Electric pump

Abstract

To provide an electric pump that can improve the torque of a motor, and restrain a foreign body from being caught in a gap between a rotor and a stator at the same time.SOLUTION: An electric motor 1 (1A-1C) comprises: a supporting shaft 10; a rotor 20 including an impeller 22 and a magnet 26, and supported by the supporting shaft 10 on the outside in the radial direction of the supporting shaft 10; a stator 40 including a stator core 42 arranged across a magnetic gap G between itself and the magnet 26, and opposed to the rotor 20 across a gap 48 in the formation range of the magnet gap G in a non-contact manner; and a return flow passage 50 provided so as to pass at least on the outside in the radial direction of the rotor 20 and the stator 40 in order to establish communication between a discharge port 22B of the impeller 22 and a suction port 22A of the impeller 22, and return fluid passed through the impeller 22, to the suction port 22A of the impeller 22. The return flow passage 50 includes a bypass passage 60 bypassing the gap 48 separating the rotor 20 and the stator 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, an electric pump has been known in which an impeller for pressurizing a fluid and a motor for rotating the impeller are disposed in the same casing. In this type of electric pump, a rotor including an impeller and a magnet and a stator including a stator core arranged with a magnetic gap between them are opposed to each other across a gap that communicates with the pump chamber.

[0003] For example, Patent Document 1 describes an electric pump that includes a shaft member fixed to a casing, a bearing portion inserted on the outside of the shaft member, and a rotor to which an impeller is fixed. The electric pump described in Patent Document 1 circulates a portion of the fluid that has passed through the impeller within a casing, for example, to lubricate the bearings or cool the motor. Specifically, a discharge passage is provided between the bearings and the rotor, and a portion of the fluid that has passed through the impeller flows into this discharge passage via the gap between the rotor and the stator, and is then returned to the impeller intake port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-23635 Summary of the Invention [Problem to be solved by the invention]

[0005] In general, from the viewpoint of improving the torque of the motor, it is desirable that the magnetic gap between the magnet and the stator core is narrow. However, when circulating a portion of the fluid that has passed through the impeller within a casing, as in the electric pump described in Patent Document 1, there is a risk that foreign matter accompanying the circulating fluid will become caught in the gap between the rotor and the stator. For this reason, it is necessary to ensure a sufficient gap between the rotor and the stator, making it difficult to narrow the magnetic gap between the magnet and the stator core.

[0006] In view of the above circumstances, at least some embodiments of the present invention aim to provide an electric pump that can simultaneously improve motor torque and prevent foreign matter from getting caught in the gap between the rotor and the stator. [Means for solving the problem]

[0007] [1] At least some embodiments of the electric pump of the present invention include: A support shaft; a rotor including an impeller and a magnet and supported by the support shaft on the radially outer side of the support shaft; a stator including a stator core disposed with a magnetic gap between it and the magnet, the stator facing the rotor without contact with the rotor across an air gap within the range where the magnetic gap is formed; a return flow path that communicates the discharge port of the impeller with the suction port of the impeller and that passes through at least the radially outer side of the rotor and the stator so as to return the fluid that has passed through the impeller to the suction port of the impeller; Equipped with The return flow path includes a bypass passage that bypasses the air gap separating the rotor and the stator.

[0008] [2] In some embodiments, in the configuration of [1] above, The electric pump includes a casing that houses a rotor, a stator, and a support shaft. The stator is A stator coil; a molding material that covers the stator core and the stator coil; Including, The return passage includes an annular passage formed between the outer peripheral surface of the rotor or molding material and the inner peripheral surface of the casing.

[0009] [3] In some embodiments, in the configuration of [2] above, The bypass road is a first flow passage connected to the downstream end of the annular flow passage and passing through a radial position range occupied by the magnet and the stator core at an axial position on the opposite side of the impeller with the magnet and the stator core in between; Includes.

[0010] [4] In some embodiments, in the configuration of [3] above, The bypass road is a second flow path connected to a downstream end of the first flow path, the second flow path being radially inward of the magnet and the stator core and passing through an axial position range occupied by the magnet and the stator core; Includes.

[0011] [5] In some embodiments, in any of the configurations [1] to [4] above, The electric pump includes a bearing for rotatably supporting the rotor on the support shaft, The bypass path bypasses both the bearing clearance and the air gap of the bearing.

[0012] [6] In one embodiment, in the configuration of [5] above, The bypass passage includes an internal flow passage in the support shaft having a hollow structure.

[0013] [7] In some embodiments, in any of the configurations [1] to [6] above, The cross-sectional area of ​​the bypass passage is larger than the cross-sectional area of ​​the gap.

[0014] [8] In some embodiments, in any of the configurations [1] to [7] above, The electric pump includes a casing that houses a rotor, a stator, and a support shaft. The rotor is disposed radially outside the stator and facing the stator across a gap, the return flow passage includes an annular flow passage formed between an outer peripheral surface of the rotor and an inner peripheral surface of the casing; The bypass passage is configured to bypass the gap downstream of the annular flow passage.

[0015] [9] In some embodiments, in any of the configurations [1] to [7] above, The electric pump includes a casing that houses a rotor, a stator, and a support shaft. The stator is A stator coil; a molding material that covers the stator core and the stator coil; Including, The rotor is disposed radially inside the stator and facing the stator across a gap, At least a portion of the bypass passage is formed between the outer peripheral surface of the molding material and the inner peripheral surface of the casing.

[0016]

[10] In some embodiments, in any of the configurations [1] to [7] above, A casing that houses the rotor, stator, and support shaft Equipped with The stator is A stator coil; a molding material that covers the stator core and the stator coil; Including, The rotor is disposed opposite to the stator, which is located on the opposite side in the axial direction, with an air gap therebetween. At least a portion of the bypass passage is formed between the outer peripheral surface of the rotor and the outer peripheral surface of the molding material and the inner peripheral surface of the casing.

[0017]

[11] In some embodiments, in any one of the configurations [1] to

[10] above, the electric pump is a circuit board on which electronic components for controlling the electric pump are mounted; a partition wall separating a pump motor chamber in which the stator and the rotor are housed from a substrate chamber in which the substrate is housed; Equipped with The return flow path includes a heat dissipation flow path formed between the rotor and the partition wall.

[0018]

[12] In some embodiments, in any of the configurations [1] to

[11] above, The partition wall is an annular portion having an opening communicating between the pump motor chamber and the base plate chamber; a cover member provided to close the opening of the annular portion and having a higher thermal conductivity than the annular portion; Includes:

[0019]

[13] In some embodiments, in the configuration of

[12] above, The cover member has a plurality of heat dissipating protrusions formed on a surface facing the heat dissipation flow path. [Effects of the Invention]

