Electric motor mounting structure and electric motor mounting method

Abstract

To provide an attachment structure of a dynamo-electric motor, capable of suppressing the generation of a resonator by an annulus ring vibration mode of an integer number and a dimension number, and provide an attachment method of the dynamo-electric motor.SOLUTION: In an attachment structure of a dynamo-electric motor 20, (a) a fastening hole 44x is provided to any one of a first position group POS1 to which an element number is applied and a second position group POS2 to which other than the element number is applied in the case where a natural number starting from one in order to a peripheral direction of a stator core 32 is applied to each of six or more virtual positions POS that is an equivalent angle interval as a center of a shaft line C in any one of peripheral pars of an inner peripheral part 32i and an outer peripheral part 32o of a cylindrical stator core 32, and a point symmetry as a center of the shaft line C, and (b) the stator core 32 is fastened by a case 90 as a non-rotational member by a volt 80 as a fastening tool into which only the fastening hole 44x provided to one of the first position group POS1 and the second position group POS2 is inserted.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There is known a mounting structure for an electric motor in which fastening holes are provided at equiangular intervals around the axis and at point-symmetrical positions around the axis on the outer periphery of a cylindrical stator core, and the stator core is fastened to a non-rotating member by fasteners (e.g., bolts) inserted through all of the fastening holes. For example, one such structure is described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-89233 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of an electric motor mounting structure in which fastening holes are provided at equal angular intervals and at positions point-symmetrical about the axis, and the stator core is fastened to a non-rotating member by fasteners inserted through all of the fastening holes, the radial stiffness of the stator core has the same characteristics repeated at equal angular intervals and point-symmetrical about the axis. When the radial stiffness of the stator core has such characteristics, resonance due to an integer-order circular vibration mode is likely to occur.

[0005] The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide an electric motor mounting structure and an electric motor mounting method that can suppress the occurrence of resonance due to integer-order circular vibration modes. [Means for solving the problem]

[0006] The gist of the first invention is a mounting structure for an electric motor including a stator core that is cylindrical about an axis and has a plurality of teeth on one of an inner circumference and an outer circumference and a plurality of fastening holes on the other circumference of the inner circumference and the outer circumference, wherein (a) when natural numbers starting from 1 are assigned to six or more virtual positions on the other circumference of the stator core that are equiangularly spaced about the axis and point-symmetric about the axis, in sequence around the stator core, the fastening holes are each provided at one of a first position group to which prime numbers are assigned and a second position group to which numbers other than prime numbers are assigned, and (b) the stator core is fastened to a non-rotating member by fasteners inserted only through the multiple fastening holes provided at one of the first position group and the second position group.

[0007] The gist of the second invention is that in the first invention, the other of the first position group and the second position group is provided with a dummy hole having the same shape as the fastening hole provided in one of the first position group and the second position group.

[0008] The gist of a third invention resides in that in the first or second invention, the non-rotating member is a transmission case.

[0009] The gist of a fourth invention is a mounting method for an electric motor including a stator core having a cylindrical shape centered on an axis, a plurality of teeth provided on one of an inner circumference and an outer circumference, and a plurality of fastening holes provided on the other circumference of the inner circumference and the outer circumference, comprising: (a) a step of positioning the stator core so that it can be fastened to a mounting surface of a non-rotating member; and (b) a step of fastening the stator core to the mounting surface of the non-rotating member by inserting fasteners only through the fastening holes provided at one of a first group of positions given prime numbers and a second group of positions given non-prime numbers, when six or more virtual positions on the other circumference of the stator core that are equiangularly spaced around the axis and point-symmetrical around the axis are each given natural numbers starting from 1 in sequence in the circumferential direction of the stator core.

[0010] The gist of the fifth invention is that in the fourth invention, the other of the first position group and the second position group is provided with a dummy hole having the same shape as the fastening hole provided in one of the first position group and the second position group.

[0011] The gist of a sixth aspect of the present invention is that in the fourth or fifth aspect of the present invention, the non-rotating member is a transmission case. Effect of the Invention

[0012] According to the electric motor mounting structure of the first invention, (a) when natural numbers starting from 1 are assigned to six or more imaginary positions on the other circumferential portion of the stator core that are equiangularly spaced about the axis and point-symmetric about the axis in sequence in the circumferential direction of the stator core, the fastening holes are provided in one of a first position group to which prime numbers are assigned and a second position group to which numbers other than prime numbers are assigned, and (b) the stator core is fastened to a non-rotating member by fasteners inserted only through the fastening holes provided in one of the first position group and the second position group. In this way, the stator core is fastened to a non-rotating member by fasteners inserted only through the fastening holes provided in one of the first position group to which prime numbers are assigned and the second position group to which numbers other than prime numbers are assigned. As a result, since the fastening positions are not repeated at equal angular intervals in the circumferential direction of the stator core, the radial rigidity of the stator core is not point-symmetric about the axis compared to when the fastening positions are repeated at equal angular intervals in the circumferential direction of the stator core, and therefore, the occurrence of resonance due to integer-order circular vibration modes is suppressed.

