JP7293807B2 - Electric motor - Google Patents

Description

The present invention relates to an electric motor having a bracket integrally provided with a heat sink.

2. Description of the Related Art Among conventional electric motors, there is known an inner rotor type permanent magnet electric 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.

Among such electric motors, there is one in which an aluminum heat sink (radiation fin) is attached to the outer surface of a metal bracket that closes the opening provided on the anti-output side of a cylindrical resin (motor shell). There was (for example, patent document 1). As a result, the heat generated in the control board for controlling the electric motor is transferred to the radiating fins, thereby improving the heat radiation performance of the heat generated in the control board inside the electric motor.

JP 2009-131127 A

In the prior art described above, the metal bracket and the radiation fins are separate parts, which increases the manufacturing cost. In addition, there is a large thermal resistance when heat is transferred from the metal bracket, which is a separate component, to the heat radiating fins. Furthermore, there is a problem that the electric motor becomes large in the axial direction due to an increase in the number of connected parts, and work for connecting the parts (for example, screwing) is also required.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electric motor that is miniaturized in the axial direction and has improved heat dissipation.

In order to solve the above problems, one aspect of the electric motor of the present invention is a cylindrical motor shell having an opening on one end face in the axial direction, and a coil and stator integrally formed with the motor shell. A stator having an iron core, a rotor arranged inside the stator, and a circuit board arranged inside the motor shell are provided. The electric motor includes a heat sink attached to the outer shell of the motor so as to block the opening of the one end face. The heat sink has a plurality of radiating fins standing outward on its outer surface, which is the one side in the axial direction, and the inner surface, which is the other side in the axial direction, faces the circuit board. are placed.

According to the electric motor of the present invention, the size is reduced in the axial direction and heat dissipation is improved.

1 is a longitudinal sectional view showing a permanent magnet motor according to the present invention; FIG. It is the perspective view (a) and top view (b) of the outer peripheral side iron core in the rotor of the permanent magnet motor which concerns on this invention. FIG. 4A is a perspective view (a) and a plan view (b) of an inner peripheral iron core in the rotor of the permanent magnet motor according to the present invention; 3A and 3B are a perspective view and a plan view of an insulating member in the rotor of the permanent magnet motor according to the present invention; FIG. 1 is a perspective view of a rotor of a permanent magnet motor according to the present invention; FIG. 6 is a plan view of the rotor of FIG. 5; FIG. FIG. 7 is a cross-sectional view taken along the line AA of FIG. 6; FIG. 7 is a cross-sectional view taken along the line BB of FIG. 6; FIG. 8 is a cross-sectional view taken along line CC of FIG. 7; FIG. 8 is a cross-sectional view taken along line DD of FIG. 7; 1 is a perspective view of a rotor, a shaft and a second bearing of a permanent magnet motor according to the present invention; FIG. 1 is a cross-sectional view showing a permanent magnet motor according to the present invention; FIG. It is the back side perspective view (a) and front side perspective view (b) of the stator of the permanent magnet motor which concerns on this invention. 13. It is a perspective view which shows the state before the rotor of FIG. 11 is combined with the stator of FIG. FIG. 14 is a perspective view showing a state after the rotor of FIG. 11 is combined with the stator of FIG. 13; It is the surface side perspective view (a) and back side perspective view (b) of the 2nd bracket of the permanent magnet motor which concerns on this invention. 1 is a perspective view of a permanent magnet motor according to the present invention; FIG. FIG. 2 is a partial cross-sectional view of the upper outer diameter side of FIG. 1; FIG. 2 is a partial enlarged view of the left side of FIG. 1;

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 do not necessarily correspond to 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.

An electric motor according to one embodiment of the present invention will be described below.

<Overall configuration of electric motor>
1 to 18 are diagrams illustrating the configuration of an electric motor 1 according to one embodiment. As shown in these figures, this permanent magnet motor 1 is, for example, a brushless DC motor. This electric motor 1 is used, for example, to rotationally drive a blower fan mounted on an outdoor unit of an air conditioner, and is screwed to the outdoor unit (not shown).

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 . A circuit board 72 for controlling the motor 1 is arranged inside the motor shell 6 in the permanent magnet motor 1 .

<Stator and rotor>
As shown in FIGS. 1 and 12 to 14, the stator 2 includes a stator core 21 having a cylindrical yoke portion and a plurality of tooth portions extending radially from the yoke portion, and an insulator 22. A wire (coil) 23 is wound around the teeth. The stator 2 is covered with a cylindrical motor shell 6 made of resin except for the inner peripheral surface of the stator core 21 . The motor shell 6 is formed with an opening 6O (see FIG. 13A) on the end face (one end face 6S in the axial direction) on the counter-output side in the direction of the central axis O (hereinafter referred to as the axial direction). . The central axes O of the electric motor 1, stator 2, insulator 22, rotor 3 and shaft 35 are all aligned.

