Permanent magnet embedded motor and pump device

Abstract

To provide a permanent magnet embedded motor in which occurrence of a local stress can be suppressed or prevented and a firm structure can be obtained without causing an increase in processing cost and complication or upsizing of a housing structure, etc., and a pump device using the motor as a drive source.SOLUTION: A permanent magnet embedded motor includes: a stator St including a stator core 20 formed into a ring shape by layering a plurality of steel plates Sp which are obtained by punching a rolled steel plate material and a coil 40 for excitation; a rotor Rt disposed inside the stator and including a permanent magnet 60; and a metal housing 1 including a cylindrical fitting recess 1b centered on a prescribed axis S so as to be fit with the stator. The stator St is shrinkage fitted to the housing while a rolling direction Rd of the steel plates is set in an expansion direction Ed in which a change amount of an inner diameter D of the fitting recess 1b is large when the housing is heated.SELECTED DRAWING: Figure 17

Description

[Technical field]

[0001] The present invention relates to an embedded permanent magnet motor including a stator around which a coil is wound and a rotor in which a permanent magnet is embedded, and to a pump device using the same as a drive source. [Background technology]

[0002] A known conventional embedded permanent magnet motor is one that includes a stator including an annular stator core with circumferentially arranged teeth and slots and a coil wound around the teeth, a rotor that is rotatably arranged inside the stator and has a permanent magnet inserted therein, and a housing that fixes the stator core and supports the rotor so that it can rotate freely (for example, Patent Document 1). In this permanent magnet motor, the stator core is formed by stacking multiple electromagnetic steel plates punched out from thin electromagnetic steel material in order to reduce iron loss due to eddy current loss, and is fixed into the housing by shrink fitting or the like.

[0003] Incidentally, electromagnetic steel sheet material is produced by rolling a manufactured steel billet (steel ingot) in a predetermined direction and also by appropriately performing heat treatment, etc., to form a strip-shaped steel sheet material, which is then wound up into a rolled material. When forming a plurality of electromagnetic steel sheets that will serve as the base material for a stator core, the rolled material is stretched into a flat plate and punched while being fed forward, to produce electromagnetic steel sheets of the designed dimensions.

[0004] However, when a stator core is formed by stacking a plurality of punched electromagnetic steel sheets, the resulting stator core tends to be slightly larger in the rolling direction than the design value due to residual distortion resulting from the rolling process of the electromagnetic steel sheet material, processing errors when stretching and punching the rolled material as the electromagnetic steel sheet material, etc. Increasing the processing accuracy to address this leads to an increase in processing costs.

[0005] Furthermore, when the above-mentioned stator core is fixed, for example, by heating and expanding the housing and then shrink fitting, the housing has a non-constant coefficient of thermal expansion depending on its shape and form, and there is a risk that after shrink fitting, this will result in areas of locally increased internal stress in the housing or stator core. Therefore, it is desirable to suppress or prevent local stresses, etc. occurring in each component, while taking into consideration the dimensional tolerances and geometric tolerances of the stator core and housing, and also the dimensional errors depending on the rolling process of the electromagnetic steel sheet and the roll material, thereby achieving a more reliable structure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-116563 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a permanent magnet embedded motor and a pump device using the same as a drive source, which can suppress or prevent the occurrence of localized stress and obtain a robust structure without increasing processing costs or complicating and enlarging the housing structure, in consideration of the problems with the prior art. [Means for solving the problem]

[0008] The permanent magnet embedded motor of the present invention comprises a stator including a stator core formed into a circular ring shape by stacking multiple steel plates obtained by punching rolled steel plate material and an excitation coil, a rotor arranged inside the stator and including a permanent magnet, and a metal housing including a cylindrical fitting recess centered on a predetermined axis into which the stator is fitted, and the stator is shrink-fitted into the housing with the rolling direction of the steel plates oriented in the expansion direction that causes the largest change in the inner diameter of the fitting recess when the housing is heated.

[0009] In the above-mentioned permanent magnet embedded motor, the housing may include a wall portion defining the mating recess, and a thick-walled portion that is continuous with the periphery of the wall portion on the opening side of the mating recess and is thicker than the wall portion, and the expansion direction may coincide with the angular position about the axis at which the cross-sectional area of ​​the thick-walled portion is largest in a cross section including the axis.

[0010] In the above-described permanent magnet embedded motor, a configuration may be adopted in which the housing includes a wall portion defining the mating recess, and two thick portions that are thicker than the wall portion and are formed continuously around the wall portion on the opening side of the mating recess in an orthogonal line direction perpendicular to the axis, and the stator is shrink-fitted into the housing with the rolling direction oriented in the arrangement direction of the two thick portions.

[0011] In the above-mentioned permanent magnet embedded motor, a configuration may be adopted in which the housing includes a wall portion defining the mating recess, a flange portion formed around the wall portion on the opening side of the mating recess, and two boss portions arranged in the flange portion in an orthogonal line direction perpendicular to the axis and thicker than the wall portion, and the stator is shrink-fitted into the housing body with the rolling direction oriented in the arrangement direction of the two boss portions.

[0012] In the above-described embedded permanent magnet motor including the two boss portions, a configuration may be adopted in which the flange portion is formed to be thicker than the wall portion.