[0013] According to the electric motor mounting structure of the second invention, in the first invention, the other of the first position group and the second position group is provided with a dummy hole having the same shape as the fastening hole provided in one of the first position group and the second position group. When the dummy hole is provided, the radial stiffness of the stator core before fastening by the fastener has a point-symmetric characteristic about the axis line, compared to when the dummy hole is not provided. Therefore, the reason why the radial stiffness of the stator core after fastening by the fastener is not point-symmetric about the axis line is only due to the symmetry of the fastening positions in the circumferential direction being broken. Therefore, since the causal relationship between the break in the symmetry of the fastening positions and the state in which the radial stiffness of the stator core after fastening by the fastener is not point-symmetric is clear, it is possible to reliably obtain an electric motor mounting structure in which the occurrence of resonance due to an integer-order circular vibration mode is suppressed.

[0014] According to the electric motor mounting structure of the third aspect of the invention, in the first or second aspect of the invention, the non-rotating member is a transmission case. In this way, the occurrence of resonance due to an integer-order circular vibration mode in the electric motor is suppressed, and therefore vibration transmitted from the electric motor to the transmission case is also suppressed. As a result, the suppression of vibration in the transmission case improves the ride comfort of, for example, a vehicle equipped with the transmission case.

[0015] According to a fourth aspect of the present invention, the method for mounting an electric motor includes the steps of: (a) arranging the stator core so that it can be fastened to a mounting surface of a non-rotating member; and (b) fastening the stator core to the mounting surface of the non-rotating member by inserting fasteners only through the fastening holes provided at one of a first position group to which prime numbers are assigned and a second position group to which numbers other than prime numbers are assigned, when natural numbers starting from 1 are assigned to six or more imaginary positions at the other circumferential portion of the stator core at equal angular intervals around the axis and point symmetric around the axis. In this way, in order to obtain a mounting structure for an electric motor that can suppress the occurrence of resonance due to an integer-order circular vibration mode, the stator core is fastened to the mounting surface of the non-rotating member by inserting fasteners only through the fastening holes provided at one of the first position group and the second position group. This reduces the number of fasteners required compared to inserting fasteners through both the first position group and the second position group to fasten the stator core to the mounting surface of the non-rotating member, thereby improving workability when installing the electric motor.

[0016] According to the method for mounting an electric motor of the fifth aspect of the invention, in the fourth aspect of the invention, the other of the first position group and the second position group is provided with dummy holes having the same shape as the fastening holes provided in one of the first position group and the second position group. In this way, the stator core is provided with a plurality of through holes that are either fastening holes or dummy holes at equal angular intervals, and the stator core can be positioned so as to be fastened to a non-rotating member by rotating the stator core at a maximum angle equal to the angle between adjacent through holes among the plurality of through holes provided at equal angular intervals. Therefore, it is easier to position the stator core so as to be fastened to a non-rotating member than when the stator core does not have through holes provided at equal angular intervals, and workability during the installation work of the electric motor is improved.

[0017] According to the sixth aspect of the invention, in the fourth or fifth aspect of the invention, the non-rotating member is a transmission case. In this way, when obtaining an electric motor mounting structure in which the occurrence of resonance due to an integer-order circular vibration mode is suppressed, vibration transmitted to the transmission case is suppressed, and ride comfort in the vehicle is improved, workability during the motor mounting work is improved. [Brief description of the drawings]

[0018] [Figure 1] 1A and 1B are cross-sectional views of a mounting structure for a motor to a case according to a first embodiment of the present invention, where (a) is a radial cross-sectional view and (b) is an axial cross-sectional view. [Diagram 2] 2 is a diagram illustrating a method of mounting the electric motor shown in FIG. 1 to a case. FIG. [Diagram 3] 1A is a diagram showing circular vibration modes of integer orders, where (a) is a second vibration mode, (b) is a third vibration mode, (c) is a fourth vibration mode, and (d) is a fifth vibration mode. [Figure 4] 10A and 10B are cross-sectional views of a mounting structure for a motor to a case according to a second embodiment of the present invention, where (a) is a radial cross-sectional view and (b) is an axial cross-sectional view. [Diagram 5]11A and 11B are cross-sectional views of a mounting structure for a motor to a case according to a third embodiment of the present invention, where (a) is a radial cross-sectional view and (b) is an axial cross-sectional view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. Note that in each of the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of each part are not necessarily drawn accurately. Hereinafter, 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. EXAMPLES

[0020] 1A and 1B are cross-sectional views of a mounting structure for a motor 20 to a case 90 according to a first embodiment of the present invention, in which (a) is a radial cross-sectional view and (b) is a cross-sectional view in the direction of an axis C. Note that Fig. 1B is a cross-sectional view taken along the cutting line 1b-1b shown in Fig. 1A.

