Electric pump

Abstract

To provide an electric pump which can inhibit increase of a pressure of a fluid in a motor chamber.SOLUTION: One embodiment of an electric pump of the invention includes: a motor part 3 having a shaft rotatable around a center axis; a pump part 40 which is connected to one end in an axial direction of the shaft and driven by power of a motor to pump a fluid; and a housing which houses the motor and the pump part. The housing is provided with: a motor chamber in which the motor part is disposed; a pump chamber in which the pump part is disposed; a supply path F1 for causing the fluid to flow from the pump chamber into the motor chamber; and a return path F2 for returning the fluid from the motor chamber to the pump chamber. A passage cross section area of the return path is larger than a passage cross section area of the supply path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric pump. [Background technology]

[0002] In the past, electric pumps that include a pump section and a motor section that rotates the pump section have sometimes had problems with temperature rise in the motor. Patent Document 1 discloses a structure for a pump device that includes an electric motor, in which the arrangement space of the pump section and the arrangement space of the motor section are connected by a suction-side communication passage and a discharge-side communication passage, and part of the oil discharged from the pump section is circulated around the motor section to suppress temperature rise in the electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-025127 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional electric pumps, the amount of fluid pumped from the pump unit to the motor unit's installation space may be greater than the amount of fluid returning from the motor's installation space to the pump unit, causing a problem of increased pressure in the motor installation space and imposing a load on the housing.

[0005] In view of the above circumstances, one aspect of the present invention has an object to provide an electric pump that can suppress an increase in fluid pressure in a motor chamber. [Means for solving the problem]

[0006] One aspect of the electric pump of the present invention includes a motor unit having a shaft rotatable about a central axis, a pump unit connected to one axial end of the shaft and driven by the power of the motor unit to pump a fluid, and a housing that accommodates the motor unit and the pump unit. The housing is provided with a motor chamber in which the motor unit is disposed, a pump chamber in which the pump unit is disposed, a supply path for allowing the fluid to flow from the pump chamber to the motor chamber, and a return path for returning the fluid from the motor chamber to the pump chamber. A flow path cross-sectional area of ​​the return path is larger than that of the supply path. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide an electric pump that can suppress an increase in fluid pressure in a motor chamber. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an electric pump according to an embodiment. [Figure 2] FIG. 2 is a front view of the bottom wall of one embodiment. [Figure 3] FIG. 3 is a partial cross-sectional view of an electric pump according to one embodiment. [Figure 4] FIG. 4 is a front view of the bottom wall portion of the second modification. [Figure 5] FIG. 5 is a partial cross-sectional view of the electric pump of the third modification. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the following description, figures show an XYZ coordinate system. The Y axis indicates the direction in which a central axis J in the embodiment described below extends. The central axis J shown in each figure is a virtual axis. In the following description, the direction in which the central axis J extends, i.e., the direction parallel to the Y axis, is referred to as the "axial direction." The side of the axial direction Y toward which the arrow of the Y axis points (+Y side) is one axial side, and the side of the axial direction Y opposite to the side toward which the arrow of the Y axis points (-Y side) is the other axial side. The radial direction centered on the central axis J is simply referred to as the "radial direction." The circumferential direction centered on the central axis J is simply referred to as the "circumferential direction." The Z axis indicates the up-down direction when the electric pump 100 of the embodiment is installed. The side of the up-down direction Z toward which the arrow of the Z axis points (+Z side) is the upper side, and the side of the up-down direction Z opposite to the side toward which the arrow of the Z axis points (-Z side) is the lower side. The X axis indicates a direction perpendicular to both the axial direction Y and the up-down direction Z.

[0010] The posture of the electric pump 100 in the vertical direction Z described below is an example, and the actual positional relationship may be one other than the positional relationship indicated by these names.

[0011] (electric pump) 1 is a cross-sectional view of an electric pump 100 according to this embodiment. The electric pump 100 is attached to, for example, a device mounted on a vehicle. The device to which the electric pump 100 is attached may be an automatic transmission or a drive unit that drives the axles of the vehicle.

[0012] In the following description, the device to which the electric pump 100 is attached is referred to as the attachment target device 5. The electric pump 100 is, for example, an electric oil pump that supplies oil to devices mounted on a vehicle. The electric pump 100 is connected to a flow path provided in the attachment target device 5 via an intake port 44c and an outlet port 43c.

[0013] The electric pump 100 includes a motor unit 3, a control unit 70, a pump unit 40, and a housing 10. The housing 10 accommodates the motor unit 3, the control unit 70, and the pump unit 40.

[0014] (Motor section) The motor unit 3 is accommodated inside the motor housing 11. In the axial direction Y, the motor unit 3 is disposed on one axial side (+Y) of the control unit 70 and on the other axial side (-Y) of the pump unit 40. The motor unit 3 has a rotor 20, a stator 30, and a terminal unit 60.

[0015] The rotor 20 is rotatable about a central axis J. The rotor 20 has a rotor core 21, a magnet 22, and a shaft 23. That is, the motor section 3 has the shaft 23 that is rotatable about the central axis J. The magnet 22 and the shaft 23 are fixed to the rotor core 21. The shaft 23 extends in the axial direction Y about the central axis J. In this embodiment, the shaft 23 is a hollow shaft. However, the shaft 23 may be a solid shaft.

[0016] The stator 30 is disposed radially outside the rotor 20. The stator 30 faces the rotor 20 with a gap in the radial direction. The stator 30 has a stator core 31, an insulator 32, and a coil portion 33. The stator core 31 surrounds the rotor core 21 from the radial outside. The outer peripheral surface of the stator core 31 is fixed to the cylindrical portion 11a of the motor housing 11. The stator core 31 has an annular core back portion 31a and a plurality of teeth 31b that protrude radially inward from the inner peripheral surface of the core back portion 31a. The plurality of teeth 31b are disposed at equal intervals along the circumferential direction. The coil portion 33 is attached to the teeth 31b via the insulator 32. The coil portion 33 is configured by winding a coil wire. The coil wire is drawn out from the coil portion 33.

[0017] The coil wires drawn out from the stator 30 are connected to the terminal unit 60. The terminal unit 60 is disposed between the stator 30 and the control unit 70. The terminal unit 60 has a plurality of terminal members. The terminal members relay the coil wires to the control unit 70.

