Rotors, electric motors, and washing machines

Abstract

By thinning the electrical steel sheet without increasing the processing steps or causing warping radially outward, performance degradation due to magnetic flux leakage radially inward is suppressed. [Solution] A rotor comprising a laminate of stacked electromagnetic steel sheets, a shaft arranged along the central axis of the laminate, and permanent magnets arranged inside the laminate, wherein the bridge portion of the electromagnetic steel sheet between the hub portion that holds the shaft and the spoke portion that holds the permanent magnets is convex in the direction opposite to the sagging direction caused by punching, and has a thinner wall portion than the hub portion and the spoke portion.

Description

Technical Field

[0001] The present invention relates to a rotor, a motor, and a washing machine.

Background Art

[0002] Patent Document 1 describes a rotor of a permanent magnet motor. This rotor includes a plurality of permanent magnets arranged in a substantially circumferential shape such that adjacent magnetic poles are different. This rotor has a rotary shaft hole provided at the center of the rotary shaft, arranges a plurality of permanent magnets near the outer periphery, provides a thin portion between the rotary shaft hole and the permanent magnets and closer to the rotary shaft hole, and includes a laminated iron core formed by laminating magnetic plates. This rotor includes a rotary shaft fitted into the rotary shaft hole of the laminated iron core. When the magnetic flux density passing through the magnetic plate is Φ, the saturation magnetic flux density of the material of the magnetic plate is Bs, the plate thickness of the magnetic plate where the thin portion is not formed is t1, and the plate thickness of the magnetic plate of the thin portion is t2, the thin portion is formed in a region satisfying the relationship of Φ < Bs × t2 / t1.

[0003] Patent Document 2 describes a permanent magnet embedded type motor including a stator in which windings are wound around a stator core, and a rotor rotatably arranged via a gap on the inner peripheral surface of the stator core. The rotor includes a rotor core formed by laminating steel plates having a plurality of magnet embedding holes, permanent magnets respectively housed and held in the magnet embedding holes, and in each of the magnet embedding holes, a first gap portion which is a portion between the magnet embedding hole and the housed and held permanent magnet and located at both circumferential ends in the magnet embedding hole where no permanent magnet exists. The plate thicknesses of a bridge portion formed between each end of adjacent magnet embedding holes and the outer periphery of the steel plate and a thin connecting portion connecting the bridge portions formed between adjacent magnet embedding holes are thinner than the plate thickness of the steel plate. When the plate thickness of the bridge portion is d2, the radial width of the bridge portion is t1, and the plate thickness of the steel plate is d1, d2 ≤ t1 < d1.

[0004] Patent Document 3 describes a rotor laminate package comprising a plurality of flat rotor laminates for a rotating electric machine, particularly a brushless synchronous motor. The rotor laminate has a hub having a hub axis and at least two spokes evenly distributed radially around the hub axis. A pair of first rotor laminates is rotated 180° relative to a second rotor laminate of the same pair and aligned around an axis perpendicular to the hub axis. The rotor laminate is formed in the hub region, and the thickness of the laminate in the hub region is at least reduced compared to the thickness of the spoke laminate, particularly at least 40% to 60%, and preferably at least 50%. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-220388 [Patent Document 2] Japanese Patent Publication No. 2016-007136 [Patent Document 3] International Publication No. 2013 / 053479 [Overview of the project] [Problems that the invention aims to solve]

[0006] In rotors equipped with laminates of electrical steel sheets, magnetic flux leakage can occur radially inward from the spokes that hold the magnets in the electrical steel sheets. This reduces the magnetic flux radially outward from the spokes, resulting in a deterioration of performance. To suppress this deterioration in performance, one option is to thin the portion of the electromagnetic steel sheet where magnetic flux flows radially inward from the spoke area. However, when thinning the sheet, it is necessary to avoid increasing the number of processing steps or causing warping radially outward.

[0007] The objective of this invention is to thin the electrical steel sheet without increasing the number of processing steps or causing warping radially outward, thereby suppressing the deterioration of performance due to leakage of magnetic flux radially inward. [Means for solving the problem]

[0008] To this end, the present invention provides a rotor comprising a laminate of electrical steel sheets, a shaft arranged along the central axis of the laminate, and a permanent magnet disposed inside the laminate, wherein the bridge portion of the electrical steel sheet between the hub portion that holds the shaft and the spoke portion that holds the permanent magnet has a convex shape in the opposite direction to the sagging direction caused by punching, and has a thin-walled portion that is thinner than the hub portion and the spoke portion.