[0013] In the above-described embedded permanent magnet motor including the two boss portions, a configuration may be adopted in which the two boss portions are formed to be thicker than the flange portion.

[0014] In the permanent magnet embedded motor including the two boss portions, the flange portion may have a configuration including a plurality of hollowed-out portions in an area outside the area through which the orthogonal line passes.

[0015] In the above-described embedded permanent magnet motor, the stator may have a configuration including an indicator that indicates the rolling direction.

[0016] In the above-mentioned embedded permanent magnet motor, a configuration may be adopted in which the thickness of the steel plate is 0.2 mm to 0.5 mm.

[0017] In the above-described embedded permanent magnet motor, a configuration may be adopted in which the housing is made of an aluminum material.

[0018] In the above-described permanent magnet embedded motor, a configuration may be adopted in which the stator core has teeth and slots arranged in the circumferential direction, and the stator includes a coil wound around the teeth via a resin bobbin.

[0019] In the above-mentioned permanent magnet embedded motor, the rotor may have a configuration including a cylindrical rotor core formed by stacking a plurality of steel plates obtained by punching a rolled steel plate material and having insertion holes arranged in the circumferential direction, and permanent magnets inserted into the insertion holes.

[0020] The embedded permanent magnet motor of the present invention is a pump device comprising a pump unit that draws in and discharges a fluid, a rotating shaft connected to the pump unit, and a drive source that exerts a driving force on the rotating shaft, and is configured to employ any of the embedded permanent magnet motors configured as described above as the drive source.

[0021] In the above pump device, the pump unit may be a trochoid pump including an inner rotor to which the rotating shaft is connected, and an outer rotor that meshes with the inner rotor. Effect of the Invention

[0022] The embedded permanent magnet motor having the above configuration can suppress or prevent the occurrence of localized stress (stress concentration) and obtain a robust structure without increasing processing costs, complicating the structure of the housing, or increasing its size, etc. Furthermore, by using the embedded permanent magnet motor having the above configuration as a drive source, a highly reliable pump device can be obtained. [Brief description of the drawings]

[0023] [Figure 1] 1 is an external perspective view showing a pump device including a permanent magnet embedded motor according to the present invention; [Diagram 2] FIG. 2 is a cross-sectional view of the pump device shown in FIG. [Diagram 3] FIG. 2 is an exploded perspective view of the pump device shown in FIG. [Figure 4] 2 is a cross-sectional view showing a fluid intake port and a fluid discharge port in the pump device shown in FIG. 1, taken along a plane perpendicular to the axis which is the center line of rotation of the rotor. [Diagram 5] 2 is a plan view showing a housing main body which forms a part of a housing included in the pump device shown in FIG. 1. [Figure 6] FIG. 6 is an external perspective view of a housing main body shown in FIG. 5. [Figure 7] 7 is a perspective cross-sectional view of the housing main body taken along line XX in FIG. 6. [Figure 8] 2 is an external perspective view showing a permanent magnet embedded motor serving as a drive source included in the pump device shown in FIG. 1. [Figure 9] FIG. 9 is an exploded perspective view of the embedded permanent magnet motor shown in FIG. 8. [Figure 10] 9 is a cross-sectional view taken along a plane perpendicular to the axis, illustrating the internal structure of the embedded permanent magnet motor illustrated in FIG. 8. [Figure 11] 9 is an external perspective view showing a stator core that constitutes a part of the permanent magnet embedded motor shown in FIG. 8. [Figure 12] 12 is a plan view of the stator core shown in FIG. 11 as viewed from one end side. [Figure 13] 4 is a schematic diagram showing a process for manufacturing a steel plate forming a stator core from a rolled steel plate material by punching. FIG. [Figure 14] 9 is an external perspective view of a rotor constituting a part of the embedded permanent magnet motor shown in FIG. 8, as viewed from one end side. [Figure 15] 9 is an external perspective view of a rotor constituting a part of the permanent magnet embedded motor shown in FIG. 8, as viewed from the other end side. [Figure 16] 2 is a plan view of a rotor core that constitutes a part of a permanent magnet embedded motor, as viewed from one end side. FIG. [Figure 17] 10 is a process diagram showing a process of heating a housing body that constitutes a part of the housing and shrink-fitting a stator into a fitting recess of the housing body. [Figure 18] 10 is a process diagram showing a process of heating a housing body that constitutes a part of the housing and shrink-fitting a stator into a fitting recess of the housing body. [Figure 19] 10 is a process diagram showing a process of heating a housing body that constitutes a part of the housing and shrink-fitting a stator into a fitting recess of the housing body. [Figure 20] 10 is a schematic diagram showing internal stress generated around a fitting recess of a housing body after shrink fitting is completed; FIG. [Figure 21] FIG. 11 is a perspective cross-sectional view of a housing main body that forms a part of the housing in a permanent magnet embedded motor according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in Figures 1 to 3, a pump device equipped with an embedded permanent magnet motor in one embodiment includes a housing body 1, a pump cover 2, a motor cover 3, a board cover 4, a rotating shaft 5, a pump unit U, an embedded permanent magnet motor M as a driving source, a circuit board CB, etc.