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 arranged annularly on the outer peripheral surface facing the stator core 21 . The permanent magnet 31 is fixed around a shaft 35 via an outer core 32, an insulating member 33, and an inner core 34, which will be described later (see FIG. 11). This shaft 35 is supported by a first bearing 41 and a second bearing 42, as shown in FIG. By doing so, the rotor 3 is rotatably supported.

<Bearing and bracket>
The second bearing 42 rotatably supports one end (anti-output side) of the shaft 35 of the rotor 3 . The first bearing 41 rotatably supports the other end (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 arranged on one end side of the motor shell 6 in the axial direction, that is, on the output side of the shaft 35 . The first bracket 51 has a first bearing housing portion 511 for housing the first bearing 41 and a flange portion 512 extending from the open end of the first bearing housing portion 511 . The first bearing housing portion 511 is formed in a cylindrical shape having a bottom portion having a through hole for passing the shaft 35 therethrough, and the flange portion 512 of the first bracket 51 is insert-molded when the motor shell 6 is molded, and the motor It is integrated with the outer shell 6.

The outer ring of the first bearing 41 is press-fitted into the inner surface of the first bearing accommodating portion 511 , and the output side of the shaft 35 supported by the inner ring of the first bearing 41 is formed in the center of the bottom of the first bearing accommodating portion 511 . It protrudes outside from the through hole.

The second bracket (heat sink) 52 is made of metal (steel plate, aluminum, etc.), and as shown in FIGS. Fixed on the output side. As shown in FIG. 16, the second bracket 52 is generally disk-shaped. The second bracket 52 includes a disk-shaped bracket body portion 521 , a flange portion 524 (outer edge portion 520 ) formed so as to extend radially outward from one axial end of the bracket body portion 521 , and the second bearing 42 . has a second bearing housing 522 for housing and positioning the .

The second bracket 52 has a bracket body portion 521 press-fitted into the opening 6O of the motor shell 6, and a flange portion 524 in contact with one end face 6S of the motor shell 6 (outer edge portion 6E of the motor shell 6). there is

The bracket main body 521 is screwed to the outer edge 6E of the motor shell 6 at the flange part 524 so as to close the opening 6O provided in the end surface 6S on one side of the motor shell 6. installed. The second bearing accommodating portion 522 is formed in the central portion of the bracket main body portion 521 as a hole having a circular bottom surface recessed from the side of the motor shell 6 (the output side of the shaft 35). In this embodiment, a bearing 522 is arranged on the opening 6O side of the stator 2 .

The first bearing 41 is housed in a first bearing housing portion 511 provided in the first bracket 51 , and the second bearing 42 is housed in a second bearing housing portion 522 provided in the second bracket 52 . The first bearing 41 and the first bearing accommodating portion 511, and the second bearing 42 and the second bearing accommodating portion 522 are electrically connected.

The second bracket 52 functions not only as a bracket for closing the opening 6O provided in one end face 6S of the motor shell 6, but also as a heat sink in this embodiment. The side (outer surface) is provided with heat radiation fins 523 erected toward the outside (opposite side of the shaft 35). The second bracket 52 also includes a plurality of grooves 525 that are recessed from the outer surface of the second bracket 52 toward the output side (inner surface) of the shaft 35 in the axial direction. In the present embodiment, heat radiation fins 523 are formed between adjacent grooves 525 in the second bracket 52 . 17, the grooves 525 in this embodiment have a shape in which a plurality of linear grooves 525 are arranged in parallel. The pattern of the shape drawn by the plurality of grooves 525 on the outer surface of the second bracket 52 is arbitrary. For example, the grooves 525 may be formed so as to extend radially from the central axis O. Further, for example, when the second bracket 52 (heat sink) is die-cast, the radiation fins 523 may be provided with a contact portion 523a against which an extraction pin is applied when removing the second bracket 52 from the mold. . In this embodiment, the abutting portions 523a integrated with the heat radiating fins 523 are arranged on the same circumference around the central axis O. As shown in FIG.

The second bracket 52, which is a heat sink in this embodiment, integrally includes a heat radiation fin 523 at a position between the second bearing housing portion 522 and the outer edge portion 520 in the radial direction. As a result, for example, the radiation fins 523 are prevented from axially overlapping the outer edge portion 520 that connects the second bracket 52 and the motor shell 6 and the second bearing housing portion 522 that houses the second bearing 42 . Since the second bracket can be arranged, it is possible to prevent the second bracket from increasing in size in the axial direction, and the space of the electric motor 1 can be saved.

