Stator core of rotating electrical machine

Abstract

To relatively simplify a configuration while reducing torque ripple.SOLUTION: A stator core for rotary electric machine is configured by stacking electromagnetic steel sheets in an axial direction, includes a plurality of teeth extending in an inner peripheral direction in an inner peripheral portion of an annular yoke part and includes protrusions extending toward both sides in a circumferential direction in tip ends of the teeth. The electromagnetic steel sheets include: a first electromagnetic steel sheet in a form in which one side of the protrusions of the teeth turned ahead in a clockwise direction is cut; and a second electromagnetic steel sheet in a form in which one side of the protrusions of the teeth turned ahead in a clockwise direction is cut. The same number of the first electromagnetic steel sheets and the second electromagnetic sheets are stacked.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a stator core for a rotating electric machine that is configured by laminating electromagnetic steel sheets. [Background technology]

[0002] For example, in rotating electrical machines such as three-phase induction motors and synchronous motors, the stator is configured to include a stator core having a ring-shaped yoke and a plurality of teeth protruding inward from the yoke, and a coil housed in slots between the teeth (see, for example, Patent Document 1). In this type of motor, for example a 4-pole, 6-slot motor, it is known that torque ripple occurs at six times the power supply frequency and integer multiples of that frequency, and it is desirable to reduce such torque ripple. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-188675 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned Patent Document 1 discloses a configuration in which the inner periphery of multiple teeth of a stator core is connected with a metal connecting member in order to reduce torque ripple in a brushless motor. This configuration maintains the circumferential pitch of the tips of the teeth with high precision, thereby suppressing cogging caused by variations and reducing torque ripple. However, this configuration increases the number of parts and complicates the configuration.

[0005] Therefore, it is an object of the present invention to provide a stator core for a rotating electrical machine that can reduce torque ripple while having a relatively simple configuration. [Means for solving the problem]

[0006] The stator core of the rotating electric machine of the embodiment is constructed by stacking electromagnetic steel sheets in the axial direction, and has a plurality of teeth extending in the inner circumferential direction on the inner periphery of a circular yoke portion, and has protrusions extending on both sides in the circumferential direction at the tips of the teeth, wherein the electromagnetic steel sheets include a first electromagnetic steel sheet in which one side of the protrusions of the teeth facing forward in the clockwise direction is cut, and a second electromagnetic steel sheet in which one side of the protrusions of the teeth facing forward in the counterclockwise direction is cut, and the first electromagnetic steel sheets and the second electromagnetic steel sheets are stacked in equal numbers. The position at which the protruding portion of the electromagnetic steel plate is cut is set to start from a position at the tip of the tooth portion that is shifted in the opposite direction from the cutting side with respect to the center line of the tooth portion. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing a schematic overall configuration of a motor according to a first embodiment. [Figure 2] FIG. 1 is a plan view showing the shape of a first electromagnetic steel sheet; [Figure 3] FIG. 10 is a plan view showing the shape of a second electromagnetic steel sheet; [Figure 4] An enlarged plan view showing the cut shape of one tooth portion [Figure 5] Cross-sectional view showing the laminated state of electromagnetic steel sheets [Figure 6] FIG. 10 is a plan view showing the state of magnetic flux in the first electromagnetic steel sheet; [Figure 7] FIG. 10 is a plan view showing the state of magnetic flux in the second electromagnetic steel sheet; [Figure 8] FIG. 10 is a diagram showing torque fluctuations in a first electromagnetic steel sheet and a second electromagnetic steel sheet. [Figure 9] A diagram showing torque fluctuations compared with a conventional model. [Figure 10] FIG. 10 is a cross-sectional view illustrating a laminated state of electromagnetic steel sheets according to a second embodiment. [Figure 11] FIG. 10 is a cross-sectional view illustrating a stacked state of electromagnetic steel sheets according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A first embodiment will be described below with reference to FIGS. 1 to 9. FIG. 1 shows a schematic view of the internal configuration of a permanent magnet three-phase synchronous motor 1 (hereinafter simply referred to as motor 1) as a rotating electric machine according to this embodiment, covering half the circumference. The motor 1 according to this embodiment is configured by, for example, mounting a stator 3 on the inner peripheral surface of a cylindrical frame 2, and disposing a rotor 4 on the inner peripheral portion of the stator 3 with a small air gap. Note that this embodiment uses a 4-pole, 6-slot motor 1 as a specific example, but the present invention is not limited to this.

