EP4689398A1

EP4689398A1 - Assemblies for an internal gear pump with hydrostatic support features

Info

Publication number: EP4689398A1
Application number: EP24707389.3A
Authority: EP
Inventors: Hao Zhang; Federico Zappaterra; Satish Kumar Raju Kalidindi; Andrea Vacca; Hassan ASSAF
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 2023-03-30
Filing date: 2024-01-18
Publication date: 2026-02-11
Also published as: CN121039396A; WO2024205694A1; KR20250165416A; JP2026511867A

Abstract

An example gear pump includes a pump housing comprising a hydrostatic groove; an outer bushing mounted to the pump housing and comprising a hydrostatic slit that is fluidly coupled to the hydrostatic groove of the pump housing; a drive flange mounted to the outer bushing such that outer bushing is interposed radially between the pump housing and the drive flange; a ring gear coupled to the drive flange and configured to rotate therewith; and a pump pinion disposed within the ring gear, such that external teeth of the pump pinion engage with internal teeth of the ring gear to draw and discharge fluid as they rotate, wherein fluid is provided to the hydrostatic groove of the pump housing and communicated through the hydrostatic slit to an interface between the drive flange and the outer bushing to facilitate rotation of the drive flange relative to the pump housing.

Description

Assemblies for an Internal Gear Pump with Hydrostatic Support Features

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63/493,003, filed on March 30, 2023, the entire contents of which are herein incorporated by reference as if fully set forth in this description.

BACKGROUND

[0002] A gear pump uses the meshing of gears to pump fluid by displacement. There are two main variations: external gear pumps, which use two external spur gears, and internal gear pumps, which use an external (e.g.. pinion) and internal (e.g., ring) spur gears. Gear pumps have fixed displacement, where the pump can provide a constant amount of fluid for each revolution.

[0003] As the gears of the pump rotate, their teeth separate on the intake side of the pump, creating a void and suction, and the void is then filled by fluid. The fluid is carried by the gears to the discharge or outlet side of the pump, where the meshing of the gears displaces the fluid under pressure. In some cases, high pressure fluid at the outlet side of the pump may push the ring gear of an internal gear pump toward a housing of the pump, thereby increasing the likelihood of wear due to friction. It may thus be desirable to counter the force applied by the high pressure fluid on the gear to reduce wear.

[0004] In examples, an electric motor can be used to drive the pump. In these examples, it may be desirable to have an assembly that integrates the pump and the electric motor. This way, mechanical components, such as shafts, bearing, etc., can be shared between hydraulic pump and the motor. It is with respect to these and other considerations that the disclosure made herein is presented. SUMMARY

[0005] The present disclosure describes implementations that relate to assemblies for an internal gear pump with hydrostatic support features.

[0006] Particularly, the present disclosure describes an internal gear pump supported by hydrostatic journal bearing or bushings, and having hydrostatic features embedded in the bushings to enhance the support of an off-center load, improving the efficiency of the pump.

[0007] In an example implementation, the gear pump is integrated with an electric motor in an assembly. The bushings configuration may enhance the integration between the gear pump and the electric motor, saving space and reducing the number of components of the assembly.

[0008] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become apparent by reference to the figures and the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES

[0009] The novel features believed characteristic of the illustrative examples are set forth in the appended claims. The illustrative examples, however, as well as a preferred mode of use, further objectives and descriptions thereof, will best be understood by reference to the following detailed description of an illustrative example of the present disclosure when read in conjunction with the accompanying Figures.

[0010] Figure 1 illustrates a perspective view of a gear pump, in accordance with an example implementation.

[0011] Figure 2 illustrates a cross-sectional side view of the gear pump of Figure 1, in accordance with an example implementation.

[0012] Figure 3 illustrates a perspective exploded view of the gear pump of Figure 1, in accordance with another example implementation.

[0013] Figure 4 illustrates another cross-sectional view of the gear pump of Figure 1, in accordance with an example implementation.

[0014] Figure 5 illustrates a perspective view of a first end cover, in accordance with an example implementation.

[0015] Figure 6 illustrates a perspective view of the first end cover of Figure 5 with a first outer bushing mounted to a cylindrical protrusion of the first end cover, in accordance with an example implementation.

[0016] Figure 7 illustrates a perspective partial cross-sectional view of the first end cover of Figure 6, in accordance with an example implementation. [0017] Figure 8 illustrates a perspective view of a cylindrical protrusion of a second end cover and a second outer bushing during a first mode of operation, in accordance with an example implementation.

[0018] Figure 9 illustrates a perspective view of the cylindrical protrusion and the second outer bushing of Figure 8 during a second mode of operation, in accordance with an example implementation.

[0019] Figure 10 illustrates a perspective view of a second end cover, in accordance with an example implementation.

[0020] Figure 11 illustrates a cross-sectional side view of an assembly of the gear pump of Figure 1 and an electric motor integrated therewith, in accordance with an example implementation.

[0021] Figure 12 illustrates a perspective exploded view of the assembly of Figure 11, in accordance with an example implementation.

DETAILED DESCRIPTION

[0022] The present disclosure relates to gear pump with bushings with hydrostatic features such that the bushings operate as hydrostatic bearings. The disclosure also relates to integrating the gear pump and an electric motor to have an assembly providing a compact configuration that reduces cost by sharing components, saves space, and enhances reliability.

[0023] Figure 1 illustrates a perspective view of a gear pump 100, Figure 2 illustrates a cross- sectional side view of the gear pump 100, and Figure 3 illustrates a perspective exploded view of the gear pump 100, in accordance with an example implementation. Figures 1-3 are described together.

[0024] The gear pump 100 has a assembly housing 102 that is mounted or interposed between a first end cover 104 (e.g., a front cover) and a second end cover 106 (e.g., a rear cover). The assembly housing 102 is generally cylindrical in shape and defines an internal chamber 103 therein that includes components of the gear pump 100 as shown in Figure 2.

[0025] The assembly housing 102 has a flange 108 that can be coupled to the first end cover 104 via a plurality of fasteners such as fastener 109 (e.g., a socket-head bolt). Similarly, the second end cover 106 can be coupled to the housing via a respective plurality of fasteners such as fastener 110.

[0026] Further, as shown in Figure 1, the first end cover 104 can have ears such as ear 111 through which fasteners such as fastener 112 can be disposed. Fasteners such as the fastener 112 can be used to mount or couple the gear pump 100 to a frame of a machine, for example. The second end cover 106 can have a first port 114, a second port 116, and a drain port 118.

[0027] Referring to Figures 2-3, the first end cover 104 has a cylindrical protrusion 120 that extends axially or longitudinally within the assembly housing 102. The second end cover 106 also has a cylindrical protrusion 122 that extends axially or longitudinally within the assembly housing 102 toward the cylindrical protrusion 120 of the first end cover 104. In other example implementations, the cylindrical protrusions 120, 122 can be separate components that are mounted to their respective end cover. The cylindrical protrusions 120, 122 face each other and form a space therebetween in which components of the gear pump 100 are disposed, such that the cylindrical protrusions 120, 122 embrace or sandwich such components of the gear pump 100. This way, the cylindrical protrusions 120, 122 are configured as a pump housing 123.

[0028] The cylindrical protrusion 120 has an annular groove or recess that accommodates a first outer bushing 124. Similarly, the cylindrical protrusion 122 has an annular groove or recess that accommodates a second outer bushing 126.

