Stator core
The stator core design optimizes weld lengths on core blocks to prevent disintegration and eddy current losses by varying weld lengths based on weight distribution, integrating riveting for structural integrity.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-12-20
- Publication Date
- 2026-07-02
AI Technical Summary
The existing stator cores experience disintegration due to the weight of core blocks during transport and lifting, necessitating extensive welds that increase eddy current losses.
A stator core design with varying weld lengths on core blocks, where upper blocks have longer welds to withstand weight and lower blocks have shorter welds, integrated with riveting, to prevent disintegration and reduce eddy current losses.
Prevents core block disintegration and minimizes eddy current losses by optimizing weld lengths based on weight distribution, ensuring structural integrity and reducing electrical connectivity.
Smart Images
Figure 2026110086000001_ABST
Abstract
Description
Technical Field
[0001] The technology disclosed in this specification relates to a stator core for a rotating electrical machine.
[0002] Patent Document 1 discloses a stator core for a rotating electrical machine having a cylindrical shape centered on a central axis. The stator core has a configuration in which a plurality of core blocks are laminated in the axial direction. Each of the plurality of core blocks has a structure in which a plurality of electromagnetic steel sheets are laminated in the axial direction and are caulked and integrated with each other. A welded portion extending in the axial direction is formed on the outer peripheral surface of the stator core. The plurality of core blocks are fixed to each other by the welded portion.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In some cases, the stator core is transported with its central axis aligned with the vertical direction. During this transport, the top of the stator core may also be held and lifted. In this case, each of the multiple core blocks experiences a downward vertical force due to its own weight. To prevent the crimping from failing and the core blocks from disintegrating due to this weight, a structure is used in which linear welds extending axially are formed on the outer surface of the stator core. By fixing the electromagnetic steel sheets together with these welds, the disintegration of the core blocks can be prevented. However, to prevent disintegration of all multiple core blocks, it is necessary to form welds along the entire axial length of the outer surface of all core blocks. This results in a large total length of welds. Eddy current losses occur in the welds because the electromagnetic steel sheets, which were previously insulated by a coating, are electrically connected. Therefore, the larger the total length of the welds, the greater the eddy current losses. [Means for solving the problem]
[0005] The stator core for a rotating electric machine disclosed herein has a cylindrical shape with respect to a central axis. The stator core comprises a plurality of core blocks arranged along an axial direction parallel to the central axis. Each of the plurality of core blocks comprises a plurality of electrical steel sheets that are stacked in the axial direction and integrated by being crimped together. A plurality of welds are formed on the outer circumferential surface of the stator core, each extending in the axial direction. The plurality of core blocks comprises a first core block located on the outermost side in the axial direction and a second core block located on the outermost side in the axial direction. The total length of the welds on the outer circumferential surface of the second core block is shorter than the total length of the welds on the outer circumferential surface of the first core block.
[0006] This section describes the case where the stator core is held and lifted while the first core block is positioned vertically above the second core block. In this case, the first core block, located at the upper vertical end, is subjected to its own weight plus the weight of all core blocks located vertically below it. On the other hand, the second core block, located at the lower vertical end, is subjected only to its own weight. Therefore, the second core block is lighter than the first core block. In the above configuration, the total length of the weld on the outer surface of the second core block is shorter than the total length of the weld on the outer surface of the first core block. That is, the total length of the weld is shorter because the second core block is lighter than the first core block. In other words, the fixing force of the electromagnetic steel sheet by the weld is reduced in proportion to the reduced weight. This makes it possible to shorten the total length of the weld while preventing the first and second core blocks from falling apart due to their own weight. This makes it possible to achieve both the prevention of core block disintegration and the suppression of eddy current losses. [Brief explanation of the drawing]
[0007] [Figure 1] This is a schematic top view of the stator core 20. [Figure 2] This is a cross-sectional view along line II-II in Figure 1. [Figure 3] This is a cross-sectional view of the stator core 120 of the comparative example. [Figure 4] This is a cross-sectional view of the stator core 220 of Example 2. [Modes for carrying out the invention]
[0008] The multiple welds may include first and second welds that are aligned in the same line and separated from each other. At least a portion of the first weld may be formed on the outer circumferential surface of the first core block. At least a portion of the second weld may be formed on the outer circumferential surface of the second core block. The axial length of the second weld may be less than the axial length of the first weld.