[0020] According to at least some embodiments of the present invention, by providing a bypass path that bypasses the gap in the magnetic gap forming range between the rotor and the stator, the flow rate of fluid passing through the gap can be reduced, and the risk of foreign matter entering the gap can be reduced. Therefore, it is possible to narrow the magnetic gap and improve the torque of the motor while suppressing foreign matter from getting caught in the gap. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is an axial cross-sectional view showing a schematic configuration of an electric pump according to an embodiment. [Figure 2] FIG. 10 is an axial cross-sectional view showing a schematic configuration of an electric pump according to another embodiment. [Figure 3] FIG. 10 is an axial cross-sectional view showing a schematic configuration of an electric pump according to yet another embodiment. [Figure 4] FIG. 2 is a diagram schematically illustrating a first flow path according to one embodiment, and is a radial cross-sectional view of an electric pump including the first flow path. [Figure 5] 1 is an axial cross-sectional view showing a specific structural example of an electric pump according to an embodiment; [Figure 6]FIG. 10 is an axial cross-sectional view showing a specific structural example of an electric pump according to another embodiment. [Figure 7] FIG. 7 is a partially sectional perspective view showing the internal structure of the electric pump shown in FIG. 6. [Figure 8] FIG. 10 is an axial cross-sectional view showing a specific structural example of an electric pump according to yet another embodiment. [Figure 9] FIG. 10 is an axial cross-sectional view showing a specific structural example of an electric pump according to yet another embodiment. [Figure 10] FIG. 10 is an axial cross-sectional view showing a specific structural example of an electric pump according to yet another embodiment. [Figure 11] FIG. 2 is a perspective view showing a cross section of the electric pump according to the embodiment, taken at an axial position passing through a radial flow passage and a central hole. [Figure 12A] FIG. 2 is a perspective view showing a cover member of the electric pump according to the embodiment; [Figure 12B] FIG. 10 is a perspective view showing a cover member of an electric pump according to another embodiment. [Figure 12C] FIG. 10 is a perspective view showing a cover member of an electric pump according to yet another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0023] Fig. 1 is an axial cross-sectional view showing a schematic configuration of an electric pump 1A according to one embodiment. Fig. 2 is an axial cross-sectional view showing a schematic configuration of an electric pump 1B according to another embodiment. Fig. 3 is an axial cross-sectional view showing a schematic configuration of an electric pump 1C according to yet another embodiment. Hereinafter, when referring to an electric pump according to some embodiments of the present invention including the electric pumps 1A to 1C, the electric pump will be referred to as the electric pump 1 (1A to 1C).

[0024] As shown in FIGS. 1 to 3, in some embodiments, the electric pump 1 (1A to 1C) includes a casing 2, and a motor section 6 and a pump section 8 disposed within the casing 2. The casing 2 has a fluid inlet 3 and a fluid outlet 4, and defines an internal space for accommodating a motor unit 6 and a pump unit 8. Electric power is supplied to the motor unit 6 via a terminal (not shown), and the motor unit 6 drives the impeller 22 of the pump unit 8 to rotate. A region (pump chamber) in the internal space of the casing 2 where the pump section 8 is provided communicates with a fluid inlet 3 and a fluid outlet 4. The fluid taken into the pump chamber from the fluid inlet 3 is pressurized as it passes through an impeller 22 of the pump section 8 and is discharged from the fluid outlet 4. In the exemplary embodiment shown in FIGS. 1 to 3 , the fluid is guided axially to the impeller 22 via the fluid inlet 3, and after passing through the impeller 22, the fluid is guided to the fluid outlet 4 via a volute chamber 9 radially outside the impeller 22. The flow path of the volute chamber 9 gradually expands toward the circumferential position of the fluid outlet 4.

[0025] 1 to 3, the pump section 8 is a centrifugal pump that utilizes centrifugal force caused by the rotation of the impeller 22. Specifically, the pump section 8 is a volute pump that has a volute chamber 9 radially outside the impeller 22. The pump section 8 may be any other type of centrifugal pump as long as it includes the impeller 22. In another embodiment, the pump section 8 is a turbine pump having guide vanes. When the pump section 8 is a turbine pump, the volute 9, whose flow path cross-sectional area gradually increases, is an optional configuration.

[0026] As described above, when focusing on the function of the electric pump 1 (1A to 1C), the components of the electric pump 1 (1A to 1C) are mainly classified into a motor section 6 that functions as a motor and a pump section 8 that functions as a pump. On the other hand, the electric pump 1 (1A to 1C) can also be classified into a plurality of elements from the viewpoint of physical components. The components of the electric pump 1 (1A to 1C) will be described below.

[0027] In some embodiments, as shown in FIGS. 1 to 3, the electric pump 1 (1A to 1C) includes a support shaft 10, a rotor 20 supported by the support shaft 10, and a stator 40 facing the rotor 20 without contacting it.

[0028] The support shaft 10 is a hollow or solid shaft member that extends along the central axis of the impeller 22. The support shaft 10 is at least partially housed in the casing 2. In the example shown in FIGS. 1 to 3, the entire support shaft 10 is provided inside the casing 2. In the exemplary embodiment, the support shaft 10 is a stationary shaft (fixed shaft) fixed to the casing 2 or the stator 40. In another embodiment, the support shaft 10 is a rotating shaft rotatably supported by the casing 2 or the stator 40 via bearings.

[0029] The rotor 20 is supported by the support shaft 10 on the radially outer side of the support shaft 10. When the support shaft 10 is a stationary shaft, the rotor 20 is rotatably supported on the support shaft 10 via bearings 12. In another embodiment, the support shaft 10 is a rotating shaft, the rotor 20 is fixed to the support shaft 10, and the support shaft 10 is rotatably supported on the stator 40 side (the molding material 46 of the stator 40) via bearings 12. The bearing 12 may be attached to the rotor 20, in which case the inner peripheral surface of the bearing 12 becomes a sliding surface against the support shaft 10, and a minute bearing gap is formed between the inner peripheral surface of the bearing 12 and the outer peripheral surface of the support shaft 10. In another embodiment, the bearing 12 is attached to the support shaft 10, and a minute bearing gap is formed between the outer peripheral surface of the bearing 12 and the inner peripheral surface of the rotor 20.

[0030] The rotor 20 includes an impeller 22 that faces the fluid inlet 3 of the casing 2 in the axial direction, a magnet 26 that is located on the opposite side of the fluid inlet 3 in the axial direction across the impeller 22, and a rotor main body 21 that supports the impeller 22 and the magnet 26.

[0031] The electric pumps 1A to 1C differ from one another in the shape of the rotor main body 21 and the arrangement of the magnets 26. In the embodiment shown in Figure 1, the rotor body 21 extends cylindrically in the axial direction from the back side of the impeller 22 and supports the magnet 26 so that it is positioned on the inner side of the stator 40 with the magnet 26 facing radially outward. In the embodiment shown in Figure 2, the rotor main body 21 extends cylindrically in the axial direction from the outer periphery of the impeller 22 and supports the magnet 26 so that it is positioned on the outer periphery of the stator 40 with the magnet 26 facing radially inward. In the embodiment shown in Figure 3, the rotor body 21 extends radially outward from the support shaft 10 in a disk shape and supports the magnets 26 so that they are arranged radially facing away from the impeller 22 in the axial direction.

[0032] The impeller 22 includes a plurality of blades 23 arranged in the circumferential direction. An intake port 22A is formed between the leading edges of adjacent blades 23, and an outlet port 22B is formed between the trailing edges of adjacent blades 23. The intake port 22A of the impeller 22 is connected to the fluid inlet 3, and velocity energy is imparted to the fluid that flows in from the fluid inlet 3 by the rotating impeller 22. The outlet port 22B of the impeller 22 is connected to the volute chamber 9, and the fluid that has passed through the impeller 22 flows radially outward via the outlet port 22B, flows into the volute chamber 9, and flows circumferentially through the volute chamber 9 toward the fluid outlet 4. At this time, the fluid is decelerated due to the gradual expansion of the flow path of the volute chamber 9, and the velocity energy is converted into static pressure. In another embodiment, the pump section 8 is a turbine pump, and the fluid after passing through the impeller 22 is decelerated in guide vanes (diffusers) arranged radially outside the impeller 22, and the velocity energy is converted into static pressure.

