Axially compact oil pump

Abstract

An axially compact gerotor-based electric oil pump for automotive use utilizes an axial flux electric motor. The motor has a drive shaft that is drivingly connected to the gerotor. The gerotor can be mounted for rotation about a tubular journal bearing which also journals the drive shaft, inhibiting axial tilt of the drive shaft due to a transverse force arising from gerotor pressure differential. The axial flux motor can also generate an axially directed continual magnetic force to generate a transverse friction force to counteract the transverse force arising from the gerotor pressure differential.

Description

AXIALLY COMPACT OIL PUMPCross-Reference to Related Applications

[0001] This application claims the benefit of, and priority to US Provisional Application No. 63 / 708,689 filed October 17, 2024 entitled "Shortened Shaft Oil Pump", the contents of which are incorporated by reference herein where permitted.Field of Art

[0002] This disclosure relates generally to the field of electric oil pumps, particularly those configured for automotive applications.Background

[0003] Automotive electric oil pumps are prevalent in many automotive vehicles for circulating lubricating and / or cooling oil. Often, the electric oil pump is integrated into a larger assembly such as an electric motor, a transmission, or a battery pack. The conventional automotive electric oil pump typically features a gerotor set driven by a conventional radial flux electric motor. Such pumps have relatively long axial dimensions in comparison to their widths. It would be beneficial to reduce the overall size of an automotive electric oil pump, particularly in the axial direction, in comparison to the conventional product.Summary

[0004] In a first aspect, an electric oil pump is provided which includes a casing, a tubular journal bearing disposed within the casing, a gerotor mounted about the tubular journal bearing, a drive shaft mounted within the tubular journal bearing, and an electric motor connected to the drive shaft. An internal barrier segregates the pump into a wet pumping chamber and a dry motor compartment. The pumping chamber includes a fluid inlet and a fluid outlet for ingress and egress of oil, respectively. The tubular journal bearing is disposed in the pumping chamber and has an outer wall and an internal bore therein. The tubular journal bearing defines a rotational axis of the pump. A shaft seal can be disposed along the internal barrier. The gerotor, comprising an inner rotor and outer rotor, is disposed in the pumping chamber. The gerotorinner rotor is mounted for rotation about the tubular journal bearing so as to bear against the outer wall thereof. The drive shaft is mounted for rotation within the bore of the tubular journal bearing and extends through the shaft seal into the dry motor compartment. The drive shaft is drivingly connected to the gerotor inner rotor. The electric motor is disposed within the dry motor compartment and drives the drive shaft. As the tubular journal bearing accomplishes the double function of bearing the gerotor inner rotor in addition to the drive shaft, the axial compactness of the pump may be improved and the structure may counteract transverse forces arising from pressure differentials in the pumping chamber which tend to tilt the drive shaft.

[0005] The drive shaft can include a shank and a head that has a larger radial breadth than a radial breadth of the shank; and the head can be drivingly connected to the gerotor inner rotor.

[0006] The electric motor can include a rotor and a stator operable to electromag netica I ly interact with one another via a magnetic air gap. The rotor can include a permanent magnet structure fixed to the drive shaft and rotatable about the rotational axis. The permanent magnet structure and the stator can be configured to generate a continual magnetic attractive force directed along the rotational axis to press the drive shaft or drive shaft head against either a wall of the pumping chamber orientated transverse to the rotational axis or an axially facing face of the tubular journal bearing. The magnitude of the continual magnetic attractive force may be large enough to inhibit tilting of the drive shaft over an operating range of the pump due to the aforesaid pressure differential forces.

[0007] The operating range of the pump can include a maximal operating rotational velocity of the gerotor, and a maximal operating pressure generated by the gerotor.

[0008] The stator can be provisioned by a printed circuit board (PCB) and a magnetically permeable stator core, with the PCB being disposed transverse to the rotational axis and having a first face proximal to the magnetic air gap and a second, opposing, face distal to the magnetic air gap, and the stator core being disposed adjacent to the second face of the PCB.

[0009] The internal barrier can include a dividing wall and the tubular journal bearing can depend from the internal dividing wall.

[0010] In some embodiments, a clearance can be provisioned between the drive shaft head and the inner rotor, and an axial length of the tubular journal bearing within the inner gerotor can be at least 50% of the axial length of the inner gerotor.

[0011] In another aspect an electric oil pump is provided which includes a casing that is segregated into a wet pumping chamber and a dry motor compartment by an internal dividing wall. The pumping chamber includes a fluid inlet and a fluid outlet for ingress and egress of oil, respectively. A journal bearing, which definiens a rotational axis, is disposed in the pumping chamber. A shaft seal is disposed along the internal dividing wall. A drive shaft, including a shank and a head, is mounted for rotation within the journal bearing, with the shank extending through the shaft seal into the dry motor compartment and the head projecting from the journal bearing. A gerotor is mounted for rotation in the pumping chamber. The gerotor includes an inner rotor and an outer rotor and the drive shaft head is drivingly connected to one of the inner and outer rotors. An electric motor is disposed within the dry motor compartment. The electric motor includes a rotor and a stator operable to electromagnetically interact with one another via a magnetic air gap. The rotor includes a permanent magnet structure fixed to the drive shaft and rotatable about the rotational axis. The permanent magnet structure and the stator are configured to generate a continual magnetic attractive force directed along the rotational axis to press the drive shaft head against either a wall of the pumping chamber orientated transverse to the rotational axis or an axially facing face of the journal bearing. The magnitude of the continual magnetic attractive force is large enough to inhibit tilting of the drive shaft over an operating range of the pump due to forces arising from a pressure differential between the fluid inlet and fluid outlet which are applied to the gerotor in a direction transverse to the rotational axis.

