JP7119509B2 - permanent magnet motor - Google Patents

Description

The present invention relates to a permanent magnet motor with a rotor having insulating members.

2. Description of the Related Art Among conventional permanent magnet motors, there is known an inner rotor type permanent magnet motor in which a rotor having permanent magnets is rotatably arranged inside a stator that generates a rotating magnetic field. This permanent magnet motor is used, for example, for rotating 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 dielectric breakdown voltage of the oil film inside the bearing, a current flows inside the bearing, causing electrolytic corrosion in the bearing. In order to prevent the electrolytic corrosion of the bearing, for example, a bearing having a rotor having an insulating member is known (see, for example, Patent Document 1).

This rotor includes, for example, an annular permanent magnet, an annular outer core located on the inner diameter side of the permanent magnet, an annular inner core located on the inner diameter side of the outer core, an outer core and an inner core. It has an insulating member positioned between the peripheral cores, and a shaft fixed to a through hole penetrating the inner peripheral core in the direction of the central axis.

Such an insulating member of the rotor is made of, for example, a resin filled between the outer core and the inner core.

JP 2012-39875 A

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

The common mode voltage is divided as potential on the inner ring side (shaft side) of the bearing by the electrostatic capacitance distribution between the stator windings and the shaft and the electrostatic capacitance between the shaft and the inverter drive circuit board. be. The common mode voltage is divided as the potential on the outer ring side (bracket side) of the bearing by the capacitance between the stator windings and the bracket and the capacitance between the bracket and the inverter drive circuit board. be. The potential difference between the inner ring side and the outer ring side of this bearing becomes the shaft voltage.

Shaft voltage is suppressed when the upper limit of the thickness of the rotor insulation member is structurally regulated, and the impedance on the rotor side (bearing inner ring side) is low even if PBT resin is used as the material, and the shaft voltage is high. Therefore, in the prior art described in Patent Document 1, an air layer or holes are formed in a part of the insulating member. The dielectric constant of air is approximately 1, which is small compared to PBT, which is about 3. Therefore, by providing an air layer or air holes, the electrostatic capacity of the rotor can be reduced, and the impedance on the rotor side (bearing inner ring side) is increased.

However, as in the rotor described in Patent Document 1, when through holes are formed as holes to form an air layer in the insulating member, the strength of the insulating member is reduced, so the inside of the through holes a wall portion that divides the through-hole into a first axial hole opening at one axial end side of the insulating member and a second axial hole opening at the other axial end side of the insulating member; It is considered to ensure the strength of the insulating member by By providing this wall portion, 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 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 operating environment of the permanent magnet motor and the heat generated from the stator windings during driving. In particular, the thermal stress concentrates 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 the thermal stress concentrates, there is a concern that the insulating member may be deteriorated in durability or cracked. In order to alleviate this thermal stress concentration, the portion where the axial side wall and bottom of the first axial hole intersect and the portion where the axial side wall and bottom of the second axial hole intersect are rounded or chamfered. is being done.

As shown in FIGS. 3 and 4, the first axial hole and the second axial hole are, for example, arcuate in the end face shape along the circumferential direction, and the depth extends from the end face in the axial direction. have.
However, if the capacitance is to be reduced for a rotor that is small in radius and thick in the axial direction, it is necessary to increase the depth of the first axial hole and the second axial hole. Considering the mechanical strength of the insulating member and the draft angle of the mold when forming the first axial hole and the second axial hole, as shown in FIGS. and the radial length R of the second axial hole cannot be sufficiently taken.

As a result, as shown in FIG. 9, the portion where the side wall SW1 of the first axial hole HL1 and the bottom portion BS intersect, the portion where the side wall SW2 of the first axial hole HL1 and the bottom portion BS intersect, or similarly the second axial direction In order to relieve the concentration of thermal stress at the intersections of the both side walls and the bottom of the hole, the inclined portions IS1 and IS2 are formed at an inclination angle θ1 of, for example, 45 degrees with respect to the axial direction by C-chamfering. The second axial hole is formed symmetrically with the first axial hole HL1 with respect to the wall W0, so illustration thereof is omitted. The insulating member IR forming the first axial hole HL1 and the second axial hole has a region A forming the wall portion W0, a region B forming the inclined portions IS1 and IS2, and a region C forming the side walls SW1 and SW2. It has a structure with The first axial hole HL1 and the second axial hole are formed at boundary portions P3 and P4 between the inclined portions IS1 and IS2 and the side walls SW1 and SW2 and boundary portions P1 and P2 between the inclined portions IS1 and IS2 and the bottom portion BS, respectively. The area B between them becomes narrow, and the axial length L1 of the area B cannot be sufficiently secured. In this case, the thermal expansion in the region A cannot be absorbed by the region B, and the directions of thermal expansion shown in the regions B and C are greatly different. Thermal stress is concentrated in

In general, the metal inner core Ci, outer core Co, and insulating member IR expand when the temperature rises. The direction of expansion is divided into expansion in the axial direction and expansion from the inner peripheral side to the outer peripheral side. Further, the coefficient of linear expansion of the insulating member IR is relative to the coefficient of linear expansion of the inner peripheral core Ci fixed to the shaft SH on the inner peripheral side of the insulating member IR and the outer peripheral core Co of the outer peripheral side of the insulating member IR. big. As a result, in the outer peripheral side wall SW2 and the C-chamfered inclined portion IS2, the outer peripheral core Co is present at the outermost peripheral position, so thermal expansion from the inner peripheral side to the outer peripheral side is prevented by the outer peripheral core Co. .

