Motor for motor compressor and motor compressor with the same

Abstract

To provide a motor for a motor compressor which can effectively reduce cogging torque and a torque ripple while maintaining average torque.SOLUTION: A rotor 24 comprises a plurality of magnet insertion holes 31 formed in a circumferential direction at an outer peripheral part facing tip end surfaces of teeth 27, permanent magnets 32 are embedded in the respective magnet insertion holes 31, and arranged via gaps 28 between an outer peripheral surface and the tip end surfaces of the teeth 27. The rotor 24 comprises: gap parts 44 formed at the outer peripheral part in a rotation direction of the rotor 24 when viewed from a d-axis constituting one magnetic pole; and recesses 34 formed on the outer peripheral surface in a direction opposite to the rotation direction of the rotor 24 when viewed from the d-axis.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electric compressor motor that is housed in a container, for example, and drives a compression element, and to an electric compressor including the same. [Background technology]

[0002] Conventionally, electric compressors used in refrigeration cycles employ permanent magnet synchronous motors with permanent magnets embedded in the rotor, but this type of permanent magnet synchronous motor has a problem in that the generated vibration noise increases when the cogging torque or torque ripple increases.

[0003] Generally, there is a correlation between the average torque and cogging torque output by a motor, and between the average torque and torque ripple, and increasing one also increases the other. For this reason, many methods have been proposed to reduce the cogging torque and torque ripple while maintaining the average torque (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6507956 Summary of the Invention [Problem to be solved by the invention]

[0005] Fig. 15 shows a conventional permanent magnet synchronous motor 100 having a structure for reducing cogging torque and torque ripple as described above. Fig. 15 shows a cross section perpendicular to the axial direction of motor 100. In the figure, reference numeral 101 denotes a stator and 102 denotes a rotor. Stator 101 has an annular base 103, a plurality of teeth 104 protruding radially inward from base 103, and windings (not shown) wound around teeth 104.

[0006] The rotor 102 is disposed so as to have a gap 106 between itself and the tip surfaces of the teeth 104 of the stator 101. The rotor 102 is composed of a rotor core 107, a plurality of magnet insertion holes 108 formed in the circumferential direction on the outer periphery of the rotor core 107, and permanent magnets 109 embedded in each magnet insertion hole 108.

[0007] In the case of conventional motor 100 shown in Fig. 15, for example, enlarged gap portion 111 is formed on the outer circumferential surface at a position corresponding to the space between adjacent magnet insertion holes 108. The circle indicated by X in Fig. 15 indicates the case where the outer circumferential surface of rotor 102 is a perfect circle, and enlarged gap portion 111 is formed by recessing the outer circumferential surface at that location from circle X.

[0008] By providing such an expanded gap portion 111, the magnetic force in that portion is weakened, and the force tending to advance the rotor 102 in the direction of rotation and the force tending to return are weakened, so that the cogging torque and torque ripple can be reduced; however, the effect is limited.

[0009] The present invention has been made to solve the above-mentioned conventional technical problems, and has an object to provide a motor for an electric compressor that can effectively reduce cogging torque and torque ripple while maintaining average torque, and an electric compressor including the motor. [Means for solving the problem]

[0010] The motor for an electric compressor of the present invention comprises a stator having a plurality of teeth protruding radially inward from an annular base, and a rotor having a plurality of magnetic poles formed of permanent magnets, the rotor having a plurality of magnet insertion holes formed circumferentially on its outer periphery facing the tip faces of the teeth, the permanent magnets being embedded in each of the magnet insertion holes and arranged with a gap between the outer periphery and the tip faces of the teeth, and characterized in that the rotor has a gap formed on the outer periphery in the rotational direction of the rotor as viewed from the d axis that constitutes one magnetic pole, and a recess formed on the outer periphery in the direction opposite to the rotational direction of the rotor as viewed from the d axis.

[0011] The motor for an electric compressor of the invention of claim 2 is characterized in that in the above invention, the gap portion is formed continuously from the magnet insertion hole in the direction of the outer peripheral surface of the rotor, and its tip is arc-shaped, and the recess is composed of a convex arc-shaped portion continuing from the outer peripheral surface of the rotor and a concave arc-shaped portion continuing from the convex arc-shaped portion, and a straight line portion parallel to the magnet insertion hole is formed continuously in the concave arc-shaped portion.