[0012] The operating range of the pump can include operation at a maximal rotational velocity of the gerotor and a maximal pressure generated by the gerotor.

[0010] The stator can be provisioned by a printed circuit board (PCB) and a magnetically permeable stator core, the PCB being disposed transverse to the rotational axis and having a first face proximal to the magnetic air gap and a second, opposing, face distal to the magnetic air gap, the stator core being disposed adjacent to the second face of the PCB.

[0013] The journal bearing can be provisioned as a tubular journal bearing having an internal bore and an outer cylindrical wall with the drive shaft shank journalled in the internal bore and the gerotor inner rotor being rotatingly mounted about the tubular journal bearing so as to bear against the outer cylindrical wall thereof.

[0014] The tubular journal bearing can depend from the internal dividing wall.

[0015] The drive shaft head can have a larger radial breadth than a radial breadth of the shank, and the head can be drivingly connected to the gerotor inner rotor.Brief Description of Drawings

[0016] The foregoing and other aspects of this disclosure may be better appreciated having regard to the attached drawings, in which:

[0017] Figure 1 is a perspective view of an electric oil pump according to a first embodiment;

[0018] Figure 2 is a partial cross-sectional, partial isometric view of the pump shown in Figure 1;

[0019] Figure 3A is an exploded view from one viewing angle of the pump shown in Figure 1;

[0020] Figure 3B is an exploded view of the pump shown in Figure 1, taken from a different viewing angle than that of Figure 3A;

[0021] Figure 4 is a cross-sectional view of an electric motor embodied in the pump shown in Figure 1;

[0022] Figure 5 is a cross-sectional view of the pump shown in Figure 1, illustrating various dimensions and applied forces;

[0023] Figure 6 is a perspective view of an electric oil pump according to a second embodiment;

[0024] Figure 7 is a partial cross-sectional, partial isometric view of the pump shown in Figure 6; and

[0025] Figure 8 is a cross-sectional view of the pump shown in Figure 6, illustrating various dimensions and applied forces.Detailed Description of Example Embodiments

[0026] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements.In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiment or embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well- known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below.

[0027] Various terms used throughout the present description may be read and understood as follows, unless the context indicates otherwise: "or" as used throughout is inclusive, as though written "and / or"; singular articles and pronouns as used throughout include their plural forms, and vice versa; similarly, gendered pronouns include their counterpart pronouns so that pronouns should not be understood as limiting anything described herein to use, implementation, performance, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplifying" and not necessarily as "preferred" over other embodiments. Further definitions for terms may be set out herein; these may apply to prior and subsequent instances of those terms, as will be understood from a reading of the present description.

[0028] Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, "each" refers to each member of a set or each member of a subset of a set.

[0029] The indefinite article "a" is not intended to be limited to mean "one" of an element. It is intended to mean "one or more" of an element, where applicable, (i.e. unless in the context it would be obvious that only one of the element would be suitable).

[0030] Terms such as "connected to", "fixed to", "bears against" and "supported by" do not mean that a first part necessarily has to directly touch a second part in order for the first and second parts to be considered connected together, fixed together, bear against one another, orsupported by one or the other, respectively. Unless the context clearly dictates otherwise, two parts may considered connected together, fixed together, bear against one another, or supported by one or the other through one or more intermediate parts which function to bear or transfer loads between the first and second parts.

[0031] Any reference to upper, lower, top, bottom or the like are intended to refer to a relative orientation of a particular element in relation to other elements and not necessarily in absolute terms, or to orientation during manufacture, shipping or use. The upper surface of an element, for example, can still be considered an upper surface in relation to another surface even when the element is lying on its side or upside down.

[0032] "Memory" refers to a non-transitory tangible computer-readable medium for storing information (e.g., data or data structures) in a format readable by a processor, and / or instructions (e.g., computer code or software programs or modules) that are readable and executable by a processor to implement an algorithm. The term "memory" includes a single device or a plurality of physically discrete, operatively connected devices despite use of the term in the singular. Non-limiting types of memory include solid-state semiconductor, optical, magnetic, and magneto-optical computer readable media. Examples of memory technologies include optical discs such as compact discs (CD-ROMs) and digital versatile discs (DVDs), magnetic media such as floppy disks, magnetic tapes or cassettes, and solid state semiconductor random access memory (RAM) devices, read-only memory (ROM) devices, electrically erasable programmable read-only memory (EEPROM) devices, flash memory devices, memory chips and combinations of the foregoing. Memory may be non-volatile or volatile. Memory may be physically attached to a processor, or remote from a processor. Memory may be removable or non-removable from a system including a processor. Memory may be operatively connected to a processor in such as way as to be accessible by a processor. Instructions stored by a memory may be based on a plurality of programming and / or markup languages known in the art, with non-limiting examples including the C, C++, C#, Python ™, MATLAB ™, Java ™, JavaScript ™, Perl ™, PHP ™, SQL ™, Visual Basic ™, Hypertext Markup Language (HTML), Extensible Markup Language (XML), and combinations of the foregoing. Instructions stored by a memory may also be implemented by configuration settings for a fixed-function device, gate array or programmable logic device.

