Electric pump

Abstract

An electric pump (100) comprises a pump part (10) and a motor part (20). The pump part (10) has a rotor (12). A drive shaft (1) has a shoulder part (4) formed between a large-diameter part (2) and a small-diameter part (3). The rotor (12) has a first insertion hole (12a), which fits with an outer peripheral surface of the large-diameter part (2) of the drive shaft (1), and a second insertion hole (12b) into which the small-diameter part (3) of the drive shaft (1) is inserted. A stop ring (70) for preventing the drive shaft (1) from coming off the rotor (12) is provided on the outer peripheral surface of the small-diameter part (3) of the drive shaft (1). Movement of the drive shaft (1) to one side in the axial direction relative to the rotor (12) is restricted as the shoulder part (4) of the drive shaft (1) comes into contact with a step part (12c) between the first insertion hole (12a) and the second insertion hole (12b), and movement of the drive shaft (1) to the other side in the axial direction relative to the rotor (12) is restricted as the stop ring (70) comes into contact with the rotor (12).

Description

electric pump

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

[0002] JP2010-112302A discloses an electric pump unit in which a pump, an electric motor for driving the pump, and a motor controller are assembled in a unit housing. A bearing is provided on the outer circumferential surface of the pump drive motor shaft driven by the motor.

[0003] In an electric pump unit such as that described in JP2010-112302A, radial movement of the pump drive motor shaft is restricted by a bearing. Furthermore, a snap ring or the like is provided to sandwich the bearing, thereby restricting axial movement of the pump drive motor shaft via the bearing. In such an electric pump unit, the number of parts increases because a bearing, a snap ring, or the like is provided to restrict movement of the pump drive motor shaft.

[0004] An object of the present invention is to reduce the number of parts in an electric pump.

[0005] According to one aspect of the present invention, there is provided an electric pump comprising: a pump section that discharges liquid; and a motor section that rotates a drive shaft to drive the pump section; wherein the pump section has a rotor through which the drive shaft is inserted and connected; the drive shaft has a large diameter section, a small diameter section that is smaller in diameter than the large diameter section, and a shoulder section that is formed between the large diameter section and the small diameter section; the rotor has a first insertion hole that mates with an outer circumferential surface of the large diameter section of the drive shaft; and a second insertion hole through which the small diameter section of the drive shaft is inserted and through which rotational torque is transmitted from the small diameter section; and a retaining member is provided on the outer circumferential surface of the small diameter section of the drive shaft to prevent the drive shaft from coming off the rotor; and the shoulder of the drive shaft contacts a step between the first insertion hole and the second insertion hole, thereby restricting movement of the drive shaft in one axial direction relative to the rotor, and the retaining member contacts the rotor, thereby restricting movement of the drive shaft in the other axial direction relative to the rotor.

[0006] Fig. 1 is a cross-sectional view of an electric pump according to an embodiment of the present invention, Fig. 2 is an enlarged view of a portion A shown in Fig. 1, and Fig. 3 is an enlarged view of a portion B shown in Fig. 1.

[0007] An electric pump 100 according to an embodiment of the present invention will be described below with reference to the drawings. The electric pump 100 is mounted on, for example, a vehicle and discharges a coolant (liquid) for cooling an electric motor mounted on the vehicle, or discharges oil (liquid) for lubricating gears mounted on the vehicle. The electric pump 100 may also be used as a fluid pressure supply source that discharges a working fluid (liquid) for driving equipment. The electric pump 100 may also be mounted on industrial machinery other than a vehicle.

[0008] As shown in Fig. 1, the electric pump 100 includes a pump unit 10 that discharges liquid, a motor unit 20 that rotates a drive shaft 1 to drive the pump unit 10, a control unit 30 that controls the motor unit 20, and a housing 40 that accommodates the pump unit 10, the motor unit 20, and the control unit 30. In the electric pump 100, the control unit 30, the motor unit 20, and the pump unit 10 are arranged in this order from the top in Fig. 1. Hereinafter, the axial direction of the drive shaft 1 will also be simply referred to as the "axial direction," and the radial direction of the drive shaft 1 will also be simply referred to as the "radial direction."

