JP7091764B2 - Permanent magnet motor - Google Patents

Description

The present invention relates to a permanent magnet motor including a rotor having an insulating member.

As a conventional permanent magnet motor, an inner rotor type permanent magnet motor in which a rotor having a permanent magnet is rotatably arranged inside a stator that generates a rotating magnetic field is known. This permanent magnet motor is used, for example, to rotationally drive a blower fan mounted on an air conditioner.

When this permanent magnet motor is driven by a PWM type inverter that performs high frequency switching, a potential difference (shaft voltage) is generated between the inner ring and the outer ring of the bearing. When this shaft voltage reaches the breakdown voltage of the oil film inside the bearing, a current flows inside the bearing and causes electrolytic corrosion in the bearing. In order to prevent electrolytic corrosion of this bearing, for example, one provided with a rotor having an insulating member is known (see, for example, Patent Document 1). The rotor includes, for example, an annular permanent magnet, an annular outer peripheral side iron core located on the inner diameter side of the permanent magnet, an annular inner peripheral side iron core located on the inner diameter side of the outer peripheral side iron core, and an outer peripheral side iron core and inner core. It includes an insulating member located between the peripheral cores and a shaft fixed to a through hole penetrating in the direction of the central axis of the inner core.

The insulating member of such a rotor is formed of, for example, a resin filled between the outer peripheral side iron core and the inner peripheral side iron core.

Japanese Unexamined Patent Publication No. 2012-39875

By the way, in the above-mentioned electrolytic corrosion of the bearing, when the permanent magnet motor is driven by the PWM type inverter, the neutral point potential of the winding of the stator does not become zero, and a voltage called a common mode voltage is generated. Since this common mode voltage contains a high frequency component due to switching, an axial voltage is generated between the outer ring and the inner ring of the bearing due to the stray capacitance inside the permanent magnet motor.

The common mode voltage is divided as a potential on the inner ring side (shaft side) of the bearing by the capacitance between the winding of the stator and the shaft and the capacitance between the shaft and the circuit board for driving the inverter. .. Then, the common mode voltage is divided as a potential on the outer ring side (bracket side) of the bearing by the capacitance between the winding of the stator and the bracket and the capacitance between the bracket and the circuit board for driving the inverter. To. The potential difference between the inner ring side and the outer ring side of this bearing is the shaft voltage.

The upper limit of the thickness of the insulating member of the rotor is structurally restricted, and even if PBT resin is used as the material, the shaft voltage is suppressed when the impedance on the rotor side (bearing inner ring side) is low and the shaft voltage is high. Therefore, in the prior art described in Patent Document 1, an air layer or a hole is formed in a part of the insulating member. Since the relative permittivity of air is almost 1, it is smaller than the PBT of about 3. Therefore, it is possible to reduce the capacitance of the rotor by providing an air layer and holes, and to increase the impedance on the rotor side (bearing inner ring side).

However, when a through hole is formed as a hole in order to form an air layer in the insulating member as in the rotor described in Patent Document 1, the strength of the insulating member is lowered, so that the inside of the through hole is formed. A wall portion is provided in the first axial direction hole that opens the through hole on one end side in the axial direction of the insulating member and a second axial direction hole that opens on the other end side in the axial direction of the insulating member. It is considered to secure the strength of the insulating member. By providing this wall portion, the bottom portion of the first axial direction hole is formed on one end side of the wall portion, and the bottom portion of the second axial direction hole is formed on the other end side of the wall portion.
On the other hand, thermal stress is generated in the insulating member due to the usage environment of the permanent magnet motor and the heat generated from the stator winding during driving. In particular, thermal stress is concentrated on the portion where the axial side wall and the bottom of the first axial hole intersect and the portion where the axial side wall and the bottom of the second axial hole intersect. When thermal stress is concentrated, there is a concern that the durability of the insulating member may decrease and cracks or cracks may occur. In order to alleviate this thermal stress concentration, R chamfers and C chamfers are formed at the intersection of the axial side wall and the bottom of the first axial hole and the intersection of the axial side wall and the bottom of the second axial hole. Is being done.

As shown in FIGS. 3 and 4, for example, the end face shape of the first axial hole and the second axial hole is formed in an arc shape along the circumferential direction, and the depth is increased in the direction along the axial direction from the end face. Have.
However, in order to reduce the capacitance for a rotor having a small radius and a thick axial direction, it is necessary to increase the depth of the first axial hole and the second axial hole. Then, when the mechanical strength of the insulating member and the draft of the mold at the time of forming the first axial hole and the second axial hole are taken into consideration, as shown in FIGS. 3 and 4, the first axial hole is formed. And the length R in the radial direction of the second axial hole cannot be sufficiently taken.