[0025] The pump unit U is a trochoid pump that sucks in and discharges a fluid (here, oil), and includes an inner rotor 11 and an outer rotor 12. As shown in Figures 2, 8, and 9, the embedded permanent magnet motor M is a three-phase brushless motor having nine slots and six magnetic poles, and includes a stator St including a stator core 20, a bobbin 30, and a coil 40, a rotor Rt including a rotor core 50 and a permanent magnet 60, and a housing (housing body 1, motor cover 3). Here, the housing body 1 and the motor cover 3 function as part of the housing of the pump device and also as a housing for the permanent magnet embedded motor M, fixing the stator St and supporting the rotor Rt so as to be freely rotatable.

[0026] The housing body 1 is formed from a metal material, such as an aluminum material, and as shown in Figures 2, 3, 5 to 7, is provided with an accommodating recess 1a for accommodating the pump unit U, a fitting recess 1b for fitting and accommodating the stator St, a wall portion 1b2 defining the fitting recess 1b, a communication passage 1c connecting the accommodating recess 1a and the fitting recess 1b, annular recess 1d, annular recess 1e, end face 1f, end face 1g, a flange portion 1h, four boss portions 1j1, 1j2, 1j3, 1j4, a plurality of cutout portions 1k, and four screw holes 1m for screwing in screws b2 for fastening the board cover 4 and the motor cover 3.

[0027] The accommodation recess 1a defines a cylindrical inner circumferential surface and a bottom surface so as to accommodate the pump unit U rotatably therein. The fitting recess 1b is formed in a cylindrical shape centered on the axis S which is the rotation center of the rotor Rt, and has a fitting surface 1b1 into which the annular portion 21 of the stator core 20 is fitted. The wall portion 1b2 is formed in a cylindrical shape centered on the axis S so as to define the fitting recess 1b, and the wall thickness T1 thereof is formed smaller than the plate thickness T2 of the flange portion 1h as shown in FIG.

[0028] The communication passage 1c is formed in a cylindrical shape centered on the axis S, and the rotating shaft 5 is inserted therethrough with a predetermined gap therebetween. The annular recess 1d is formed in an annular shape centered on the axis S so that the lip seal Ls can be fitted into it. The annular recess 1e is formed in an annular shape centered on the axis S so that a bearing B1 that rotatably supports the rotating shaft 5 is fitted into the annular recess 1e with a washer W interposed between the lip-type seal Ls and the bearing B1. The end surface 1f is formed as a flat surface perpendicular to the axis S so that the pump cover 2 can be joined thereto. The end surface 1g is formed as a flat surface perpendicular to the axis S so that the motor cover 3 can be tightly joined with a sealant therebetween.

[0029] The flange portion 1h is fixed by joining and fastening the pump device to a mounting surface of an object, and is formed in a generally rectangular flat plate shape that continues around the periphery of the wall portion 1b2 on the opening side of the fitting recess 1b and expands in a direction perpendicular to the axis S. The flange portion 1h is formed thicker than the wall portion 1b2 of the fitting recess 1b as a whole, and as shown in Fig. 7, the plate thickness T2 in the direction in which the two boss portions 1j1, 1j2 are aligned, i.e., in the direction of an orthogonal line L perpendicular to the axis S, is formed to be thicker than the wall portion 1b2 that defines the fitting recess 1b (T2>T1). Furthermore, the flange portion 1h has a plurality of lightening holes 1k in an area outside the area through which the orthogonal line L passes. The plurality of lightening holes 1k can reduce the weight of the housing body 1 while ensuring the necessary mechanical strength. In addition, in the straight line region connecting the two boss portions 1j3, 1j4, a hollowed-out portion 1k is provided between the boss portions 1j3, 1j4 and the fitting recess 1b, and the plate thickness of the flange portion 1h in this region is formed to be smaller than the above-mentioned plate thickness T2.

[0030] The four boss portions 1j1, 1j2, 1j3, and 1j4 are fastened by fastening bolts (not shown) with the flange portion 1h joined to the joint surface of the object to which the pump device is applied, and are formed in a cylindrical shape with a boss height (thickness) T3, as shown in FIG. 7. That is, the four boss portions 1j1, 1j2, 1j3, and 1j4 are formed to be thicker than the flange portion 1h (T3>T2).

[0031] The housing body 1 having the above configuration is heated to a predetermined temperature when the stator St is shrink-fitted into the fitting recess 1b. In this heating process, the housing body 1 thermally expands, and the area with a large volume of material, i.e., the area including the thick portion, expands more than other areas. In the housing body 1, the overall thickness dimension (T2, T3) in the arrangement direction (direction of the orthogonal line L) of the two boss portions 1j1, 1j2 is larger than the wall thickness T1 of the wall portion 1b2 that defines the fitting recess 1b (T2, T3>T1). In addition, the overall thickness dimension in the arrangement direction of the two boss portions 1j3, 1j4 is thicker than the wall thickness T1 of the wall portion 1b2 that defines the fitting recess 1b, but is smaller and thinner than the thickness dimension in the arrangement direction of the two boss portions 1j1, 1j2. That is, in a configuration in which the housing body 1 includes a wall portion 1b2 that defines the mating recess 1b and a thick-walled portion (flange portion 1h, four boss portions 1j1, 1j2, 1j3, 1j4, and multiple hollowed-out portions 1k) that are continuous with the periphery of the wall portion 1b2 on the opening side of the mating recess 1b and are formed to be thicker than the wall portion 1b2, the cross-sectional area of ​​the thick-walled portion is largest at the angular position shown in Figure 7 in a cross section including the axis S.