[0029] The gear pump 100 further includes a drive flange 128 that is generally cylindrical in shape. The gear pump 100 also includes a ring gear 130 that is interposed between the cylindrical protrusions 120, 122. In one example, the ring gear 130 is integrated with the drive flange 128 such that the ring gear 130 and the drive flange 128 are formed as one component. In another example, the ring gear 130 can be a separate components that is coupled to the drive flange 128 (e.g., via a key-keyway arrangement, a spline arrangement, a self-holding taper arrangement, etc.).

[0030] As depicted in Figure 2, the first outer bushing 124 is interposed radially between an exterior peripheral surface of the cylindncal protrusion 120 and an interior peripheral surface of the drive flange 128. Similarly, the second outer bushing 126 is interposed radially between an exterior peripheral surface of the cylindrical protrusion 122 and the interior peripheral surface of the drive flange 128. As described in more detail below, the outer bushings 124, 126 operate as bearings that support rotation of the drive flange 128 and the ring gear 130 with minimal friction. [0031] As shown in Figure 3, the ring gear 130 has internal teeth 131 formed on an interior peripheral surface thereof. Referring to Figures 2-3 together, the gear pump 100 has a pump shaft 132 to which a pump pinion 134 (e.g., a spur gear having external teeth 135 formed in an exterior peripheral surface thereol) is mounted to or integrated.

[0032] The external teeth 135 of the pump pinion 134 engage with the internal teeth 131 of the ring gear 130. Further, the pump pinion 134 is mounted off-center relative to the ring gear 130, i.e., a center of rotation of the pump pinion 134 is eccentric relative to or offset from a respective center of rotation of the ring gear 130.

[0033] The cylindrical protrusion 120 has a through-hole 137 that accommodates the pump shaft 132, and a first inner bushing 136 is interposed radially between an exterior peripheral surface of the pump shaft 132 and an interior peripheral surface of the cylindrical protrusion 120 bounding the through-hole 137. Similarly, the cylindrical protrusion 122 has hole or cavity 141 that accommodates the other end of the pump shaft 132, and a second inner bushing 138 is interposed radially between the exterior peripheral surface of the pump shaft 132 and an interior peripheral surface of the cylindrical protrusion 122 bounding the cavity 141.

[0034] As described in more detail below, the inner bushings 136, 138 operate as bearings that support rotation of the pump shaft 132 with minimal friction. As the pump shaft 132 is disposed off-center from the ring gear 130, the inner bushings 136, 138 (which support the pump shaft 132) are disposed off-center relative to the outer bushings 124, 126 (which support the drive flange 128).

[0035] The cylindrical protrusion 120 includes a drain passage 139, and the cylindrical protrusion 122 includes a drain passage 140. The drain passage 139 can fluidly couple the first inner bushing 136 to fluid volumes within the cylindrical protrusion 120 to prevent stagnation of the fluid involved in supporting the first inner bushing 136, which supports rotation of the pump shaft 132 and the pump pinion 134. The drain passage 140 similarly can fluidly couple the second inner bushing 138 to fluid volumes within the cylindrical protrusion 122 to prevent stagnation of the fluid involved in supporting the second inner bushing 138, which supports rotation of the pump shaft 132 and the pump pinion 134.

[0036] The ring gear 130 and the pump pinion 134 are supported axially within the assembly housing 102 via (i) a first thrust plate 142 disposed on one side of the ring gear 130 and the pump pinion 134, and (ii) a second thrust plate 144 on the other side of the ring gear 130 and the pump pinion 134. As such, the pump pinion 134 and the ring gear 130 are interposed or sandwiched between the thrust plates 142. 144. As described below, the thrust plates 142, 144 can operate as axial compensator that may reduce leakage within the gear pump 100 and improve its efficiency.

[0037] The thrust plates 142, 144 are in turn supported by the cylindrical protrusion 120 and the cylindrical protrusion 122. Particularly, the thrust plate 142 interfaces with the cylindrical protrusion 120, and the thrust plate 144 interfaces with the cylindrical protrusion 122. The term “interface” is used herein to indicate a point, plane, or space (or a portion of the plane or space) where two components meet and interact (e.g., where the thrust plates 142, 144 meet and interact with the cylindrical protrusions 120, 122, respectively). The thrust plates 142, 144 are configured as floating components that can move axially as described below to make up for any axial clearances and reduce internal leakage within the gear pump 100.

[0038] With this configuration, components of the gear pump 100 are interposed between and supported by the cylindrical protrusions 120, 122 of the end covers 104. 106. As depicted in Figures 2-3, the thrust plates 142. 144 include respective through-holes to accommodate the pump shaft 132 therethrough. [0039] Figure 4 illustrates another cross-sectional view of the gear pump 100, in accordance with an example implementation. The plane along which the cross section of Figure 4 is taken can be perpendicular to the plane along which the cross section of Figure 2 is taken, for example.

[0040] Referring to Figures 3-4 together, the cylindrical protrusionl20 has a first fluid cavity 146 and a second fluid cavity 148. The fluid cavities 146, 148 extend axially in the cylindrical protrusion 120. In an example, the fluid cavities 146, 148 are kidney-shaped when looking at the cylindrical protrusion 120 in a longitudinal direction, as shown in Figure 3.

[0041] Similarly, the cylindrical protrusion 122 has a first fluid cavity 150 and a second fluid cavity 152. The fluid cavities 150, 152 extend axially in the cylindrical protrusion 120. In an example, the fluid cavities 150, 152 can also be kidney-shaped.

[0042] Further, the thrust plates 142, 144 can have respective fluid passages aligned respectively with the fluid cavities 146-152. Particularly, the first thrust plate 142 can have a fluid passage 154 aligned with the first fluid cavity 146 of the cylindrical protrusion 120 and the first fluid cavity 150 of the cylindrical protrusion 122. The first thrust plate 142 also can have a fluid passage 156 aligned with the second fluid cavity 148 of the cylindrical protrusion 120 and the second fluid cavity 152 of the cylindrical protrusion 122.

[0043] Similarly, the second thrust plate 144 can have a fluid passage 158 aligned with the first fluid cavity 146 of the cylindrical protrusion 120 and the first fluid cavity 150 of the cylindrical protrusion 122. The second thrust plate 144 also can have a fluid passage 160 aligned with the second fluid cavity 148 of the cylindrical protrusion 120 and the second fluid cavity 152 of the cylindrical protrusion 122.

[0044] The fluid passages 154-160 of the thrust plates 142, 144 can be also kidney-shaped to match shapes of the fluid cavities 146-152. In examples, the thrust plates 142, 144 can have grooves around the fluid passages 154-160 in which kidney-shapes seals may be disposed to seal the respective passages and prevent cross flow therebetween.

[0045] The first fluid cavity 1 0 is in fluid communication or is fluidly coupled to the first port 114, and the second fluid cavity 152 is in fluid communication or is fluidly coupled to the second port 116. With this configuration, the first fluid cavity 146, the fluid passage 154, the fluid passage 158, the first fluid cavity 150 are aligned and in fluid communication with the first port 114. Similarly, the second fluid cavity 148, the fluid passage 156, the fluid passage 160, the second fluid cavity 152 are aligned and in fluid communication with the second port 116.