[0009] In the rotor described above, if the magnetic flux density passing through the electrical steel sheet is Φ, the saturation magnetic flux density of the electrical steel sheet material is Bs, the thickness of the electrical steel sheet in the non-thin portion is t1, and the thickness of the electrical steel sheet in the thin portion is t2, then the relationship Φ > Bs × t2 / t1 may hold.

[0010] The rotor described above may be a spoke rotor.

[0011] The present invention also provides an electric motor equipped with any of the rotors described above.

[0012] The above-mentioned electric motor may be used at rotational speeds ranging from 400 revolutions per minute to 20,000 revolutions per minute.

[0013] Furthermore, the present invention also provides a washing machine equipped with the above-mentioned electric motor. [Effects of the Invention]

[0014] According to the present invention, it is possible to thin the electromagnetic steel sheet without increasing the number of processing steps or causing warping radially outward, thereby suppressing deterioration of performance due to leakage of magnetic flux radially inward. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows an example configuration of a drum-type washing machine to which this embodiment is applied. [Figure 2]It is a top view showing a configuration example of a general electromagnetic steel sheet constituting a rotor. [Figure 3] It is a top view showing a configuration example of a general rotor. [Figure 4] It is a diagram showing problems of a motor using the rotor shown in FIG. 3. [Figure 5] It is a diagram showing the state of the electromagnetic steel sheet when it is first cut. [Figure 6] It is a diagram showing the state of the electromagnetic steel sheet when normal thinning is performed. [Figure 7] It is a diagram showing the state of the electromagnetic steel sheet after cutting the horizontally expanded area. [Figure 8] It is a diagram showing a method of creating a concave-shaped thin portion. [Figure 9] It is a diagram showing a method of creating a convex-shaped thin portion. [Figure 10] It is a perspective view showing a configuration example of the electromagnetic steel sheet in the present embodiment constituting the rotor. [Figure 11] It is a perspective view showing a configuration example of the rotor in the present embodiment. [Figure 12] It is a cross-sectional view of the laminate of the rotor in the present embodiment.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] [Washing Machine] FIG. 1 is a diagram showing a configuration example of a drum-type washing machine 1 to which the present embodiment is applied. As shown in the figure, the washing machine 1 includes a housing 2 having a substantially box-shaped appearance. The washing machine 1 further includes a tub 3 in which washing water is stored. The washing machine 1 further includes a drum 4 that is rotatably installed inside the tub 3 and in which a number of through holes are formed.

[0018] Openings 3a and 4a are provided on the front surfaces of the tub 3 and the drum 4, and a door 6 for opening and closing the openings 3a and 4a is hinge-coupled to the front surface of the housing 2.

[0019] At the top of the housing 2, a water supply pipe 7a for receiving washing water from the outside and a detergent container 7b for mixing detergent with the washing water supplied through the water supply pipe 7a are installed. At the bottom of the housing 2, a drain pump 8a and a drain hose 8b are installed for discharging the washing water to the outside of the housing 2 after the washing is finished.

[0020] Drum 4 is positioned at an upward angle toward the front of the enclosure 2, and tab 3 is also positioned at the same upward angle as drum 4.

[0021] Multiple lifters 4b are arranged at predetermined intervals on the inner surface of the drum 4. These lifters 4b lift the laundry upwards along with the wash water as the drum 4 rotates, and then drop from a predetermined height to wash the laundry.

[0022] The drum 4 is rotatable within the tab 3 because a rotating shaft 4c, fixed to the center of its rear, is supported by the rear portion of the tab 3. The rear end of the rotating shaft 4c is fixed to a pulley 4d. This pulley 4d is connected by a belt 4e to a motor (electric motor) 5 installed at the bottom of the housing 2, thereby transmitting power from the motor 5 to the rotating shaft 4c. Here, the motor 5 includes a rotor 5a and a stator 5b. The rotor 5a is fitted onto the shaft 30 and is rotatable with the shaft 30. The stator 5b is positioned to surround the rotor 5a with an air gap, and rotates the rotor 5a due to the magnetic force generated by the current flowing through the winding coils.

[0023] [rotor] Figure 2 is a top view showing an example of the configuration of a typical electrical steel sheet 10 that constitutes the rotor 5a. As shown in the figure, the electrical steel sheet 10 has a hub portion 11, a spoke portion 12, and a bridge portion 13.