[0009] This section describes the case where the stator core is held at its upper part and lifted, with the first core block positioned vertically above the second core block. Since the second core block is located below the first core block, the second core block has less self-weight. In other words, the second core block is less likely to decompose due to its own weight. With the above configuration, by making the axial length of the second weld shorter than the axial length of the first weld, it is possible to shorten the total length of the weld while preventing the core block from decomposing due to its own weight.
[0010] The first weld may be formed over the entire axial length on the outer surface of the first core block. The second weld may be formed over only a portion of the axial length on the outer surface of the second core block.
[0011] According to the above configuration, it is possible to shorten the total length of the welded section while preventing the core block from disintegrating due to its own weight.
[0012] The second weld may be formed so as to straddle the boundary between the second core block and the core block adjacent to the second core block.
[0013] According to the above configuration, the second core block and the core block adjacent to the second core block can be fixed to each other by the second weld.
[0014] The multiple core blocks may include at least one intermediate core block positioned between the first core block and the second core block. The multiple welds may include third and fourth welds extending axially from within the first core block toward the second core block. The axial length of the fourth weld may be less than the axial length of the third weld. The positions of the third weld and the fourth weld on the outer surface of the stator core may be different.
[0015] According to the above configuration, it is possible to shorten the total length of the welded section while preventing the core block from disintegrating due to its own weight. [Examples]
[0016] (Structure of stator core 20) Figure 1 shows a schematic top view of a stator core 20 for a rotating electric machine according to this embodiment. In Figure 1, the z direction is the direction in which the central axis CA extends. The x and y directions are directions in a plane perpendicular to the central axis CA. The coordinate relationships are the same in subsequent figures. For the purpose of clarity in the illustration, only one of the repeatedly arranged components may be given a reference numeral.
[0017] The stator core 20 is a cylindrical member with a central axis CA. The stator core 20 has a cylindrical back yoke 20y. Multiple convex teeth 20a are provided on the inner circumferential surface of the back yoke 20y. Slot portions SL are formed between adjacent teeth 20a.
[0018] The stator core 20 comprises a plurality of fixing parts 21 and a plurality of welded parts 22. The plurality of fixing parts 21 are integrally formed with the stator core 20. The plurality of fixing parts 21 are arranged along the outer peripheral surface 20s of the stator core 20. The plurality of fixing parts 21 are arranged at equal intervals in the circumferential direction with respect to the central axis CA. In the example of Figure 1, four fixing parts 21 are arranged with 90-degree rotational symmetry. Each of the plurality of fixing parts 21 has a through hole 21h parallel to the central axis CA.
[0019] The welded part 22 is a bead formed on the metal part joined by welding. The welded part 22 extends in the axial direction (z direction). A plurality of welded parts 22 are formed on the outer peripheral surface 20s of the stator core 20. The plurality of welded parts 22 are arranged differently in the circumferential direction centered on the central axis CA. In the example of FIG. 1, four welded parts 22a to 22d are arranged at equal intervals in the circumferential direction.
[0020] FIG. 2 shows a cross-sectional view taken along the line II-II of FIG. 1. FIG. 2 is a cross-sectional view passing through the central axis CA and passing through two welded parts 22a and 22c. In FIG. 2, compared with FIG. 1, the dimension in the x direction is reduced. Also, for clarity, the first core block CB1, the intermediate core blocks CBb and CBd are shown by gray filling.
[0021] The stator core 20 includes a plurality of core blocks arranged along the axial direction (z direction) parallel to the central axis CA. Each of the plurality of core blocks has the same shape. The number of stacked core blocks may vary. In this embodiment, the stator core 20 is composed of six core blocks. The six core blocks include a first core block CB1, four intermediate core blocks CBa to CBd, and a second core block CB2. The first core block CB1 is the core block located on the most one side (+z direction side) in the axial direction. The second core block CB2 is the core block located on the most other side (-z direction side) in the axial direction. The intermediate core blocks CBa to CBd are blocks arranged between the first core block CB1 and the second core block CB2.
[0022] Each of the six core blocks includes a plurality of electromagnetic steel sheets 25 stacked in the axial direction. The number of stacked electromagnetic steel sheets 25 constituting the core block may vary. In this embodiment, one core block is composed of five electromagnetic steel sheets 25 stacked.
[0023] Each of the six core blocks is equipped with multiple crimped sections CR (see Figure 1). The multiple crimped sections CR are arranged along the circumferential direction with respect to the central axis CA. The multiple crimped sections CR are the parts that integrate the five electromagnetic steel sheets 25 that make up the core block by crimping them together.