[0021] 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, and is a so-called motor generator. The electric motor 20 is, for example, a driving power source for running the vehicle 10.

[0022] For example, the electric motor 20 is an inner rotor type synchronous motor including a cylindrical stator 30 centered on an axis C that is the rotation center line of the rotor 60, and a rotor 60 disposed on the inner circumferential side of the stator 30. The electric motor 20 is an interior permanent magnet motor (IPM motor) having a structure in which a permanent magnet is disposed (embedded) inside the rotor 60, for example.

[0023] The stator 30 includes a stator core 32 and a winding (not shown) wound around the stator core 32. The stator core 32 is formed by, for example, stacking a plurality of electromagnetic steel sheets 50 in the direction of the axis C. An insulating coating is formed on the front and back surfaces of the electromagnetic steel sheets 50.

[0024] The stator core 32 is cylindrical with the axis C at its center. A plurality of (48 in this embodiment) grooves, i.e., slots 38, which have a depth in a direction toward the outer periphery of the stator core 32 in the radial direction and penetrate in the direction of the axis C, are provided in the inner periphery 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 become electromagnets and generate a rotating magnetic field. Thus, the stator core 32 has a plurality of teeth 36 in its inner periphery 32i. The inner periphery 32i corresponds to "one of the peripheries" in the present invention.

[0025] The yoke 34 is a portion of the stator core 32 other than the teeth 36, and serves as a path for magnetic lines of force between the teeth 36 which are electromagnets.

[0026] The outer periphery 32o of the stator core 32 is provided with a plurality of through holes 44 penetrating in the direction of the axis C. The plurality of through holes 44 are provided at all of eight imaginary positions POS that are equiangularly spaced (2π / 8 [rad] in this embodiment) around the axis C on the outer periphery 32o in the radial cross-sectional view of FIG. 1(a) and point-symmetrical around the axis C. When natural numbers starting from 1 are assigned to these eight imaginary positions POS in the circumferential counterclockwise direction, for example, when "1" to "8" are assigned, the imaginary positions POS are positions P1 to P8 in FIG. 1(a). The radial distances from the axis C to each of the positions P1 to P8 are the same. These positions P1 to P8 are equiangularly spaced around the axis C. The through holes 44 are cylindrical through holes 44a, 44b, 44c, 44d, 44e, 44f, 44g, and 44h having the same diameter and centered on center lines 46a, 46b, 46c, 46d, 46e, 46f, 46g, and 46h, respectively. The center lines 46a, 46b, 46c, 46d, 46e, 46f, 46g, and 46h are parallel to the axis C and pass through positions P1 to P8, respectively. In this manner, the through holes 44 have the same shape. The through holes 44 are provided in the protruding portion 40. The protruding portion 40 protrudes partially radially outward at the outer circumferential portion 32o of the stator core 32 and extends in the direction of the axis C. The through holes 44 are each open at one end surface 32a and the other end surface 32b of the stator core 32 in the direction of the axis C.

[0027] Here, in the virtual positions POS, the four positions P2, P3, P5, and P7 assigned with prime numbers (in this embodiment, 2, 3, 5, and 7) are defined as a first position group POS1, and the four positions P1, P4, P6, and P8 assigned with numbers other than prime numbers (in this embodiment, 1, 4, 6, and 8) are defined as a second position group POS2.

[0028] The rotor 60 is rotatably disposed on the inner periphery side of the stator 30. The inner periphery surface of the stator 30 and the outer periphery surface of the rotor 60 face each other in the radial direction. A rotor shaft 62 is inserted into the inner periphery of the rotor 60 and is connected to the rotor shaft 62 so as to be rotatable about an axis C. The rotor shaft 62 is supported by the case 90 via a bearing (not shown).

[0029] The case 90 is a non-rotating member. The case 90 is, for example, a bottomed cylindrical case, 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 holes 94 at positions corresponding to the multiple through holes 44. The multiple holes 94 are holes 94a, 94b, 94c, 94d, 94e, 94f, 94g, and 94h that are provided at positions corresponding to the through holes 44. A female screw is formed on the inner circumferential surface of each of the holes 94. The case 90 corresponds to the "non-rotating member" in the present invention.

