Electric water pump

Abstract

In this electric water pump, a front-stage impeller has an upper surface and a bottom surface, main blades are provided on the upper surface, and a plurality of arc-shaped groove parts are formed at intervals on the bottom surface along a circumference coaxial with a support shaft. A rear-stage impeller includes a cylindrical part into which the support shaft is inserted, and an umbrella part that is integrally formed on the outer periphery of the cylindrical part and that has the main blades provided on an upper surface. A plurality of arc-shaped claw parts capable of fitting into the groove parts are formed with gaps in between at the tip of the cylindrical part extending from the upper surface side of the umbrella part, and the two impellers are integrally rotatably connected by fitting the plurality of claw parts into the plurality of groove parts.

Description

Electric water pump

[0001] The technology disclosed in this specification relates to an electric water pump used in cooling circuits and the like.

[0002] Conventionally, as this type of technology, for example, the "two-stage centrifugal pump" described in Patent Document 1 below is known. This two-stage centrifugal pump includes a pump case, a rotor shaft rotationally driven by a drive source, two axially adjacent impellers held by the rotor shaft, a partition wall that divides a space in the pump case, and a guide vane member arranged on a front surface of the partition wall. The partition wall has a circular hole through which the rotor shaft is inserted. The pump case has two pump chambers partitioned by the partition wall. Each impeller is accommodated in each pump chamber, respectively. The partition wall and the guide vane member are arranged between the two adjacent stages of impellers.

[0003] Japanese Unexamined Patent Publication No. 2022-30980

[0004] By the way, in the two-stage centrifugal pump described in Patent Document 1, two axially adjacent stages of impellers are each held on the rotor shaft. Therefore, a process of assembling each of the two stages of impellers to the rotor shaft is required, and a reduction in assembly man-hours is desired.

[0005] The disclosed technology has been made in view of the above circumstances, and an object thereof is to provide an electric water pump that enables a reduction in man-hours for assembling two stages of impellers so as to be integrally rotatable.

[0006] To achieve the above objective, the technology described in claim 1 is an electric water pump comprising a housing, a two-stage impeller housed in the housing that rotates around a pivot shaft by obtaining rotational driving force and pressurizes fluid flowing in from the upstream side in the axial direction to the radially outward direction, wherein the two-stage impeller includes an impeller on the front side and an impeller on the rear side, the impeller on the front side having an upper surface and a bottom surface, the upper surface having main blades, and the bottom surface having a plurality of arc-shaped grooves formed at intervals on a circumference coaxial with the pivot shaft, the impeller on the rear side including a cylindrical part through which the pivot shaft is inserted, and an umbrella part integrally formed on the outer circumference of the cylindrical part and having main blades on its upper surface, the tip of the cylindrical part extending from the side of the upper surface of the umbrella part having a plurality of arc-shaped claws that can be fitted into the grooves with gaps between them, and the two-stage impeller is connected so as to be able to rotate together by fitting the plurality of claws into the plurality of grooves.

[0007] According to the above-described technology, the two impellers are connected by fitting multiple claws formed at the tip of the cylindrical portion of the downstream impeller into multiple grooves formed on the bottom surface of the upstream impeller. The two impellers are then supported so that they can rotate together by inserting a support shaft through the cylindrical portion.

[0008] To achieve the above objective, the technology described in claim 2 is the technology described in claim 1, wherein a stepped surface is formed on the inner circumference of the cylindrical portion of the downstream impeller, which contacts the bottom surface of the upstream impeller when the multiple claw portions are fitted into the multiple groove portions, the stepped surface has a first depth in the axial direction from the tip surface of the cylindrical portion, and the multiple gaps in the cylindrical portion have a second depth in the axial direction from the tip surface of the cylindrical portion, the second depth being greater than the first depth.

