Electric pump

Abstract

To provide an electric pump that is made lightweight and can suppress deterioration in pump efficiency even when the temperature changes.SOLUTION: An electric pump 1 comprises: a motor 2 having a resin motor case 5 that accommodates a stator 3 and a rotor 4 and has a plurality of projections 5c rising from a bottom 5b; a driven part D connected to the motor 2; a cylindrical part 12a that abuts on the bottom 5b of the motor case 5 in an axial direction and rotatably accommodates the driven part D; a cover 12d that closes the side of the cylindrical part 12a opposite to the motor case; and an opposing part 12c that is separated from and opposed to the projections 5c in the axial direction. The axial lengths of the driven part D and the cylindrical part 12a are equal to each other, and the driven part D and the cylindrical part 12a have a linear expansion coefficient of 10×10-6 / K to 25×10-6 / K inclusive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, electric pumps are mounted on vehicles and used, for example, to supply pressurized oil necessary for the operation of the vehicle's transmission, etc. Such electric pumps are configured with a cylindrical motor case, a motor including an armature fixed to the inner periphery of the motor case, and a rotor held in the motor case via a ball bearing and having a permanent magnet on its outer periphery facing the armature, and a gear pump fixed to one end of the motor case.

[0003] The gear pump includes a cylindrical pump housing integral with the motor case, a cover closing one end of the pump housing, an annular outer rotor rotatably housed within the pump housing and having a plurality of internal teeth on its inner periphery, and a disk-shaped inner rotor rotatably housed within the pump housing and having external teeth on its outer periphery that mesh with the internal teeth of the outer rotor. The inner rotor of the gear pump is connected to the rotor of the motor, and when driven by the motor, it is rotated together with the outer rotor within the pump housing. An electric pump configured in this manner can continuously supply hydraulic oil to a transmission by driving the gear pump when current is applied to the motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-127918 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electric pump configured as described above, the motor case that houses the stator and rotor and the pump housing that houses the inner rotor and outer rotor are integrated, and the case that houses the electric pump parts has a two-piece structure consisting of the motor case and the cover, which is advantageous in that it has a simple structure.

[0006] However, conventional electric pumps have a problem of being heavy because their motor cases and covers are made of metal. One possible way to reduce the weight of conventional electric pumps is to use a resin motor case with a pump housing. However, simply using a resin motor case results in a difference in linear expansion coefficient between the metal inner and outer rotors and the synthetic resin pump housing. As a result, as temperatures rise, the gaps between the inner and outer rotors and the cover increase, reducing the pump's efficiency. Therefore, reducing the weight of conventional electric pumps results in a problem of reduced pump efficiency when used in environments with extreme temperature changes.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an electric pump that is lightweight and can suppress deterioration in pump efficiency even when the temperature changes. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the motor of the present invention is provided with a motor having a stator, a rotor rotatable relative to the stator, and a resin motor case that is cylindrical with a bottom and houses the stator and rotor therein and has a plurality of protrusions rising from the bottom toward the side opposite the stator; a driven part connected to the rotor; a pump case having a cylindrical part that is outside the motor case and abuts against the bottom of the motor case in the axial direction and rotatably houses the driven part; a cover that closes the side of the cylindrical part opposite the motor case and abuts against the side of the motor case opposite the driven part; and an opposing part that faces the protrusions and is spaced apart in the axial direction, wherein the axial lengths of the driven part and the cylindrical part of the pump case are equal, and the linear expansion coefficients of the driven part and the cylindrical part of the pump case are 10×10 -6 / K or more and 25×10 -6 / K or less.

[0009] In the electric pump configured in this manner, a pump chamber is formed by the cylindrical portion that faces the bottom in the axial direction, and since the protruding portion and the facing portion are spaced apart, even if the axial lengths of the motor case and the cylindrical portion of the pump case change due to temperature changes, the protruding portion does not abut on the facing portion, and the cylindrical portion does not rise up from the bottom of the motor case. Also, in the electric pump, the axial lengths of the driven portion and the cylindrical portion of the pump case are equal, and the linear expansion coefficients of the driven portion and the cylindrical portion of the pump case are 10 × 10 -6 / K or more and 25×10 -6 / K or less, the cylindrical portion is in contact with the bottom portion, and the axial length of the pump chamber is determined by the axial length of the cylindrical portion, so regardless of the difference in the linear expansion coefficients of the motor case and the pump case, the axial length of the pump chamber always matches the axial length of the cylindrical portion even when the temperature of the electric pump changes. Therefore, with the electric pump, the gap between the driven portion and the bottom and the gap between the driven portion and the pump case cover do not increase, so deterioration of pump efficiency can be suppressed.