[0012] The motor for electric compressors of the invention of claim 3 is characterized in that, when the distance between the center of the arc at the end of the gap and the magnet insertion hole is L, the distance from the outer peripheral surface of the rotor on the d-axis to the magnet insertion hole is Lm, and the point where a perpendicular line drawn from the center of the arc at the end of the gap to the magnet insertion hole intersects with the magnet insertion hole is A, L / Lm is set to 0.25≦L / Lm≦0.4, and the angle θ1 formed by a line from the center of the outer diameter of the rotor passing through point A and the d-axis is set to 20°≦θ1≦25° in electrical angle.

[0013] The motor for an electric compressor of the invention of claim 4 is characterized in that, when the point at which the convex arc-shaped portion and the concave arc-shaped portion that constitute the recess in the above invention are connected is defined as B, the angle θ2 formed by the line passing from the center of the outer diameter of the rotor through point B and the d-axis is set to be 33°≦θ1≦48° in electrical angle.

[0014] The electric compressor of the invention recited in claim 5 comprises an electric compressor motor of any of the above inventions and a compression element driven by the electric compressor motor housed in a container. Effect of the Invention

[0015] According to the present invention, in a motor for an electric compressor consisting of a stator having a plurality of teeth protruding radially inward from an annular base, and a rotor having a plurality of magnetic poles formed of permanent magnets, the rotor has a plurality of magnet insertion holes formed in the circumferential direction on its outer periphery facing the tip faces of the teeth, and the permanent magnets are each embedded in the magnet insertion holes and arranged with a gap between the outer periphery and the tip faces of the teeth, and a gap is formed on the outer periphery in the rotational direction of the rotor as viewed from the d axis that constitutes one magnetic pole, and a recess is formed on the outer periphery in the direction opposite to the rotational direction of the rotor as viewed from the d axis.Therefore, the gap formed on the outer periphery in the rotational direction of the rotor as viewed from the d axis weakens the magnetic force of that portion, thereby weakening the force that moves in the rotational direction when the rotor is rotated, while the recess formed on the outer periphery in the direction opposite to the rotational direction of the rotor as viewed from the d axis weakens the magnetic force of that portion, thereby weakening the force that moves the rotor back in the direction opposite to the rotational direction.

[0016] As a result, it is possible to effectively reduce the cogging torque and torque ripple compared to the conventional art while maintaining the average torque, and it is possible to effectively suppress the noise and vibration generated by the motor.

[0017] More specifically, as in the invention of claim 2, the gap portion is formed continuously from the magnet insertion hole in the direction of the outer peripheral surface of the rotor, and its tip is made into an arc shape, and the recess is composed of a convex arc-shaped portion that continues from the outer peripheral surface of the rotor and a concave arc-shaped portion that continues from the convex arc-shaped portion, and a straight line portion that is parallel to the magnet insertion hole is formed continuously in the concave arc-shaped portion.

[0018] As in the invention of claim 3, if the distance between the center of the arc at the end of the gap and the magnet insertion hole is L, the distance from the outer peripheral surface of the rotor on the d-axis to the magnet insertion hole is Lm, and the point where a perpendicular line drawn from the center of the arc at the end of the gap to the magnet insertion hole intersects with the magnet insertion hole is A, then L / Lm is set to 0.25≦L / Lm≦0.4, and the angle θ1 formed by the line from the center of the rotor's outer diameter passing through point A and the d-axis is set to 20°≦θ1≦25° electrical angle.

[0019] Furthermore, as in the invention of claim 4, when the point at which the convex arc-shaped portion and the concave arc-shaped portion that constitute the recess are connected is designated as B, the angle θ2 formed by the line passing from the center of the outer diameter of the rotor through point B and the d-axis is set to be 33°≦θ1≦48° in electrical angle.

[0020] By setting as above, it is possible to effectively reduce the cogging torque and the torque ripple while maintaining the average torque of the motor for the electric compressor.

[0021] Furthermore, as in the invention of claim 5, by constructing an electric compressor by housing the motor for an electric compressor and the compression element of each of the above inventions in a container, it is possible to obtain a small-sized, high-performance electric compressor with little vibration and noise. [Brief description of the drawings]