[0009] According to the configuration of the above technology, in addition to the operation of the technology described in claim 1, the multiple claws of the cylindrical portion of the downstream impeller are fitted into the multiple grooves on the bottom surface of the upstream impeller, so that the bottom surface of the upstream impeller contacts and is positioned against the stepped surface on the inner circumference of the cylindrical portion. In this state, the second depth of the gap in the cylindrical portion is greater than the first depth of the stepped surface of the cylindrical portion. Therefore, the position in the gap of the cylindrical portion where the bottom surface of the upstream impeller engages is shallower than the bottom of the gap. Now, suppose that when the two-stage impeller is rotating, the rotation of the upstream impeller locks up due to foreign matter getting caught or the like. At this time, the downstream impeller will continue to rotate, so an excessive rotational load is applied to the portion where the claws of the cylindrical portion of the downstream impeller engage with the grooves on the bottom surface of the upstream impeller. In particular, an excessive rotational load is applied to the inner wall on the opposite side of the rotation direction in the gap between the multiple claws where the portions between the multiple grooves engage. However, in the above configuration, the position of the bottom surface of the impeller on the front side is at a step that is shallower than the bottom of the gap, so the rotational load does not directly act on the bottom of the gap.

[0010] To achieve the above objective, the technology described in claim 3 relates to the electric water pump described in claim 2, wherein the gap has a bottom in the direction of the second depth, and the bottom has corners having an asymmetrical curved shape in the width direction perpendicular to the direction of the second depth, and the curvature of one of the asymmetrical corners, which is on the opposite side of the rotation direction of the impeller, is greater than the curvature of the other asymmetrical corner.

[0011] According to the configuration of the above technology, in addition to the effects of the technology described in claim 2, the bottom of the gap in the cylindrical portion has corners that are curved in an asymmetrical shape in the width direction. The curvature of one of the asymmetrical corners, which is on the opposite side of the impeller's rotation direction, is greater than the curvature of the other asymmetrical corner. Therefore, even if a rotational load is applied to the corner at the bottom of the gap in the cylindrical portion, which is on the opposite side of the impeller's rotation direction, the load is easily distributed due to the curved shape of that corner with its large curvature.

[0012] To achieve the above objective, the technology described in claim 4 is intended to be the technology described in any one of claims 1 to 3, wherein the electric water pump is provided in the cooling system of the electric vehicle.

[0013] According to the configuration of the above technology, an electric water pump provided in the cooling system of an electric vehicle can achieve the same effect as the technology described in any one of claims 1 to 3.

[0014] According to the technology described in claim 1, the two-stage impeller can be assembled integrally to the support shaft without having to assemble them separately, thereby reducing the assembly time.

[0015] According to the technology described in claim 2, in addition to the effects of the technology described in claim 1, it is possible to suppress the direct application of excessive rotational load to the bottom of the gap.

[0016] According to the technology described in claim 3, in addition to the effects of the technology described in claim 2, the durability strength of the corners of the gap can be improved.

[0017] According to the technology described in claim 4, an electric water pump provided in the cooling system of an electric vehicle can obtain the same effects as the technology described in any one of claims 1 to 3.

[0018] A front view showing the electric water pump according to the first embodiment. A cross-sectional view showing the electric water pump according to the first embodiment. A cross-sectional view showing an enlarged portion of Figure 2 (the pump section described later) according to the first embodiment. A cross-sectional view showing the first impeller, the partition plate, and the second impeller supported by the support shaft in a disassembled state according to the first embodiment. A view along line A-A in Figure 4 showing the bottom surface of the first impeller according to the first embodiment. A view along line B-B in Figure 4 showing the top surface of the second impeller including the second cover according to the first embodiment. A perspective view showing the top side of the second impeller with the second cover removed, together with the upper cylindrical portion, according to the first embodiment. A cross-sectional view showing an enlarged portion of the area enclosed by the dashed-dotted circle in Figure 3 according to the first embodiment. A cross-sectional view along line C-C in Figure 8 showing the connection portion between the upper cylindrical portion of the second impeller and the first impeller according to the first embodiment. A circuit diagram showing an example of the use of an electric water pump according to the first embodiment. A perspective view similar to Figure 7 showing the upper side of the second impeller according to the second embodiment.

[0019] The following describes an embodiment in which an electric water pump is incorporated into the cooling system of an electric vehicle.

[0020] <First Embodiment> First, the first embodiment will be described in detail with reference to Figures 1 to 8.

[0021] [Basic Configuration of the Electric Water Pump] Figure 1 shows a front view of the electric water pump 1 of this embodiment. Figure 2 shows a cross-sectional view of the electric water pump 1. Figure 3 shows an enlarged cross-sectional view of a part of Figure 2 (the pump section 3, which will be described later).