[0024] The hub portion 11 is a ring-shaped member provided inside the rotor 5a. The hub portion 11 holds the shaft 30 (see Figure 1) which is located inside 14. The spoke portion 12 is a fan-shaped member provided on the outside of the rotor 5a so as to surround the hub portion 11. Each spoke portion 12 has a rim 121 with a rounded edge. Each rim 121 has the shape of an arc segment. When all the rims 121 of the spoke portions 12 are put together, they form a broken arc. The figure shows eight spoke portions 12, but the number of spoke portions 12 is not limited to this. The spoke portions 12 hold permanent magnets 40 (described later) which are placed between adjacent spoke portions 12. The bridge section 13 is the part that connects the hub section 11 and the spoke section 12. The width of the bridge section 13 is extremely narrow compared to the outer width of the spoke section 12. In Figure 2, the bridge section 13 is flat.

[0025] Figure 3 is a top view showing a typical configuration of a rotor 5a. The rotor 5a comprises a laminate 20, a shaft 30 (see Figure 1), and permanent magnets 40.

[0026] The laminate 20 is made by laminating electrical steel sheets 10. The laminate 20 has a hub laminate 21, a spoke laminate 22, and a bridge laminate 23. The hub laminate 21 is the part of the laminate 20 in which the hub portion 11 of the electrical steel sheet 10 is laminated. The spoke laminate 22 is the part of the laminate 20 in which the spoke portion 12 of the electrical steel sheet 10 is laminated. The bridge laminate 23 is the part of the laminate 20 in which the bridge portion 13 of the electrical steel sheet 10 is laminated.

[0027] The shaft 30 is positioned along the central axis of the laminate 20. Specifically, the shaft 30 is positioned inside the hub laminate 21 of the laminate 20.

[0028] The permanent magnets 40 are arranged inside the laminate 20. Specifically, the permanent magnets 40 are arranged radially between adjacent spoke laminates 22 of the laminate 20. The permanent magnets 40 are arranged so that opposing faces have the same magnetic poles. In this case, the magnetic poles of the spoke laminate 22 sandwiched between adjacent permanent magnets 40 will have magnetic flux with the same poles as the opposing faces of the permanent magnets 40. The magnetic flux of the magnetic poles of each spoke laminate 22 repels and attracts the magnetic field of the stator 5b (see Figure 1), causing the rotor 5a to rotate relative to the stator 5b. Such a rotor 5a is also called a spoke rotor.

[0029] Figure 4 shows the problems with the motor 5 using the rotor 5a shown in Figure 3. As shown in the diagram, in such a motor 5, magnetic flux flows as indicated by arrow F1. That is, magnetic flux flows from the rotor 5a to the stator 5b, and then returns from the stator 5b to the rotor 5a. As a result, the rotor 5a rotates and produces output. On the other hand, in such a motor 5, as indicated by arrow F2, some of the magnetic flux flows radially inward from the rotor 5a, which results in losses and leads to a deterioration in the performance of the motor 5. Therefore, in this embodiment, by thinning the bridge portion 13 of the electromagnetic steel sheet 10, the magnetic flux flowing radially inward of the rotor 5a is magnetically saturated, making it difficult for the magnetic flux to flow.

[0030] Here, we will explain in detail how to thin the bridge portion 13 of the electrical steel sheet 10. Figure 5 shows the state of the electrical steel sheet 10 when it was first cut. As shown in the figure, sagging 139 occurs in the cut surface of the bridge portion 13 of the electrical steel sheet 10. Here, the direction of the sagging 139 is assumed to be downward in the figure. Sagging also occurs in the cut surfaces of the hub portion 11 and spoke portion 12 of the electrical steel sheet 10, but these are omitted from the illustration here.

[0031] First, let's explain the usual process of thinning walls. Figure 6 shows the state of the electrical steel sheet 10 after normal thinning. In typical thinning processes, the bridge portion 13 is crushed by the press. When the bridge portion 13 is pressed and thinned, it expands laterally by a region 135 corresponding to the amount of thinning. Therefore, a process is needed to cut off the expanded region 135. Figure 7 shows the state of the electrical steel sheet 10 after the horizontally extended region 135 has been cut off.