[0009] The pump unit 10 is an internal gear pump. The pump unit 10 has an inner rotor 12 as a rotor through which the drive shaft 1 is inserted and connected. An outer rotor 13 is provided on the outside of the inner rotor 12. The configuration of the drive shaft 1 and the configuration of the connection between the drive shaft 1 and the inner rotor 12 will be described later. The inner rotor 12 and the outer rotor 13 are housed in a housing 40 (specifically, a housing main body 41 described later), are provided eccentrically with respect to each other, and are covered by a pump cover 56 of the housing 40. Specifically, the inner rotor 12 is provided coaxially with the drive shaft 1 so that its center overlaps with the drive shaft 1, and the outer rotor 13 is provided so that its center is offset from the drive shaft 1. The inner rotor 12 has a plurality of external teeth (not shown) on its outer peripheral surface, and the outer rotor 13 has a plurality of internal teeth (not shown) on its inner peripheral surface that slide against the external teeth. The external teeth and the internal teeth are formed with different numbers of teeth, and a pump chamber 14 is defined by adjacent external teeth of the inner rotor 12 and internal teeth of the outer rotor 13. A plurality of pump chambers 14 are formed in the pump section 10.

[0010] When the drive shaft 1 rotates, the inner rotor 12 and the outer rotor 13 rotate while the external teeth of the inner rotor 12 slide against the internal teeth of the outer rotor 13. As the inner rotor 12 and the outer rotor 13 rotate, the volume of the pump chamber 14 repeatedly expands and contracts. In the expansion region (suction region) where the pump chamber 14 expands, liquid is sucked in through a suction port (not shown) formed in the pump cover 56, and in the contraction region (discharge region) where the pump chamber 14 contracts, liquid is discharged to the outside through a discharge port (not shown) formed in the pump cover 56.

[0011] The motor unit 20 includes an annular stator 21 and a motor rotor (not shown) disposed radially inside the stator 21. The stator 21 includes an annular stator core 22 disposed to surround the motor rotor and coil wires 23 wound around the stator core 22. The stator core 22 is formed with U-phase coils, V-phase coils, and W-phase coils corresponding to three-phase drive currents, and the ends of each coil wire 23 are connected to the control unit 30. The motor rotor includes a rotor core (not shown) coupled to the outer circumferential surface of the drive shaft 1 and rotating together with the drive shaft 1, and a plurality of permanent magnets (not shown) provided on the outer circumferential surface of the rotor core. In the motor unit 20, the motor rotor rotates about the drive shaft 1 due to the interaction between the magnetization state of the stator core 22 and the permanent magnets of the motor rotor. This drives the pump unit 10.

[0012] The control unit 30 controls the current supplied to the stator 21 to drive the motor unit 20. The control unit 30 includes electronic components 31 and a substrate 32 on which the electronic components 31 are mounted and to which the coil wires 23 of the motor unit 20 are connected. The electronic components 31 include, for example, a magnetic detection sensor such as a Hall element that can detect changes in magnetism that occur in response to the rotation of the drive shaft 1, and a calculation unit that calculates the rotation angle and rotation speed of the drive shaft 1 based on the detection value of the magnetic detection sensor. The control unit 30 controls the direction of the current flowing through the coil wires 23 of the stator 21 in accordance with the rotation angle of the drive shaft 1, and also controls the magnitude of the current supplied to the coil wires 23 so that the rotation speed of the drive shaft 1 matches a target rotation speed input from outside. A heat dissipation unit 33 that dissipates heat from the substrate 32 is provided between the substrate 32 and the housing 40.

[0013] The housing 40 has a housing main body 41 having an opening 42 , a cover 51 that covers the opening 42 , and a pump cover 56 that covers the pump section 10 .

[0014] The housing main body 41 has an insertion hole 43 through which the drive shaft 1 is inserted, an annular motor accommodating recess 44 in which the motor section 20 is accommodated, an oil seal accommodating recess 46 formed axially continuous with the insertion hole 43 and in which an oil seal 65 is accommodated, and a pump accommodating recess 47 in which the pump section 10 is accommodated.

[0015] The insertion hole 43 is formed to extend in the axial direction between the oil seal accommodating recess 46 and the pump accommodating recess 47. The motor accommodating recess 44 is formed to be continuous with the opening 42, and the stator core 22 of the motor section 20 is provided in contact with its inner circumferential surface 44a. The oil seal accommodating recess 46 is formed to have a larger diameter than the insertion hole 43. The pump accommodating recess 47 is formed with its center offset from the insertion hole 43, and accommodates the inner rotor 12 and outer rotor 13 of the pump section 10.

