Electric motor mounting structure

Abstract

To provide a mounting structure of an electric motor capable of suppressing occurrence of resonance by an annular vibration mode and stably fastening a stator core.SOLUTION: A mounting structure of a motor 20 includes: a stator core 32 that has a cylindrical shape with an axis line C as a center and in which a plurality of teeth 36 are provided on an inner peripheral portion 32i and a plurality of holes 44 are provided at an equal angular interval with the axis line C as a center on an outer peripheral portion 32o. (a) The stator core 32 is fastened to a case 90 by bolts 80 inserted respectively through at least three fastening holes 44x among the plurality of holes 44. (b) By respective different fastened states between the stator core 32 and the case 90 by the bolts 80, radial rigidity of the stator core 32 attached to the case 90, symmetry around the axis line C is broken. (c) A polygon formed by connecting the fastening holes 44x each other when viewed in a direction of the axis line C includes the axis line C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a structure for mounting an electric motor to a non-rotating member. [Background technology]

[0002] If the number of magnetic poles of the rotor matches the number of bolts fastening the stator core to the case, which is a non-rotating member, the stator core is likely to resonate due to the influence of electromagnetic force during rotor rotation. For this reason, a mounting structure for an electric motor is known that suppresses the occurrence of resonance by making the number of magnetic poles of the rotor and the number of bolts fastening the stator core different from each other. For example, the structure described in Patent Document 1 is one such example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-280249 Summary of the Invention [Problem to be solved by the invention]

[0004] In the mounting structure for an electric motor described in Patent Document 1, bolts are inserted through all of the multiple holes provided at equal angular intervals on the outer periphery of the stator core. Therefore, the radial stiffness of the stator core fastened to the case has a periodic characteristic in which the stiffness is equal at equal angular intervals in the circumferential direction. When the radial stiffness of the stator core is periodic in the circumferential direction, there is a risk of resonance due to a circular vibration mode. Furthermore, the stator core must be stably fastened to the case with bolts.

[0005] The present invention has been made in light of the above circumstances, and its object is to provide a mounting structure for an electric motor that can suppress the occurrence of resonance due to the circular vibration mode and can stably fasten the stator core. [Means for solving the problem]

[0006] The gist of the present invention is to It is made up of multiple electromagnetic steel sheets stacked in the thickness direction, A cylindrical shape with an axis as its center, with a plurality of teeth on the inner periphery and a The electromagnetic steel plate is penetrated in the direction of the axis. An electric motor having a stator core in which a plurality of holes are provided at equal angular intervals around the axis, To the case The mounting structure includes: (a) a bolt passing through each of at least three fastening holes among the plurality of holes, and the stator core is secured to the mounting structure; The aforementioned (b) the stator core is fastened to a case, and since the rigidity at the multiple fastening points on the case where the stator core is fastened with the bolts is different, the symmetry of the radial rigidity of the stator core around the axis when attached to the case is lost, (c) the polygon formed by connecting adjacent fastening holes when viewed in the axial direction includes the axis, and (d) at least one of the thicknesses at the multiple fastening points on the case and the radial lengths of the thickened areas at the multiple fastening points on the case is different for each of the multiple fastening points. [Effects of the Invention]