Therefore, the directions of thermal expansion indicated by the regions A and B are not perpendicular to the bottom surfaces and inclined surfaces of the bottom portion BS and the inclined portion IS2, but are inclined toward the outer periphery. As a result, the change in the direction of thermal expansion indicated by the regions B and C is greater than the change in the direction indicated by the inclined portion IS1 and the side wall SW1 on the inner peripheral side. The change is bigger. Therefore, the thermal stress concentrates more at the boundary portion P4 between the C-chamfered inclined portion IS2 on the outer peripheral side and the side wall SW2 than on the boundary portion P3 between the C-chamfered inclined portion IS1 on the inner peripheral side and the side wall SW1.

Therefore, the present invention has been made by paying attention to the problem of the prior art described in the above-mentioned Patent Document 1, and includes a wall that divides the interior of the through hole of the insulating member into a first axial hole and a second axial hole. is provided, the bottom of the first axial hole is formed on one end of the wall, and the bottom of the second axial hole is formed on the other end of the wall, the first axial hole and the second To provide a permanent magnet motor capable of alleviating the concentration of thermal stress on the boundary between the side wall and the bottom of an axial hole and on the outer peripheral side of the boundary between the inclined portion and the side wall of a first axial hole and a second axial hole. purpose.

In order to solve the above problems, one aspect of the permanent magnet electric motor of the present invention comprises a stator fixed to the motor shell and a rotor arranged inside the stator, and the rotor is arranged with permanent magnets. An annular outer core, an annular inner core positioned on the inner diameter side of the outer core, an insulating member positioned between the outer core and the inner core, and a motor supporting the inner core. The insulating member has a shaft rotatably supported by a bearing on the outer shell, and the insulating member includes a first axial hole opening at one end face in the axial direction, a second axial hole opening at the other end face in the axial direction, a first A wall formed between the axial hole and the second axial hole, the bottom of the first axial hole being formed on one end of the wall, and the second axial hole being formed on the other end of the wall and each of the first axial hole and the second axial hole has an inner side wall formed along the axial direction, an outer side wall formed along the axial direction, and a first stress relieving inclined portion for relieving thermal stress is formed around a boundary portion between an inner peripheral side wall and a bottom portion of at least one of the first axial hole and the second axial hole. , the first stress relaxation inclined portion is inclined with respect to the inner peripheral side wall, and the second stress relaxation inclined portion for relaxing thermal stress is formed around the boundary portion between the outer peripheral side wall and the bottom , The second stress relaxation inclined portion is inclined with respect to the side wall on the outer peripheral side, and the second stress relaxation inclined portion is longer in the axial direction than the first stress relaxation inclined portion.

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

It is an explanatory view showing a permanent magnet motor according to the present invention. 1 is a perspective view showing a first embodiment of a rotor of a permanent magnet motor according to the present invention; FIG. 3 is a plan view of the rotor of FIG. 2; FIG. 3 is a bottom view of the rotor of FIG. 2; FIG. FIG. 4 is a cross-sectional view of FIG. 3, where (a) is a cross-sectional view taken along line AA, and (b) is a partial cross-sectional view of part C of (a). FIG. 3 is a plan view of a rotor showing a state in which permanent magnets are attached to an outer core; FIG. 10A is a conventional explanatory diagram illustrating thermal stress concentration around the bottom of a conventional first axial hole and mitigation of thermal stress concentration around the bottom of the first axial hole according to the present invention; , (b) are explanatory diagrams of the present invention. FIG. 6 is an enlarged cross-sectional view showing a second embodiment of the rotor of the permanent magnet motor according to the present invention; It is a figure explaining the thermal-stress concentration around the bottom part of the conventional 1st axial direction hole.

An embodiment of the present invention will now be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and differ from reality. Therefore, specific components should be determined with reference to the following description.

Further, the embodiments shown below are examples of apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is based on the shape, structure, arrangement, etc. of the component parts. It is not specific to the following. Various modifications can be made to the technical idea of the present invention within the technical scope defined by the claims.

A permanent magnet motor according to an embodiment of the present invention will be described below.

<Overall configuration of electric motor>
1 to 5 are diagrams for explaining the configuration of a permanent magnet motor 1 according to the first embodiment. As shown in FIGS. 1 to 5, this permanent magnet motor 1 is, for example, a brushless DC motor. This permanent magnet motor 1 is used to rotationally drive a blower fan mounted in an indoor unit of an air conditioner.

In the following, an inner rotor type permanent magnet electric motor 1 in which a rotor 3 having permanent magnets 31 is rotatably arranged inside a stator 2 that generates a rotating magnetic field will be described as an example. A permanent magnet motor 1 in this embodiment includes a stator 2 , a rotor 3 , and a motor shell 6 .

<Stator and rotor>
The stator 2 includes a stator core 21 having a cylindrical yoke and a plurality of teeth extending radially inward from the yoke, and windings 23 wound around the teeth via insulators 22 . . The stator 2 is covered with a motor shell 6 made of resin except for the inner peripheral surface of the stator core 21 .

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

<Bearing and bracket>
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 (anti-output side) of the shaft 35 of the rotor 3 . Ball bearings, for example, are used for the first bearing 41 and the second bearing 42 .

The first bracket 51 is made of metal (steel plate, aluminum, etc.) and is fixed to one end side of the motor shell 6 , that is, the output side of the shaft 35 . The first bracket 51 includes a cylindrical bracket main body 511 with one end open and the other end closed by a bottom plate portion 510 , and a first bearing housing provided on the bottom plate portion 510 for housing the first bearing 41 . A portion 512 is provided.