[0033] The impeller 22 may have a shroud 24. In the exemplary embodiment shown in FIGS. 1 to 3, the impeller 22 is a closed impeller and includes a shroud 24 that covers the blades 23. In other embodiments, the impeller 22 is an open impeller in which there is no shroud covering the blades 23 .

[0034] The magnet 26 is a permanent magnet that is disposed facing the stator 40. In the embodiment shown in FIGS. 1 to 3, the magnet 26 is provided so as to be exposed on the surface of the rotor 20 that faces the stator 40. The magnet 26 may be one for each electric pump 1 (1A to 1C), or may be divided into multiple magnets 26. The shape of the magnet 26 can be selected arbitrarily to match the shape of the stator 40, and may be, for example, cylindrical, arc-shaped, disk-shaped, or rod-shaped.

[0035] In some embodiments, as shown in FIGS. 1-3, the stator 40 includes a stator core 42 and a stator coil 44. The stator core 42 forms a magnetic path through which magnetic flux flows when current is applied to the stator coil 44. The stator coil 44 may be wound around the teeth of the stator core 42 so as to be housed in slots provided in the stator core 42.

[0036] The stator 40 may further include a resin molding material 46 that covers the stator core 42 and the stator coil 44 . The stator core 42 and the stator coil 44 may be embedded in the molding material 46. A stator 40 configured in this manner can be obtained by insert molding. That is, the stator core 42 and the stator coil 44 are set in a mold as insert parts, and resin is injected into the mold, thereby obtaining the stator 40 in which the stator core 42 and the stator coil 44 are embedded in the molding material 46.

[0037] The stator core 42 is disposed with a magnetic gap G between it and the magnet 26 of the rotor 20. The magnetic gap G is formed across the area where the stator core 42 and the magnet 26 face each other. Hereinafter, the area where the magnetic gap G is formed will be referred to as the magnetic gap G formation range (or magnetic gap formation range). 1 and 2, the magnetic gap G extends in an annular shape along the axial direction of the impeller 22. In contrast, in the embodiment shown in Fig. 3, the magnetic gap G extends in a disk shape along the radial direction of the impeller 22.

[0038] The stator 40 faces the rotor 20 without contacting it, with an air gap 48 between them, within the magnetic gap forming range. In an embodiment in which the magnets 26 are exposed on the surface of the rotor 20 and the stator 40 includes a molding material 46, a gap 48 is formed between the magnets 26 and the molding material 46, as shown in FIGS. 1 to 3.

[0039] Here, from the viewpoint of narrowing the magnetic gap G and improving the torque of the motor section 6, it is desirable that the air gap 48 be as narrow as possible. On the other hand, the gap 48 communicates with the pump chamber in which the impeller 22 is provided, and some of the fluid flowing out from the discharge port 22B of the impeller 22 may reach the gap 48. Therefore, if the gap 48 is made too narrow, there is a high risk that foreign matter accompanying the fluid from the impeller 22 will become caught in the gap 48.

[0040] Therefore, in some embodiments, as shown in Figures 1 to 3, the flow path structure of the return flow path 50, which returns a portion of the fluid from the discharge port 22B of the impeller 22 to the intake port 22A, is devised, and a bypass path 60 that bypasses the gap 48 is provided as part of the return flow path 50.

[0041] The return flow passage 50 connects the discharge port 22B and the suction port 22A of the impeller 22. A portion of the fluid that has passed through the impeller 22 is taken into the return flow passage 50 and returned to the suction port 22A of the impeller 22 through the return flow passage 50. 1 to 3, the return flow passage 50 passes at least radially outside the rotor 20 and the stator 40. By using the space radially outside the rotor 20 and the stator 40 as an arrangement area for the return flow passage 50, the degree of freedom in arranging the return flow passage 50, including the bypass path 60 that bypasses the gap 48, is improved.

[0042] The bypass passage 60, which constitutes a part of the return passage 50, is provided so as to bypass the gap 48 that separates the rotor 20 and the stator 40. That is, the fluid that flows into the bypass passage 60 of the return passage 50 is returned to the intake port 22A of the impeller 22 without passing through the gap 48, as shown by the solid arrows in Figures 1 to 3. Note that in Figures 1 to 3, the flow of the fluid that passes through the gap 48 in the part of the return passage 50 that is not the bypass passage 60 is shown by the dashed arrows. In this way, by providing the bypass path 60 in the return flow path 50, it is possible to reduce the flow rate of the fluid passing through the gap 48 between the rotor 20 and the stator 40 in the magnetic gap forming range, thereby reducing the risk of foreign matter entering the gap 48.

[0043] In some embodiments, as shown in FIGS. 1 to 3, the return flow passage 50 includes an annular flow passage 52 formed between the outer peripheral surface of the molding material 46 of the rotor 20 or the stator 40 and the inner peripheral surface of the casing 2. The annular flow passage 52 extends in the axial direction radially outside the magnet 26 and the stator core 42. The annular flow passage 52 passes through the axial position range Y occupied by the magnet 26 and the stator core 42, and extends in the axial direction to the opposite side of the impeller 22 with the magnet 26 and the stator core 42 in between.

[0044] In this way, by forming the annular flow path 52 by utilizing the gap between the outer surface of the molding material 46 of the rotor 20 or stator 40 and the inner surface of the casing 2, the freedom of arrangement of the return flow path 50, including the bypass path 60 that does not pass through the gap 48, is improved.

[0045] 1, the annular flow passage 52 is formed between the inner peripheral surface of the casing 2 and the outer peripheral surface of the molding material 46 of the stator 40, and constitutes a part of the bypass path 60 that bypasses the gap 48. That is, the fluid that has passed through the impeller 22 is divided into a flow toward the annular flow passage 52 and a flow toward the gap 48 on the upstream side of the annular flow passage 52 (the volute chamber 9), and the fluid that has flowed into the annular flow passage 52 is returned to the intake port 22A of the impeller 22 without passing through the gap 48. Thus, in some embodiments, as shown in FIG. 1, the annular flow path 52 is formed as part of the bypass path 60 by utilizing the gap between the inner surface of the casing 2 and the outer surface of the molding material 46 of the stator 40, thereby making it possible to realize the bypass path 60 with a simple configuration.

[0046] In the electric pump 1B shown in Fig. 2, the annular flow passage 52 is formed between the inner circumferential surface of the casing 2 and the outer circumferential surface of the rotor 20. The annular flow passage 52 of the electric pump 1B constitutes part of the return flow passage 50, but is not the bypass passage 60 that bypasses the gap 48. The fluid that has passed through the impeller 22 is divided downstream of the annular flow passage 52 into a flow that flows toward the bypass passage 60 and a flow that flows toward the gap 48. In this way, in some embodiments, as shown in FIG. 2, by utilizing the gap between the inner peripheral surface of the casing 2 and the outer peripheral surface of the molding material 46 of the stator 40 to form an annular flow passage 52 as part of the return flow passage 50, it is possible to realize a return flow passage 50 with a simple configuration, which includes a bypass passage 60 that branches off from the fluid flow toward the gap 48 downstream of the annular flow passage 52.

