Electric motor, blower, and air conditioning device

Abstract

This electric motor comprises: a rotor having a shaft; a stator having an annular stator core surrounding the rotor from the outer side in the radial direction centered on the central axis of the shaft and a coil wound around the stator core; a mold resin part provided so as to cover the stator; and a substrate disposed on one side of the stator core in the axial direction of the shaft. A semiconductor element is disposed on the substrate. A distance Ri from the central axis to an inner end of the semiconductor element in the radial direction, a distance Ro from the central axis to an outer end of the semiconductor element in the radial direction, a distance Rm from the central axis to the inner peripheral surface of the mold resin part, and a distance Rc from the central axis to an inner end of the coil in the radial direction satisfy at least one of Ro ≥ Rm, Ro ≤ Rc, Ri ≥ Rm, and Ri ≤ Rc.

Description

Electric motors, fans and air conditioners

[0001] The present disclosure relates to an electric motor, a blower, and an air conditioning device.

[0002] Some electric motors, such as synchronous motors, have a circuit board on which semiconductor elements are mounted. Because the semiconductor elements are a heat source, suppressing the temperature rise of the circuit board is an issue. To address this issue, it has been proposed to provide a heat dissipation member in contact with the circuit board (see, for example, Patent Documents 1, 2, and 3).

[0003] Japanese Patent Application Laid-Open No. 2001-211663 (see FIG. 3) Japanese Patent Application Laid-Open No. 2004-357371 (see FIG. 1) Japanese Patent Application Laid-Open No. 2004-140893 (see FIG. 1)

[0004] However, further improvement in heat dissipation is required, taking into consideration the arrangement of semiconductor elements on the substrate.

[0005] The present disclosure has been made to solve the above problems, and aims to further improve heat dissipation.

[0006] The electric motor of the present disclosure includes a rotor having a shaft, an annular stator core that radially surrounds the rotor about the central axis of the shaft, a stator having a coil wound around the stator core, a molded resin portion that covers the stator, and a substrate that is disposed on one side of the stator core in the axial direction of the shaft. A semiconductor element is disposed on the substrate. The distance Ri from the central axis to the radially inner end of the semiconductor element, the distance Ro from the central axis to the radially outer end of the semiconductor element, the distance Rm from the central axis to the inner circumferential surface of the molded resin portion, and the distance Rc from the central axis to the radially inner end of the coil satisfy at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc.

[0007] According to the present disclosure, by satisfying at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc, heat generated in the semiconductor element on the substrate can be dissipated via the molded resin part facing the substrate, thereby improving the heat dissipation performance of the substrate.

[0008] FIG. 1 is a longitudinal cross-sectional view showing an electric motor according to a first embodiment. FIG. 2 is a cross-sectional view showing an enlarged portion of the electric motor according to the first embodiment. FIG. 3 is a cross-sectional view showing a rotor taken along line III-III in FIG. 1. FIG. 4 is a cross-sectional view showing a circuit board of an electric motor according to a second embodiment. FIG. 5 is a cross-sectional view showing a circuit board of an electric motor according to a comparative example. FIG. 6 is a cross-sectional view showing a circuit board of an electric motor according to a third embodiment. FIG. 7 is a cross-sectional view showing a circuit board of an electric motor according to a modified example of the third embodiment. FIG. 8 is a cross-sectional view showing an electric motor according to a fourth embodiment. FIG. 9 is a diagram showing a heat dissipation path in the electric motor according to the first embodiment, and a diagram showing a heat dissipation path in the electric motor according to the fourth embodiment. FIG. 10 is a diagram showing an air conditioner to which the electric motors of the respective embodiments can be applied, and a diagram showing an outdoor unit of the air conditioner.

[0009] Embodiment 1. <Overall configuration of electric motor 1> An electric motor according to embodiment 1 will be described. Fig. 1 is a longitudinal cross-sectional view showing electric motor 1 according to embodiment 1. Electric motor 1 is a synchronous motor, and is used, for example, in a blower of an air conditioning device 100 (Fig. 10(A)).

[0010] The electric motor 1 comprises a rotor 2 having a shaft 10, a stator 3 surrounding the rotor 2, a substrate 5, a molded resin part 4 covering the stator 3, a bracket 7 attached to the molded resin part 4, and bearings 11 and 12 supporting the shaft 10.

[0011] The central axis Ax of the shaft 10 defines the center of rotation of the rotor 2. Hereinafter, the direction of the central axis Ax will be referred to as the "axial direction." The radial direction about the central axis Ax will be referred to as the "radial direction." The circumferential direction about the central axis Ax will be referred to as the "circumferential direction."

[0012] The rotor 2 has a shaft 10 , a rotor core 20 fixed to the shaft 10 , and a plurality of permanent magnets 22 embedded in the rotor core 20 .

[0013] The shaft 10 is made of, for example, metal. The shaft 10 is fixed by press fitting or the like into a shaft hole 23 formed in the radial center of the rotor core 20. As will be described later, the shaft 10 protrudes from the molded resin portion 4 to one side in the axial direction. The protruding side of the shaft 10 is referred to as the long axis side, and the opposite side is referred to as the short axis side.