As a result, as shown in FIG. 8A, in order to alleviate the thermal stress concentration in the portion where the axial side wall and the bottom of the first axial hole intersect and the portion where the axial side wall and the bottom of the second axial hole intersect. In addition, a tilted portion having an tilt angle θ1 of, for example, 45 degrees with respect to the axial direction is formed by C chamfering. Since the second axial hole is formed symmetrically with respect to the wall portion, the illustration is omitted. The insulating member forming the first axial hole and the second axial hole has a structure having a region A forming a wall portion, a region B forming an inclined portion, and a region C forming an axial side wall portion. The first axial hole and the second axial hole have a region B between the boundary portion between the inclined portion and the axial side wall (P3, P4) and the boundary portion between the inclined portion and the bottom portion (P1, P2), respectively. It becomes narrow and the axial length L1 of the region B cannot be sufficiently taken. In this case, the thermal expansion in the region A cannot be absorbed in the region B, and the directions of the thermal expansion shown in the region B and the region C are significantly different. Therefore, the boundary portion between the region B and the region C (P3, Thermal stress is concentrated on P4).

On the other hand, as shown in FIG. 8B, in order to alleviate the thermal stress concentration at the portion where the axial side wall and the bottom of the first axial hole intersect and the portion where the axial side wall and the bottom of the second axial hole intersect. In addition, a tilted portion having an tilt angle θ2 of, for example, 22.5 degrees is formed in the axial direction by C chamfering. The first axial hole and the second axial hole have a region B between the boundary portion between the inclined portion and the axial side wall (P3, P4) and the boundary portion between the inclined portion and the bottom portion (P1, P2), respectively. It is wider than that of FIG. 8A, and the axial length L1 of the region B can be sufficiently taken. In this case, the thermal stress concentration at the boundary between the region B and the region C (P3, P4) can be relaxed, but the direction of thermal expansion indicated by the arrow is significantly different between the region A and the region B. Thermal stress is concentrated on the boundary portion (P1, P2) between the region B and the region A.
In this way, as shown in FIGS. 8 (a) and 8 (b), the portion where the axial side wall and the bottom of the first axial hole intersect with each other by forming an inclined portion in the axial direction by C chamfering, and Even if the thermal stress concentration at the intersection of the axial side wall and the bottom of the second axial hole is relaxed, the boundary portion (P3, P4) between the inclined portion and the axial side wall of the first axial hole and the second Thermal stress is concentrated on the boundary portion (P3, P4) between the inclined portion of the biaxial hole and the axial side wall, the boundary portion (P1, P2) between the inclined portion and the bottom of the first axial hole, and the first. Thermal stress is concentrated on the boundary portion (P1, P2) between the inclined portion and the bottom portion of the biaxial hole.

Therefore, the present invention has been made by paying attention to the problem of the prior art described in Patent Document 1, and is a wall that divides the inside of the through hole of the insulating member into a first axial hole and a second axial hole. When a portion is provided and the bottom portion of the first axial hole is formed on one end side of the wall portion and the bottom portion of the second axial hole is formed on the other end side of the wall portion, the first axial hole and the second portion are formed. The boundary between the axial side wall and the bottom of at least one of the axial holes, the boundary between the inclined portion and the axial side wall of the first axial hole and the second axial hole, and the first axial hole and the second axial direction. It is an object of the present invention to provide a permanent magnet motor capable of relaxing the concentration of thermal stress on the boundary portion between the inclined portion and the bottom portion of the hole.

In order to solve the above problems, one aspect of the permanent magnet motor of the present invention includes a stator fixed to the outer shell of the motor and a rotor arranged inside the stator, and the rotor is arranged with a permanent magnet. A motor that supports an annular outer peripheral side core, an annular inner peripheral core located on the inner diameter side of the outer peripheral core, an insulating member located between the outer peripheral core and the inner peripheral core, and an inner peripheral core. The outer shell is provided with a shaft rotatably supported by bearings, and the insulating member includes a first axial hole that opens at one end surface in the axial direction, a second axial hole that opens at the other end surface in the axial direction, and a first. A wall portion formed between the axial hole and the second axial hole is provided, and each of the first axial hole and the second axial hole has a side wall on the inner diameter side, a side wall on the outer diameter side, and a bottom. The inner side wall, the outer diameter side side wall, and the bottom portion are formed by molding with a mold, and at least one of the first axial direction hole and the second axial direction hole is a boundary between the inner diameter side side wall and the bottom portion. It is a permanent magnet motor in which two or more stages of stress relaxation inclined portions for relieving thermal stress are formed around the portion and around the boundary portion between the side wall and the bottom on the outer diameter side .

According to one aspect of the permanent magnet electric motor of the present invention, in order to prevent electrolytic corrosion of the bearing, the insulating member is provided with a wall portion that separates the first axial hole and the second axial hole extending in the axial direction, and the wall portion is provided. When the bottom of the first axial hole is formed on one end side of the wall and the bottom of the second axial hole is formed on the other end side of the wall, the axial direction of the first axial hole and the second axial hole. The boundary between the side wall and the bottom, the boundary between the inclined portion of the first axial hole and the second axial hole and the axial side wall, and the boundary between the inclined portion and the bottom of the first axial hole and the second axial hole. The concentration of thermal stress on the part can be relaxed.

It is explanatory drawing which shows the permanent magnet electric motor which concerns on this invention. It is a perspective view which shows the 1st Embodiment of the rotor of the permanent magnet electric motor which concerns on this invention. It is a top view of the rotor of FIG. It is a bottom view of the rotor of FIG. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is a partial cross-sectional view of the part C of FIG. It is a top view of the rotor which shows the state which the permanent magnet is attached to the iron core on the outer peripheral side. It is a figure explaining the relaxation of the thermal stress concentration around the bottom of the 1st axial hole of the present invention, and the relaxation of the thermal stress concentration around the bottom of the 1st axial hole of this invention, (a) and (b) are conventional It is explanatory drawing, and (c) is explanatory drawing of this invention.