The output side (inner surface) of the shaft 35 of the second bracket 52 , which is a heat sink, is arranged to face the circuit board 72 and is in contact with the circuit board 72 via the heat transfer member 71 . As a result, the heat generated in the circuit board 72 is transferred to the second bracket 52, which is an aluminum heat sink, compared to the case where a metal bracket (not shown) is provided as a separate component between the heat sink and the circuit board. Since the heat is transmitted directly, the heat resistance can be reduced and the heat dissipation is improved.

As shown in FIG. 18, the base end portion 523b of the heat radiating fin 523 is located on the other side (inner surface side) in the axial direction of the end face 6S (outer edge portion 6E) on one side of the motor shell 6 in the axial direction. . As a result, it is possible to prevent the electric motor 1 from increasing in size in the axial direction, and to ensure the height of the radiating fins 523 so as to improve the heat radiation performance. Similarly, the base end portion 523 b of the heat radiation fin 523 is located on the other side (inner surface side) in the axial direction of the outer edge portion 520 (flange portion 524 ) of the second bracket 52 . As a result, it is possible to prevent the electric motor 1 from increasing in size in the axial direction, and to ensure the height of the radiating fins 523 so as to improve the heat radiation performance.

In addition, the distal end portion 523t of the radiation fin 523 is formed so as not to be located outside (on the counter-output side of the shaft 35, that is, one side in the axial direction) of the outer edge portion 520 (flange portion 524) in the axial direction. there is In other words, the distal end portion 523t of the heat radiation fin 523 is located on the inner surface side of the flange portion 524 (the output side of the shaft 35, that is, the other side in the axial direction) or flush with the flange portion 524 in the axial direction. As a result, it is possible to further prevent the electric motor 1 from increasing in size in the axial direction, and the flange portion 524 can prevent the tip portion 523t of the heat radiating fin 523 from being damaged due to an impact from the outside.

The radiation fins 523 are arranged radially inward of the outer edge portion 520 (flange portion 524 ) of the rotor 3 . The second bracket 52 has an annular portion 52a formed around the radiation fins 523. As shown in FIG. The annular portion 52a connects the plurality of radiation fins 523 (see FIG. 16A). In this embodiment, the outer edge portion 520 includes an annular portion 52a and a flange portion 524 located on the outer peripheral side of the annular portion 52a. have
As a result, since the outer diameter side of the heat radiation fins 523 is surrounded by the annular portion 52a (and the flange portion 524), it is possible to prevent direct external force from being applied to the heat radiation fins 523 (for example, when screwing), thereby preventing damage to the heat radiation fins 523. can be prevented. Moreover, since the plurality of heat radiation fins 523 are connected to each other via the annular portion 52a, the strength of the heat radiation fins 523 can be increased.

The second bracket 52 is formed, for example, by integral molding of aluminum die casting. That is, the annular portion 52a is integrally formed with the flange portion 524 and the heat radiation fins 523. As shown in FIG. Thereby, the strength of the annular portion 52a and the heat radiation fins 523 can be increased.

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

As shown in FIGS. 1 to 11, the rotor 3 includes a permanent magnet 31, an outer core 32, an insulating member (connecting portion) 33, and an inner core 34 from the outer diameter side to the inner diameter side. and a shaft 35 .

As shown in FIGS. 1, 11 and 12, the permanent magnet 31 is annularly formed of a plurality of (e.g., 8 or 10) permanent magnet pieces 311 so that N poles and S poles appear alternately at equal intervals in the circumferential direction. is formed in It should be noted that the permanent magnet 31 may be a plastic magnet that is annularly formed by solidifying magnet powder with resin.

The outer core 32 is formed in an annular shape, as shown in FIG. 2, and positioned on the inner diameter side of the permanent magnet 31, as shown in FIGS. The outer peripheral core 32 is recessed from the inner peripheral surface (see FIG. 2) toward the outer diameter side in order to secure the function of preventing rotation with the insulating member 33, which will be described later. axial direction) (for example, five in the circumferential direction). That is, the inner peripheral concave portion 321 is a key groove that prevents rotation of the insulating member 33 (a groove that prevents slippage between the rotating members. The key groove improves the fastening force between the members and improves the power transmission efficiency. can increase ). Further, the outer core 32 is provided with a plurality of (for example, 10 in the circumferential direction) outer protrusions 322 that protrude from the outer peripheral surface to the outer diameter side in order to position the permanent magnets 31 .