[0047] 3, the annular flow passage 52 is formed between the inner circumferential surface of the casing 2 and the outer circumferential surface of the rotor 20 and the outer circumferential surface of the molding material 46 of the stator 40, and forms part of a bypass path 60 that bypasses the gap 48. That is, the fluid that has passed through the impeller 22 is divided midway through the annular flow passage 52 into a flow that continues to flow through the annular flow passage 52 and a flow toward the gap 48. Downstream of this dividing point, the fluid flowing through the annular flow passage 52 is returned to the suction port 22A of the impeller 22 without passing through the gap 48. In this way, in some embodiments, as shown in FIG. 3, the annular flow path 52 is formed as part of the bypass path 60 by utilizing the gap between the inner surface of the casing 2 and the outer surface of the molding material 46 of the stator 40 (the portion of the annular flow path 52 downstream of the branch point), thereby making it possible to realize the bypass path 60 with a simple configuration.

[0048] 1 to 3, the bypass passage 60 includes a first flow path 62 connected to the downstream end of the annular flow path 52. Here, the downstream end of the annular flow path 52 refers to one of the axial ends of the annular flow path 52 that is farther from the impeller 22, and in the embodiment of FIGS. 1 to 3, refers to the end of the annular flow path 52 opposite to the upstream end of the annular flow path 52 that is connected to the volute 9. The first flow passage 62 passes radially inward through a radial position range X occupied by the magnet 26 and the stator core 42 at an axial position opposite the impeller 22 with the magnet 26 and the stator core 42 interposed therebetween.

[0049] 1 to 3, the first flow passage 62 is formed between the bottom surface of the casing 2 and the lower surface of the stator 40. In this case, the first flow passage 62 may be a flow passage that spreads out in a disk shape. In another embodiment, the first flow passage 62 is formed inside the molding material 46 of the stator 40. In this case, the first flow passage 62 is an internal flow passage of any shape (for example, linear) provided in the molding material 46.

[0050] The first flow passage 62 may include a plurality of flow passages extending along the radial direction. 4 is a diagram schematically illustrating a first flow path 62 according to one embodiment, and is a radial cross-sectional view of the electric pump 1 including the first flow path 62. In the embodiment shown in the figure, the first flow path 62 includes a plurality of radial flow paths 63 extending radially inward from the downstream end of the annular flow path 52. Each radial flow path 63 extends linearly along the radial direction inside the molding material 46 and opens into a central hole 64 of the molding material 46, through which the support shaft 10 is inserted.

[0051] 1 to 3, in some embodiments, the second flow path 66 is connected to the downstream end of the first flow path 62. Here, the downstream end of the first flow path 62 refers to the end of the first flow path 62 opposite to the upstream end of the first flow path 62 that is connected to the downstream end of the annular flow path 52. The second flow passage 66 passes through an axial position range Y occupied by the magnet 26 and the stator core 42, radially inside the magnet 26 and the stator core 42.

[0052] 1 to 3 , in one embodiment, the second flow path 66 is an internal flow path of the support shaft 10 having a hollow structure. In this case, an opening 11 provided on one end side of the support shaft 10 communicates with the first flow path 62, and the fluid from the first flow path 62 flows into the second flow path 66 inside the support shaft 10 via the opening 11. The fluid that has flowed into the second flow path 66 flows in the axial direction inside the support shaft 10 toward the intake port 22A of the impeller 22. In another embodiment, the second flow path 66 is formed by an axial groove provided on the inner circumferential surface of the rotor body 21 or the molding material 46, or on the outer circumferential surface of the support shaft 10. In this case, the upstream end of the axial groove communicates with the first flow path 62, and the fluid that has flowed into the axial groove flows axially toward the intake port 22A of the impeller 22 via the bearing gap of the bearing 12.

[0053] In some embodiments, as shown in FIGS. 1-3, bypass path 60 bypasses not only air gap 48 between rotor 20 and stator 40, but also the bearing clearance of bearing 12. In the exemplary embodiment shown in Figures 1 to 3, the internal flow path of the support shaft 10 as the second flow path 66 guides the fluid toward the intake port 22A of the impeller 22 via the radially inner side of the bearing gap, sandwiching the cylindrical support shaft 10, and the fluid flowing through the second flow path 66 does not pass through the bearing gap of the bearing 12.

[0054] 1 to 3, the bypass passage 60 is provided with a throttle 15 that reduces the cross-sectional area of ​​the passage downstream of the second passage 66. The throttle 15 has a function of adjusting the flow rate of the fluid that is returned to the suction port 22A of the impeller 22 via the bypass passage 60. When the second flow path 66 is formed by an internal flow path of the hollow support shaft 10, an orifice plate may be provided at the end of the support shaft 10 as the restriction 15. In other embodiments, the restriction 15 is realized by a gap between the support shaft 10 and a cap (not shown) fitted to the end of the support shaft 10, or by an orifice hole provided in the cap.

[0055] By providing the bypass path 60 having the above configuration, the flow rate of fluid passing through the gap 48 between the rotor 20 and the stator 40 is reduced compared to conventional electric pumps that do not have a bypass path, thereby suppressing the intrusion of foreign matter into the gap 48. In order to further reduce the risk of foreign matter entering the gap 48, it is advantageous to set the flow path cross-sectional area of ​​the bypass path 60 to be relatively larger than that of the gap 48. In this case, a larger flow rate of the fluid will be returned to the suction port 22A of the impeller 22 via the bypass path 60, and as a result, the flow rate of the fluid passing through the gap 48 will be further reduced.

[0056] Next, the detailed structure of the electric pump 1 (1A to 1C) shown in FIGS. 1 to 3 will be described with reference to FIGS. FIG. 5 is an axial cross-sectional view showing a specific structural example of an electric pump 1A according to one embodiment. Fig. 6 is an axial cross-sectional view showing a specific example of the structure of an electric pump 1B according to another embodiment. Fig. 7 is a partial cross-sectional perspective view showing the internal structure of the electric pump 1B shown in Fig. 6. FIG. 8 is an axial cross-sectional view showing an example of the structure of an electric pump 1C according to yet another embodiment.

[0057] 5, the electric pump 1A includes a casing 2 having a front casing 2A and a rear casing 2B, and a motor unit 6 and a pump unit 8 disposed within the casing 2. The front casing 2A defines a pump chamber in which an impeller 22 is housed, and has a fluid inlet 3 and a fluid outlet 4 communicating with the pump chamber. The front casing 2A forms a volute chamber 9 radially outward of the impeller 22.

[0058] The electric pump 1A shown in FIG. 5 includes a support shaft 10, a rotor 20 including an impeller 22, a magnet 26, and a rotor body 21, and a stator 40 including a stator core 42, a stator coil 44, and a molding material 46. The stator 40 is fixed to the rear casing 2B by any method (for example, press fitting). The support shaft 10 is a stationary shaft that is fixed to the molding material 46 of the stator 40 by any method (for example, press fitting). The rotor 20 is rotatably supported on the support shaft 10 by the bearing 12, with the rear side portion of the impeller 22 (part of the rotor main body 21 and the magnet 26) inserted into the recess of the molding material 46. An annular gap 48 is formed between the outer peripheral surface of the portion of the rotor 20 inserted into the recess of the molding material 46 and the inner peripheral surface of the recess of the molding material 46, and the rotor 20 rotates without contacting the stator 40, facing the stator 40 across the gap 48 in the radial direction.

[0059] As shown in FIG. 5 , a cylindrical magnet 26 is provided on the outer peripheral surface of the portion of the rotor body 21 inserted into the recess of the molding material 46, facing an annular gap 48. A stator core 42 is disposed within the molding material 46 radially outward of the magnet 26, forming a radial magnetic gap between the magnet 26 and the stator core 42. The gap 48 is a gap between the rotor 20 and the stator 40 within the magnetic gap forming range and communicates with the volute chamber 9. After passing through the impeller 22, a portion of the fluid may reach the gap 48 from the volute chamber 9. The fluid that flows into the gap 48 passes through the gap between the rotor body 21 and the molding material 46 and the bearing gap of the bearing 12, and is discharged toward the suction port 22A of the impeller 22, as indicated by the dashed arrow in FIG. 5 .