The bracket main body 511 is press-fitted to the outer peripheral surface of the motor shell 6 at the open end side. The first bearing accommodating portion 512 is formed in a cylindrical shape having a bottom projecting from the central portion of the bottom plate portion 510 to the side opposite to the motor shell 6 . The outer ring of the first bearing 41 is press-fitted into the cylindrical inner surface 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 protrudes outside from a through hole formed in the center of the bottom. It is

The second bracket 52 is made of metal (steel plate, aluminum, etc.) and is arranged on the other end side of the motor shell 6 , that is, on the counter-output side of the shaft 35 . The second bracket 52 has a second bearing housing portion 521 for housing the second bearing 42 and a flange portion 522 extending from the open end of the second bearing housing 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 during molding of the motor shell 6 and integrated with the motor shell 6 .

The first bearing 41 is housed in a first bearing housing portion 512 provided in the first bracket 51 , and the second bearing 42 is housed in a second bearing housing 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 connected.

<Specific Configuration of Rotor>
In the permanent magnet motor 1 configured as described above, in order to prevent electrolytic corrosion from occurring in the first bearing 41 and the second bearing 42, as shown in FIG. It has A specific configuration of the rotor 3 will be described below.

As shown in FIGS. 1 to 5, the rotor 3 includes a permanent magnet 31, an outer core 32, an insulating member 33, an inner core 34, and a shaft 35 from the outer diameter to the inner diameter. It has

As shown in FIGS. 1 and 6, the permanent magnet 31 is annularly formed of a plurality of (e.g., eight) permanent magnet pieces 311 so that N poles and S poles appear alternately at equal intervals in the circumferential direction. . It should be noted that the permanent magnet 31 may be a plastic magnet that is annularly formed by solidifying magnet powder with resin.

As shown in FIG. 3 , the outer core 32 is formed in an annular shape and positioned on the inner diameter side of the permanent magnet 31 . Although not shown, the outer core 32 has a plurality of (for example, four) protruding radially inwardly from an inner peripheral surface 321 (see FIG. 5) in order to secure a detent function with an insulating member 33, which will be described later. ) and an outer peripheral concave portion recessed from the inner peripheral surface 321 toward the outer diameter side. The plurality of outer-peripheral-side protrusions and outer-peripheral-side recesses extend in the direction of the central axis O and are arranged at regular intervals in the circumferential direction.

As shown in FIG. 3 , the inner peripheral core 34 is formed in an annular shape and positioned on the inner diameter side of the outer peripheral core 32 . Although not shown, the inner peripheral iron core 34 has a plurality (e.g., 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, which will be described later. inner peripheral recessed portion. The plurality of inner peripheral recesses extend in the direction of the central axis O and are arranged at regular intervals in the circumferential direction. A through hole 343 penetrating in the direction of the central axis O is provided in the center of the inner peripheral core 34 .

The insulating member 33 is made of dielectric resin such as PBT or PET, and is positioned between the outer core 32 and the inner core 34 . The insulating member 33 is formed integrally with the outer core 32 and the inner core 34 by filling resin between the outer core 32 and the inner core 34 . The insulating member 33 reduces the capacitance between the outer core 32 and the inner core 34 (a part of the capacitance between the windings 23 of the stator 2 and the shaft 35) to reduce the first bearing. The electric potential on the inner ring side of 41 and the second bearing 42 is lowered to match the electric potential 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 iron core 34 by press fitting or caulking.

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

The permanent magnet motor 1, which is used to rotationally drive a blower fan mounted on an air conditioner, is driven by a PWM type inverter, so the neutral point potential of the winding does not become zero, and 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 and inner rings of the first bearing 41 and the second bearing 42 due to the stray capacitance inside the permanent magnet motor 1 . When this shaft voltage reaches the dielectric breakdown voltage of the oil film inside the bearing, a current flows inside the bearing, causing 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. An axial hole 331 is formed, and a second axial hole 332 is formed at the other axial end for similarly reducing the electrostatic capacity of the rotor 3 . A plurality (for example, eight) of these first axial holes 331 and second axial holes 332 are formed at equal intervals in the circumferential direction. Between each of the plurality of first axial holes 331 and between each of the plurality of second axial holes 332, partition walls 334 are formed to allow adjacent first axial holes 331 and adjacent It separates the second axial holes 332 from each other.

Furthermore, as shown in FIGS. 3 to 5, the first axial hole 331 and the second axial hole 332 face each other in the axial direction and have the same depth at the central position in the axial direction. A wall portion 333 is provided to separate the two. By providing this wall portion 333, the bottom portion 335c of the first axial 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. It is A side wall 335a and a side wall 335b are formed along the axial direction from the bottom 335c of each of the first axial hole 331 and the second axial hole 332, respectively. As described above, the first axial hole 331 and the second axial hole 332 are formed in an arcuate end face shape along the circumferential direction due to the formation of the wall portion 333 and the partition wall 334, and the direction along the axial direction from the end face is formed in an arc shape. , and a plurality (for example, 8) of them are formed at regular intervals.

Here, for example, when the first axial hole 331 and the second axial hole 332 are formed in the rotor 3 which has a small radius and is thick in the axial direction, the radius of the rotor 3 becomes small. The radial length (width) R of the directional hole 331 and the second axial hole 332 is also reduced. In order to reduce the electrostatic capacitance of the rotor 3, the depth of the first axial hole 331 and the second axial hole 332 must be increased. However, if the depths of the first axial hole 331 and the second axial hole 332 are made too deep, the thickness of the wall portion 333 separating the first axial hole 331 and the second axial hole 332 becomes thin, resulting in insulation. Since the mechanical strength of the member 33 is lowered, the wall portion 333 with an appropriate thickness is required to ensure the mechanical strength.

