the pocket 35 can flow directly axially from the pocket 35 and across the boundary of the outlet opening 17 due to the radial outward extension of the periphery thereof, as caused by the formation of the expanded portion 17a to the radial position of the pocket 35.

Each of the pockets 35 accordingly provides both an additional flow volume for receiving additional liquid and a flow path for allowing a portion of the liquid being compressed along the outlet opening 17 side of the gerotor pump 10 to escape the corresponding cavity 55 and leak to the outlet opening 17 when the maximum degree of compression of the liquid is occurring as one of the teeth 45 is maximally received within one of the notches 26. The presence of the pockets 35 accordingly reduces the pressure experienced within the outer gerotor 20 by allowing an increased portion of the liquid to flow out of each cavity 55 during the compression of the liquid therein while also providing an increased volume for generally reducing the pressure of the liquid while passing through the outer gerotor 20.

FIG. 7 also shows the periphery of the outlet opening 17 as having a radially inwardly expanded portion 17b that is intended radially inwardly further than a remainder of the inner periphery of the outlet opening 17 extending along and around the sleeve 13 receiving the shaft 60, wherein the remainder of the inner periphery otherwise includes a constant radius of curvature greater than that of the radially inwardly expanded portion 17b. The radially inwardly expanded portion 17b is positioned at or adjacent the completion of the compression of each of cavities 55 for receiving the pumped liquid when at a relatively high pressure. This radially inward indenting results in a flow area through the outlet opening 17 being increased where the pressure of the liquid is maximized, thereby allowing for the liquid to exit the outer gerotor 20 more quickly such that excessive pressure does not build-up at the end of each compression cycle in a manner contributing to the formation of excessive internal pressures within the gerotor pump 10.

Simulations preformed with respect to the gerotor pump 10 of the present invention having the formation of the pockets 30, 35 therein results in the gerotor pump 10 encountering significantly reduced internal pressures in comparison to the same gerotor pump devoid of such features with respect to typical operating conditions. As such, the gerotor pump 10 of the present invention beneficially aids in preventing an incidence of disengagement of the outer gerotor 20 from the inner face 12a of the connection wall 12 where the pumped liquid may undesirably flow past the rim 23 of the outer gerotor 20. The gerotor pump 10 as disclosed also avoids instances where the outer gerotor 20 is excessively tilted relative to the guidance provided by features such as the sleeve 13, thereby preventing the generation of wear as a result of the undesirable frictional engagement present between such surfaces during rotation of the outer gerotor 20.

The gerotor pump 10 is depicted throughout the present figures as including both the pockets 30 and the pockets 35 in combination, but it should be apparent that the gerotor pump 10 may be provided to utilize only one of the pockets 30, 35 while remaining within the scope of the present invention since the pressure reducing features provided by either of the pockets 30, 35 are not dependent on the presence of the other of the pockets 30, 35 as described herein. That is, the advantages of the pockets 30 may be appreciated in the absence of the pockets 35, and likewise the advantages of the use of the pockets 35 (along with appropriate modifications to the structure of the outlet opening 17) may be appreciated in the absence of the pockets 30.

From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.