[0014] The rotor core 20 is an annular member centered on the central axis Ax. The rotor core 20 has a plurality of electromagnetic steel plates stacked in the axial direction. The rotor core 20 has a plurality of magnet insertion holes 21 arranged in the circumferential direction. A permanent magnet 22 is disposed in each magnet insertion hole 21.

[0015] The permanent magnets 22 are, for example, rare earth magnets or ferrite magnets. The number of permanent magnets 22 corresponds to the number of poles of the rotor 2. The number of poles of the rotor 2 is, for example, six or ten, but is not limited to this and may be two or more.

[0016] The stator 3 includes a stator core 30 , an insulator 31 attached to the stator core 30 , and a coil 32 wound around the stator core 30 via the insulator 31 .

[0017] The stator core 30 has a plurality of electromagnetic steel plates stacked in the axial direction. The stator core 30 has an annular yoke centered on the central axis Ax and a plurality of teeth extending radially inward from the yoke, with tip surfaces of the teeth facing the rotor 2. The tip surfaces of the teeth form the inner circumferential surface of the stator core 30.

[0018] The insulator 31 is made of a resin such as PBT (polybutylene terephthalate) and insulates the stator core 30 from the coil 32. The coil 32 is made of, for example, a magnet wire. The coil 32 is wound around the teeth of the stator core 30 via the insulator 31 by concentrated winding or distributed winding.

[0019] The molded resin portion 4 forms the outer shell of the electric motor 1. The molded resin portion 4 is made of a thermosetting resin such as an unsaturated polyester resin, more specifically, a bulk molding compound (BMC).

[0020] The molded resin portion 4 has a cylindrical portion 41 that is cylindrical and centered on the central axis Ax, and a flat portion 42 that is formed at the end of the cylindrical portion 41 on the major axis side. The cylindrical portion 41 surrounds and holds the stator 3 from the outside in the radial direction and both sides in the axial direction. For this reason, the cylindrical portion 41 is also referred to as a stator holding portion.

[0021] The flat plate portion 42 of the molded resin portion 4 faces the axial end face of the stator core 30. A central hole 42a is formed in the center of the flat plate portion 42, through which the shaft 10 passes. A bearing holder 43 that holds the bearing 11 is formed so as to surround the central hole 42a of the flat plate portion 42.

[0022] The substrate 5 is disposed on the minor axis side of the molded resin part 4 and faces the stator 3 in the axial direction. In other words, the substrate 5 is disposed on one axial side of the stator 3. The substrate 5 is supported by a support pin 61 provided in the molded resin part 4. A central hole 53 is formed in the center of the substrate 5, through which the shaft 10 passes.

[0023] The substrate 5 is, for example, a printed circuit board. The printed circuit board is an insulating plate-shaped substrate on which a wiring pattern made of a conductor is formed, and through holes may be formed as needed. The substrate 5 may also be called a circuit board.

[0024] The substrate 5 has a first surface S1 axially facing the stator 3 and a second surface S2 opposite thereto. A semiconductor element 50, more specifically, a MOSFET (metal oxide semiconductor field effect transistor) 51 and a microcomputer 52 are arranged on the first surface S1.

[0025] In order to electrically connect the wiring pattern of the substrate 5 to the coil 32 of the stator 3, the substrate 5 and terminals provided on the insulator 31 are connected by connecting portions (not shown). The arrangement of the semiconductor element 50 on the substrate 5 will be described later.

[0026] The bracket 7 is attached to the cylindrical portion 41 of the molded resin portion 4. The bracket 7 is made of metal and is fixed to the molded resin portion 4 by screws or adhesive. A space for accommodating the substrate 5 is formed between the bracket 7 and the molded resin portion 4.

[0027] The bracket 7 has a flat plate portion 71 that is perpendicular to the central axis Ax. A bearing holding portion 72 that holds the bearing 12 is formed in the radial center of the flat plate portion 71.

[0028] Bearings 11 and 12 rotatably support shaft 10. Bearing 11 is held by bearing holder 43 of molded resin portion 4 and is positioned axially on shaft 10 by E-ring 13. Bearing 12 is held by bearing holder 72 of bracket 7 and is positioned axially on shaft 10 by E-ring 14.

[0029] 2 is an enlarged cross-sectional view of a portion of the electric motor 1. The cylindrical portion 41 of the molded resin portion 4 is formed with a substrate-facing portion 41a that faces the substrate 5 in the axial direction, and an annular portion 41b that surrounds the substrate 5 from the radially outer side.

[0030] Support pins 61 for supporting the substrate 5 are provided on the substrate-facing portion 41a of the molded resin portion 4 so as to protrude in the axial direction. Here, four support pins 61 are arranged at equal intervals in the circumferential direction around the central axis Ax. The base portion of each support pin 61 is held by the molded resin portion 4. Each support pin 61 is fitted into a mounting hole 55 (FIG. 3) formed in the substrate 5. The number of support pins 61 is not limited to four, and may be two or more.

[0031] The insulator 31 has a body portion 31b formed on the teeth of the stator core 30, an inner wall portion 31a formed radially inside the body portion 31b, and an outer wall portion 31c formed radially outside the body portion 31b.