[0030] Here, the term "fastening hole" refers to one of the multiple through holes 44 through which the bolt 80 is inserted to fasten the stator core 32 to the case 90 as described later, and the term "dummy hole" refers to one of the multiple through holes 44 through which the bolt 80 is not inserted to fasten the stator core 32 to the case 90 as described later. Also, the term "locking hole" refers to one of the multiple holes 94 that is provided corresponding to the position of the fastening hole, and the term "non-locking hole" refers to one of the multiple holes 94 that is provided corresponding to the position of the dummy hole. In this embodiment, the through holes 44b, 44c, 44e, and 44g are the fastening holes 44x, and the through holes 44a, 44d, 44f, and 44h are the dummy holes 44y. Also, the holes 94b, 94c, 94e, and 94g are the locking holes 94x, and the holes 94a, 94d, 94f, and 94h are the non-locking holes 94y. The fastening holes 44x and the dummy holes 44y correspond to the "fastening holes" and the "dummy holes" of the present invention, respectively.

[0031] FIG. 2 is a diagram for explaining a method of mounting the electric motor 20 shown in FIG.

[0032] First, in step S10, a process is performed in which stator core 32 is disposed so as to be fastenable to mounting surface 92 of case 90. Specifically, stator core 32 is disposed so that openings of the multiple through holes 44 on the other end surface 32b side face opposite openings of multiple holes 94 provided in mounting surface 92, respectively.

[0033] After execution of step S10, in step S20, a process is executed in which the bolts 80 are inserted only into the fastening holes 44x (=through holes 44b, 44c, 44e, 44g) provided in the first position group POS1, and the stator core 32 is fastened to the mounting surface 92 of the case 90 at four locations. The bolts 80 have, for example, a shaft portion 80a and a head portion 80b that has a larger diameter than the shaft portion 80a and is provided on one end side of the shaft portion 80a. A male screw is formed on the outer circumferential surface of the tip portion on the other end side of the shaft portion 80a. The diameter of each of the fastening holes 44x is larger than the diameter of the shaft portion 80a and smaller than the diameter of the head portion 80b. In the first position group POS1, the male screw provided at the tip portion of the shaft portion 80a of the bolt 80 inserted into each of the fastening holes 44x is screwed into the female screw provided in the locking hole 94x, thereby fastening the stator core 32 to the case 90. In the second position group POS2, the bolts 80 are not inserted into the dummy holes 44y, i.e., the male threads of the bolts 80 are not screwed into the non-engagement holes 94y of the case 90. "Screwed" means to connect the male threads by twisting and rotating them relative to the female threads. In this embodiment, the first position group POS1 is a fastening position for fastening the stator core 32 to the case 90, while the second position group POS2 is a non-fastening position that is not a fastening position for fastening the stator core 32 to the case 90. The bolts 80 correspond to the "fastener" in this invention.

[0034] From here, the circular vibration mode will be explained.

[0035] As described above, when the electric motor 20 is driven by an alternating current, each tooth portion 36 becomes an electromagnet and generates a rotating magnetic field. The rotor 60 is then attracted 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 has an integer-order circular vibration mode.

[0036] 3 is a diagram showing circular vibration modes of integer orders, where (a) is the second vibration mode (=when the integer order is "2"), (b) is the third vibration mode (=when the integer order is "3"), (c) is the fourth vibration mode (=when the integer order is "4"), and (d) is the fifth vibration mode (=when the integer order is "5"). In FIG. 3, a schematic showing the state of a radial cross section of the stator core 32 at one point in time and a schematic showing the state of a radial cross section of the stator core 32 at another point in time are respectively shown by solid lines and dashed lines. In addition, at the virtual position POS, the fastened position is shown by a black circle, and the non-fastened position is shown by a white circle.

[0037] In the resonance due to the circular vibration mode, the anti-rotation portions where the stator core 32 expands or contracts in the radial direction and the nodes where the stator core 32 hardly expands or contracts in the radial direction appear periodically in the circumferential direction. The anti-rotation portions are portions where the stator core 32 has a large radial vibration, and the nodes are portions where the stator core 32 has a smaller radial vibration than the anti-rotation portions. The number of anti-rotation portions and the nodes is twice the integer order in the circular vibration mode. In addition, in any of the integer order circular vibration modes, the anti-rotation portions and the nodes are located at positions that are point-symmetric about the axis C. In addition, in the case where the integer order is an even number, such as the second vibration mode and the fourth vibration mode, when the state of the radial cross section of the stator core 32 is rotated 180[deg] about the axis C, the portions of the anti-rotation portions where the stator core 32 expands in the radial direction and the portions where the stator core 32 contracts in the radial direction coincide with each other. When the integer order is odd, such as the third vibration mode and the fifth vibration mode, when the radial cross-section of the stator core 32 is rotated 180 degrees 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.

