Rotating electric machine and method for forming slits in rotor slots

Abstract

In order to provide a rotary electric machine with which it is possible to improve heat dissipation characteristics of a rotor and in which temperature characteristics do not decline even when using a die cast rotor, the present invention is characterized by comprising a rotor formed by laminating electromagnetic steel sheet, and a stator disposed on the outer circumference of the rotor, the rotor being a die cast rotor in which a plurality of rotor bars are formed at prescribed intervals in the circumferential direction, the die cast rotor being formed by a die cast member flowing inside a rotor slot extending in the axial direction, the rotor slot being an open slot via which the rotor bar is exposed from a slit formed on the outer circumference, the circumferential direction width of the slit being less than the circumferential direction width of the rotor bar, the side wall of the slit exposing the side surface (laminated surface) of the electromagnetic steel sheet, and the slit being a slit groove in which the depth to the exposed part of the rotor bar is greater than the depth to the non-exposed part of the rotor bar.

Description

Technical Field

[0001] The present invention relates to a rotating electric machine and a method for forming a slit in a rotor slot, and more particularly, to a rotating electric machine and a method for forming a slit in a rotor slot suitable for use in a die-cast rotor in which rotor bars are formed by pouring a die-cast material into the rotor slots.

Background Art

[0002] Generally, in a rotating electric machine composed of a die-cast rotor in which rotor bars are formed by pouring a die-cast material into rotor slots, when operating at a high frequency such as a rotating electric machine for a railway vehicle, heat generated in the die-cast material constituting the die-cast rotor often becomes a problem.

[0003] To address this problem, by forming a slit in the upper part in the radial direction of the rotor slot, that is, adopting a so-called open slot type, the cooling performance can be improved and the heat generation problem can be solved.

[0004] As prior art documents related to such an open slot type, patent documents can be cited.

[0005] In this Patent Document 1, the slot formed in the rotor has an open structure, and a secondary conductor is cast into the open slot structure, and by machining a gas flow path, gas can be forced to flow into the gas flow path provided in the secondary conductor, and the secondary conductor can be effectively cooled, so that a small and efficient induction machine can be realized.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Incidentally, in rotating electric machines using die-cast rotors, when the rotor temperature is mitigated by open slots, securing ventilation passages for the slits formed in the rotor slots becomes a problem.

[0008] In the aforementioned Patent Document 1, the amount of airflow to the slit is ensured by providing blades on a short-circuit ring at the axial end face of the rotor.

[0009] However, in the technology described in Patent Document 1, in the case of a rotating electric machine that assumes high-frequency operation, since the short-circuit ring has blades on the axial end face of the rotor, there are problems with air resistance generated on the outer wall of the ventilation passage and the stress concentration at the end that occurs as a result.

[0010] Furthermore, in rotating electric machines using die-cast rotors, if the rotor slits are created with the same dimensions as the openings, die-cast material will remain on the outer wall of the ventilation passage. Current will then flow through this remaining die-cast material, resulting in higher heat generation and associated losses than anticipated before manufacturing.

[0011] The present invention has been made in view of the above-mentioned points, the eye The objective is to provide a rotating electric machine that, even when using a die-cast rotor, has improved rotor heat dissipation characteristics and does not deteriorate in temperature characteristics. [Means for solving the problem]

[0013] The rotating electric machine of the present invention is Record To achieve the target, a rotor formed by laminating electromagnetic steel sheets and a stator arranged on the outer circumference of the rotor 、 The rotor is provided with a rotor in which a plurality of rotor bars are formed at predetermined intervals in the circumferential direction, and die-cast material is poured into rotor slots that extend in the axial direction. BornThe die-cast rotor is formed, and the rotor slot is an open slot through which the rotor bar is exposed, the circumferential width of the slit is narrower than the circumferential width of the rotor bar, the side wall of the slit exposes the side surface (laminated surface) of the electrical steel sheet, and the slit is a groove in which the depth to the exposed portion of the rotor bar is deeper than the depth to the non-exposed portion of the rotor bar. In addition, the rotor is provided with end rings at both axial ends, and grooves extending from the slits are also formed in the end rings. It is characterized by the following: [Effects of the Invention]

[0015] According to the present invention, even when using a die-cast rotor, it is possible to obtain a rotating electric machine in which the heat dissipation characteristics of the rotor are improved and the temperature characteristics do not deteriorate. kill . [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows a cross-sectional view of the upper half of an electric motor, which is an embodiment 1 of the rotating electric machine of the present invention. [Figure 2(a)] This diagram shows a cross-section of the end ring of a conventional electric motor, and is an enlarged view corresponding to part A in Figure 1. [Figure 2(b)] Figure 2(a) is a cross-sectional view showing the slit of the end ring as seen from the direction of arrow C. [Figure 3(a)] This figure shows a cross-sectional view of the end of the end ring in an electric motor, which is an embodiment 1 of the rotating electric machine of the present invention, and is an enlarged view of part A in Figure 1. [Figure 3(b)] Figure 3(a) is a cross-sectional view showing the slit of the end ring as seen from the direction of arrow C. [Figure 4] This figure shows a conventional method for forming slits in the rotor slot of an electric motor. [Figure 5] This figure shows a method for forming slits in a rotor slot of an electric motor, which is an embodiment 1 of the present invention. [Modes for carrying out the invention]

[0017] Hereinafter, based on the described embodiments, the rotating electric machine and the method for forming the slits of the rotor slots of the present invention will be described. In each figure, the same reference numerals are used for the same components.