[0046] The gear pump 100 is configured to operate as a bi-directional pump. Particularly, the first port 114 can operate as an inlet port configured to receive fluid from a fluid reservoir or a hydraulic actuator fluidly coupled to the gear pump 100 (e.g., via a hose or any hydraulic line), and the second port 116 can operate as an outlet or discharge port for providing pressurized fluid being discharged from the gear pump 100 to a hydraulic actuator fluidly coupled to the gear pump 100. The hydraulic actuator can, for example, be a hydraulic cylinder having a piston linearly moving therein or can be a hydraulic motor. In this mode of operation, the pump pinion 134 and the ring gear 130 rotate in a first rotational direction and the hydraulic actuator can move in a first direction.

[0047] In another mode of operation, the first port 114 can operate as a discharge port for providing pressurized fluid being discharged from the gear pump 100 to the hydraulic actuator, and the second port 116 can operate as an inlet port configured to receive fluid from the fluid reservoir. In this mode of operation, the pump pinion 134 and the ring gear 130 rotate in a second rotational direction opposite the first rotational direction, and the hydraulic actuator can move in a second direction opposite the first direction. [0048] Further, the gear pump 100 can operate in a pumping mode or a motoring mode. In the pumping mode, the gear pump 100 provides pressurized fluid to the hydraulic actuator to drive a working member (e.g., a piston) of the hydraulic actuator against a resistive load. In the motoring mode, the fluid returning from the hydraulic actuator is high pressure fluid that can drive a prime move (e.g., an electric motor) driving the gear pump 100 in a regenerative mode.

[0049] Operation of the gear pump 100 is described next assuming it rotates in a given direction. However, it should be understood that the gear pump 100 can operate in the other direction as well where the operation of the ports and fluid volumes is reversed.

[0050] During operation, a prime move (e.g., an engine or electric motor) drives either the pump shaft 132 or the ring gear 130. As such, either the pump pinion 134 rotates within the ring gear 130 and cause the ring gear 130 to rotate, or the ring gear 130 rotates and causes the pump pinion 134 to rotate therewith. As mentioned above, the pump pinion 134 rotates off center relative to the ring gear 130. In other words, a longitudinal axis around which the pump pinion 134 rotates is offset from a respective longitudinal axis around which the ring gear 130 rotates.

[0051] As the external teeth 135 of the pump pinion 134 and the internal teeth 131 of the ring gear 130 separate or disengage, they create an expanding volume (i.e., expanding chamber). The expanding volume collectively represents multiple pockets formed between the separating teeth. The expanding volume operates as a suction void forming between the separating teeth on the intake side of the gear pump 100 that is fluidly coupled to the inlet port (e.g., the first port 114). Fluid from the inlet port thus fills the expanding volume between the teeth.

[0052] Fluid is then carried by the external teeth 135 of the pump pinion 134 and the internal teeth 131 of the ring gear 130 to another chamber or volume on a discharge side of the gear pump 100, which is fluidly coupled to the outlet port (e.g., the second port 116). The meshing of the gear teeth of the pump pinion 134 and the ring gear 130 displaces the fluid, and the fluid is then provided to the outlet port. As such, as the teeth of the pump pinion 134 and the ring gear 130 become interlocked on the discharge side of the gear pump 100, the volume is reduced and the fluid is forced out under pressure.

[0053] As the external teeth 135 of the pump pinion 134 and the internal teeth 131 of the ring gear 130 mesh, they form a seal between the expanding volume having low pressure fluid received from the inlet port and the volume between teeth that are meshing or are about to mesh at the outlet port. The seal created by the meshed teeth forces the fluid out of the discharge port and prevents fluid from flowing back toward the inlet port.

[0054] Further, as shown in Figures 2-3, the gear pump iOO includes a crescent seal assembly comprising an inner crescent 162 and an upper or outer crescent 164. The terms “inner” and “outer” indicate radial positioning of the crescents, where the inner crescent 162 is disposed radially inward relative to the outer crescent 164.

[0055] The inner crescent 162 and the outer crescent 164 are axially supported within the internal space between the ring gear 130 and the pump pinion 134 by a pivot or locating pin 166. Referring to Figure 2, the locating pin 166 is disposed partially in blind holes formed in the cylindrical protrusions 120, 122, and extends through locating pin through-holes in the thrust plates 142, 144 and through the crescents 162, 164.

[0056] With this configuration, the inner crescent 162 and the outer crescent 164 are held axially in position by the locating pin 166. and the locating pin 166 also maintains the orientation of the crescents 162, 164. As such, the locating pin 166 supports the crescent seal assembly (the inner crescent 162 and the outer crescent 164) axially.

[0057] As the pump pinion 134 and the ring gear 130 rotate during operation of the gear pump 100, the crescents 162, 164 divide the fluid as it is being carried from the low pressure suction expanding volume to the volume coupled to the discharge port. Thus, the crescents 162, 164 can form a seal between the low pressure volume and the high pressure volume.

[0058] Particularly, the outer surface (i.e., radially outward surface) of the outer crescent 164 interfaces with the internal teeth 131 of the ring gear 130 to create a seal therebetween. An effective seal between the outer surface of the outer crescent 164 and the internal teeth 131 of the ring gear 130 may preclude leakage from the high pressure volume to the low pressure volume. The terms ‘'preclude” or “block” fluid flow is used herein to indicate substantially preventing fluid flow except for minimal flow of drops per minute, for example.

[0059] In a similar manner, the inner surface (i.e., radially inward surface) of the inner crescent 162 interfaces with the external teeth 135 of the pump pinion 134 to create a seal therebetween. An effective seal between the inner surface of the inner crescent 162 and the external teeth 135 of the pump pinion 134 may preclude leakage from the high pressure volume to the low pressure volume.

[0060] The configuration of a crescent seal assembly of the crescents 162, 164 provides for an effective seal and compensates for radial clearances between the crescents 162, 164 and the gear teeth to create an effective seal. Particularly, fluid from either the expanding volume or the high pressure volume seeping through the interface between the outer crescent 164 and the inner crescent 162 can push the crescents 162, 164 radially apart. Fluid between the crescents 162, 164 can thus push the outer crescent 164 radially outward toward the internal teeth 131 of the ring gear 130, thereby eliminating any radial space or clearance therebetween and forming an effective seal. Similarly, fluid between the crescents 162. 164 can push the inner crescent 162 radially inward toward the external teeth 135 of the pump pinion 134, thereby eliminating any radial space or clearance therebetween and forming an effective seal. [0061] Further, in an example, the crescents 162, 164 can be configured such that at least one spring cavity is formed therebetween. The spring cavities can be formed as recesses in the inner surface of the outer crescent 164. In other example implementations, the spring cavities can be formed as recesses in the outer surface of the inner crescent 162. In another example, both the inner crescent 162 and the outer crescent 164 can have mating or facing recesses that form the spring cavities therebetween.

[0062] The spring cavities can receive springs (e.g., leaf springs, wave springs, or coil springs) therein. In addition to fluid pushing the crescents 162, 164 radially apart, the springs disposed in the spring cavities can also push the crescents 162, 164 radially apart. With this configuration, the springs can push the outer crescent 164 radially outward toward the internal teeth 131 of the ring gear 130, thereby enhancing effectiveness of the seal therebetween. Similarly, the springs can push the inner crescent 162 radially inward toward the external teeth 135 of the pump pinion 134. thereby enhancing effectiveness of the seal therebetween.