[0018] (circuit board) The control unit 70 is located on the other axial side (-Y) of the motor unit 3. The control unit 70 is connected to the motor unit 3. The control unit 70 controls the power supplied to the coil unit 33. In this way, the control unit 70 controls the motor unit 3. The control unit 70 has a circuit board 71 that extends in a direction perpendicular to the axial direction Y. The circuit board 71 is arranged on the central axis J. A control IC, an inverter, a power supply circuit, and the like that drive and control the motor unit 3 are mounted on the circuit board 71. Terminal members of the terminal unit 60 are connected to the circuit board 71.

[0019] (housing) The housing 10 accommodates the motor section 3, the control section 70, and the pump section 40 inside. The housing 10 is provided with a motor chamber 10A and a pump chamber 10B. The motor section 3 and the control section 70 are disposed in the motor chamber 10A. On the other hand, the pump section 40 is disposed in the pump chamber 10B. The end of the shaft 23 on one axial side (+Y) is disposed in the pump chamber 10B. On the other hand, the end of the shaft 23 on the other axial side (-Y) is disposed in the motor chamber 10A.

[0020] The housing 10 has a lid portion 13, a motor housing 11, and a pump cover 19. The lid portion 13, the motor housing 11, and the pump cover 19 are separate members. The lid portion 13 is fixed to the other axial end of the motor housing 11. The pump cover 19 is fixed to one axial end of the motor housing 11. The motor chamber 10A is a space surrounded by the lid portion 13 and the motor housing 11. The pump chamber 10B is a space surrounded by the pump cover 19 and the motor housing 11.

[0021] (Lid) The lid portion 13 accommodates the control unit 70 therein. The lid portion 13 also covers the motor chamber 10A from the other axial side (-Y). The lid portion 13 is made of, for example, resin. The lid portion 13 has a board surrounding portion 13a, a plurality of fixing claw portions 13b, and a board cover portion 13c.

[0022] The substrate surrounding portion 13a has a substantially circular ring shape centered on the central axis J. The substrate surrounding portion 13a surrounds the control portion 70 from the radially outer side. A second groove portion 13g is provided on the outer peripheral surface of the substrate surrounding portion 13a. The second groove portion 13g opens radially outward. The second groove portion 13g is provided around the entire circumference of the outer peripheral surface of the substrate surrounding portion 13a. A second O-ring 2b is accommodated in the second groove portion 13g. The second O-ring 2b extends in a circular ring shape centered on the central axis J.

[0023] The fixed claws 13b extend from the substrate surrounding portion 13a toward one axial side (+Y). The fixed claws 13b are arranged side by side along the circumferential direction. The tips of the fixed claws 13b are provided with protrusions that protrude radially inward.

[0024] The board cover portion 13c covers the control unit 70 from the other axial side. In this way, the board cover portion 13c protects the control unit 70. In this embodiment, the board cover portion 13c is adhesively fixed to the board enclosure portion 13a from the other axial side (-Y).

[0025] (Motor housing) The motor housing 11 has a generally cylindrical shape and extends in the axial direction Y around a central axis J. The motor housing 11 accommodates the motor section 3 and the pump section 40. The motor housing 11 has a cylindrical section 11a, a bottom wall section 11d, and a pump surrounding section 11h.

[0026] The cylindrical portion 11a has a cylindrical shape that extends in the axial direction Y around the central axis J. The cylindrical portion 11a surrounds the motor portion 3 from the radial outside. The cylindrical portion 11a also surrounds the motor chamber 10A from the radial outside. A lid portion 13 is connected to the end of the cylindrical portion 11a on the other axial side (-Y). As a result, the opening of the cylindrical portion 11a on the other axial side (-Y) is covered by the lid portion 13.

[0027] The outer peripheral surface of the cylindrical portion 11a is provided with a locking groove portion 11c and a first groove portion 11g. The locking groove portion 11c and the first groove portion 11g are provided around the entire outer peripheral surface of the cylindrical portion 11a. The locking groove portion 11c and the first groove portion 11g open radially outward.

[0028] The locking groove 11c is located at the end of the outer peripheral surface of the cylindrical portion 11a on the other axial side (-Y). The fixing claw 13b is disposed radially outward from the end of the cylindrical portion 11a on one axial side (+Y). The protrusion of the fixing claw 13b engages with the locking groove 11c. This connects the cover 13 to the motor housing 11.

[0029] The first groove 11g is located on one axial side (+Y) of the locking groove 11c. A first O-ring (sealing member) 2a is housed in the first groove 11g. The first O-ring 2a extends in an annular shape around the central axis J.

[0030] The bottom wall portion 11d extends in a direction intersecting the axial direction Y. The bottom wall portion 11d is substantially annular in shape with the central axis J as its center. The radial outer edge of the surface of the bottom wall portion 11d facing the other axial side is connected to one axial side (+Y) of the cylindrical portion 11a. The bottom wall portion 11d is located on one axial side (+Y) of the motor chamber 10A and on the other axial side (-Y) of the pump chamber 10B. The bottom wall portion 11d separates the motor chamber 10A and the pump chamber 10B.

[0031] The bottom wall portion 11d is provided with a shaft support hole 11j and a communication hole 11k. The shaft support hole 11j and the communication hole 11k penetrate the bottom wall portion 11d in the axial direction Y. As a result, the shaft support hole 11j and the communication hole 11k connect the motor chamber 10A and the pump chamber 10B.

[0032] The shaft support hole 11j is circular and has a center on the central axis J. The shaft 23 is passed through the shaft support hole 11j. The inner diameter of the shaft support hole 11j is slightly larger than the outer diameter of the shaft 23. The shaft support hole 11j rotatably supports the shaft 23 on its inner circumferential surface. That is, the bottom wall portion 11d functions as a sliding bearing.

[0033] A shaft support portion 11e is provided on the surface of the other axial side (-Y) of the bottom wall portion 11d. The shaft support portion 11e is cylindrical and protrudes from the bottom wall portion 11d toward the other axial side (-Y). The shaft support portion 11e extends along the inner edge of the shaft support hole 11j. The inner circumferential surface of the shaft support portion 11e is continuously connected to the shaft support hole 11j. In other words, the inner circumferential surface of the shaft support portion 11e forms part of the inner circumferential surface of the shaft support hole 11j.

[0034] The bottom wall portion 11d covers the pump portion 40 from the other axial side (-Y). The bottom wall portion 11d has a first opposing surface 11f that faces one axial side (+Y) and faces the pump portion 40. The first opposing surface 11f is provided with a first suction side groove portion (first recess) 44a, a first discharge side groove portion (second recess) 43a, and a communicating groove portion (groove portion) 11s. The first suction side groove portion 44a, the first discharge side groove portion 43a, and the communicating groove portion 11s are recessed toward the other axial side (-Y).