[0022] [Figure 1] 1 is a vertical sectional side view of an electric compressor according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an enlarged plan sectional view (a cross section perpendicular to the axial direction of the motor; the same applies below) of a main part of the motor (motor for an electric compressor) of FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional plan view for explaining the rotation direction and d-axis of the motor in FIG. 2. [Figure 4] FIG. 4 is an enlarged cross-sectional plan view for explaining the positions at which gaps and recesses are set in the motor shown in FIG. 3. [Diagram 5] 2 is a diagram for explaining the average torque of the motor of FIG. 1 when θ1 and L / Lm (both of which are parameters to be described later) are changed. FIG. [Figure 6] 2 is a diagram for explaining the cogging torque of the motor of FIG. 1 when θ1 and L / Lm are changed. [Figure 7] 2 is a diagram illustrating the torque ripple of the motor of FIG. 1 when θ1 and L / Lm are changed. [Figure 8] 2 is a diagram illustrating the average torque, cogging torque, and torque ripple of the motor of FIG. 1 when θ2 (a parameter to be described later) is changed. FIG. [Figure 9] FIG. 11 is an enlarged cross-sectional plan view of a motor in which only a gap is formed in a rotor. [Figure 10] FIG. 11 is an enlarged plan sectional view of a motor in which only recesses are formed in a rotor. [Figure 11] 16 is a diagram for explaining the average torque of the motor when the rotor has a perfect circular shape, the conventional shape of FIG. 15, the shape of FIG. 9, the shape of FIG. 10, and the shape of FIG. 2. FIG. [Figure 12] 16 is a diagram for explaining the cogging torque of a motor when the rotor has a perfect circular shape, the conventional shape of FIG. 15, the shape of FIG. 9, the shape of FIG. 10, and the shape of FIG. [Figure 13] 16 is a diagram illustrating the torque ripple of a motor when the rotor has a perfect circular shape, the conventional shape of FIG. 15, the shape of FIG. 9, the shape of FIG. 10, and the shape of FIG. 2. FIG. [Figure 14] 16 is a diagram showing the average torque, cogging torque, and torque ripple of a motor when the rotor has a perfect circular shape, when it has the conventional shape of FIG. 15, and when it has the shape of the present invention of FIG. 2. [Figure 15] FIG. 11 is an enlarged cross-sectional plan view of a conventional motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described in detail. An electric compressor 1 of the embodiment is a scroll compressor that houses a scroll compression element 3 and a motor (motor for electric compressor) 4 of the present invention in a container 2. The scroll compression element 3 comprises a fixed scroll 6 fixed to the container 2, and a movable scroll 7 that revolves around the fixed scroll 6 without rotating due to a rotating shaft 8 of the motor 4, and is arranged so that a spiral wrap 11 formed on the fixed scroll 6 and a spiral wrap 12 formed on the movable scroll 7 mesh with each other.

[0024] The refrigerant is introduced into the container 2 through a refrigerant introduction passage (not shown) and is sucked from the outside into the compression chamber defined between the wraps 11, 12. This compression chamber narrows toward the center due to the orbital motion of the movable scroll 7, so the sucked refrigerant is compressed and discharged from the center through the discharge chamber 14 and a refrigerant discharge passage (not shown). In addition, because the pressure inside the container 2 is low, the refrigerant also passes around the motor 4, cooling the motor 4.

[0025] Next, the motor 4 of the present invention will be described. The motor 4 of the embodiment is a permanent magnet synchronous motor, and is composed of a stator 21 consisting of a stator core 22 (made of multiple laminated electromagnetic steel sheets) and windings 23, and a magnet-embedded rotor 24 (also made of multiple laminated electromagnetic steel sheets) that is fixed to the rotating shaft 8 and rotates inside the stator 21.

[0026] As shown in FIG. 2, the stator core 22 of the stator 21 consists of an annular base 26 and a plurality of teeth 27 (the number of which corresponds to the number of poles; in this embodiment, 12 teeth) protruding radially inward from the base 26, and a winding 23 (not shown in FIG. 2) is wound around each tooth 27 in concentrated winding.

[0027] The rotor 24 is concentric with the stator 21, and is disposed so as to have a gap (air gap) 28 between its outer circumferential surface (the outer circumferential surface of a rotor core 29 described later) and the tip surfaces of the teeth 27. The rotor 24 has a rotor core 29, and a plurality of magnet insertion holes 31 (eight in this embodiment) are formed at equal intervals in the circumferential direction on the outer periphery of the rotor core 29 (rotor 24) facing the tip surfaces of the teeth 27. A permanent magnet 32 ​​is embedded in each magnet insertion hole 31, and each permanent magnet 32 ​​forms one magnetic pole on the rotor 24.