[0063] Further, the crescent seal assembly can include check valves between the crescents 162, 164 to preclude fluid flow from the high pressure volume to the low pressure volume regardless of the direction of rotation of the pump shaft 132. In particular, the outer crescent 164 and the inner crescent 162 can have recesses or grooves that form check valve cavities or recesses therebetween. Check pins can be positioned in such check valve cavities.

[0064] Pressurized fluid seeping between the crescents 162, 164 from a high pressure volume to a low pressure volume pushes the check pins against the internal surfaces of the crescents 162, 164, which form a seat for the check pin. The check pins thus create a seal with the surfaces of crescents and precludes leakage thereacross. Another oppositely disposed check pin and check valve cavity can preclude or block leakage in the other direction when the pump shaft 132 rotates in the other rotational direction. [0065] This configuration of the crescent seal assembly thus enables the gear pump 100 to be bi-directional. Whether fluid is drawn through the first port 114 then displaced to the second port 116, or vice versa, the check pins operate as opposite check valves that block leakage fluid flow in either direction. Additional check pins can be added to further enhance the seal between the intake side and the discharge side of the gear pump 100.

[0066] As shown in Figure 4 and as described above, the fluid passages 154-160 of the thrust plates 142, 144 and the fluid cavities 146-152 facilitate communication of fluid from expanding volume and the high pressure volume formed between the pump pinion 134 and the ring gear 130 axially in both directions to reach the interfaces between the thrust plates 142, 144 and the cylindrical protrusions 120, 122. Fluid trapped at the interface between the thrust plate 142 and the cylindrical protrusion 120 applies an axial fluid force on the thrust plate 142 toward end faces of the pump pinion 134 and the ring gear 130. This way. a metal-to-metal seal is created between the thrust plate 142 and the end faces of the pump pinion 134 and the ring gear 130.

[0067] Similarly, fluid trapped at the interface between the thrust plate 144 and the cylindrical protrusion 122 applies an axial fluid force on the thrust plate 144 toward the other end faces of the pump pinion 134 and the ring gear 130. This way, a metal-to-metal seal is created between the thrust plate 144 and the end faces of the pump pinion 134 and the ring gear 130.

[0068] The fluid forces acting on the thrust plates 142. 144 toward the pump pinion 134 and the ring gear 130 pushes or squeezes the thrust plates 142. 144 axially against the pump pinion 134 and the ring gear 130, thereby creating an effective seal and eliminating any axial gaps therebetween. As such, the thrust plates 142, 144 can be referred to as axial compensators as they can compensate for any axial gaps between the thrust plates 142, 144 and the pump pinion 134 and the ring gear 130 disposed therebetween, thereby reducing leakage and improving efficiency of the gear pump 100. [0069] As mentioned above, as the external teeth 135 of the pump pinion 134 separate from the internal teeth 131 of the ring gear 130 on the intake side of the gear pump 100, an expanding volume is created with low pressure. On the discharge side of the gear pump 100, as the external teeth 135 of the pump pinion 134 mesh with the internal teeth 131 of the ring gear 130, a decreasing volume causes fluid to be forced out under pressure. Such pressurized fluid between the pump pinion 134 and the ring gear 130 on the discharge side can apply a radially - outward force on the ring gear 130 and the drive flange 128 toward the cylindrical protrusions 120, 122. As a result, friction and wear may occur at the interface between the drive flange 128 and the cylindrical protrusions 120, 122 at a region where the radially-outward force pushes the drive flange 128 radially toward the cylindrical protrusions 120, 122.

[0070] Such interface region may be different based on the direction of rotation of the pump pinion 134 and the ring gear 130. Particularly, the region that tends to wear or is subjected to friction when the pump pinion 134 and the ring gear 130 are rotating in a first direction (e.g., when the first port 114 is the inlet port and the second port 116 is the outlet port) may be different from a respective region that tends to wear or is subjected to friction when the pump pinion 134 and the ring gear 130 are rotating in a second direction (e.g., when the second port 116 is the inlet port and the first port 114 is the outlet port).

[0071] As show n in Figure 4, the cylindrical protrusion 120 has cross-holes such as cross-hole 168 and cross-hole 170. The term “cross-hole” indicates a hole that crosses a path of another hole, cavity, or channel. The cross-holes 168, 170 are configured to communicate fluid from the first fluid cavity 146 and the second fluid cavity 148, respectively, to the interface betw een the first outer bushing 124 and the cylindrical protrusion 120. As such, the cross-holes 168, 170 can communicate high pressure fluid in the first fluid cavity’ 146 or the second fluid cavity 148 (depending on the direction of rotation of the ring gear 130 and the pump pinion 134) to the interface between the first outer bushing 124 and the cylindrical protrusion 120 to support the first outer bushing 124 during rotation of the drive flange 128.

[0072] Similarly, the cylindrical protrusion 122 has cross-holes such as cross-hole 172 and cross-hole 174. The cross-holes 172, 174 are configured to communicate fluid from the first fluid cavity 150 and the second fluid cavity 152, respectively, to the interface between the second outer bushing 126 and the cylindrical protrusion 122. As such, the cross-holes 172, 174 can communicate high pressure fluid in the first fluid cavity 150 or the second fluid cavity 152 (depending on the direction of rotation of the ring gear 130 and the pump pinion 134) to the interface between the second outer bushing 126 and the cylindrical protrusion 122 to support the second outer bushing 126 during rotation of the drive flange 128.

[0073] The cross-holes 168-174 can also be referred to as feeding ports as they feed fluid to hydrostatic features as described below.

[0074] Figure 5 illustrates a perspective view of the first end cover 104, in accordance with an example implementation. Figure 5 shows the cylindrical protrusion 120 without the first outer bushing 124.

[0075] As depicted in Figure 5, the cylindrical protrusion 120 has a first hydrostatic groove 176 and a second hydrostatic groove 178. The first hydrostatic groove 176 is a circumferential groove that spans a particular angular range about an exterior surface of the cylindrical protrusion 120. Similarly, the second hydrostatic groove 178 is a circumferential groove that spans a respective angular range about the exterior surface of the cylindrical protrusion 120. The first hydrostatic groove 176 overlaps with the second hydrostatic groove 178 for a portion of the respective angular ranges of the hydrostatic grooves 176, 178. However, the first hydrostatic groove 176 is not fluidly coupled to the second hydrostatic groove 178, and no cross flow occurs therebetween as they receive fluid of differing pressure levels. [0076] Referring to Figures 4-5 together, the cross-holes 168-170 communicate fluid to the interface between the first outer bushing 124 and the cylindrical protrusion 120, and thus such fluid fills the hydrostatic grooves 176, 178, thereby supporting the first outer bushing 124 during rotation of the drive flange 128. Particularly, the cross-hole 170 communicates fluid from the second fluid cavity 148 to the first hydrostatic groove 176, whereas the cross-hole 168 communicates fluid from the first fluid cavity 146 to the second hydrostatic groove 178.

[0077] Figure 6 illustrates a perspective view of the first end cover 104 with the first outer bushing 124 mounted to the cylindrical protrusion 120, in accordance with an example implementation. As depicted, the first outer bushing 124 has a first hydrostatic slit 180 (e.g.. opening or window) and a second hydrostatic slit 182.