[0038] Incidentally, in the stator core 32, the radial rigidity is relatively high at the fastened position, and the radial rigidity is relatively low at the non-fastened position. For example, when all of the imaginary positions POS that are equiangularly spaced about the axis C and point-symmetric about the axis C are set as fastened positions (i.e., when the bolts 80 are inserted into all of the through holes 44, respectively, and the stator core 32 is fastened to the case 90), the radial rigidity of the stator core 32 has the same characteristics repeated at equiangular intervals and has point-symmetric characteristics about the axis C. When the radial rigidity of the stator core 32 has such point-symmetric characteristics, resonance due to an integer-order circular vibration mode in which the webbones and nodes are positioned point-symmetric about the axis C is likely to occur.

[0039] In this embodiment, only the first position group POS1 of the virtual positions POS is set as the fastening position. As a result, the fastening positions are not repeated at equal angular intervals in the circumferential direction, so the radial stiffness of the stator core 32 is not point-symmetrical about the axis C compared to the case where the fastening positions are repeated at equal angular intervals in the circumferential direction. Specifically, in any of the circular vibration modes, the radial stiffness of the stator core 32 is relatively high at positions P2 and P5, while the radial stiffness of the stator core 32 is relatively low at positions P6 and P1, which are point-symmetrical about the axis C with respect to positions P2 and P5. This is because the symmetry of the fastening positions in the circumferential direction is destroyed by only the first position group POS1 to which a prime number is assigned being set as the fastening position. As a result of the radial stiffness of the stator core 32 not being point-symmetrical about the axis C, resonance due to an integer-order circular vibration mode in which the webbones and nodes are point-symmetrical about the axis C is less likely to occur.

[0040] According to the mounting structure of the electric motor 20 of this embodiment, (a) when natural numbers starting from 1 are assigned to eight virtual positions POS on the outer circumferential portion 32o of the stator core 32 at equal angular intervals of 2π / 8 [rad] around the axis C and point-symmetric around the axis C in sequence counterclockwise around the stator core 32, fastening holes 44x (=through holes 44b, 44c, 44e, 44g) are provided in a first position group POS1 to which a prime number is assigned, and (b) the stator core 32 is fastened to the case 90 by bolts 80 inserted only through the fastening holes 44x provided in the first position group POS1. In this manner, the stator core 32 is fastened to the case 90 by bolts 80 inserted only through the fastening holes 44x provided in the first position group POS1 to which a prime number is assigned. As a result, the fastening positions are not repeated at equal angular intervals in the circumferential direction of the stator core 32, and therefore, compared to a case in which the fastening positions are repeated at equal angular intervals in the circumferential direction of the stator core 32, the state is not point-symmetrical about the axis C. Therefore, the occurrence of resonance due to an integer-order circular vibration mode is suppressed.

[0041] According to the mounting structure of the electric motor 20 of this embodiment, the second position group POS2 is provided with dummy holes 44y (= through holes 44a, 44d, 44f, 44h) having the same shape as the fastening holes 44x provided in the first position group POS1. When the dummy holes 44y are provided, the radial rigidity of the stator core 32 before fastening with the bolts 80 has point-symmetric characteristics about the axis C, compared to when the dummy holes 44y are not provided. Therefore, the reason why the radial rigidity of the stator core 32 after fastening with the bolts 80 is not point-symmetric about the axis C is only due to the symmetry of the fastening positions in the circumferential direction being broken. Therefore, since the causal relationship between the break in the symmetry of the fastening positions and the state in which the radial rigidity of the stator core 32 after fastening with the bolts 80 is not point-symmetric, it is possible to reliably obtain a mounting structure of the electric motor 20 in which the occurrence of resonance due to an integer-order circular vibration mode is suppressed.

[0042] According to the mounting structure of the electric motor 20 of this embodiment, the case 90 is a transmission case. In this manner, the occurrence of resonance due to an integer-order circular vibration mode in the electric motor 20 is suppressed, and therefore the vibration transmitted from the electric motor 20 to the transmission case is also suppressed. As a result, the vibration in the transmission case is suppressed, and thus, for example, the ride comfort of the vehicle 10 equipped with the transmission case is improved.

[0043] The mounting method of the electric motor 20 of this embodiment includes the steps of (a) arranging the stator core 32 so as to be fastened to the mounting surface 92 of the case 90, and (b) fastening the stator core 32 to the mounting surface 92 of the case 90 by inserting the bolts 80 only through the fastening holes 44x provided in the first position group POS1 to which a prime number is assigned, when natural numbers starting from 1 are assigned to eight imaginary positions POS on the outer circumferential portion 32o of the stator core 32 at equal angular intervals of 2π / 8 [rad] around the axis C and point-symmetric about the axis C in sequence in the circumferential direction of the stator core 32 counterclockwise. In this way, in order to obtain a mounting structure of the electric motor 20 capable of suppressing the occurrence of resonance due to an integer-order circular vibration mode, the stator core 32 is fastened to the mounting surface 92 of the case 90 by inserting the bolts 80 only through the multiple fastening holes 44x provided in the first position group POS1. This reduces the number of bolts 80 compared to inserting bolts 80 through both the first position group POS1 and the second position group POS2 to fasten the stator core 32 to the mounting surface 92 of the case 90, thereby improving workability when installing the electric motor 20.