[0035] FIG. 2 is a front view of the bottom wall 11d of this embodiment. As shown in FIG. 2, the first suction side groove 44a and the first discharge side groove 43a are each arc-shaped grooves extending circumferentially about the central axis J. The first suction side groove 44a and the first discharge side groove 43a open to one axial side (+Y). The first suction side groove 44a and the first discharge side groove 43a are provided at different circumferential positions. The first suction side groove 44a and the first discharge side groove 43a are located on opposite sides of the central axis J. In addition, the end of the communicating hole 11k on one axial side (+Y) opens to the bottom surface of the first suction side groove 44a.

[0036] The communicating groove 11s extends linearly in the radial direction. The radially inner end of the communicating groove 11s opens into the shaft support hole 11j. The radially outer end of the communicating groove 11s opens into the first discharge groove 43a. In other words, the communicating groove 11s connects to the shaft support hole 11j and the first discharge groove 43a. The opening of the communicating groove 11s in the first discharge groove 43a is located approximately in the center of the length of the first discharge groove 43a.

[0037] In this embodiment, a step 11n is provided at the radially inner end of the communicating groove 11s. The depth of the communicating groove 11s is greater at the step 11n. That is, the position of the bottom surface of the communicating groove 11s is recessed toward the other axial side (-Y) at the step 11n compared to other portions. According to this embodiment, the step 11n is provided at the radially inner end of the communicating groove 11s, thereby ensuring a wide radially inner opening of the communicating groove 11s in the axial direction. This allows the fluid to be supplied to a wide range in the axial direction relative to the outer peripheral surface of the shaft 23. This makes it easier for the fluid to lubricate the inner peripheral surface of the shaft support hole 11j and the outer peripheral surface of the shaft 23.

[0038] The bottom surface of the step portion 11n may be inclined radially inward toward the other axial side (-Y). In this case, the fluid in the communication groove portion 11s can be smoothly supplied to the shaft support hole 11j at the step portion 11n.

[0039] Furthermore, the groove width of the step portion 11n may gradually increase radially inward. In this case, the fluid can be supplied to a wider area in the circumferential direction relative to the outer circumferential surface of the shaft 23. This makes it easier for the fluid to lubricate the area between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23.

[0040] As shown in FIG. 1, the pump surrounding portion 11h is cylindrical and protrudes from the bottom wall portion 11d to one side in the axial direction. The pump surrounding portion 11h surrounds the pump portion 40 from the radially outer side. That is, the pump chamber 10B is provided radially inside the pump surrounding portion 11h. The pump surrounding portion 11h opens to one side in the axial direction. The inner circumferential surface of the pump surrounding portion 11h is circular and eccentric with respect to the central axis J. The inner circumferential surface of the pump surrounding portion 11h faces the outer circumferential surface of the outer rotor 42. The inner circumferential surface of the pump surrounding portion 11h rotatably supports the outer circumferential surface of the outer rotor 42.

[0041] (Pump cover) The pump cover 19 is substantially disk-shaped and centered on the central axis J. The pump cover 19 is disposed on one axial side (+Y) of the pump section 40. The pump cover 19 covers the pump section 40 from one axial side (+Y). Therefore, the pump cover 19 and the bottom wall section 11d sandwich the pump section 40 from both axial sides. The pump cover 19 is fixed to the end of the inner circumferential surface of the pump surrounding section 11h on one axial side (+Y). The pump cover 19 closes the opening of the pump surrounding section 11h from one axial side.

[0042] The pump cover 19 has a second opposing surface 19f, a suction portion 19a, an intake port 44c, and a discharge port 43c. The second opposing surface 19f faces the other axial side (-Y) and faces the pump portion 40.

[0043] The second opposing surface 19f is provided with a second suction side groove 44b and a second discharge side groove 43b. The second suction side groove 44b and the second discharge side groove 43b are provided on a surface of the pump cover 19 facing the other axial side (-Y). The second suction side groove 44b and the second discharge side groove 43b are grooves that extend in the circumferential direction of the central axis J. The second suction side groove 44b and the second discharge side groove 43b are recessed toward one axial side (+Y). The second suction side groove 44b and the second discharge side groove 43b open to the other axial side (-Y). The second suction side groove 44b and the second discharge side groove 43b are provided at different circumferential positions. In this embodiment, the second suction side groove 44b and the second discharge side groove 43b are located on opposite sides of the central axis J.

[0044] The second suction side groove 44b and the first suction side groove 44a have substantially the same shape. The second suction side groove 44b overlaps with the first suction side groove 44a when viewed in the axial direction Y. Similarly, the second discharge side groove 43b and the first discharge side groove 43a have substantially the same shape. The second discharge side groove 43b overlaps with the first discharge side groove 43a when viewed in the axial direction Y. The second suction side groove 44b, the first suction side groove 44a, the second discharge side groove 43b, and the first discharge side groove 43a are part of the pump chamber 10B.

[0045] The suction portion 19a is cylindrical and protrudes toward one axial side (+Y) from the surface of the pump cover 19 facing that side. The suction port 44c is provided on the tip surface of the suction portion 19a. The suction port 44c is connected to the bottom surface of the second suction side groove portion 44b. The suction port 44c draws fluid from outside the electric pump 100. The suction port 44c allows the fluid to flow into the suction chamber A2 of the pump chamber 10B.

[0046] The discharge port 43c is provided on a surface of the pump cover 19 facing one axial side (+Y). The discharge port 43c is connected to the bottom surface of the second discharge groove portion 43b. The discharge port 43c discharges the compressed fluid to the outside of the electric pump 100. The discharge port 43c discharges the fluid from the compression chamber A1 of the pump chamber 10B.

[0047] (Pump section) The pump unit 40 is disposed on one axial side (+Y) of the motor unit 3. The pump unit 40 is connected to the end of the shaft 23 on one axial side (+Y). The pump unit 40 is driven by the power of the motor unit 3. The pump unit 40 draws in fluid such as oil from the outside, compresses the drawn fluid, and discharges it. In other words, the pump unit 40 pumps the fluid.

[0048] The pump section 40 of this embodiment is a trochoid pump. The pump section 40 includes an inner rotor 41 and an outer rotor 42. The outer rotor 42 is disposed radially outward of the inner rotor 41. The inner rotor 41 and the outer rotor 42 each have a trochoid tooth profile. The tooth profile of the inner rotor 41 and the tooth profile of the outer rotor 42 mesh at one circumferential point. The outer rotor 42 is held on the inner circumferential surface of the pump enclosure 11h. The outer rotor 42 surrounds the inner rotor 41 from the radially outer side over the entire circumferential circumference. The inner rotor 41 is connected to an end of the shaft 23 on one axial side (+Y). The inner rotor 41 rotates around the central axis J integrally with the shaft 23, radially inside the outer rotor 42. The outer rotor 42 rotates eccentrically around the central axis J while sliding along the inner circumferential surface of the pump enclosure 11h.