[0032] A coil 32 is wound around the body portion 31b of the insulator 31. The inner wall portion 31a abuts against a radially inner end portion 32a of the coil 32, and the outer wall portion 31c abuts against a radially outer end portion 32b of the coil 32. The inner wall portion 31a and the outer wall portion 31c hold the coil 32 from both radial sides.

[0033] An inner peripheral surface 45 of the cylindrical portion 41 of the molded resin portion 4 is located at the same radial position as the inner peripheral surface of the stator core 30. The inner wall portion 31a of the insulator 31 is located radially outward from the inner peripheral surface 45 of the cylindrical portion 41 of the molded resin portion 4. Hereinafter, the inner peripheral surface 45 of the cylindrical portion 41 of the molded resin portion 4 will be referred to as the "inner peripheral surface 45 of the molded resin portion 4."

[0034] Figure 3 is a cross-sectional view of the electric motor 1 taken along line III-III in Figure 1. As described above, the central hole 53 of the substrate 5 is a hole through which the shaft 10 (Figure 1) passes. In addition, mounting holes 55 that fit onto the support pins 61 of the molded resin part 4 are formed at four locations along the outer periphery 54 of the substrate 5.

[0035] A semiconductor element 50 is disposed on the first surface S1 of the substrate 5. Specifically, the semiconductor element 50 is a MOSFET 51 and a microcomputer 52. The MOSFET 51 is also referred to as a first semiconductor element, and the microcomputer 52 is also referred to as a second semiconductor element. The number of semiconductor elements 50 disposed on the substrate 5 is assumed to be n, where n is an integer of 2 or greater.

[0036] A Hall effect element (not shown) for detecting the rotation of the rotor 2 may be disposed on the first surface S1 of the substrate 5.

[0037] The MOSFET 51 is a switching element that controls the current flowing through the coil 32. The MOSFET 51 constitutes part of the inverter circuit. Two MOSFETs 51 are provided for each of the U phase, V phase, and W phase. Therefore, the total number of MOSFETs 51 is six. In FIG. 3, the six MOSFETs 51 are denoted by reference numerals 51a, 51b, 51c, 51d, 51e, and 51f.

[0038] The microcomputer 52 performs calculations necessary for controlling the rotation of the rotor 2. The calculations necessary for controlling the rotation of the rotor 2 include, for example, calculations of the rotational position of the rotor 2 based on the output of a Hall effect element disposed on the substrate 5. The number of microcomputers 52 is one.

[0039] The six MOSFETs 51 and the microcomputer 52 are arranged side by side in the circumferential direction. Here, the six MOSFETs 51 are arranged side by side on one side of the central axis Ax, and the microcomputer 52 is arranged on the other side.

[0040] The number of MOSFETs 51 is not limited to six, and the number of microcomputers 52 is not limited to 1. Other examples of the arrangement of MOSFETs 51 and microcomputers 52 will be described in the second and third embodiments.

[0041] The MOSFET 51 and the microcomputer 52 each have a radially inner end Ei and a radially outer end Eo. In the following description, the MOSFET 51 and the microcomputer 52 will be collectively referred to as the semiconductor element 50.

[0042] 2, the distance from the central axis Ax to the radially inner end Ei of the semiconductor element 50 is defined as Ri, and the distance from the central axis Ax to the radially outer end Eo of the semiconductor element 50 is defined as Ro.

[0043] Furthermore, the distance from the central axis Ax to the inner circumferential surface 45 of the molded resin portion 4 is defined as Rm. The distance from the central axis Ax to the radially inner end 32a of the coil 32 is defined as Rc.

[0044] These distances Ri, Ro, Ri, and Rm satisfy at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc.

[0045] <Operation> The operation of the electric motor 1 of the first embodiment will be described with reference to Figure 2. Rotation control by the microcomputer 52 on the circuit board 5 and switching operation by the semiconductor element 50 cause a current to flow through the coil 32 of the stator 3. The current flowing through the coil 32 and the magnetic field of the permanent magnet 22 of the rotor 2 generate a torque that rotates the rotor 2, causing the rotor 2 to rotate.

[0046] The heat generated by the current in the coil 32 is mainly radiated to the outside of the electric motor 1 via the molded resin portion 4. Furthermore, a portion of the heat generated by the current in the coil 32 moves from the stator core 30 to the rotor core 20 via the air gap, and is radiated to the outside of the electric motor 1 via the shaft 10. The heat radiated to the outside of the electric motor 1 is dissipated into the air surrounding the electric motor 1.

[0047] Furthermore, heat generated by the semiconductor element 50 and the microcomputer 52 on the substrate 5 mainly moves to the molded resin part 4 via the support pins 61 and is dissipated from the molded resin part 4 to the outside of the electric motor 1. Furthermore, part of the heat that has moved to the molded resin part 4 via the support pins 61 moves from the molded resin part 4 to the rotor core 20 and is dissipated to the outside of the electric motor 1 via the shaft 10.

[0048] Furthermore, when a current flows through the coil 32, a magnetic field is generated in the stator core 30 and flows into the rotor core 20. As the rotor 2 rotates, the magnetic field flowing from the stator core 30 into the rotor core 20 changes, and this change in the magnetic field generates heat in the stator core 30 and the rotor core 20. The heat generated in the stator core 30 and the rotor core 20 is dissipated to the outside of the electric motor 1 via the molded resin portion 4 or the shaft 10.