[0044] According to the mounting method of the electric motor 20 of this embodiment, the second position group POS2 is provided with dummy holes 44y having the same shape as the fastening holes 44x provided in the first position group POS1. In this manner, the stator core 32 is provided with a plurality of through holes 44 that are either the fastening holes 44x or the dummy holes 44y at equal angular intervals, and the stator core 32 can be positioned so as to be fastened to the case 90 by rotating the stator core 32 at an angle equal to the maximum angle between adjacent through holes among the plurality of through holes 44 provided at equal angular intervals. Therefore, compared to a case in which the stator core 32 does not have the through holes 44 at equal angular intervals, it is easier to position the stator core 32 so as to be fastened to the case 90, and the workability during the mounting work of the electric motor 20 is improved.

[0045] According to the mounting method of the electric motor 20 of this embodiment, the case 90 is a transmission case. In this manner, when obtaining a mounting structure for the electric motor 20 in which the occurrence of resonance due to an integer-order circular vibration mode is suppressed, thereby suppressing vibration transmitted to the transmission case and improving the ride comfort of the vehicle 10, the workability during the mounting work of the electric motor 20 is improved. EXAMPLES

[0046] 4A and 4B are cross-sectional views of a mounting structure for mounting an electric motor 120 to a case 90 according to a second embodiment of the present invention, 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. 4B is a cross-sectional view taken along the cutting line 4b-4b shown in Fig. 4A.

[0047] The configuration of the electric motor 120 according to this embodiment is the same as the configuration of the electric motor 20 according to the above-described embodiment 1. The mounting structure of the electric motor 120 according to this embodiment is different in fastening position from the mounting structure of the electric motor 20 according to embodiment 1. Therefore, the following description will focus on the parts of this embodiment that are different from embodiment 1, and parts that are substantially common in function to embodiment 1 will be denoted by the same reference numerals and descriptions thereof will be omitted as appropriate.

[0048] In this embodiment, the through holes 44a, 44d, 44f, and 44h are fastening holes 144x, and the through holes 44b, 44c, 44e, and 44g are dummy holes 144y. The holes 94a, 94d, 94f, and 94h are locking holes 194x, and the holes 94b, 94c, 94e, and 94g are non-locking holes 194y. The fastening holes 144x and the dummy holes 144y correspond to the "fastening holes" and "dummy holes" of the present invention, respectively.

[0049] The mounting method of the electric motor 120 in this embodiment is substantially the same as the mounting method of the electric motor 20 in the above-described embodiment 1, except that the bolts 80 are inserted only through the fastening holes 144x (=through holes 44a, 44d, 44f, 44h) instead of through the fastening holes 44x, and the stator core 32 is fastened to the mounting surface 92 of the case 90 at four points.

[0050] In the second position group POS2, the male threads provided at the tip of the shaft portion 80a of the bolt 80 inserted through each of the fastening holes 144x are screwed into the female threads provided in the locking holes 194x, thereby fastening the stator core 32 to the case 90. In the first position group POS1, the bolt 80 is not inserted through each of the dummy holes 144y, that is, the male threads provided on the bolt 80 are not screwed into the non-locking holes 194y of the case 90. In this embodiment, the second position group POS2 is a fastening position for fastening the stator core 32 to the case 90, while the first position group POS1 is a non-fastening position.

[0051] In the above-described first embodiment, only the first position group POS1 of the virtual positions POS is set as the fastened position, so that the radial stiffness of the stator core 32 is not point-symmetrical about the axis C. On the other hand, in this embodiment, only the second position group POS2 of the virtual positions POS is set as the fastened position, so that the radial stiffness of the stator core 32 is not point-symmetrical about the axis C. As can be seen by switching the fastened positions and the non-fastened positions in FIG. 3, the symmetry of the fastened positions in the circumferential direction is also lost in this embodiment. In this way, the radial stiffness of the stator core 32 is not point-symmetrical about the axis C, so that resonance due to an integer-order circular vibration mode in which the webbones and nodes are point-symmetrical about the axis C is less likely to occur.

[0052] The mounting structure of the electric motor 120 of this embodiment is different from that of the first embodiment in that the stator core 32 is fastened to the case 90 by bolts 80 inserted only through fastening holes 144x provided in a second position group POS2 to which a non-prime number is assigned among the virtual positions POS, but is otherwise the same. In this embodiment as well, the radial rigidity of the stator core 32 is not point-symmetrical about the axis C, and therefore the same effects as those of the first embodiment are achieved.