[0009] The rotor 4 has a cylindrical rotor core 5 as a whole, with a rotating shaft (not shown) fixed through a central hole 5a at the center of the rotor core 5, and the rotating shaft is rotatably supported by brackets on both ends of the frame 2. Slits 5b are formed in the regions that form each magnetic pole of the rotor core 5, i.e., in each of the 90-degree regions divided into four circumferentially, and a permanent magnet 6 is installed in each slit 5b. The rotor core 5 is made by stacking a number of electromagnetic steel plates in the axial direction.

[0010] The stator 3 is configured by mounting a three-phase winding 8 on a stator core 7 having a plurality of slots 7a, for example six. The stator core 7 is configured by stacking a number of electromagnetic steel sheets in the axial direction. The stator core 7 is configured in an overall annular shape, and includes a ring-shaped yoke portion 9 on the outer periphery, and a plurality of teeth 10 (six in this case) extending inward from the yoke portion 9. The teeth 10 are configured in a form having protrusions 11 at their inner periphery tips that extend on both sides in the circumferential direction.

[0011] The stator core 7 according to this embodiment will now be described in detail with reference to Figures 2 to 5. As described above, the stator core 7 is formed by laminating a large number of electromagnetic steel sheets, and is formed by including the same number of two types of electromagnetic steel sheets 12, 13: first electromagnetic steel sheets 12 as shown in Figure 2 and second electromagnetic steel sheets 13 as shown in Figure 3. These electromagnetic steel sheets 12, 13 integrally comprise a ring-shaped portion corresponding to the yoke portion 9 of the stator core 7 and portions corresponding to the six teeth portions 10, and also comprise portions corresponding to only one side of the protrusions 11 of each tooth portion 10.

[0012] Specifically, as shown in Figures 2 and 4, the first electromagnetic steel sheet 12 has one side of the protrusion 11 of each tooth portion 10 that faces forward in the clockwise direction of rotation cut out, and this cut portion is referred to as cut portion 12a. As shown in Figure 3, the second electromagnetic steel sheet 13 has one side of the protrusion 11 of each tooth portion 10 that faces forward in the counterclockwise direction of rotation cut out, and this cut portion is referred to as cut portion 13a. In this embodiment, the first electromagnetic steel sheet 12 and the second electromagnetic steel sheet 13 have mirror-symmetrical shapes and are obtained by flipping one type of electromagnetic steel sheet of the same shape over.

[0013] More specifically, in the case of the first electromagnetic steel sheet 12, the cut portions 12a, 13a provided on these electromagnetic steel sheets 12, 13 are cut from a starting point S at a position shifted in the opposite direction (left side in FIG. 4) from the cutting side (right side in FIG. 4) with respect to the center line O of the tooth portion 10 at the tip end of the portion corresponding to the tooth portion 10, as shown in FIG. 4. The cut is made by a straight line L extending from the starting point S toward the other circumferential direction (right side in FIG. 4) and making an angle φ of 25 degrees or more with respect to the tip end edge of the tooth portion 10.

[0014] More specifically, the starting point S is the position where the tip of the tooth 10 intersects with an imaginary line V that passes through the center of the rotor core 7 and is shifted in one circumferential direction by an angle θ with respect to the center line O of the tooth 10. The angle θ is θ=360 / (P*n) / 2 (1) (where P is the number of poles, and n is the reduced torque ripple multiple component for frequency f) In this embodiment, P is 4 and n is 6, so θ=7.5°.

[0015] In this embodiment, as shown in Fig. 5, the stator core 7 is formed by alternately stacking first blocks 14, each of which is formed by stacking a plurality of, for example, several, first electromagnetic steel sheets 12, and second blocks 15, each of which is formed by stacking the same number of second electromagnetic steel sheets 13. In Fig. 5, a total of six blocks are stacked alternately, with three first blocks 14 and three second blocks 15. The three-phase windings 8 are attached to the teeth portion 10 of the stator core 7 formed by stacking the electromagnetic steel sheets 12 and 13 as described above, so as to be housed in each slot 7a, thereby forming the stator 3.

[0016] Next, the operation and effects of the motor 1 configured as described above will be described with reference to Figures 6 to 9. In a motor 1 with, for example, four poles and six slots, such as the three-phase synchronous motor 1 of this embodiment, when three-phase AC is applied to the windings 8, the distribution of magnetic flux density, and therefore the rotational magnetomotive force on the rotor 4, fluctuates periodically, and it is known that torque ripple increases, particularly due to harmonic components six times the frequency f. In response to this, the present inventors focused on the shape of the teeth 10 of the stator core 7 in order to reduce torque ripple, and confirmed that torque ripple can be reduced by modifying the shape of the protrusions 11 provided at the inner ends of the teeth 10.

