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, 1B) 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; 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 in the formation range of the magnetic gap G in a non-contact manner; and a return flow passage 50 for establishing communication between a discharge port 22B of the impeller 22 and a suction port 22A of the impeller 22, and returning 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 provided at a radial position inside the gap 48 on the back side of the impeller 22 so as to bypass 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 connects the discharge port of the impeller with the suction port of the impeller and returns the fluid that has passed through the impeller to the suction port of the impeller; Equipped with The return flow passage includes a bypass passage provided on the rear side of the impeller at a radial position inside the gap separating the rotor and the stator so as to bypass the gap.

[0008] [2] In some embodiments, in the configuration of [1] above, The rotor has a neck between the impeller and the magnet in the axial direction, the neck being constricted radially inward from the outer circumferential surface of the impeller and the outer circumferential surface of the magnet, the neck defines a cavity on the rear side of the impeller that communicates with the gap; The bypass passage includes an internal passage formed in the rotor that opens into the cavity.

[0009] [3] In some embodiments, in the configuration of [2] above, The rotor is a hollow portion into which the support shaft is inserted; a first through hole that passes through the neck and connects the cavity to the hollow portion; Including, The bypass path includes a first through-hole as an internal flow path.

[0010] [4] In some embodiments, in the configuration of [3] above, The support shaft terminates midway through the hollow portion so that the opening of the first through hole into the hollow portion is at least partially open.

[0011] [5] In some embodiments, in the configuration of [3] or [4] above, The electric pump is provided with a bearing that is located on the opposite side of the impeller in the axial direction across the opening of the first through hole into the hollow portion, and that rotatably supports the rotor on the support shaft.

[0012] [6] In some embodiments, in the configuration of [2] above, The rotor is a shoulder having an outer diameter larger than that of the neck, positioned on the opposite side of the impeller in the axial direction across the neck, and holding the magnet on the outer periphery; a second through hole penetrating the shoulder so as to pass through the radially inner side of the gap; Including, The bypass path includes a second through-hole as an internal flow path.

[0013] [7] In some embodiments, in the configuration of [6] above, The electric pump includes a bearing for rotatably supporting the rotor on the support shaft, The second through hole passes through the radially inner side of the gap and connects the cavity to the downstream side of the gap and the upstream side of the bearing gap between the bearing and the support shaft.

[0014] [8] In some embodiments, in the configuration of [6] or [7] above, The support shaft has an axial flow passage extending along the axial direction of the support shaft so as to penetrate the support shaft, The return flow path is A second through hole; an axial flow passage of the support shaft that communicates with the second through hole; Includes:

[0015] [9] In some embodiments, in the configuration of [9] 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 wall surface of the partition portion facing the rotor forms an intermediate flow passage for guiding the fluid that has passed through the second through hole to the axial flow passage. [Effects of the Invention]

[0016] 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]

[0017] [Figure 1] 1 is an axial cross-sectional view showing a schematic configuration of an electric pump according to an embodiment. [Figure 2A] FIG. 10 is a cross-sectional view showing another example of the configuration of the bypass passage of the electric pump. [Figure 2B] FIG. 10 is a cross-sectional view showing yet another example of the configuration of the bypass passage of the electric pump. [Figure 3] FIG. 10 is an axial cross-sectional view showing a schematic configuration of an electric pump according to another embodiment. [Figure 4] 1 is an axial cross-sectional view showing a specific structural example of an electric pump according to an embodiment; [Figure 5] FIG. 10 is an axial cross-sectional view showing a specific structural example of an electric pump according to another embodiment. [Figure 6] 10A and 10B are diagrams illustrating the structure of an electric pump according to still another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] Fig. 1 is an axial cross-sectional view showing a schematic configuration of an electric pump 1A according to one embodiment. Fig. 2A is a cross-sectional view showing another example of the configuration of a bypass passage of an electric pump. Fig. 2B is a cross-sectional view showing yet another example of the configuration of a bypass passage of an electric pump. Fig. 3 is an axial cross-sectional view showing a schematic configuration of an electric pump 1B according to another embodiment. Hereinafter, when referring to an electric pump according to some embodiments of the present invention including the electric pumps 1A and 1B, they will be referred to as the electric pump 1 (1A, 1B).