[0007] According to the mounting structure of the electric motor of the present invention, (a) the stator core is secured by bolts inserted through at least three fastening holes among the plurality of holes. The aforementioned (b) the stator core is fastened to a case, and since the rigidity at the multiple fastening points on the case where the stator core is fastened with the bolts is different, the symmetry of the radial rigidity of the stator core when attached to the case is lost around the axis, (c) the polygon formed by connecting adjacent fastening holes when viewed in the axial direction includes the axis, and (d) at least one of the thicknesses at the multiple fastening points on the case and the radial lengths of the thickened areas at the multiple fastening points on the case is different for each of the multiple fastening points. As a result, in an electric motor in which a stator core is formed by stacking a plurality of electromagnetic steel sheets in the thickness direction, has a cylindrical shape centered on the axis, has a plurality of teeth provided on the inner periphery, and has a plurality of holes penetrating the electromagnetic steel sheets in the axial direction on the outer periphery at equal angular intervals around the axis, and is fastened to a case by bolts inserted through at least three fastening holes among the plurality of holes,As shown in (b) above, the symmetry of the radial rigidity of the stator core around the axis is broken, and as shown in (c) above, the polygons formed by connecting adjacent fastening holes when viewed in the axial direction include the axis. So The occurrence of resonance due to the circular vibration mode is suppressed, and the stator core is stably fastened to the case. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are cross-sectional views of a mounting structure for a motor to a case according to a first embodiment, where FIG. 1A is a cross-sectional view in the radial direction, and FIG. 1B is a cross-sectional view in the axial direction. [Figure 2] 1A to 1D are diagrams showing circular vibration modes of integer orders, where (a) is a diagram explaining the second vibration mode, (b) is a diagram explaining the third vibration mode, (c) is a diagram explaining the fourth vibration mode, and (d) is a diagram explaining the fifth vibration mode. [Figure 3] 1A and 1B are diagrams illustrating the radial rigidity of a stator core fastened to a case, in which (a) shows a case in which three fastening holes are arranged symmetrically about a line passing through the axis when viewed in the axial direction, (b) shows a case in which four fastening holes are arranged symmetrically about a line passing through the axis when viewed in the axial direction, and (c) shows a case in which the angular intervals around the axis between adjacent fastening holes when viewed in the axial direction are all the same. [Figure 4] 10A and 10B are cross-sectional views of a mounting structure for a motor to a case according to a second embodiment, where FIG. 10A is a cross-sectional view in the radial direction, and FIG. 10B is a cross-sectional view in the axial direction. [Figure 5] 10A and 10B are cross-sectional views of a mounting structure for a motor to a case according to a third embodiment, where FIG. 10A is a cross-sectional view in the radial direction, and FIG. 10B is a cross-sectional view in the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. Note that in each embodiment, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of each part are not necessarily accurately depicted. In this specification, the "direction parallel to the axis C," the "radial direction of the stator core," and the "circumferential direction of the stator core" will be simply referred to as the "axis C direction," the "radial direction," and the "circumferential direction," respectively. [Example]

[0010] 1A and 1B are cross-sectional views of a mounting structure for an electric motor 20 to a case 90 according to a first embodiment, where (a) is a radial cross-sectional view and (b) is a cross-sectional view in the direction of the axis C. Note that FIG. 1 shows an example in which an electric motor 20 is fastened to a case 90 in the manner shown in FIG. 3A, which will be described later, and FIG. 1B is a cross-sectional view taken along the cutting line 1b-1b shown in FIG. 1A. The case 90 and bolts 80 are not shown in FIG. 1A.

[0011] The electric motor 20 is a rotating electric machine that functions as an electric motor (motor) and a generator (generator) mounted on the vehicle 10, such as a hybrid vehicle or an electric vehicle. The electric motor 20 is, for example, a driving power source for the vehicle 10 to run.

[0012] The axis C is the rotation center line of the rotor 60. For example, the electric motor 20 is an AC-driven interior permanent magnet motor (IPM motor) that includes a cylindrical stator 30 centered on the axis C and a rotor 60 disposed on the inner periphery of the stator 30.

[0013] The stator 30 includes a stator core 32 and a winding (not shown) wound around the stator core 32 .

[0014] The stator core 32 is cylindrical and centered on the axis C, and is formed by laminating, for example, a plurality of electromagnetic steel sheets 50. A plurality (48 in this embodiment) of grooves, i.e., slots 38, having a depth extending radially outward and penetrating in the direction of the axis C, are provided in the inner circumferential portion 32i of the stator core 32 at equal angular intervals (at equal angular intervals of 2π / 48 rad in this embodiment). Teeth 36 are formed between adjacent slots 38. When an alternating current is applied to the winding, the teeth 36 act as electromagnets and generate a rotating magnetic field. Thus, the stator core 32 has a plurality of teeth 36 on its inner circumferential portion 32i.

[0015] The yoke 34 is a portion of the stator core 32 other than the tooth portions 36, and serves as a path for magnetic lines of force between the tooth portions 36 that have become electromagnets.