[0010] The pump case of the electric pump may have a plurality of holes formed along the axial direction from the surface of the cylindrical portion facing the bottom of the motor case, facing each of the plurality of protrusions and allowing the insertion of the protrusions, with the bottoms of the holes forming the opposing portions. With an electric pump configured in this manner, the cylindrical portion can be made thicker in the radial direction to ensure a large contact area with the bottom of the cylindrical portion, thereby reducing the contact pressure between the cylindrical portion and the bottom when the pump case is fixed to the motor case with a fastener and suppressing creep of the motor case.

[0011] Furthermore, the electric pump may include a fastener attached to the protruding portion for fastening the opposing portion to the motor case. With an electric pump configured in this manner, the protruding portion is used to fasten the opposing portion with a fastener attached to the protruding portion, and the pump case is attached to the motor case, so that the pump case can be easily fastened to the motor case using a commonly used fastener. Furthermore, with an electric pump configured in this manner, because the protruding portion is inserted into the hole, the axial length of the pump case can be shortened compared to when the pump case is fastened to the motor case at another location, and therefore the overall length of the electric pump is shortened, improving the ease of installation in non-installed locations. [Effects of the Invention]

[0012] According to the electric pump of the present invention, it is possible to reduce the weight and suppress deterioration of the pump efficiency even when the temperature changes. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a vertical cross-sectional view of an electric pump according to an embodiment of the present invention; [Figure 2] FIG. 2 is a bottom view of the motor case according to the embodiment. [Figure 3] 2 is a cross-sectional view of the pump portion of the embodiment taken along the line XX' in FIG. 1. FIG. [Figure 4] FIG. 2 is a plan view of a pump case in the electric pump according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described below based on the embodiment shown in the drawings. As shown in Fig. 1, an electric pump 1 in this embodiment is configured to include a motor 2, a drive gear 10 as a driven part D driven by the motor 2, a driven gear 11 meshing with the drive gear 10, and a pump case 12 that rotatably houses the drive gear 10 and the driven gear 11.

[0015] Below, a detailed description will be given of each part of the electric pump 1. The motor 2 includes a stator 3, a rotor 4 rotatable relative to the stator 3, and a cylindrical motor case 5 with a bottom that houses the stator 3 and the rotor 4.

[0016] As shown in FIG. 1, the motor case 5 is a cylindrical body having a cylindrical frame 5a and a bottom 5b that closes the lower end of the frame 5a in FIG. 1, and has four protrusions 5c that rise from the bottom 5b downward in FIG. 1, which is the side opposite the stator, and a circuit board case 5d that is integrally formed on the outer periphery of the frame 5a.

[0017] In this embodiment, the motor case 5 is manufactured by molding in which the stator 3 is inserted into a mold and synthetic resin is injected into the mold, and the stator 3 embedded in the frame 5a is held together.

[0018] The bottom portion 5b is annular, with its outer periphery connected to the lower end of the frame 5a in Figure 1, and is provided on its inner periphery with an annular bearing holder 5b1 that protrudes into the frame 5a. A cylindrical bearing 6 that rotatably supports the outer periphery of the rotor 4 and a seal ring 7 that seals the outer periphery of the rotor 4 are attached to the inner periphery of the bearing holder 5b1.

[0019] As shown in Fig. 2, the bottom portion 5b has a pair of arc-shaped grooves 5b2, 5b3 arranged on the same circumference centered at the center of the bottom portion 5b, and four protrusions 5c at four locations on the circumference of a circle O whose center is on the outer periphery of the grooves 5b2, 5b3 of the bottom portion 5b and eccentric from the center of the circumference on which the grooves 5b2, 5b3 are provided. As shown in Fig. 1, the protrusions 5c are cylindrical, have a threaded groove on their inner periphery, extend downward from the lower end of the bottom portion 5b, and have a tapered surface on their outer periphery. The axial lengths of the protrusions 5c are the same, but may be different.