[0020] As shown in FIGS. 1 and 3, in some embodiments, the electric pump 1 (1A, 1B) includes a casing 2, and a motor section 6 and a pump section 8 that are at least partially disposed within the casing 2. The casing 2 includes a front casing 2A and a rear casing 2B. The front casing 2A has a fluid inlet 3 and a fluid outlet 4. The casing 2 defines an interior space for at least partially 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 and rotates an impeller 22 of the pump unit 8. 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 the impeller 22 of the pump section 8 and is discharged from the fluid outlet 4. In the exemplary embodiment shown in FIGS. 1 and 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.

[0021] 1 and 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.

[0022] As described above, when focusing on the function of the electric pump 1 (1A, 1B), the components of the electric pump 1 (1A, 1B) 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, 1B) can also be classified into a plurality of elements from the viewpoint of physical components. The components of the electric pump 1 (1A, 1B) will be described below.

[0023] In some embodiments, as shown in Figures 1 and 3, the electric pump 1 (1A, 1B) 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.

[0024] 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. 1 and 3, in an 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.

[0025] 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 by the support shaft 10 via bearings 12, as shown in FIGS. 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.

[0026] 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.

[0027] In some embodiments, as shown in Figures 1 and 3, 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 the magnet 26 is positioned on the inner side of the stator 40 with the magnet 26 facing radially outward. A shaft insertion hole, which may be a through-hole extending in the axial direction, is formed in the rotor body 21, and this shaft insertion hole forms a hollow portion 25 of the rotor 20. The support shaft 10 is inserted into the hollow portion 25 (shaft insertion hole).

[0028] 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.

[0029] 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 .

[0030] 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.

[0031] In some embodiments, as shown in FIGS. 1 and 3, the rotor 20 has a neck 28 axially between the impeller 22 and the magnet 26 . The neck 28 refers to a portion of the rotor 20 that is constricted radially inward from the outer circumferential surfaces of the impeller 22 and the magnet 26. The neck 28 of the rotor 20 is formed by a recess 27 in the rotor body 21. The neck 28 of the rotor 20 formed by the recess 27 defines an annular cavity 29 on the back side of the impeller 22 that communicates with a gap 48 (described below) between the rotor 20 and the stator 40.

[0032] As shown in FIGS. 1 and 3, the rotor 20 has a shoulder 31 whose outer diameter is larger than that of the neck 28. The shoulder 31 is located on the opposite side of the impeller 22 in the axial direction across the neck 28. The shoulder 31 holds the magnet 26 on the outer circumferential surface side of the shoulder 31.

[0033] In some embodiments, as shown in FIGS. 1 and 3, the stator 40 is disposed on the outer circumferential side of the magnet 26 of the rotor 20 and 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.

[0034] 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. 1 and 3, the molding material 46 of the stator 40 also serves as the rear casing 2B. In other embodiments, the stator 40 is molded separately from the rear casing 2B, and the stator 40 is housed inside the rear casing 2B.

[0035] 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. The magnetic gap G extends in an annular shape along the axial direction of the impeller 22. Hereinafter, the region where the magnetic gap G is formed will be referred to as the magnetic gap G forming range (or magnetic gap forming range).

[0036] 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, an air gap 48 is formed between the magnets 26 and the molding material 46, as shown in Figures 1 and 3.

[0037] 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, gap 48 communicates with the pump chamber in which impeller 22 is provided via cavity 29, and some of the fluid flowing out from discharge port 22B of impeller 22 can reach gap 48 via cavity 29. For this reason, if gap 48 is made too narrow, there is a higher risk that foreign matter accompanying the fluid from impeller 22 will become caught in gap 48.

[0038] Therefore, in some embodiments, as shown in Figures 1 and 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.