The plurality of inner peripheral recesses 321 extend in the axial direction from the end face of the insulating member 33 and are arranged at equal intervals in the circumferential direction. In this embodiment, two inner peripheral recesses 321 are arranged so as to extend from both ends of the outer peripheral core 32 in the axial direction. As a result, the outer core 32 has a partition wall 323 (retaining portion) between the inner peripheral recessed portions 321 adjacent in the axial direction. ) can be retained.

The plurality of outer peripheral side projections 322 extend in the axial direction and are arranged at regular intervals in the circumferential direction. In addition, each outer protrusion 322 is arranged to extend from one end to the other end of the outer core 32 in the axial direction.

As shown in FIG. 3, the inner core 34 is formed in an annular shape, and is located on the inner diameter side of the outer core 32 as shown in FIGS. The inner peripheral core 34 is recessed radially inward from the outer peripheral surface (see FIG. 3) and has a plurality of axially extending (eg, circumferential 6) of outer peripheral recesses 341 are provided. That is, the outer peripheral recess 341 functions as a key groove that prevents the insulating member 33 from rotating.

The plurality of outer peripheral recesses 341 extend in the axial direction and are arranged at equal intervals in the circumferential direction. In this embodiment, the outer peripheral recessed portion 341 is defined by a partition wall 344 (retaining portion) arranged in the center in the axial direction. Therefore, two outer peripheral recesses 341 are arranged so as to extend from both ends of the inner peripheral iron core 34 . As a result, in the inner peripheral core 34, a partition wall 344 exists between the outer peripheral recessed portions 341 adjacent in the axial direction. ) can be retained.

A through hole 343 is provided in the center of the inner peripheral core 34 so as to extend therethrough in the axial direction. The shaft 35 is passed through the through-hole 343 of the inner circumference iron core 34, and the shaft 35 and the inner circumference iron core 34 are connected. In addition, the inner peripheral core 34 may be provided with a plurality of through holes 342 for weight reduction between the through holes 343 and the outer peripheral surface of the inner peripheral core 34 . The plurality of through holes 342 are arranged at regular intervals in the circumferential direction so that the inner peripheral core 34 in which the through holes 342 are formed has a spoke-like shape when viewed from the axial direction.

The insulating member 33 is made of dielectric resin such as PBT (polybutylene terephthalate) or PET (polyethylene terephthalate), 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 insert molding in which resin is filled 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). By lowering the potential on the inner ring side of the first bearing 41 and the second bearing 42, the potential difference between the inner ring side and the outer ring side is adjusted to be small.

As shown in FIG. 4 , the insulating member 33 has, on its outer peripheral surface, (a plurality of) outer protrusions 338 that engage with the inner recesses 321 of the outer core 32 described above. Also, the insulating member 33 has (a plurality of) inner protrusions 339 that engage with the outer recesses 341 of the inner core 34 on the inner peripheral surface.

Here, an engaging portion (an inner recessed portion 321 and an outer The side convex portion 338) is used as a first concave-convex engaging portion, and is provided between the insulating member 33 and the inner peripheral core 34 to prevent rotation between the insulating member 33 and the inner peripheral core 34. The joining portion (the inner peripheral side convex portion 339 and the outer peripheral side concave portion 341) will be referred to as a second concave-convex engaging portion. As described above, in the present embodiment, the recesses of the uneven engagement portions (the first uneven engagement portion and the second uneven engagement portion) are formed in the outer core 32 and the inner core 34 to provide insulation. A case where the member (connecting portion) 33 is formed with the projections of the uneven engagement portion is illustrated.

It should be noted that whether the concave portions and the convex portions of the concave-convex engaging portions are arranged on either the rotor cores (32, 34) or the insulating member 33 may be reversed from the above case. For example, the convex portions of the concave-convex engaging portions may be provided on the outer core 32 and the inner core 34 , and the concave portions of the concave-convex engaging portions may be provided on the insulating member 33 .

The first concave-convex engaging portions 321, 338 and the second concave-convex engaging portions 339, 341, as shown in FIGS. A partition wall 323 (retaining portion) is formed between the outer peripheral side core 32 and the inner peripheral side core 34 because a partition wall 344 (retaining portion) is formed between the outer peripheral side recessed portions 341 adjacent in the axial direction. It is possible to prevent the insulating member 33 from coming off. Therefore, as described above, the first concave-convex engaging portions 321, 338 and the second concave-convex engaging portions 339, 341 can have the functions of preventing rotation and retaining by engaging the concaves and convexes.