[0028] Therefore, the motor 4 of the embodiment has an eight-pole structure, the direction of the magnetic flux created by one permanent magnet 32 ​​constituting one magnetic pole is the d-axis (the central axis of the direction of the magnetic flux created by the magnetic pole), and the direction electrically and magnetically perpendicular to this d-axis is the q-axis. Note that the number of magnetic poles is not limited to eight as in the embodiment.

[0029] In addition, in the present invention, as shown in Figure 3, a gap portion 33 is formed on the outer periphery in the rotational direction of rotor 24 (indicated by an arrow in Figure 3) as viewed from the d axis (the central axis of permanent magnet 32) that constitutes one magnetic pole, and a recess 34 is formed on the outer periphery in the direction opposite to the rotational direction of rotor 24 as viewed from the d axis.

[0030] 3, in this embodiment, gap 33 is formed to continuously protrude from magnet insertion hole 31 in the direction of the outer circumferential surface of rotor 24, and has an elongated hole shape overall, with its tip being an arc-shaped portion 36. In addition, recess 34 is composed of convex arc-shaped portion 37 continuing from the outer circumferential surface of rotor 24 and concave arc-shaped portion 38 continuing therefrom, and concave arc-shaped portion 38 is formed with a straight line portion 39 that is parallel to magnet insertion hole 31.

[0031] In this way, the gap 36 formed on the outer periphery in the rotation direction of the rotor 24 as viewed from the d axis weakens the magnetic force generated in the gap 36 when the rotor 24 is rotated, thereby weakening the forward force. Furthermore, the recess 34 formed on the outer periphery in the opposite direction to the rotation direction of the rotor 24 as viewed from the d axis weakens the magnetic force in that portion, thereby weakening the force that causes the rotor 24 to return in the opposite direction to the rotation direction, thereby making it possible to reduce cogging torque and torque ripple.

[0032] The roles of the gap 36 and the recess 34 are as follows: (a) Role of the gap 36 By weakening the magnetic force in the rotational direction of the rotor 24, the torque peaks are smoothed out, reducing the cogging torque and torque ripple. (b) Role of the recess 34 By weakening the magnetic force in the direction opposite to the rotation direction of the rotor 24, the torque valley is raised, reducing the cogging torque and torque ripple. It also prevents a decrease in the average torque.

[0033] 4 to 8, the optimum position for maximizing the effect of the above-mentioned gap 36 and recess 34 will be examined. As shown in Fig. 4, the distance between the center of the arc of arc-shaped portion 36 at the tip of gap 33 and magnet insertion hole 31 is defined as L. Also, the distance from the outer circumferential surface of rotor 24 on the d-axis to magnet insertion hole 31 is defined as Lm.

[0034] Furthermore, the point where a perpendicular line drawn from the center of arc-shaped portion 36 at the tip of gap 33 toward magnet insertion hole 31 intersects with magnet insertion hole 31 is defined as A, and the angle formed by a line passing from the center of the outer diameter of rotor 24 through point A and the d axis is defined as θ1. Furthermore, the point where convex arc-shaped portion 37 and concave arc-shaped portion 38 that constitute recess 34 connect is defined as B, and the angle formed by a line passing from the center of the outer diameter of rotor 24 through point B and the d axis is defined as θ2.

[0035] First, the position and shape of the gap 33 will be examined. When each parameter is defined as above, the ratio L / Lm of L to the distance Lm, and the angle θ1 are changed. The results of analyzing the average torque characteristics at the maximum current of the motor 4 are shown in Fig. 5, the results of analyzing the cogging torque characteristics are shown in Fig. 6, and the results of analyzing the torque ripple characteristics are shown in Fig. 7. Note that the angle θ1 is converted to an electrical angle. The angle θ2 is also converted to an electrical angle and fixed at 46°. Furthermore, the numerical values ​​P1 to P7 in each figure are ratios (per unit) when the value when the rotor has an outer diameter of a perfect circle is used as the reference (1.000).

[0036] As is clear from the dashed line range in FIG. 5, the average torque at maximum current is equivalent to that in the case of a perfect circle when the angle θ1 is 20°≦θ1≦25°, but decreases in other ranges.

[0037] As is clear from the dashed line range in FIG. 6, when the ratio L / Lm is in the range of 0.25≦L / Lm≦0.4, which is approximately when the average torque is equivalent to that in the case of a perfect circle, and the range is 20°≦θ1≦25°, the cogging torque is smallest.

[0038] As is clear from FIG. 7, the torque ripple at maximum current is sufficiently small within the range of 0.25≦L / Lm≦0.4 when 20°≦θ1≦25°, where the average torque is the same as in the case of a perfect circle.