[0020] 2, the grooves 5b2 and 5b3 are provided at positions that are line-symmetrical with respect to a line L1 that passes through the center of the bottom portion 5b and extends in the up-down direction in FIG. 2. The circumferential distance between the upper ends of the grooves 5b2 and 5b3 in FIG. 2 is wider than the circumferential distance between the lower ends of the grooves 5b2 and 5b3 in FIG. 2.

[0021] The protrusions 5c are provided on the circumference of the circle O on which they are provided at positions that are line-symmetrical with respect to the line L1, and are arranged offset upward in FIG. 2 relative to the bottom 5b.

[0022] 1 and 2, the substrate case 5d has a rectangular cylindrical shape and is connected to the outer periphery of the frame 5a, and houses the substrate 8. The upper open end of the substrate case 5d is closed by a cap 9.

[0023] Although not shown in detail, the stator 3 includes an annular stator core 3a with a plurality of teeth on its inner periphery, windings 3b wound around the teeth of the stator core 3a, and an annular bus bar 3c connected to the windings 3b, and as described above, is embedded in the synthetic resin that forms the frame 5a of the motor case 5. The bus bar 3c of the stator 3 protrudes to the outside from the synthetic resin that forms the frame 5a and is connected to a board 8 fixed inside the board case 5d. The board 8 includes a drive circuit (not shown) for driving the motor 2, and can receive power from an external power source (not shown) to energize the windings 3b of the stator 3.

[0024] The rotor 4 is configured to include a shaft 4a rotatably inserted into a bearing 6 attached to the inner periphery of a bearing holder 5b1 of the motor case 5, a yoke 4b attached to the outer periphery of the shaft 4a, and a permanent magnet 4c attached to the outer periphery of the yoke 4b and radially facing the stator 3. Therefore, in the motor 2, a rotating magnetic field is generated in the stator 3 by energizing the winding 3b, and the rotor 4 can be rotated by attracting the permanent magnet 4c.

[0025] As shown in FIG. 1, the lower end of the shaft 4a passes through the inner periphery of the bottom portion 5b of the motor case 5 and protrudes into the pump case 12 disposed below the motor case 5.

[0026] The pump case 12 is cylindrical and is placed under the lower end of the bottom 5b of the motor case 5. As shown in Figures 1 and 3, the pump case 12 specifically includes a cylindrical portion 12a, four holes 12b formed along the axial direction from the surface of the cylindrical portion 12a facing the bottom 5b of the motor case 5, each hole 12b facing the corresponding protrusion 5c and allowing the protrusion 5c to be inserted, opposing portions 12c formed at the bottom of the holes 12b facing the tips of the protrusions 5c, and a cover 12d that closes the lower end of the cylindrical portion 12a.

[0027] The inner and outer peripheries of the cylindrical portion 12a are not concentric, and the center of the inner periphery of the cylindrical portion 12a is eccentric in the radial direction from the center of the outer periphery of the cylindrical portion 12a, upward in Fig. 3. The shaft 4a is disposed at the center of the outer periphery of the cylindrical portion 12a, and therefore protrudes at a position eccentric from the center of the inner periphery of the cylindrical portion 12a.

[0028] As described above, the inner and outer circumferential circles of the cylindrical portion 12a have different centers, and therefore the inner circle is positioned eccentrically upward relative to the outer circle in Fig. 3. Therefore, the radial thickness of the cylindrical portion 12a is thinner at the upper side and thicker at the lower side in Fig. 3. The holes 12b are formed at positions corresponding to the positions of the protrusions 5c on the bottom 5b of the motor case 5, and have an inner diameter larger than the outer diameter of the protrusions 5c. When the pump case 12 is placed on the bottom 5b of the motor case 5, the corresponding protrusions 5c are inserted into the holes 12b.