[0033] "Processor" refers to one or more electronic hardware devices that is / are capable of reading and executing instructions stored on a memory to perform operations on data, whichmay be stored on a memory or provided in a data signal. The term "processor" includes a single device or a plurality of physically discrete, operatively connected devices despite use of the term in the singular. The plurality of processors may be arrayed or distributed. Non-limiting examples of processors include integrated circuit semiconductor devices and / or processing circuit devices referred to as computers, servers or terminals having single or multi-processor architectures, microprocessors, microcontrollers, microcontroller units (MCU), central processing units (CPU), field-programmable gate arrays (FPGA), application specific circuits (ASIC), digital signal processors, and combinations of the foregoing.

[0034] Figure 1 shows a perspective view an automotive style electric oil pump 100. The pump 100 includes a casing 102 which features an inlet port 110 and an outlet port 120. The casing 102 can also feature an electrical connector receptacle 104.

[0035] Referring additionally to the cross-sectional view of Figure 2 and the exploded views of Figures 3A and 3B, it will be seen that the casing 102 can be conveniently provisioned by a plurality of casing segments that can be fixed or releasably attached to one another, including an outlet segment 102A, a gerotor segment 102B, a motor segment 102C, and a cover segment 102D. These casing segments 102A-102D can be manufactured from a metal such as aluminum or from a plastic utilizing forming techniques well known in the forming arts.

[0036] The casing outlet segment 102A can be formed as monolithic structure such as through die casting to include a radial flat wall portion 112 and the inlet and outlet ports 110, 120. The casing outlet segment 102A can be attached to the casing gerotor segment 102B via a plurality of threaded fasteners 106 installed in threaded bores 108 and 109 (seen best in Figure 3B) formed in the casing outlet segment 102A and the casing gerotor segment 102B, respectively.

[0037] The casing gerotor segment 102B can be formed to include an outer cylindrical wall 124, an inner cylindrical wall 126 disposed radially inward of the outer cylindrical wall 124, and a journal bearing such as a tubular journal bearing 128 disposed radially inward of the inner cylindrical wall 126. The casing gerotor segment 102B can also include a radial wall 144 that interconnects the outer cylindrical wall 124, the inner cylindrical wall 126 and the tubular journal bearing 128. The radial wall 144 can include a bore 146 that communicates with the bore of the tubular journal bearing 128.

[0038] The outer cylindrical wall 124 can include a flange 129 having integrally formed mounting receptacles 131 and can include a first groove 132A for fitment of a first O-ring 134Atherein. This construction enables the pump 100 to be releasably installed into a larger assembly with corresponding mounting receptacles (no shown) aligned with the mounting receptacles 131 and configured to fluidly communicate with the pump inlet and outlet ports 110, 120. The outer cylindrical wall 124 can also include a second groove 132B for fitment of a second O-ring 134B therein, providing a sealing mechanism against casing motor segment 102C.

[0039] The casing motor segment 102C can be provisioned in the form of a cylinder that can be fixed to the outer cylindrical wall 124 of the casing gerotor segment 102B, such as by a press fit, interconnecting screw threads or weldment.

[0040] The cover segment 102D can be attached to the casing motor segment 102C such as through a screw threaded interconnection or press fit.

[0041] The inner cylindrical wall 126 of the casing gerotor segment 102B, the flat wall portion 112 of the casing outlet segment 102A, and the radial wall 144 of the casing gerotor segment 102B can define a pumping chamber 130. The tubular journal bearing 128 can be disposed in the pumping chamber 130 at a position that is offset from the center of the chamber 130. The tubular journal bearing 128 can depend from the radial wall 144 and be axially shorter than the outer and inner cylindrical walls 124, 126.

[0042] The casing cover segment 102D and the radial wall 144 of the casing gerotor segment 102B can define a motor compartment 148. The radial wall 144 of the casing gerotor segment 102B can function as an internal barrier segregating the casing 102 into a wet pumping chamber and a dry motor compartment and it will be appreciated that other structures, such as a non-integrated radial wall, a composite structure, or a film may be provisioned for this purpose.

[0043] A gerotor 150, comprising an inner rotor 150A and an outer rotor 150B, can be disposed in the pumping chamber 130. The inner rotor 150A can feature a central bore 151 configured to fit over the tubular journal bearing 128. A drive shaft 152, comprising a shank 152A and a head 152B, can be disposed within the tubular journal bearing 128, with the drive shaft head 152B projecting from the tubular journal bearing 128 and drivingly connected to the inner gerotor gear 150A, such as through a mortise joint. The gerotor inner and outer rotors 150A, 150B and the drive shaft head 152B can feature flat faces abutting the flat wall portion 112 of the casing outlet segment 102A. The drive shaft shank 152A can extend through the bore 146 of the radial wall 144 of casing gerotor segment 102B and into the motor compartment 148. An oil seal or radial shaft seal 154 can be disposed about the drive shaft shank 152A and within thebore 146 to seal the motor compartment 148 against ingress of oil from the pumping chamber 130.