[0032] Next, the thinning of the wall in this embodiment will be described. In this embodiment, the thinning process involves bending the bridge portion 13 as it is crushed by the press, thereby reducing its thickness. This eliminates the need for the step of cutting the laterally extended region 135.

[0033] First, we will explain the case where the bridge portion 13 is thinned into a concave shape. Figure 8 shows a method for creating a concave, thin-walled section. In Figure 8, a press device (not shown) lowers the stripper 83 toward the die 82 having the recess 821, pressing the electrical steel sheet 10 toward the die 82. The press device then closes the punch 81 and die 82, press-working the electrical steel sheet 10 with the recess 821 of the die 82. At this time, the direction of the curvature of the recess in the electrical steel sheet 10, indicated by arrow C11, and the direction of the curvature of the electrical steel sheet 10 outside the recess, indicated by arrow C12, are the same. As a result, the electrical steel sheet 10 deforms significantly. In this case, when the electrical steel sheets 10 are laminated and crimped, residual stress increases, leading to increased iron loss and potentially degrading performance.

[0034] Furthermore, we will explain the case where the bridge portion 13 is thinned to a convex shape. Figure 9 shows a method for creating a convex-shaped thin-walled section. In Figure 9, a press device (not shown) lowers the stripper 93 toward the die 92 having the protrusion 921, pressing the electrical steel sheet 10 toward the die 92. The press device then closes the punch 91 and die 92, pressing the electrical steel sheet 10 with the protrusion 921 of the die 92. At this time, the direction of the curvature of the protrusion of the electrical steel sheet 10, indicated by arrow C21, is opposite to the direction of the curvature of the electrical steel sheet 10 other than the protrusion, indicated by arrow C22. In other words, the direction of the sag 139 (see Figure 5) of the electrical steel sheet 10 is opposite to the direction of the protrusion of the electrical steel sheet 10. Therefore, the deformation of the electrical steel sheet 10 is reduced.

[0035] Figure 10 is a perspective view showing an example of the configuration of the electromagnetic steel sheet 10 in this embodiment that constitutes the rotor 5a. As shown in the figure, the electromagnetic steel sheet 10 has a hub portion 11, a spoke portion 12, and a bridge portion 13.

[0036] The hub portion 11 and spoke portion 12 have been described with reference to Figure 2, so their explanation will be omitted here. The bridge section 13 is the part that connects the hub section 11 and the spoke section 12. The width of the bridge section 13 is extremely narrow compared to the outer width of the spoke section 12. In Figure 10, the bridge section 13 has a convex shape in the opposite direction to the direction of the punched-out burr 139 (see Figure 5) as shown in Figure 9.

[0037] Figure 11 is a perspective view showing an example of the configuration of the rotor 5a in this embodiment. The rotor 5a comprises a laminate 20, a shaft 30 (see Figure 1), and a permanent magnet 40.

[0038] The laminate 20 is formed by laminating the electromagnetic steel sheets 10 shown in Figure 10. The laminate 20 has a hub laminate 21, a spoke laminate 22, and a bridge laminate 23. The hub laminate 21 and spoke laminate 22 have been described with reference to Figure 3, so their explanation will be omitted. The bridge laminate 23 is the part of the laminate 20 in which the bridge portion 13 of the electromagnetic steel sheets 10 is laminated. In Figure 10, the bridge portion 13 had a convex shape in the opposite direction to the burr 139 (see Figure 5) caused by punching. Therefore, in Figure 11, the bridge laminate 23 as a whole also has a convex shape in the opposite direction to the burr 139 (see Figure 5) caused by punching.

[0039] The shaft 30 and the permanent magnet 40 have been described with reference to Figure 3, so their explanation will be omitted here.

[0040] Figure 12 is a cross-sectional view of the laminated rotor 5a 20 in this embodiment. As shown in the figure, the bridge portion 13 is thinned in the electromagnetic steel sheet 10. As a result, the bridge portion 13 has a thin-walled portion 131 that is thinner than the hub portion 11 and the spoke portion 12.

[0041] Here, let t1 be the thickness of the electrical steel sheet 10 in the portion other than the thinned portion 131. In other words, let t1 be the thickness of the bridge portion 13 before it was thinned. For example, the thickness of the hub portion 11 and the spoke portion 12 can be used as the thickness of the bridge portion 13 before it was thinned. Furthermore, the thickness of the thinned portion 131 of the electromagnetic steel sheet 10 is set to t2. In other words, the thickness of the bridge portion 13 after thinning is set to t2. Furthermore, let Φ be the magnetic flux density passing through the electromagnetic steel sheet 10. For example, let Φ be the magnetic flux density passing through the bridge section 13. Furthermore, let Bs be the saturation magnetic flux density of the material of the electrical steel sheet 10. For example, let Bs be the saturation magnetic flux density of the material of the bridge section 13.

