Electric pump

Abstract

Electric pump comprising: - a gerotor comprising an outer rotor (4) and an inner rotor (3), the outer rotor (4) assembled around the inner rotor (3), the outer rotor (4) and the inner rotor (3) being configured to pump a fluid, - an electric outrunner motor comprising a stator (7, 8, 9) and a rotor (6) being configured to drive the gerotor, the stator (7, 8, 9) and the rotor (6) assembled around the gerotor.

Description

[0001] DESCRIPTION

[0002] ELECTRIC PUMP

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to high-power density electric pumps, more specifically to oil pumps.

[0005] BACKGROUND OF THE INVENTION

[0006] Electric oil pumps are used throughout the industry. In this type of systems, oil pumps are driven by electric motors, allowing the pump speed to be easily varied and controlled, resulting in controlled pump characteristics, like flow and pressure.

[0007] Furthermore, the motors used in these pumps tend to be electronically commuted, which means no motor brushes are needed, meaning they are reliable, maintenance free and very efficient compared to their brushed counterparts.

[0008] The printed circuit board (PCB) unit may also incorporate input / output central processing units (CPU), which allow the system to read and interpret input signals, compute the speed or torque to be applied to the pump and return any faults or malfunctions.

[0009] Several type of pumps can be used depending on the application. Often, when the fluid to be pumped is oil, and size and efficiency are required, gerotor pumps are used. These are a type of positive displacement pump that offer a compact size in relation their pumping capabilities, while being comprised of only two moving parts, an outer rotor and an inner rotor.

[0010] In a gerotor, the inner rotor has n teeth, while the outer rotor has n + 1 teeth, with n defined as a natural number greater than or equal to 2. The axis of the inner rotor is offset from the axis of the outer rotor and both rotors rotate on their respective axes.There are several possibilities for the electric motor. Often a brushless DC electric motor (BLDC) or permanent magnet synchronous motor (PMSM) motor is used.

[0011] A brushless DC electric motor (BLDC), also known as an electronically commutated motor, is a synchronous motor using a direct current (DC) electric power supply. It uses an electronic controller to switch DC currents to the motor windings producing magnetic fields that effectively rotate in space and which the permanent magnet rotor follows.

[0012] A permanent magnet synchronous motor (PMSM) is a synchronous electric motor whose inductor consists of permanent magnets.

[0013] These motors have two distinct architectures: inrunner and outrunner. In case of an inrunner motor, the rotor is located on the inside of the stator. In case of the outrunner motor, the rotor is located on the outside of the stator.

[0014] The inrunner architecture is, by far, the most widespread, owing to the placement of the stator in contact with the motor housing, allowing for better cooling compared to the outrunner type, where the stator is surrounded by the rotor, meaning copper, or winding losses, in the form of heat cannot be so easily dissipated.

[0015] Provided the stator can be cooled though, the outrunner architecture provides higher torque and power densities in relation to size. This is the reason why these motors are used in drone propulsion, where power density is paramount. The propellers high speed air slipstream results in a powerful heat convection exchange that allows the stator to be efficiently cooled.

[0016] There are also known dry rotors and wet rotors in a circulation pump. In a dry rotor the electric motor does not come into contact with the fluid.SUMMARY OF THE INVENTION

[0017] It is an object of the present invention an electric pump that provides a high-power density in relation to size.

[0018] The electric pump comprises:

[0019] - a gerotor comprising an outer rotor and an inner rotor, the outer rotor assembled around the inner rotor, the outer rotor and the inner rotor being configured to pump a fluid, - an electric outrunner motor comprising a stator and a rotor being configured to drive the gerotor, the stator and rotor assembled around the gerotor.

[0020] Both elements, the gerotor and the electric outrunner motor, are located in a housing that allows to assemble the electric outrunner motor around the gerotor.

[0021] The claimed configuration allows a very compact electric pump.

[0022] DESCRIPTION OF THE FIGURES

[0023] To complete the description and to provide for a better understanding of the invention, drawings are provided. Said drawings form an integral part of the description and illustrate preferred embodiments of the invention. The drawings comprise the following figures.