[0044] The tubular journal bearing 128 defines the rotational axis of the pump.

[0045] An axial flux electric motor 160 comprising a rotor 160A and a stator 160B (seeFigs. 3A, 3B) can be disposed within the motor compartment 148. The rotor 160A interacts electromagnetically with the stator 160B through a magnetic air gap 162 (seen in Fig. 4). As will be seen, the axial flux motor 160 is quite compact in the axial direction.

[0046] The rotor 160A can include a permanent magnet structure 164 that is fixed relative to the drive shaft 152. Referring additionally to the isolated cross-sectional view of Figure 4, the permanent magnet structure 164 can comprise a back-iron disc 166 with a permanent magnet ring 168 adhered thereto, with the drive shaft 152 being fixed such as by press fit to the disc 166. The permanent magnet ring 168 can be segmented circumferentially into magnets of alternating pole faces, as indicated by stippled lines in the drawings.

[0047] The stator 160B can include a printed circuit board (PCB) 170 and a stator core 172.

[0048] The PCB 170 can carry electrical windings for a plurality of electrical phases. Various electrical stator winding configurations can be employed as known in the art per se, one of which is disclosed in W02023 / 082002 published May 19, 2023.

[0049] The stator core 172 can be formed, for example, from ferrite with a relatively high permeability yet relatively high electrical resistivity. The stator core 172 can be configured in the form of a toothless ring 174 (see Figs. 3A, 3B) mounted on a face of the PCB 170 distal to the magnetic air gap 162. In the illustrated embodiment the toothless stator core ring 174 is configured and disposed so as to overlap and be co-extensive with the permanent magnet ring 168. The radial wall 144 of the casing gerotor segment 102B can include a toroidal rebate 176 to support the stator core 172.

[0050] Figure 4 shows, schematically, a magnetic flux path (stippled lines 136) for a portion of the illustrated electric motor 160 in cross-sectional view, where it will be seen that the magnetic flux path extends through the stator core 172. The stator core 172 can provision a low reluctance path to complete flux loops between adjacent magnet poles of opposite polarity. This low reluctance path can concentrate flux density and, compared to a coreless stator, can improveflux alignment resulting in higher flux linkage between the stator and rotor, improving efficiency. The toothless nature of the illustrated stator core can reduce cogging torque in comparison to a toothed core.

[0051] A control printed circuit board alternatively referred to as a controller 180 can also be mounted in the motor compartment 148. The controller 180 carries electronics for commutating the motor and interfacing with other vehicular controls that can communicate operating set points to the controller such as speed, flow rate etc. The controller 180 can be mounted against the casing cover segment 102D which can function as a heat sink to radiate heat away from the controller.

[0052] In operation, the motor controller 180 commutates the windings stator to cause the rotor 160A to rotate. As the back iron disc 166 is fixed to the drive shaft 152, the drive shaft 152 rotates and it, in turn, rotates the gerotor inner rotor 150A. As is known in the gerotor art, the rotation of the gerotor inner rotor 150A induces rotation of the gerotor outer rotor 150B. The rotation of the gerotor 150 induces ingress of oil into the pumping chamber 130 via inlet 110 and egress of oil out of the pumping chamber 130 via outlet 120.

[0053] The controller 180 includes a processor and a memory, as will be understood by one skilled in the art. Examples of a memory and a processor are described elsewhere herein.

[0054] Some of the forces acting within the pump 100 will now be discussed in greater detail. Referring additionally to the partial cross-sectional view of the pump 100 in Figure 5, in operation there can be a relatively large pressure differential in the pumping chamber 130 between the suction side inlet 110 and the expulsion side outlet 120 resulting in a considerable transverse force TF acting against the gerotor 150. Absent preventative measures, the transverse force TF would act on the gerotor 150 which would induce the drive shaft 152 to tilt axially away from the nominal rotational axis of the pump 100. The tilt of the drive shaft 152 can be detrimental to the performance of the oil pump in that a tilted drive shaft could cause the flat faces of the gerotor 150 to lift off the flat wall portion 112 of the casing outlet segment 102A which would result in reduced performance as the efficiency of gerotor pumping action is dependent on tight tolerances in this area. Additionally, a tilted drive shaft 152 would induce wear in its journal bearing and result in a tilting of the electric motor rotor 160A against the stator 160B, the performance of which is also sensitive to small variations given that the air gap 162 can be quite small, on the order of about 0.25 to 1 mm. To handle the load presented by theforce TF prior art oil pumps have typically utilized a relatively long drive shaft seated in a relatively long bearing journal such that journal bearing segment labelled "JS" is generally at least about the same length as the height, labelled "GH", of the gerotor rotors 150, and typically larger.