[0049] The internal space of the second suction side groove 44b and the internal space of the first suction side groove 44a are connected to the gap G between the inner rotor 41 and the outer rotor 42 from both sides in the axial direction Y. In the following description, the internal spaces of the second suction side groove 44b and the first suction side groove 44a, which are connected to each other as a single continuous space, are referred to as suction chamber A2. The suction chamber A2 is connected to the suction port 44c.

[0050] The internal space of the second discharge groove 43b and the internal space of the first discharge groove 43a are connected to the gap G between the inner rotor 41 and the outer rotor 42 from both sides in the axial direction Y. In the following description, the internal spaces of the second discharge groove 43b and the first discharge groove 43a, which are connected to each other as a continuous space, are referred to as compression chamber A1. Compression chamber A1 is connected to the discharge port 43c.

[0051] The suction port 44c, the suction chamber A2, the compression chamber A1, and the discharge port 43c function as part of the pump section 40. That is, the pump section 40 has the suction port 44c, the suction chamber A2, the compression chamber A1, and the discharge port 43c. The suction port 44c draws in fluid from the outside. The suction chamber A2 is connected to the suction port 44c. The compression chamber A1 pumps the fluid. The discharge port 43c is connected to the compression chamber A1 and discharges the fluid to the outside.

[0052] As the pump section 40 is driven, the gap G between the inner rotor 41 and the outer rotor 42 moves around the central axis J. As a result, the pressure in the suction chamber A2 decreases, and fluid flows into the suction chamber A2 and the gap G from the suction port 44c. As the gap G moves in the circumferential direction, the pump section 40 moves the fluid from the suction chamber A2 to the compression chamber A1. As a result, the pressure in the compression chamber A1 increases, and the fluid in the compression chamber A1 is discharged from the discharge port 43c.

[0053] (supply route and return route) The housing 10 is provided with a supply path F1 and a return path F2. The supply path F1 allows fluid to flow from the pump chamber 10B into the motor chamber 10A. This causes fluid to be stored in the pump chamber 10B to a certain height. The fluid in the pump chamber 10B circulates within the pump chamber 10B and cools the motor section 3 and the control section 70 arranged in the pump chamber 10B. The return path F2 returns the fluid from the motor chamber 10A to the pump chamber 10B. The fluid returned to the pump chamber 10B is discharged from the discharge port 43c together with other fluids.

[0054] In this embodiment, the first discharge groove 43a is connected to the communication groove 11s. That is, the communication groove 11s is connected to the compression chamber A1 at its radially outer end. The communication groove 11s is also connected to the end of the shaft support hole 11j on one axial side (+Y) of the shaft support hole 11j at its radially inner end. The shaft support hole 11j opens to the motor chamber 10A at its end on the other axial side (-Y). In this way, the communication groove 11s and the shaft support hole 11j connect the compression chamber A1 and the pump chamber 10B.

[0055] When the electric pump 100 is driven, the pressure of the fluid increases in the compression chamber A1. This increase in pressure causes the fluid to pass through the communicating groove 11s and the shaft support hole 11j and flow into the motor chamber 10A. In other words, the communicating groove 11s and the shaft support hole 11j function as a supply path F1 that moves the fluid from the pump chamber 10B to the motor chamber 10A.

[0056] The shaft 23 is disposed in the shaft support hole 11j. Therefore, a path connecting the pump chamber 10B and the motor chamber 10A inside the shaft support hole 11j is provided between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23. That is, in this embodiment, a portion of the supply path F1 is provided between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23.

[0057] In this embodiment, a communication hole 11k opens into the first suction groove portion 44a. The communication hole 11k is connected to the suction chamber A2 at one axial end (+Y side). The communication hole 11k is also connected to the motor chamber 10A at the other axial end (-Y side).

[0058] When the electric pump 100 is driven, the fluid pressure in the suction chamber A2 decreases, causing the fluid to be drawn in through the suction port 44c. At the same time, the fluid in the motor chamber 10A is drawn into the suction chamber A2 through the communication hole 11k. In other words, the communication hole 11k functions as a return path F2 that moves the fluid from the motor chamber 10A to the pump chamber 10B.

[0059] In this embodiment, the flow path cross-sectional area of ​​the return path F2 is larger than the flow path cross-sectional area of ​​the supply path F1. Here, the "flow path cross-sectional area" of the supply path F1 and the return path F2 is used as an index of the magnitude of the flow path resistance in the supply path F1 and the return path F2. The "flow path cross-sectional area" of the supply path F1 and the return path F2 represents the ease of fluid flow in the supply path F1 and the return path F2. The flow path cross-sectional area of ​​the supply path F1 represents the smallest flow path cross-sectional area in the entire length of the supply path F1. Furthermore, if the supply path F1 includes multiple branched paths, the flow path cross-sectional area of ​​the supply path F1 is the sum of the smallest flow path cross-sectional areas of the branched paths. Similarly, the flow path cross-sectional area of ​​the return path F2 represents the smallest flow path cross-sectional area in the entire length of the return path F2. Furthermore, if the return path F2 includes multiple branched paths, the flow path cross-sectional area of ​​the return path F2 is the sum of the smallest flow path cross-sectional areas of the branched paths.

[0060] In this embodiment, the supply path F1 has only one path. The supply path F1 in this embodiment has the smallest cross-sectional area inside the shaft support hole 11j. In this embodiment, the flow path cross-sectional area of ​​the supply path F1 is the area of ​​the gap between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23 in a cross section perpendicular to the axial direction Y.

[0061] In this embodiment, the return path F2 has only one path. The return path F2 in this embodiment has the smallest cross-sectional area inside the communication hole 11k. In this embodiment, the flow path cross-sectional area of ​​the return path F2 is the area of ​​a cross section perpendicular to the axial direction Y of the communication hole 11k.