[0042] Therefore, the plate thickness t2 should satisfy the condition "Φ>Bs×t2 / t1". This increases the certainty that magnetic flux saturation occurs in the bridge section 13. As a result, the leakage flux flowing radially inward of the rotor 5a can be reduced, enabling further torque increases for the motor 5. Furthermore, the thinning of the bridge section 13 can be achieved by press working. Consequently, there is no increase in material costs, and high performance can be achieved without significantly raising costs. In addition, by connecting the outer circumference with a thin section, strength can be increased without compromising performance.

[0043] In this embodiment, the rotor 5a rotates at a speed of approximately 500 to 20,000 revolutions per minute in a drum-type washing machine 1 as shown in Figure 1. Specifically, the rotor 5a rotates at a speed of 400 to 700 revolutions per minute during washing and at a speed of 14,000 to 20,000 revolutions per minute during spinning. However, these rotational speeds are based on the assumption that the power of the motor 5 equipped with the rotor 5a is transmitted to the rotating shaft 4c (see Figure 1) of the drum 4 (see Figure 1) by the pulley 4d (see Figure 1).

[0044] [summary] This embodiment can be understood as follows: The rotor of the first embodiment comprises a laminate of electrical steel sheets, a shaft arranged along the central axis of the laminate, and permanent magnets arranged inside the laminate, wherein the bridge portion of the electrical steel sheet between the hub portion that holds the shaft and the spoke portion that holds the permanent magnets is convex in the direction opposite to the burring direction due to punching, and has a thin-walled portion that is thinner than the hub portion and the spoke portion. The rotor of the second embodiment is a rotor in which, in the rotor of the first embodiment, the relationship Φ > Bs × t2 / t1 holds, where Φ is the magnetic flux density passing through the electromagnetic steel sheet, Bs is the saturation magnetic flux density of the electromagnetic steel sheet material, t1 is the thickness of the electromagnetic steel sheet in the part other than the thin-walled portion, and t2 is the thickness of the electromagnetic steel sheet in the thin-walled portion. The rotor of the third embodiment is a spoke rotor in the rotor of the first or second embodiment. The electric motor of the first embodiment is an electric motor equipped with a rotor of any of the first to third embodiments. The electric motor of the second embodiment is an electric motor used in the electric motor of the first embodiment at a rotational speed in the range of 400 revolutions per minute to 20,000 revolutions per minute. The washing machine of the first embodiment is a washing machine equipped with an electric motor of the first embodiment or the second embodiment. [Explanation of Symbols]

[0045] 1...Washing machine, 2...Housing, 3...Tub, 4...Drum, 5...Motor, 5a...Rotor, 5b...Stator, 6...Door, 10...Electromagnetic steel sheet, 11...Hub section, 12...Spoke section, 13...Bridge section, 20...Laminate, 21...Hub laminate, 22...Spoke laminate, 23...Bridge laminate, 30...Shaft, 40...Permanent magnet

Claims

1. A laminate made of stacked electrical steel sheets, A shaft arranged along the central axis of the laminate, A permanent magnet arranged inside the laminate, Equipped with, A rotor in which the bridge portion between the hub portion that holds the shaft and the spoke portion that holds the permanent magnet is convex in the direction opposite to the sagging direction caused by punching, and has a thinner wall portion that is thinner than the hub portion and the spoke portion.

2. The rotor according to claim 1, wherein the relationship Φ > Bs × t2 / t1 holds true when Φ is the magnetic flux density passing through the electrical steel sheet, Bs is the saturation magnetic flux density of the material of the electrical steel sheet, t1 is the thickness of the portion of the electrical steel sheet other than the thin portion, and t2 is the thickness of the thin portion of the electrical steel sheet.

3. The rotor according to claim 1, wherein the rotor is a spoke rotor.

4. An electric motor equipped with the rotor described in any one of claims 1 to 3.

5. The electric motor according to claim 4, which is used at a rotational speed in the range of 400 revolutions per minute to 20,000 revolutions per minute.

6. A washing machine equipped with the electric motor described in claim 4.

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