[0029] As shown in FIG. 3, the hole 12b provided in the radially thick portion of the cylindrical portion 12a is not in contact with the inner or outer periphery of the cylindrical portion 12a. Also, as shown in FIG. 1, the hole 12b opens from the upper end of the cylindrical portion 12a facing the bottom portion 5b and extends in the axial direction. As shown in FIG. 3, the hole 12b provided in the radially thin portion of the cylindrical portion 12a is not in contact with the inner periphery of the cylindrical portion 12a but opens to the outer periphery. Also, as shown in FIG. 1, the hole 12b opens from the upper end of the cylindrical portion 12a facing the bottom portion 5b and extends in the axial direction. Thus, the hole 12b may open to the outer periphery of the cylindrical portion 12a, opening not only at the axial end but also at a portion of the side. Therefore, the inner periphery of the cylindrical portion 12a is formed into a cylindrical surface that is continuous in the circumferential direction by the hole 12b, and the cylindrical portion 12a forms a partition wall that houses the driving gear 10 and the driven gear 11, which serve as the driven part D.

[0030] The axial length of each hole 12b is shorter than the axial length of the cylindrical portion 12a, and the bottom of the hole 12b in the cylindrical portion 12a forms an opposing portion 12c that faces the protrusion 5c in the axial direction. Furthermore, the axial length of each hole 12b is longer than the axial length of the corresponding protrusion 5c, and when the upper end of the cylindrical portion 12a of the pump case 12 is abutted against the lower surface of the bottom 5b of the motor case 5 and the corresponding protrusion 5c is inserted into each hole 12b, a gap is always formed in the axial direction between the opposing portion 12c, which is the bottom of the hole 12b, and the protrusion 5c.

[0031] 1, the cylindrical portion 12a has a bolt insertion hole 12c1 that opens from its lower end on the side opposite the motor and penetrates an opposing portion 12c that is the bottom of the hole 12b. As shown in FIG. 1, the pump case 12 configured in this manner is placed on the motor case 5 by inserting the protruding portion 5c into the hole 12b and abutting the upper end of the motor side of the cylindrical portion 12a against the lower end of the bottom portion 5b of the motor case 5. After that, when a bolt 20 serving as a fastener is inserted into the bolt insertion hole 12c1 and screwed onto the inner periphery of the protruding portion 5c, the opposing portion 12c abuts against the head 20a of the bolt 20, and is thereby sandwiched between the bolt 20 and the bottom portion 5b of the motor case 5 and fixed to the motor case 5. Because there is a gap between the upper end of the opposing portion 12c of the pump case 12 fixed in this manner in FIG. 1 and the lower end of the protruding portion 5c, they do not come into direct contact.

[0032] The lower end of the tubular portion 12a in Figure 1, which is the side opposite the motor case, is closed by a cover 12d, and when the pump case 12 is fixed to the motor case 5, a sealed pump chamber P is formed by the bottom 5b of the motor case 5, the tubular portion 12a of the pump case 12, and the cover 12d.

[0033] 4, the cover 12d has arc-shaped grooves 12d1 and 12d2 at its end facing the pump chamber P, as well as a discharge port 12d3 that opens from the side opposite the pump chamber and communicates with groove 12d1, and a suction port 12d4 that opens from the side opposite the pump chamber and communicates with groove 12d2. The cover 12d also has a recess 12d5 into which a cylindrical bearing 21 that rotatably contacts the outer periphery of the lower end of the shaft 4a in FIG. 1 is fitted. Thus, the shaft 4a of the rotor 4 is supported by the bearing 6 of the motor case 5 and the bearing 21 attached to the pump case 12, allowing it to rotate without axial wobble. In addition, the holes 12b provided in the tubular portion 12a and the protrusions 5c of the motor case 5 are provided on a circumference concentric with the driven gear 11, with two on the outer periphery of the groove 12d1 leading to the discharge port 12d3 and two on the outer periphery of the groove 12d2 leading to the suction port 12d4.

[0034] 1 and 3, a driving gear 10 and a driven gear 11 are rotatably housed in the pump chamber P, which is the inner periphery of the cylindrical portion 12a of the pump case 12. The driven gear 11 is annular and has internal teeth 11a provided on its inner periphery, and its outer periphery is in sliding contact with the inner periphery of the cylindrical portion 12a of the pump case 12, allowing it to rotate about its axis within the pump case 12.