[0053] The mounting method of the electric motor 120 of the present embodiment is different from the above-described first embodiment in that the bolts 80 are inserted only into the fastening holes 144x provided in the second position group POS2 to which a number other than a prime number is assigned among the virtual positions POS, thereby fastening the stator core 32 to the mounting surface 92 of the case 90. The rest of the mounting method is the same as that of the above-described first embodiment. Therefore, the same effects as those of the above-described first embodiment are achieved. EXAMPLES

[0054] 5A and 5B are cross-sectional views of a mounting structure for mounting a motor 220 to a case 90 according to a third embodiment of the present invention, 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. 5B is a cross-sectional view taken along the cutting line 5b-5b shown in Fig. 5A.

[0055] The configuration of the electric motor 220 according to the third embodiment of the present invention is substantially the same as that of the electric motor 20 according to the first embodiment. In the first embodiment, the through holes 44 are provided at all the virtual positions POS, but in the present embodiment, the through holes 44 (=through holes 44b, 44c, 44e, 44g) are provided only at the first position group POS1 among the virtual positions POS, and the holes 94b, 94c, 94e, 94g are provided only at the positions corresponding to the first position group POS1. Therefore, the present embodiment will be described mainly with respect to the parts different from the first embodiment, and the parts substantially common in function to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0056] The electric motor 220 is an inner rotor type synchronous motor including a cylindrical stator 230 and a rotor 60 disposed on the inner circumferential side of the stator 230. The stator 230 includes a stator core 232 and a winding (not shown) wound around the stator core 232.

[0057] The stator core 232 has substantially the same configuration as the stator core 32 according to the first embodiment. In the stator core 232, the first position group POS1 of the virtual positions POS has the through holes 44b, 44c, 44e, and 44g. On the other hand, the second position group POS2 of the virtual positions POS has no protrusion 40 and no through holes 44a, 44d, 44f, and 44h. The holes 94a, 94d, 94f, and 94h are not provided at positions on the mounting surface 92 of the case 90 corresponding to the second position group POS2.

[0058] In this embodiment, the through holes 44b, 44c, 44e, and 44g are fastening holes 244x, and the holes 94b, 94c, 94e, and 94g are locking holes 294x. In this embodiment, no dummy holes or non-locking holes are provided. The fastening holes 244x correspond to the "fastening holes" of the present invention.

[0059] The mounting method of the electric motor 220 in this embodiment is the same as the mounting method of the electric motor 20 in the above-described first embodiment, except that neither the dummy holes nor the non-locking holes are provided.

[0060] In this embodiment, the first position group POS1 is a fastening position for fastening the stator core 232 to the case 90, while the second position group POS2 is a non-fastening position.

[0061] The mounting structure of the electric motor 220 of this embodiment is the same as that of the first embodiment except that no dummy holes (=through holes 44a, 44d, 44f, 44h) are provided in the second position group POS2. Also in this embodiment, the radial rigidity of the stator core 32 is not point-symmetrical about the axis C, so that the same effects as those of the first embodiment are achieved except for the effects due to the provision of the dummy holes.

[0062] The mounting method of the electric motor 220 of this embodiment is the same as that of the above-mentioned embodiment 1, except that neither the dummy hole nor the non-locking hole is provided. Therefore, the same effects as those of the above-mentioned embodiment 1 are achieved, except for the effects due to the provision of the dummy hole.

[0063] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can be applied to other embodiments as well.

[0064] In the above-mentioned embodiments 1, 2, and 3, natural numbers starting from 1 are assigned to the virtual positions POS in a counterclockwise circumferential direction, but the present invention may be such that natural numbers starting from 1 are assigned to the virtual positions POS in a clockwise circumferential direction.

[0065] In the above-mentioned embodiment 3, the locking holes 294x (=holes 94b, 94c, 94e, 94g) are provided only at positions corresponding to the first position group POS1, but the present invention is not limited to this embodiment. For example, in the embodiment 3, non-locking holes (=holes 94a, 94d, 94f, 94h) may be provided at positions corresponding to the second position group POS2, as in the embodiment 1. That is, regardless of whether it is the first position group POS1 or the second position group POS2, holes 94 may be provided at positions corresponding to them.

[0066] In the above-mentioned Example 3, the second position group POS2 does not have any of the through holes 44a, 44d, 44f, 44h or the protrusion 40 on which they are provided, but it may also be an embodiment in which, for example, the second position group POS2 does not have the through holes 44a, 44d, 44f, 44h but has the protrusion 40.