[0016] The outer circumferential portion 32o of the stator core 32 is provided with a plurality of holes 44 penetrating in the direction of the axis C. As viewed in the direction of the axis C, positions Pa to Ph, which are the centers of the plurality of holes 44, are equiangularly spaced (2π / 8 [rad] in this embodiment) around the axis C and are eight locations that are point-symmetrical about the axis C. The radial distance from the axis C to each of the positions Pa to Ph is the same. Each of the plurality of holes 44 is a cylindrical hole 44a to 44h having the same diameter centered on the positions Pa to Ph. Similarly, hereinafter, the reference numerals for the configurations corresponding to the positions Pa to Ph will be suffixed with letters a to h, respectively. In this manner, each of the plurality of holes 44 has the same shape. The plurality of holes 44 is provided in a protruding portion 40. The protruding portion 40 protrudes partially radially outward from the outer circumferential portion 32o of the stator core 32 and extends in the direction of the axis C. The holes 44 are open at one end surface 32a and the other end surface 32b of the stator core 32 in the direction of the axis C, respectively.

[0017] The case 90 is a non-rotating member. The case 90 is made of an aluminum alloy, for example, by casting. The case 90 is, for example, a cylindrical case with a bottom, and is a transmission case (= a case that houses a vehicle transmission) that houses the stator 30 and rotor 60 of the electric motor 20 inside. The inner surface of the case 90 is provided with a mounting surface 92 to which the electric motor 20 is attached. The mounting surface 92 is provided with a plurality of holes 94, and the plurality of holes 94 are provided at positions corresponding to the plurality of holes 44. The case 90 corresponds to the "non-rotating member" in this invention.

[0018] Here, the term "fastening hole 44x" refers to one of the multiple holes 44 through which the bolt 80 is inserted to fasten the stator core 32 to the case 90, and the term "dummy hole 44y" refers to one of the multiple holes 44 through which the bolt 80 is not inserted to fasten the stator core 32 to the case 90. The term "locking hole 94x" refers to one of the multiple holes 94 that is provided to correspond to the position of the fastening hole 44x, and the term "non-locking hole 94y" refers to one of the multiple holes 94 that is provided to correspond to the position of the dummy hole 44y. A female thread is formed on the inner circumferential surface of each of the locking holes 94x. The "locking hole 94x" is a fastening point on the case 90 where the stator core 32 is fastened with the bolt 80.

[0019] In this embodiment, the fastening holes 44x are holes 44a, 44d, and 44f, and the dummy holes 44y are holes 44b, 44c, 44e, 44g, and 44h. The locking holes 94x are holes 94a, 94d, and 94f, and the non-locking holes 94y are holes 94b, 94c, 94e, 94g, and 94h. In FIG. 1(a), the fastening holes 44x are indicated by diagonal lines. There are at least three pairs of fastening holes 44x and locking holes 94x. When viewed from the axis C direction, a polygon (= an area surrounded by the sides of the polygon and including the sides) formed by connecting adjacent fastening holes 44x includes the axis C. Because the polygon includes the axis C, which is the center of gravity of the electric motor 20 when viewed from the axis C direction, the stator core 32 is stably fastened to the case 90 by the bolts 80 inserted through the fastening holes 44x.

[0020] Now, the circular vibration mode will be described.

[0021] As described above, when the electric motor 20 is driven by an alternating current, each tooth 36 acts as an electromagnet and generates a rotating magnetic field. The rotor 60 is then attracted to or repelled by the rotating magnetic field, causing the rotor 60 to rotate. Meanwhile, a radial electromagnetic force acts on the stator core 32 due to the force received from the rotor 60. The radial electromagnetic force acting on the stator core 32 causes the stator core 32 to vibrate in the radial direction. This radial vibration (resonance) of the stator core 32 includes integer-order circular vibration modes.

[0022] 2 is a diagram showing circular vibration modes of integer orders, where (a) is a diagram explaining the second vibration mode (=when the integer order is "2"), (b) is a diagram explaining the third vibration mode (=when the integer order is "3"), (c) is a diagram explaining the fourth vibration mode (=when the integer order is "4"), and (d) is a diagram explaining the fifth vibration mode (=when the integer order is "5") In Fig. 2, a schematic diagram showing the state of a radial cross section of stator core 32 at one point in time and a schematic diagram of the state of a radial cross section of stator core 32 at another point in time are shown by solid lines and two-dot chain lines, respectively.