[0049] In this way, heat generated in the electric motor 1 is dissipated to the outside of the electric motor 1 via the molded resin portion 4, etc. However, as the output of the electric motor 1 has increased in recent years, the current flowing through the coil 32 tends to increase. In particular, when the current flowing through the coil 32 increases, the increase in the amount of heat generated by the microcomputer 52 is small, but the amount of heat generated by the MOSFET 51 increases significantly. As a result, the temperature of the substrate 5 is likely to rise, making it difficult to dissipate heat sufficiently.

[0050] In the first embodiment, as described above, the distance Ri from the central axis Ax to the radially inner end Ei of the semiconductor element 50, the distance Ro from the central axis Ax to the radially outer end Eo of the semiconductor element 50, the distance Rm from the central axis Ax to the inner circumferential surface 45 of the molded resin part 4, and the distance Rc from the central axis Ax to the radially inner end 32 a of the coil 32 satisfy at least one of Ro ≧ Rm, Ro ≦ Rc, Ri ≧ Rm, and Ri ≦ Rc. These requirements will be explained in order.

[0051] Ro≧Rm means that the radially outer end Eo of the semiconductor element 50 is located radially outward of the inner circumferential surface 45 of the molded resin part 4. In other words, at least a part of the semiconductor element 50 faces the substrate facing part 41 a of the molded resin part 4 in the axial direction.

[0052] 2, the heat generated by the semiconductor element 50 moves through the air to the substrate-facing portion 41a of the molded resin part 4. The heat transferred from the semiconductor element 50 to the substrate-facing portion 41a of the molded resin part 4 moves toward the outer periphery of the molded resin part 4 and is dissipated to the outside of the electric motor 1. This improves the heat dissipation effect from the semiconductor element 50.

[0053] Furthermore, Ro≦Rc means that the radially outer end Eo of the semiconductor element 50 is located radially inward of the radially inner end 32 a of the coil 32 of the stator 3. In other words, the semiconductor element 50 does not face the coil 32 in the axial direction.

[0054] As described above, not only heat from the semiconductor element 50 but also heat from the coil 32 moves to the molded resin part 4. Since the semiconductor element 50 and the coil 32 are not axially opposed to each other, the heat of the semiconductor element 50 can be moved to areas of the molded resin part 4 that are not heated by the heat of the coil 32. This further improves the heat dissipation effect from the semiconductor element 50.

[0055] Furthermore, Ri≧Rm means that the radially inner end Ei of the semiconductor element 50 is located radially outward of the inner circumferential surface 45 of the molded resin part 4. In other words, the entire semiconductor element 50 faces the substrate facing part 41 a of the molded resin part 4 in the axial direction.

[0056] Therefore, the heat generated in the semiconductor element 50 is more effectively transferred to the substrate-facing portion 41 a of the molded resin portion 4 through the air and dissipated to the outside of the motor 1. Therefore, the heat dissipation effect from the semiconductor element 50 can be further improved.

[0057] Furthermore, Ri≦Rc means that the radially inner end Ei of the semiconductor element 50 is located radially inward of the radially inner end 32 a of the coil 32 of the stator 3. In other words, at least a part of the semiconductor element 50 does not face the coil 32 in the axial direction.

[0058] Since at least a portion of the semiconductor element 50 and the coil 32 do not face each other in the axial direction, heat can be transferred from at least a portion of the semiconductor element 50 to an area in the molded resin part 4 that is not heated by the heat of the coil 32. Therefore, the heat dissipation effect from the semiconductor element 50 can be further improved.

[0059] In this way, by satisfying at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc, the heat dissipation effect from the semiconductor element 50 can be improved.

[0060] In particular, Ro≧Rm is the most important condition for improving the heat dissipation effect because it means that at least a portion of the semiconductor element 50 faces the substrate-facing portion 41a of the molded resin portion 4 in the axial direction. Therefore, it is desirable to achieve a combination of Ro≧Rm and at least one of Ro≦Rc, Ri≧Rm, and Ri≦Rc. Furthermore, it goes without saying that the highest heat dissipation effect can be achieved if all of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc are achieved.

[0061] Here, the case where the semiconductor element 50 is disposed on the first surface S1 of the substrate 5 has been described, but the semiconductor element 50 may be disposed on the second surface S2 of the substrate 5, or may be disposed separately on the first surface S1 and the second surface S2. In this case as well, if at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc is satisfied, the heat dissipation efficiency can be improved.

[0062] However, if the semiconductor element 50 is placed on the first surface S1, the distance between the semiconductor element 50 and the substrate-facing portion 41a of the molded resin part 4 is short, and heat can easily move from the semiconductor element 50 to the molded resin part 4, which is advantageous in terms of improving heat dissipation efficiency.

[0063] It is also desirable that at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc be satisfied for both the MOSFET 51 and the microcomputer 52. However, the present invention is not limited to this example, and it is sufficient that at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc be satisfied for at least one of the MOSFET 51 and the microcomputer 52.

[0064] In particular, since the amount of heat generated by the MOSFET 51 increases significantly as the output of the motor 1 increases, it is desirable that at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc be satisfied for the MOSFET 51.