Now, let us consider the shear stress that the concave-convex engaging portion that functions as a key (mechanical element that fastens the rotating body to the shaft) receives when the rotor 3 rotates. Assuming that the position where the concavo-convex engagement portion (key) is arranged is a position with a radius of r [m] from the central axis O on the shaft that transmits the torque of size T [N m], the shape of the concavo-convex engagement portion is uniform, the shear stress τ [Pa] acting on the concave-convex engaging portion can be represented by τ=α×T/r (α: constant of proportionality). Also, the radial position of the first uneven engagement portion provided between the outer core 32 and the insulating member 33 (that is, the inner diameter of the outer core 32) r1, the insulating member 33 and the inner core 34 When comparing the radial position of the second concave-convex engaging portion provided between (that is, the outer diameter of the inner peripheral iron core 34) r2, r1>r2 is always established. Furthermore, the torque transmitted between the outer core 32 and the insulating member 33 and the torque transmitted between the insulating member 33 and the inner core 34 can be considered equal. Therefore, the shear stress τ1 acting between the members on the outer diameter side (the first concave-convex engagement portion between the outer core 32 and the insulating member 33) acts between the members on the inner diameter side (inner core 34 and insulation) The shear stress τ2 acting on the second concave-convex engaging portion between the members 33 is always greater (that is, τ1<τ2 is always established). Therefore, by increasing the number of the second concave-convex engaging portions 339 and 341 in the circumferential direction more than the number of the first concave-convex engaging portions 321 and 338 in the circumferential direction, It is possible to reduce the shearing stress acting on each of the first concave-convex engaging portions 321 and 338 and further strengthen the anti-rotation of the insulating member 33 .

The shaft 35 is passed through a through hole 343 provided in the inner core 34 and fixed to the inner core 34 by press fitting, caulking, or the like.

A permanent magnet motor 1 used for rotating a blower fan mounted on an air conditioner is driven by a PWM type inverter, so that the neutral point potential of the winding does not become zero, and the common mode voltage and A voltage called 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 rotor 3 described above, the insulating member 33 is formed in a cylindrical shape, as shown in FIGS. A 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, 10) of these first axial holes 331 and second axial holes 332 are formed at equal intervals in the circumferential direction. Partition walls 334 are uniformly formed between each of the plurality of first axial holes 331 and between each of the plurality of second axial holes 332 to provide circumferentially adjacent first axial holes. 331 and circumferentially adjacent second axial holes 332 are separated from each other. Here, the plan view and bottom view of the rotor 3 are the same. The partition wall 334 enhances the mechanical strength of the insulating member 33 (connecting portion), and when the rotor 3 rotates, the partition wall 334 sufficiently transmits rotational motion power between the inner peripheral iron core 34 and the outer peripheral iron core 32. can be done.

Further, as shown in FIG. 7 , the first axial hole 331 and the second axial hole 332 are axially opposed to each other, and the axial center of the insulating member 33 (the axially opposed first axis A wall portion 333 is provided between the direction hole 331 and the second axial direction hole 332) so that the depths of the holes are the same. The wall portion 333 enhances the mechanical strength of the insulating member 33 (connecting portion), and when the rotor 3 rotates, sufficiently transmits the power of the rotational motion between the inner peripheral iron core 34 and the outer peripheral iron core 32. be able to. Further, by providing the 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. 335c is formed. Side walls 335a and 335b are formed along the axial direction from bottoms 335c of the first axial hole 331 and the second axial hole 332, respectively.

In this manner, the first axial hole 331 and the second axial hole 332 have a depth in the axial direction from both end surfaces due to the formation of the wall portion 333 . As shown in FIGS. 6 to 9, the first axial hole 331 and the second axial hole 332 each have an arcuate end surface shape along the circumferential direction when viewed from the axial direction. are formed at regular intervals (for example, 10 in the circumferential direction).

Here, for example, when forming the first axial hole 331 and the second axial hole 332 in the rotor 3 having a small radius and being thick in the axial direction, since the radius of the rotor 3 is small, The radial length (width) R of the hole 331 and the second axial hole 332 is also restricted to be small.

Further, since the insulating member 33 in this embodiment is formed by integrally molding a dielectric resin such as PBT or PET together with the outer peripheral iron core 32 and the inner peripheral iron core 34, the first axial hole 331 and the second axial hole 331 are formed. Considering the draft angle of the mold when molding the biaxial hole 332, the radial length (width) R of the first axial hole 331 and the second axial hole 332 cannot be increased.

In order to reduce the electrostatic capacitance of the rotor 3, for example, it is conceivable to increase the depth of the first axial hole 331 and the second axial hole 332 . 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. Here, in order to increase the mechanical strength, the axial thickness of the partition 323 (retaining portion) of the outer core 32 and the axial thickness of the partition 344 (retaining portion) of the inner core 34 are set to the wall portions 333 is approximately equal to the (axial) thickness of

In addition, in the present embodiment, as described above, the first axial hole 331 and the second axial hole 332 are configured so that the end face shape when viewed from the axial direction is the same in the circumferential direction as shown in FIGS. It is formed in an arc along the That is, by making the radial length (width) R of the first axial hole 331 and the second axial hole 332 constant in the circumferential direction, the size of the holes can be increased within a limited space. Moreover, the electrostatic capacity of the rotor 3 can be reduced.