[0078] The first hydrostatic slit 180 is angularly spaced from the second hydrostatic slit 182 about a surface of the first outer bushing 124. Further, the first hydrostatic slit 180 is fluidly coupled to the first hydrostatic groove 176 of the cylindrical protrusion 120, and the second hydrostatic slit 182 is fluidly coupled to the second hydrostatic groove 178 of the cylindrical protrusion 120.

[0079] Figure 7 illustrates a perspective partial cross-sectional view of the first end cover 104, in accordance with an example implementation. In Figure 7, it is assumed that the gear pump 100 operates in a mode where high pressure fluid is provided to the second fluid cavity 148, while low pressure fluid is provided to the first fluid cavity 146.

[0080] As depicted in Figure 7, high pressure (output) fluid is communicated from the second fluid cavity 148 through the cross-hole 170 to the first hydrostatic groove 176, then through the first hydrostatic slit 180 to the interface between the drive flange 128 and the first outer bushing 124. As such, pressurized fluid is provided to a region of the first outer bushing 124 at which a minimum gap between the first outer bushing 124 and the drive flange 128 may occur. Such use of high pressure fluid in such minimal gap region may reduce friction/wear, enhance capability of the first outer bushing 124 in bearing loads, and enhance lubrication and performance of the first outer bushing 124 in supporting rotation of the drive flange 128 relative to the cylindrical protrusion 120, particularly at low rotational speeds.

[0081] Similarly, referring to Figures 4-7 together, low pressure (inlet) fluid is communicated from the first fluid cavity 146 through the cross-hole 168 to the second hydrostatic groove 178, then through the second hydrostatic slit 182 to the interface between the drive flange 128 and the first outer bushing 124. Such low pressure fluid can further support lubrication at the interface of the first outer bushing 124 and the drive flange 128. and may also providing a cooling effect (e.g., at the lubricated interface).

[0082] Notably, as mentioned above, the gear pump 100 is configured to be bi-directional. Thus, in another mode of operation where the ring gear 130 and the pump pinion 134 rotate in the opposite direction, the first fluid cavity 146 may receive high pressure fluid, and thus the second hydrostatic slit 182 communicates such high pressure fluid at the region with the minimal gap. In this mode, the second fluid cavity 148 receives the low pressure fluid and communicates it to the first hydrostatic slit 180. In other words, the high pressure fluid and low pressure fluid in Figure 7 would be switched.

[0083] The cylindrical protrusion 122 and the second outer bushing 126 are configured in a similar manner to support lubrication and reduce friction/wear between the drive flange 128 and the cylindrical protrusion 122, and enhance capability of the second outer bushing 126 in bearing loads.

[0084] Figure 8 illustrates a perspective view of the cylindrical protrusion 122 and the second outer bushing 126 during a first mode of operation, in accordance with an example implementation. Similar to the first outer bushing 124, the second outer bushing 126 has a hydrostatic slit 184 and a hydrostatic slit 186, that are respectively in fluid communication with hydrostatic grooves (not shown) formed in the cylindrical protrusion 122.

[0085] In one mode of operation, where the pump shaft 132, the pump pinion 134, and the ring gear 130 rotate in one direction, the first fluid cavity 150 receives the high pressure fluid of the gear pump 100, and fluid is communicated from the first fluid cavity 150 through the hydrostatic slit 186 to region 188 (shaded region), which represents the minimal gap region (e.g., minimal gap between the second outer bushing 126 and the drive flange 128) in this mode of operation. The region 188 overlaps with or encompasses the hydrostatic slit 186 as shown in Figure 8.

[0086] In another mode of operation, where the pump shaft 132, the pump pinion 134, and the ring gear 130 rotate in an opposite direction, the second fluid cavity 152 receives the high pressure fluid. Such high pressure fluid is then communication through the hydrostatic slit 184 to a respective minimal gap region.

[0087] Figure 9 illustrates a perspective view of the cylindrical protrusion 122 and the second outer bushing 126 during a second mode of operation, in accordance with an example implementation. As depicted in Figure 9, in this mode of operation, the second fluid cavity 152 receives the high pressure fluid of the gear pump 100, and fluid is communicated from the second fluid cavity 152 through the hydrostatic slit 184 to region 190 (shaded region), which represents the minimal gap region (e.g., minimal gap between the second outer bushing 126 and the drive flange 128) in this mode of operation. The region 190 overlaps with or encompasses the hydrostatic slit 184 as depicted in Figure 9.

[0088] At the same time that fluid is communicated to the interface betw een the outer bushings 124, 126 with the cylindrical protrusions 120, 122 and the drive flange 128, fluid is also communicated to the interface between the inner bushings 136, 138 and the interior peripheral surfaces of the cylindrical protrusions 120, 122. Particularly, the internal cavities or through- holes of the cylindrical protrusions 120, 122 that accommodate the pump shaft 132 and the inner bushings 136, 138 are bounded by surfaces having hydrostatic grooves similar to the hydrostatic grooves 176, 178.

[0089] The inner bushings 136, 138 can also have hydrostatic slits similar to the hydrostatic slits 180-186 configured to diffuse fluid at the interface between the inner bushings 136, 138 and the cylindrical protrusions 120, 122 to facilitate and support rotation of the pump shaft 132. This way, rotation of the pump shaft 132 is supported and lubricated to enhance performance and reduce friction/wear, enhance capability of the inner bushings 136, 138 in bearing loads particularly at low rotational speeds.

[0090] Figure 10 illustrates a perspective view of the second end cover 106, in accordance with an example implementation. As shown in Figure 10, the second inner bushing 138 can have a hydrostatic slit 192 and hydrostatic slit 194. In Figure 10, the second fluid cavity 152 receives the high pressure (output) fluid, which is communicated to the hydrostatic slit 184 of the outer bushing 126 as described above.

[0091] At the same time, pressurized fluid from the second fluid cavity 152 is communicated to the hydrostatic slit 192 on the opposite side, and then fluid is diffused through the hydrostatic slit 192 to the interface between the second inner bushing 138 and the interior surface of the cylindrical protrusion. Also, low pressure fluid in the first fluid cavity 150 is communicated through cross-hole 196 and hydrostatic groove 198 formed in the interior surface of the cylindrical protrusion 122 to the hydrostatic slit 194.

[0092] The first inner bushing 136 and the cylindrical protrusion 120 may have a similar configuration. This way, rotation of the pump shaft 132 is supported and lubricated during operation of the gear pump 100. [0093] In one example, the gear pump 100 can be driven via a prime mover external to the gear pump 100. For instance, referring to Figures 2-4, an engine or electric motor can be coupled to the pump shaft 132, e.g., via splines 199 formed at an end of the pump shaft 132. In another example, however, an electric motor can be integrated within the internal chamber 103 of the assembly housing 102 to drive the gear pump 100. With this configuration, a compact assembly including the prime mover (the electric motor) and the gear pump 100 is formed.

[0094] Figure 11 illustrates a cross-sectional side view of an assembly 200 including the gear pump 100 and an electric motor 202 integrated therewith, and Figure 12 illustrates a perspective exploded view of the assembly 200. in accordance with an example implementation. Figures 11-12 are described together. As depicted, the electric motor 202 is disposed within the internal chamber 103 of the assembly housing 102.

[0095] The electric motor 202 includes a stator 204 fixedly-positioned within the internal chamber 103 of the assembly housing 102. The stator 204 can have wire windings 206 that are wrapped about a body (e.g., a lamination stack) of the stator 204, and when electric current is provided through the wire windings, a magnetic field is generated.