[0039] That is, by setting the position and shape of the gap 33 so that the ratio L / Lm is 0.25≦L / Lm≦0.4 and the angle θ1 is in the range of 20°≦θ1≦25° in electrical angle, it is possible to most effectively reduce the cogging torque and torque ripple while maintaining the average torque. Therefore, in this embodiment, the position and shape of the gap 33 are determined so that the ratio L / Lm is 0.3 and the angle θ1 is 24° (electrical angle).

[0040] After determining the position and shape of the gap 33 in this way, the optimal position and shape of the recess 34 are then verified. Figure 8 shows the results of analyzing the average torque characteristics at maximum current of the motor 4, the cogging torque characteristics, and the torque ripple characteristics when the angle θ2 is changed. Note that, as mentioned above, the ratio L / Lm is fixed at 0.3 and the angle θ1 is fixed at 24°.

[0041] As is clear from Figure 8, the average torque at the maximum current value is slightly lower than that in the case of a perfect circle when the angle θ2 is θ2≦33°, but is equivalent when 33°≦θ2. The values ​​in Figure 8 are also expressed as a ratio (per unit) with the value for a rotor with a perfect circle outer diameter set as the reference (1.00).

[0042] The cogging torque monotonically decreases when the angle θ2 is 31°≦31°, reaches a maximum value at 36° within the range of 31°≦θ2≦44°, and then starts to increase monotonically when 44°≦θ2. Then, when θ2=49°, it reaches a value equivalent to the maximum value.

[0043] The torque ripple at maximum current decreases monotonically when the angle θ2 is θ2≦31°, and after reaching a substantially constant value in the range of 31°≦θ2≦48°, it begins to increase monotonically when the angle θ2 is 48°≦θ2.

[0044] From the above situation, it can be seen that by setting the position and shape of the recess 34 so that the angle θ2 is 33°≦θ2≦48° electrical angle (shown by the dashed line in FIG. 8), it is possible to obtain a significant effect in reducing the cogging torque and the torque ripple at the maximum current while maintaining the average torque at the maximum current.

[0045] Next, with reference to Figs. 9 to 13, the characteristics of maximum torque, cogging torque and torque ripple will be described for the case where the rotor 24 is a perfect circle, the conventional shape of Fig. 15, the case where only the gap 33 is formed as in Fig. 9 (with only the gap), the case where only the recess 34 is formed on the outer diameter of the rotor 24 as in Fig. 10 (with only the outer diameter recess), and the case where the gap 33 and the recess 34 are formed on the outer diameter of the rotor 24 as in Fig. 2 (the present invention) (with the gap and the outer diameter recess). Note that each parameter (L / Lm, θ1, θ2) in the case of Fig. 2 is set within the optimum value range mentioned above. The numerical values ​​in each figure are also ratios (per unit) with the value for a rotor with a perfect circle outer diameter as the reference (1.00).

[0046] As shown in Fig. 11, when the average torque at maximum current in each case is 1.00, as is clear from Fig. 12, the cogging torque is reduced by 0.70 when only recessed portion 34 is provided, and as is clear from Fig. 13, the torque ripple is reduced by 0.77 when only gap 33 is provided. And when gap 33 and recessed portion 34 are provided as in the present invention, the cogging torque is 0.61 and the torque ripple is 0.68, which is the greatest reduction effect. This state is summarized in Fig. 14 for the perfect circle shape, the conventional shape (Fig. 15), and the inventive shape (Fig. 2).

[0047] As described above in detail, according to the present invention, gap 33 is formed on the outer periphery in the direction of rotation of rotor 24 as viewed from the d axis that constitutes one magnetic pole, and recess 34 is formed on the outer periphery in the direction opposite to the direction of rotation of rotor 24 as viewed from the d axis. Therefore, gap 33 weakens the magnetic force of gap 33 when rotor 24 is rotated, thereby weakening the force tending to move in the direction of rotation, and recess 34 weakens the magnetic force in that portion, thereby weakening the force tending to return rotor 24 in the direction opposite to the direction of rotation.

[0048] As a result, it is possible to effectively reduce the cogging torque and torque ripple compared to the conventional art while maintaining the average torque, and it is possible to effectively suppress the noise and vibration generated by the motor 4.