As described above, the size and shape of the first axial hole 331 and the second axial hole 332 are determined in consideration of both reducing the electrostatic capacity of the rotor 3 and ensuring mechanical strength.

By the way, generally, the linear expansion coefficient of resin is 10 times or more larger than that of metal. Therefore, the insulating member 33 made of resin expands more when the temperature rises and contracts more when the temperature drops than the outer core 32 and the inner core 34 made of metal.

As shown in FIGS. 6 to 8, the insulating member 33 has side walls 335a and 335b that are thin in the radial direction and thick in the axial direction. Therefore, the amount of expansion and contraction of the side walls 335a and 335b of the insulating member 33 is greater in the axial direction than in the radial direction.

The amount of expansion and contraction of the wall portion 333 and the partition wall 334 of the insulating member 33 can be divided into a component in the radial direction and a component in the axial direction. Since it is regulated by the iron core 34, the amount of expansion and contraction in the axial direction tends to be greater than the amount of expansion and contraction in the radial direction.

Here, the insulating member 33 sandwiched between the outer core 32 and the inner core 34 shown in FIGS. It varies depending on where it was axially before it contracted. That is, since the insulating member 33 expands or contracts in both axial directions with the axial central portion as a boundary, the displacement of the insulating member 33 increases with increasing distance from the axial central portion. For example, the central portion in the axial direction (near the wall portion 333) has almost no axial displacement before and after expansion. On the other hand, the end portion in the axial direction (near the end portion 335d) undergoes a large axial displacement before and after the expansion. In addition, since the insulating member 33 has a small width in the radial direction and its expansion and contraction in the radial direction are restricted, the displacement in the radial direction due to expansion and contraction hardly changes regardless of the position in the axial direction. do not have.

Moreover, thermal stress is likely to concentrate at a portion of the insulating member 33 where expansion and contraction in the radial direction are restricted by the outer core 32 and the inner core 34 . Therefore, in this embodiment, the thermal stress concentrates on the wall portion 333 and the partition wall 334 of the insulating member 33 .

In this way, considering the expansion due to the temperature rise of the side walls 335a, 335b, the wall portion 333, and the partition wall 334 of the insulating member 33, the amount of expansion in the axial direction tends to be greater than the expansion in the radial direction. , the thermal stress concentrates particularly on the portion where the expansion is restricted and the portion where the amount of displacement is large.

Due to the influence of the expansion of the insulating member 33, thermal stress concentrates on the intersections of the wall portion 333 and the side walls 335a and 335b shown in FIG. By providing the (first concave portion), the force can be released to the first concave portion side, and the thermal stress can be relieved.
In addition, due to the expansion of the insulating member 33, the thermal stress concentrates on the ends of the side walls 335a and 335b in the axial direction. force can be released to relieve thermal stress.

On the other hand, in the partition wall 334 shown in FIG. 8, the expansion in the radial direction is restricted by the outer core 32 and the inner core 34, and the amount of displacement caused by the expansion near the end 335d in the axial direction is particularly large. . Therefore, due to the expansion of the insulating member 33, the vicinity of the axial end 335d of the insulating member 33 covering the inner and outer edges of the outer core 32 and the inner core 34 is particularly prone to cracking.

Therefore, in order to prevent the thermal cracking described above, the insulating member 33 is provided with gaps between the annularly arranged first axial holes 331 and between the second axial holes 332, as shown in FIGS. A third axial hole 336 is formed at one end in the axial direction, and a fourth axial hole 337 is similarly formed at the other end in the axial direction. These third axial hole 336 and fourth axial hole 337 (second recesses 336, 337) are identical to the first axial hole 331 and second axial hole 332 (first recesses 331, 332). They are formed on the circumference and arranged in an annular shape.
Further, the third axial hole 336 and the fourth axial hole 337 (second recesses) are provided in a plurality (for example, 10) are formed. Furthermore, each of the third axial hole 336 and the fourth axial hole 337 is arranged so as to axially overlap the partition wall 334 described above. Further, as shown in FIGS. 6 to 9, the third axial hole 336 and the fourth axial hole 337 are formed so that their end faces are arcuate in the circumferential direction when viewed from the axial direction. Further, the third axial hole 336 and the fourth axial hole 337 are continuous with the first axial hole 331 and the second axial hole 332, so that both end surfaces of the insulating member 33 in the axial direction have annular recesses. A groove is formed. That is, when the first axial hole 331 and the second axial hole 332 are the first recesses, and the third axial hole 336 and the fourth axial hole 337 are the second recesses, the insulating member (connecting portion) Annular recessed grooves (331, 336 and 332, 337) are provided on both axial end surfaces of 33 . This annular concave groove portion can uniformly disperse force in the circumferential direction by making the length (width) R in the radial direction on both end faces constant in the circumferential direction.