[0060] As shown in FIG. 5 , an annular flow passage 52 is formed between the outer peripheral surface of the molding material 46 of the stator 40 and the inner peripheral surface of the casing 2. The annular flow passage 52 extends in the axial direction from its upstream end connected to the volute 9, passing radially outside the stator core 42 and the magnet 26. The downstream end of the annular flow passage 52 is connected to the upstream ends of multiple first flow passages 62 provided inside the molding material 46. Each of the first flow passages 62 extends radially inward toward an opening 11 at the end of the hollow support shaft 10. The downstream end of each first flow passage 62 is connected to a second flow passage 66 serving as an internal flow passage of the support shaft 10. The second flow passage 66 extends axially toward the opposite end of the support shaft 10, passing radially inside the magnet 26 and the stator core 42. A cap 16 is attached to the opposite end of the support shaft 10, and a throttle 15 is formed by a gap between the support shaft 10 and the cap 16. In other embodiments, the restrictor 15 may be an orifice plate provided at the end of the support shaft 10 or an orifice hole provided in the cap 16 . The annular flow path 52, the first flow path 62, and the second flow path 66 configured as described above form a bypass path 60 that bypasses the gap 48.

[0061] 5, the bypass passage 60 formed by the annular passage 52, the first passage 62, and the second passage 66 is formed inside the stationary portion as a route that surrounds most of the rotor 20 and the stator 40 in the axial cross section of the electric pump 1A. This allows for a high degree of freedom in arranging the bypass passage 60 that bypasses the gap 48 that exists in the region where the magnetic gap between the stator core 42 and the magnet 26 is formed.

[0062] 6, the electric pump 1B includes a casing 2 including a front casing 2A and a rear casing 2B, and a motor section 6 and a pump section 8 disposed within the casing 2. The front casing 2A defines a pump chamber in which an impeller 22 is housed, and has a fluid inlet 3 and a fluid outlet 4 communicating with the pump chamber. The front casing 2A forms a volute chamber 9 radially outward of the impeller 22.

[0063] The electric pump 1B shown in FIG. 6 includes a support shaft 10, a rotor 20 including an impeller 22, a magnet 26, and a rotor body 21, and a stator 40 including a stator core 42, a stator coil 44, and a molding material 46. The stator 40 is fixed to the rear casing 2B by any method (for example, press fitting). The support shaft 10 is a stationary shaft that is fixed to the molding material 46 of the stator 40 by any method (for example, press fitting). The rotor 20 forms a recess for accommodating the stator 40 on the rear side of the impeller 22. That is, the rotor main body 21 extends in the axial direction from the outer peripheral edge of the rotor main body 21 facing the volute chamber 9, and the rotor 20 has a cylindrical shape on the rear side of the impeller 22. The stator 40 is inserted into the recess on the inner peripheral side of the cylindrical portion of the rotor 20 (the portion of the rotor 20 on the rear side of the impeller 22). In other words, the stator 40 is surrounded by the cylindrical portion of the rotor 20 radially outside the stator 40. With the stator 40 inserted into the recess on the inner peripheral side of the cylindrical portion of the rotor 20, the rotor 20 is rotatably supported on the support shaft 10 by the bearings 12. An annular gap 48 is formed between the inner surface of the cylindrical portion of the rotor 20 and the outer surface of the molding material 46 of the stator 40, and the rotor 20 rotates without contacting the stator 40 while facing the stator 40 in the radial direction across the gap 48.

[0064] As shown in FIG. 6 , in the cylindrical portion of the rotor 20, a cylindrical magnet 26 is provided on the inner circumferential surface of the rotor body 21, facing an annular gap 48. A stator core 42 is disposed within the molding material 46 radially inward of the magnet 26, forming a radial magnetic gap between the magnet 26 and the stator core 42. The gap 48 is a gap between the rotor 20 and the stator 40 within the magnetic gap forming range, and is connected to the volute chamber 9 via the annular flow passage 52. After passing through the impeller 22, a portion of the fluid can reach the gap 48 from the volute chamber 9 via the annular flow passage 52. The fluid that flows into the gap 48 is discharged to the suction port 22A of the impeller 22 through the gap between the rotor body 21 and the molding material 46 and the bearing gap of the bearing 12, as indicated by the dashed arrows in FIG. 6 .

[0065] As shown in FIGS. 6 and 7 , an annular flow passage 52 is formed between the outer circumferential surface of the cylindrical portion of the rotor 20 and the inner circumferential surface of the casing 2. The annular flow passage 52 extends axially from its upstream end connected to the volute 9, passing radially outside the stator core 42 and the magnets 26. The downstream end of the annular flow passage 52 is connected to the upstream ends of multiple first flow passages 62 provided inside the molding material 46. As shown in FIG. 7 , each of the first flow passages 62 is a radial flow passage 63 extending radially and extending radially inward toward an opening 11 at the end of the hollow support shaft 10. Each of the first flow passages 62 opens into a central hole 64 of the molding material 46 into which the support shaft 10 is inserted. The downstream end of each first flow passage 62 is connected via the central hole 64 to a second flow passage 66, which serves as an internal flow passage of the support shaft 10. The second flow passage 66 extends axially toward the opposite end of the support shaft 10, passing radially inside the magnets 26 and the stator core 42. A cap 16 is attached to the opposite end of the support shaft 10, and the gap between the support shaft 10 and the cap 16 forms a restriction 15. In other embodiments, the restriction 15 may be an orifice plate provided at the end of the support shaft 10 or an orifice hole provided in the cap 16. The first flow path 62 and the second flow path 66 configured as described above form a bypass path 60 that bypasses the gap 48 .

[0066] 6 and 7, the return flow passage 50, which is a combination of the bypass passage 60 formed by the first flow passage 62 and the second flow passage 66 and the annular flow passage 52, is formed as a route that surrounds most of the rotor 20 and the stator 40 in the axial cross section of the electric pump 1B. Therefore, the return flow passage 50, which includes the bypass passage 60 that bypasses the gap 48, can be arranged with a high degree of freedom.

[0067] 8, the electric pump 1C includes a casing 2 including a front casing 2A and a rear casing 2B, and a motor unit 6 and a pump unit 8 disposed within the casing 2. The front casing 2A defines a pump chamber in which an impeller 22 is housed, and has a fluid inlet 3 and a fluid outlet 4 communicating with the pump chamber. The front casing 2A forms a volute chamber 9 radially outward of the impeller 22.

[0068] The electric pump 1C shown in FIG. 8 includes a support shaft 10, a rotor 20 including an impeller 22, a magnet 26, and a rotor body 21, and a stator 40 including a stator core 42, a stator coil 44, and a molding material 46. The stator 40 is fixed to the rear casing 2B by any method (for example, press fitting). The support shaft 10 is a stationary shaft that is fixed to the molding material 46 of the stator 40 by any method (for example, press fitting). The rotor 20 is rotatably supported on the support shaft 10 by bearings 12, with the axial end face of the rotor 20 opposite the impeller 22 facing the axial end face of the stator 40. A disk-shaped gap 48 is formed between the opposing axial end faces of the rotor 20 and the stator 40, and the rotor 20 rotates without contacting the stator 40, facing the stator 40 across the gap 48 in the axial direction.