[0023] In resonance due to the circular vibration mode, web portions where the stator core 32 expands or contracts in the radial direction and nodes where the stator core 32 hardly expands or contracts in the radial direction appear periodically in the circumferential direction. The web portions are regions where the stator core 32 experiences large radial vibrations, and the nodes are regions where the stator core 32 experiences smaller radial vibrations than the web portions. The number of web portions and nodes is twice the integer order in the circular vibration mode. In addition, in any circular vibration mode of integer orders, the web portions and nodes are located at point-symmetric positions about the axis C. Note that, in the case where the integer order is an even number, such as the second-order vibration mode and the fourth-order vibration mode, when the state of the radial cross section of the stator core 32 is rotated by π [rad] about the axis C, the web portions where the stator core 32 expands in the radial direction and the nodes where the stator core 32 contracts in the radial direction coincide with each other. When the integer order is odd, such as in the third vibration mode and the fifth vibration mode, when the radial cross section of the stator core 32 is rotated by π [rad] around the axis C, the part of the abdomen where the stator core 32 expands radially coincides with the part where the stator core 32 contracts radially.

[0024] In the stator core 32 attached to the case 90, the radial rigidity is relatively high at the positions of the fastening holes 44x fastened with the bolts 80, and the radial rigidity is relatively low at the positions of the dummy holes 44y not fastened with the bolts 80. This is because, when the stator core 32 is fastened to the case 90 with the bolts 80, the stator core 32 is less likely to deform at the positions fastened to the case 90 compared to the positions not fastened to the case 90.

[0025] For example, if the radial stiffness at each of the fastening holes 44x is the same and the radial stiffness of the stator core 32 when attached to the case 90 is periodic in the circumferential direction, resonance due to a circular vibration mode corresponding to the circumferential periodicity of the radial stiffness of the stator core 32 is likely to occur.

[0026] For example, if the radial rigidity at the fastening holes 44x is the same and the radial rigidity of the stator core 32 when attached to the case 90 is symmetrical with respect to any line passing through the axis C, resonance due to an integer-order circular vibration mode is likely to occur in which the abdomen and nodes are positioned point-symmetrically around the axis C.

[0027] Figure 3 is a diagram explaining the radial rigidity of the stator core 32 fastened to the case 90, where (a) shows a case where three fastening holes 44x are arranged symmetrically with respect to a line CL1 passing through the axis C when viewed in the direction of the axis C, (b) shows a case where four fastening holes 44x are arranged symmetrically with respect to a line CL2 passing through the axis C when viewed in the direction of the axis C, and (c) shows a case where four fastening holes 44x are arranged such that the angular intervals between adjacent fastening holes 44x around the axis C are all the same when viewed in the direction of the axis C.

[0028] In this embodiment, the fastening state between the stator core 32 and the case 90 by the bolts 80 differs for each fastening location. "Different fastening states" means that when the stator core 32 is fastened to the case 90 by the bolts 80, the fastening states result in different radial rigidities of the stator core 32 attached to the case 90. For example, the bolts 80 inserted through the fastening holes 44x have substantially the same configuration (same material), but the outer diameters D [mm] of the shanks 82 of the bolts 80 are different, or the axial forces (= tightening forces) F [N] of the bolts 80 when the stator core 32 is attached to the case 90 are different. Note that the bolts 80 each have, for example, a shank 82 that can be inserted into the fastening hole 44x and a head that has a diameter larger than the diameter of the fastening hole 44x and is provided on one end of the shank 82.

[0029] Next, an example will be described in which the outer diameter D of the shank 82 of the bolt 80 is different for each fastening point. In accordance with the different outer diameters D, the diameters of the locking holes 94x are also different.

[0030] In the example shown in FIG. 3(a), of the multiple holes 44, holes 44a, 44d, and 44f are designated as fastening holes 44x, and holes 44b, 44c, 44e, 44g, and 44h are designated as dummy holes 44y. Here, the outer diameters D of bolts 80a, 80d, and 80f inserted through fastening hole 44x are designated as outer diameters Da, Dd, and Df, respectively. Of the outer diameters Da, Dd, and Df, outer diameter Df is the largest, outer diameter Dd is the smallest, and outer diameter Da is a value between them. Here, the radial rigidity moduli G at the respective positions of the fastening holes 44x in the stator core 32 attached to the case 90 are designated as rigidity moduli Ga, Gd, and Gf, respectively. The rigidity modulus G is a physical property that indicates resistance to deformation; the higher the rigidity modulus G, the more resistant to deformation. As the outer diameter D of the bolt 80 increases, the bolt 80 becomes more resistant to deformation and the modulus of rigidity G increases. Therefore, among the moduli of rigidity Ga, Gd, and Gf, Gf is the highest, Gd is the lowest, and Ga is an intermediate value. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 is lost about the axis C. "Symmetry is lost about the axis C" means that the symmetry is not periodic in the circumferential direction and is not line-symmetric about any line passing through the axis C. For example, the moduli of rigidity G are different between one side and the other side of the line CL1 passing through the axis C shown in FIG. 3(a), resulting in a loss of symmetry.