In particular, the bottoms of the second recesses (the third axial hole 336 and the fourth axial hole 337) (the positions of the axial ends of the partition wall 334) are aligned with the rotor core (the outer core 32 and the inner core). It has been confirmed that concentration of thermal stress in the insulating member 33 is suppressed when the iron core 34) is formed so as to be closer to the axial central portion than the axial end face of the iron core 34). Based on this, in the present embodiment, the depth of the third axial hole 336 and the fourth axial hole 337 is formed to be 5.5 mm from the axial end surface of the insulating member 33 . On the other hand, the depths of the first axial hole 331 and the second axial hole 332 are formed to be 16.5 mm from the axial end surface of the insulating member 33 .

Here, as shown in FIG. 19 and Table 1, the depth of the first axial hole 331 and the second axial hole 332 (the depth of the first concave portion) is M [mm], and the third axial hole 336 and the depth of the fourth axial hole 337 (the depth of the second recess) is S [mm], and the axial length (core thickness) of the outer core 32 and the inner core 34 is L [mm]. ], and the axial thickness (central wall thickness) of the wall portion 333 is assumed to be C [mm].
At this time, as can be seen from FIG. 19, the condition that the bottoms of the second recesses (336, 337) are closer to the axial center than the axial end faces of the rotor cores (32, 34) is as follows.
2M+C-2S<L
It is to be The rotor 3 is desirably designed to satisfy this conditional expression. That is, by satisfying this conditional expression, thermal cracking of the insulating member 33 can be prevented more reliably. Note that 2M+C matches the axial length of the insulating member 33 .

Therefore, by forming the third axial hole 336 and the fourth axial hole 337, which are the second recesses, the area of the insulating member 33 having a large axial length can be reduced to reduce the total volume of the insulating member 33. , and the amount of expansion and contraction of the insulating member 33 in the axial direction can be reduced. In addition, since the second recesses 336 and 337 are provided, the force applied to the vicinity of the end 335d in the axial direction can be released toward the second recesses, thereby relieving the thermal stress and concentrating the thermal stress. can be suppressed. For this reason, it is possible to suppress deterioration in durability due to concentration of thermal stress in the insulating member 33, and to suppress the occurrence of thermal cracks and cracks, thereby extending the life of the insulating member 33.

That is, as shown in FIGS. 5 to 8 , the plurality of third axial holes 336 (second recesses) correspond to the plurality of annularly arranged first axial holes 331 (first recesses). , and formed so as to connect circumferentially adjacent first axial holes 331 . Similarly, the plurality of fourth axial holes 337 (second recesses) are arranged between the plurality of annularly arranged second axial holes 332 (first recesses) and It is formed so as to connect the second axial holes 332 adjacent to each other in the direction. Thereby, concentration of thermal stress can be suppressed.

Further, the depths of the third axial hole 336 and the fourth axial hole 337 are formed smaller (shallower) than the depths of the first axial hole 331 and the second axial hole 332 . As a result, partition walls 334 that partition the second axial holes 332 are provided between the circumferentially adjacent first axial holes 331 and between the circumferentially adjacent second axial holes 332 . It is possible to increase the strength of the insulating member 33 (connecting portion).

Further, when the first axial hole 331 and the second axial hole 332 are used as the first concave portion, and the third axial hole 336 and the fourth axial hole 337 are used as the second concave portion, the insulating member (connecting portion) Annular recessed grooves (331, 336 and 332, 337) are provided on both axial end surfaces of 33 . As a result, the side walls 335a and 335b at the axial end portions of the insulating member 33 can expand toward the radially annular recessed groove portion side, so that the influence of thermal stress is further alleviated and thermal cracking of the insulating member 33 is prevented. can be prevented.

In the above description, the case where the insulating member 33 thermally expands due to the heat generated in the windings 23 of the stator 2 under the usage environment and driving state of the permanent magnet motor 1 has been described. In addition, heat is generated around the bottoms of the first axial holes 331 and the second axial holes 332 and around the top of the insulating member 33 during thermal contraction when the temperature drops depending on the usage environment and driving state of the permanent magnet motor 1 . Concentration of stress can be relieved.
In this embodiment, the insulating member 33 is provided with first concave portions 331 and 332 and second concave portions 336 and 337 in order to suppress thermal stress. The volume) can be reduced, the stress during thermal expansion and thermal contraction can be reduced, and thermal cracking of the insulating member 33 can be prevented.