[0016] The cover 51 has a protrusion 51a that protrudes from the opposite side to the housing main body 41 (upward in FIG. 2 ). The protrusion 51a is hollow, and the circuit board 32 and heat dissipation unit 33 of the control unit 30 are housed in the hollow portion of the protrusion 51a. The circuit board 32 is electrically connected to the outside via a connector (not shown) provided on the housing main body 41. The cover 51 is fixed to the housing main body 41 with fastening members 81.

[0017] The pump cover 56 is provided to cover the pump accommodating recess 47. The pump cover 56 is fixed to the housing main body 41 by fastening members (not shown). The pump cover 56 is formed with a shaft accommodating portion 56a that accommodates the tip end 1a of the drive shaft 1.

[0018] Next, the configuration of the drive shaft 1 and the configuration of the connection between the drive shaft 1 and the inner rotor 12 will be described in detail.

[0019] 1 and 2, the drive shaft 1 has a large diameter portion 2, a small diameter portion 3 formed with a diameter smaller than the large diameter portion 2, and a shoulder portion 4 (see FIG. 2) formed between the large diameter portion 2 and the small diameter portion 3. The drive shaft 1 has the small diameter portion 3 formed on the tip end 1a side (lower side in FIG. 1) and the large diameter portion 2 formed on the base end 1b side (upper side in FIG. 1). The tip end 1a is accommodated in a shaft accommodating portion 56a of the pump cover 56 so as not to come into contact with the pump cover 56. A magnet 67 is provided on the base end 1b so as not to come into contact with the electronic components 31 and the circuit board 32 of the control unit 30. The control unit 30 detects changes in magnetism caused by the magnet 67 and calculates the rotation angle and rotation speed of the drive shaft 1.

[0020] The large diameter portion 2 is formed over the motor accommodating recess 44, the oil seal accommodating recess 46, the insertion hole 43, and the pump accommodating recess 47 of the housing main body 41 of the housing 40. The large diameter portion 2 is formed in a cylindrical shape with a uniform outer diameter along the axial direction, and has no notches or the like. An oil seal 65 and multiple bushings 60 are provided on the outer peripheral surface of the large diameter portion 2. The multiple bushings 60 are provided between the inner peripheral surface of the insertion hole 43 and the outer peripheral surface of the large diameter portion 2, and support the drive shaft 1 rotatably relative to the housing main body 41. It is noted that only one bushing 60 may be provided.

[0021] In this embodiment, the small diameter portion 3 is formed in a so-called D-cut shape. Specifically, the small diameter portion 3 has a flat portion 3a formed by cutting out a portion of the outer circumferential surface in the axial direction. The flat portion 3a extends axially from the tip end 1a to the large diameter portion 2, and two flat portions 3a are formed parallel to each other. In other words, the small diameter portion 3 has a two-face width. As described below, the flat portions 3a contact the inner rotor 12 and rotate, thereby transmitting the rotational torque of the drive shaft 1 to the inner rotor 12. Shoulders 4 (see FIG. 2) are formed between the large diameter portion 2 and the two flat portions 3a. The shoulders 4 are formed to extend radially between the large diameter portion 2 and the two flat portions 3a.

[0022] As shown in FIGS. 1 and 3 , a retaining ring 70 is provided on the outer peripheral surface of the small diameter portion 3 as a retaining member that prevents the drive shaft 1 from slipping out of the inner rotor 12. Specifically, an annular receiving hole 3b (see FIG. 3 ) is formed on the outer peripheral surface of the small diameter portion 3 of the drive shaft 1, and a portion of the retaining ring 70 is received in the receiving hole 3b. A portion of the retaining ring 70 is exposed radially from the receiving hole 3b. The retaining ring 70 is formed in an annular shape, and when not attached to the receiving hole 3b, its inner diameter is smaller than the innermost diameter of the receiving hole 3b or is approximately the same as the innermost diameter of the receiving hole 3b. The receiving hole 3b is formed with an arc-shaped cross section that conforms to the shape of the retaining ring 70. When attaching the retaining ring 70 to the drive shaft 1, the inner rotor 12 is first attached to the drive shaft 1, and then force is applied from the inside of the retaining ring 70 to elastically deform it so that its diameter expands, allowing it to move along the outer peripheral surface of the small diameter portion 3. Then, by loosening the force applied to the retaining ring 70 on the receiving hole 3b, the retaining ring 70 is reduced in diameter and received in the receiving hole 3b. The retaining ring 70 may be formed in a C-shape or an E-shape.