[0035] The driven gear 11 is rotatable within the pump case 12 around the center of the inner circumference of the cylindrical portion 12a. Therefore, the driven gear 11 rotates around a position eccentric to the axis of the rotor 4 of the motor 2.

[0036] On the other hand, the drive gear 10 is annular and has external teeth 10a on its outer periphery that mesh with the internal teeth 11a of the driven gear 11, and is attached to the shaft 4a of the rotor 4, which is inserted into the inner periphery. Therefore, the drive gear 10 can rotate around the axis of the rotor 4. The number of teeth on the external teeth 10a of the drive gear 10 is one less than the number of teeth on the internal teeth 11a of the driven gear 11, and the drive gear 10 meshes eccentrically with the driven gear 11. The external teeth 10a and the internal teeth 11a are trochoidal, but may be shaped like a hypocycloid or other curve other than a trochoid. A crescent-shaped shape may be provided between the drive gear 10 and the driven gear 11.

[0037] The axial length of the drive gear 10 and the driven gear 11 is equal to the axial length of the cylindrical portion 12a of the pump case 12, and when the drive gear 10 and the driven gear 11 are housed in the pump chamber P, the upper ends of the drive gear 10 and the driven gear 11 in FIG. 1 come into sliding contact with the lower end surface of the bottom portion 5b of the motor case 5, and the lower ends of the drive gear 10 and the driven gear 11 in FIG. 1 come into sliding contact with the upper end surface of the cover 12d. The drive gear 10, the driven gear 11, and the pump case 12 have a linear expansion coefficient of 10×10 -6 / K or more and 25×10 -6 / K or less. In this embodiment, the driving gear 10, the driven gear 11 and the pump case 12 are made of aluminum, but may be made of metal such as iron or stainless steel, or phenolic resin.

[0038] When current is applied to the winding 3b of the motor 2 to rotate the drive gear 10, the driven gear 11, which meshes with the drive gear 10, also rotates. Because the drive gear 10 is eccentric with respect to the driven gear 11, the volume of the cavity between the external teeth 10a of the drive gear 10 and the internal teeth 11a of the driven gear 11 changes as the drive gear 10 and the driven gear 11 rotate. When the drive gear 10 is rotated counterclockwise in FIG. 3, the driven gear 11 also rotates counterclockwise, and the volume of the cavity between the drive gear 10 and the driven gear 11 on the left side of the imaginary line V, which passes through the center of rotation of the drive gear 10 and runs along the vertical direction in FIG. 3, decreases as the drive gear 10 and the driven gear 11 rotate counterclockwise. On the other hand, the volume of the cavity between the drive gear 10 and the driven gear 11 on the right side of the imaginary line V increases as the drive gear 10 and the driven gear 11 rotate counterclockwise.

[0039] The cavities between the drive gear 10 and the driven gear 11 on the left side of the imaginary line V are connected to each other by an arc-shaped groove 5b2 in the bottom 5b, and the cavities between the drive gear 10 and the driven gear 11 on the right side of the imaginary line V are connected to each other by an arc-shaped groove 5b3 in the bottom 5b.

[0040] In addition, the cavity between the drive gear 10 and the driven gear 11 on the left side of the imaginary line V is connected to the discharge port 12d3 by an arc-shaped groove 12d1 in the cover 12d, and the cavity between the drive gear 10 and the driven gear 11 on the right side of the imaginary line V is connected to the suction port 12d4 by an arc-shaped groove 12d2 in the cover 12d.

[0041] Therefore, when the drive gear 10 is driven counterclockwise in Figure 3, liquid is taken in through the suction port 12d4 into the cavity to the right of the imaginary line V, where the volume is expanding, and the taken-in liquid is pushed out from the cavity to the left of the imaginary line V, where the volume is decreasing, and can be discharged outside the pump case 12 through the discharge port 12d3.