Therefore, the depths of the first axial hole 331 and the second axial hole 332 are set in consideration of both reducing the electrostatic capacity of the rotor 3 and ensuring mechanical strength.

Since the insulating member 33 is formed by integrally molding a dielectric resin such as PBT or PET together with the outer core 32 and the inner core 34, the mechanical strength of the rotor 3 and the first axial hole 331 are reduced. Considering the draft angle of the mold when molding the second axial hole 332, as described above, as shown in FIGS. The hole 332 has an arc-shaped end surface along the circumferential direction due to the formation of the wall portion 333 and the partition wall 334, and has a depth in the direction along the axial direction from the end surface. A sufficient radial length (width) R of the hole 331 and the second axial hole 332 cannot be ensured.

By the way, generally, the coefficient of linear expansion of the insulating member 33 is larger than the coefficient of linear expansion of the outer peripheral iron core 32 and the inner peripheral iron core 34 made of metal. is greater than that of the outer core 32 and the inner core 34 .

As shown in FIG. 5(a), the insulating member 33 expands and shrinks in the side walls 335a and 335b of the insulating member 33 because the side walls 335a and 335b are thin in the radial direction and thick in the axial direction. In comparison, the axial direction is larger.

The amount of expansion and contraction of the wall portion 333 of the insulating member 33 can be divided into a component in the radial direction and a component in the axial direction. Axial expansion or contraction is greater than radial expansion or contraction.

Therefore, when considering the expansion of the wall portion 333 of the insulating member 33 due to the temperature rise, the expansion in the axial direction is greater than the expansion in the radial direction. Thermal stress is concentrated at the intersection of the bottom 335c of the axial hole 331 and the side walls 335a and 335b and the intersection of the bottom 335c of the second axial hole 332 and the side walls 335a and 335b.

Here, the degree of concentration of thermal stress in the first axial hole 331 will be examined. In addition, since the second axial hole 332 is formed symmetrically with the first axial hole 331 with respect to the wall portion 333, a description thereof will be omitted. Normally, as indicated by the dotted line in FIG. 7A, the bottom portion 335c is substantially perpendicular to the opposing side walls 335a and 335b of the insulating member 33 forming the first axial hole 331. 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, the thermal stress concentrates 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.

For this reason, in order to alleviate the concentration of thermal stress on the boundary portions P0a and P0b, as shown in FIG. Chamfering may be performed to form ramps 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 ramps 335d and 335e, and a region C forming the sidewalls 335a and 335b. Thus, the formation of the inclined portion 335d relaxes the thermal stress at the boundary portion P0a between the bottom portion 335c and the side wall 335a, and the formation of the inclined portion 335e relaxes the thermal stress at the boundary portion P0b between the bottom portion 335c and the side wall 335b. can be performed to suppress the concentration of thermal stress.

By the way, the insulating member 33 forming the first axial hole 331 has an axial thickness of the region A forming the wall portion 333, a radial thickness of the region C forming the side walls 335a and 335b, and a 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 reduced by absorbing the thermal expansion in the axial direction 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, in general, the metal inner core 34, outer core 32, and insulating member 33 expand when the temperature rises. The direction of expansion is divided into expansion in the axial direction and expansion from the inner peripheral side to the outer peripheral side. In addition, the coefficient of linear expansion of the insulating member 33 is relative to the coefficient of linear expansion of the inner peripheral core 34 fixed to the shaft 35 on the inner peripheral side of the insulating member 33 and the outer peripheral core 32 on the outer peripheral side of the insulating member 33. big. As a result, since the outer peripheral side iron core 32 that prevents the thermal expansion of the insulating member 33 does not exist in the inner peripheral side wall 335a and the inclined portion 335d, thermal expansion from the inner peripheral side to the outer peripheral side is prevented. However, in the outer peripheral side wall 335b and the inclined portion 335e, the outer peripheral iron core 32 exists at the outermost peripheral position of the insulating member 33, so that the outer peripheral iron core 32 prevents thermal expansion from the inner peripheral side to the outer peripheral side. be.

For this reason, the directions of thermal expansion indicated by the regions A and B are not perpendicular to the bottom surfaces and inclined surfaces of the bottom portion 335c and the inclined portion 335e on the outer peripheral side, but are inclined toward the outer peripheral side. As a result, the change in the direction of thermal expansion indicated by the regions B and C is greater than the change in the direction indicated by the inclined portion 335d and the side wall 335a on the inner peripheral side. The change is bigger. As a result, the magnitude of thermal stress concentration at the boundary portion P4 between the outer peripheral side inclined portion 335e and the side wall 335b becomes greater than the magnitude of the thermal stress concentration at the boundary portion P3 between the inner peripheral side inclined portion 335d and the side wall 335a.

Therefore, for example, when 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 of the first axial hole 331 is Since the length R is sufficiently large, the axial length L1 of the region B forming the inclined portions 335d and 335e can be increased by C chamfering cut at an angle of 45 degrees. It can be set to an axial length LS that can relax thermal stress. However, as shown in FIG. 7(a), when the radial length R of the first axial hole 331 is small, the C-chamfering of the same size causes the inner peripheral inclined portion 335d and the outer peripheral inclined portion 335e to be separated from each other. However, the thermal stress concentration is greater at the boundary portion P4 between the inclined portion 335e on the outer peripheral side and the side wall 335b than at the boundary portion P3 between the inclined portion 335d on the inner peripheral side and the side wall 335a. such a problem arises.