[0067] In the above-described first, second, and third embodiments, the stator core 32 is fastened to the case 90 at four locations by the bolts 80, but the stator core 32 may be fastened to the case 90 at three locations by the bolts 80. For example, in the first embodiment, when natural numbers starting from 1 are sequentially assigned to six imaginary positions POS on the outer circumferential portion 32o at equal angular intervals of 2π / 6 [rad] around the axis C and point-symmetric about the axis C in counterclockwise or clockwise directions around the stator core 32, the stator core 32 may be fastened to the case 90 by the bolts 80 inserted only through a plurality of through holes 44 provided in a position group assigned with prime numbers (2, 3, 5). For example, in the first embodiment, when natural numbers starting from 1 are assigned to ten virtual positions POS on the outer circumferential portion 32o at equal angular intervals of 2π / 10 [rad] around the axis C and point-symmetric around the axis C in sequence in the counterclockwise or clockwise direction of the stator core 32, the stator core 32 may be fastened to the case 90 by bolts 80 inserted only through the through holes 44 provided in the position groups to which prime numbers (2, 3, 5, 7) are assigned. In this manner, if the number of virtual positions POS is six or more, the first position group POS1 and the second position group POS2 each have three or more. Therefore, regardless of whether the first position group POS1 or the second position group POS2 of the virtual positions POS is set as the fastening position, the stator core 32, 232 is always fastened to the case 90 at three or more points. As a result, the other end surface 32b of the stator core 32, 232 and the mounting surface 92 of the case 90 are stably fastened to each other.

[0068] In the above-described first, second, and third embodiments, the electric motors 20, 120, and 220 are of the inner rotor type, but may be of the outer rotor type. When the electric motors 20, 120, and 220 are of the outer rotor type, the teeth 36 are provided on the outer circumferential portions 32o and 232o of the stator cores 32 and 232, and the fastening holes 44x, 144x, and 244x are provided on the inner circumferential portions 32i and 232i of the stator cores 32 and 232. In this case, the outer circumferential portions 32o and 232o and the inner circumferential portions 32i and 232i respectively correspond to the "one circumferential portion" and the "other circumferential portion" in the present invention.

[0069] In the above-described first, second and third embodiments, the bolt 80 corresponds to the "fastener" of the present invention, but the present invention is not limited to this embodiment, and for example, the "fastener" may be a combination of a bolt and a nut.

[0070] It should be noted that the above-described embodiments are merely examples of the present invention, and the present invention can be embodied 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]

[0071] 20,120,220: Electric motor 32,232: Stator core 32i, 232i: Inner circumference (one side) 32o, 232o: Outer periphery (other periphery) 36: Teeth 44x;144x;244x: Fastening hole 44y;144y: dummy hole 80: Bolt (fastener) 90: Case (non-rotating part) 92: Mounting surface C: Axis line POS: Virtual Location POS1: First position group POS2: Second position group

Claims

1. A mounting structure for an electric motor including a stator core having a cylindrical shape centered on an axis, a plurality of teeth provided on one of an inner peripheral portion and an outer peripheral portion, and a plurality of fastening holes provided on the other peripheral portion of the inner peripheral portion and the outer peripheral portion, when natural numbers starting from 1 are assigned to six or more imaginary positions at equiangular intervals about the axis and point-symmetric about the axis in the other peripheral portion of the stator core in sequence in the circumferential direction of the stator core, the fastening holes are provided in one of a first group of positions assigned with prime numbers and a second group of positions assigned with numbers other than prime numbers, The stator core is fastened to a non-rotating member by fasteners inserted through only a plurality of fastening holes provided in one of the first position group and the second position group. A mounting structure for an electric motor.

2. The other of the first position group and the second position group is provided with a dummy hole having the same shape as the fastening hole provided in one of the first position group and the second position group.

2. The electric motor mounting structure according to claim 1.

3. The non-rotating member is a transmission case.

3. The electric motor mounting structure according to claim 1 or 2.

4. A method for mounting an electric motor including a stator core having a cylindrical shape centered on an axis, a plurality of teeth provided on one of an inner peripheral portion and an outer peripheral portion, and a plurality of fastening holes provided on the other peripheral portion of the inner peripheral portion and the outer peripheral portion, comprising the steps of: disposing the stator core so as to be fastened to a mounting surface of a non-rotating member; and fastening the stator core to the mounting surface of the non-rotating member by inserting fasteners through only the fastening holes provided at either one of a first group of positions to which prime numbers are assigned and a second group of positions to which numbers other than prime numbers are assigned, when natural numbers starting from 1 are assigned in sequence in a circumferential direction of the stator core to six or more virtual positions on the other peripheral portion of the stator core that are equiangularly spaced about the axis and point-symmetric about the axis. A method for mounting an electric motor.

5. The other of the first position group and the second position group is provided with a dummy hole having the same shape as the fastening hole provided in one of the first position group and the second position group.

5. The method for mounting an electric motor according to claim 4.

6. The non-rotating member is a transmission case.

6. A method for mounting an electric motor according to claim 4 or 5.

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