[0024] Figure 1 shows a front view of an embodiment of the invention of a dry rotor architecture.

[0025] Figure 2 shows a cut view (A-A) of the embodiment of figure 1.

[0026] Figure 3 shows a front view of an embodiment of the invention of a wet rotor architecture.

[0027] Figure 4 shows a cut view (C-C) of the embodiment of figure 3.

[0028] Figure 5 shows a cut view (B-A) of the embodiment of figure 1.Figure 6 shows a cut view (D-C) of the embodiment of figure 3.

[0029] DETAILED DESCRIPTION OF THE INVENTION

[0030] Figures 1 to 6 show embodiments of the invention in which the electric pump comprises:

[0031] - a gerotor comprising an outer rotor (4) and an inner rotor (3), the outer rotor (4) assembled around the inner rotor (3), the outer rotor (4) and the inner rotor (3) being configured to pump a fluid,

[0032] - an electric outrunner motor comprising a stator (7, 8, 9) and a rotor (6) being configured to drive the gerotor, the stator (7, 8, 9) and rotor (6) assembled around the gerotor.

[0033] In an embodiment, the stator (7, 8, 9) comprises a stator core (7), stator windings (8).

[0034] In the shown embodiments the electric pump comprises a housing (1) enclosing the gerotor and the electric outrunner motor.

[0035] The electric pump may also comprise a front cover (16) of the housing (1). In an embodiment, it may also comprise a back cover (15).

[0036] In an embodiment, the gerotor comprises a shaft (5), the inner rotor (3), the outer rotor (4) and the rotor (6) of the electric outrunner motor being rotatable around this shaft (5).

[0037] The electric pump also comprises a PCB (10) that in the shown embodiment is located annexed to the back cover (15).

[0038] In an embodiment, the electric pump comprises an inner housing (2) enclosing the gerotor. In this embodiment the electric outrunner motor is assembled around the inner housing (2), thus, the stator (7, 8, 9) and the rotor (6) are assembled around the inner housing (2).

[0039] In an embodiment, the electric pump comprises ribs (11) extending between the housing (1) and the inner housing (2). Ribs (11) may be added where desirable to attain required mechanical sturdiness. The housing (1) comprises a connector (12) and pins (13).In an embodiment the electric outrunner motor rotor (6) is assembled around the electric outrunner motor stator (7, 8, 9). This has the technical advantage of provided a better cooling of the motor stator (7, 8, 9).

[0040] The electric outrunner motor stator (7, 8, 9) can be cooled by means of convection and conduction heat transfer. The gerotor inner rotor (3), driven by the shaft (5), drives the gerotor outer rotor (4), resulting in oil being pumped. The oil circulation in the gerotor (3, 4) cools the inner housing (2) walls by means of heat convection. The stator core (7) is cooled by means of heat conduction, owing to the surface contact with the inner housing (2) that encloses the gerotor. The stator windings (8) are cooled via heat conduction owing to the surface contact with the stator core (7). The most demanding system operation condition in terms of the motor current consumption, resulting in higher copper losses (IR2), is for lower oil temperatures and higher oil viscosity and density. Heat dissipation from the electric stator (7, 8, 9) is the highest at lower oil temperatures and higher temperature gradient.

[0041] In the embodiment in which an inner housing (2) is provided, the electric outrunner motor stator (7, 8, 9) is assembled around the inner housing (2). Given the stator (7,8,9) is assembled around the inner housing (2) it allows the pump to be in a tight configuration.

[0042] Given the motor is of the outrunner architecture, means assembling the stator (7, 8, 9) onto the housing (1) in a sturdy overall system assembly, is a challenge, because the stator (7,8, 9) outer wall is surrounded by the rotor (6). Preventing a direct contact between the stator (7, 8, 9) outer wall and the housing (1 ) inner wall is wanted. It is addressed by using the inner housing (2) outer wall and the stator core (7, 8, 9) inner wall. The inner housing (2) is part of the housing (1). Thus, another advantage is that the electric pump is more sturdy owing to the fact the electric outrunner motor stator (7, 8, 9) is assembled onto the inner housing (2).