The axial length L1, which corresponds to the axial length of the region B, between the boundary portion P3 between the inner peripheral side inclined portion 335d and the side wall 335a and the boundary portion P0a between the side wall 335a and the bottom portion 335c is small thermal stress. The length in the axial direction can be set so as to relax the thermal stress according to the degree of concentration. However, the axial length L1 between the boundary portion P4 between the inclined portion 335e and the side wall 335b on the outer peripheral side and the boundary portion P0b between the side wall 335b and the bottom portion 335c reduces thermal stress according to the magnitude of large thermal stress concentration. It is short compared to the axial length _Ls1 that can be relaxed. Therefore, the thermal stress still concentrates on the boundary portion P4 between the inclined portion 335e on the outer peripheral side and the side wall 335b.

Therefore, in this embodiment, as shown in FIG. In order to alleviate the concentration of thermal stress, a first stress relaxation inclined portion 336a for alleviating the thermal stress at the inclination angle θ1 is formed around the boundary portion P0a between the inner side wall 335a and the bottom portion 335c by chamfering at an angle of 45 degrees. , and a second stress relaxation inclined portion 336b for relaxing thermal stress at the inclination angle θ1 is formed around the boundary portion P0b between the outer peripheral side wall 335b and the bottom portion 335c by chamfering at 45 degrees.
The first stress relieving sloped portion 336a is formed by extending the inner surface of the side wall 335a to the wall portion 333 in accordance with the small thermal stress concentration on the inner peripheral side. The axial length (hereinafter simply referred to as the axial length) L2 when projected in the radial direction is set to the axial length _Ls2 required for thermal stress relaxation. For example, the radial length R of the first axial hole 331 is set to 3 mm, and the length L2 required for thermal stress relaxation is set to 0.8 mm. This forms a boundary portion P3 between the side wall 335a on the inner peripheral side and the first stress relaxation inclined portion 336a.
In addition, the second stress relaxation sloped portion 336b is formed by extending the inner surface of the side wall 335b to the wall portion 333, depending on the magnitude of the large thermal stress concentration on the outer peripheral side. The axial length (hereinafter simply referred to as the axial length) L1 when projected in the radial direction is set to the axial length _Ls1 required for thermal stress relaxation. For example, the radial length R of the first axial hole 331 is set to 3 mm, and the length L1 required for thermal stress relaxation is set to 1.7 mm. As a result, a boundary portion P4 is formed between the side wall 335b on the outer peripheral side and the second stress relaxation inclined portion 336b.

Therefore, the axial length L1 required to relax the thermal stress of the second stress relaxation sloped portion 336b on the outer peripheral side is replaced by the axial length L1 required to relax the thermal stress of the first stress relaxation sloped portion 336a on the inner peripheral side. By setting the length longer than L2, the axial thermal expansion from the wall portion 333 due to the temperature rise is absorbed according to the difference in the degree of thermal stress concentration between the inner peripheral side and the outer peripheral side of the first axial direction hole 331 . can do. Therefore, the stress concentration at the boundary portion P3 between the inner peripheral side wall 335a and the first stress relaxation sloped portion 336a as well as the boundary portion P4 between the outer peripheral side wall 335b and the second stress relaxation sloped portion 336b can be relaxed. .
Note that the relationship between the axial lengths L1 and L2 required for alleviating the thermal stress shown in FIG. Accordingly, in the first stress relaxation inclined portion _336a on the inner peripheral side, the axial length L1 in FIG. The axial length L2 is set to be shorter _than the axial length L1 and equal to the axial length Ls2 required for thermal stress relaxation. Since the axial length L1 of is insufficient with respect to the axial length Ls1 required for thermal stress relaxation, the axial length _Ls1 required for thermal stress relaxation longer _than this axial length L1 ( L1). In order to secure such axial lengths L1 and L2, as shown in FIG. He is trying to shift from the center position of the radial direction of the 1st axial direction hole 331 to the inner peripheral side.

As a result of actual thermal stress analysis by the present applicant, even in a structure in which the radial length R of the first axial hole 331 can be only 3 mm, as shown in FIG. It became possible to reduce the thermal stress to about four-fifths compared to the case where only the heat treatment was performed.

Therefore, a first stress relaxation inclined portion 336a for relieving thermal stress is formed around the boundary portion P0a between the inner side wall 335a and the bottom portion 335c. A second stress relaxation sloped portion 336b for relaxing the thermal stress is formed in the second stress relaxation sloped portion 336b, and the axial length L1 (=Ls ₁ ) required for relaxing the thermal stress of the second stress relaxation sloped portion 336b is set to the first stress relaxation sloped portion 336b. By setting the length longer than the axial length L2 (=Ls ₂ ) required to relax the thermal stress of the inclined portion 336a, the bottom portion 335c of the first axial hole 331 is affected by the thermal expansion of the wall portion 333 in the axial direction. It is possible to eliminate the concentration of thermal stress on the outer peripheral side of the periphery (periphery of the bottom). For this reason, it is possible to suppress deterioration in durability due to repeated concentration of thermal stress on the insulating member 33, and to suppress the occurrence of cracks and fractures, thereby extending the life of the insulating member 33. Here, the periphery of the bottom portion 335c of the first axial hole 331 (the periphery of the bottom portion) means the periphery of the boundary portion P0a between the inner peripheral side wall 335a and the bottom portion 335c, or the boundary portion P0b between the outer peripheral side wall 335b and the bottom portion 335c. Shows the surroundings. In the following description, it will be abbreviated as bottom peripheral.