[0039] 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. The bypass passage 60 is provided at a radial position inside the gap 48 on the back side of the impeller 22, and constitutes a part of the return passage 50. Here, "a radial position inside the gap 48" means a position between the gap 48 and the center of rotation of the impeller 22 in the radial direction.

[0040] The bypass passage 60, which constitutes a part of the return passage 50, is provided so as to bypass the gap 48 separating 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 and 3. Note that in Figures 1 and 3, the flow of 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.

[0041] In some embodiments, as shown in FIGS. 1-3, the bypass passage 60 comprises an internal flow passage 62 in the rotor 20 that opens into the cavity 29. A portion of the fluid that has passed through the impeller 22 flows around to the rear side of the impeller 22 and flows into the cavity 29 via the gap between the rear side of the impeller 22 and the stator 40 (mold material 46). In the cavity 29, which has a relatively large cross-sectional area of ​​the flow path, the flow velocity of the fluid that has flowed around to the rear side of the impeller 22 decreases and a stagnation portion is formed. Therefore, foreign matter accompanying the fluid flow that flows into the cavity 29 is easily captured in the stagnation portion formed in the cavity 29. Therefore, by using the internal flow path 62 that opens into the cavity 29 as the bypass path 60, foreign matter can be easily taken into the bypass path 60 (internal flow path 62), and the risk of foreign matter getting caught in the gap 48 can be effectively reduced.

[0042] In the exemplary embodiment shown in FIGS. 1-3, the internal flow passage 62 opens into the cavity 29 radially inward of the gap 48 . The fluid that flows around the back side of impeller 22 and into cavity 29 flows radially inward as shown by the solid arrows in Figures 1 to 3. Therefore, foreign matter accompanying the fluid flow also tries to move radially inward within cavity 29. Therefore, when the opening position of the internal flow passage 62 into the cavity 29 is radially inward of the gap 48, foreign matter attempting to move radially inward within the cavity 29 is more likely to be taken into the internal flow passage 62. Conversely, foreign matter attempting to move radially inward within the cavity 29 is less likely to enter the gap 48, which is located radially outward of the opening position of the internal flow passage 62.

[0043] 1, the internal flow passage 62 is a first through-hole 62A that passes through the neck 28 of the rotor 20 and connects the cavity 29 to the hollow portion 25. The first through-hole 62A is provided between the impeller 22 and the air gap 48 in the axial direction. The number of first through holes 62A is not particularly limited, and multiple first through holes 62A may be provided at different circumferential positions. In other embodiments, one first through hole 62A is provided at any circumferential position. Furthermore, the first through hole 62A may be a radial hole that passes through the neck 28 of the rotor 20, or may be an oblique hole that is provided obliquely relative to the radial direction.

[0044] 1, the support shaft 10 ends midway through the hollow portion 25 of the rotor 20. That is, the axial position of the tip of the support shaft 10 is within the range in which the hollow portion 25 is formed in the rotor 20. The opening of first through hole 62A to hollow portion 25 is open and not blocked by support shaft 10. In this case, it is sufficient that the opening of first through hole 62A is at least partially open, and part of the opening of first through hole 62A may be covered by support shaft 10. Cavity 29 communicates with a region of hollow portion 25 into which support shaft 10 is not inserted, via first through hole 62A that is at least partially open.

[0045] 1, in the region of hollow portion 25 where support shaft 10 is not inserted, the fluid taken in from cavity 29 flows in the axial direction toward suction port 22A of impeller 22. In other words, the region of hollow portion 25 where support shaft 10 is not inserted forms part of return flow path 50, is connected to the downstream end of first through hole 62A serving as bypass path 60, and guides the fluid that has passed through bypass path 60 to suction port 22A of impeller 22. Furthermore, not only the fluid that has passed through the bypass passage 60 but also the fluid that has passed through the gap 48 flows into the region of the hollow portion 25 where the support shaft 10 is not inserted. Specifically, as shown by the dashed arrow in FIG. 1 , the fluid that has passed through the gap 48 flows radially inward through the axial gap between the lower surface of the rotor 20 and the bottom surface of the rear casing 2B (mold material 46), then passes through the bearing gap of the bearing 12, and finally reaches the region of the hollow portion 25 where the support shaft 10 is not inserted. In this way, the circulation flows that have been divided into a flow toward the bypass passage 60 (first through hole 62A) and a flow toward the gap 48 in the cavity 29 join together in the region of the hollow portion 25 where the support shaft 10 is not inserted and are returned to the suction port 22A of the impeller 22.