[0043] Therefore, the electric outrunner motor stator (7, 8, 9) is assembled around the inner housing (2) which is the gerotor housing, thus making use of the electric stator (7, 8, 9) inner void. It makes the electric pump more compact as previously stated.Figure 1 shows a front view of an embodiment of the invention of a dry rotor architecture with the back cover (15), the PCB (10) and the electric outrunner motor rotor (6) hidden. Figure 2 shows a cut view (A-A) of the dry motor of figure 1.

[0044] In the embodiment of a dry motor, the stator comprises a stator core (7) and stator windings (8).

[0045] Figure 3 shows a front view of an embodiment of the invention of a wet rotor architecture with the back cover (15), the PCB (10) and the electric outrunner motor rotor (6) hidden. Figure 4 shows a cut view (C-C) of the wet rotor of figure 3.

[0046] In the embodiments in which a wet rotor is depicted, a path needs to be found to connect the stator phase wires (14) between the stator windings (8) and the PCB (10). The challenge lies in the fact the electric outrunner motor rotor (6) surrounds the stator windings (8), preventing a direct connection to the PCB (10). It is solved by means of overmolding the stator phase windings (14) in the body of the stator core (7). Thus, the electric outrunner motor stator (7, 8, 9) comprises overmolded stator phase windings (9).

[0047] In overmoulding the windings are overmoulded with a synthetic material. In this way, the winding goods are optimally protected.

[0048] As previously stated, the dry rotor architecture is shown in figures 1 , 2 and 5. In this architecture the oil circuit does not get in contact with the electric outrunner motor rotor (6) and stator (7, 8, 9).

[0049] The housing (1) comprises a suction port (17) configured to suction the fluid to be compressed between the outer rotor (4) and an inner rotor (3).

[0050] More specifically, the housing (1) comprises a front cover (16), the front cover (16) comprising the suction port (17).

[0051] In the embodiment of figure 5, the suction port (7) is in fluidic communication with the space between the outer rotor (4) and the inner rotor (3).According to the above, oil, for instance, enters the electric pump via the front cover (16) suction port (17). Oil is compressed by the gerotor and exits the gerotor in a high-pressure chamber (20). The high-pressure chamber (20) is located annexed to the front cover (16). In an embodiment, the housing (1) comprises an outlet (22).

[0052] In an embodiment, the housing (1) comprises a channel (21) and an outlet (22) so that the fluid runs through the channel (21) from the high-pressure chamber (20) and exits the electric pump via the outlet (22). In the shown embodiment, the fluid makes 90 degrees turn back into the housing (1).

[0053] Given the shaft (5) is in direct contact with the housing (1), the body shaft (5) hole needs to be lubricated. Oil flows into the housing shaft support but is not allowed to get in contact with the electric outrunner motor stator (7, 8, 9) and rotor (6) by means of a radial sealant (23).

[0054] The suction port (17) and outlet (22) positions depend on the specific interface on which the electric pump is mounted. If the specific interface allows the outlet (22) to be located within the gerotor outer rotor (4), there is no need for the high-pressure chamber (20) and channel (21), resulting in smaller flow head losses.

[0055] Wet rotor architecture is shown in figures 3, 4 and 6. In this architecture the oil circuit is such that oil is allowed to flow around the electric outrunner motor rotor (6) and stator (7, 8, 9).

[0056] As previously stated, the housing (1) comprises the suction port (17) configured to suction the fluid to be compressed between the outer rotor (4) and an inner rotor (3). More specifically, oil enters the electric pump via the gerotor (3,4) suction port (17) located in the front cover (16).