[0096] The electric motor 202 further includes a rotor 208 positioned within the stator 204. The electric motor 202 can further include magnets 210 mounted to the rotor 208 in an annular space between the stator 204 and the rotor 208. The magnets 210 are configured to interact with the magnetic field generated by the wire windings 206 of the stator 204 to rotate the rotor 208 and produce torque. In other example implementation, a different type of electric motor might be used that does not include permanent magnets.

[0097] The gear pump 100 is mounted within the assembly housing 102, and, at least partially, within the rotor 208 and the stator 204 of the electric motor 202. Further, the rotor 208 is coupled to the drive flange 128 such that as the rotor 208 rotates, the drive flange 128 and the 1 ring gear 130 rotate therewith. For example, the drive flange 128 can be press fitted inside the rotor 208 such that the drive flange 128 is coupled to the rotor 208. Other arrangements, such as key-keyway arrangement, spline arrangement, self-holding taper arrangement, etc. could alternatively be used to couple the rotor 208 to the drive flange 128.

[0098] Thus, as the rotor 208 rotates, the drive flange 128 and the ring gear 130 rotate, thereby driving the pump pinion 134 mounted to or integrated with a pump shaft 212. The pump shaft 212 differs from the pump shaft 132 in that the pump shaft 212 is shorter and does not extend outside the first end cover 104. The pump shaft 212 is not driven by an external prime mover, but is rather driven by the electric motor 202 integrated with the gear pump 100 in the assembly 200. A plug 214 can be used to cap the hole in the first end cover 104 through which the pump shaft 212 can be inserted.

[0099] As the rotor 208 drives the ring gear 130, the ring gear 130 drives the pump pinion 134, which is offset from the ring gear 130 (i.e., the pump pinion 134 is disposed off-center relative to the ring gear 130), as described above. No separate bearings might be need to support rotation of the rotor 208. Rather, the outer bushings 124, 126 and the inner bushings 136, 138 support rotation of the rotating components of the assembly 200. This way, the gear pump 100 and the electric motor 202 share components to reduce cost and have a compact assembly.

[00100] The detailed description above describes various features and operations of the disclosed systems with reference to the accompanying figures. The illustrative implementations described herein are not meant to be limiting. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[00101] Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

[00102] Additionally, any enumeration of elements, blocks, or steps in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried out in a particular order.

[00103] Further, devices or systems may be used or configured to perform functions presented in the figures. In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and/or software) to enable such performance. In other examples, components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner.

[00104] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide

[00105] The arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location. [00106] While various aspects and implementations have been disclosed herein, other aspects and implementations will be apparent to those skilled in the art. The various aspects and implementations disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. Also, the terminology⁷ used herein is for the purpose of describing particular implementations only, and is not intended to be limiting.

[00107] Embodiments of the present disclosure can thus relate to one of the enumerated example embodiments (EEEs) listed below.

[00108] EEE 1 is a gear pump comprising: a pump housing comprising a hydrostatic groove; an outer bushing mounted to the pump housing and comprising a hydrostatic slit that is fluidly coupled to the hydrostatic groove of the pump housing; a drive flange mounted to the outer bushing such that outer bushing is interposed radially between the pump housing and the drive flange; a ring gear coupled to the drive flange and configured to rotate therewith; a pump pinion disposed within the ring gear, such that external teeth of the pump pinion engage with internal teeth of the ring gear; and a plurality of ports comprising: a first port and a second port, wherein as the pump pinion and the ring gear rotate, fluid is draw n from the first port and displaced to the second port for discharge, wherein fluid from the second port is provided to the hydrostatic groove of the pump housing and communicated through the hydrostatic slit to an interface between the drive flange and the outer bushing to facilitate rotation of the drive flange relative to the pump housing.

[00109] EEE 2 is the gear pump of EEE 1, wherein the hydrostatic groove is a first hydrostatic groove, wherein the hydrostatic slit is a first hydrostatic slit, wherein the pump housing comprises a second hydrostatic groove, wherein the outer bushing comprises a second hydrostatic slit, and wherein fluid from the first port is provided to the second hydrostatic groove and communicated through the second hydrostatic slit to the interface between the drive flange and the outer bushing.

[00110] EEE 3 is the gear pump of EEE 2, wherein the first hydrostatic slit is angularly spaced from the second hydrostatic slit about a surface of the outer bushing.

[00111] EEE 4 is the gear pump of any of EEEs 2-3, wherein the first hydrostatic groove is a circumferential groove that spans a particular angular range about an exterior surface of the pump housing, wherein the second hydrostatic groove is a respective circumferential groove that spans a respective angular range about the exterior surface of the pump housing, and wherein the first hydrostatic groove overlaps with the second hydrostatic groove for a portion of the respective angular range.

[00112] EEE 5 is the gear pump of any of EEEs 1-4, wherein the pump housing comprises a cylindrical protrusion comprising the hydrostatic groove, and wherein the outer bushing is mounted to the cylindrical protrusion.

[00113] EEE 6 is the gear pump of EEE 5, wherein the cylindrical protrusion is a first cylindrical protrusion, wherein the pump housing comprises a second cylindrical protrusion facing the first cylindrical protrusion such that the ring gear and the pump pinion are interposed between the first cylindrical protrusion and the second cylindrical protrusion.

[00114] EEE 7 is the gear pump of EEE 6, wherein the outer bushing is a first outer bushing mounted to the first cylindrical protrusion, wherein the second cylindrical protrusion comprises a respective hydrostatic groove, and wherein the gear pump further comprises: a second outer bushing mounted to the second cylindrical protrusion and interposed radially between the second cylindrical protrusion and the drive flange, wherein the second outer bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove of the second cylindrical protrusion, such that fluid from the second port is provided to the respective hydrostatic groove of the second cylindrical protrusion and communicated through the respective hydrostatic slit to a respective interface between the drive flange and the second outer bushing to facilitate rotation of the drive flange relative to the pump housing.

[00115] EEE 8 is the gear pump of any of EEEs 6-7, further comprising: a first end cover comprising the first cylindrical protrusion; and a second end cover comprising the second cylindrical protrusion, wherein the second end cover comprises the first port and the second port.

[00116] EEE 9 is the gear pump of any of EEEs 5-8, wherein the cylindrical protrusion comprises (i) a fluid cavity that is fluidly coupled to the second port, and (ii) a cross-hole configured to communicate fluid from the fluid cavity to the hydrostatic groove.

[00117] EEE 10 is the gear pump of any of EEEs 1-9, wherein the pump pinion is mounted to a pump shaft, wherein the pump shaft is supported within the pump housing, and wherein the gear pump further comprises: an inner bushing mounted within the pump housing and interposed radially between the pump shaft and an interior peripheral surface of the pump housing, wherein the interior peripheral surface of the pump housing comprises a respective hydrostatic groove, wherein the inner bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove, wherein fluid from the second port is provided to the respective hydrostatic groove and communicated through the respective hydrostatic slit to a respective interface between the inner bushing and the interior peripheral surface of the pump housing to facilitate rotation of the pump shaft relative to the pump housing.