[0046] 1, the opening position of the first through-hole 62A into the hollow portion 25 is located axially between the impeller 22 and the bearing 12. In other words, the bearing 12 is located on the opposite side of the opening position of the first through-hole 62A into the hollow portion 25 from the impeller 22 in the axial direction. Therefore, as described above, the fluid that has passed through the bypass path 60 merges with the fluid that has passed through the gap 48 and the bearing gap of the bearing 12 in the region of the hollow portion 25 where the support shaft 10 is not inserted. In this sense, the first through hole 62A serving as the bypass path 60 bypasses not only the gap 48 but also the bearing gap of the bearing 12. Therefore, by using the first through hole 62A as the bypass path 60 that bypasses the bearing gap of the bearing 12, not only the risk of foreign matter entering the gap 48 but also the risk of foreign matter entering the bearing gap of the bearing 12 can be reduced.

[0047] A throttle 15 may be provided to adjust the flow rate of the fluid passing through the area of ​​the hollow portion 25 where the support shaft 10 is not inserted. The orifice 15 may be an orifice plate provided in a region of the hollow portion 25 where the support shaft 10 is not inserted. In another embodiment, the orifice 15 is a gap between the rotor body portion 21 and a cap (not shown) attached to the rotor body portion 21 so as to close one end of the through hole (shaft insertion hole) in the rotor body portion 21 that defines the hollow portion 25 of the rotor 20, or an orifice hole provided in the cap.

[0048] 2A, the internal flow path 62 is a communication passage 62B having one end opening in the neck 28 of the rotor 20 and the other end opening in the pump chamber (the space on the suction port 22A side of the impeller 22). The communication passage 62B is provided on the impeller 22 side of the gap 48 in the axial direction. In the example shown in FIG. 2A, the communication passage 62B has a configuration in which a radial hole and an axial hole are connected, but the communication passage 62B may also be an oblique hole extending from one open end in the neck 28 to the other open end in the pump chamber so as to move radially inward toward the axial position of the fluid inlet 3. In the communication passage 62B that constitutes the bypass path 60, the fluid taken in from the cavity 29 flows toward the intake port 22A of the impeller 22. The flow of fluid returning from the cavity 29 to the intake port 22A of the impeller 22 via the communication passage 62B does not merge with the flow of fluid that has passed through the gap 48. After passing through the gap 48, the fluid flows radially inward through the axial gap between the lower surface of the rotor 20 and the bottom surface of the rear casing 2B (mold material 46), and then returns to the intake port 22A of the impeller 22 via the bearing gap of the bearing 12 and the gap between the outer peripheral surface of the support shaft 10 and the inner peripheral surface of the through-hole (shaft insertion hole) of the rotor main body 21 (see the dashed arrow in FIG. 2A ). In the embodiment shown in FIG. 2A, the support shaft 10 is inserted throughout the hollow portion 25 of the rotor 20.