[0042] As described above, the electric pump 1 of this embodiment is an internal gear pump configured by housing the drive gear 10 and driven gear 11 as the driven part D in the pump case 12. Note that the electric pump 1 may also be an external gear pump in which the drive gear 10 and driven gear 11 in the driven part D mesh with each other through external teeth. Furthermore, although not shown, the electric pump 1 may also be a vane pump in which the driven part D is configured by a pump rotor connected to the rotor 4 of the motor 2 and vanes inserted so as to be able to enter and exit into a plurality of grooves opening from the outer periphery of the rotor pump, and the tips of the vanes slide against the inner periphery of the pump case 12 to drive the pump rotor, thereby performing pumping operation.

[0043] Furthermore, in the electric pump 1 of this embodiment, when the drive gear 10 is driven in the aforementioned direction, the highest pressure occurs in the cavity between the drive gear 10 and the driven gear 11 in FIG. 3 , which is located above a line passing through the center of the shaft 4a of the rotor 4. However, the distance between the two protruding portions 5c located above the shaft 4a in FIG. 3 , where the pressure is highest, is narrower than the distance between the two protruding portions 5c located below the shaft 4a in FIG. 3 , where the pressure is low. In this way, the multiple protruding portions 5c are positioned above the shaft 4a, where the pressure is high, so that each protruding portion 5c can bear the load acting on the protruding portions 5c to separate the pump case 12 from the motor case 5 due to the pressure in the pump chamber P. This reduces the axial tensile stress acting on the protruding portions 5c, thereby reducing fatigue of the motor case 5.

[0044] In the electric pump 1 configured as above, when the temperature of the atmosphere surrounding the electric pump 1 changes or the temperature rises due to heat generation during operation, the motor case 5, drive gear 10, driven gear 11, and pump case 12, all of which are made of resin, expand or contract. The drive gear 10, driven gear 11, and pump case 12 have linear expansion coefficients of 10 × 10 -6 / K or more and 25×10 -6 / K or less, and the expansion or contraction of the drive gear 10, the driven gear 11, and the pump case 12 is about the same, but the degree of expansion or contraction of the plastic motor case 5 is greater than the degree of expansion or contraction of the drive gear 10, the driven gear 11, and the pump case 12. However, in the electric pump 1 of this embodiment, the cylindrical portion 12a of the pump case 12 abuts against the bottom portion 5b of the motor case 5, and a gap is provided between the tip of the protruding portion 5c of the motor case 5 and the opposing portion 12c that is fixed to the motor case 5 by the bolt 20 that serves as a fastener attached to the protruding portion 5c.

[0045] Therefore, even if the axial lengths of the motor case 5 and the cylindrical portion 12a of the pump case 12 change due to temperature changes, the protruding portion 5c and the opposing portion 12c of the motor case 5 are separated from each other to provide the gap therebetween, so the protruding portion 5c does not come into contact with the opposing portion 12c, and the cylindrical portion 12a does not rise up from the bottom 5b of the motor case 5. As described above, in the electric pump 1 of this embodiment, the cylindrical portion 12a is in contact with the bottom 5b, and the axial length of the pump chamber P is determined by the axial length of the cylindrical portion 12a. Therefore, regardless of the difference in the linear expansion coefficients of the motor case 5 and the pump case 12, the axial length of the pump chamber P always coincides with the axial length of the cylindrical portion 12a, even if the temperature of the electric pump 1 changes. The axial length of the cylindrical portion 12a is equal to the axial lengths of the drive gear 10 and the driven gear 11, and the linear expansion coefficients of the drive gear 10, the driven gear 11, and the pump case 12 are 10×10 -6 / K or more and 25×10 -6 / K or less, and the expansion or contraction of the driving gear 10, the driven gear 11, and the cylindrical portion 12a of the pump case 12 is also about the same, so no large gaps are formed between the upper ends of the driving gear 10 and the driven gear 11 in FIG. 1 and the bottom portion 5b, or between the lower ends of the driving gear 10 and the driven gear 11 in FIG. 1 and the cover 12d.