[0069] As shown in FIG. 8 , a disk-shaped magnet 26 is provided on the axial end face of the rotor body 21 opposite the impeller 22, facing a gap 48. A stator core 42 is disposed within a molded material 46 on the axially opposite side of the magnet 26 from the impeller 22, and an axial magnetic gap is formed between the magnet 26 and the stator core 42. The gap 48 is a gap between the rotor 20 and the stator 40 within the magnetic gap-forming range and communicates with the volute chamber 9 via the upstream portion of the annular flow passage 52. A portion of the fluid passing through the impeller 22 can reach the gap 48 from the volute chamber 9 via the upstream portion of the annular flow passage 52. The fluid that flows into the gap 48 is discharged to the suction port 22A of the impeller 22 via the gap 48 and a bearing gap between the outer circumferential surface of the support shaft 10 and the inner circumferential surface of the bearing 12, as indicated by the dashed arrow in FIG. 8 .

[0070] As shown in FIG. 8 , an annular flow passage 52 is formed between the outer circumferential surface of the rotor main body 21 of the rotor 20 and the outer circumferential surface of the molding material 46 of the stator 40 and the inner circumferential surface of the casing 2. The annular flow passage 52 extends axially from its upstream end connected to the volute 9, passing radially outside the stator core 42 and the magnets 26. The downstream end of the annular flow passage 52 is connected to the upstream ends of multiple first flow passages 62 provided inside the molding material 46. Each of the first flow passages 62 extends radially inward toward an opening 11 at the end of the hollow support shaft 10. The downstream end of each first flow passage 62 is connected to a second flow passage 66 serving as an internal flow passage of the support shaft 10. The second flow passage 66 extends axially toward the opposite end of the support shaft 10, passing radially inside the magnets 26 and the stator core 42. A cap 16 is attached to the opposite end of the support shaft 10, and a throttle 15 is formed by a gap between the support shaft 10 and the cap 16. In other embodiments, the restrictor 15 may be an orifice plate provided at the end of the support shaft 10 or an orifice hole provided in the cap 16 . The annular flow path 52, the first flow path 62, and the second flow path 66 configured as described above form a bypass path 60 that bypasses the gap 48.

[0071] 8, the bypass passage 60 formed by the annular passage 52, the first passage 62, and the second passage 66 is formed inside the stationary portion as a route that surrounds most of the rotor 20 and the stator 40 in the axial cross section of the electric pump 1C. This allows for a high degree of freedom in arranging the bypass passage 60 that bypasses the gap 48 that exists in the region where the magnetic gap between the stator core 42 and the magnet 26 is formed.

[0072] Although the electric pump 1 (1A to 1C) according to several embodiments has been described above, the present invention is not limited to the above-described embodiments without departing from the spirit of the present invention. For example, the electric pump 1 may further include a control board for controlling the electric pump 1 in addition to the rotor 20 and the stator 40.

[0073] FIG. 9 is a diagram showing the structure of an electric pump 1D according to another embodiment. The embodiment shown in Fig. 9 is obtained by adding a control board and its heat dissipation path, which will be described below, to the electric pump 1A shown in Fig. 5. In other embodiments, a control board and its heat dissipation path, which will be described below, are added to the electric pump 1B shown in Figs. 6 and 7 or the electric pump 1C shown in Fig. 8.

[0074] In some embodiments, the electric pump 1D has a board 100 for controlling the electric pump 1, as shown in Fig. 9. The board 100 may be, for example, a printed wiring board, and is housed in a board chamber 110. The board 100 is supported at a desired position within the board chamber 110 by a support (not shown).

[0075] At least one electronic component 102 for controlling the electric pump 1 is mounted on the surface of the substrate 100. The electronic component 102 includes a semiconductor device for controlling the current supplied to the stator coil 44. One or more electronic components 102 may be mounted on the surface of the substrate 100 facing the rotor 20.

[0076] In some embodiments, the electric pump 1 has a partition wall 120 that separates a pump motor chamber in which the rotor 20 and the stator 40 are housed from a substrate chamber 110 in which the substrate 100 is housed. A heat dissipation flow path 123 that constitutes a part of the return flow path 50 (bypass path 60) is formed between the rotor 20 and a surface 122 of the partition wall 120 on the pump motor chamber side. In the embodiment shown in FIG. 9 , a first flow path 62 of the bypass path 60 functions as the heat dissipation flow path 123. By providing the heat dissipation flow path 123 between the rotor 20 and the partition wall 120, the fluid flowing through the heat dissipation flow path 123 can promote heat dissipation from the substrate 100 and the electronic components 102. Furthermore, since the heat dissipation flow path 123 and the substrate chamber 110 are separated by the partition wall 120, the fluid is prevented from entering the substrate chamber 110 from the heat dissipation flow path 123, and damage to the substrate 100 and the electronic components 102 can be prevented.

[0077] 9, the partition wall 120 is formed by a portion of the molding material 46, a portion of the rear casing 2B, and a lid member 130 having a higher thermal conductivity than the molding material 46 and the rear casing 2B. The lid member 130 may be made of aluminum, copper, or an alloy thereof, which have excellent thermal conductivity. The lid member 130 is provided in at least a portion of the area in which the substrate 100 is arranged. In the example shown in Fig. 9, the lid member 130 is arranged so that the entire lid member 130 fits within the area in which the substrate 100 is arranged. In other embodiments, the lid member 130 extends beyond the area in which the substrate 100 is arranged. The lid member 130 is provided so as to close an opening 132 provided in an annular portion 121 of the partition wall portion 120 formed by the molding material 46 and the rear casing 2B. A seal member 134, which may be, for example, an O-ring, is provided between the lid member 130 and the opening 132 of the molding material 46 and the rear casing 2B. The seal member 134 prevents fluid from entering the board chamber 110 from the heat dissipation flow path 123, with the aim of protecting the board 100 and electronic components 102.

[0078] In some embodiments, the partition 120 (lid member 130 ) is positioned so as to at least partially contact at least one electronic component 102 . In the example shown in FIG. 9, the partition wall 120 (lid member 130) comes into contact with the surface of the electronic component 102A, and the partition wall 120 (lid member 130) functions as a heat sink for the electronic component 102A.

[0079] Fig. 10 is an axial cross-sectional view showing a specific structural example of an electric pump according to yet another embodiment. Fig. 11 is a perspective view showing a cross-section of an electric pump according to an embodiment at an axial position passing through a radial flow path and a central hole. Fig. 12A is a perspective view showing a cover member of an electric pump according to an embodiment. Fig. 12B is a perspective view showing a cover member of an electric pump according to another embodiment. Fig. 12C is a perspective view showing a cover member of an electric pump according to yet another embodiment. The electric pump 1E shown in Fig. 10 is obtained by modifying the cover member 130 and the surrounding structure of the cover member 130 of the electric pump 1D shown in Fig. 9. Hereinafter, electric pumps 1 (1E) according to several other embodiments will be described with reference to Figs. 10 to 12C.

[0080] In some embodiments, the electric pump 1 (1E) has a partition wall 220 that separates a pump motor chamber in which the rotor 20 and the stator 40 are housed from a substrate chamber 110 in which the substrate 100 is housed, as shown in Fig. 10. A heat dissipation flow path 223 that constitutes a part of the return flow path 50 (bypass path 60) is formed between the rotor 20 and a surface 222 of the partition wall 220 on the pump motor chamber side. In the embodiment shown in Fig. 10, the central hole 64 of the molding material 46 of the bypass path 60 mainly functions as the heat dissipation flow path 223.