[0049] 2B , the internal flow passage 62 is a through-hole 62C provided through the neck 28 so as to communicate with a groove 63 provided in the inner wall of the through-hole (shaft insertion hole) of the rotor main body 21. The through-hole 62C is provided between the impeller 22 and the gap 48 in the axial direction. The groove 63 may be formed in the outer peripheral surface of the support shaft 10. The through hole 62C constituting the bypass path 60 guides the fluid taken in from the cavity 29 to the groove 63. The upstream end of the groove 63 is connected to the through hole 62C, and the downstream end of the groove 63 is connected to the suction port 22A side of the impeller 22. Therefore, the fluid that has passed through the through hole 62C serving as the bypass path 60 is returned to the suction port 22A of the impeller 22 via the groove 63. The flow of the fluid that is returned to the suction port 22A of the impeller 22 from the cavity 29 via the through hole 62C and the groove 63 may merge with the flow of the fluid that has passed through the gap 48. In the exemplary embodiment shown in FIG. 2B, the fluid flow after passing through gap 48 flows radially inward through the axial gap between the lower surface of rotor 20 and the bottom surface of rear casing 2B (mold material 46), and then reaches groove 63 via the bearing gap of bearing 12 and the gap between the outer peripheral surface of support shaft 10 and the inner peripheral surface of the through hole (shaft insertion hole) of rotor main body 21 (see dashed arrow). In the embodiment shown in FIG. 2B, the support shaft 10 is inserted throughout the hollow portion 25 of the rotor 20.

[0050] 3, the rotor 20 has a second through hole 62D in the shoulder 31 as the internal flow path 62. The second through hole 62D is provided penetrating the shoulder 31 so as to pass through the radially inner side of the gap 48. The second through hole 62D extends inside the shoulder 31, passing through the extension range Y of the stator core 42 in the axial direction. One end of the second through hole 62D opens to an axial end surface of the shoulder 31 that faces the cavity 29. The other end of the second through hole 62D opens to an axial end surface (the lower surface of the rotor 20) on the opposite side of the shoulder 31. In the exemplary embodiment shown in FIG. 3 , the second through hole 62D may be an axial hole that penetrates the shoulder 31. In other embodiments, the second through hole 62D may be an oblique hole that extends obliquely with respect to the axial direction, for example, an oblique hole that extends obliquely with respect to the axial direction from one end of the second through hole 62D that opens to the cavity 29 toward the radially inner side. Furthermore, the number of second through holes 62D is not particularly limited, and multiple second through holes 62D may be provided at different circumferential positions.

[0051] The second through-hole 62D guides the fluid taken in from the cavity 29 to a portion of the return flow passage 50 downstream of the gap 48. Therefore, the fluid flowing through the second through-hole 62D is returned to the intake port 22A of the impeller 22 without passing through the gap 48. In other words, the second through-hole 62D functions as a bypass passage 60 that bypasses the gap 48. 3, one end of the second through hole 62D is connected to the cavity 29, and the other end of the second through hole 62D is fluidly connected to the gap between the lower surface of the rotor 20 and the bottom surface of the rear casing 2B (mold material 46). Therefore, in the gap between the lower surface of the rotor 20 and the bottom surface of the rear casing 2B (mold material 46), the fluid that has passed through the second through hole 62D merges with the fluid that has passed through the gap 48. The merged fluid passes through the bearing gap of the bearing 12 and is returned to the suction port 22A of the impeller 22. Thus, in the embodiment shown in Figure 3, the second through hole 62D passes radially inside the gap 48 and connects the cavity 29 to the downstream side of the gap 48 and the upstream side of the bearing gap between the bearing 12 and the support shaft 10.

[0052] 3 , the support shaft 10 has a hollow structure, and an axial flow passage 11 extending along the axial direction of the support shaft 10 so as to penetrate the support shaft 10 is formed inside the support shaft 10. The axial flow passage 11 communicates with an internal flow passage 62 (second through-hole 62D) of the rotor 20 via a gap between the rotor 20 and the rear casing 2B (mold material 46) and a communication hole 13 provided in the support shaft 10. In this case, the return flow passage 50 includes a second through hole 62D as the internal flow passage 62 and an axial flow passage 11 formed inside the support shaft 10.