[0022] This electric water pump 1 is installed, for example, in a cooling system (described later) mounted on an electric vehicle and is used to circulate cooling water as a fluid. As shown in Figures 1 to 3, the electric water pump 1 comprises a cylindrical housing 2 made of resin. The electric water pump 1 comprises a pump section 3 and a motor section 4. The housing 2 includes an upper housing 2A, a body 2B, and a lower housing 2C.

[0023] As shown in Figures 1 to 3, the upper housing 2A is roughly dish-shaped and has a flange 2Ab on its outer circumference. The body 2B is roughly cylindrical and has an upper flange 2Bc at its upper end and a lower flange 2Bd at its lower end. The lower housing 2C is roughly dish-shaped and has a flange 2Ca on its outer circumference. The upper ends of the upper housing 2A and the body 2B are connected via flange 2Ab and upper flange 2Bc. The lower ends of the lower housing 2C and the body 2B are connected via flange 2Ca and lower flange 2Bd.

[0024] [About the pump section] As shown in Figures 1 to 3, the pump section 3 is provided in the upper housing 2A and a part of the body 2B. The upper housing 2A is provided with a cooling water intake passage 11 that protrudes upward. The upper housing 2A and the body 2B are provided with a pump chamber 12. The pump chamber 12 is positioned in the middle and is divided into a first pump chamber 12A and a second pump chamber 12B by a resin partition plate 13 that is formed separately from the body 2B. A resin first impeller 14 is placed in the first pump chamber 12A. A resin second impeller 15 is placed in the second pump chamber 12B. In this embodiment, the first impeller 14 and the second impeller 15 are connected so as to be rotatable as a single unit. In this embodiment, each impeller 14, 15 rotates clockwise when viewed from above in Figure 2, that is, from the side of the intake passage 11 (hereinafter defined as the "upstream side").

[0025] As shown in Figures 2 and 3, multiple main blades 14a are formed in a curved, vortex-like shape at regular intervals on the upstream side of the first impeller 14. A resin first cover 16 is attached to the upstream side of the first impeller 14 so as to cover these main blades 14a. The first cover 16 is a component of the first impeller 14 and rotates integrally with the first impeller 14. An upstream gap 17 is provided between the first cover 16, which is located on the upstream side of the first impeller 14, and the inner wall 2Aa of the upper housing 2A facing it, allowing cooling water to flow through. A central hole 16a is formed in the center of the first cover 16 through which a support shaft 30, which will be described later, passes.

[0026] As shown in Figures 2 and 3, multiple main blades 15a are formed at regular intervals in a curved, vortex-like shape on the upstream side of the second impeller 15. A second resin cover 18 is attached to the upstream side of the second impeller 15 so as to cover these main blades 15a. The second cover 18 is a component of the second impeller 15 and rotates integrally with the second impeller 15. An upstream gap 19 is provided between the second cover 18, which is located on the upstream side of the second impeller 15, and the lower surface 13a of the partition plate 13 facing it, allowing cooling water to flow through. A central hole 18a is also formed in the center of the second cover 18, through which a support shaft 30, described later, passes.

[0027] As shown in Figures 2 and 3, multiple blades 13b are formed in a vortex streamline pattern at regular intervals on the upstream side of the partition plate 13. The main blades 14a and 15a of each impeller 14 and 15 and the blades 13b of the partition plate 13 are curved in the same vortex direction. A central hole 13c is also formed in the center of the partition plate 13, through which the support shaft 30, described later, passes.

[0028] A series of pump passages are formed in the upper housing 2A and the body 2B. The pump passages include an upstream gap 17 between the first cover 16 and the upper housing 2A, a central hole 16a of the first cover 16, a gap between the outer circumference of the first impeller 14 and the inner circumference of the upper housing 2A, a gap between the first impeller 14 and the partition plate 13, a central hole 13c of the partition plate 13, an upstream gap 19 between the second cover 18 and the lower surface 13a of the partition plate 13, a central hole 18a of the second cover 18, a gap between the outer circumference of the second impeller 15 and the inner circumference of the body 2B, and a gap between the lower surface of the second impeller 15 and the body 2B. One end of the pump passage leads to the suction passage 11, and the other end of the passage leads to the discharge passage 20 provided in the body 2B.