[0023] The retaining ring 70 is capable of contacting the inner rotor 12 (specifically, the pressing portion 12d, which will be described later), and contact of the retaining ring 70 with the inner rotor 12 restricts axial movement of the drive shaft 1 relative to the inner rotor 12 (upward in FIG. 1-3 ). This prevents the drive shaft 1 from coming off the inner rotor 12. The retaining ring 70 is positioned so that, even when it comes into contact with the inner rotor 12, the magnet 67 provided on the drive shaft 1 will not come into contact with the electronic components 31 or the circuit board 32 of the control unit 30.

[0024] 2 and 3, the inner rotor 12 has a first insertion hole 12a (see FIG. 2) that fits onto the outer peripheral surface of the large diameter portion 2 of the drive shaft 1, a second insertion hole 12b (see FIG. 2) through which the small diameter portion 3 of the drive shaft 1 is inserted, and a pressing portion 12d (see FIG. 3) that can come into contact with the retaining ring 70. The first insertion hole 12a, the second insertion hole 12b, and the pressing portion 12d are formed continuously and lined up in this order from the top side in FIG.

[0025] As shown in Figure 2, the first insertion hole 12a is formed at one axial end of the inner rotor 12 (upper side in Figures 1 to 3). The inner diameter of the first insertion hole 12a is larger than the inner diameter of the second insertion hole 12b and is approximately the same diameter as the large diameter portion 2 of the drive shaft 1. Therefore, when the drive shaft 1 is inserted into the inner rotor 12, the outer peripheral surface of the large diameter portion 2 of the drive shaft 1 fits into the inner peripheral surface of the first insertion hole 12a of the inner rotor 12. This allows the drive shaft 1 and the inner rotor 12 to be coaxially arranged, and restricts radial movement of the drive shaft 1 relative to the inner rotor 12.

[0026] The second insertion hole 12b is formed between the first insertion hole 12a and the pressing portion 12d. The second insertion hole 12b is formed to correspond to the shape of the small diameter portion 3 of the drive shaft 1. Specifically, the second insertion hole 12b has a flat portion 12e that comes into surface contact with the flat portion 3a of the small diameter portion 3. When the drive shaft 1 rotates, rotational torque is transmitted from the flat portion 3a of the drive shaft 1 to the flat portion 12e of the inner rotor 12, causing the inner rotor 12 to rotate.

[0027] A stepped portion 12c is formed between the first insertion hole 12a and the second insertion hole 12b. The stepped portion 12c extends radially. The stepped portion 12c is formed axially opposite the shoulder portion 4 of the drive shaft 1 and is capable of contacting the shoulder portion 4. The shoulder portion 4 contacts the stepped portion 12c, thereby restricting the movement of the drive shaft 1 in the axial direction (downward in FIGS. 1 to 3 ) relative to the inner rotor 12. The shoulder portion 4 of the drive shaft 1 is positioned so that the tip end 1a of the drive shaft 1 does not contact the pump cover 56 even when it contacts the stepped portion 12c of the inner rotor 12.