[0053] 3, in the return flow passage 50, the fluid that has passed through the second through-hole 62D is divided into a flow toward the bearing gap between the bearing 12 and the support shaft 10 and a flow toward the axial flow passage 11 in the support shaft 10, and the two flows join together again just before the suction port 22A of the impeller 22. The axial flow passage 11 and the communication hole 13 of the support shaft 10 both have a flow passage width (flow passage diameter) that is larger than the bearing gap between the bearing 12 and the support shaft 10. In this case, foreign matter larger than the bearing gap between the bearing 12 and the support shaft 10 is returned to the intake port 22A of the impeller 22 through the communication hole 13 and the axial flow path 11. This makes it possible to prevent foreign matter from accumulating in the return flow path 50 and from getting caught in the bearing gap between the bearing 12 and the support shaft 10.

[0054] Next, the detailed structure of the electric pump 1 (1A, 1B) will be described with reference to FIGS. Fig. 4 is an axial cross-sectional view showing a specific example of the structure of an electric pump 1A according to one embodiment, and Fig. 5 is an axial cross-sectional view showing a specific example of the structure of an electric pump 1B according to another embodiment.

[0055] 4, the electric pump 1A includes a casing 2 having a front casing 2A and a rear casing 2B, and a pump unit 8 disposed within the casing 2. Of the motor unit 6 of the electric pump 1A, the stator 40 is provided integrally with the rear casing 2B, while the rotor 20 is disposed within the casing 2. The front casing 2A defines a pump chamber in which the impeller 22 is housed, and has a fluid inlet 3 and a fluid outlet 4 that communicate with the pump chamber. The front casing 2A forms a volute chamber 9 radially outward of the impeller 22.

[0056] 4 includes a support shaft 10, a rotor 20 including an impeller 22, a magnet 26, and a rotor main body 21, and a stator 40 including a stator core 42, a stator coil 44, and a molding material 46. The molding material 46 also serves as a rear casing 2B. The support shaft 10 is a stationary shaft that is fixed to the molding material 46 (rear casing 2B) 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 gap 48.

[0057] 4, a cylindrical magnet 26 is provided on the outer peripheral surface of the portion of rotor body 21 inserted into the recess of molding material 46 (shoulder 31 of rotor 20), facing an annular gap 48. Stator core 42 is disposed within molding material 46 radially outward from magnet 26, and a radial magnetic gap is formed between magnet 26 and stator core 42. Gap 48 is a gap between rotor 20 and stator 40 that exists within the magnetic gap formation range, and communicates with volute chamber 9 via cavity 29. A portion of the fluid that has passed through impeller 22 can reach gap 48 from volute chamber 9 via cavity 29. As shown by the dashed arrows in FIG. 4 , the fluid that has flowed into gap 48 flows into the non-insertion region of hollow portion 25 of rotor 20 where support shaft 10 is not inserted, via the gap between rotor main body 21 and molding material 46 (rear casing 2B) and the bearing gap between the outer circumferential surface of support shaft 10 and the inner circumferential surface of bearing 12.

[0058] On the other hand, an internal flow path 62 (first through hole 62A) of the rotor 20 that opens into the cavity 29 is provided in the neck 28 of the rotor 20 as a bypass path 60. The first through hole 62A opens into a region of the hollow portion 25 where the support shaft 10 is not inserted, and the cavity 29 communicates with the hollow portion 25 via the first through hole 62A. As shown by the solid arrow in Fig. 4, the fluid taken in from the cavity 29 into the first through-hole 62A (bypass path 60) merges with the fluid that has passed through the gap 48 and the bearing gap (the dashed arrow in Fig. 4) in the non-insertion region of the hollow portion 25 for the support shaft 10. The merged fluid is returned to the intake port 22A of the impeller 22 via the gap (the orifice 15) between the rotor body 21 and the cap 16 attached to the rotor body 21.

[0059] The electric pump 1B shown in FIG. 5 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 the impeller 22 is housed, and has a fluid inlet 3 and a fluid outlet 4 that communicate with the pump chamber. The front casing 2A forms a volute chamber 9 radially outward of the impeller 22.

[0060] The electric pump 1B 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 (rear casing 2B) 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 gap 48.