[0055] The present disclosure provides two countermeasures which can be used the counteract the transverse force TF whilst attempting to achieve the objective of axial compactness. These countermeasures can be used jointly or in the alternative depending on the magnitude of the counteracting forces they generate.

[0056] First, it will be seen in the illustrated embodiment that the gerotor inner rotor 150A is supported transversely by an outer cylindrical wall 1280 of the tubular journal bearing 128 over which the gerotor inner rotor 150A is fitted. The bearing surfaces here are larger than the bearing surfaces inside the bore of the tubular journal bearing 128 and thus able to provide considerable support. In effect, utilizing both the inner and outer cylindrical walls of the tubular journal bearing 128 to support the gerotor inner rotor 150A more than doubles the effective bearing surfaces in this region, allowing the journal bearing segment JS to be compact. In some embodiments, the bearing support provided by outer cylindrical wall 1280 may be sufficient to resist entirely any appreciable axial tilt of the gerotor 150 or gerotor inner rotor 150A caused the transverse force TF.

[0057] Second, it should be appreciated that as the electric motor 160 utilizes a single sided rotor in an axial flux topology with a stator core, a continual magnetic attractive force (schematically represented by reference arrow MF) arises between the rotor 160A and stator 160B which acts in the axial direction to push the drive shaft head 152B against the flat wall portion 112 of the casing outlet segment 102A with a positive engagement, thus resisting the transverse force TF. The continual magnetic attractive force MF is generated between the permanent magnet structure 164 and the stator core 172 and is always present, not varying appreciably with the rotational speed of the gerotor or the pump output. The magnitude of the continual magnetic attractive force MF depends on the geometry of the permanent magnet structure 164 and the stator core 172, the specific materials used for these components, and the spacing of the magnetic air gap 162. Furthermore, as the illustrated toothless ring 174 of the stator core 172 is configured and arranged in a manner co-extensive with the permanent magnet ring 168 the continual magnetic attractive force MF is deployed circumferentially and thus generates a radially inward centering force that, by way of a friction normal, may counteract atleast in part the aforementioned tilting forces that arise in operation. These counteracting forces presented by electric motor 160 result in an overall pressure x velocity profile on the bearing surfaces of the gerotor inner rotor 150A and the plate 112 of the casing outlet segment 102A that is relatively stable over the pump operating range. In some embodiments, the magnitude of the continual magnetic attractive force MF may be large enough to, in isolation, inhibit tilting of the drive shaft 152 over a rated maximal rotational velocity of the pump 100 and a rated maximal pressure generated by the pump 100. In other embodiments, the combination of the bearing support provided by outer cylindrical wall 1280 and the magnitude of the continual magnetic attractive force MF may be sufficient to preclude tilting of the drive shaft 152 over a rated maximal rotational velocity of the pump 100 and a rated maximal pressure generated by the pump 100.

[0058] Figures 6-7 show a second embodiment of an electric oil pump 200, which a variant of pump 100.

[0059] Referring to Figure 6, oil pump 200 features a casing 202 having an inlet port 210 and an outlet port 220 that are disposed at different positions as compared to inlet and outlet ports 110 and 120, with the inlet port 210 being located circumferentially such that oil ingresses radially and the outlet port 220 being located axially such that oil egresses axially.

[0060] Referring additionally to the cross-sectional view of Figure 7, it will be seen that casing 202 has fewer segments than casing 102 in that casing 202 is provisioned by an outlet segment 202A, a main body segment 202B, and a cover segment 202C. These casing segments can be manufactured from a metal such as aluminum or from a plastic utilizing forming techniques well known in the forming arts.

[0061] The outlet segment 202A features the outlet port 220.

[0062] The casing body segment 202B can be formed to include an outer cylindrical wall224, an inner cylindrical wall 226 disposed radially inward of the outer cylindrical wall 224, and a journal bearing such as a tubular journal bearing 228 disposed radially inward of the inner cylindrical wall 226. The casing body segment 202B can also include a first radial wall 244A that interconnects the outer cylindrical wall 224, the inner cylindrical wall 226 and the tubular journal bearing 228. The radial wall 244 can include a bore 246 that communicates with the bore of the tubular journal bearing 228. The radial wall 244A can be formed to present a cavity 245 that fluidly communicates with the inlet port 210 (which is hidden from view in Fig. 7). The casingbody segment 202B can also include a second radial wall 244B that can mate with the casing outlet segment 202A to form a controller compartment 148B.

[0063] The casing cover segment 202C when mated to the casing body segment 202B defines a motor compartment 248A.

[0064] The inner cylindrical wall 226 of the casing body segment 202B, the casing outlet segment 202A, and the radial wall 244A of the casing body segment 202B can define a pumping chamber 230 which is in fluid communication with the inlet cavity 245 via a passageway 245P. The tubular journal bearing 228 can be disposed in the pumping chamber 230 at a position that is offset to the center of the chamber 230. The tubular journal bearing 228 can depend from the radial wall 244A and be axially shorter than the inner cylindrical walls 226.