As with the first axial hole 331, the second axial hole 322 also has a first stress relaxation inclined portion 336a around the bottom portion of the second axial hole 332, as shown in FIG. 5(b). and the second stress relaxation sloped portion 336b, and the axial length L1 required to relax the thermal stress in the axial direction of the second stress relaxation sloped portion 336b is defined by the thermal stress in the axial direction of the first stress relaxation sloped portion 335d By setting the length longer than the axial length L2 required for alleviation of , the same effect as described above can be obtained.
Moreover, the axial length required for the first stress relaxation sloped portion 336a and the second stress relaxation sloped portion 336b is such that the position of the C chamfer is symmetrical across the radial center line of the first axial hole 331. It can be easily secured by simply shifting from the center to the inner peripheral side.

According to the first embodiment described above, the diameter of the rotor 3 is small, and in order to reduce the electrostatic capacity of the rotor 3, the first axial hole 331 and the second axial hole 332 are Even when the C chamfering of a sufficient size cannot be performed around the bottom portion, the periphery of the boundary portion P0a between the side wall 335a on the inner peripheral side and the bottom portion 335c with respect to the first axial hole 331 and the second axial hole 332 A first stress relaxation slanted portion 336a for relieving thermal stress is formed in the outer peripheral side wall 335b and a second stress relieving slanted portion 336b for relieving thermal stress around the boundary portion P0b between the outer peripheral side wall 335b and the bottom portion 335c. By setting the axial length L1 of the second stress relaxation inclined portion 336b longer than the axial length L2 of the first stress relaxation inclined portion 336a, the first axial hole 331 and the second axial hole 332 and the boundary portion P0b between the outer peripheral side wall 335b and the bottom portion 335c, and the boundary portion P4 between the outer peripheral side second stress relaxation inclined portion 336b and the side wall 335b of the first axial hole 331 and the second axial hole 332. concentration can be eased.

In the above description, the case where the wall portion 333 thermally expands due to the heat generated by the windings 23 of the stator 2 under the usage environment and driving state of the permanent magnet motor 1 has been described. The concentration of thermal stress around the bottoms of the first axial hole 331 and the second axial hole 332 can be alleviated even during thermal contraction 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 rotor 3 is provided with the insulating member 33, and the insulating member 33 is provided with a first axial hole 331 and a second axial hole 331. When the holes 332 are formed, concentration of thermal stress occurring in the insulating member 33, which is a problem when manufacturing the rotor 3 with a small diameter, can be alleviated. As a result, the electrostatic capacity of the rotor 3 can be reduced, and a small rotor 3 having durability can be manufactured, and the permanent magnet motor 1 itself can also be miniaturized.

In the above-described first embodiment, the first stress relaxation sloped portion 336a and the second stress relaxation sloped portion 336b are respectively C chamfered. An R-chamfered shape can also be applied instead of the chamfered shape. In addition, in the first embodiment, the first stress relaxation inclined portion 336a having the inclination angle θ1 and the outer peripheral side wall 335b are formed by chamfering 45 degrees around the boundary portion P0a between the inner peripheral side wall 335a and the bottom portion 335c. and the second stress relaxation sloped portion 336b having the slope angle θ1 is formed around the boundary portion P0b of the bottom portion 335c by C chamfering of 45 degrees. The first stress relaxation inclined portion 336a and the second stress relaxation inclined portion 336b on the outer peripheral side may have different inclination angles. 45 degrees, the length L1 is made larger than 1.7 mm by chamfering, the inclination angle of the second stress relaxation inclined portion 336b on the outer peripheral side is made 30 degrees, and the inclination angle on the outer peripheral side is smaller than the inclination angle on the inner peripheral side. You may

In the above embodiment, the axial length L1 of the _first stress relaxation inclined portion 336a is set equal to the axial length Ls1 required for stress relaxation, but the present invention is not limited to this. , the axial length L1 may be set longer _than the axial length Ls1 required for stress relaxation. Similarly, the axial length L2 of the _second stress relaxation inclined portion 336b may be set longer than the axial length Ls2 required for stress relaxation.

Next, a second embodiment of the invention will be described with reference to FIG.
In this second embodiment, instead of the first stress relaxation sloped portion 336a and the second stress relaxation sloped portion 336b having a C-chamfered shape, a two-stage stress relaxation sloped portion is applied. is. Since the first axial hole 331 and the second axial hole 332 are formed symmetrically with respect to the wall portion 333, the explanation of the second axial hole 332 is omitted.

That is, in the second embodiment, as shown in FIG. 8, the axial direction from the end of the inner peripheral side wall 335a corresponding to the axial length Ls ₂ (L4) capable of relaxing the thermal stress from the bottom 335c. With respect to the direction, for example, chamfering is performed at 15 degrees according to the dimensions shown in FIG. For example, the fourth stress relaxation inclined portion 336c2 having the second inclination angle θ3 is formed by chamfering at 45 degrees according to the dimensions shown in FIG.