[0031] In the example shown in FIG. 3(b), of the multiple holes 44, holes 44a, 44c, 44f, and 44h are designated as fastening holes 44x, and holes 44b, 44d, 44e, and 44g are designated as dummy holes 44y. Here, the outer diameters D of bolts 80a, 80c, 80f, and 80h inserted through fastening hole 44x are designated as outer diameters Da, Dc, Df, and Dh, respectively. Of the outer diameters Da, Dc, Df, and Dh, outer diameter Dh is the largest, outer diameter Da is the second largest, outer diameter Df is the third largest, and outer diameter Dc is the smallest. Here, the radial rigidity moduli G at the respective positions of fastening holes 44x in stator core 32 attached to case 90 are designated as rigidity moduli Ga, Gc, Gf, and Gh, respectively. Of the moduli of rigidity Ga, Gc, Gf, and Gh, Gh is the highest, Ga is the second highest, Gf is the third highest, and Gc is the lowest. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 is lost about the axis C. For example, the moduli of rigidity G are different between one side and the other side of the line CL2 passing through the axis C shown in FIG. 3(b), resulting in a loss of symmetry.

[0032] In the example shown in FIG. 3(c), of the multiple holes 44, holes 44a, 44c, 44e, and 44g are designated as fastening holes 44x, and holes 44b, 44d, 44f, and 44h are designated as dummy holes 44y. The outer diameters D of bolts 80a, 80c, 80e, and 80g inserted through fastening hole 44x are designated as Da, Dc, De, and Dg, respectively. Of the outer diameters Da, Dc, De, and Dg, Dg is the largest, Da is the second largest, De is the third largest, and Dc is the smallest. The radial rigidity moduli G at the respective positions of fastening holes 44x in stator core 32 attached to case 90 are designated as Ga, Gc, Ge, and Gg, respectively. Of the moduli of rigidity Ga, Gc, Ge, and Gg, Gg is the highest, Ga is the second highest, Ge is the third highest, and Gc is the lowest. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 is lost about the axis C. For example, the moduli of rigidity G are different on one side and the other side of the line CL3 and the line CL4 passing through the axis C shown in FIG. 3(c), resulting in a loss of symmetry.

[0033] Next, an example will be described in which the axial force F of the bolt 80 varies depending on the fastening location.

[0034] First, the case shown in FIG. 3(a) will be described. Here, the axial forces F of the bolts 80a, 80d, and 80f inserted through the fastening holes 44x are respectively designated as Fa, Fd, and Ff. Of the axial forces Fa, Fd, and Ff, Ff is the largest and Fd is the smallest, with the axial force Fa being a value between them. The larger the axial force F of the bolt 80, the more difficult it is to deform and the higher the rigidity G. Therefore, of the rigidity moduli Ga, Gd, and Gf, Gf is the largest and Gd is the smallest, with the rigidity modulus Ga being a value between them. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 around the axis C is lost.

[0035] Next, the case shown in Fig. 3(b) will be described. Here, the axial forces F of the bolts 80a, 80c, 80f, and 80h inserted through the fastening holes 44x are designated as Fa, Fc, Ff, and Fh, respectively. Of the axial forces Fa, Fc, Ff, and Fh, the axial force Fh is the largest, the axial force Fa is the second largest, the axial force Ff is the third largest, and the axial force Fc is the smallest. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 around the axis C is lost.

[0036] Next, the case shown in Fig. 3(c) will be described. Here, the axial forces F of the bolts 80a, 80c, 80e, and 80g inserted through the fastening holes 44x are respectively designated as axial forces Fa, Fc, Fe, and Fg. Of the axial forces Fa, Fc, Fe, and Fg, the axial force Fg is the largest, the axial force Fa is the second largest, the axial force Fe is the third largest, and the axial force Fc is the smallest. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 around the axis C is lost.

[0037] In this embodiment, since the fastening states between the stator core 32 and the case 90 by the bolts 80 inserted through the fastening holes 44x are different, the symmetry of the radial rigidity of the stator core 32 when attached to the case 90 around the axis C is lost.