[0081] 11 , at axial positions of the electric pump 1 where the radial flow passages 63 and the central hole 64 are present, the multiple regions 47 separated from one another by the radial flow passages 63 have partially annular contours including an inner arc 47A and an outer arc 47B. The outer diameter of the central hole 64 matches the inner diameter of the inner arc 47A of the contours of the multiple regions 47 of the molding material 46. This is in contrast to the configuration in FIG. 7, in which a relatively small diameter central hole 64 is formed surrounded by a plurality of sector-shaped regions of molding material 46 separated from each other by radial flow passages 63 .

[0082] In this way, by providing a central hole 64 having an outer diameter that matches the inner diameter of the inner arc 47A of the outline of the multiple regions 47 of the molding material 46 between the rotor 20 and the partition wall portion 120 as a heat dissipation flow path 223, the contact area between the heat dissipation flow path 223 and the partition wall portion 220 is increased, and heat dissipation from the substrate 100 and the electronic component 102 can be further promoted.

[0083] 10, the partition wall 220 is formed by a portion of the molding material 46, a portion of the rear casing 2B, and a lid member 230 having a higher thermal conductivity than the molding material 46 and the rear casing 2B. Like the above-described lid member 130, the lid member 230 may be made of aluminum, copper, or an alloy thereof, which have excellent thermal conductivity. The lid member 230 is provided in at least a portion of the area where the substrate 100 is disposed. The lid member 230 is provided so as to close an opening 232 provided in an annular portion 221 of a partition wall portion 220 formed by the molding material 46 and the rear casing 2B. Specifically, the molding material 46 has an annular protrusion 233 that protrudes toward the substrate chamber 110, and the lid member 230 fits into the opening 232 provided in the annular protrusion 233. A seal member 234, which may be, for example, an O-ring, is provided between the lid member 230 and the opening 232 of the annular protrusion 233 of the molding material 46. In this way, by providing the opening 232 to be closed by the lid member 230 in a single component (the molding material 46), fluid leakage can be more reliably prevented compared to when openings 232 are provided in both the molding material 46 and the rear casing 2B (FIG. 9). 10 and 12, the cover member 230 includes a flange 236 having a diameter larger than the inner diameter of the opening 232. The flange 236 of the cover member 230 abuts against the annular protrusion 233 of the molding material 46 on the substrate chamber 110 side, enabling the cover member 230 to be positioned relative to the annular portion 221 of the partition wall portion 220.

[0084] In some embodiments, the partition wall 220 (lid member 230) is disposed so as to be in at least partial contact with at least one electronic component 102. In the example shown in Fig. 10, the partition wall 220 (lid member 230) is in contact with the surfaces of the electronic components 102A and 102B, and the partition wall 220 (lid member 230) functions as a heat sink for the electronic components 102A and 102B.

[0085] In some embodiments, the cover member 230 has a plurality of heat dissipation protrusions 238 formed on a surface 237 (a part of the surface 222 of the partition wall portion 220 on the pump motor chamber side) facing the heat dissipation flow path 223. The heat dissipation protrusions 238 are heat transfer area enlarging elements that enlarge the contact area between the fluid flowing through the heat dissipation flow path 223 and the cover member 230.

[0086] In some embodiments, the heat dissipation protrusion 238 of the cover member 230A includes a plurality of heat dissipation pins 238A formed on the surface 237 of the cover member 230A, as shown in FIGS. 11 and 12A. 12A, the plurality of heat dissipation pins 238A are arranged in the circumferential direction at different radial positions of the cover member 230A. In the exemplary embodiment shown in FIG. 12A, the plurality of heat dissipation pins 238A are arranged to form four circumferential rows at different radial positions. Distributing the plurality of heat dissipation pins 238A at different radial positions can promote heat transfer between the fluid and the heat dissipation pins 238A. The shape of the heat dissipation pin 238A is not particularly limited, and may be, for example, a columnar shape having any cross-sectional shape, including a cylindrical shape and a rectangular columnar shape. In the exemplary embodiment shown in FIG. 12A, the heat dissipation pin 238A is a columnar shape having a circular cross-section. Furthermore, although FIG. 12A shows an example in which all of the plurality of heat dissipation pins 238A have the same shape, some of the plurality of heat dissipation pins 238A may have a different shape from the others.

[0087] In some other embodiments, the heat dissipating protrusion 238 includes a plurality of heat dissipating fins (238B, 238C) formed on the surface 237 of the cover member 230 (230B, 230C), as shown in FIGS. 12B and 12C. The heat dissipation fins (238B, 238C) have a flat or curved plate shape when viewed from the normal direction of the surface 237 of the cover member 230 (230B, 230C).

[0088] In some embodiments, the heat dissipating protrusion 238 of the cover member 230B includes a plurality of flat heat dissipating fins 238B, as shown in FIG. 12B. The heat dissipation fins 238B are arranged in the circumferential direction at different radial positions of the cover member 230B. In the exemplary embodiment shown in Fig. 12B, the heat dissipation fins 238B are arranged to form two circumferential rows at different radial positions. By distributing the heat dissipation fins 238B at different radial positions, heat transfer between the fluid and the heat dissipation fins 238B can be promoted. Each heat dissipation fin 238B is oriented along the radial direction of the cover member 230B. That is, when viewed from the normal direction of the surface 237 of the cover member 230B, each heat dissipation fin 238B is arranged so that the plate shape of the heat dissipation fin 238B is aligned along the radial direction of the cover member 230B. In the exemplary embodiment shown in FIG. 12B , the inner fins 240 of the heat dissipation fins 238B belonging to the inner circumferential row are oriented in a direction that coincides with the radial direction of the cover member 230B, and a pair of adjacent outer fins 242 of the heat dissipation fins 238B belonging to the outer circumferential row, which sandwich the inner fin 240 in the circumferential direction, are oriented in the same direction as the inner fin 240. As a result, the fluid that passes through the pair of outer fins 242 comes into contact with the inner fins 240, further promoting heat transfer between the fluid and the heat dissipation fins 238B.

[0089] In some embodiments, the heat dissipating protrusion 238 of the cover member 230C includes a plurality of curved plate-shaped heat dissipating fins 238C, as shown in FIG. 12C. When viewed from the normal direction of the surface 237 of the cover member 230C, the heat dissipation fins 238C are curved so that the angle of inclination relative to the radial direction increases as they extend radially outward. In the embodiment shown in FIG. 12C , the heat dissipation fins 238C include a plurality of long fins 250 having a large fin length and a plurality of short fins 252 having a fin length shorter than that of the long fins 250. The long fins 250 and the short fins 252 are arranged alternately in the circumferential direction. In the exemplary embodiment shown in FIG. 12C , eight long fins 250 and eight short fins 252 are arranged alternately in the circumferential direction on the surface 237 of the cover member 230C. Each short fin 252 is arranged between the outer peripheral portions of a pair of adjacent long fins 250 in the circumferential direction. In this way, by arranging the short fins 252 in the inter-long fin passages between the outer peripheral portions of the long fins 250, heat transfer between the fluid and the heat dissipation fins 238B can be further promoted.