[0065] Although the case where the MOSFET 51 and the microcomputer 52 are arranged on the substrate 5 has been described here, only the MOSFET 51 or only the microcomputer 52 may be arranged on the substrate 5. Furthermore, semiconductor elements other than the MOSFET and the microcomputer may be arranged on the substrate 5.

[0066] Furthermore, a heat dissipation member may be added between the second surface S2 of the substrate 5 and the bracket 7 so as to be in contact with them. In this case, the heat generated by the semiconductor element 50 can also be dissipated from the bracket 7 via the heat dissipation member.

[0067] Effect of the Embodiment As described above, the electric motor 1 of the first embodiment includes the rotor 2 having the shaft 10, the stator 3 having the annular stator core 30 that radially surrounds the rotor 2 from the outside and the coil 32 wound around the stator core 30, the molded resin portion 4 that is provided to cover the stator 3, and the substrate 5 that is arranged on one axial side of the stator core 30. The semiconductor element 50 is arranged on the substrate 5. The distance Ri from the central axis Ax to the radially inner end Ei of the semiconductor element 50, the distance Ro from the central axis Ax to the radially outer end Eo of the semiconductor element 50, the distance Rm from the central axis Ax to the inner circumferential surface 45 of the molded resin portion 4, and the distance Rc from the central axis Ax to the radially inner end 32 a of the coil 32 satisfy at least one of Ro ≧ Rm, Ro ≦ Rc, Ri ≧ Rm, and Ri ≦ Rc.

[0068] Therefore, the heat generated in the semiconductor element 50 on the substrate 5 can be transferred to the molded resin part 4 through the air and dissipated to the outside of the motor 1. This improves the heat dissipation effect from the semiconductor element 50.

[0069] Furthermore, the semiconductor element 50 is disposed on a first surface S1 of the substrate 5 facing the stator 3, and the molded resin part 4 has a substrate facing part 41a facing the substrate 5, and this substrate facing part 41a faces the semiconductor element 50 across air in the axial direction. Therefore, heat from the semiconductor element 50 can be easily transferred to the molded resin part 4 via the air, improving the heat dissipation effect.

[0070] In addition, since support pins 61 that support the substrate 5 are attached to the molded resin part 4, the heat generated by the semiconductor element 50 can be transferred to the molded resin part 4 via the support pins 61 and dissipated to the outside of the motor 1.

[0071] Furthermore, since the substrate 5 is housed in the space formed between the molded resin part 4 and the bracket 7 , the semiconductor element 50 on the substrate 5 can be protected by the molded resin part 4 and the bracket 7 .

[0072] Embodiment 2. Figure 4 is a diagram showing a substrate 5A of an electric motor according to embodiment 2, and corresponds to a cross-sectional view taken along line III-III in Figure 1. In embodiment 2, the arrangement of semiconductor elements 50 (i.e., MOSFETs 51 and microcomputers 52) on substrate 5A differs from that in embodiment 1.

[0073] The number of semiconductor elements 50 arranged on the substrate 5A is assumed to be n, where n is an integer equal to or greater than 2. In the second embodiment, the substrate 5A is divided into n regions R1 to Rn in the circumferential direction, and one semiconductor element 50 is arranged in each of the regions R1 to Rn. It is desirable that the regions R1 to Rn of the substrate 5A be set at equal intervals in the circumferential direction.

[0074] 4, n=7. That is, the substrate 5A is divided into seven regions R1 to R7 in the circumferential direction. MOSFETs 51a to 51f are arranged in the regions R1 to R6, and the microcomputer 52 is arranged in the region R7.

[0075] As described in the first embodiment, with regard to the arrangement of the semiconductor element 50, at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc shown in FIG. 2 is satisfied.

[0076] Fig. 5 is a diagram showing a substrate 5E of a motor according to a comparative example, and corresponds to a cross-sectional view taken along line III-III in Fig. 1. In this comparative example, the substrate 5E is divided into four regions R1 to R4 in the circumferential direction. Regions R1 to R3 are located on one side of the central axis Ax, and region R4 is located on the opposite side of the central axis Ax.

[0077] In region R1 of substrate 5E, MOSFETs 51a and 51b are arranged side by side in the radial direction. In region R2, MOSFETs 51c and 51d are arranged side by side in the radial direction. In region R3, MOSFETs 51e and 51f are arranged side by side in the radial direction. In region R4, a microcomputer 52 is arranged.

[0078] In the substrate 5E of the comparative example, the MOSFETs 51, which are heat sources, are concentrated on one side (the upper side in FIG. 5 ) of the central axis Ax. In addition, in the regions R1 to R3, two MOSFETs 51 are arranged side by side in the radial direction in each region. Therefore, the heat generated by the MOSFETs 51 is likely to cause a local temperature rise in the substrate 5E.

[0079] 4, the substrate 5A is divided in the circumferential direction into regions R1 to Rn, the number of which is equal to the number n of semiconductor elements 50, and one semiconductor element 50 is disposed in each of the regions R1 to Rn. Since the semiconductor elements 50 are disposed in a dispersed manner in the circumferential direction, local temperature increases in the substrate 5A can be suppressed, and the temperature distribution in the substrate 5A can be made uniform.