[0032] Therefore, when the housing body 1 is heated, the amount of change Δd1 in the inner diameter of the fitting recess 1b in the arrangement direction of the boss portions 1j1 and 1j2 as the two thick portions becomes larger than the amount of change Δd2 in the inner diameter of the fitting recess 1b in the arrangement direction of the boss portions 1j3 and 1j4 as the two thick portions. The value of Δd (= Δd1 - Δd2) is in the range of several μm. 5, the arrangement direction of the boss portions 1j1, 1j2 as the two thick portions corresponds to the expansion direction Ed in which the amount of change in the inner diameter of the fitting recess 1b is large when the housing body 1 is heated. In other words, the expansion direction Ed in which the amount of change in the inner diameter of the fitting recess 1b is large when the housing body 1 is heated coincides with the angular position about the axis S in which the cross-sectional area of ​​the thick portions is maximized in a cross section including the axis S.

[0033] The pump cover 2 is formed from an aluminum material or the like, and as shown in Figures 2 and 3, is joined to the end face 1f of the housing body 1 to cover the accommodating recess 1a, and is provided with an intake port 2a for sucking in fluid and an exhaust port 2b for discharging pressurized fluid. With the pump unit U accommodated in the accommodation recess 1a, the pump cover 2 is joined to the end surface 1f of the housing body 1 and fastened and fixed by screws b1.

[0034] The motor cover 3 is formed from a resin material and is joined to the end face 1g of the housing body 1 to cover the mating recess 1b. As shown in Figures 2 and 3, the motor cover 3 has a through hole 3a centered on the axis S, an annular recess 3b, a fixing portion 3c for fixing the circuit board CB, a connector 3d for accommodating terminals for connection to the outside, and a circular hole for passing a screw b2. The through hole 3a is formed so that a detection target unit 5b fixed to the end of the rotating shaft 5 can be inserted therethrough. The annular recess 3b is formed in an annular shape centered on the axis S so that a cylindrical metal holder 3e can be fitted and fixed in place. The metal holder 3e fits and holds a bearing B2 that rotatably supports the rotating shaft 5. The motor cover 3 is joined to the end surface 1g of the housing body 1, and the board cover 4 is joined from the outside and fastened therebetween by screws b2.

[0035] The board cover 4 is formed of a metal plate, a resin material, or the like, and is fastened and fixed to the end surface 1g of the housing body 1 by screws b2 with the motor cover 3 sandwiched therebetween to cover the circuit board CB.

[0036] The rotating shaft 5 is made of a metal material and formed into a cylindrical shape centered on the axis S. As shown in Figures 2, 3, and 16, the rotating shaft 5 is provided with a connecting portion 5a having a two-face width at one end, a detectable unit 5b fixed to the other end, and a key groove portion 5c on the outer periphery. The rotating shaft 5 has a key groove portion 5c fitted into an axial hole 57 of a rotor core 50 included in a permanent magnet embedded motor M, and a connecting portion 5a connected to an inner rotor 11 of a pump unit U. In addition, the outer periphery is sealed by a lip-type seal Ls, and the rotating shaft 5 is rotatably supported by bearings B1 and B2 so as to transmit the rotational force of the rotor Rt to the inner rotor 11.

[0037] The detectable unit 5b is an annular holder in which a permanent magnet is fitted so that its north and south poles alternate around the axis S, and is positioned opposite the detection sensor C1 mounted on the circuit board CB, as shown in FIG. 2. The detected unit 5b functions as a detection target of the detection sensor C1 that detects the rotational angle position of the rotating shaft 5, that is, the rotor Rt.

[0038] As shown in FIGS. 2 and 3, the pump unit U includes an inner rotor 11 and an outer rotor 12. The inner rotor 11 is made of a material such as steel or sintered steel and is formed into a roughly star shape that defines an end face that slides on the bottom wall surface of the accommodating recess 1a of the housing body 1 and the inner wall surface of the pump cover 2. The inner rotor 11 is formed as an external gear having a tooth profile based on a trochoid curve, with a fitting hole 11a, seven protrusions (peaks) and seven recesses (valleys). The fitting hole 11a is formed so that the connecting portion 5a of the rotating shaft 5 is fitted therein. The inner rotor 11 is rotated by the rotary shaft 5 around the axis line S as the center of rotation in the direction of the arrow A in FIGS.

[0039] The outer rotor 12 is made of a material such as steel or sintered steel and is formed into an annular shape that defines an end face that slides on the bottom wall surface of the accommodating recess 1a of the housing body 1 and the inner wall surface of the pump cover 2. The outer rotor 12 has a circular outer circumferential surface 12a, eight protrusions and eight recesses, and is formed as an internal gear with teeth that can mesh with the inner rotor 11. The outer circumferential surface 12a is in contact with the inner circumferential surface of the installation recess 1a and is supported so as to be rotatable about an axis deviated from the axis S. The outer rotor 12 rotates at a slower speed than the inner rotor 11 while being linked to the rotation of the inner rotor 11 which rotates about the axis S. By the rotation of the inner rotor 11 and the outer rotor 12, the fluid is sucked into the pump chamber from the suction port 2a, pressurized, and discharged from the discharge port 2b.