[0065] The radial wall 244A of the casing body segment 202B provisions an internal barrier segregating the casing 202 into a wet pumping chamber and a dry motor compartment and it will be appreciated that other structures, such as a non-integrated radial wall, a composite structure, or a film may be provisioned for this purpose. For example, in some embodiments the radial wall 244A can be non-hermetic and a PCB stator 270 can be mounted against the radial wall 244A so as to provide a portion of the barrier segregating the casing 202 into a wet pumping chamber and a dry motor compartment. This would expose the PCB stator 270 to the flow of oil which may assist in cooling the stator.

[0066] A gerotor 250, comprising inner rotor 250A and an outer rotor 250B, can be disposed in the pumping chamber 230. The inner rotor 250A can feature a central bore 251 configured to fit over the tubular shaft journal bearing 228. A drive shaft 252, comprising a shank 252A and a head 252B, can be disposed within the tubular shaft journal bearing 228, with the drive shaft head 252B projecting from the tubular shaft journal bearing 228 and drivingly connected to the inner gerotor gear 250A, such as through a loose mortise joint. The gerotor inner and outer rotors 250A, 250B and the drive shaft head 252B can feature flat faces abutting a flat wall portion 212 of the casing outlet segment 202A. The drive shaft shank 252A can extend through the bore 246 of the radial wall 244A and into the motor compartment 248A. An oil seal or radial shaft seal 254 can be disposed about the drive shaft shank 252A and within the bore 246 to seal the motor compartment 248A against ingress of oil from the inlet cavity 245.

[0067] The tubular journal bearing 248 defines the rotational axis of the pump 200.

[0068] An axial flux electric motor 260 comprising a rotor 260A and a stator 260B can be disposed within the motor compartment 248A. The electric motor is substantially similar to motor 160 and features similar components that function in a similar manner, including a permanent magnet structure 264, comprising a back-iron disc 266 and a permanent magnet ring 268, the printed circuit board (PCB) stator 270 and a stator core 272. A controller 280 can be mounted in the controller compartment 248B.

[0069] Some of the forces acting within the pump 200 will now be discussed in greater detail. Referring additionally to the partial cross-sectional view of the pump 200 in Figure 8, in operation there can be a relatively large pressure differential in the pumping chamber 230 between the suction side inlet 210 and the expulsion side outlet 220 resulting in a considerable transverse force TF2 acting against the gerotor 250. Due to the differing axial positions of the inlet and outlet 210, 220, the transverse force TF2 will also have a larger axial component in comparison to pump 100 directed to the inlet passageway 245 from the outlet 220. Absent preventative measures, the transverse force TF2 would act on the gerotor 250 which would induce the drive shaft 252 to tilt axially away from the nominal rotational axis of the pump 200. The tilt of the drive shaft 252 can be detrimental to the performance of the oil pump in that a tilted drive shaft could cause the flat faces of the gerotor 250 to lift off the flat wall portion 212 of the casing outlet segment 202A which would result in reduced performance as the efficiency of gerotor pumping action is dependent on tight tolerances in this area. Additionally, a tilted drive shaft 252 would induce wear in its journal bearing and result in a tilting of the electric motor rotor 260A against the stator 260B, the performance of which is also sensitive to small variations given that the air gap 262 can be quite small, on the order of about 0.25 to 1 mm.

[0070] The present disclosure provides two countermeasures which can be used the counteract the transverse force TF2 whilst attempting to achieve the objective of axial compactness. These countermeasures can be used jointly or in the alternative depending on the magnitude of the counteracting forces they generate.

[0071] First, it will be seen in the illustrated embodiment that the gerotor inner rotor 250A is supported transversely by an outer cylindrical wall 2280 of the tubular journal bearing 228 over which the gerotor inner rotor 250A is fitted. The bearing surfaces here are larger than the bearing surfaces inside the bore of the tubular bearing journal 228 and thus able to provide considerable support. In effect, utilizing both the inner and outer cylindrical walls of the tubular bearing journal228 to support the gerotor inner rotor 250A more than doubles the effective bearing surfaces in this region, allowing the journal bearing segment JS2 to be compact relative to the overall axial length of the pump. In some embodiments, the bearing support provided by outer cylindrical wall 2280 may be sufficient to resist entirely any appreciable axial tilt of the gerotor 250 or gerotor inner rotor 250A caused by the transverse force TF2.

[0072] Second, it should be appreciated that as the electric motor 260 utilizes a single sided rotor in an axial flux topology with a stator core, a continual magnetic attractive force (schematically represented by reference arrow MF2) arises between the rotor 260A and stator 260B which acts in the axial direction to push the drive shaft head 252B against the flat wall portion 212 of the casing outlet segment 202A with a positive engagement, thus resisting the transverse force TF2. The continual magnetic attractive force MF2 is generated between the permanent magnet structure 264 and the stator core 272 and is always present, not varying appreciably with the rotational speed of the gerotor or the pump output. The magnitude of the continual magnetic attractive force MF2 depends on the geometry of the permanent magnet structure 264 and the stator core 272, the specific materials used for these components, and the spacing of the magnetic air gap 262. Furthermore, as the illustrated toothless ring 274 of the stator core 272 is configured and arranged in a manner co-extensive with the permanent magnet ring 268 the continual magnetic attractive force MF2 is deployed circumferentially and thus generates a radially inward centering force that, by way of a friction normal, may counteract at least in part the aforementioned tilting forces that arise in operation. These counteracting forces presented by electric motor 260 result in an overall pressure x velocity profile on the bearing surfaces of the gerotor inner rotor 250A and the flat wall 212 of the casing outlet segment 202A that is relatively stable over the pump operating range. In some embodiments, the magnitude of the continual magnetic attractive force MF2 may be large enough to, in isolation, inhibit tilting of the drive shaft 252 over a rated maximal rotational velocity of the pump 200 and a rated maximal pressure generated by the pump 200. In other embodiments, the combination of the bearing support provided by outer cylindrical wall 2280 and the magnitude of the continual magnetic attractive force MF2 may be sufficient to preclude tilting of the drive shaft 252 over a rated maximal rotational velocity of the pump 200 and a rated maximal pressure generated by the pump 200.