[0090] 10 to 12C, the tip end surface of the heat dissipating protrusion 238 is flush with the portion of the pump motor chamber side surface 222 of the partition wall portion 220 other than the heat dissipating protrusion 238. In other embodiments, the heat dissipating protrusion 238 protrudes toward the pump motor chamber so as to intrude into the heat dissipation flow path 223, and the tip end surface of the heat dissipating protrusion 238 is located closer to the heat dissipation flow path 223 than the portion of the pump motor chamber side surface 222 of the partition wall portion 220 other than the heat dissipating protrusion 238.

[0091] In some embodiments, the cover member 230 of the electric pump 1 (1E) includes a combination of two or more types of heat dissipating protrusions 238 selected from the heat dissipating pins 238A and the heat dissipating fins 238B and 238C described above. Furthermore, the cover member 230 of the electric pump 1 (1E) may include other heat dissipating protrusions 238 other than the heat dissipating pins 238A or the heat dissipating fins 238B, 238C described above.

[0092] According to the above-described embodiment, for example, the following advantageous effects can be obtained. [1] By providing a bypass path 60 that bypasses the gap 48 in the area where the magnetic gap G is formed between the magnet 26 and the stator core 42, the flow rate of fluid flowing into the gap 48 can be reduced, and the risk of foreign matter entering the gap 48 from the pump chamber can be reduced. Therefore, it is possible to narrow the magnetic gap G while suppressing foreign matter from getting caught in the gap 48, thereby improving the torque of the motor unit 6. Furthermore, by utilizing the space radially outside the rotor 20 and the stator 40 as an arrangement area for the return flow passage 50, the degree of freedom in arranging the return flow passage 50 including the bypass passage 60 that bypasses the gap 48 is improved. [2] By using the annular flow passage 52 formed between the outer peripheral surface of the rotor 20 or the molding material 46 and the inner peripheral surface of the casing 2 as part of the return flow passage 50, the return flow passage 50, including the bypass path 60 that bypasses the gap 48, can be arranged with a high degree of freedom. [3] By connecting the first flow path 62, which passes through the radial position of the gap 48 on the opposite side of the impeller 22 in the axial direction across the gap 48, to the downstream end of the annular flow path 52, the fluid after passing through the annular flow path 52 can be directed toward the intake port 22A of the impeller 22 without passing through the gap 48. [4] The fluid that has passed through the first flow path 62 can be guided toward the intake port 22A of the impeller 22 via a second flow path 66 that passes through an axial position of the gap 48 on the radial inside of the gap 48. [5] When the bypass path 60 bypasses not only the gap 48 but also the bearing gap between the bearing 12 and the support shaft 10, the circulating flow through the bearing gap can be reduced by directing a portion of the fluid circulating from the discharge port 22B of the impeller 22 toward the suction port 22A through the bypass path 60. This reduces the risk of foreign matter entering the gap 48 as well as the bearing gap. [6] When the bypass path 60 includes an internal flow path (second flow path 66) of the hollow support shaft 10, the circulating flow through the bearing gap can be reduced, and the simple configuration can reduce the risk of foreign matter entering the bearing gap. [7] When the cross-sectional area of ​​the bypass passage 60 is larger than that of the gap 48, a major portion of the circulating fluid flowing from the discharge port 22B of the impeller 22 toward the suction port 22A can be guided to the bypass passage 60, further reducing the circulating fluid flow passing through the gap 48. This effectively reduces the risk of foreign matter entering the gap 48.

[0093] In this specification, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement strictly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent rectangular shapes or cylindrical shapes in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components. [Explanation of symbols]

[0094] 1(1A~1E): Electric pump 2: Casing 10: Support shaft 12: Bearing 20: Rotor 22: Impeller 22A: Inlet 22B:Discharge port 26: Magnet 40: Stator 42: Stator core 44: Stator coil 46:Molding material 48 :Void 50: Return flow path 52: Annular flow path 60: Bypass road 62: First flow path 66: Second flow path 100: Substrate 102: Electronic parts 110: Substrate room 120,220: Partition wall part 123,223: Heat radiation flow path 130, 230: Lid member 238: Heat dissipation protrusion G: Magnetic gap X: Radial position range Y: Axial position range

Claims

1. A support shaft; a rotor including an impeller and a magnet and supported by the support shaft on the radially outer side of the support shaft; a stator including a stator core disposed with a magnetic gap between it and the magnet, the stator facing the rotor without contact with the rotor across an air gap within a range where the magnetic gap is formed; a return flow path that communicates a discharge port of the impeller with a suction port of the impeller and that passes through at least the radial outside of the rotor and the stator so as to return the fluid that has passed through the impeller to the suction port of the impeller; Equipped with The return passage includes a bypass passage that bypasses the gap separating the rotor and the stator. Electric pump.

2. a casing that houses the rotor, the stator, and the support shaft; The stator includes: A stator coil; a molding material that covers the stator core and the stator coil; Including, The return flow passage includes an annular flow passage formed between an outer peripheral surface of the rotor or the molding material and an inner peripheral surface of the casing. The electric pump according to claim 1 .

3. The bypass path is a first flow path connected to a downstream end of the annular flow path, the first flow path passing through a radial position range occupied by the magnet and the stator core at an axial position on the opposite side of the impeller with the magnet and the stator core interposed therebetween; Contains The electric pump according to claim 2.

4. The bypass path is a second flow path connected to a downstream end of the first flow path, the second flow path passing through an axial position range occupied by the magnet and the stator core, radially inside the magnet and the stator core; Contains The electric pump according to claim 3.

5. a bearing for rotatably supporting the rotor on the support shaft; The bypass path bypasses both the bearing gap of the bearing and the air gap. The electric pump according to claim 1 or 2.

6. The bypass passage includes an internal flow passage of the support shaft having a hollow structure. The electric pump according to claim 5.

7. The cross-sectional area of ​​the bypass passage is larger than the cross-sectional area of ​​the gap. The electric pump according to claim 1 or 2.

8. a casing that houses the rotor, the stator, and the support shaft; the rotor is disposed radially outside the stator and facing the stator across the gap, the return passage includes an annular passage formed between an outer peripheral surface of the rotor and an inner peripheral surface of the casing, The bypass passage is configured to bypass the gap downstream of the annular flow path. The electric pump according to claim 1 or 2.

9. a casing that houses the rotor, the stator, and the support shaft; The stator includes: A stator coil; a molding material that covers the stator core and the stator coil; Including, the rotor is disposed radially inside the stator and facing the stator across the gap, At least a portion of the bypass passage is formed between an outer peripheral surface of the molding material and an inner peripheral surface of the casing. The electric pump according to claim 1 or 2.

10. A casing that houses the rotor, the stator, and the support shaft Equipped with The stator includes: A stator coil; a molding material that covers the stator core and the stator coil; Including, the rotor is disposed opposite the stator located on the opposite side in the axial direction across the gap, At least a portion of the bypass passage is formed between the outer peripheral surface of the rotor and the outer peripheral surface of the molding material and the inner peripheral surface of the casing. The electric pump according to claim 1 or 2.

11. a substrate on which electronic components for controlling the electric pump are mounted; a partition wall separating a pump motor chamber in which the stator and the rotor are housed from a substrate chamber in which the substrate is housed; Equipped with The return flow path includes a heat dissipation flow path formed between the rotor and the partition wall. The electric pump according to claim 1 or 2.

12. The partition wall portion is an annular portion having an opening communicating between the pump motor chamber and the base plate chamber; a cover member provided to close the opening of the annular portion and having a higher thermal conductivity than the annular portion; Contains The electric pump according to claim 11.

13. The cover member has a plurality of heat dissipation protrusions formed on a surface facing the heat dissipation flow path. The electric pump according to claim 12.

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