[0062] During operation, the electric pump 100 of this embodiment sends fluid compressed in the compression chamber A1 to the motor chamber 10A via the supply path F1, and also draws fluid from the motor chamber 10A into the suction chamber A2 via the return path F2. If the flow rate of fluid sent to the motor chamber 10A via the supply path F1 is greater than the flow rate of fluid discharged from the motor chamber 10A via the return path F2, the pressure of the fluid in the motor chamber 10A increases. If the pressure of the fluid in the motor chamber 10A increases too much, the load on the connection between the fixing claw 13b and the locking groove 11c increases, which could cause the cover 13 and the motor housing 11 to become disengaged. Furthermore, if the pressure of the fluid in the motor chamber 10A increases too much, the housing 10 itself could be damaged. In addition, if the pressure of the fluid in the motor chamber 10A becomes too high, the force that the rotor 20 receives from the fluid in the motor chamber 10A becomes uneven in the circumferential direction, which may cause the shaft 23 to tilt and reduce the rotational efficiency of the shaft 23. For this reason, in the electric pump 100, it is preferable to suppress an increase in the pressure of the fluid in the motor chamber 10A.

[0063] In this embodiment, the cross-sectional area of ​​the return path F2 is larger than the cross-sectional area of ​​the supply path F1. Therefore, the return path F2 can have a smaller flow resistance than the supply path F1. This embodiment prevents the flow rate of fluid discharged from the motor chamber 10A through the return path F2 from becoming smaller than the flow rate of fluid sent to the motor chamber 10A through the supply path F1. As a result, an increase in fluid pressure in the motor chamber 10A can be prevented, and disconnection between the components constituting the housing 10 and damage to the housing 10 can be prevented. Furthermore, tilting of the shaft 23 due to an increase in fluid pressure in the motor chamber 10A can be prevented, thereby maintaining the driving efficiency of the electric pump 100.

[0064] In this embodiment, the supply path F1 is connected to the compression chamber A1 at the pump chamber 10B. Because the pressure of the fluid is increased in the compression chamber A1, the supply path F1 allows the fluid to move smoothly from the pump chamber 10B to the motor chamber 10A. Furthermore, the return path F2 is connected to the suction chamber A2 at the pump chamber 10B. Because the pressure of the fluid is reduced in the suction chamber A2 as the fluid is sucked in from the outside, the return path F2 allows the fluid to move smoothly from the motor chamber 10A to the pump chamber 10B.

[0065] In this embodiment, at least a portion of the return path F2 is provided in the communication hole 11k. The communication hole 11k is provided in the bottom wall portion 11d that separates the motor chamber 10A and the pump chamber 10B. According to this embodiment, the return path F2 can be easily formed by providing the communication hole 11k by machining the bottom wall portion 11d using a drill or the like. This reduces the manufacturing cost of the electric pump 100. Furthermore, by using the communication hole 11k as the return path F2, it is possible to adjust the flow path cross-sectional area of ​​the return path F2 with high precision by adjusting the hole diameter of the communication hole 11k. This makes it easy to adjust the flow path cross-sectional area of ​​the return path F2 to an appropriate size.

[0066] In this embodiment, the first opposing surface 11f is provided with a first suction-side groove 44a that constitutes at least a part of the inner wall of the suction chamber A2, and the communication hole 11k opens to the bottom surface of the first recess. According to this embodiment, the opening of the communication hole 11k in the pump chamber 10B can be prevented from being covered by the components of the pump section 40 (the inner rotor 41 and the outer rotor 42), thereby realizing smooth movement of fluid from the motor chamber 10A to the pump chamber 10B via the communication hole 11k.

[0067] In this embodiment, if the diameter of the communication hole 11k is made too large, the amount of intake from the motor chamber 10A to the suction chamber A2 may increase too much, which may reduce the amount of intake from the suction port 44c to the suction chamber A2. In other words, if the flow path cross-sectional area of ​​the return path F2 is made too large, the suction efficiency of the electric pump 100 may decrease.

[0068] As shown in FIG. 2 , in this embodiment, the outer edge 11ka of the opening of the first suction side groove portion 44a at the bottom surface 44aa of the communicating hole 11k is located more inward than the outer edge 44ab of the bottom surface 44aa when viewed from the axial direction Y. The first suction side groove portion 44a of this embodiment has an outer wall surface 44ac facing radially inward and an inner wall surface 44ad located radially inward of the outer wall surface 44ac and facing radially outward. The outer wall surface 44ac and the inner wall surface 44ad face each other radially. The outer wall surface 44ac and the inner wall surface 44ad each extend in an arc shape along the circumferential direction. In this embodiment, the entire outer edge 11ka of the opening of the communicating hole 11k is located radially inward of the outer wall surface 44ac when viewed from the axial direction Y. Furthermore, the entire outer edge 11ka of the opening of the communicating hole 11k is located radially outward of the inner wall surface 44ad when viewed from the axial direction Y.

[0069] According to this embodiment, the communication hole 11k can be made sufficiently small relative to the first suction groove portion 44a. This allows the amount of fluid flowing into the suction chamber A2 through the communication hole 11k to be made sufficiently small relative to the volume of the suction chamber A2. This prevents a decrease in the suction efficiency of the electric pump 100 caused by the flow of fluid from the motor chamber 10A to the pump chamber 10B through the return path F2.

[0070] As shown in FIG. 1, at least a portion of the supply path F1 in this embodiment is provided between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23. The inner circumferential surface of the shaft support hole 11j supports the outer circumferential surface of the shaft 23 while allowing it to slide along the inner circumferential surface. According to this embodiment, by providing the supply path F1 in the gap between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23, it is easy to make the flow path cross-sectional area of ​​the supply path F1 smaller than the flow path cross-sectional area of ​​the return path F2. According to this embodiment, it is easy to suppress an increase in pressure in the motor chamber 10A.

[0071] Furthermore, if the flow path cross-sectional area of ​​the supply path F1 is large, a large amount of fluid flows from the compression chamber A1 to the motor chamber 10A, and the pressure in the compression chamber A1 decreases, thereby reducing the amount of fluid discharged through the discharge port 43c. According to this embodiment, by providing the supply path F1 in the gap between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23, the flow path cross-sectional area of ​​the supply path F1 can be made sufficiently small, thereby improving the discharge efficiency of the electric pump 100.

[0072] Furthermore, according to this embodiment, by providing the supply path F1 in the gap between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23, the fluid lubricates the gap between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23. According to this embodiment, the frictional resistance between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23 can be reduced.

[0073] In this embodiment, the first opposing surface 11f is provided with a first discharge groove 43a that constitutes at least a portion of the inner wall of the compression chamber A1, and a communication groove 11s that connects the first discharge groove 43a to the inner circumferential surface of the shaft support hole 11j. Furthermore, at least a portion of the supply path F1 is provided within the communication groove 11s. According to this embodiment, the fluid whose pressure has been increased in the compression chamber A1 can be sent between the inner circumferential surface of the shaft support hole 11j and the outer circumferential surface of the shaft 23 via the communication groove 11s.