[0073] Note that in the second embodiment pump 200 the drive shaft head 252B can have a clearance 249 with the inner rotor 250A, for example, by squaring off the head 252Bwithin a cylindrical bore of the inner gerotor 25A. In this manner, the effective axial extent of the gerotor can be reduced to the coextensive axial lengths of the shank 252B and the inner gerotor 250A, denoted by dimension GH2 (which is smaller than the axial extent GH in the first embodiment pump 100), whereby the influence of the transverse force TF2 to tilt the drive shaft 252 can be reduced. Additionally, or alternatively, the axial length of the tubular journal bearing 228 within the inner gerotor 250A, indicated by the GH2 dimension, can be selected so that it is at least 50% of the actual axial length or thickness RH2 of the gerotor 250, to thereby inhibit or reduce the tendency of the inner gerotor 250A to tilt in the pumping chamber 230.

[0074] The continual magnetic force MF or MF2 has been shown in an orientation that urges the shaft head against the flat wall portion of the casing. However, in some embodiments the relative orientation of the permanent magnet structure and the stator may be reversed such the continual magnetic force MF or MF2 urges the shaft head away from the flat wall portion of the casing and instead urges the shaft head against an axially facing face 128F or 228F of the tubular journal bearing.

[0075] In some embodiments, the PCB stator may be replaced with an axial flux stator that utilizes wire windings installed over a core or yoke.

[0076] In still other embodiments the axial flux motor may be replaced with a radial flux motor such that the forces MF or MF2 are not present.

[0077] The shank and the head of the drive shaft have been shown to be separate components with differing geometries but those skilled in the art will appreciate that the head can be a simple unitary extension of the shank of the same cross-sectional dimension. The drive shaft has been shown as being connected to the inner rotor of the gerotor; however it will be appreciated by those skilled in the art that a gerotor can also function by driving the outer rotor and such embodiment is contemplated by this disclosure, wherein the drive shaft is drivingly connected to the other rotor.

[0078] Those skilled in the art will appreciate that a wide variety of other modifications may be made to the embodiments disclosed herein whilst conforming with the appended claims.

Claims

Claims1. An electric oil pump, comprising: a casing (102, 202); an internal barrier (144, 244A) segregating the pump into a wet pumping chamber (130, 230) and a dry motor compartment (148 248A), wherein the pumping chamber includes a fluid inlet (110, 210) and a fluid outlet (120, 220); a tubular journal bearing (154, 254), disposed in the pumping chamber, having an internal bore (1281, 2281) and an outer bearing wall (1280, 2280), the tubular journal bearing defining a rotational axis of the pump; a shaft seal (154, 254) disposed along the internal barrier; a gerotor (150, 250) having an inner rotor (150A, 250A) and outer rotor (150B, 250B), the gerotor inner rotor being mounted for rotation about the tubular journal bearing so as to bear against the outer bearing wall thereof; a drive shaft (152, 252) drivingly connected to the inner rotor and extending through the shaft seal into the dry motor compartment; and an electric motor (160, 260), disposed within the dry motor compartment, connected to the drive shaft.

2. An electric oil pump according to claim 2, wherein, in operation, a pressure differential arises in a direction transverse to the rotational axis which generates a transversely directed force (TF, TF2) on the gerotor, and wherein the gerotor inner rotor and the outer bearing wall of the tubular journal bearing are configured to counteract the transverse force arising from the pressure differential so as to preclude axial tilt of the drive shaft during operation.

3. An electric oil pump according to claim 2, wherein the pump operation includes operation at a maximal operating rotational velocity of the gerotor and a maximal operating pressure generated by the gerotor.

4. An electric oil pump according to claim 1, wherein: the drive shaft includes a shank (152A, 252A) and a head (152B, 252B) that has a larger radial breadth than a radial breadth of the shank; the head is drivingly connected to the gerotor inner rotor;the electric motor comprises a rotor (160A, 260A) and a stator (160B, 260B) operable to electromagnetically interact with one another via a magnetic air gap (162, 262); the rotor includes a permanent magnet structure (164, 264) fixed to the drive shaft and rotatable about the rotational axis; and the permanent magnet structure and the stator are configured to generate a continual magnetic attractive force (MF, MF2) directed along the rotational axis to press the drive shaft head against one of a wall (112, 212) of the pumping chamber orientated transverse to the rotational axis and an axially facing face (128F, 228F) of the tubular journal bearing, to thereby generate a transverse friction force.