[0046] As described above, the electric pump 1 of this embodiment includes a motor 2 having a stator 3, a rotor 4 rotatable relative to the stator 3, a resin motor case 5 that is cylindrical with a bottom and houses the stator 3 and the rotor 4 therein and has a plurality of protruding portions 5c rising from a bottom portion 5b on the opposite side to the stator, a driven portion D connected to the rotor 4, a pump case 12 having a tubular portion 12a that is on the outside of the motor case 5 and abuts against the bottom portion 5b of the motor case 5 in the axial direction and rotatably houses the driven portion D, a cover 12d that closes the opposite motor case side of the tubular portion 12a and abuts against the opposite motor case side of the driven portion D, and an opposing portion 12c that is spaced apart in the axial direction and faces the protruding portions 5c, and the axial lengths of the driven portion D and the tubular portion 12a of the pump case 12 are equal, and the linear expansion coefficients of the driven portion D and the tubular portion 12a of the pump case 12 are 10×10 -6 / K or more and 25×10 -6 / K or less.

[0047] According to the electric pump 1 configured in this manner, the pump chamber P is formed by the cylindrical portion 12a that faces the bottom portion 5b in the axial direction, and the driven portion D has a linear expansion coefficient of 10×10 -6 / K or more and 25×10 -6 / K or less, the gap between the driven portion D and the bottom portion 5b and the gap between the driven portion D and the cover 12d do not increase even when the temperature changes, so deterioration of the pump efficiency can be suppressed. Therefore, according to the electric pump 1 of this embodiment, even if the motor case 5 is made of resin to reduce its weight, deterioration of the pump efficiency due to temperature changes can be suppressed. According to the electric pump 1 of this embodiment, deterioration of the pump efficiency due to temperature changes can be suppressed while reducing its weight.

[0048] The gap between the driven part D and the bottom 5b of the motor case 5 and the gap between the driven part D and the cover 12d of the pump case 12 are controlled so that the driven part D can rotate smoothly within the pump case 12 and so that leakage of liquid from these gaps is below the allowable amount for operation of the pump. Therefore, the condition that the axial lengths of the driven part D and the tubular part 12a of the pump case 12 are equal also includes a case where there is an error equal to the sum of the lengths of the gaps when the axial length of the tubular part 12a is subtracted from the axial length of the driven part D. Therefore, even if the axial length of the tubular part 12a is longer than the axial length of the driven part D by the error, this is still included in the category of the axial lengths of the driven part D and the tubular part 12a of the pump case 12 being equal.

[0049] Furthermore, the axial length of the gap between the protrusion 5c and the opposing portion 12c may be set so that the protrusion 5c and the opposing portion 12c do not come into contact with each other within the temperature range in which the electric pump 1 can be installed in the environment in which the electric pump 1 is installed.

[0050] Furthermore, in the electric pump 1 of this embodiment, an annular gap is provided between the outer periphery of the protruding portion 5c and the inner periphery of the hole 12b, and consideration is given to preventing the outer periphery of the protruding portion 5c from coming into contact with the inner periphery of the hole 12b within the temperature range of the electric pump 1 in the environment in which the electric pump 1 is installed. By providing an annular gap between the outer periphery of the protruding portion 5c and the inner periphery of the hole 12b in this manner, it is possible to prevent the outer periphery of the protruding portion 5c from coming into contact with the inner periphery of the hole 12b due to temperature changes, preventing expansion of the protruding portion 5c and causing excessive stress in the protruding portion 5c, and suppressing deterioration of the motor case 5.

[0051] Furthermore, the protrusion 5c has a tapered outer surface and a tapered shape, which makes it easier to insert the bottom 5b of the motor case 5 into the hole 12b when overlapping the cylindrical portion 12a of the pump case 12, making it easier to assemble the electric pump 1.

[0052] In the electric pump 1 of this embodiment, the pump chamber P is formed by abutting the cylindrical portion 12a of the pump case 12 against the bottom portion 5b of the motor case 5, and if there is a concern that the drive gear 10 and the driven gear 11 will be in sliding contact with the bottom portion 5b, which is made of resin, and therefore wear of the bottom portion 5b is a concern, a plate may be placed between the drive gear 10, the driven gear 11, and the cylindrical portion 12a and the bottom portion 5b. In this case, the plate functions as the bottom portion 5c of the motor case 5, and the plate and the pump case 12 form the pump chamber P, making it possible to prevent the drive gear 10 and the driven gear 11 from directly abutting against the resin of the motor case 5.