[0061] 5, a cylindrical magnet 26 is provided on the outer peripheral surface of the portion of rotor body 21 inserted into the recess of molding material 46 (shoulder 31 of rotor 20), facing an annular gap 48. Stator core 42 is disposed within molding material 46 radially outward from magnet 26, and a radial magnetic gap is formed between magnet 26 and stator core 42. Gap 48 is a gap between rotor 20 and stator 40 that exists within the magnetic gap formation range, and communicates with volute 9 via cavity 29. After passing through the impeller 22, a portion of the fluid can reach the gap 48 from the volute 9 via the cavity 29. The fluid that has flowed into the gap 48 flows through the gap between the rotor body 21 and the molding material 46, as indicated by the dashed arrow in FIG.

[0062] On the other hand, an internal flow path 62 (second through hole 62D) opening into the cavity 29 is provided in the shoulder 31 of the rotor 20 as a bypass path 60. The second through hole 62D has one end opening into the cavity 29 and the other end opening into the axial gap between the lower surface of the rotor 20 (shoulder 31) and the bottom surface of the molding material 46. The fluid taken into the second through-hole 62D (bypass path 60) from the cavity 29 merges with the fluid that has passed through the gap 48 (the dashed arrow in FIG. 4) in the axial gap between the lower surface of the rotor 20 (shoulder 31) and the bottom surface of the molding material 46, as shown by the solid arrow in FIG. 5. The merged fluid passes through the gap between the rotor 20 and the molding material 46, and is then divided into a flow that passes through the bearing gap between the bearing 12 and the support shaft 10, and a flow that passes through the communication hole 13 of the support shaft 10 and the axial flow path 11. These two flows merge again just before the suction port 22A of the impeller 22 in the gap (throttle 15) between the rotor body 21 and the cap 16 attached to the rotor body 21, and flow toward the suction port 22A of the impeller 22. Specifically, the flow that has passed through the bearing gap between the bearing 12 and the support shaft 10 passes through the annular gap between the outer circumferential surface of the support shaft 10 and the rotor main body 21, and is finally discharged from the gap (throttle 15) between the cap 16 and the rotor main body 21 to the suction port 22A side of the impeller 22. On the other hand, the flow that has passed through the communication hole 13 of the support shaft 10 and the axial flow path 11 turns back at the cavity on the tip side of the cap 16, passes through the gap between the cap 16 and the support shaft 10, and is finally discharged from the gap (throttle 15) between the cap 16 and the rotor main body 21 to the suction port 22A side of the impeller 22.

[0063] Although the electric pump 1 (1A, 1B) 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.

[0064] FIG. 6 is a diagram showing the structure of an electric pump 1 according to another embodiment. In some embodiments, the electric pump 1 has a board 100 for controlling the electric pump 1, as shown in Fig. 6. 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).

[0065] 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.

[0066] In some embodiments, the electric pump 1 has a partition wall portion 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 wall surface 122 of the partition wall portion 120 facing the rotor 20 forms an intermediate flow path 123 for guiding the fluid that has passed through the second through-hole 62D to the axial flow path 11 in the support shaft 10. In this way, by separating the intermediate flow path 123 and the substrate chamber 110 by the partition wall 120, it is possible to prevent the fluid from entering the substrate chamber 110 from the intermediate flow path 123 and prevent damage to the substrate 100 and the electronic component 102. In addition, the fluid flowing through the intermediate flow path 123 can promote heat dissipation from the substrate 100 and the electronic component 102.

[0067] 6, the partition wall 120 is formed by a portion of the rear casing 2B and a lid member 130 having a higher thermal conductivity than the rear casing 2B. The lid member 130 includes at least a portion of the portion of the rear casing 2B that faces the board 100. In the example shown in FIG. 6, the lid member 130 is arranged so that the entire lid member 130 is contained within the area in which the board 100 is arranged. In other embodiments, the lid member 130 extends beyond the area in which the board 100 is arranged. The lid member 130 is provided to close an opening 132 provided in 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 portion of the rear casing 2B where the opening 132 is located. The seal member 134 prevents fluid from entering the board chamber 110 from the intermediate flow path 123, with the aim of protecting the board 100 and electronic components 102.