[0017] That is, in this embodiment, it has been confirmed that torque ripple can be reduced by providing first electromagnetic steel sheets 12 in which one side of protrusions 11 of teeth 10 facing forward in the clockwise direction is cut, and second electromagnetic steel sheets 13 in which one side of protrusions 11 of teeth 10 facing forward in the counterclockwise direction is cut, and combining and stacking these to form stator core 7. The reasons for this are thought to be as follows.

[0018] Here, Fig. 6 shows the state of magnetic flux passing through the first electromagnetic steel sheet 12 in a given phase, and Fig. 7 shows the state of magnetic flux passing through the second electromagnetic steel sheet 13 in the same phase. As can be seen from Figs. 6 and 7, the distribution of magnetic flux density between the first electromagnetic steel sheet 12 and the second electromagnetic steel sheet 13 is biased toward the side where the protrusion 11 is present. In the stator core 7 of the present embodiment, the electromagnetic steel sheets 12, 13 are configured by laminating the same number of sheets, which is thought to have made it possible to equalize the distribution of magnetic flux density overall and reduce the magnitude of torque ripple.

[0019] FIG. 8 shows the variation in generated torque over time, i.e., with phase fluctuation. In FIG. 8, (A) shows the torque at the first electromagnetic steel sheet 12, and (B) shows the torque at the second electromagnetic steel sheet 13. Also, (C) shows the torque for the entire motor 1 of this embodiment. In addition to the torque variation shown in FIG. 8, (D) shows the torque variation for a conventional motor, i.e., a stator core with protrusions on both sides. In FIGS. 8 and 9, (A) and (B) have opposite high and low waves, and (C), which is a combination of these, shows suppressed ripple. Furthermore, the torque ripple is generally lower than in (D). From FIGS. 8 and 9, it can be seen that the torque ripple was sufficiently reduced in the stator core 7 of this embodiment.

[0020] In this embodiment, it is possible to assemble the stator core 7 without adding any additional parts. As described above, the stator core 7 of the motor 1 of this embodiment includes first electromagnetic steel sheets 12 in which one side of the protruding portions 11 of the teeth 10 facing the clockwise direction of rotation is cut, and second electromagnetic steel sheets 13 in which one side of the protruding portions 11 of the teeth 10 facing the counterclockwise direction of rotation is cut, and these sheets are combined and stacked in equal numbers, thereby achieving the excellent effect of reducing torque ripple while maintaining a relatively simple configuration.

[0021] In this embodiment, first electromagnetic steel sheets 12 and second electromagnetic steel sheets 13 are formed by flipping one type of electromagnetic steel sheet of the same shape over. In this way, the electromagnetic steel sheets that make up stator core 7 can be used as either first electromagnetic steel sheets 12 or second electromagnetic steel sheets 13 by flipping them over as needed, so only one type of electromagnetic steel sheet needs to be manufactured. This makes it easier to manufacture electromagnetic steel sheets 12 and 13, and an even simpler configuration can be achieved.

[0022] In particular, in this embodiment, the starting point S for cutting the protrusions 11 on the electromagnetic steel sheets 12, 13 is offset from the center line O of the tooth portion 10 in the opposite direction from the cutting side. This allows for an excellent torque ripple reduction effect. More specifically, the cutting position for the protrusions 11 on the electromagnetic steel sheets 12, 13 is set to a straight line L extending from the starting point S toward the other circumferential direction and forming an angle φ of 25° or more with the tip edge of the tooth portion 10. If the angle φ is less than 25°, the torque ripple suppression effect is reduced. However, if the angle φ is made too large, the overall drive torque will be reduced.

[0023] Furthermore, in this embodiment, the starting point S is set to the position where the tip of the tooth portion 10 intersects with an imaginary line V that is shifted in one circumferential direction by an angle θ from the center line O of the tooth portion 10, and the angle θ is calculated using the following equation (1): θ=360 / (P*n) / 2 (where P is the number of poles and n is the reduced torque ripple multiple component for frequency f). This provides an excellent torque ripple reduction effect.