5. An electric oil pump according to claim 4, wherein the stator is provisioned by a printed circuit board (PCB) (170, 270) and a magnetically permeable stator core (172, 272), the PCB being disposed transverse to the rotational axis and having a first face proximal to the magnetic air gap and a second, opposing, face distal to the magnetic air gap, the stator core being disposed adjacent to the second face of the PCB.

6. An electric oil pump according to claim 4, wherein the magnitude of the friction force is large enough to inhibit tilting of the drive shaft over an operating range of the pump due to a force arising from a pressure differential between the fluid inlet and fluid outlet which is applied to the gerotor in a direction transverse to the rotational axis.

7. An electric oil pump according to claim 6, wherein the operating range of the pump includes operation at a maximal operating rotational velocity of the gerotor and a maximal operating pressure generated by the gerotor.

8. An electric oil pump according to claim 4, wherein, in operation, support provided by the outer bearing wall to the gerotor inner rotor in combination with the magnitude of the transverse friction force is sufficient to preclude axial tilt of the drive shaft due to a force arising from a pressure differential between the fluid inlet and fluid outlet that is applied to the gerotor in a direction transverse to the rotational axis.

9. An electric oil pump according to claim 8, wherein the operating range of the pump includes operation at a maximal operating rotational velocity of the gerotor and a maximal operating pressure generated by the gerotor.

10. An electric oil pump according to claim 2, wherein the internal barrier includes an internal dividing wall (144, 244A) and the tubular journal bearing depends from the internal dividing wall.

11. An electric oil pump according to claim 2, wherein: the drive shaft includes a shank (152A, 252A) and a head (152B, 252B) that has a larger radial breadth than a radial breadth of the shank; the head is drivingly connected to the gerotor inner rotor; a clearance (249) is present between the shaft head and the inner rotor; and an axial length (GH2) of the tubular journal bearing within the inner gerotor at least 50% of the axial length (RH2) of the inner gerotor.

12. An electric oil pump, comprising: a casing (102, 202); an internal barrier (144, 244A) segregating the casing into a wet pumping chamber (130, 230) and a dry motor compartment (148, 248A); a fluid inlet (110, 210) and a fluid outlet (120, 220) for ingress and egress of oil into and out of the pumping chamber; a shaft seal (154, 254) disposed along the internal barrier; a journal bearing (128, 228) disposed in the pumping chamber, defining a rotational axis; a drive shaft (152, 252), including a shank (152A, 252A) and a head (152B, 252B), the shank mounted for rotation within the journal bearing about the rotational axis and extending through the shaft seal into the dry motor compartment, the head projecting from the journal bearing; a gerotor (150, 250) mounted for rotation in the pumping chamber, wherein the gerotor includes an inner rotor (150A, 250A) and an outer rotor (150B, 250B) and the head is drivingly connected to one of the inner and outer rotors; an electric motor (160) disposed within the dry motor compartment, the electric motor comprising a rotor (160A, 260A) and a stator (160B, 260B) operable to electromagneticallyinteract with one another via a magnetic air gap, wherein the rotor includes a permanent magnet structure (164, 264) fixed to the drive shaft and rotatable about the rotational axis; wherein the permanent magnet structure and the stator are configured to generate a continual magnetic attractive force (MF, MF2) directed along the rotational axis to press the drive shaft against one of a wall (112, 212) of the pumping chamber orientated transverse to the rotational axis and an axially facing face (128F, 228F) of the journal bearing, to thereby generate a transverse friction force, wherein the magnitude of the continual magnetic attractive force is sufficient to inhibit tilting of the drive shaft over an operating range of the pump due to forces arising from a pressure differential between the fluid inlet and fluid outlet which are applied to the gerotor in a direction transverse to the rotational axis.

12. An electric oil pump according to claim 11, wherein the stator is provisioned by a printed circuit board (PCB) (170, 270) and a magnetically permeable stator core (172, 272), the PCB being disposed transverse to the rotational axis and having a first face proximal to the magnetic air gap and a second, opposing, face distal to the magnetic air gap, the stator core being disposed adjacent to the second face of the PCB.

13. An electric oil pump according to claim 11, wherein the operating range of the pump includes operation at a maximal rated rotational velocity of the gerotor and a maximal rated pressure generated by the gerotor.

14. An electric oil pump according to claim 12, wherein: the journal bearing is a tubular journal bearing having an outer cylindrical wall (1280, 2280) and an internal bore (1281, 2281); the shank is journalled in the internal bore; the gerotor inner rotor is rotatingly mounted about the tubular journal bearing so as to bear against the outer cylindrical wall thereof.

15. An electric oil pump according to claim 14, wherein: the head has a radial breadth that is larger than a radial breadth of the shank; the gerotor inner rotor is drivingly connected to the head;a clearance (249) is present between the head and the inner rotor; and an axial length (GH2) of the tubular journal bearing within the inner gerotor at least 50% of the axial length (RH2) of the inner gerotor.

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