[0057] In this embodiment, the suction port (7) is in fluidic communication with the electric outrunner motor stator (7, 8, 9). The electric outrunner motor stator is in fluidic communication with the space between the outer rotor (4) and the inner rotor (3) such that the fluid is configured to move from the suction port (7) to the electric outrunner motor stator (7, 8, 9) and afterwards to the space between the outer rotor (4) and the inner rotor (3) for its compression. Thus, oil then enters the gerotor via a gerotor body suction port (18).In an embodiment, the electric outrunner motor stator (7, 8, 9) is in fluidic communication with the space between the outer rotor (4) and the inner rotor (3) through the inner housing (2). Thus, oil then enters the gerotor via an inner housing (2) suction port (19).

[0058] This primary oil flow generates a secondary oil flow around the electric outrunner motor rotor (6) and stator (7, 8, 9), especially at high oil temperatures and low oil viscosities. As oil is allowed to be in contact with the electric outrunner motor rotor (6) and stator (7, 8, 9), the stator core (7) and stator windings (8) need to be insulated with the overmolded stator phase windings (9). On the other hand, there is no need for the radial sealant (23).

[0059] Oil is compressed and exits the gerotor into a high-pressure chamber (20). The high-pressure chamber (20) is located annexed to the front cover (16).

[0060] In an embodiment, the housing (1) comprises a channel (21) and an outlet (22) so that the fluid runs through the channel (21) and exits the electric pump via the outlet (22). In the shown embodiment, the fluid makes 90 degrees turn back into the housing (1).

[0061] The suction port (17) and outlet (22) positions depend on the specific interface on which the electric pump is mounted. If the specific interface allows the outlet (22) to be located within the gerotor outer rotor (4), there is no need for the high-pressure chamber (20) and channel (21), resulting in smaller flow head losses.

Claims

CLAIMS1.- Electric pump, characterized in that it comprises:- a gerotor comprising an outer rotor (4) and an inner rotor (3), the outer rotor (4) assembled around the inner rotor (3), the outer rotor (4) and the inner rotor (3) being configured to pump a fluid,- an electric outrunner motor comprising a stator (7, 8, 9) and a rotor (6) being configured to drive the gerotor, the stator (7, 8, 9) and the rotor (6) assembled around the gerotor.2.- Electric pump, according to claim 1, wherein the electric pump comprises a housing (1) enclosing the gerotor and the electric outrunner motor and an inner housing (2) enclosing the gerotor, the electric outrunner motor being assembled around the inner housing (2).3.- Electric pump, according to claim 2, wherein it comprises ribs (11) extending between the housing (1) and the inner housing (2).4.- Electric pump, according to any preceding claim, wherein the electric outrunner motor rotor (6) is assembled around the electric outrunner motor stator (7, 8, 9).5.- Electric pump, according to claims 2 or 3 and 4, wherein the electric outrunner motor stator (7, 8, 9) is assembled around the inner housing (2).6.- Electric pump, according to any preceding claim, wherein the electric outrunner motor stator (7, 8, 9) comprises overmolded stator phase windings (9).7.- Electric pump, according to any preceding claim 2 to 6, wherein the housing (1) comprises a suction port (17) configured to suction the fluid to be compressed between the outer rotor (4) and an inner rotor (3).8.- Electric pump, according to claim 7, wherein the suction port (7) is in fluidic communication with a space between the outer rotor (4) and the inner rotor (3).9.- Electric pump, according to claim 7, wherein the suction port (7) is in fluidic communication with the electric outrunner motor stator (7, 8, 9), the electric outrunner motor stator (7, 8, 9) being in fluidic communication with a space between the outer rotor (4) and the inner rotor (3) such that the fluid is configured to move from the suction port (7) to the electric outrunner motor stator (7, 8, 9) and afterwards to the space between the outer rotor (4) and the inner rotor (3) for its compression.10.- Electric pump, according to claim 9 and 2, wherein the electric outrunner motor stator (7, 8, 9) is in fluidic communication with the space between the outer rotor (4) and the inner rotor (3) through a suction port (19) in the inner housing (2).11.- Electric pump, according to any preceding claim 8 to 10, wherein the housing (1) comprises a front cover (16), the front cover (16) comprising the suction port (17).12.- Electric pump, according to any preceding claim 2 to 11, wherein the housing (1) comprises an outlet (22).

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