[0028] As shown in FIG. 3 , the pressing portion 12d is annularly formed at the other axial end (lower side in FIGS. 1-3 ) of the inner rotor 12. The pressing portion 12d is tapered relative to the axial direction. Specifically, the pressing portion 12d is formed so that its diameter gradually increases with increasing distance from the second insertion hole 12b. The pressing portion 12d can contact a retaining ring 70. When the retaining ring 70 contacts the tapered pressing portion 12d, the axial movement of the drive shaft 1 relative to the inner rotor 12 (upper side in FIGS. 1-3 ) is restricted. Furthermore, when the retaining ring 70 contacts the pressing portion 12d, a reaction force F of the force of the retaining ring 70 pressing the pressing portion 12d acts from the point P of contact between the two toward a perpendicular direction to the pressing portion 12d (arrow F in FIG. 3 ). The extension of the reaction force F intersects with the accommodating hole 3b. In other words, the accommodating hole 3b is provided at a position where an extension line of the reaction force F extending from the point P intersects. Therefore, the retaining ring 70 is pressed against the accommodating hole 3b of the drive shaft 1. This makes it difficult for the retaining ring 70 to fall out of the accommodating hole 3b. Furthermore, because the retaining ring 70 is difficult to fall out of the accommodating hole 3b, the accommodating hole 3b can be formed shallower than in a configuration without the pressing portion 12d, and the cross-sectional loss of the small diameter portion 3 is reduced.

[0029] In this way, in the electric pump 100, the outer peripheral surface of the large diameter portion 2 of the drive shaft 1 is fitted into the inner peripheral surface of the first insertion hole 12a of the inner rotor 12, thereby restricting radial movement of the drive shaft 1 relative to the inner rotor 12, and the shoulder portion 4 of the drive shaft 1 and the retaining ring 70 provided on the drive shaft 1 come into contact with the inner rotor 12, thereby restricting axial movement of the drive shaft 1 relative to the inner rotor 12. In other words, radial and axial movement of the drive shaft 1 relative to the inner rotor 12 can be restricted without providing a bearing or a snap ring, washer, or the like that restricts axial movement of the bearing. Therefore, radial and axial movement of the drive shaft 1 relative to the inner rotor 12 can be restricted with a small number of parts.

[0030] Furthermore, the electric pump 100 does not require bearings, which are relatively expensive components, thereby reducing the manufacturing costs of the electric pump 100. Furthermore, the electric pump 100 can be assembled simply by fitting the outer peripheral surface of the large diameter portion 2 of the drive shaft 1 with the inner peripheral surface of the first insertion hole 12a of the inner rotor 12 and providing a retaining ring 70, which improves the ease of assembly of the electric pump 100 compared to a configuration in which movement of the drive shaft 1 is restricted by bearings, snap rings, washers, etc.

[0031] As shown in FIGS. 1 and 2 , in the electric pump 100, when the retaining ring 70 is in contact with the inner rotor 12, a gap S (see FIG. 2 ) is formed between the shoulder 4 of the drive shaft 1 and the step 12c of the inner rotor 12. If the gap S were not formed, a force from the drive shaft 1 pressing the inner rotor 12 toward the pump cover 56 could occur due to manufacturing errors in the drive shaft 1, etc. For example, the drive shaft 1 could receive force from a motor rotor (not shown) of the motor unit 20, which would press the inner rotor 12 toward the pump cover 56. This could result in the inner rotor 12 seizing up or the like. However, in the electric pump 100 of this embodiment, the gap S is formed, and this gap S can absorb manufacturing errors in the drive shaft 1, etc. This prevents the inner rotor 12 from seizing up or the like.

[0032] Furthermore, in the electric pump 100, a part of the outer circumferential surface of the large diameter portion 2 of the drive shaft 1 is cut away to form the flat portion 3a of the small diameter portion 3, which makes it easier to process the drive shaft 1.

[0033] According to the present embodiment described above, the following effects are achieved.

[0034] In the electric pump 100, the outer peripheral surface of the large diameter portion 2 of the drive shaft 1 fits into the inner peripheral surface of the first insertion hole 12a of the inner rotor 12, restricting radial movement of the drive shaft 1 relative to the inner rotor 12, and the shoulder portion 4 of the drive shaft 1 and a retaining ring 70 provided on the drive shaft 1 come into contact with the inner rotor 12, restricting axial movement of the drive shaft 1 relative to the inner rotor 12. Thus, radial and axial movement of the drive shaft 1 relative to the inner rotor 12 can be restricted with a small number of parts.

[0035] Next, modified examples of this embodiment will be described. The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above embodiment, or to combine the configurations described in the different modified examples below.