[00118] EEE 11 is the gear pump of EEE 10, wherein the respective hy drostatic groove is a first respective hydrostatic groove, wherein the respective hydrostatic slit is a first respective hydrostatic slit, wherein the pump housing comprises a second respective hydrostatic groove formed in the interior peripheral surface of the pump housing, wherein the inner bushing comprises a second respective hydrostatic slit, and wherein fluid from the first port is provided to the second respective hydrostatic groove and communicated through the second respective hydrostatic slit to the respective interface between the inner bushing and the interior peripheral surface of the pump housing.

[00119] EEE 12 is the gear pump of EEE 11, wherein a center of rotation of the pump shaft and the pump pinion is offset from a respective center of rotation of the ring gear such that the inner bushing is eccentric relative to the outer bushing.

[00120] EEE 13 is an assembly comprising: an assembly housing having an internal chamber therein; an electric motor disposed in the internal chamber of the assembly housing and comprising (i) a stator that is fixedly positioned in the internal chamber of the assembly housing, and (ii) a rotor positioned within the stator and rotatable relative to the stator; and the gear pump of any of EEEs 1-12 positioned in the assembly housing, at least partially within the rotor of the electric motor. For example, the gear pump comprises: a drive flange coupled to the rotor of the electric motor such that the rotor is configured to rotate the drive flange, a ring gear coupled to the drive flange and configured to rotate therewith, a pump pinion disposed within the ring gear, such that external teeth of the pump pinion engage with internal teeth of the ring gear, and a plurality of ports comprising: a first port and a second port, wherein as the rotor rotates, the drive flange and the ring gear rotate therewith, causing the pump pinion to rotate within the ring gear, such that fluid is drawn from the first port and displaced to the second port for discharge.

[00121] EEE 14 is the assembly of EEE 13, further comprising: an end cover coupled to the assembly housing and comprising a cylindrical protrusion, wherein the cylindrical protrusion comprises a hydrostatic groove; and an outer bushing mounted to the cylindrical protrusion such that outer bushing is interposed radially between the cylindrical protrusion and the drive flange, wherein the outer bushing comprises a hydrostatic slit that is fluidly coupled to the hydrostatic groove of the cylindrical protrusion, and wherein fluid from the second port is provided to the hydrostatic groove of the cylindrical protrusion and communicated through the hydrostatic slit to an interface between the drive flange and the outer bushing to facilitate rotation of the drive flange relative to the cylindrical protrusion.

[00122] EEE 15 is the assembly of EEE 14, wherein the hydrostatic groove is a first hydrostatic groove, wherein the hydrostatic slit is a first hydrostatic slit, wherein the cylindrical protrusion comprises a second hydrostatic groove, wherein the outer bushing comprises a second hydrostatic slit, and wherein fluid from the first port is provided to the second hydrostatic groove and communicated through the second hydrostatic slit to the interface between the drive flange and the outer bushing.

[00123] EEE 16 is the assembly of any of EEEs 14-15, wherein the end cover is a first end cover, wherein the cylindrical protrusion is a first cylindrical protrusion, and wherein the assembly further comprises: a second end cover coupled to the assembly housing and comprising a second cylindrical protrusion facing the first cylindrical protrusion, wherein the ring gear and the pump pinion are interposed between the first cylindrical protrusion and the second cylindrical protrusion.

[00124] EEE 17 is the assembly of EEE 16, wherein the outer bushing is a first outer bushing mounted to the first cylindrical protrusion, wherein the second cylindrical protrusion comprises a respective hydrostatic groove, and wherein the gear pump further comprises: a second outer bushing mounted to the second cylindrical protrusion and interposed radially between the second cylindrical protrusion and the drive flange, wherein the second outer bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove of the second cylindrical protrusion, such that fluid from the second port is provided to the respective hydrostatic groove of the second cylindrical protrusion and communicated through the respective hydrostatic slit to a respective interface between the drive flange and the second outer bushing to facilitate rotation of the drive flange relative to the second cylindrical protrusion.

[00125] EEE 18 is the assembly of any of EEEs 14-17, wherein the cylindrical protrusion comprises (i) a fluid cavity that is fluidly coupled to the second port, and (ii) a cross-hole configured to communicate fluid from the fluid cavity to the hydrostatic groove.

[00126] EEE 19 is the assembly of any of EEEs 14-18, wherein the pump pinion is mounted to a pump shaft, wherein the pump shaft is supported within the cylindrical protrusion, and wherein the gear pump further comprises: an inner bushing mounted within the cylindrical protrusion and interposed radially between the pump shaft and an interior peripheral surface of the cylindrical protrusion, wherein the interior peripheral surface of the cylindrical protrusion comprises a respective hydrostatic groove, wherein the inner bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove, wherein fluid from the second port is provided to the respective hydrostatic groove and communicated through the respective hydrostatic slit to a respective interface between the inner bushing and the interior peripheral surface of the cylindrical protrusion to facilitate rotation of the pump shaft relative to the cylindrical protrusion.

[00127] EEE 20 is the assembly of EEE 19, wherein the respective hydrostatic groove is a first respective hydrostatic groove, wherein the respective hydrostatic slit is a first respective hydrostatic slit, wherein the cylindrical protrusion comprises a second respective hydrostatic groove formed in the interior peripheral surface of the cylindrical protrusion, wherein the inner bushing comprises a second respective hydrostatic slit, and wherein fluid from the first port is provided to the second respective hydrostatic groove and communicated through the second respective hydrostatic slit to the respective interface between the inner bushing and the interior peripheral surface of the cylindrical protrusion.

Claims

CLAIMS What is claimed is:

1. A gear pump comprising: a pump housing comprising a hydrostatic groove; an outer bushing mounted to the pump housing and comprising a hydrostatic slit that is fluidly coupled to the hydrostatic groove of the pump housing; a drive flange mounted to the outer bushing such that outer bushing is interposed radially between the pump housing and the drive flange; a ring gear coupled to the drive flange and configured to rotate therewith; a pump pinion disposed within the nng gear, such that external teeth of the pump pinion engage with internal teeth of the ring gear; and a plurality of ports comprising: a first port and a second port, wherein as the pump pinion and the ring gear rotate, fluid is drawn from the first port and displaced to the second port for discharge, wherein fluid from the second port is provided to the hydrostatic groove of the pump housing and communicated through the hydrostatic slit to an interface between the drive flange and the outer bushing to facilitate rotation of the drive flange relative to the pump housing.

2. The gear pump of claim 1, wherein the hydrostatic groove is a first hydrostatic groove, wherein the hydrostatic slit is a first hydrostatic slit, wherein the pump housing comprises a second hydrostatic groove, wherein the outer bushing comprises a second hydrostatic slit, and wherein fluid from the first port is provided to the second hydrostatic groove and communicated through the second hydrostatic slit to the interface between the drive flange and the outer bushing.

3. The gear pump of claim 2, wherein the first hydrostatic slit is angularly spaced from the second hydrostatic slit about a surface of the outer bushing.

4. The gear pump of claim 2, wherein the first hydrostatic groove is a circumferential groove that spans a particular angular range about an exterior surface of the pump housing, wherein the second hydrostatic groove is a respective circumferential groove that spans a respective angular range about the exterior surface of the pump housing, and wherein the first hydrostatic groove overlaps with the second hydrostatic groove for a portion of the respective angular range.

5. The gear pump of claim 1, wherein the pump housing comprises a cylindrical protrusion comprising the hydrostatic groove, and wherein the outer bushing is mounted to the cylindrical protrusion.