[0074] Fluid flows into the motor chamber 10A via the supply path F1 and flows out of the motor chamber 10A via the return path F2. In the motor chamber 10A, the fluid accumulates at least up to the height of the opening of the return path F2 in the motor chamber 10A. Therefore, by arranging components in the motor chamber 10A below the opening of the return path F2 in the motor chamber 10A, they can be cooled by the fluid that accumulates in the lower part of the motor chamber 10A.

[0075] In this embodiment, the control unit 70 is disposed in the motor chamber 10A. At least a portion of the control unit 70 is located below the opening of the return path F2 in the motor chamber 10A. According to this embodiment, at least a portion of the control unit 70 can be immersed in the fluid accumulated in the lower part of the motor chamber 10A, which makes it possible to effectively cool the control unit 70.

[0076] In this embodiment, the central axis J extends along a horizontal plane (XY plane). In this embodiment, the central axis J is positioned at the same height as the opening of the return path F2 in the motor chamber 10A. According to this embodiment, approximately half of the rotor 20 and the stator 30 can be immersed in the fluid accumulated at the bottom of the motor chamber 10A, making it possible to effectively cool the rotor 20 and the stator 30. Note that if the central axis J is positioned below the opening of the return path F2 in the motor chamber 10A, a wider area of ​​the rotor 20 and the stator 30 can be immersed in the fluid, further improving the cooling efficiency of the rotor 20 and the stator 30. In other words, the central axis J may be positioned at the same height as the opening of the return path F2 in the motor chamber 10A or below the opening of the return path F2 in the motor chamber 10A.

[0077] The electric pump 100 of this embodiment is housed in a recess 5a of the device 5 to which it is to be attached. The recess 5a is filled with a fluid. An opening 5b connected to a flow path in the device 5 to which it is to be attached is provided on the inner circumferential surface of the recess 5a. The discharge port 43c of the electric pump 100 discharges the fluid into the recess 5a. This increases the pressure in the recess 5a, and the fluid is pressure-fed into the flow path of the device 5 to which it is to be attached from the opening 5b.

[0078] FIG. 3 is a partial cross-sectional view of the electric pump 100 of this embodiment. The cylindrical portion 11a of the motor housing 11 has an end face 11t facing the other axial side (-Y). The cover portion 13 has a third opposing surface 13t that faces the end face 11t in the axial direction. A small gap K is provided between the end face 11t and the third opposing surface 13t. The dimension of the gap K in the axial direction Y is within the dimensional tolerance range of the motor housing 11 and the cover portion 13. The dimension of the gap K in the axial direction Y also varies depending on the circumferential position. The gap K connects the motor chamber 10A with the external space of the housing 10.

[0079] In this embodiment, a first groove 11g in which a first O-ring 2a is disposed is provided on the outer peripheral surface of the cylindrical portion 11a. Furthermore, a second groove 13g in which a second O-ring 2b is disposed is provided on the outer peripheral surface of the lid portion 13. The first O-ring 2a is located on one axial side (+Y) of the gap K, and the second O-ring 2b is located on the other axial side (-Y) of the gap K. The first O-ring 2a and the second O-ring 2b each extend circumferentially about the central axis J.

[0080] The first O-ring 2a is compressed between the bottom surface of the first groove 11g and the inner circumferential surface of the recess 5a, thereby restricting the passage of fluid between the outer circumferential surface of the cylindrical portion 11a and the inner circumferential surface of the recess 5a on one axial side (+Y) of the gap K.

[0081] In this embodiment, a first O-ring 2a is disposed on the outer peripheral surface of the cylindrical portion 11a, the first O-ring 2a being located on one axial side (+Y) of the gap K between the cylindrical portion 11a and the lid portion 13 and on the other axial side (-Y) of the discharge port 43c. The first O-ring 2a prevents the fluid discharged from the discharge port 43c into the recess 5a from reaching the gap K.

[0082] The interior of the recess 5a where the discharge port 43c opens is connected to the compression chamber A1, and the fluid pressure is increased similarly to that of the compression chamber A1. Therefore, if the first O-ring 2a is not provided, part of the fluid discharged from the discharge port 43c flows into the motor chamber 10A through the gap K. In other words, if the first O-ring 2a is not provided, the gap K functions as a supply path. Note that a case where the gap K functions as a supply path will be described later in Modification 3 (see FIG. 5).

[0083] According to this embodiment, the first O-ring 2a prevents fluid from flowing into the gap K from the discharge port 43c. This prevents the flow path cross-sectional area of ​​the supply path from increasing. As a result, the flow path cross-sectional area of ​​the supply path can be prevented from becoming larger than the flow path cross-sectional area of ​​the return path F2, thereby preventing an increase in pressure in the motor chamber 10A. Furthermore, according to this embodiment, the fluid discharged from the discharge port 43c can be easily pressure-fed into the flow path of the target device 5 through the opening 5b, thereby improving the discharge efficiency of the electric pump 100.

[0084] The second O-ring 2b is compressed between the bottom surface of the second groove portion 13g and the inner circumferential surface of the recessed portion 5a. As a result, the second O-ring 2b restricts the passage of fluid between the outer circumferential surface of the cylindrical portion 11a and the inner circumferential surface of the recessed portion 5a on the other axial side (-Y) of the gap K. According to this embodiment, it is possible to prevent moisture, dust, and the like that enter through the opening of the recessed portion 5a from entering the motor chamber 10A via the gap K. This improves the reliability of the electric pump 100.

[0085] <Modification> Next, modifications that can be adopted in the above-described embodiment will be described. In the following description of each modification, the same components as those in the already described embodiment or modification will be assigned the same reference numerals, and the description thereof will be omitted.

[0086] (Variation 1) 1 illustrates a return path F2a according to a first modified example that can be used in the above-described embodiment with a virtual line (two-dot chain line). The return path F2a according to this modified example is composed of a hole 111a provided in the cylindrical portion 11a and a groove 119a provided in the pump cover 19.

[0087] The hole 111a is provided at the end of the cylindrical portion 11a on one axial side (+Y). The hole 111a extends along the axial direction Y and opens into the inner circumferential surface of the pump enclosure 11h. The groove 119a is provided in the second opposing surface 19f of the pump cover 19. The groove 119a extends radially outward from the second suction-side groove 44b and opens into the outer circumferential surface of the pump cover 19. The radially outer opening of the groove 119a connects to the end of the hole 111a on one axial side (+Y). As a result, the hole 111a and the groove 119a connect the motor chamber 10A and the suction chamber A2 of the pump chamber 10B. The hole 111a and the groove 119a also function as a return path F2a that returns fluid from the motor chamber 10A to the pump chamber 10B.