[0036] <Modification 1> In the above embodiment, the drive shaft 1 has the small diameter portion 3 formed on the tip end 1a side and the large diameter portion 2 formed on the base end 1b side. Alternatively, the drive shaft 1 may have the large diameter portion 2 formed on the tip end 1a side and the small diameter portion 3 formed on the base end 1b side. In this configuration, the inner rotor 12 is formed upside down from the shape shown in FIG. 1 . The stop ring 70 provided on the outer peripheral surface of the small diameter portion 3 contacts the pressing portion 12d of the inner rotor 12, thereby restricting axial movement of the drive shaft 1 in one direction relative to the inner rotor 12, and the shoulder portion 4 contacts the step portion 12c of the inner rotor 12, thereby restricting axial movement of the drive shaft 1 in the other direction relative to the inner rotor 12. This configuration also provides the same effects as the above embodiment.

[0037] <Modification 2> In the above embodiment, when the retaining ring 70 is in contact with the inner rotor 12, a gap S is formed between the shoulder portion 4 of the drive shaft 1 and the step portion 12c of the inner rotor 12, and the gap S can absorb manufacturing errors of the drive shaft 1, etc. However, although it is preferable that the gap S is formed, it is not an essential component of the electric pump 100.

[0038] <Modification 3> In the above embodiment, the accommodating hole 3b is formed with an arc-shaped cross section that conforms to the shape of the retaining ring 70. However, the shape of the accommodating hole 3b is not limited to this, and may be, for example, rectangular in cross section. Also, in the above embodiment, the pressing portion 12d of the inner rotor 12 is formed with a tapered shape, and the reaction force F presses the retaining ring 70 against the accommodating hole 3b. However, the pressing portion 12d does not have to be formed with a tapered shape as long as the reaction force F can press the retaining ring 70 against the accommodating hole 3b. Furthermore ... if there is no risk of the retaining ring 70 falling off, for example, the pressing portion 12d does not have to be formed.

[0039] <Modification 4> In the above embodiment, the shoulder portion 4 is formed to extend linearly in the radial direction. However, the shape of the shoulder portion 4 is not limited to the above as long as it can restrict axial movement of the drive shaft 1 relative to the inner rotor 12 by axially contacting the step portion 12c of the inner rotor 12. For example, the shoulder portion 4 may be formed to have a curved surface or a tapered shape.

[0040] <Modification 5> In the above embodiment, the small diameter portion 3 of the drive shaft 1 is formed in a so-called D-cut shape. Specifically, the small diameter portion 3 has two flat portions 3a formed by cutting out part of the outer circumferential surface of the large diameter portion 2. However, the shape of the small diameter portion 3 is not limited to this as long as it can transmit the rotational torque of the drive shaft 1 to the inner rotor 12. The small diameter portion 3 may be configured to have only one flat portion 3a. Furthermore, the small diameter portion 3 and the inner rotor 12 may be spline-coupled.

[0041] In the above embodiment, the pump section 10 is an internal gear pump in which the inner rotor 12 has a plurality of external teeth on its outer peripheral surface, and the outer rotor 13 has a plurality of internal teeth on its inner peripheral surface that are in sliding contact with the external teeth. However, the configuration of the pump section 10 is not limited to this, and the pump section 10 may be, for example, a vane pump having a cam ring or a plurality of vanes.

[0042] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0043] The electric pump 100 includes a pump section 10 that discharges a liquid, and a motor section 20 that drives the pump section 10 by rotating a drive shaft 1. The pump section 10 has an inner rotor 12 as a rotor into which the drive shaft 1 is inserted and connected. The drive shaft 1 has a large diameter section 2, a small diameter section 3 that is formed with a diameter smaller than that of the large diameter section 2, and a shoulder section 4 that is formed between the large diameter section 2 and the small diameter section 3. The inner rotor 12 has a first insertion hole 12a that fits with the outer circumferential surface of the large diameter section 2 of the drive shaft 1, and a second insertion hole 12b that fits with the outer circumferential surface of the small diameter section 3 of the drive shaft 1. and a second insertion hole 12b through which rotational torque is transmitted from the first insertion hole 12a to the second insertion hole 12b. A retaining ring 70 is provided on the outer peripheral surface of the small diameter portion 3 of the drive shaft 1 as a retaining member that prevents the drive shaft 1 from slipping out of the inner rotor 12. The shoulder 4 of the drive shaft 1 comes into contact with a step 12c between the first insertion hole 12a and the second insertion hole 12b, thereby restricting movement of the drive shaft 1 in one axial direction relative to the inner rotor 12, and the retaining ring 70 comes into contact with the inner rotor 12, thereby restricting movement of the drive shaft 1 in the other axial direction relative to the inner rotor 12.