[0080] Except for the above points, the electric motor of the second embodiment is configured similarly to the electric motor 1 of the first embodiment.

[0081] As described above, in embodiment 2, the substrate 5A is divided circumferentially into regions R1 to Rn, the number of which is equal to the number n of semiconductor elements 50, and one semiconductor element 50 is arranged in each of the regions R1 to Rn, thereby suppressing local temperature increases in the substrate 5A.

[0082] In particular, if the regions R1 to Rn of the substrate 5A are divided at equal intervals in the circumferential direction, the temperature distribution of the substrate 5A can be made more uniform.

[0083] Embodiment 3. Figure 6 is a diagram showing a substrate 5B of an electric motor according to embodiment 3, and corresponds to a cross-sectional view taken along line III-III in Figure 1. In embodiment 3, the arrangement of semiconductor elements 50 (i.e., MOSFETs 51 and microcomputers 52) on substrate 5B differs from that in embodiment 2.

[0084] Of the n semiconductor elements 50 arranged on the substrate 5A, the number of MOSFETs 51 is defined as m, and the number of microcomputers 52 is defined as r, where m is an integer of 2 or more, and r is an integer of 1 or more.

[0085] In the third embodiment, the substrate 5B is divided into m regions R1 to Rm in the circumferential direction, and one MOSFET 51 is disposed in each of the regions R1 to Rm. The regions R1 to Rm of the substrate 5B are preferably set at equal intervals in the circumferential direction. The microcomputer 52 is disposed across two adjacent regions R1 to Rm.

[0086] In the example shown in Fig. 4, m = 6 and r = 1. That is, the substrate 5B is divided into six regions R1 to R6 in the circumferential direction. MOSFETs 51a to 51f are arranged in the regions R1 to R6. The microcomputer 52 is arranged across the regions R1 and R2.

[0087] As described in the first embodiment, with regard to the arrangement of the semiconductor element 50, at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc shown in FIG. 2 is satisfied.

[0088] As explained in the first embodiment, as the output of the electric motor increases, the amount of heat generated by the MOSFETs 51 increases significantly, but the increase in the amount of heat generated by the microcomputer 52 is small. Therefore, it is more necessary to disperse the MOSFETs 51 in the circumferential direction than the microcomputers 52.

[0089] Therefore, in the third embodiment, the substrate 5B is divided into regions R1 to Rm, the number of which is equal to the number m of the MOSFETs 51 that generate a large amount of heat, and each of the regions R1 to Rm is provided with one MOSFET 51. Also, the microcomputer 52 that generates a small amount of heat is provided so as to straddle two adjacent regions.

[0090] In this way, the MOSFETs 51 that generate a large amount of heat are arranged in a dispersed manner in the circumferential direction, which can suppress a local temperature rise in the substrate 5B. In particular, if the regions R1 to Rm of the substrate 5B are arranged at equal intervals in the circumferential direction, the effect of suppressing a local temperature rise in the substrate 5B can be enhanced.

[0091] Except for the above points, the electric motor of the third embodiment is configured similarly to the electric motor 1 of the first embodiment.

[0092] As described above, in the third embodiment, the substrate 5B is divided circumferentially into regions R1 to Rm, the number of which is equal to the number m of semiconductor elements 50 (e.g., MOSFETs 51) that generate a large amount of heat, and one semiconductor element 50 (e.g., MOSFET 51) that generates a large amount of heat is disposed in each of the regions R1 to Rm, thereby making it possible to suppress local temperature increases in the substrate 5B.

[0093] In particular, if the regions R1 to Rm of the substrate 5B are divided at equal intervals in the circumferential direction, the temperature distribution of the substrate 5B can be made more uniform.

[0094] Modification Example Figure 7 is a diagram showing a substrate 5C of an electric motor according to a modification example of the third embodiment, and corresponds to a cross-sectional view taken along line III-III in Figure 1. The modification example of the third embodiment differs from the third embodiment in that the microcomputer 52 is not disposed on the substrate 5C.

[0095] Depending on the driving method of the electric motor, there may be cases where MOSFETs 51 are arranged on substrate 5C without microcomputer 52. In this case, as shown in Fig. 7, substrate 5B may be divided into regions R1 to R6, the number of which is equal to the number of MOSFETs 51, and one MOSFET 51 may be arranged in each of regions R1 to R6.

[0096] In this case as well, the MOSFETs 51 are arranged in a dispersed manner in the circumferential direction, so that a local temperature rise in the substrate 5C can be suppressed.

[0097] 8 is a cross-sectional view showing an electric motor 1D of embodiment 4. The electric motor 1D of embodiment 4 differs from the electric motor 1 of embodiment 1 in the support structure of the substrate 5.

[0098] As shown in Figure 8, in the electric motor 1D of embodiment 4, instead of the support pin 61 (Figures 1 and 2) described in embodiment 1, a step portion 46 is integrally formed in the molded resin portion 4 as a board support portion that supports the board 5.

[0099] The step portion 46 is formed to protrude in the axial direction from the substrate-facing portion 41 a of the molded resin portion 4, and abuts against an outer peripheral region of the first surface S1 of the substrate 5. The step portion 46 also extends in an annular shape centered on the central axis Ax.