Next, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic and differ from the actual ones. Therefore, specific components should be judged in consideration of the following explanations.

Further, the embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention describes the shape, structure, arrangement, etc. of components. It is not specific to the following. The technical idea of the present invention may be modified in various ways within the technical scope specified by the claims described in the claims.

Hereinafter, the permanent magnet motor according to the embodiment of the present invention will be described.

<Overall configuration of motor>
1 to 6 are diagrams illustrating the configuration of the permanent magnet motor 1 according to the first embodiment. As shown in FIGS. 1 to 6, the permanent magnet motor 1 is, for example, a brushless DC motor. The permanent magnet motor 1 is used to rotationally drive a blower fan mounted on an indoor unit of an air conditioner.

Hereinafter, an inner rotor type permanent magnet motor 1 in which a rotor 3 having a permanent magnet 31 is rotatably arranged inside a stator 2 that generates a rotating magnetic field will be described as an example. The permanent magnet motor 1 in the present embodiment includes a stator 2, a rotor 3, and a motor outer shell 6.

<Stator and rotor>
The stator 2 includes a stator core 21 having a cylindrical yoke portion and a plurality of teeth portions extending from the yoke portion to the inner diameter side, and a winding 23 wound around the teeth portion via an insulator 22. .. The stator 2 is covered with a motor outer shell 6 made of resin, except for the inner peripheral surface of the stator core 21.

The rotor 3 is rotatably arranged with a predetermined gap on the inner peripheral side of the stator core 21 of the stator 2. This rotor is a surface magnet type in which a permanent magnet 31 is arranged in an annular shape on an outer peripheral surface facing the stator core 21. The permanent magnet 31 is fixed around the shaft 35 via the outer peripheral side iron core 32, the insulating member 33, and the inner peripheral side iron core 34, which will be described later. The shaft 35 is supported by the first bearing 41 and the second bearing 42, and the first bearing 41 is supported by the first bracket 51 and the second bearing 42 is supported by the second bracket 52, so that the rotor 3 is supported. It is rotatably supported.

<Bearings and brackets>
The first bearing 41 supports one end side (output side) of the shaft 35 of the rotor 3. The second bearing 42 supports the other end side (counter-output side) of the shaft 35 of the rotor 3. As the first bearing 41 and the second bearing 42, for example, ball bearings are used.

The first bracket 51 is made of metal (steel plate, aluminum, etc.) and is fixed to one end side of the motor outer shell 6, that is, the output side of the shaft 35. The first bracket 51 has a cylindrical bracket body 511 having one end open and the other end closed by a bottom plate portion 510, and a first bearing accommodating the first bearing 41 provided in the bottom plate portion 510 to accommodate the first bearing 41. It has a portion 512. The open end side of the bracket body 511 is press-fitted into the outer peripheral surface of the motor outer shell 6. The first bearing accommodating portion 512 is formed in a cylindrical shape having a bottom portion protruding from the central portion of the bottom plate portion 510 to the side opposite to the motor outer shell 6. The outer ring of the first bearing 41 is press-fitted into the inner surface of the cylinder of the first bearing accommodating portion 512, and the output side of the shaft 35 supported by the inner ring of the first bearing 41 projects outward from a through hole formed in the center of the bottom. Has been done.

The second bracket 52 is made of metal (steel plate, aluminum, etc.) and is arranged on the other end side of the motor outer shell 6, that is, on the counter-output side of the shaft 35. The second bracket 52 has a second bearing accommodating portion 521 for accommodating the second bearing 42, and a flange portion 522 extending around from the open end of the second bearing accommodating portion 521. The second bearing accommodating portion 521 is formed in a cylindrical shape having a bottom portion, and the flange portion 522 of the second bracket 52 is insert-molded at the time of molding the motor outer shell 6 and is integrated with the motor outer shell 6.

The first bearing 41 is housed in a first bearing accommodating portion 512 provided in the first bracket 51, and the second bearing 42 is accommodated in a second bearing accommodating portion 521 provided in the second bracket 52. The first bearing 41 and the first bearing accommodating portion 512, and the second bearing 42 and the second bearing accommodating portion 521 are electrically conductive, respectively.

<Specific configuration of rotor>
In the permanent magnet motor 1 configured as described above, in order to prevent electrolytic corrosion in the first bearing 41 and the second bearing 42, as shown in FIG. 1, a part of the rotor 3 is an insulating member 33. It is equipped with. Hereinafter, a specific configuration of the rotor 3 will be described.

As shown in FIGS. 1 to 6, the rotor 3 has a permanent magnet 31, an outer peripheral side iron core 32, an insulating member 33, an inner peripheral side iron core 34, and a shaft 35 from the outer diameter side to the inner diameter side. It is equipped with.

As shown in FIGS. 1 and 7, the permanent magnet 31 is formed in an annular shape by a plurality of (for example, eight) permanent magnet pieces 311 so that the north and south poles appear alternately at equal intervals in the circumferential direction. .. As the permanent magnet 31, a plastic magnet formed in an annular shape by solidifying the magnet powder with a resin may be used.