[0088] Even when the return path F2a of this modified example is employed, by appropriately setting the flow path cross-sectional areas of the return path F2a and the supply path F1, it is possible to suppress an increase in pressure in the motor chamber 10A. The return path F2a of this modified example may be employed instead of the return path F2 of the above-described embodiment, or may be employed together with the return path F2 of the above-described embodiment. When multiple return paths F2, F2a are provided in the housing 10, the "flow path cross-sectional area of ​​the return path" to be compared with the flow path cross-sectional area of ​​the supply path F1 is the sum of the flow path cross-sectional areas of the respective return paths F2, F2a.

[0089] (Variation 2) 4 is a front view of the bottom wall 211d of Modification 2. As in the above-described embodiment, the first opposing surface 211f of the bottom wall 211d of this modification is provided with the first suction groove 44a, the first discharge groove 43a, and a communicating groove 11s. The bottom wall 211d is also provided with a communicating hole 211k that opens into the bottom surface of the first suction groove 44a.

[0090] In this modified example, an outer edge 211ka of the opening of the communicating hole 211k on the bottom surface 44aa of the first suction side groove portion 44a coincides with the outer edge 44ab of the bottom surface 44aa when viewed from the axial direction Y. In the present embodiment, a portion of the outer edge 211ka of the opening of the communicating hole 211k overlaps with the outer wall surface 44ac when viewed from the axial direction Y. Furthermore, a portion of the outer edge 211ka of the opening of the communicating hole 211k overlaps with the inner wall surface 44ad when viewed from the axial direction Y. Note that it is sufficient that a portion of the outer edge 211ka of the opening of the communicating hole 211k coincides with at least one portion of the outer edge 44ab of the bottom surface 44aa. Therefore, the outer edge 211ka of the opening of the communicating hole 211k may overlap, for example, with either the outer wall surface 44ac or the inner wall surface 44ad.

[0091] According to this modification, the communication hole 211k can be made larger than the first suction-side groove portion 44a. This increases the amount of fluid that flows into the suction chamber A2 via the communication hole 211k. As a result, it becomes easier to ensure that the flow path cross-sectional area of ​​the return path F2b is larger than the flow path cross-sectional area of ​​the supply path F1, thereby preventing an increase in fluid pressure in the motor chamber 10A.

[0092] (Variation 3) 5 is a partial cross-sectional view of an electric pump 300 according to a third modification. Similar to the above-described embodiment, the housing 310 according to this modification includes a motor housing 311 and a lid portion 13. An end surface 311t of a cylindrical portion 311a of the motor housing 311 and a third opposing surface 13t of the lid portion 13 face each other in the axial direction Y via a gap K. This modification differs from the above-described embodiment mainly in that no O-ring is provided on the outer circumferential surface of the cylindrical portion 311a between the gap K and the discharge port 43c in the axial direction.

[0093] According to this modification, at least a portion of the supply path F1a is provided in the gap K between the cylindrical portion 311a and the lid portion 13. The housing 310 of this modification is provided with the supply path F1a in addition to the supply path F1 (see FIG. 1) of the above-described embodiment. However, the housing 310 of this modification may not be provided with the supply path F1 of the above-described embodiment, and may be provided with only the supply path F1a of this modification shown in FIG. 5.

[0094] According to this modification, the flow path cross-sectional area of ​​the supply path F1 can be made larger than in the above-described embodiment, which allows a larger amount of fluid to be sent to the motor chamber 10A, thereby improving the cooling efficiency of each part of the motor chamber 10A (the motor unit 3 and the control unit 70).

[0095] In this modified example, a plurality of supply paths F1, F1a are provided in the housing 10. Therefore, the "cross-sectional area of ​​the supply paths" compared with the return path F2 is the sum of the cross-sectional areas of the supply paths F1, F1a.

[0096] In this modified example, the gap K that constitutes the supply path F1a is provided between surfaces that face each other in the axial direction Y, but the gap K may also be provided between surfaces that face each other in the radial direction.

[0097] The present invention is not limited to the above-described embodiment and its modifications, and other configurations and methods may be adopted within the scope of the technical concept of the present invention.

[0098] For example, the configurations of the supply path and return path in the above-described embodiment and its modified examples are merely examples, and are not limited to the above-described embodiment and its modified examples as long as they can transport fluid between the pump chamber and the motor chamber, respectively.

[0099] In the above-described embodiment, the cover and the motor housing are connected by the relationship between the fixing claw and the locking groove. However, the connection structure between the cover and the motor housing is not limited to the above-described embodiment.

[0100] The electric pump to which the present invention is applied is not particularly limited in its application. The type of fluid pumped by the electric pump is not particularly limited, and may be water, etc. The electric pump may be mounted on equipment other than a vehicle.