[0100] A protrusion 47 that protrudes in the axial direction is formed on the step portion 46. The protrusion 47 fits into a mounting hole 55 (FIG. 2) formed in the substrate 5. This fixes the substrate 5 to the step portion 46 of the molded resin portion 4.

[0101] As described in the first embodiment, with regard to the arrangement of the semiconductor element 50, at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc shown in FIG. 2 is satisfied.

[0102] Fig. 9A is a schematic diagram showing heat dissipation paths in the electric motor 1 (Figs. 1 and 2) of the first embodiment described above. Fig. 9B is a schematic diagram showing heat dissipation paths in an electric motor 1D of the fourth embodiment.

[0103] 9A, in the electric motor 1 of the first embodiment, heat generated in the semiconductor element 50 moves through the air to the substrate facing portion 41a of the molded resin portion 4 as shown by arrow A. Furthermore, the heat generated in the semiconductor element 50 moves within the substrate 5 as shown by arrows B and C, moves from the support pin 61 to the substrate facing portion 41a as shown by arrow D, and then moves toward the outer periphery of the molded resin portion 4 as shown by arrow E.

[0104] The support pin 61 faces the coil 32 in the axial direction. Therefore, in the molded resin part 4, the heat dissipation path from the substrate 5 (indicated by arrow E) and the heat dissipation path from the coil 32 are close to each other. Since the temperature rises in the area where these heat dissipation paths are close to each other, the efficiency of heat dissipation from the support pin 61 may decrease.

[0105] In contrast to this, in the second embodiment, as shown in FIG. 9B, a step portion 46 that abuts against the substrate 5 is formed in the molded resin portion 4, and the heat that has traveled within the substrate 5 (indicated by arrow B) travels directly to the step portion 46, and then, as indicated by arrow F, moves toward the outer periphery of the molded resin portion 4, and is dissipated to the outside of the motor.

[0106] Therefore, in the molded resin portion 4, the heat dissipation path from the substrate 5 (indicated by arrow F) and the heat dissipation path from the coil 32 can be separated from each other, thereby improving the heat dissipation efficiency.

[0107] Except for the above points, the electric motor 1D of the fourth embodiment is configured similarly to the electric motor 1 of the first embodiment.

[0108] Furthermore, the semiconductor elements 50 (i.e., MOSFET 51 and microcomputer 52) on the substrate 5 of the electric motor 1D may be arranged as in the second embodiment (FIG. 4), or as in the third embodiment (FIG. 6) or its modified example (FIG. 7).

[0109] As described above, in the electric motor 1D of the fourth embodiment, the step portion 46 that contacts the substrate 5 is formed integrally with the molded resin portion 4. Therefore, the heat dissipation path from the substrate 5 via the step portion 46 and the heat dissipation path from the coil 32 can be separated from each other, thereby further improving the heat dissipation efficiency.

[0110] <Air Conditioning Apparatus> Next, an air conditioning apparatus to which the electric motor 1 of each of the above-described embodiments and modifications can be applied will be described. Fig. 10(A) is a diagram showing the configuration of an air conditioning apparatus 100 to which the electric motor 1 of embodiment 1 is applied. The air conditioning apparatus 100 includes an outdoor unit 101 and an indoor unit 102. The outdoor unit 101 and the indoor unit 102 are connected by a refrigerant pipe 103.

[0111] The outdoor unit 101 includes a compressor 104, a condenser 105, and an outdoor blower 110. The outdoor blower 110 is, for example, a propeller fan. The outdoor blower 110 has an impeller 111 and an electric motor 1A that drives the impeller 111.

[0112] The indoor unit 102 includes an evaporator 122 and an indoor blower 120. The indoor blower 120 is, for example, a crossflow fan. The indoor blower 120 has an impeller 121 and an electric motor 1B that drives the impeller 121.

[0113] 10(B) is a cross-sectional view of the outdoor unit 101. The electric motor 1A is supported by a frame 107 disposed within a housing 106 of the outdoor unit 101. An impeller 111 is attached to the shaft 10 of the electric motor 1A via a hub 112.

[0114] In the outdoor blower 110, an impeller 111 is rotated by the motor 1A to blow air outdoors. During cooling operation of the air conditioner 100, the heat released when the refrigerant compressed by the compressor 104 is condensed in the condenser 105 is released outdoors by the air blown by the outdoor blower 110.

[0115] In the indoor fan 120 (FIG. 10A), an impeller 121 is rotated by the motor 1B to blow air into the room. During cooling operation of the air conditioner 100, the air that has lost heat when the refrigerant evaporates in the evaporator 122 is blown into the room by the indoor fan 120.

[0116] The electric motors 1A and 1B are configured as the electric motor 1 of embodiment 1. In the electric motor 1 of embodiment 1, a stable operating state is maintained due to the improved heat dissipation of the substrate 5. This improves the reliability of the outdoor fan 110 and the indoor fan 120, thereby improving the reliability of the air conditioning apparatus 100.

[0117] The electric motors 1A and 1B are not limited to the electric motor 1 of embodiment 1, but may be the electric motors of embodiments 2 to 4 or the modified examples. Furthermore, although the electric motors of each embodiment and the modified examples are used in both the outdoor fan 110 and the indoor fan 120 here, they may be used in only one of them.