[0029] The two impellers 14 and 15 of the pump section 3 described above are configured to rotate around the support shaft 30 by obtaining rotational driving force from the motor section 4, and to pressurize the cooling water flowing in from the upstream side in the axial direction SD (see Figure 2) to the outside in the radial direction RD (see Figure 2).

[0030] The partition plate 13 positioned between the two impellers 14 and 15 has a return flow path RP (shown by a thick arrow in Figure 3) that guides the cooling water pumped by the first impeller 14 on the front side toward the inside in the radial direction RD (see Figure 2), and an introduction flow path IP (shown by a thick arrow in Figure 3) connected downstream of the return flow path RP that redirects and introduces the cooling water to the second impeller 15 on the rear side.

[0031] [About the motor section] As shown in Figure 2, the motor section 4 is located below the pump section 3, between the body 2B and the lower housing 2C. The motor section 4 is composed of a brushless motor. The motor section 4 comprises a support shaft 30, a rotor 31, and a stator 32.

[0032] The metal support shaft 30 extends axially SD from the center of the upper housing 2A and the body 2B. The upper end of the support shaft 30 is fixed to an upper bearing 41 located above the first impeller 14. The lower end of the support shaft 30 is fixed to a lower bearing 42 located at the bottom of the body 2B. A rotating body 33, which is integrally formed by the impellers 14, 15, the covers 16, 18 and the rotor 31, is rotatably supported on the support shaft 30. The rotating body 33 is positioned to cover most of the outer circumference of the support shaft 30. An axial gap 34 is formed between the inner circumference of the rotating body 33 and the outer circumference of the support shaft 30. This axial gap 34 leads to the pump section passage described above and the motor section passage described later.

[0033] The rotor 31 is cylindrical and housed in the body 2B. The rotor 31 is positioned below the second impeller 15 at a distance and is provided to be integral with the second impeller 15. The rotor 31 is arranged in series with each impeller 14, 15 in the axial direction SD. The upper end surface 31a of the rotor 31 is positioned facing the second impeller 15. The rotor 31 and each impeller 14, 15 are rotatable about the axis of the support shaft 30. The rotor 31 includes a cylindrical permanent magnet 43 provided on its outer circumference. This permanent magnet 43 has multiple magnetic poles in the circumferential direction.

[0034] Body 2B has an inner circumferential surface 2Ba and a bottom surface 2Bb. The inner circumferential surface 2Ba faces the outer circumference of the rotor 31 and surrounds the rotor 31. The bottom surface 2Bb faces the lower end surface 31b of the rotor 31. A rotor gap 35 is formed between the inner circumferential surface 2Ba of body 2B and the outer circumference of the rotor 31. On the other hand, a bottom gap 36 is formed between the bottom surface 2Bb of body 2B and the lower end surface 31b of the rotor 31. The motor section passage includes the rotor gap 35 and the bottom gap 36 described above.

[0035] The stator 32 is housed in the body 2B on the outer circumference side of the rotor 31. The stator 32 includes a metal core 51. The core 51 is formed by stacking a plurality of core plates. Coil wire 52 is wound around the core 51.

[0036] A control circuit 55 that controls the power supply to the stator 32 is provided inside the lower housing 2C. The control circuit 55 is connected to an external power supply via terminals (not shown). The control circuit 55 is configured to supply power from the external power supply to the motor unit 4.

[0037] [Technical Features of This Embodiment] In the basic configuration of the electric water pump 1 described above, the first impeller 14 and the second impeller 15 are connected so as to be able to rotate together. In this embodiment, the configuration relating to this connection will be described below.

[0038] Figure 4 shows a disassembled cross-sectional view of the first impeller 14, the partition plate 13, and the second impeller 15 supported by the support shaft 30. Figure 5 shows the bottom surface of the first impeller 14 as viewed along line A-A in Figure 4. Figure 6 shows the top surface of the second impeller 15, including the second cover 18, as viewed along line B-B in Figure 4. Figure 4 shows the first impeller 14 with the first cover 16 attached. It also shows the second impeller 15 with the second cover 18 attached.