[0040] The circuit board CB is equipped with components that control the drive of the permanent magnet embedded motor M, and has wiring printed thereon and various electronic components that constitute the control circuit mounted thereon.In addition, as shown in Figure 2, a detection sensor C1 that faces the detected unit 5b is also mounted on the circuit board CB. The detection sensor C1 is made up of a plurality of Hall elements arranged in an arc shape centered on the axis S. The detection sensor C1 is adapted to detect the magnetic pole position (rotational angle position) in the rotation direction of the rotating shaft 5, i.e., the rotor Rt.

[0041] The embedded permanent magnet motor M includes a stator St including a stator core 20, a bobbin 30, and a coil 40, and a rotor Rt including a rotor core 50 and a permanent magnet 60, as shown in FIGS.

[0042] The stator core 20 is formed as a laminate of multiple steel plates obtained by punching rolled steel plate material made of magnetic material, and as shown in Figures 11 and 12, it has an annular portion 21, nine teeth 22 as salient poles that protrude from the annular portion 21 toward the center (axis S) and are arranged at equal intervals in the circumferential direction, nine slots 23 arranged at equal intervals in the circumferential direction, and multiple cutout portions 24.

[0043] The nine teeth 22 are formed in the same shape and are rotationally symmetrical about the axis S, and each has a tip end surface 22a that defines a circular arc surface. The nine tip faces 22a are arranged on a cylindrical surface having a predetermined diameter, and are disposed so as to face the outer peripheral contour 50a (outer peripheral magnetic pole surface 53a) of the rotor core 50 with a predetermined gap therebetween. The nine slots 23 are formed in the same shape and are rotationally symmetric about the axis S, and each has an opening 23a having a predetermined width between the teeth 22 on both sides. The notch 24 is used during lamination press processing of the stator core 20 or for positioning relative to other components or as an index therefor.

[0044] Now, the manufacture of the stator core 20 will be described. As shown in FIG. 13, a rolled steel plate material Rm obtained by rolling a steel ingot into a strip shape and winding it up into a roll is used as a material. The rolled steel plate material Rm has a plate thickness in the range of 0.2 mm to 0.5 mm. In the punching press process, the rolled steel plate material Rm is set and fed to the press machine Pm along the conveyor line TL. When the rolled steel plate material Rm is stretched from the rolled state into a strip shape, the stretching direction of the strip corresponds to the rolling direction Rd.

[0045] Then, the press machine Pm punches out the steel plates Sp that define the outline of the stator core 20, and the steel plates Sp are manufactured in a sequential manner. Subsequently, the punched steel plates Sp are stacked and pressed together using a predetermined jig, and are bonded together. Therefore, the thickness of each steel plate Sp is in the range of 0.2 mm to 0.5 mm. Here, due to various factors such as residual stress and residual strain due to the rolling process of the rolled steel plate material Rm, and the processing accuracy when the material is stretched from the rolled state into a strip shape and punched, the outer diameter of the laminated stator core 20 tends to be larger by ΔD than the designed outer diameter D in the direction of the straight line L2, i.e., in the rolling direction Rd, as shown in Fig. 12. The value of ΔD is in the range of several µm.

[0046] Here, as shown in Figures 11 and 12, the direction of the straight line L2 (rolling direction Rd) is located at a position that passes through the center of an area where the notches 24 are not provided at equal intervals on the outer circumferential surface of the annular portion 21 and is perpendicular to the axis S. In other words, the notches 24 are provided at angles θ clockwise and θ counterclockwise from the straight line L2. Therefore, the rolling direction Rd of the steel sheet Sp can be recognized by using the central area Ma between the two notches 24, 24 as an index. Also, by providing a mark ML at the circumferential center position of the two notches 24, 24, the mark ML can be used as an index.

[0047] The bobbin 30 is formed in a two-piece structure using an electrically insulating resin material, and is assembled so as to sandwich the stator core 20 in the direction of the axis S. The coil 40 has a concentrated winding structure in which it is wound around each of the nine teeth 22 via the bobbin 30, and is electrically connected in three separate phases.

[0048] The rotor core 50 is made of a laminate of multiple steel plates obtained by punching rolled steel plate material made of magnetic material, and is formed so as to define a cylindrical outer peripheral contour 50a that faces the teeth 22 (tip surfaces 22a) of the stator core 20 with a predetermined gap therebetween, as shown in FIG. 10. As shown in Figures 10, 14 to 16, the rotor core 50 has six insertion holes 51 arranged at equal intervals in the circumferential direction, six V-groove-shaped recesses 52 arranged at equal intervals in the circumferential direction, six outer peripheral magnetic pole portions 53 arranged at equal intervals in the circumferential direction, six filling holes 54 arranged at equal intervals in the circumferential direction, six through holes 55 arranged at equal intervals in the circumferential direction, receiving portions 56 provided corresponding to each insertion hole 51, a shaft hole 57 into which the rotating shaft 5 fits, and six long holes 58 arranged at equal intervals in the circumferential direction.