[0118] Although the preferred embodiments have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various improvements and modifications can be made.

[0119] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D Electric motor, 2 Rotor, 3 Stator, 4 Molded resin part, 5, 5A, 5B, 5C, 5D Board, 7 Bracket, 10 Shaft, 20 Rotor core, 21 Magnet insertion hole, 22 Permanent magnet, 30 Stator core, 31 Insulator, 32 Coil, 32a Inner peripheral surface, 41 Cylindrical part (stator holding part), 41a Board facing part, 45 Inner peripheral surface, 46 Step part (board support part), 50 Semiconductor element, 51 MOSFET, 52 Microcomputer, 55 Mounting hole, 61 Support pin, 100 Air conditioner, 101 Outdoor unit, 102 Indoor unit, 110 Outdoor blower, 111 Impeller, 120 Indoor blower, 121 impeller, Ei inner peripheral end of semiconductor element, Eo outer peripheral end of semiconductor element.

Claims

1. An electric motor comprising: a rotor having a shaft; a stator having a ring-shaped stator core surrounding the rotor from the outside in the radial direction centered on a central axis of the shaft; and a coil wound around the stator core; a molded resin portion provided to cover the stator; and a substrate arranged on one side of the stator core in the axial direction of the shaft, wherein a semiconductor element is arranged on the substrate, and a distance Ri from the central axis to an inner end of the semiconductor element in the radial direction, a distance Ro from the central axis to an outer end of the semiconductor element in the radial direction, a distance Rm from the central axis to an inner surface of the molded resin portion, and a distance Rc from the central axis to an inner end of the coil in the radial direction satisfy at least one of Ro≧Rm, Ro≦Rc, Ri≧Rm, and Ri≦Rc.

2. The electric motor according to claim 1, wherein the semiconductor element is disposed on a surface of the substrate facing the stator.

3. The electric motor according to claim 1 or 2, wherein the molded resin portion has a board-facing portion that faces the board, and the board-facing portion faces the semiconductor element in the axial direction across air.

4. The electric motor according to any one of claims 1 to 3, wherein a support pin for supporting the substrate is attached to the molded resin portion.

5. The electric motor according to any one of claims 1 to 3, wherein the molded resin portion has a step portion for supporting the substrate.

6. The electric motor according to any one of claims 1 to 5, further comprising a bracket on the opposite side of the molded resin portion with respect to the circuit board in the axial direction, the circuit board being housed in a space formed between the molded resin portion and the bracket.

7. An electric motor as claimed in any one of claims 1 to 6, wherein n (n is an integer of 2 or more) semiconductor elements are arranged on the substrate, and the n semiconductor elements are arranged one per n regions divided in a circumferential direction around the central axis.

8. The electric motor according to claim 7, wherein the n regions are provided at equal intervals in the circumferential direction.

9. An electric motor as described in any one of claims 1 to 6, wherein the substrate has m (m is an integer of 2 or more) first semiconductor elements and r (r is an integer of 1 or more) second semiconductor elements, the amount of heat generated by each of the m first semiconductor elements is greater than the amount of heat generated by each of the r second semiconductor elements, and the m first semiconductor elements are arranged one by one in m regions divided circumferentially around the central axis.

10. The electric motor according to claim 9, wherein the m regions are provided at equal intervals in the circumferential direction.

11. The electric motor according to claim 9 or 10, wherein the r second semiconductor elements are arranged so as to straddle two of the m regions.

12. The electric motor according to any one of claims 9 to 11, wherein the first semiconductor element is a MOSFET, and the second semiconductor element is a microcomputer.

13. An electric motor comprising: a rotor having a shaft; a stator having a ring-shaped stator core surrounding the rotor from the outside in the radial direction centered on the central axis of the shaft, and a coil wound around the stator core; a molded resin portion provided to cover the stator; and a substrate arranged on one side of the stator core in the axial direction of the shaft, wherein n (n is an integer of 2 or more) semiconductor elements are arranged on the substrate, and the n semiconductor elements are arranged one per n regions divided circumferentially around the central axis.

14. The electric motor according to claim 13, wherein the n regions are provided at equal intervals in the circumferential direction.

15. An electric motor comprising: a rotor having a shaft; a stator having a ring-shaped stator core surrounding the rotor from the outside in the radial direction centered on a central axis of the shaft, and a coil wound around the stator core; a molded resin portion provided to cover the stator; and a substrate arranged on one side of the stator core in the axial direction of the shaft, wherein m (m is an integer of 2 or more) first semiconductor elements and r (r is an integer of 1 or more) second semiconductor elements are arranged on the substrate, the amount of heat generated by each of the m first semiconductor elements is greater than the amount of heat generated by each of the r second semiconductor elements, and the m first semiconductor elements are arranged one per m regions divided in the circumferential direction centered on the central axis.

16. The electric motor according to claim 15, wherein the m regions are provided at equal intervals in the circumferential direction.

17. A blower comprising an electric motor according to any one of claims 1 to 16 and an impeller attached to the shaft of the electric motor.

18. An air-conditioning apparatus comprising an outdoor unit and an indoor unit, at least one of the outdoor unit and the indoor unit having a blower according to claim 17.

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