[0053] Furthermore, in the electric pump 1 of this embodiment, the pump case 12 has a plurality of holes 12b formed along the axial direction from a surface of the cylindrical portion 12a facing the bottom portion 5b of the motor case 5. The holes 12b face the respective protrusions 5c and allow insertion of the protrusions 5c, and the bottoms of the holes 12b form opposing portions 12c. According to the electric pump 1 configured in this manner, the radial thickness of the cylindrical portion 12a can be increased to ensure a large contact area with the bottom portion 5b of the cylindrical portion 12a. This reduces the contact pressure between the cylindrical portion 12a and the bottom portion 5b when the pump case 12 is fixed to the motor case 5 with the bolts (fixing devices) 20, thereby suppressing creep of the motor case 5. In this way, by providing the holes 12b in the cylindrical portion 12a for inserting the protrusions 5c and widening the radial thickness of the cylindrical portion 12a, the contact pressure between the cylindrical portion 12a and the bottom portion 5b can be reduced. However, since the cylindrical portion 12a only needs to form a pump chamber P that accommodates the drive gear 10 and the driven gear 11, instead of forming the opposing portion 12c by providing a hole 12b in the cylindrical portion 12a, the radial wall of the cylindrical portion 12a may be thinned, and an opposing portion formed of a flange or the like that faces the protrusion 5c with an axial gap on the outer periphery of the cylindrical portion 12a on the side opposite the motor may be provided.

[0054] Furthermore, the electric pump 1 of the present embodiment includes a bolt (fixing device) 20 that is attached to the protruding portion 5c and fixes the opposing portion 12c to the motor case 5. According to the electric pump 1 configured in this manner, the protruding portion 5c is used to attach the pump case 12 to the motor case 5 by fixing the opposing portion 12c with the bolt (fixing device) 20 attached to the protruding portion 5c, and therefore the pump case 12 can be easily fixed to the motor case 5 using a commonly used fixing device. Furthermore, according to the electric pump 1 configured in this manner, because the protruding portion 5c is inserted into the hole 12d, the axial length of the pump case 12 can be shortened compared to when the pump case 12 is fixed to the motor case 5 at another location, and therefore the overall length of the electric pump 1 is also shortened, improving the mountability of the electric pump 1 in non-installation locations.

[0055] Furthermore, the fixing device may include, in addition to the bolt 20, a screw shaft partially embedded in the protruding portion 5c and a nut screwed to the screw shaft, or it may be anything that can be attached to the protruding portion 5c and fix the opposing portion 12c so that it does not move away from the protruding portion 5c.

[0056] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0057] 1 electric pump, 2 motor, 3 stator, 4 rotor, 5 motor case, 5b bottom, 5c protrusion, 10 drive gear, 11 driven gear, 12 pump case, 12a cylindrical portion, 12b hole, 12c opposing portion, 12d cover, 20 bolt (fixing device), D driven portion

Claims

1. a motor including a stator, a rotor rotatable relative to the stator, and a cylindrical, bottomed motor case made of resin that houses the stator and the rotor and has a plurality of protrusions that rise from the bottom toward the side opposite the stator; a driven part connected to the rotor; a pump case having a cylindrical portion that is located outside the motor case and abuts against a bottom of the motor case in the axial direction and rotatably houses the driven portion; a cover that closes the cylindrical portion on the side opposite the motor case and abuts against a side surface of the driven portion on the side opposite the motor case; and an opposing portion that faces the protruding portion and is spaced apart in the axial direction; The driven part and the cylindrical part of the pump case have the same axial length, and the driven part and the cylindrical part of the pump case have a linear expansion coefficient of 10×10 －６ / K or more and 25 × 10 －６ / K or less An electric pump characterized by:

2. The pump case has a plurality of holes formed along the axial direction from a surface of the cylindrical portion facing the bottom of the motor case, facing the plurality of protrusions, respectively, to allow the insertion of the protrusions, and the facing portions are formed at the bottoms of the holes.

2. The electric pump according to claim 1.

3. a fastener attached to the protruding portion to fasten the opposing portion to the motor case; 3. The electric pump according to claim 1 or 2.

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