As shown in FIG. 3, the outer peripheral side iron core 32 is formed in an annular shape and is located on the inner diameter side of the permanent magnet 31. Although not shown, the outer peripheral side iron core 32 has a plurality (for example, four) protruding from the inner peripheral surface 321 (see FIG. 5) toward the inner diameter side in order to secure the function of preventing rotation with the insulating member 33 described later. ), It is provided with an outer peripheral side convex portion and an outer peripheral side concave portion recessed from the inner peripheral surface 321 to the outer diameter side. The plurality of outer peripheral side convex portions and outer peripheral side concave portions extend in the direction of the central axis O and are arranged at equal intervals in the circumferential direction.

As shown in FIG. 3, the inner peripheral side iron core 34 is formed in an annular shape and is located on the inner diameter side of the outer peripheral side iron core 32. Although not shown, the inner peripheral side iron core 34 has a plurality (for example, eight) recessed from the outer peripheral surface 341 (see FIG. 5) toward the inner diameter side in order to secure the function of preventing rotation with the insulating member 33 described later. It has a recess on the inner peripheral side of the. The plurality of inner peripheral recesses extend in the direction of the central axis O and are arranged at equal intervals in the circumferential direction. The inner peripheral side iron core 34 is provided with a through hole 343 that penetrates in the direction of the central axis O at the center.

The insulating member 33 is made of a dielectric resin such as PBT or PET, and is located between the outer peripheral side iron core 32 and the inner peripheral side iron core 34. The insulating member 33 is integrally formed with the outer peripheral side iron core 32 and the inner peripheral side iron core 34 by filling the resin between the outer peripheral side iron core 32 and the inner peripheral side iron core 34. The insulating member 33 has a first bearing in which the capacitance between the outer peripheral side iron core 32 and the inner peripheral side iron core 34 (a part of the capacitance between the winding 23 of the stator 2 and the shaft 35) is reduced. The potentials on the inner ring side of the 41 and the second bearing 42 are lowered to match the potentials on the inner ring side and the outer ring side.

The shaft 35 is fixed to a through hole 343 provided in the inner peripheral side iron core 34 by press fitting or caulking.

<Structure, action and effect of rotor according to the present invention>
Next, in the permanent magnet motor 1 of the present embodiment, the structure of the rotor 3 according to the present invention, its action and effect will be described with reference to FIGS. 2 to 5.

Since the permanent magnet motor 1 used to drive the blower fan mounted on the air conditioner to rotate is driven by a PWM type inverter, the neutral point potential of the winding does not become zero, which is called a common mode voltage. Voltage is generated. Due to this common mode voltage, a potential difference (shaft voltage) is generated between the outer ring and the inner ring of the first bearing 41 and the second bearing 42 due to the floating capacity inside the permanent magnet motor 1. When this shaft voltage reaches the breakdown voltage of the oil film inside the bearing, a current flows inside the bearing and causes electrolytic corrosion inside the bearing.

In the configuration of the rotor 3 described above, the insulating member 33 has a cylindrical shape as shown in FIGS. 2 to 4, and is first at one end in the axial direction in order to reduce the electrostatic capacity of the rotor 3. An axial hole 331 is formed, and a second axial hole 332 for reducing the electrostatic capacity of the rotor 3 is similarly formed at the other end in the axial direction. A plurality (for example, eight) of these first axial holes 331 and the second axial holes 332 are formed at equal intervals in the circumferential direction. A partition wall 334 is formed between each of the plurality of first axial holes 331 and between each of the plurality of second axial holes 332, and adjacent first axial holes 331 are adjacent to each other and adjacent to each other. The second axial hole 332 is separated from each other.

Further, the first axial hole 331 and the second axial hole 332 face each other in the axial direction as shown in FIGS. 3 to 5, so that the depths of the first axial hole 331 and the second axial hole 332 are the same at the central position in the axial direction. A wall portion 333 is provided. By providing the wall portion 333, the bottom portion 335c of the first axial direction hole 331 is formed on one end side of the wall portion 333, and the bottom portion 335c of the second axial direction hole 332 is formed on the other end side of the wall portion 333. Has been done. A side wall 335a and a side wall 335b are formed along the axial direction from the bottom portions 335c of the first axial hole 331 and the second axial hole 332, respectively. In this way, the first axial hole 331 and the second axial hole 332 are formed in an arc shape along the circumferential direction by forming the wall portion 333 and the partition wall 334, and the direction along the axial direction from the end face. It has a structure having a certain depth, and each of them is formed at equal intervals (for example, 8 pieces).

Here, for example, when the first axial hole 331 and the second axial hole 332 are formed with respect to the rotor 3 having a small radius and a thick axial direction, the radius of the rotor 3 becomes small, so that the first axis The length (width) R of the direction hole 331 and the second axial hole 332 in the radial direction is also reduced. In order to reduce the capacitance of the rotor 3, it is necessary to increase the depth of the first axial hole 331 and the second axial hole 332. However, if the depth of the first axial hole 331 and the second axial hole 332 is made too deep, the thickness of the wall portion 333 that separates the first axial hole 331 and the second axial hole 332 becomes thin, and insulation is provided. Since the mechanical strength of the member 33 is lowered, a wall portion 333 having an appropriate thickness is required to secure the mechanical strength.