6. The gear pump of claim 5, wherein the cylindrical protrusion is a first cylindrical protrusion, wherein the pump housing comprises a second cylindrical protrusion facing the first cylindrical protrusion such that the ring gear and the pump pinion are interposed between the first cylindrical protrusion and the second cylindrical protrusion.

7. The gear pump of claim 6, wherein the outer bushing is a first outer bushing mounted to the first cylindrical protrusion, wherein the second cylindrical protrusion comprises a respective hydrostatic groove, and wherein the gear pump further comprises: a second outer bushing mounted to the second cylindrical protrusion and interposed radially between the second cylindrical protrusion and the drive flange, wherein the second outer bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove of the second cylindrical protrusion, such that fluid from the second port is provided to the respective hydrostatic groove of the second cylindrical protrusion and communicated through the respective hydrostatic slit to a respective interface between the drive flange and the second outer bushing to facilitate rotation of the drive flange relative to the pump housing.

8. The gear pump of claim 6, further comprising: a first end cover comprising the first cylindrical protrusion; and a second end cover comprising the second cylindrical protrusion, wherein the second end cover comprises the first port and the second port.

9. The gear pump of claim 5, wherein the cylindrical protrusion comprises (i) a fluid cavity that is fluidly coupled to the second port, and (ii) a cross-hole configured to communicate fluid from the fluid cavity to the hydrostatic groove.

10. The gear pump of claim 1 , wherein the pump pinion is mounted to a pump shaft, wherein the pump shaft is supported within the pump housing, and wherein the gear pump further comprises: an inner bushing mounted within the pump housing and interposed radially between the pump shaft and an interior peripheral surface of the pump housing, wherein the interior peripheral surface of the pump housing comprises a respective hydrostatic groove, wherein the inner bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove, wherein fluid from the second port is provided to the respective hydrostatic groove and communicated through the respective hydrostatic slit to a respective interface between the inner bushing and the interior peripheral surface of the pump housing to facilitate rotation of the pump shaft relative to the pump housing.

11. The gear pump of claim 10, wherein the respective hydrostatic groove is a first respective hydrostatic groove, wherein the respective hydrostatic slit is a first respective hydrostatic slit, wherein the pump housing comprises a second respective hydrostatic groove formed in the interior peripheral surface of the pump housing, wherein the inner bushing comprises a second respective hydrostatic slit, and wherein fluid from the first port is provided to the second respective hydrostatic groove and communicated through the second respective hydrostatic slit to the respective interface between the inner bushing and the interior peripheral surface of the pump housing.

12. The gear pump of claim 11, wherein a center of rotation of the pump shaft and the pump pinion is offset from a respective center of rotation of the ring gear such that the inner bushing is eccentric relative to the outer bushing.

13. An assembly comprising: an assembly housing having an internal chamber therein; an electric motor disposed in the internal chamber of the assembly housing and comprising (i) a stator that is fixedly positioned in the internal chamber of the assembly housing, and (ii) a rotor positioned within the stator and rotatable relative to the stator; and a gear pump positioned in the assembly housing, at least partially within the rotor of the electric motor, wherein the gear pump comprises: a drive flange coupled to the rotor of the electric motor such that the rotor is configured to rotate the drive flange, a ring gear coupled to the drive flange and configured to rotate therewith, a pump pinion disposed within the ring gear, such that external teeth of the pump pinion engage with internal teeth of the ring gear, and a plurality' of ports comprising: a first port and a second port, wherein as the rotor rotates, the drive flange and the ring gear rotate therewith, causing the pump pinion to rotate within the ring gear, such that fluid is drawn from the first port and displaced to the second port for discharge.

14. The assembly of claim 13, further comprising: an end cover coupled to the assembly housing and comprising a cylindrical protrusion, wherein the cylindrical protrusion comprises a hydrostatic groove; and an outer bushing mounted to the cylindrical protrusion such that outer bushing is interposed radially between the cylindrical protrusion and the drive flange, wherein the outer bushing comprises a hydrostatic slit that is fluidly coupled to the hydrostatic groove of the cylindrical protrusion, and wherein fluid from the second port is provided to the hydrostatic groove of the cylindrical protrusion and communicated through the hydrostatic slit to an interface between the drive flange and the outer bushing to facilitate rotation of the drive flange relative to the cylindrical protrusion.

15. The assembly of claim 14, wherein the hydrostatic groove is a first hydrostatic groove, wherein the hydrostatic slit is a first hydrostatic slit, wherein the cylindrical protrusion comprises a second hydrostatic groove, wherein the outer bushing comprises a second hydrostatic slit, and wherein fluid from the first port is provided to the second hydrostatic groove and communicated through the second hydrostatic slit to the interface between the drive flange and the outer bushing.

16. The assembly of claim 14, wherein the end cover is a first end cover, wherein the cylindrical protrusion is a first cylindrical protrusion, and wherein the assembly further comprises: a second end cover coupled to the assembly housing and comprising a second cylindrical protrusion facing the first cylindrical protrusion, wherein the ring gear and the pump pinion are interposed between the first cylindrical protrusion and the second cylindrical protrusion.

17. The assembly of claim 16, wherein the outer bushing is a first outer bushing mounted to the first cylindrical protrusion, wherein the second cylindrical protrusion comprises a respective hydrostatic groove, and wherein the gear pump further comprises: a second outer bushing mounted to the second cylindrical protrusion and interposed radially between the second cylindrical protrusion and the drive flange, wherein the second outer bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove of the second cylindrical protrusion, such that fluid from the second port is provided to the respective hydrostatic groove of the second cylindrical protrusion and communicated through the respective hydrostatic slit to a respective interface between the drive flange and the second outer bushing to facilitate rotation of the drive flange relative to the second cylindrical protrusion.

18. The assembly of claim 14. wherein the cylindrical protrusion comprises (i) a fluid cavity that is fluidly coupled to the second port, and (ii) a cross-hole configured to communicate fluid from the fluid cavity to the hydrostatic groove.

19. The assembly of claim 14, wherein the pump pinion is mounted to a pump shaft, wherein the pump shaft is supported within the cylindrical protrusion, and wherein the gear pump further comprises: an inner bushing mounted within the cylindrical protrusion and interposed radially between the pump shaft and an interior peripheral surface of the cylindrical protrusion, wherein the interior peripheral surface of the cylindrical protrusion comprises a respective hydrostatic groove, wherein the inner bushing comprises a respective hydrostatic slit that is fluidly coupled to the respective hydrostatic groove, wherein fluid from the second port is provided to the respective hydrostatic groove and communicated through the respective hydrostatic slit to a respective interface between the inner bushing and the interior peripheral surface of the cylindrical protrusion to facilitate rotation of the pump shaft relative to the cylindrical protrusion.

20. The assembly of claim 19. wherein the respective hydrostatic groove is a first respective hydrostatic groove, wherein the respective hydrostatic slit is a first respective hydrostatic slit, wherein the cylindrical protrusion comprises a second respective hydrostatic groove formed in the interior peripheral surface of the cylindrical protrusion, wherein the inner bushing comprises a second respective hydrostatic slit, and wherein fluid from the first port is provided to the second respective hydrostatic groove and communicated through the second respective hydrostatic slit to the respective interface between the inner bushing and the interior peripheral surface of the cylindrical protrusion.