[0024] A boundary BD1 is formed between the first core block CB1 and the intermediate core block CBa. A boundary BD2 is formed between the intermediate core blocks CBa and CBb. A boundary BD3 is formed between the intermediate core blocks CBb and CBc. A boundary BD4 is formed between the intermediate core blocks CBc and CBd. A boundary BD5 is formed between the intermediate core block CBd and the second core block CB2. Boundaries BD1 to BD5 are not fixed by crimping. Boundaries BD1 to BD5 are fixed to each other by a welded joint 22, as will be described later.
[0025] As shown in Figure 2, the weld 22a includes a first weld 22a1 and a second weld 22a2. The first weld 22a1 and the second weld 22a2 are aligned on the same line and are separated from each other. The axial length of the first weld 22a1 is length L1. The axial length of the second weld 22a2 is length L2. Length L2 is smaller than length L1.
[0026] At least a portion of the first weld 22a1 is formed on the outer circumferential surface CB1s of the first core block CB1. In the example in Figure 2, the upper end UE1 of the first weld 22a1 is located at the +z end of the first core block CB1. The lower end LE1 of the first weld 22a1 is located within the intermediate core block CBd. In other words, the first weld 22a1 is formed to straddle the boundary BD1 to BD4. This allows the first core block CB1 and the intermediate core blocks CBa to CBd to be fixed together as a single unit. Furthermore, on the outer circumferential surface CB1s of the first core block CB1, the outer circumferential surface CBas of the intermediate core block CBa, the outer circumferential surface CBbs of the intermediate core block CBb, and the outer circumferential surface CBcs of the intermediate core block CBc, the first weld 22a1 is formed over the entire axial direction. This allows the electrical steel sheets to be fixed together in the first core block CB1 and the intermediate core blocks CBa to CBc.
[0027] At least a portion of the second weld 22a2 is formed on the outer circumferential surface CB2s of the second core block CB2. In the example shown in Figure 2, the upper end UE2 of the second weld 22a2 is located within the intermediate core block CBd. The lower end LE2 of the second weld 22a2 is located within the second core block CB2. In other words, the second weld 22a2 is formed to straddle the boundary BD5. This allows the intermediate core block CBd and the second core block CB2 to be fixed to each other. Furthermore, on the outer circumferential surface CB2s of the second core block CB2, the second weld 22a2 is formed only in a portion of the axial direction. Therefore, in the region RW of the second core block CB2 where the second weld 22a2 is not formed, the electromagnetic steel sheet 25 is fixed only by riveting.
[0028] Similarly, weld 22b includes a first weld 22b1 and a second weld 22b2. Weld 22c includes a first weld 22c1 and a second weld 22c2. Weld 22d includes a first weld 22d1 and a second weld 22d2. The configuration of the first welds 22b1 to 22d1 is the same as that of the first weld 22a1 described above. The configuration of the second welds 22b2 to 22d2 is the same as that of the second weld 22a2 described above. Therefore, a detailed explanation is omitted.
[0029] On the outer circumferential surface CB1s of the first core block CB1, first welds 22a1 to 22d1 are arranged in the circumferential direction. Each of the first welds 22a1 to 22d1 is formed over the entire axial length of the outer circumferential surface CB1s (i.e., over five electrical steel sheets) (see Figure 3, region R1). Therefore, the total length of the welds on the outer circumferential surface CB1s corresponds to the thickness of 20 electrical steel sheets. On the outer circumferential surface CB2s of the second core block CB2, second welds 22a2 to 22d2 are arranged in the circumferential direction. Each of the second welds 22a2 to 22d2 is formed over only a portion of the outer circumferential surface CB2s (i.e., over only one electrical steel sheet). Therefore, the total length of the welds on the outer circumferential surface CB2s corresponds to the thickness of four electrical steel sheets. In other words, the total length of the welds on the outer circumferential surface CB2s of the second core block CB2 is shorter than the total length of the welds on the outer circumferential surface CB1s of the first core block CB1.
[0030] (Method for manufacturing the stator core 20) An electrical steel sheet is punched into the planar shape of the stator core 20 by a punching mechanism (not shown). The punched electrical steel sheet has a fixing portion 21 and teeth 20a, as shown in Figure 1. Five punched electrical steel sheets are stacked and a crimped portion CR is formed using a press machine. This completes the core block.
[0031] Next, as shown in Figure 2, the six core blocks are stacked axially, and then welded to the outer surface 20s. The welding is performed by methods such as TIG welding. This forms a welded joint 22. The boundaries BD1 to BD5 are welded together by the welded joint 22. As a result, the six core blocks are integrated, and the stator core 20 is completed.