Therefore, the depths of the first axial hole 331 and the second axial hole 332 are set in consideration of both the reduction of the capacitance of the rotor 3 and the securing of the mechanical strength.

Since the insulating member 33 is integrally molded with a dielectric resin such as PBT or PET together with the outer peripheral side iron core 32 and the inner peripheral side iron core 34, the mechanical strength of the rotor 3 and the first axial direction hole 331 are combined with the insulating member 33. When the draft of the mold at the time of molding the second axial hole 332 is taken into consideration, as described above, as shown in FIGS. 2 to 5, the first axial hole 331 and the second axial direction The hole 332 is formed in an arc shape along the circumferential direction by forming the wall portion 333 and the partition wall 334, and has a structure having a depth in the direction along the axial direction from the end face in the first axial direction. The length (width) R in the radial direction of the hole 331 and the second axial hole 332 cannot be sufficiently taken.

By the way, in general, the coefficient of linear expansion of the insulating member 33 is larger than the coefficient of linear expansion of the surrounding metal outer peripheral side iron core 32 and the inner peripheral side iron core 34, and the expansion amount at the time of temperature rise and the linear expansion coefficient at the time of temperature decrease The amount of shrinkage is larger than that of the outer peripheral side iron core 32 and the inner peripheral side iron core 34.

As shown in FIG. 6, in the insulating member 33, the amount of expansion and contraction of the side walls 335a and 335b in the insulating member 33 is smaller in the radial direction and thicker in the axial direction than the radial side. It is larger in the axial direction.

Further, the amount of expansion and contraction of the wall portion 333 of the insulating member 33 is divided into a radial component and an axial component, but the radial direction is regulated by the outer peripheral side iron core 32 and the inner peripheral side iron core 34. Axial expansion and contraction is greater than radial expansion and contraction.

Therefore, when considering the expansion of the wall portion 333 due to the temperature rise, the expansion in the axial direction becomes larger than the expansion in the radial direction, and due to the influence of the expansion of the wall portion 333, the first axial hole 331 Thermal stress is concentrated on the portion where the bottom portion 335c and the side walls 335a and 335b intersect, and the portion where the bottom portion 335c and the side walls 335a and 335b of the second axial hole 332 intersect.

Here, the degree of concentration of thermal stress is examined for the first axial hole 331. Normally, as shown by the dotted line in FIG. 8A, the bottom portion 335c is substantially perpendicular to the side walls 335a and 335b of the insulating member 33 forming the first axial hole 331 facing each other, and the first The insulating member 33 forming the axial hole 331 has a region A forming the wall portion 333 and a region C forming the side walls 335a and 335b. Since the directions are significantly different, thermal stress is concentrated at the boundary portion P0a between the side wall 335a and the bottom portion 335c and the boundary portion P0b between the side wall 335b and the bottom portion 335c.

Therefore, in order to alleviate the concentration of thermal stress on the boundary portions P0a and P0b, as shown in FIG. 8A, a cut is made between the side walls 335a and 335b and the bottom 335c at an angle of, for example, 45 degrees. It is conceivable to chamfer to form the inclined portions 335d and 335e. In this case, the insulating member 33 forming the first axial hole 331 has a region A forming the wall portion 333, a region B forming the inclined portions 335d and 335e, and a region C forming the side walls 335a and 335b. By forming the inclined portion 335d, the thermal stress is relaxed at the boundary portion P0a between the bottom portion 335c and the side wall 335a, and by forming the inclined portion 335e, the thermal stress is relaxed at the boundary portion P0b between the bottom portion 335c and the side wall 335b. It is possible to suppress the concentration of thermal stress.

By the way, the insulating member 33 forming the first axial hole 331 has the axial thickness of the region A forming the wall portion 333, the radial thickness of the region C forming the side walls 335a and 335b, and the radius of the rotor 3. Depending on the length and the shape of the chamfer, the axial length L1 of the region B forming the inclined portions 335d and 335e is absorbed by the axial thermal expansion of the region A forming the wall portion 333 to reduce the thermal stress. It may not be possible to have an axial length LS that can be relaxed. For example, assuming that the axial thickness of the region A is sufficiently larger than the radial thickness of the region C and the radial length of the rotor 3 is also sufficiently large, the radial length R of the first axial hole 331 is assumed to be sufficiently large. Is sufficiently large, so that the axial length L1 of the region B forming the inclined portions 335d and 335e can be formed long by the C chamfer cutting at an angle of 45 degrees, so that the axial length L1 is thermally stressed. Can be set to an axial length LS that can be relaxed.
However, as shown in FIG. 8A, when the radial length R of the first axial hole 331 is small, the boundary portion P3 between the side wall 335a and the inclined portion 335d, which corresponds to the axial length of the region B. The axial length L1 between the side wall 335a and the boundary portion P0a of the bottom portion 335c, the boundary portion P4 between the side wall 335b and the inclined portion 335e, and the boundary portion P0b between the side wall 335b and the bottom portion 335c is heat. It is shorter than the axial length Ls that can relieve stress. Therefore, the thermal stress is concentrated on the boundary portion P3 between the side wall 335a and the inclined portion 335d and the boundary portion P4 between the side wall 335b and the inclined portion 335e.