By forming the fourth stress relaxation sloped portion 336c2 chamfered at 45 degrees, the angle θ3 between the fourth stress relaxation sloped portion 336c2 and the side wall 335a is formed to be 45 degrees, and the fourth stress relaxation sloped portion 336c2 and the bottom The angle θ4 between 335c is formed at 45 degrees. As a result, between the side wall 335a and the bottom portion 335c on the inner peripheral side of the first axial hole 331, a two-stage stress relaxation slope is formed by the combination of the third stress relaxation slope portion 336c1 and the fourth stress relaxation slope portion 336c2. A portion 336 is formed. Therefore, around the boundary portion P0a between the side wall 335a on the inner peripheral side of the first axial hole 331 formed in the insulating member 33 and the bottom portion 335c, the region A forming the wall portion 333 and the third stress relaxation inclined portion 336c1 and a region B forming the fourth stress relaxation inclined portion 336c2, and a region C forming the side wall 335a on the inner peripheral side.

Further, as shown in FIG. 8, from the end of the side wall 335b on the outer peripheral side corresponding to the axial length Ls ₁ (L3) in which the thermal stress can be relieved from the bottom 335c, in the axial direction, for example, 8 is chamfered at about 13 degrees to form a fifth stress relaxation inclined portion 336d1 with a third inclination angle θ5, and stress relaxation can be performed on the bottom portion 335c side. 45 degree chamfering is performed to form the sixth stress relaxation inclined portion 336d2 having the fourth inclination angle θ6.

By forming the sixth stress relaxation sloped portion 336d2 chamfered at 45 degrees, the angle θ6 between the sixth stress relaxation sloped portion 336d2 and the side wall 335b is formed to be 45 degrees, and the sixth stress relaxation sloped portion 336d2 and the bottom The angle θ7 between 335c is formed at 45 degrees. As a result, between the outer peripheral side wall 335b and the bottom portion 335c of the first axial hole 331, the combination of the fifth stress relaxation sloped portion 336d1 and the sixth stress relaxation sloped portion 336d2 provides a two-stage stress relaxation sloped portion. 336 is formed. Therefore, around the boundary portion P0b between the outer peripheral side wall 335b and the bottom portion 335c of the first axial hole 331 formed in the insulating member 33, the area A forming the wall portion 333, the fifth stress relaxation inclined portion 336d1 and It has a region B forming the sixth stress relaxation inclined portion 336d2 and a region C forming the side wall 335b on the outer peripheral side.

Further, as described above, the second tilt angle θ3 of the fourth stress relaxation sloped portion 336c2 with respect to the axial direction is set larger than the first tilt angle θ2 of the third stress relaxation sloped portion 336c1 with respect to the axial direction. The fourth inclination angle θ6 with respect to the axial direction of the inclined portion 336d2 is set larger than the third inclination angle θ5 with respect to the axial direction of the fifth stress relaxation inclined portion 336d1.

According to the second embodiment, the first axial hole 331 is provided with the third stress relaxation sloped portion 336c1 and the fourth stress relaxation sloped portion 336c2 on the inner circumference side around the bottom portion of the first axial hole 331, and the first axial hole 331 By providing two stages of the fifth stress relaxation sloped portion 336d1 and the sixth stress relaxation sloped portion 336d2 on the outer peripheral side of the bottom portion of the , the boundary portion between the third stress relaxation sloped portion 336c1 and the inner peripheral side wall 335a indicated by the arrow The change in the direction of thermal expansion at P3 can be made smaller than that in FIG. can be made smaller than in FIG. 7(b). Therefore, the concentration of thermal stress at the boundary portion P3 between the third stress relaxation sloped portion 336c1 and the inner peripheral side wall 335a and the boundary portion P4 between the fifth stress relaxation sloped portion 336d1 and the outer peripheral side wall 335b is reduced to the first degree. It can be suppressed more than the embodiment.

In the second embodiment, the two-step third stress relaxation sloped portion 336c1 and the fourth stress relaxation sloped portion 336c2 are formed on the inner peripheral side, and the two-step fifth stress relaxation sloped portion 336d1 and the sixth stress relaxation sloped portion 336d1 are formed on the inner peripheral side. The case where the stress relaxation inclined portion 336d2 is formed on the outer peripheral side has been described. The present invention is not limited to the configuration described above, and the stress relaxation inclined portion 336 may be formed in three or more stages. In addition, the present invention is not limited to the above configuration, and the one-step stress relaxation inclined portion 336 is formed on the inner peripheral side, and the two steps of the fifth stress-relaxation inclined portion 336d1 and the sixth stress-relaxation inclined portion 336d2 are formed. may be formed on the outer peripheral side to form the two-step stress relaxation inclined portion 336 only on the outer peripheral side.

Further, the third stress relaxation sloped portion 336c1 and the fourth stress relaxation sloped portion 336c2, and the fifth stress relaxation sloped portion 336d1 and the sixth stress relaxation sloped portion 336d2 are limited to those forming straight slopes by chamfering. Instead, a curved surface can be formed by chamfering.

Further, in each of the above-described embodiments, the end face shape of the first axial hole 331 and the second axial hole 332 is not limited to the arc shape along the circumferential direction. shape. Further, the number of the first axial holes 331 and the second axial holes 332 is not limited to eight, and may be any number as long as the mechanical strength of the insulating member 33 can be ensured. In addition, the number of the first axial holes 331 and the second axial holes 332 is not limited to a plurality. It may be formed in a shape continuous with the .

Further, in each of the above-described embodiments, the first axial hole 331 and the second axial hole 332 are formed symmetrically with respect to the wall portion 333, so that the first axial hole 331 and the second axial hole 332 Although the stress relieving slant portion 336 is formed around the bottom portion of each, the present invention is not limited to this. , the stress relaxation inclined portion may be formed around the bottom of either the first axial hole 331 or the second axial hole 332, which has a higher degree of concentration of thermal stress.