[0049] Here, the six insertion holes 51, the six V-groove-shaped recesses 52, the six outer peripheral magnetic pole portions 53, the six filling holes 54, the six through holes 55, the six receiving portions 56, and the six long holes 58 are each formed rotationally symmetrically about the axis S, and are also formed line-symmetrically with respect to the radial straight line DL, except for the long hole 58, so only one of each will be described below.

[0050] The insertion hole 51 is an area where a permanent magnet 60 is inserted and fixed, i.e., an embedding area for the permanent magnet 60, and is formed so as to have an elongated cross-sectional shape in a direction Pd perpendicular to a radial straight line DL of the rotor Rt, as shown in Figure 16. Specifically, the insertion hole 51 is formed to include two wall surfaces 51a, 51b parallel to the vertical direction Pd, and two convex curved surfaces 51c protruding inwardly away from the through hole 55 at both ends in the vertical direction Pd. Because the insertion hole 51 has two convex curved surfaces 51c, when the permanent magnet 60 is inserted into the insertion hole 51, it is possible to suppress or prevent the permanent magnet 60 from shifting in the vertical direction Pd while providing a gap G on both sides.

[0051] The V-groove-shaped recess 52 is formed between the insertion holes 51, 51 in the circumferential direction to form a gap with a V-groove-shaped cross-section tapering toward the axis S, in order to divide the outer peripheral contour 50a in the circumferential direction and define the outer peripheral magnetic pole portion 53. The V-groove recess 52 functions as a flux barrier that suppresses or prevents leakage and short-circuiting of magnetic lines of force.

[0052] The outer peripheral magnetic pole portion 53 is a region that generates a magnetic pole corresponding to the permanent magnet 60 inserted into the insertion hole 51, and as shown in Figure 16, has a shape that is line-symmetrical with respect to a radial straight line DL, and has an outer peripheral magnetic pole surface 53a between two V-groove-shaped recesses 52, 52. The outer magnetic pole surface 53a is a cylindrical curved surface that defines the outer peripheral contour 50a, that is, a curved surface having a curvature of 2 / φZ when the outer diameter dimension of the outer peripheral contour 50a is φZ, and faces the tip surfaces 22a of the teeth 22 with a predetermined gap between them.

[0053] The filling hole 54 is a region to be filled with adhesive for fixing the permanent magnet 60 , and is formed radially inward of the insertion hole 51 so as to communicate with the insertion hole 51 . That is, after the permanent magnet 60 is inserted into the insertion hole 51, the filling hole 54 is filled with adhesive, thereby bonding the radially inward surface of the permanent magnet 60 to the wall surface 51a of the insertion hole 51.

[0054] As shown in FIG. 16, the through hole 55 is formed in a plane perpendicular to the axis S, between the insertion holes 51, 51 in the circumferential direction and radially inward of the V-groove-shaped recess 52 so as to form a gap with a circular cross section. The through hole 55 functions as a flux barrier that suppresses or prevents leakage and short circuits of magnetic lines, and also serves as a positioning portion into which a jig for positioning the rotor core 50 is inserted when assembling the permanent magnet 60 into the insertion hole 51.

[0055] 15 and 16, the receiving portion 56 is formed as a protruding piece that protrudes inward at the other open end of the insertion hole 51, and receives the end face of the permanent magnet 60 inserted into the insertion hole 51 to position the permanent magnet 60 in the direction of the axis S. Accordingly, the positioning and bonding work can be completed simply by inserting the permanent magnet 60 into the insertion hole 51. As shown in FIG. 16, the shaft hole 57 is for fitting the rotating shaft 5, and has six projections 57a which fit into the key grooves 5c of the rotating shaft 5. The long hole 58 is formed so as to extend in a direction inclined with respect to the straight line DL on the radially outer side of the shaft hole 57. The long hole 58 allows elastic deformation of the peripheral region of the protrusion 57a ​​when the rotating shaft 5 is fitted into the shaft hole 57. This allows the fitting operation of the rotating shaft 5 to be performed smoothly.

[0056] The six permanent magnets 60 are formed in the same shape as flat plates having a rectangular cross section that is elongated in the vertical direction Pd, as shown in Figures 10, 14, and 15. The six permanent magnets 60 are oriented so that their N poles and S poles face each other in the radial direction (direction of straight line DL) of the rotor core 50, and are inserted at equal intervals in the circumferential direction about the axis S so that the poles facing outward alternate. The permanent magnets 60 are inserted into the insertion holes 51 of the rotor core 50 with gaps G provided at both ends in the vertical direction Pd.

[0057] Here, since the gap G is provided on both sides of the permanent magnet 60, it is possible to prevent the magnetic field lines from short-circuiting themselves from the north pole to the south pole of the permanent magnet 60. Furthermore, since one permanent magnet 60 having a simple flat plate-like shape is arranged in correspondence with one outer peripheral magnetic pole portion 53, it is possible to achieve a simplified structure and reduced costs compared to a configuration in which a permanent magnet having a curved shape is arranged in correspondence with one outer peripheral magnetic pole portion 53, or a configuration in which multiple permanent magnets are arranged in correspondence with one outer peripheral magnetic pole portion 53.