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 hole 332 and the third axial hole 336 and the fourth axial hole 337 are formed, concentration of thermal stress generated in the insulating member 33, which is a problem when manufacturing the rotor 3 with a small diameter, is alleviated. can be made
As a result, it is possible to manufacture a compact rotor 3 that maintains the strength of connection between the outer core 32 and the inner core 34, increases the impedance between them, and reduces the electrostatic capacity of the rotor 3. can. In addition, the permanent magnet motor 1 including the rotor 3 can also be downsized.

As described above, the second bracket 52 that closes the opening 6O of the cylindrical motor shell 6 also functions as a heat sink, eliminating the need to combine the bracket and the heat sink separately. As a result, the number of parts to be combined with the electric motor 1 can be reduced, and an increase in the size of the electric motor 1 in the axial direction can be suppressed (that is, the size of the electric motor 1 can be reduced).
Further, in this embodiment, the heat generated in the circuit board 72 is directly transferred to the heat sink 52 made of aluminum compared to the case where a metal bracket is provided as a separate component (not shown) between the heat sink and the circuit board. heat dissipation is improved.

By the way, in each of the above-described 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 chord positions 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 10 Indoor unit 101 Base 102 Bottom plate 103 Upper plate 104 Side plate 21 Stator core 22 Insulator 23 Winding 3 Rotor 31 Permanent magnet 311 Permanent magnet Piece 32... Outer peripheral side core 321... Inner peripheral side concave portion (first concave/convex engaging portion)
323... Partition part (retaining part)
33... Insulating member (connecting part)
33a... One end face 33b... The other end face 331... First axial hole (first concave portion)
332... Second axial hole (first recess)
333... Wall part 334... Partition wall 335a, 335b... Side wall 335c... Bottom part 335d... End part 336... Third axial hole (second recess)
337... Fourth axial hole (second recess)
338 . . . Outer peripheral side convex portion (first uneven engagement portion)
339... Inner periphery side convex portion (second concave/convex engaging portion)
34... Inner peripheral side iron core 341... Outer peripheral side concave portion (second concave/convex engaging portion)
343... Through hole 344... Partition (retaining portion)
DESCRIPTION OF SYMBOLS 35... Shaft 41... 1st bearing 42... 2nd bearing 51... 1st bracket 511... 1st bearing accommodating part 512... Flange part 52... 2nd bracket (heat sink)
52a... Annular part 520... Outer edge part 521... Bracket body part 522... Second bearing accommodating part 523... Radiation fin 524... Flange part 525... Groove 6... Motor outer shell 6E... Outer edge part 6S... End face 71... Heat transfer member 72... Circuit Substrate O... Central axis

Claims (6)

A cylindrical motor shell having an opening on one end face in the axial direction, a stator including a coil and a stator iron core integrally formed with the motor shell, a rotor arranged inside the stator, An electric motor comprising: a circuit board arranged inside the motor shell; and a heat sink attached to the motor shell so as to block the opening of the one end face,
The heat sink has a disc-shaped bracket main body that is press-fitted into the opening, and a flange that extends radially outward from one end of the bracket main body in the axial direction,
The flange portion is attached to the one end face of the motor shell,
the outer surface of the bracket body, which is the one side in the axial direction , has a plurality of radiating fins standing outward,
The inner surface of the bracket body , which is the other side in the axial direction, is in thermal contact with the circuit board via a heat transfer member.
Electric motor. The electric motor according to claim 1,
the flange portion has a contact surface that contacts the one-side end surface of the motor outer shell,
A base end portion of the heat radiating fin is located on the other side in the axial direction of the contact surface of the flange portion . The electric motor according to claim 1 or 2 ,
A tip portion of the radiation fin is located on the other side of the flange portion or flush with the flange portion in the axial direction. The electric motor according to any one of claims 1 to 3,
The heat radiating fins are arranged radially inward of the flange portion of the rotor , and the outer diameter side of the heat radiating fins is surrounded by the flange portion.
Electric motor. The electric motor according to any one of claims 1 to 4,
The heat sink further has an annular portion formed around the heat radiation fins,
The annular portion connects the plurality of heat radiating fins to each other. The electric motor according to any one of claims 1 to 5,
The rotor further has a shaft extending in the axial direction and a bearing that rotatably supports one end of the shaft,
The bracket body portion of the heat sink is formed with a bearing accommodating portion that accommodates the bearing.

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