[0024] In addition, in this embodiment, the stator core 7 is configured by alternately stacking first blocks 14, each formed by stacking a plurality of first electromagnetic steel sheets 12, and second blocks 15, each formed by stacking an equal number of second electromagnetic steel sheets 13. This makes it possible to easily manufacture the stator core 7, while still achieving a sufficient torque ripple reduction effect, compared to stacking the electromagnetic steel sheets 12, 13 one by one.

[0025] 10 shows a second embodiment, in which the lamination form of the first electromagnetic steel sheets 12 and the second electromagnetic steel sheets 13 in a stator core 21 is different from that of the first embodiment. That is, the stator core 21 of the second embodiment is configured by laminating the first electromagnetic steel sheets 12 and the second electromagnetic steel sheets 13 alternately, one by one. In this case, the lamination process is somewhat more tedious than when the electromagnetic steel sheets 12, 13 are laminated as blocks, but the first blocks 32 can be made to be excellent in reducing torque ripple.

[0026] 11 shows a stator core 31 according to a third embodiment. In this third embodiment, half the number of first electromagnetic steel sheets 12 are stacked to form a first block 32, and the same number of second electromagnetic steel sheets 13 are stacked to form a second block 33. The first block 32 and the second block 33 are then stacked to form the stator core 31. This method is slightly less effective in reducing torque ripple, but it allows the stator core 31 to be manufactured most simply.

[0027] Although the above embodiment is applied to a 4-pole, 6-slot motor 1, it can be applied to various uses and types of rotating electrical machines with different numbers of poles and slots. In this case, the above formula (1) can be excluded from application if the position of the starting point S is out of alignment with the protrusion 11 of the tooth portion 10. Also, various changes can be made to the shape and size of the tooth portion 10 and the protrusion 11. The protrusion may be cut along a curved line instead of a straight line L.

[0028] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0029] In the drawings, 1 indicates a three-phase synchronous motor (rotating electric machine), 3 indicates a stator, 4 indicates a rotor, 5 indicates a rotor core, 6 indicates a permanent magnet, 7, 21, and 31 indicate a stator core, 7a indicates a slot, 8 indicates a winding, 9 indicates a yoke portion, 10 indicates a teeth portion, 11 indicates a protrusion, 12 indicates a first electromagnetic steel sheet, 13 indicates a second electromagnetic steel sheet, 14 indicates a first block, 15 indicates a second block, 32 indicates a first block, and 33 indicates a second block.

Claims

1. A stator core for a rotating electric machine is configured by laminating electromagnetic steel sheets in the axial direction, and has a plurality of teeth extending in the inner circumferential direction on the inner periphery of an annular yoke portion, and has protrusions at the tips of the teeth extending on both sides in the circumferential direction, the electromagnetic steel sheets include a first electromagnetic steel sheet in which one side of a protruding portion of the tooth portion facing forward in the clockwise direction of rotation is cut, and a second electromagnetic steel sheet in which one side of a protruding portion of the tooth portion facing forward in the counterclockwise direction of rotation is cut, the first electromagnetic steel sheets and the second electromagnetic steel sheets are laminated in equal numbers, A stator core of a rotating electric machine, wherein the position at which the protruding portion in the electromagnetic steel plate is cut is set to start from a position at the tip of the tooth portion that is shifted in the opposite direction from the cutting side relative to the center line of the tooth portion.

2. 2. A stator core for a rotating electric machine according to claim 1, wherein the position at which the protrusion in the electromagnetic steel plate is cut is from the starting point toward the other circumferential direction at an angle of 25 degrees or more with respect to the tip edge of the tooth portion.

3. The starting point is a position where a virtual line that is shifted in one circumferential direction by an angle θ from a center line of the tooth intersects with a tip end of the tooth, and The angle θ is θ=360 / (P*n) / 2 (1) (where P is the number of poles, and n is the reduced torque ripple multiple component for the frequency) 3. The stator core of claim 1, wherein the axial length of the stator core is determined by the following formula:

4. 4. A stator core for a rotating electric machine according to claim 1, wherein the first electromagnetic steel sheets and the second electromagnetic steel sheets are alternately stacked one by one, or the first electromagnetic steel sheets and the second electromagnetic steel sheets are alternately stacked as blocks each having a plurality of sheets stacked one on top of the other.

5. 5. The stator core for a rotating electric machine according to claim 1, wherein the first electromagnetic steel sheets and the second electromagnetic steel sheets are formed by flipping electromagnetic steel sheets of the same shape over one another.

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