[0038] According to this embodiment, (a) the stator core 32 is fastened to the case 90 by bolts 80 inserted through three or four fastening holes 44x of the plurality of holes 44, (b) the fastening states of the stator core 32 and the case 90 by the bolts 80 are different from one another, so that the symmetry about the axis C is lost in the radial rigidity of the stator core 32 when attached to the case 90, and (c) the polygons formed by connecting adjacent fastening holes 44x when viewed in the direction of the axis C include the axis C. As in (b) above, the symmetry about the axis C is lost in the radial rigidity of the stator core 32, and as in (c) above, the polygons formed by connecting adjacent fastening holes 44x when viewed in the direction of the axis C include the axis C. This suppresses the occurrence of resonance due to the circular vibration mode compared to when the fastening state between the stator core 32 and the case 90 by the bolt 80 inserted through the fastening hole 44x is the same, and the stator core 32 is stably fastened to the case 90.

[0039] According to this embodiment, when the arrangement of the fastening holes 44x is symmetrical with respect to a line passing through the axis C (for example, lines CL1 to CL4) as viewed in the direction of the axis C, the fastening states of the stator core 32 and the case 90 by the bolts 80 are different, and therefore the symmetry about the axis C is lost in the radial rigidity of the stator core 32 in a state attached to the case 90. This suppresses the occurrence of resonance due to the circular vibration mode and allows the stator core 32 to be stably fastened to the case 90.

[0040] According to this embodiment, either the outer diameter D of the bolts 80 inserted through the fastening holes 44x or the axial force F of the bolts 80 inserted through the fastening holes 44x is different, which results in different fastening states between the stator core 32 and the case 90 by the bolts 80. The fastening state can be made different with a simple configuration such as varying the outer diameter D of the bolts 80 or varying the axial force F of the bolts 80, thereby suppressing the occurrence of resonance due to the circular vibration mode and stably fastening the stator core 32 to the case 90. [Example]

[0041] 4A and 4B are cross-sectional views of the mounting structure of the electric motor 20 to the case 190 according to the second embodiment, where (a) is a radial cross-sectional view and (b) is a cross-sectional view along the axis C. The mounting structure of the electric motor 20 to the case 190 according to this embodiment is substantially the same as the mounting structure of the electric motor 20 to the case 90 according to the first embodiment. Therefore, the following description will focus on the parts of this embodiment that are different from the first embodiment, and parts that are substantially the same in function as the first embodiment will be denoted by the same reference numerals and will not be described as appropriate.

[0042] Fig. 4 shows an example in which the electric motor 20 is fastened to the case 190 with the fastening holes 44x positioned in the same manner as in Fig. 3(a), and Fig. 4(b) is a cross-sectional view taken along the cutting line 4b-4b shown in Fig. 4(a). In Fig. 4(a), the case 190 and the bolts 180 are not shown.

[0043] In this embodiment, the case 90 and the bolt 80 in the first embodiment are replaced with a case 190 and a bolt 180, respectively. The outer diameter D of the shaft portion 182 of the bolt 180 inserted through each of the fastening holes 44x is the same. The locking holes 194x provided in the case 190 are located in the same positions as the locking holes 94x in the first embodiment, and the diameters of the locking holes 194x are all the same.

[0044] For example, the thickness TH [mm] in the direction of axis C at the fastening points of case 190 (hereinafter referred to as "thickness TH") varies, and the radial length L [mm] of the region where the thickness at the fastening points of case 190 is thicker than the surrounding area (hereinafter referred to as "thick region") varies. For example, the difference in thickness TH and the radial length L of the thick region depends on the presence or absence of ribs formed on case 190 for reinforcement, etc.

[0045] Next, an example in which the wall thickness TH of the case 190 varies depending on the fastening location will be described.

[0046] First, a case where the position of the fastening hole 44x is the same as that shown in FIG. 3(a) will be described. Here, the thicknesses TH of the fastening points, i.e., the locking holes 194x, on the case 190 are respectively defined as thicknesses THa, THd, and THf. Furthermore, the radial lengths L of the thick-walled regions at the fastening points on the case 190 are respectively defined as lengths La, Ld, and Lf. Of the thicknesses THa, THd, and THf, THf is the thickest and THd is the thinnest, with THa being a value between them. Furthermore, of the lengths La, Ld, and Lf, Lf is the longest and Ld is the shortest, with La being a value between them. The thicker the thickness TH, the more difficult it is to deform and the higher the modulus of rigidity G. Furthermore, the longer the length L, the more difficult it is to deform and the higher the modulus of rigidity G. Therefore, of the moduli of rigidity Ga, Gd, and Gf, Gf is the highest and Gd is the lowest, with Ga being a value between them. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 90 with respect to the axis C as the center is lost.