[0068] 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. 6, 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.

[0069] 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 magnetic gap formation range, the circulating flow passing through the gap 48 can be reduced, thereby reducing the risk of foreign matter entering the gap 48. Furthermore, since the bypass path 60 is provided radially inward of the gap 48 and on the back side of the impeller 22, foreign matter that attempts to move radially inward due to the fluid flow that has circumvented the back side of the impeller can be easily taken into the bypass path 60. [2] In the cavity 29 defined by the neck 28 of the rotor 20, the fluid that has flowed around to the back side of the impeller 22 forms a stagnation area. If the internal flow path 62 that opens into this cavity 29 is used as a bypass path 60, foreign matter accompanying the fluid flow that has flowed around to the back side of the impeller 22 is captured in the stagnation area (cavity 29), making it easier for foreign matter to be taken into the bypass path 60.

[0070] 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]

[0071] 1: Electric pump 1A: Electric pump 1B: Electric pump 10: Support shaft 11: Axial flow passage 12: Bearing 13:Communication hole 20: Rotor 22: Impeller 22A: Inlet 22B:Discharge port 25: Hollow part 26: Magnet 28: Neck 29: Cavity 31: Shoulder 40: Stator 42: Stator core 48 :Void 50: Return flow path 60: Bypass road 62 (62A to 62D): Internal flow path 62A: First through hole 62D: 2nd through hole 100: Substrate 102: Electronic parts 110: Substrate room 120: Partition wall part 122: Wall 123: Intermediate flow path G: Magnetic gap

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 connects a discharge port of the impeller with a suction port of the impeller and returns the fluid that has passed through the impeller to the suction port of the impeller; Equipped with The return flow passage includes a bypass passage provided on a rear surface side of the impeller at a radial position inside the gap so as to bypass the gap separating the rotor and the stator. Electric pump.

2. the rotor has a neck between the impeller and the magnet in the axial direction, the neck being constricted radially inward from an outer circumferential surface of the impeller and an outer circumferential surface of the magnet, the neck defines a cavity on the rear side of the impeller that communicates with the gap; The bypass passage includes an internal passage formed in the rotor so as to open into the cavity. The electric pump according to claim 1 .

3. The rotor is a hollow portion into which the support shaft is inserted; a first through hole that passes through the neck and connects the cavity to the hollow portion; Including, The bypass path includes the first through hole as the internal flow path. The electric pump according to claim 2.

4. The support shaft is terminated midway through the hollow portion so that the opening of the first through hole into the hollow portion is at least partially open. The electric pump according to claim 3.

5. a bearing for rotatably supporting the rotor on the support shaft, the bearing being located on the opposite side of the impeller in the axial direction across the opening position of the first through hole into the hollow portion; The electric pump according to claim 3 or 4.

6. The rotor is a shoulder having an outer diameter larger than that of the neck, positioned on the opposite side of the impeller in the axial direction across the neck, and holding the magnet on the outer periphery; a second through hole passing through the shoulder so as to pass radially inside the gap; Including, The bypass path includes the second through hole as the internal flow path. The electric pump according to claim 2.

7. a bearing for rotatably supporting the rotor on the support shaft; The second through hole passes through the radially inner side of the gap and communicates the cavity with the downstream side of the gap and the upstream side of a bearing gap between the bearing and the support shaft. The electric pump according to claim 6.

8. the support shaft has an axial flow passage extending along the axial direction of the support shaft so as to penetrate the support shaft, The return flow path is The second through hole; the axial flow passage of the support shaft communicating with the second through hole; Contains The electric pump according to claim 6 or 7.

9. 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 wall surface of the partition wall facing the rotor forms an intermediate flow passage for guiding the fluid that has passed through the second through hole to the axial flow passage. The electric pump according to claim 8.

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