[0049] In addition, in the embodiment, the gap portion 33 is formed continuously from the magnet insertion hole 31 in the direction of the outer peripheral surface of the rotor 24, and its tip is formed in an arc shape, and the recess 34 is composed of a convex arc-shaped portion 37 that continues from the outer peripheral surface of the rotor 24 and a concave arc-shaped portion 38 that continues from the convex arc-shaped portion 37, and a straight line portion 39 that is parallel to the magnet insertion hole 31 is formed continuously in the concave arc-shaped portion 38.

[0050] Then, assuming that the distance between the center of the arc-shaped portion 36 at the tip of the gap 33 and the magnet insertion hole 31 is L, the distance from the outer peripheral surface of the rotor 24 on the d-axis to the magnet insertion hole 31 is Lm, and the point where a perpendicular line drawn from the center of the arc-shaped portion 36 at the tip of the gap 33 toward the magnet insertion hole 31 intersects with the magnet insertion hole 31 is A, L / Lm is set to 0.25≦L / Lm≦0.4, and the angle θ1 formed by a line passing from the center of the rotor's outer diameter through point A and the d-axis is set to 20°≦θ1≦25° in electrical angle.

[0051] Furthermore, when the point where the convex arc-shaped portion 37 and the concave arc-shaped portion 38 that constitute the recess 34 are connected is designated as point B, the angle θ2 formed by the line passing from the center of the outer diameter of the rotor 24 through point B and the d-axis is set to 33°≦θ1≦48° in electrical angle. This makes it possible to effectively reduce the cogging torque and torque ripple while maintaining the average torque of the motor 4.

[0052] Furthermore, by configuring the electric compressor 1 by housing the motor 4 and the scroll compression element 33 within the container 2, it is possible to provide a small-sized, high-performance electric compressor 1 with little vibration and noise.

[0053] In the embodiment, the present invention is applied to a scroll electric compressor, but the present invention is not limited to this and the motor 4 of the present invention is suitable for various electric compressors such as a rotary electric compressor. [Explanation of symbols]

[0054] 1 Electric compressor 2 containers 3 Scroll Compression Factor 4 Motor 8 Rotation Axis 21 Stator 22 Stator core 23 Windings 24 Rotor 27 Teeth 28 Gap 29 Rotor core 31 Magnet insertion hole 32 Permanent magnets 33 Cavity 34 Recess 36 Arc-shaped section 37 Convex arc-shaped part 38 Concave arc shaped portion 39 Straight section

Claims

1. A motor for an electric compressor includes a stator having a plurality of teeth protruding radially inward from an annular base, and a rotor having a plurality of magnetic poles formed of permanent magnets, The rotor is a plurality of magnet insertion holes formed in a circumferential direction in an outer periphery facing the tip surfaces of the teeth, the permanent magnets being embedded in the magnet insertion holes and disposed with gaps between the outer periphery and the tip surfaces of the teeth; A motor for an electric compressor, characterized in that it has a gap formed on an outer periphery in the rotational direction of the rotor as viewed from a d-axis that constitutes one magnetic pole, and a recess formed on the outer periphery in the direction opposite to the rotational direction of the rotor as viewed from the d-axis.

2. The gap is formed continuously from the magnet insertion hole toward the outer circumferential surface of the rotor, and the tip of the gap is formed in an arc shape.

2. The motor for an electric compressor according to claim 1, wherein the recess is composed of a convex arc-shaped portion continuing from the outer peripheral surface of the rotor and a concave arc-shaped portion continuing from the convex arc-shaped portion, and a straight portion parallel to the magnet insertion hole is formed continuously with the concave arc-shaped portion.

3. The distance between the center of the arc at the tip of the gap and the magnet insertion hole is L, The distance from the outer circumferential surface of the rotor to the magnet insertion hole on the d-axis is Lm, When the point A is the intersection point between the magnet insertion hole and a perpendicular line drawn from the center of the arc at the tip of the gap toward the magnet insertion hole, L / Lm is 0.25≦L / Lm≦0.4, The angle θ1 between the line passing through the point A from the center of the outer diameter of the rotor and the d-axis is 20°≦θ1≦25° in electrical angle.

3. The motor for an electric compressor according to claim 2, wherein:

4. When the point where the convex arc-shaped portion and the concave arc-shaped portion that constitute the recess are connected is designated as B, The angle θ2 between the line passing through the center of the outer diameter of the rotor and the point B and the d-axis is 33°≦θ1≦48° in electrical angle.

4. The motor for an electric compressor according to claim 3, wherein:

5. 5. An electric compressor comprising: the motor for an electric compressor according to claim 1; and a compression element driven by the motor for an electric compressor, the compression element being housed in a container.

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