[0047] Although not explained here, when the position of the fastening holes 44 is the same as that shown in Figure 3(b) or the same as that shown in Figure 3(c), by varying the thickness TH of the case 190 at each fastening point or varying the radial length L of the thick-walled region at each fastening point on the case 190, it is possible to break the symmetry of the radial rigidity of the stator core 32 attached to the case 190 around the axis C.

[0048] According to this embodiment, (a) the stator core 32 is fastened to the case 190 by the bolts 180 inserted through three or four fastening holes 44x out of the multiple holes 44, (b) the rigidity of the positions of the locking holes 194x in the case 190 to which the stator core 32 is fastened by the bolts 180 is different, which breaks the symmetry of the radial rigidity of the stator core 32 attached to the case 190 about the axis C, and (c) the polygon connecting the fastening holes 44x as viewed from the direction of the axis C includes the axis C. As a result, compared to when the rigidity of the positions of the locking holes 194x in the case 190 is the same, the occurrence of resonance due to the circular vibration mode is suppressed, and the stator core 32 is stably fastened to the case 190.

[0049] According to this embodiment, the thickness TH of each fastening point in case 190 and the radial length L of each thick-walled region in case 190 are different. By using the simple configuration of making the thickness TH of each fastening point in case 190 different and making the radial length L of each thick-walled region different, the symmetry of the radial rigidity of stator core 32 attached to case 190 about axis C is broken. This suppresses the occurrence of resonance due to the circular vibration mode and ensures that stator core 32 is stably fastened to case 190. [Example]

[0050] 5A and 5B are cross-sectional views of the mounting structure of the electric motor 20 to the case 290 according to the third embodiment, where (a) is a radial cross-sectional view and (b) is a cross-sectional view along the axis C. The mounting structure of the electric motor 20 to the case 290 according to this embodiment is substantially the same as the mounting structure of the electric motor 20 to the case 90 according to the first embodiment. Therefore, the following description will focus on the parts of this embodiment that are different from the first embodiment, and parts that are substantially the same in function as the first embodiment will be denoted by the same reference numerals and will not be described as appropriate.

[0051] Fig. 5(b) is a cross-sectional view taken along the line 5b-5b shown in Fig. 5(a). In Fig. 5(a), the case 290 and the bolt 280 are not shown.

[0052] In this embodiment, the case 90 and the bolt 80 in the first embodiment are replaced with a case 290 and a bolt 280, respectively. The outer diameter D of the shaft portion 282 of the bolt 280 inserted through the fastening hole 44x is all the same, and the axial force F of the bolt 280 when the stator core 32 is attached to the case 290 is all the same. Furthermore, the wall thickness TH of the case 290 at the fastening point, i.e., the position of the locking hole 294x, is all the same, and the radial length L of the thick-walled region at the position of the locking hole 294x is all the same.

[0053] In this embodiment, the fastening holes 44x are holes 44a, 44d, and 44e, and the dummy holes 44y are holes 44b, 44c, 44f, 44g, and 44h. The locking holes 294x are holes 294a, 294d, and 294e, and the non-locking holes 294y are holes 294b, 294c, 294f, 294g, and 294h. In Figure 5, the fastening holes 44x are indicated by diagonal lines.

[0054] When viewed from the direction of the axis C, the angular intervals (hereinafter simply referred to as "angular intervals") between adjacent fastening holes 44x about the axis C are different from one another. Specifically, the angular intervals between the hole 44a and the hole 44d, the angular intervals between the hole 44d and the hole 44e, and the angular intervals between the hole 44e and the hole 44a are 3 / 8π [rad], 1 / 8π [rad], and 4 / 8π [rad], respectively, which are all different from one another. As a result, the symmetry of the radial rigidity of the stator core 32 attached to the case 290 about the axis C is lost.