In order to alleviate the concentration of thermal stress at the boundary portion P3 between the side wall 335a and the inclined portion 335d and the boundary portion P4 between the side wall 335b and the inclined portion 335d, the boundary portions P3 and P4 are shown in FIG. It is necessary to set the axial length L1 between the bottom 335c and the bottom 335c to the axial length Ls that can relieve the thermal stress. In this way, in order to set the axial length L1 to the axial length Ls that can relieve the thermal stress, for example, the inclined portion is chamfered by 22.5 degrees according to the dimensions shown in FIG. 8 (b). When 335d and 335e are formed, the inclination angle θ2 with respect to the side wall 335a of the inclined portion 335d and the inclination angle θ2 with respect to the side wall 335b of the inclined portion 335e are gentler than the inclination angle θ1 shown in FIG. It is possible to relax the concentration of thermal stress at the boundary portion P3 of the portion 335d and the boundary portion P4 between the side wall 335b and the inclined portion 335e. However, in the boundary portion P1 between the inclined portion 335d and the bottom portion 335c and the boundary portion P2 between the inclined portion 335e and the bottom portion 335c, the direction of thermal expansion is the axial direction at the bottom portion 335c as shown by an arrow in FIG. 8B. On the other hand, in the inclined portions 335d and 335e, the direction of thermal expansion is perpendicular to the inclined surface corresponding to the C plane, and the directions differ greatly by nearly 90 degrees with respect to the axial direction. Thermal stress is concentrated on P2.

In this way, when chamfering is performed at one place between the side walls 335a and 335b and the bottom portion 335c to form the inclined portions 335d and 335e having an inclined surface corresponding to the C surface, the boundary portion P3 on the side wall 335a side and the boundary portion P3 and The thermal stress is concentrated on the boundary portion P4 on the side wall 335b side, or the thermal stress is concentrated on the boundary portions P1 and P2 on the bottom portion 335c side. Even when R chamfering is performed instead of C chamfering in FIG. 8A, the boundary portion between the curved portion of the R chamfer and the side walls 335a and 335b is the boundary portion P3 and the inclined portion of the inclined portion 335d and the side wall 335a of the C chamfer. It is at the same position as the boundary portion P4 between the 335e and the side wall 335b, and the axial length L1 between the boundary portions P3 and P4 and the bottom 335c is shorter than the axial length Ls capable of relieving thermal stress, and the thermal stress is relieved. Cannot be done sufficiently.

Therefore, in the present embodiment, as shown in FIG. 8C, from the ends of the side walls 335a and 335b corresponding to the axial length Ls capable of relieving the thermal stress from the bottom 335c, with respect to the axial direction. For example, the first stress relaxation inclined portions 336a and 336b having the first inclination angle θ3 are formed by chamfering about 6.4 degrees according to the dimensions shown in FIG. 8 (c), and stress relaxation is performed on the bottom portion 335c side. The second stress relaxation inclined portions 336c and 336d having the second inclined angle θ4 are formed by chamfering at 45 degrees according to the dimensions shown in FIG. 8 (c), for example, as shown in FIG. 8 (a). .. The angle between the second stress relaxation slope 336c and the side wall 335a and between the second stress relaxation slope 336d and the side wall 335b due to the formation of the second stress relaxation slopes 336c and 336d chamfered by 45 degrees. θ4 is formed at 45 degrees, respectively, and the angle θ5 between the second stress relaxation inclined portions 336c and 336d and the bottom portion 335c is formed at 45 degrees. As a result, between the side walls 335a and 335b of the first axial hole 331 and the bottom portion 335c, the first stress relaxation inclined portion 336a and the second stress relaxation inclined portion 336c, the first stress relaxation inclined portion 336b and the second stress relaxation are performed. By combining the inclined portions 336d, two stages of stress relaxation inclined portions 336 are formed. Therefore, around the boundary portion P0a between the side wall 335a and the bottom portion 335c of the first axial direction hole 331 formed in the insulating member 33, and around the boundary portion P0b between the side wall 335b and the bottom portion 335c of the first axial direction hole 331. The region A forming the wall portion 333, the region B-1 forming the second stress relaxation inclined portions 336c and 336d, the region B-2 forming the first stress relaxation inclined portions 336a and 336b, and the side walls 335a and 335b are formed. It has a region C to be formed. Not only when the two-stage stress relaxation inclined portion 336 is formed between the side walls 335a and 335b facing each other in the radial direction and the bottom portion 335c, but also between the side walls 334 at both ends in the circumferential direction and the bottom portion 335c. A two-stage stress relaxation slope may be formed.

Further, as described above, the second inclination angle θ4 with respect to the axial direction of the second stress relaxation inclined portions 336c and 336d is set to be larger than the first inclination angle θ3 with respect to the axial direction of the first stress relaxation inclined portions 336a and 336b. There is. Then, as shown in FIG. 8C, the first inclination angle θ3 and the second inclination angle θ4 are set to angles at which the concentration of thermal stress can be relaxed according to the amount of expansion in the axial direction due to the thermal expansion of the wall portion 333. It is set.