[0032] In welding, only the outermost layer of the outer surface 20s is welded. This minimizes the generation of eddy currents and the increase in iron loss in the welded area 22.
[0033] (assignment) The problem will be explained using the comparative example stator core 120 shown in Figure 3. Figure 3 is a drawing of the same embodiment as Figure 2. The comparative example stator core 120 (Figure 3) differs from the stator core 20 of this embodiment (Figure 2) in the structure of the welded parts 122a and 122c. Components common to both Figure 3 and Figure 2 are denoted by the same reference numerals, and their explanation is omitted.
[0034] In some cases, the stator core is transported with its central axis CA aligned with the vertical direction (z direction). During this transport, the top of the stator core may be held and lifted upwards (towards arrow Y1). In this case, each of the six core blocks experiences a downward (-z) force due to its own weight. To prevent the crimping portion CR from breaking and the core block from disintegrating due to this weight, a structure is used in which linear welds extending axially are formed on the outer surface of the stator core. By fixing the electromagnetic steel sheets together with these welds, the disintegration of the core block can be prevented. However, because the electromagnetic steel sheets, which were previously insulated by a coating, are electrically connected at the welds, eddy current losses occur. Therefore, the eddy current losses increase as the total length of the welds increases.
[0035] In the comparative example stator core 120 (Figure 3), welds 122a and 122c are formed on the outer circumferential surface of the six core blocks along their entire axial length. That is, the welds 122a and 122c are formed continuously from the upper end 120U to the lower end 120L of the stator core 120. Due to the large total length of the welds, there was a problem of large eddy current losses.
[0036] (effect) Figure 2 illustrates the case where the upper part of the stator core 20 is held and lifted upward (towards arrow Y1). In this case, the first core block CB1, located at the upper vertical end, is subjected to its own weight in addition to the weight of all the core blocks located vertically below it (intermediate core blocks CBa to CBd and the second core block CB2). On the other hand, the second core block CB2, located at the lower vertical end, is subjected only to its own weight. Therefore, the applied load to the second core block CB2 is smaller than that to the first core block CB1. In other words, the lower the core block is vertically, the less likely it is that crimping failure due to its own weight will occur (the less likely it is that the core block will disintegrate).
[0037] Therefore, in the technology of this embodiment, as described above, the total length of the weld on the outer surface CB2s of the second core block CB2 is made shorter than the total length of the weld on the outer surface CB1s of the first core block CB1. In other words, the fixing force of the electromagnetic steel sheet by the weld is reduced in proportion to the reduced applied load. This makes it possible to shorten the total length of the weld while preventing the disintegration of the first core block CB1 and the second core block CB2 due to their own weight. This makes it possible to achieve both prevention of core block disintegration and suppression of eddy current loss.
[0038] In the technology of this embodiment, the length L2 of the second weld 22a2, located on the lower side, is smaller than the length L1 of the first weld 22a1, located on the upper side. That is, in the core blocks located on the upper side, which have a greater self-weight (first core block CB1, intermediate core blocks CBa to CBc), the first weld 22a1 is formed along the entire axial direction of the outer circumferential surface. Since the electromagnetic steel sheets can be fixed together by the first weld 22a1, disintegration of the core blocks due to their own weight can be prevented. In the core blocks located on the lower side, which have a smaller self-weight (intermediate core block CBd and second core block CB2), the electromagnetic steel sheets can be sufficiently fixed together by riveting. Therefore, since the second weld 22a2 only needs to be formed at the boundary between the core blocks, the length of the weld can be shortened. Disintegration of the core blocks due to their own weight can be prevented while shortening the total length of the weld. Thus, eddy current loss can be suppressed. The same effect as described above can be obtained in the welds 22b to 22d. [Examples]
[0039] (Configuration of base section 220b) Figure 4 shows a cross-sectional view of the stator core 220 of Example 2. Figure 4 is a drawing showing the same region as Figure 2. That is, Figure 4 is a cross-sectional view passing through the central axis CA and the two third welds 23 and fourth welds 24. The stator core 220 of Example 2 (Figure 4) differs from the stator core 20 of Example 1 (Figure 2) in that it has a third weld 23 and a fourth weld 24. Components common to both Figure 4 and Figure 2 are denoted by the same reference numerals, and their explanation is omitted.
[0040] The third weld 23 and the fourth weld 24 are located at different positions on the outer circumferential surface of the stator core 220. Specifically, the third weld 23 is located at the -x end in the circumferential direction, and the fourth weld 24 is located at the +x end in the circumferential direction. The axial length of the third weld 23 is L3, and the axial length of the fourth weld 24 is L4. L4 is smaller than L3.