[0055] For example, if eight or more holes 44 are provided, and only three of the holes 44 are fastening holes 44x and the rest are dummy holes 44y, the stator core 32 can be stably fastened to the case 290 with the minimum number of bolts 280, that is, three, and the occurrence of resonance due to the circular vibration mode is suppressed compared to when the angular intervals between adjacent fastening holes 44x are the same when viewed in the direction of the axis C.

[0056] According to this embodiment, (a) the angular intervals between adjacent fastening holes 44x when viewed in the direction of the axis C are different from each other, (b) of the multiple holes 44, all holes other than the fastening holes 44x are dummy holes 44y, and (c) the polygons formed by connecting adjacent fastening holes 44x when viewed in the direction of the axis C include the axis C. This suppresses the occurrence of resonance due to the circular vibration mode and ensures that the stator core 32 is stably fastened to the case 290.

[0057] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0058] In the first, second, and third embodiments described above, the stator core 32 is fastened to the cases 90, 190, and 290 by the bolts 80, 180, and 280. However, the present invention is not limited to this, and the stator core 32 may be fastened by, for example, a combination of a bolt and a nut. Also, the cases 90, 190, and 290 may not be provided with the non-locking holes 94y and 294y, respectively.

[0059] In the above-described first embodiment, when the arrangement of the fastening holes 44x is line-symmetrical with respect to a line passing through the axis C (for example, lines CL1 to CL4) as viewed in the direction of the axis C, the fastening states of the stator core 32 and the case 90 by the bolts 80 are different from each other. However, the present invention is not limited to this, and may be, for example, as in the second embodiment, an embodiment in which the rigidity of the positions of the locking holes 94x in the case 90 is different from each other. In this way, when the arrangement of the fastening holes 44x is line-symmetrical with respect to a line passing through the axis C as viewed in the direction of the axis C, an embodiment in which at least one of the fastening states of the stator core 32 and the case 90 by the bolts 80 is different from each other and the rigidity at a plurality of fastening points in the case 90 is different from each other may be established.

[0060] In the above-mentioned Example 2, the thickness TH at each fastening point in the case 190 and the radial length L of each thick region in the case 190 are different, but the present invention is not limited to this, and may be, for example, a configuration in which either the thickness TH or the length L is different.

[0061] In the first embodiment described above, the symmetry about the axis C is broken in the radial rigidity of the stator core 32 when attached to each of the cases 90, 190, and 290 by varying the fastening states of the stator core 32 and the case 90 by the bolts 80, by varying the rigidity of the positions of the locking holes 194x in the case 190 to which the stator core 32 is fastened by the bolts 180, and by varying the angular intervals between adjacent fastening holes 44x when viewed from the axis C in the third embodiment. However, the present invention is not limited to this. For example, by combining the above-described varying the fastening states, varying the rigidity of the positions of the locking holes in the case, and varying the angular intervals between adjacent fastening holes 44x, the symmetry about the axis C may be broken in the radial rigidity of the stator core 32 when attached to the case.

[0062] It should be noted that the above-described embodiments are merely examples of the present invention, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art, without departing from the spirit of the present invention. [Explanation of symbols]

[0063] 20: motor, 32: stator core, 32i: inner circumference, 32o: outer circumference, 36: teeth, 44: multiple holes, 44x: fastening hole, 44y: dummy hole, 80, 180, 280: bolt, 90, 190, 290: case (non-rotating member), 94, 194, 294: multiple holes (multiple fastening points), C: axis, CL1 to CL4: line (any line passing through the axis), D: outer diameter, F: axial force, L: length, TH: thickness

Claims

[Claim 1] A mounting structure for a case of an electric motor having a stator core which is constructed by stacking a plurality of electromagnetic steel sheets in the thickness direction, has a cylindrical shape centered on an axis, has a plurality of teeth on the inner periphery, and has a plurality of holes on the outer periphery that penetrate the electromagnetic steel sheets in the direction of the axis and are arranged at equal angular intervals around the axis, the stator core is fastened to the case by bolts inserted through at least three fastening holes among the plurality of holes, Since the rigidity of a plurality of fastening points in the case to which the stator core is fastened with the bolts is different from one another, the symmetry of the radial rigidity of the stator core attached to the case around the axis is lost, A polygon formed by connecting the fastening holes adjacent to each other when viewed in the axial direction includes the axis, At least one of the thickness of each of the plurality of fastening points in the case and the length in the radial direction of each of the thick-walled regions in the case at the plurality of fastening points is different for each of the plurality of fastening points. A mounting structure for an electric motor.

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