By forming the two-stage stress relaxation inclined portion 336 in this way, between the boundary portion P13 and the bottom portion 335c of the side wall 335a and the first stress relaxation inclined portion 336a, and between the side wall 335b and the first stress relaxation inclined portion 336b. The axial length L1 between the boundary portion P14 and the bottom portion 335c can be the axial length Ls capable of relieving thermal stress, and the region B forming the first stress relief inclined portions 336a and 336b. Since the change in the direction of thermal expansion between -2 and the region C forming the side walls 335a and 335b is small, the concentration of thermal stress due to the axial thermal expansion of the wall portion 333 at the boundary portions P13 and P14 is relaxed. can do.

Further, in the boundary portion P11 between the bottom portion 335c and the second stress relaxation inclined portion 336c and the boundary portion P12 between the bottom portion 335c and the second stress relaxation inclined portion 336d, the region A forming the wall portion 333 and the second stress relaxation inclination are also formed. The change in the direction of thermal expansion between the regions B-1 forming the portions 336c and 336d is smaller than that in FIG. 8 (b), and the boundary portions P11 and P12 are suppressed in order to suppress a large change in the direction of thermal expansion. It is possible to alleviate the concentration of thermal stress due to the axial thermal expansion of the wall portion 333 in the wall portion 333.

Further, at the boundary portion between the first stress relaxation inclined portion 336a and the second stress relaxation inclined portion 336c and the boundary portion between the first stress relaxation inclined portion 336b and the second stress relaxation inclined portion 336d, the second stress relaxation inclined portion 336c is also formed. And the first stress relaxation in order to suppress a large change in the direction of thermal expansion between the region B-1 forming the 336d and the region B-2 forming the first stress relaxation inclined portions 336a and 336b. Thermal stress due to axial thermal expansion of the wall portion 333 at the boundary portion P15 between the inclined portion 336a and the second stress relaxation inclined portion 336c and the boundary portion P16 between the first stress relaxation inclined portion 336b and the second stress relaxation inclined portion 336d. Concentration can be eased.

As a result of actual thermal stress analysis by the applicant, FIGS. 8 (a) and 8 (b) have a structure in which the radial length R of the first axial hole 331 can be obtained only, for example, 3 mm. ), It has become possible to reduce the thermal stress to about two-thirds as compared with the case where the inclined portions 335d and 335e are formed by one-step chamfering.

Therefore, by forming the two-stage stress relaxation inclined portion 336 between the side walls 335a and 335b and the bottom portion 335c, the periphery of the bottom portion 335c of the first axial hole 331 due to the axial thermal expansion of the wall portion 333 (around the bottom portion). ), The concentration of thermal stress can be eliminated, the deterioration of durability due to the repeated concentration of thermal stress of the insulating member 33 can be suppressed, the occurrence of cracks and cracks can be suppressed, and the life can be extended. can. Here, the periphery of the bottom portion 335c of the first axial direction hole 331 (periphery of the bottom portion) is the periphery of the boundary portion P0a between the side wall 335a of the first axial direction hole 331 and the bottom portion 335c, and the side wall 335b of the first axial direction hole 331. And the periphery of the boundary portion P0b of the bottom 335c. In the following explanation, it will be abbreviated as around the bottom.

Further, similarly to the first axial hole 331, the second axial hole 332 also has the first stress relaxation inclined portions 336a and 336b and the second stress relaxation inclined portion around the bottom of the second axial direction hole 332. 336c and 336d are formed, and by forming the two-stage stress relaxation inclined portion 336, the same action and effect as described above can be obtained.

According to the present embodiment described above, when the diameter of the rotor 3 is small and the electrostatic capacity of the rotor 3 is reduced, the periphery of the bottom of the first axial hole 331 and the second axial hole 332. Even when one-step chamfering of sufficient size cannot be performed, the concentration of thermal stress is relaxed to reduce the thermal stress around the bottoms of the first axial hole 331 and the second axial hole 332 of the insulating member 33. By reducing the number, the insulating member 33 can be made less likely to be cracked or cracked, and the durability can be improved.

In the above description, the case where the wall portion 333 thermally expands due to the heat generated by the winding 23 of the stator 2 in the usage environment and the driving state of the permanent magnet motor 1 has been described, but it depends on the usage environment and the driving state of the permanent magnet motor 1. The concentration of thermal stress around the bottoms of the first axial hole 331 and the second axial hole 332 can be relaxed even during thermal shrinkage when the temperature drops.

Therefore, in order to prevent electrolytic corrosion of the first bearing 41 and the second bearing 42 that support the shaft 35, the insulating member 33 is arranged in the rotor 3, and the insulating member 33 has the first axial hole 331 and the second axial direction. When the hole 332 is formed, it is possible to alleviate the concentration of thermal stress generated in the insulating member 33, which is a problem when the rotor 3 having a small diameter is manufactured. As a result, the capacitance of the rotor 3 can be reduced, a small rotor 3 having durability can be manufactured, and the permanent magnet motor 1 itself can be miniaturized.

In the above embodiment, the case where the first stress relaxation inclined portions 336a and 336b and the second stress relaxation inclined portions 336c and 336d are chamfered by a plane has been described, but the present invention is not limited thereto. , Chamfering with a curved surface can be applied instead of chamfering with a flat surface.