[0058] In the embedded permanent magnet motor M having the above configuration, the operation of fitting the stator St into the housing body 1 will be described with reference to FIGS. First, the housing body 1 and the stator St are prepared as shown in Fig. 17. The stator St is formed by fitting the bobbin 30 into the stator core 20 and winding the coil 40 around the bobbin 30.

[0059] Here, the rolling direction Rd (straight line L2) of the steel plate Sp constituting the stator core 20 is oriented so as to be aligned with the expansion direction Ed (direction of the orthogonal line L) of the housing body. This orientation is preferably such that the expansion direction Ed (orthogonal line L) and the rolling direction Rd (straight line L2) completely coincide with each other, but is not limited thereto, and there is a certain tolerance range for positional deviation. For example, as shown in FIG. 12, it is acceptable for the direction to be shifted clockwise or counterclockwise by an angle θ with respect to the straight line L2, that is, within the range of an angle 2θ. In this embodiment, the angle θ is about 40°.

[0060] Next, the housing body 1 is heated to a predetermined temperature. After that, as shown in Fig. 18, the stator core 20 is inserted into the fitting recess 1b in the direction of the axis S. Then, as shown in Fig. 19, the stator St is completely inserted to a predetermined depth into the fitting recess 1b of the housing body 1, and is cooled to room temperature after a predetermined time has passed, whereby the stator St is fixed in the fitting recess 1b in a tight fit state.

[0061] As described above, the stator St is shrink-fitted into the housing body 1 with the rolling direction Rd of the steel plate Sp oriented in the expansion direction Ed in which the amount of change in the inner diameter of the fitting recess 1b is large when the housing body 1 serving as a housing is heated. As a result, when the stator St is cooled to room temperature after shrink-fitting, a uniform compressive stress σ acts on the stator St (stator core 20) from the housing body 1 around the fitting recess 1b, as shown in Fig. 20. Therefore, localized stress concentration in the housing body 1 and the stator core 20 can be suppressed or prevented.

[0062] As described above, the permanent magnet embedded motor M having the above-mentioned configuration includes a stator St including a stator core 20 formed in a circular ring shape by stacking a plurality of steel plates Sp obtained by punching a rolled steel plate material Rm and an excitation coil 40, a rotor Rt arranged inside the stator St and including a permanent magnet 60, and a metal housing (housing body 1) including a cylindrical fitting recess 1b centered on a predetermined axis S into which the stator St is fitted, and the stator St is shrink-fitted into the housing (housing body 1) with the rolling direction Rd of the steel plates Sp oriented in the expansion direction Ed in which the amount of change in the inner diameter of the fitting recess 1b is large when the housing (housing body 1) is heated. This makes it possible to suppress or prevent the occurrence of localized stress (stress concentration) and obtain a robust structure without increasing processing costs or complicating and enlarging the structure of the housing. Furthermore, when the embedded permanent magnet motor M having the above-described configuration is applied as a drive source for a pump device, a highly reliable pump device can be obtained without risk of damage or the like. The operation of the embedded permanent magnet motor M having the above configuration is similar to that of a conventional embedded permanent magnet motor, so a description thereof will be omitted here.

[0063] In the above embodiment, the expansion direction in which the amount of change in the inner diameter of the mating recess when the housing is heated is the flange portion 1h formed around the mating recess 1b and the two boss portions 1j1, 1j2 that are thicker than the wall portion 1b2 that defines the mating recess 1b and are arranged in the direction of the orthogonal line L perpendicular to the axis S in the flange portion 1h close to the periphery of the mating recess 1b, and are defined as the arrangement direction of the two boss portions 1j1, 1j2, but this is not limited to this.

[0064] For example, as shown in FIG. 21, a configuration may be adopted in which a housing main body 100 forming part of the housing includes a wall portion 1b2 defining the mating recess 1b, two thick portions 101 that are continuous with the periphery of the wall portion 1b2 on the opening side of the mating recess 1b and are formed to be thicker than the wall portion 1b2, an opening end surface 102, etc., and a motor cover and a board cover (not shown) are formed to fit and be fixed to the opening end surface 102 of the housing main body 100. Here, the two thick portions 101 are, for example, fitted into recesses of an application object, and serve to position and fix the housing (housing body 100) at a predetermined position on the application object. In the above configuration, the expansion direction Ed, in which the amount of change in the inner diameter of the fitting recess 1b is large when the housing body 100 is heated, coincides with the angular position about the axis S at which the cross-sectional area of ​​the thick-walled portion 101 is the largest in a cross section including the axis S, i.e., the angular position of the cross section shown in Figure 21. In this way, as long as the configuration includes a thick portion that is continuous with the periphery of the wall portion 1b2 that defines the fitting recess 1b and is formed thicker than the wall portion 1b2, the thick portion is not limited to a boss portion and may have other shapes. In short, various other configurations can be adopted as long as the configuration has a volume that specifies the expansion direction in which the amount of change in the inner diameter of the fitting recess when the housing is heated is large.