[0041] The third weld 23 extends axially from within the first core block CB1 toward the second core block CB2. Specifically, the third weld 23 is formed continuously from the upper end 220U to the lower end 220L of the stator core 220. This allows all core blocks (first core block CB1, intermediate core blocks CBa to CBd, and second core block CB2) to be fixed together as a single unit. Furthermore, electrical steel sheets can be fixed together within each of the core blocks.
[0042] The fourth weld 24 extends axially from within the first core block CB1 toward the second core block CB2. Specifically, the fourth weld 24 extends from within the first core block CB1 toward the intermediate core block CBd. This allows the five upper core blocks (first core block CB1 and intermediate core blocks CBa to CBd) to be fixed together as a single unit. Furthermore, electrical steel sheets can be fixed together within each of the four upper core blocks (first core block CB1 and intermediate core blocks CBa to CBc).
[0043] (effect) Figure 4 illustrates the case where the upper part of the stator core 220 is held and lifted upward (towards arrow Y1). In this case, as mentioned above, the weight of the core block decreases as it moves vertically downward, making it less likely for the crimp to fail due to its own weight (making it less likely for the core block to disintegrate). Therefore, in the technology of this embodiment, the axial lengths of the multiple welds arranged in the circumferential direction are made different. Specifically, the length L4 of the fourth weld 24 is made shorter than the length L3 of the third weld 23. In other words, the fourth weld 24 is omitted in the vertically downward core block where disintegration of the core block is less likely to occur. This makes it possible to shorten the total length of the welds while preventing disintegration due to the weight of the core block. It also makes it possible to suppress eddy current losses.
[0044] (Modified version of Example 2) The third weld 23 and fourth weld 24 shown in Example 2 are just examples. The third weld 23 and fourth weld 24 can take various forms as long as the length L4 is smaller than the length L3 and the upper ends of the third weld 23 and fourth weld 24 are located within the first core block CB1. Furthermore, the upper ends of the third weld 23 and fourth weld 24 do not necessarily have to be located at the upper end 220U of the stator core 220, but may be located within the outer circumferential surface CB1s.
[0045] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness.
[0046] (modified version) The arrangement of the welded joint 22 (Figure 2), the third welded joint 23, and the fourth welded joint 24 (Figure 4) can vary, and these welded joints may be arranged in combination. For example, some of the welded joints among the multiple welded joints arranged along the circumferential direction may be welded joint 22, the third welded joint 23, the fourth welded joint 24, etc. [Explanation of Symbols]
[0047] 20: Stator core 20s: Outer surface 22: Welded joint 25: Electrical steel sheet CB1: First core block CB1s: Outer surface CB2: Second core block CB2s: Outer surface CBa~CBd: Intermediate core block
Claims
1. A stator core for a rotating electric machine having a cylindrical shape centered on a central axis, It comprises a plurality of core blocks arranged along an axial direction parallel to the central axis, Each of the aforementioned multiple core blocks comprises multiple electromagnetic steel sheets that are stacked in the axial direction and integrated by crimping each other. Multiple welded joints, each extending in the axial direction, are formed on the outer circumferential surface of the stator core. The plurality of core blocks include a first core block located furthest to one side in the axial direction and a second core block located furthest to the other side in the axial direction. The total length of the welded portion on the outer circumferential surface of the second core block is shorter than the total length of the welded portion on the outer circumferential surface of the first core block. Stator core.
2. The plurality of welds include a first weld and a second weld that are arranged on the same straight line and separated from each other. At least a portion of the first weld is formed on the outer circumferential surface of the first core block, At least a portion of the second weld is formed on the outer circumferential surface of the second core block, The stator core according to claim 1, wherein the axial length of the second weld is smaller than the axial length of the first weld.
3. The first welded portion is formed on the outer circumferential surface of the first core block, extending over the entire axial direction. The stator core according to claim 2, wherein the second welded portion is formed on the outer circumferential surface of the second core block in only a portion of the axial direction.
4. The stator core according to claim 3, wherein the second welded portion is formed to straddle the boundary between the second core block and a core block adjacent to the second core block.
5. The plurality of core blocks each include at least one intermediate core block positioned between the first core block and the second core block. The plurality of welds include a third weld and a fourth weld that extend axially from within the first core block toward the second core block. The axial length of the fourth weld is smaller than the axial length of the third weld. The stator core according to any one of claims 1 to 4, wherein the positions of the third weld and the fourth weld on the outer circumferential surface of the stator core are different.