[0039] As shown in Figures 4 to 6, the second impeller 15 on the downstream side includes a cylindrical portion 15b that extends axially from its center and through which the support shaft 30 is inserted, and an umbrella portion 15c that is integrally formed on the outer circumference of the cylindrical portion 15b and has main blades 15a on its upper surface. The cylindrical portion 15b includes an upper cylindrical portion 15ba above the umbrella portion 15c and a lower cylindrical portion 15bb below the umbrella portion 15c. The cylindrical portion 15b is rotatably supported with respect to the support shaft 30.

[0040] As shown in Figure 5, the first impeller 14 on the front side is disc-shaped and has an upper surface 14f and a bottom surface 14b. The main blades 14a are provided on the upper surface 14f. An engagement hole 14c is formed on the bottom surface 14b through which the tip of the support shaft 30 penetrates and engages. In addition, multiple (three in this embodiment) arc-shaped grooves 14d are formed on the circumference of the bottom surface 14b at intervals IV, coaxial with the engagement hole 14c. That is, the multiple grooves 14d are arranged on the circumference at equal angular intervals via a partition 14e.

[0041] FIG. 7 is a perspective view showing the upper surface side of the second impeller 15 with the second cover 18 removed, together with the upper cylindrical portion 15ba.

[0042] As shown in FIGS. 6 and 7, a plurality (three in this embodiment) of arc-shaped claw portions 15bc that can be fitted into the groove portions 14d of the first impeller 14 are formed at the tip of the upper cylindrical portion 15ba of the second impeller 15 on the rear stage side via gaps 15bd.

[0043] FIG. 8 is an enlarged cross-sectional view showing a portion surrounded by an alternate long and short dash line circle S1 in FIG. 3. FIG. 9 is a cross-sectional view taken along line C-C of FIG. 8 showing a connection portion between the upper cylindrical portion 15ba of the second impeller 15 and the first impeller 14. As shown in FIGS. 8 and 9, the claw portions 15bc of the upper cylindrical portion 15ba are fitted into the plurality of groove portions 14d of the first impeller 14, whereby the two-stage impellers 14 and 15 are connected so as to be rotatable integrally.

[0044] In this embodiment, as shown in FIG. 7, a step surface 15be that abuts against the bottom surface 14b of the first impeller 14 when the plurality of claw portions 15bc are fitted into the plurality of groove portions 14d is formed on the inner circumference of the upper cylindrical portion 15ba of the second impeller 15. The step surface 15be has a first depth D1 in the axial direction from the tip of the upper cylindrical portion 15ba. The plurality of gaps 15bd of the upper cylindrical portion 15ba have a second depth D2 in the axial direction from the tip of the upper cylindrical portion 15ba. And the second depth D2 is larger than the first depth D1. In this embodiment, the second depth D2 is about twice the first depth D1.

[0045] As shown in FIG. 9, the gap 15bd of the upper cylindrical portion 15ba has a bottom portion B1 in the direction of the second depth D2. The bottom portion B1 has left-right asymmetric curved corners C1 and C2 in the width direction orthogonal to the depth direction. The curvature of the first corner C1 (on the right side in FIG. 9), which is one of the asymmetric corners and located on the opposite side to the rotation direction XD of both impellers 14 and 15, is larger than the curvature of the other asymmetric second corner C2 (on the left side in FIG. 9).[Example of Electric Water Pump Use] Figure 10 shows an example of the use of the electric water pump 1 described above in a circuit diagram. As shown in Figure 8, in this embodiment, the electric water pump 1 is used as a first electric water pump 97 and a second electric water pump 98 in a cooling system 91 mounted on an electric vehicle 90. The cooling system 91 corresponds to an example of the "cooling system" of this disclosed technology. In addition to the two electric water pumps 97 and 98, the cooling system 91 includes a radiator 92, a PCU 93, a battery 94, and a chiller 95. The first pipe 96A is connected to the radiator 92. The second pipe 96B is connected to the CPU 93. The third pipe 96C is connected to the battery 94. The fourth pipe 96D is connected to the chiller 95. In addition to the PCU 93, the first electric water pump 97 is provided on the second pipe 96B. In addition to the chiller 95, the fourth pipe 96D is equipped with a second electric water pump 98. Both ends of the first pipe 96A are connected to the sixth inlet / outlet passage 99F and the second inlet / outlet passage 99B of the flow path switching device 100. Both ends of the second pipe 96B are connected to the seventh inlet / outlet passage 99G and the third inlet / outlet passage 99C of the flow path switching device 100. Both ends of the third pipe 96C are connected to the fourth inlet / outlet passage 99D and the eighth inlet / outlet passage 99H of the flow path switching device 100. Both ends of the fourth pipe 96D are connected to the first inlet / outlet passage 99A and the fifth inlet / outlet passage 99E of the flow path switching device 100. Then, by operating each of the electric water pumps 97 and 98 and driving the flow path switching device 100, the flow of cooling water to each part 92 to 95 is controlled by switching its flow path.