[0065] In the above embodiment, as an embedded permanent magnet motor having a stator including a plurality of teeth and slots arranged in the circumferential direction, and a rotor including a plurality of insertion holes arranged in the circumferential direction and a plurality of permanent magnets inserted into each of the insertion holes, a permanent magnet embedded motor M has been shown that has a stator St including nine teeth 22 and slots 23 and a rotor Rt including six insertion holes 51 (i.e., six permanent magnets 60), i.e., the rotor Rt has six magnetic poles and the stator St has nine teeth and slots. However, the present invention is not limited to the above configuration, and can be similarly applied to embedded permanent magnet motors having other configurations that satisfy the condition that the number of magnetic poles of the rotor is 2n (n is a natural number) and the number of teeth and slots of the stator is 3n (n is a natural number), as well as to specifications that deviate from the above conditions.

[0066] In the above embodiment, a trochoid pump is used as the pump unit in a pump device driven by a permanent magnet embedded motor M, but this is not limited to this and a vane pump or other type of pump may also be used.

[0067] As described above, the embedded permanent magnet motor of the present invention can suppress or prevent the occurrence of localized stress (stress concentration) and can obtain a robust structure without incurring increased processing costs or complicated and large housing structures, and is therefore useful not only as a drive source for pump equipment but also as a drive source for a variety of other devices. [Explanation of symbols]

[0068] S axis 1 Housing body (housing) 1b Fitting recess 1b1 mating surface 1b2 wall 1h Flange 1j1, 1j2 Two bosses (two thick sections) 1j3, 1j4 boss part L Orthogonal line (arrangement direction) Ed Expansion direction 1k Multiple cutouts 2 Pump cover 2a Inlet 2b Outlet 3 Motor cover 4 Circuit Board Cover 5 Rotation Axis U Pump Unit (Trochoid Pump) 11 Inner rotor (trochoid pump) 12 Outer rotor (trochoid pump) M Permanent magnet embedded motor (drive source) St stator 20 Stator core 22 Teeth 23 Slots Rm Rolled steel plate material SP steel plate Rd Rolling direction Ma central area (index) ML Marker (Indicator) 30 Bobbin 40 Coil Rt Rotor 50 Rotor core 51 Insertion hole 52 V-groove recess 53 Outer magnetic pole part 54 Filling hole 55 Through hole 60 Permanent Magnets G void 100 Housing body (housing) 101 Thick part

Claims

1. a stator including a stator core formed in an annular shape by laminating a plurality of steel plates obtained by punching a rolled steel plate material and an excitation coil; a rotor disposed inside the stator and including a permanent magnet; a metal housing including a cylindrical fitting recess centered on a predetermined axis into which the stator is fitted; The stator is shrink-fitted into the housing with the rolling direction of the steel plate oriented in an expansion direction in which the amount of change in the inner diameter of the fitting recess is large when the housing is heated. A permanent magnet embedded motor.

2. the housing includes a wall portion defining the fitting recess, and a thick portion that is continuous with a periphery of the wall portion on an opening side of the fitting recess and is formed to be thicker than the wall portion, The expansion direction corresponds to an angular position around the axis at which a cross-sectional area of ​​the thick portion is maximized in a cross section including the axis.

2. The permanent magnet embedded motor according to claim 1 .

3. the housing includes a wall portion defining the fitting recess, and two thick portions formed continuously around the wall portion on an opening side of the fitting recess in a direction perpendicular to the axis, the thick portions being thicker than the wall portion, The stator is shrink-fitted to the housing with the rolling direction oriented in the arrangement direction of the two thick portions.

2. The permanent magnet embedded motor according to claim 1 .

4. the housing includes a wall portion defining the fitting recess, a flange portion formed around the wall portion on an opening side of the fitting recess, and two boss portions arranged in the flange portion in a direction perpendicular to the axis and having a thickness greater than that of the wall portion, The stator is shrink-fitted into the housing body with the rolling direction oriented in the arrangement direction of the two boss portions.

2. The permanent magnet embedded motor according to claim 1 .

5. The flange portion is formed to be thicker than the wall portion.

5. The permanent magnet embedded motor according to claim 4.

6. The two boss portions are formed to be thicker than the flange portion.

6. The permanent magnet embedded motor according to claim 5.

7. The flange portion includes a plurality of hollow portions in an area outside the area through which the orthogonal line passes.

6. The permanent magnet embedded motor according to claim 5.

8. The stator includes an indicator indicating the rolling direction.

2. The permanent magnet embedded motor according to claim 1 .

9. The thickness of the steel plate is 0.2 mm to 0.5 mm.

2. The permanent magnet embedded motor according to claim 1 .

10. The housing is made of an aluminum material.

2. The permanent magnet embedded motor according to claim 1 .

11. The stator core has teeth and slots arranged in a circumferential direction, The stator includes the coil wound around the teeth via a resin bobbin.

2. The permanent magnet embedded motor according to claim 1 .

12. The rotor includes a cylindrical rotor core formed by stacking a plurality of steel plates obtained by punching a rolled steel plate material and having insertion holes arranged in the circumferential direction, and the permanent magnets are inserted into the insertion holes.

12. The permanent magnet embedded motor according to claim 1, wherein the rotor is a rotor having a first end and a second end.

13. A pump unit that draws in and discharges a fluid; A rotating shaft connected to the pump unit; A pump device including: The driving source is a permanent magnet embedded motor according to claim 12. A pump device characterized in that

14. The pump unit is a trochoid pump including an inner rotor to which the rotating shaft is connected and an outer rotor that meshes with the inner rotor.

14. The pump device according to claim 13.

Images