Further, in the above embodiment, the case where the two-stage thermal stress relaxation inclined portion 336 is formed around the bottom of the first axial hole 331 and the second axial hole 332 has been described, but the present invention is not limited thereto. It is also possible to form three or more stages of thermal stress gradients.

Further, in the above embodiment, the end face shapes of the first axial hole 331 and the second axial hole 332 are not limited to the case where they are formed in an arc shape along the circumferential direction, and both ends in the circumferential direction are semicircular. Can be. Further, the number of the first axial hole 331 and the second axial hole 332 is not limited to eight, and can be any number as long as the mechanical strength of the insulating member 33 can be secured. Further, the number of the first axial hole 331 and the second axial hole 332 is not limited to a plurality, and the first axial hole 331 and the second axial hole 332 are regarded as one hole in the circumferential direction. It may be formed into a continuous shape.

Further, in the above embodiment, since the first axial hole 331 and the second axial hole 332 are formed symmetrically with respect to the wall portion 333, the first axial hole 331 and the second axial hole 332 are formed. A stress relaxation inclined portion 336 is formed around each bottom, but the present invention is not limited to this, and the first axial hole 331 and the second axial hole 332 have an asymmetrical shape with respect to the wall 333. When formed, a stress relaxation inclined portion may be formed around the bottom of either the first axial hole 331 or the second axial hole 332, whichever has a stronger degree of concentration of thermal stress.

Further, in the above embodiment, the case where the present invention is applied to the surface magnet type rotor 3 in which the permanent magnet 31 is arranged on the outer peripheral surface of the outer peripheral side iron core 32 has been described, but the present invention is not limited to this, and the outer periphery is not limited thereto. The present invention can also be applied to an embedded magnet type rotor in which a slot extending in the axial direction is formed at a chord position with respect to the outer peripheral surface of the side iron core 32 and a permanent magnet is arranged in this slot.

1 ... Permanent magnet motor 2 ... Steader 21 ... Steader iron core 22 ... Insulator 23 ... Winding 3 ... Rotor 31 ... Permanent magnet 311 ... Permanent magnet piece 32 ... Outer peripheral side iron core 321 ... Inner peripheral surface 33 ... Insulating member 33a ... One end surface 33b ... End surface 331 ... First axial hole 332 ... Second axial hole 333 ... Wall part 334 ... Partition 335a, 335b ... Side wall 335c ... Bottom 335d, 335e ... Inclined part 336 ... Stress relaxation inclined part 336a, 336b ... 1st stress relaxation inclined portion 336c, 336d ... 2nd stress relaxation inclined portion 34 ... Inner peripheral side iron core 341 ... Outer peripheral surface 343 ... Through hole 35 ... Shaft 41 ... 1st bearing 42 ... 2nd bearing 51 ... 1st bracket 511 ... Bracket body 512 ... 1st bearing accommodating part 52 ... 2nd bracket 521 ... 2nd bearing accommodating part 522 ... Flange part O ... Central axis

Claims (4)

It has a stator fixed to the outer shell of the motor and a rotor placed inside the stator.
The rotor is located between the annular outer peripheral side iron core in which the permanent magnet is arranged, the annular inner peripheral side iron core located on the inner diameter side of the outer peripheral side iron core, and the outer peripheral side iron core and the inner peripheral side iron core. An insulating member and a shaft that supports the inner peripheral side iron core and is rotatably supported by bearings on the outer shell of the motor are provided.
The insulating member is between a first axial hole that opens on one end surface in the axial direction, a second axial hole that opens on the other end surface in the axial direction, and a first axial hole and a second axial hole. A wall part to be formed is provided in
Each of the first axial hole and the second axial hole has a side wall on the inner diameter side, a side wall on the outer diameter side, and a bottom portion, and the side wall on the inner diameter side, the side wall on the outer diameter side, and the bottom portion. Is formed by molding with a mold,
At least one of the first axial hole and the second axial hole is the periphery of the boundary portion between the inner diameter side side wall and the bottom portion , and the boundary portion between the outer diameter side side wall and the bottom portion. A permanent magnet motor characterized by forming two or more stages of stress relaxation slopes around it to relieve thermal stress. Around the boundary between the side wall and the bottom of at least one of the first axial hole and the second axial hole, thermal stress is relaxed by absorbing the axial thermal expansion of the wall portion. First stress that is inclined by the first tilt angle with respect to the axial direction from the end of at least one side wall of the first axial hole and the second axial hole corresponding to the axial length from the bottom. The permanent according to claim 1, wherein a relaxation inclined portion is formed, and a second stress relaxation inclined portion inclined by a second inclination angle is formed between the first stress relaxation inclined portion and the bottom portion. Magnet electric motor. The permanent according to claim 2, wherein the second inclination angle of the second stress relaxation inclination portion with respect to the axial direction is set to be larger than the first inclination angle of the first stress relaxation inclination portion with respect to the axial direction. Magnet motor. A plurality of the first axial hole and the second axial hole are provided in the circumferential direction, and between each of the plurality of first axial holes and between each of the plurality of second axial holes. The partition wall is formed in the above, and the end face shapes of the first axial hole and the second axial hole are formed in an arc shape along the circumferential direction, according to any one of claims 1 to 3. The described permanent magnet motor.

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