[0046] [Operation and Effects of the Electric Water Pump] According to the configuration of the electric water pump 1 of this embodiment described above, the two stages of impellers 14 and 15 are connected by fitting the multiple claw portions 15bc formed at the tip of the upper cylindrical portion 15ba of the second impeller 15 on the downstream side into the multiple groove portions 14d formed on the bottom surface 14b of the first impeller 14 on the upstream side. Then, by inserting the support shaft 30 through the upper cylindrical portion 15ba, the two stages of impellers 14 and 15 are supported so that they can rotate together as a single unit. For this reason, the two stages of impellers 14 and 15 can be assembled together without separately assembling them to the support shaft 30, and the assembly man-hours can be reduced.

[0047] Furthermore, according to the configuration of this embodiment, the plurality of claw portions 15bc of the upper cylindrical portion 15ba of the second impeller 15 are fitted into the plurality of groove portions 14d of the bottom surface 14b of the first impeller 14. Accordingly, the bottom surface 14b of the first impeller 14 abuts against the step surface 15be on the inner circumference of the upper cylindrical portion 15ba and is positioned. In this state, the second depth D2 of the gap 15bd of the upper cylindrical portion 15ba is larger than the first depth D1 of the step surface 15be of the upper cylindrical portion 15ba. Therefore, the position where a part of the bottom surface 14b of the first impeller 14 engages in the gap 15bd of the upper cylindrical portion 15ba is a position shallower than the bottom B1 of the gap 15bd. Here, it is assumed that when the two-stage impellers 14 and 15 are rotationally driven, the rotation of the first impeller 14 is locked due to reasons such as foreign matter biting. At this time, the second impeller 15 tends to continue rotating, so an excessive rotational load is applied to the portion where the claw portion 15bc of the upper cylindrical portion 15ba is fitted into the groove portion 14d of the bottom surface 14b of the first impeller 14. In particular, an excessive rotational load is applied to the inner wall on the opposite side in the rotational direction in the gap 15bd between the plurality of claw portions 15bc, with which the portion between the plurality of groove portions 14d engages. However, in the above configuration, the position of the bottom surface 14b of the first impeller 14 is at the position of the step surface 15be which is shallower than the bottom B1 of the gap 15bd, so the rotational load does not directly act on the bottom B1 of the gap 15bd. Therefore, direct application of an excessive rotational load to the bottom B1 of the gap 15bd can be suppressed.

[0048] Furthermore, according to the configuration of this embodiment, as shown in FIG. 9, the bottom B1 of the gap 15bd of the upper cylindrical portion 15ba has corners C1 and C2 having a bilaterally asymmetric curved shape in the width direction. The curvature of the corner C1 on one asymmetric side and on the rotational direction side of the impellers 14 and 15 is larger than the curvature of the other asymmetric corner C2. Therefore, even if a rotational load is applied to the first corner C1 on the opposite side to the rotational direction XD of the impellers 14 and 15 at the bottom B1 of the gap 15bd of the upper cylindrical portion 15ba, the curved shape with a large curvature of the corner C1 facilitates load dispersion. Therefore, the durability strength of the corner C1 of the gap 15bd can be improved.

[0049] According to the configuration of this embodiment, the above-described functions and effects can be obtained for the electric water pumps 97 and 98 used in the cooling system 91 of the electric vehicle 90.

[0050] <Second Embodiment> The second embodiment will be described in detail with reference to Figure 11. In the following description, components equivalent to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted, with the focus being on the differences.

[0051] [Technical Features of This Embodiment] This embodiment differs from the first embodiment in the following technical features. Figure 11 shows the upper side of the second impeller 15 in this embodiment, in a perspective view similar to that of Figure 7.