Furthermore, in each of the above embodiments, the case where the present invention is applied to the surface magnet type rotor 3 in which the permanent magnets 31 are arranged on the outer peripheral surface of the outer core 32 has been described, but the present invention is not limited to this. The present invention can also be applied to an embedded magnet type rotor in which slots extending in the axial direction are formed at the chord position with respect to the outer peripheral surface of the outer core 32 and permanent magnets are arranged in these slots.

REFERENCE SIGNS LIST 1 Permanent magnet motor 2 Stator 21 Stator core 22 Insulator 23 Winding 3 Rotor 31 Permanent magnet 311 Permanent magnet piece 32 Outer core 321 Inner surface 33 Insulating member 33a One end surface 33b Other end surface 331 First axial hole 332 Second axial hole 333 Wall portion 334 Partition wall 335a, 335b Side wall 335c Bottom portion 335d, 335e Inclined portion 336a First stress relaxation inclined portion 336b Second stress relaxation sloped portion 336c1 Third stress relaxation sloped portion 336c2 Fourth stress relaxation sloped portion 336d1 Fifth stress relaxation sloped portion 336d2 Sixth stress relaxation sloped portion 34 Inner core 341 Outer peripheral surface 343 Through hole 35 Shaft 41 First bearing 42 Second bearing 51 First bracket 511 Bracket main body 512 First bearing housing portion 52 Second bracket 521 Second bearing housing portion 522 Flange O central axis

Claims (5)

A stator fixed to the motor shell and a rotor arranged inside the stator,
The rotor includes an annular outer core in which permanent magnets are arranged, an annular inner core positioned on the inner diameter side of the outer core, and positioned between the outer core and the inner core. an insulating member, and a shaft that supports the inner peripheral iron core and is rotatably supported by a bearing on the outer shell of the motor,
The insulating member has a first axial hole opening at one axial end surface, a second axial hole opening at the other axial end surface, and a space between the first axial hole and the second axial hole. having a wall formed at
a bottom portion of the first axial hole is formed on one end side of the wall portion, and a bottom portion of the second axial hole is formed on the other end side of the wall portion;
Each of the first axial hole and the second axial hole has an inner side wall formed along the axial direction and an outer side wall formed along the axial direction. death,
At least one of the first axial hole and the second axial hole has a first stress relaxation inclined portion around a boundary portion between the inner circumferential side wall and the bottom portion for alleviating thermal stress. , the first stress relaxation inclined portion is inclined with respect to the inner peripheral side wall, and a second stress relaxation inclined portion for relaxing thermal stress is formed around a boundary portion between the outer peripheral side wall and the bottom portion. formed , wherein the second stress relaxation inclined portion is inclined with respect to the side wall on the outer peripheral side ;
A permanent magnet motor, wherein the axial length of the second stress relaxation inclined portion is longer than the axial length of the first stress relaxation inclined portion. A stator fixed to the motor shell and a rotor arranged inside the stator,
The rotor includes an annular outer core in which permanent magnets are arranged, an annular inner core positioned on the inner diameter side of the outer core, and positioned between the outer core and the inner core. an insulating member, and a shaft that supports the inner peripheral iron core and is rotatably supported by a bearing on the outer shell of the motor,
The insulating member has a first axial hole opening at one axial end surface, a second axial hole opening at the other axial end surface, and a space between the first axial hole and the second axial hole. a bottom portion of the first axial hole is formed on one end side of the wall portion, and a bottom portion of the second axial hole is formed on the other end side of the wall portion;
At least one of the first axial hole and the second axial hole has an axial length from the bottom that can relax thermal stress around the boundary portion between the inner peripheral side wall and the bottom. A third stress relaxation inclined portion inclined at a first inclination angle with respect to the axial direction is formed from the end portion of the side wall on the inner peripheral side of at least one of the first axial hole and the second axial hole corresponding to , a fourth stress relaxation sloped portion inclined at a second slope angle is formed between the third stress relaxation sloped portion and the bottom;
In at least one of the first axial hole and the second axial hole, around the boundary portion between the side wall on the outer peripheral side and the bottom portion, there is an axial length from the bottom portion that can relax the thermal stress. a fifth stress relaxation inclined portion inclined at a third angle of inclination with respect to the axial direction from the end portion of the inner peripheral side wall of at least one of the corresponding first axial hole and the second axial hole; A sixth stress relaxation sloped portion inclined at a fourth slope angle is formed between the fifth stress relaxation sloped portion and the bottom portion,
The axial length required for relaxing the thermal stress of the fifth stress relaxation sloped portion and the sixth stress relaxation sloped portion is adjusted to the thermal stress relaxation of the third stress relaxation sloped portion and the fourth stress relaxation sloped portion. A permanent magnet motor characterized by having an axial length longer than required. A second inclination angle of the fourth stress relaxation inclined portion with respect to the axial direction is set larger than a first inclination angle of the third stress relaxation inclined portion with respect to the axial direction. 3. The permanent magnet motor according to claim 2, wherein the inclination angle is set larger than the third inclination angle with respect to the axial direction of the fifth stress relaxation inclined portion. 4. The permanent magnet motor according to claim 2, wherein at least one of said first axial hole and said second axial hole is formed with three or more stages of stress relaxation inclined portions. A plurality of the first axial holes and the second axial holes are provided in a circumferential direction between the plurality of first axial holes and between the plurality of second axial holes. 5. A partition wall is formed in the first axial hole and the end faces of the second axial hole are arcuate along the circumferential direction. Permanent magnet motor as described.

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