[0044] In this configuration, the outer peripheral surface of the large diameter portion 2 of the drive shaft 1 is fitted into the inner peripheral surface of the first insertion hole 12a of the inner rotor 12, thereby restricting radial movement of the drive shaft 1 relative to the inner rotor 12, and the shoulder portion 4 of the drive shaft 1 and the retaining ring 70 provided on the drive shaft 1 come into contact with the inner rotor 12, thereby restricting axial movement of the drive shaft 1 relative to the inner rotor 12. Therefore, radial and axial movement of the drive shaft 1 relative to the inner rotor 12 can be restricted with a small number of parts.

[0045] Furthermore, in the electric pump 100 , when the retaining ring 70 is in contact with the inner rotor 12 , a gap S is formed between the shoulder portion 4 of the drive shaft 1 and the step portion 12 c of the inner rotor 12 .

[0046] In this configuration, the gap S between the shoulder 4 of the drive shaft 1 and the step 12c of the inner rotor 12 can absorb manufacturing errors of the drive shaft 1 and the like.

[0047] In addition, in the electric pump 100, a ring-shaped accommodating hole 3b that accommodates a portion of the retaining ring 70 is formed in the small diameter portion 3 of the drive shaft 1, and the inner rotor 12 further has a pressing portion 12d that presses the retaining ring 70 against the accommodating hole 3b by a reaction force when the retaining ring 70 comes into contact with the inner rotor 12.

[0048] In the electric pump 100, the pressing portion 12d of the inner rotor 12 is formed in a tapered shape that is inclined with respect to the axial direction.

[0049] In these configurations, the pressing portion 12d of the inner rotor 12 makes it difficult for the retaining ring 70 to fall out of the receiving hole 3b.

[0050] In addition, in the electric pump 100, the small diameter portion 3 of the drive shaft 1 has a flat portion 3a formed by cutting out a portion of the outer circumferential surface in the axial direction, and the shoulder portion 4 of the drive shaft 1 is formed between the large diameter portion 2 and the flat portion 3a.

[0051] This configuration makes it easier to process the drive shaft 1.

[0052] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0053] This application claims priority based on Japanese Patent Application No. 2024-44542, filed with the Japan Patent Office on March 21, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An electric pump comprising: a pump section that discharges liquid; and a motor section that rotates a drive shaft to drive the pump section, wherein the pump section has a rotor through which the drive shaft is inserted and connected, the drive shaft having: a large diameter section; a small diameter section that is smaller in diameter than the large diameter section; and a shoulder section that is formed between the large diameter section and the small diameter section, the rotor having: a first insertion hole that mates with the outer circumferential surface of the large diameter section of the drive shaft; and a second insertion hole through which the small diameter section of the drive shaft is inserted and through which rotational torque is transmitted from the small diameter section, and a retaining member that prevents the drive shaft from coming off the rotor is provided on the outer circumferential surface of the small diameter section of the drive shaft, wherein the shoulder of the drive shaft comes into contact with a step between the first insertion hole and the second insertion hole, thereby restricting movement of the drive shaft in one axial direction relative to the rotor, and wherein the retaining member comes into contact with the rotor, thereby restricting movement of the drive shaft in the other axial direction relative to the rotor.

2. An electric pump according to claim 1, wherein when the retaining member is in contact with the rotor, a gap is formed between the shoulder of the drive shaft and the step of the rotor.

3. An electric pump as claimed in claim 1, wherein the small diameter portion of the drive shaft is formed with an annular accommodating hole for accommodating a part of the retaining member, and the rotor further has a pressing portion which, when the retaining member comes into contact with the rotor, presses the retaining member against the accommodating hole by reaction force.

4. An electric pump according to claim 3, wherein the pressing portion of the rotor is formed in a tapered shape inclined relative to the axial direction.

5. An electric pump according to claim 1, wherein the small diameter portion of the drive shaft has a flat portion formed by cutting out a portion of the outer circumferential surface in the axial direction, and the shoulder portion of the drive shaft is formed between the large diameter portion and the flat portion.

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