[0052] As shown in Figure 11, this embodiment differs from the first embodiment mainly in the configuration of the gap 15bd between the multiple claw portions 15bc provided at the upper end of the upper cylindrical portion 15ba of the second impeller 15. As shown in Figure 11, in this embodiment, the second depth D2 of the gap 15bd is the same as the first depth D1 of the stepped surface 15be of the upper cylindrical portion 15ba. That is, the bottom of the gap 15bd is flush with the stepped surface 15be. The left and right corners of the bottom of the gap 15bd are right-angled and symmetrical.

[0053] [Operation and Effects of the Electric Water Pump] According to the configuration of the electric water pump 1 of this embodiment described above, the two stages of impellers 14 and 15 are connected by fitting the multiple claw portions 15bc formed at the tip of the upper cylindrical portion 15ba of the second impeller 15 on the downstream side into the multiple groove portions 14d formed on the bottom surface 14b of the first impeller 14 on the upstream side. Then, by inserting the support shaft 30 through the upper cylindrical portion 15ba, the two stages of impellers 14 and 15 are supported so that they can rotate together as a single unit. For this reason, the two stages of impellers 14 and 15 can be assembled together without separately assembling them to the support shaft 30, and the assembly man-hours can be reduced.

[0054] <Another Embodiment> It should be noted that this disclosed technology is not limited to the embodiments described above, and it may be implemented by appropriately modifying some of the components without departing from the spirit of the disclosed technology.

[0055] In each of the above embodiments, the electric water pump 1 was embodied as electric water pumps 97 and 98 used in the cooling system of the electric vehicle 90, but the invention is not limited thereto.

[0056] This disclosed technology can be used, for example, in an electric water pump used in the cooling system of an electric vehicle.

[0057] 1 Electric water pump 2 Housing 14 First impeller 14a Main blade 14b Bottom surface 14d Groove 14f Top surface 15 Second impeller 15a Main blade 15b Cylindrical section 15bc Claw section 15bd Gap 15be Stepped surface 15c Umbrella section 15d Top surface 30 Support shaft 90 Electric vehicle 91 Cooling system (cooling system) IV Spacing D1 First depth D2 Second depth B1 Bottom C1 First corner C2 Second corner RD Radial direction SD Axial direction XD Rotational direction

Claims

1. An electric water pump comprising: a housing; a two-stage impeller housed in the housing, which rotates around a pivot shaft by obtaining rotational driving force and pressurizes fluid flowing in from the upstream side in the axial direction to the radially outward direction; the two-stage impeller comprising an impeller on the front side and an impeller on the rear side, wherein the impeller on the front side has an upper surface and a bottom surface, the upper surface is provided with main blades, and the bottom surface has a plurality of arc-shaped grooves formed at intervals on a circumference coaxial with the pivot shaft; the impeller on the rear side comprises a cylindrical portion through which the pivot shaft is inserted, and an umbrella portion integrally formed on the outer circumference of the cylindrical portion and having main blades on its upper surface; a plurality of arc-shaped claw portions that can be fitted into the grooves are formed at the tip of the cylindrical portion extending from the upper surface side of the umbrella portion with gaps between them, and the two-stage impeller is connected so as to be able to rotate as a whole by fitting the plurality of claw portions into the plurality of grooves.

2. An electric water pump according to claim 1, wherein a stepped surface is formed on the inner circumference of the cylindrical portion of the downstream impeller, such that when a plurality of the claw portions are fitted into a plurality of groove portions, it abuts against the bottom surface of the upstream impeller, the stepped surface has a first depth in the axial direction from the tip surface of the cylindrical portion, and the plurality of gaps in the cylindrical portion have a second depth in the axial direction from the tip surface of the cylindrical portion, the second depth being greater than the first depth.

3. An electric water pump according to claim 2, wherein the gap has a bottom in the direction of the second depth, and the bottom has corners having an asymmetrical curved shape in the width direction perpendicular to the direction of the second depth, and the curvature of one of the asymmetrical corners on the side opposite to the direction of rotation of the impeller is greater than the curvature of the other asymmetrical corner.

4. An electric water pump according to any one of claims 1 to 3, characterized in that the electric water pump is provided in the cooling system of an electric vehicle.

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