[0101] The present technology can be configured as follows. (1) An electric pump comprising: a motor section having a shaft rotatable about a central axis; a pump section connected to one axial end of the shaft and driven by the power of the motor section to pump a fluid; and a housing that accommodates the motor section and the pump section, wherein the housing is provided with a motor chamber in which the motor section is disposed, a pump chamber in which the pump section is disposed, a supply path that allows the fluid to flow from the pump chamber into the motor chamber, and a return path that returns the fluid from the motor chamber to the pump chamber, and the flow path cross-sectional area of ​​the return path is larger than the flow path cross-sectional area of ​​the supply path. (2) The electric pump described in (1), wherein the pump section has an intake port that draws in the fluid from the outside, an intake chamber connected to the intake port, a compression chamber that pressurizes the fluid, and an outlet that connects to the compression chamber and discharges the fluid to the outside, and the supply path is connected to the compression chamber and the return path is connected to the intake chamber. (3) The electric pump described in (2), wherein the housing has a bottom wall portion extending in a direction intersecting the axial direction and separating the motor chamber and the pump chamber, the bottom wall portion is provided with a communication hole connecting the motor chamber and the pump chamber, and at least a portion of the return path is provided in the communication hole. (4) An electric pump as described in (3), wherein a first recess that forms at least a part of the inner wall of the suction chamber is provided on a surface of the bottom wall facing one axial side, and the communication hole opens to the bottom surface of the first recess. (5) The electric pump according to (4), wherein an outer edge of an opening of the communication hole at the bottom surface of the first recess is positioned more inward than an outer edge of the bottom surface when viewed in the axial direction. (6) The electric pump according to (4), wherein at least a portion of an outer edge of the opening of the communication hole at the bottom surface of the first recess coincides with an outer edge of the bottom surface when viewed in the axial direction. (7) An electric pump according to any one of (2) to (6), wherein the housing has a bottom wall portion extending in a direction intersecting the axial direction to separate the motor chamber and the pump chamber, the bottom wall portion is provided with a shaft support hole extending in the axial direction to connect the motor chamber and the pump chamber, the shaft support hole rotatably supports the shaft on its inner circumferential surface, and at least a portion of the supply path is provided between the inner circumferential surface of the shaft support hole and the outer circumferential surface of the shaft. (8) An electric pump as described in (7), wherein a surface of the bottom wall portion facing one axial side is provided with a second recess that forms at least a part of the inner wall portion of the compression chamber and a groove portion that connects the second recess with the inner surface of the shaft support hole, and at least a part of the supply path is provided inside the groove portion. (9) An electric pump described in any one of (1) to (8), wherein the housing has a cylindrical portion surrounding the motor portion from the radial outside, and a lid portion connected to the other axial end of the cylindrical portion and covering the opening on the other axial side of the cylindrical portion, and a sealing member is arranged on the outer surface of the cylindrical portion, located on one axial side of the gap between the cylindrical portion and the lid portion and on the other axial side of the discharge port of the pump portion, and extending circumferentially along the central axis. (10) An electric pump described in any one of (1) to (8), wherein the housing has a cylindrical portion surrounding the motor portion from the radial outside and a lid portion connected to the other axial end of the cylindrical portion and covering the opening on the other axial side of the cylindrical portion, and at least a portion of the supply path is provided in the gap between the cylindrical portion and the lid portion. (11) An electric pump described in any one of (1) to (10), further comprising a control unit disposed in the motor chamber and controlling the motor unit, at least a portion of the control unit being located below the opening of the return path in the motor chamber. (12) An electric pump described in any one of (1) to (11), wherein the central axis extends along a horizontal plane and is located at the same height as the opening of the return path in the motor chamber or below the opening of the return path in the motor chamber. [Explanation of symbols]

[0102] 2a...first O-ring (sealing member), 3...motor portion, 5a...recess, 10, 310...housing, 10A...motor chamber, 10B...pump chamber, 11a, 311a...cylindrical portion, 11d, 211d...bottom wall portion, 11j...shaft support hole, 11k, 211k...communicating hole, 11ka, 44ab, 211ka...outer edge, 11s...communicating groove portion (groove portion), 13...lid portion, 23...shaft, 40 ...pump section, 43a...first discharge groove section (second recess), 43c...discharge port, 44a...first suction groove section (first recess), 44aa...bottom surface, 44c...suction port, 70...control section, 100, 300...electric pump, 119a...groove section, A1...compression chamber, A2...suction chamber, F1, F1a...supply path, F2, F2a, F2b...return path, G, K...gap, IC...control, J...central axis, Y...axial direction

Claims

1. a motor unit having a shaft rotatable about a central axis; a pump unit connected to one axial end of the shaft and driven by the power of the motor unit to pump fluid; a housing that accommodates the motor unit and the pump unit, The housing includes: a motor chamber in which the motor unit is disposed; a pump chamber in which the pump unit is disposed; a supply path for allowing the fluid to flow from the pump chamber to the motor chamber; a return path for returning the fluid from the motor chamber to the pump chamber; The return path has a cross-sectional area larger than the cross-sectional area of ​​the supply path. Electric pump.

2. The pump unit includes: an intake port for sucking the fluid from the outside; a suction chamber connected to the suction port; a compression chamber for compressing the fluid; a discharge port connected to the compression chamber and discharging the fluid to the outside, the supply path is connected to the compression chamber; The return path is connected to the suction chamber. The electric pump according to claim 1 .

3. the housing has a bottom wall portion extending in a direction intersecting the axial direction and separating the motor chamber and the pump chamber, a communication hole that connects the motor chamber and the pump chamber is provided in the bottom wall portion; At least a portion of the return path is provided in the communication hole. The electric pump according to claim 2.

4. a first recess that constitutes at least a part of an inner wall of the suction chamber is provided on a surface of the bottom wall that faces one axial side; the communication hole opens to a bottom surface of the first recess. The electric pump according to claim 3.

5. an outer edge of an opening of the communication hole at the bottom surface of the first recessed portion is positioned more inward than an outer edge of the bottom surface when viewed in the axial direction; The electric pump according to claim 4.

6. an outer edge of the opening of the communication hole at the bottom surface of the first recessed portion at least partially coincides with an outer edge of the bottom surface when viewed in the axial direction; The electric pump according to claim 4.

7. the housing has a bottom wall portion extending in a direction intersecting the axial direction and separating the motor chamber and the pump chamber, a shaft support hole extending in the axial direction and connecting the motor chamber and the pump chamber is provided in the bottom wall portion; the shaft support hole rotatably supports the shaft on an inner circumferential surface thereof, At least a portion of the supply path is provided between an inner circumferential surface of the shaft support hole and an outer circumferential surface of the shaft. The electric pump according to claim 2.

8. The surface of the bottom wall portion facing one axial side is a second recess that constitutes at least a part of the inner wall of the compression chamber; a groove portion connecting the second recess portion and an inner circumferential surface of the shaft support hole, At least a portion of the supply path is provided inside the groove portion. The electric pump according to claim 7.

9. The housing includes: a cylindrical portion that surrounds the motor portion from the radially outer side; a cover portion connected to the end portion on the other axial side of the cylindrical portion and covering the opening on the other axial side of the cylindrical portion, a seal member is disposed on an outer peripheral surface of the cylindrical portion, the seal member being located on one axial side of a gap between the cylindrical portion and the lid portion and on the other axial side of a discharge port of the pump portion, the seal member extending in a circumferential direction of the central axis; The electric pump according to claim 1 .

10. The housing includes: a cylindrical portion that surrounds the motor portion from the radially outer side; a cover portion connected to the end portion on the other axial side of the cylindrical portion and covering the opening on the other axial side of the cylindrical portion, At least a portion of the supply path is provided in a gap between the cylindrical portion and the lid portion. The electric pump according to claim 1 .

11. a control unit that is disposed in the motor chamber and controls the motor unit; At least a portion of the control unit is located below an opening of the return path in the motor chamber. The electric pump according to claim 1 .

12. The central axis extends along a horizontal plane and is located at the same height as an opening of the return path in the motor chamber or below the opening of the return path in the motor chamber. The electric pump according to claim 1 .

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