Embodiment

[0018] FIG. 1 shows a cross-section of the upper half of the rotating electric machine according to Embodiment 1 of the present invention.

[0019] The rotating electric machine of the present embodiment shown in FIG. 1 is a motor 20, which is composed of a rotor 1 fixed to a rotating shaft 4 and a stator 2 arranged in the radial direction of the rotor 1 and covering the outer periphery of the rotor 1 with a predetermined gap.

[0020] As is well known, by passing an electric current through the stator coil 9 of the stator 2, a rotational force is applied to the rotor 1, and the rotating shaft 4 rotates. A casing 7 is attached to the rotating shaft 4 via a bearing 8.

[0021] The above-described rotor 1 has a structure in which electromagnetic steel sheets are laminated, and its laminated shape is maintained by being bolted (not shown).

[0022] Further, the rotor 1 has rotor slots 5a that are cut from its outer periphery to the inner periphery with a certain depth, have a predetermined interval in the circumferential direction, and extend in the axial direction. The rotor bars 5 are exposed from the slits 6 formed on the outer periphery of the rotor 1, and have a so-called open slot structure.

[0023] Rotor bars 5 are arranged in each of the rotor slots 5a, and at the axial end faces of the rotor 1, the rotor bars 5 are connected by an annular end ring 3 and are short-circuited.

[0024] The above-described rotor bars 5 are formed by pouring a die-cast material into the rotor slots 5a, and the rotor 1 is a die-cast rotor provided with the rotor bars 5 as described above.

[0025] Next, we will explain the configuration of a conventional electric motor shown in Figures 2(a) and 2(b), which are enlarged cross-sectional views of region A in Figure 1, and the configuration of the electric motor 20 of this embodiment shown in Figures 3(a) and 3(b).

[0026] Figure 2(a) is an enlarged cross-sectional view showing the end of the end ring 3 in a conventional electric motor configuration, and Figure 2(b) is a cross-sectional view showing the slit 10 of the end ring 3 as seen from the direction of arrow C in Figure 2(a).

[0027] Figure 3(a) is an enlarged cross-sectional view showing the end of the end ring 3 in the configuration of the electric motor 20 of this embodiment, and Figure 3(b) is a cross-sectional view showing the slit 11 of the end ring 3 as seen from the direction of arrow D in Figure 3(a).

[0028] As shown in Figures 2(a) and 3(a), the stator coils 9 are discretely arranged circumferentially within the stator 2, with a portion of them protruding axially from the stator 2. The end ring 3 rotates between this protruding portion of the stator coil 9 (coil end 9a) and the rotation axis 4 (radially).

[0029] The end ring 3 in this embodiment, shown in Figure 3(a), has a forward tapered structure in which the distance between the end ring 3 and the coil end 9a of the stator 2 gradually widens towards the axial end. By adopting a forward tapered structure for the end ring 3, the space between the end ring 3 and the end of the stator coil 9 (between the end ring 3 and the coil end 9a) is expanded, generating airflow along the end ring 3 and increasing the amount of air flowing into the gap between the rotor 1 and the stator 2.

[0030] Furthermore, in a conventional electric motor configuration as shown in Figure 2(a), where the slit 10 is simply cut to the end, when operating at high speeds such as in railway vehicle motors, the generation of air resistance on the outer wall of the slit 10 due to the opposing wind, and the resulting concentration of stress, become major problems.

[0031] However, as shown in the configuration of the electric motor 20 in this embodiment in Figure 3(a), by making the slit 11 on the extension of the forward tapered structure formed in the end ring 3 also a forward tapered structure, the length of the slit 11 in the end ring 3 and the area of ​​the outer wall of the slit 11 are reduced compared to the case where the end ring 3 does not have a forward tapered structure as shown in Figure 2(a). This reduces the influence of the opposing wind, thereby minimizing the generation of air resistance and stress.

[0032] Furthermore, in the electric motor 20 of this embodiment, the rotor bars 5 in the rotor slot 5a on the outer circumference of the rotor 1 are formed in one piece by die casting. However, as shown in Figure 5(c), the circumferential dimension (L1) of the slit 15 is narrower than the width (circumferential dimension L3) of the rotor bar 5, and the side walls of the slit 15 are processed so that the side surface (laminated surface) of the electromagnetic steel sheet is exposed.

[0033] As will be explained later, this is due to machining a slit 15 with a width (L1) wider than the width (L2) of the opening 5c ​​(see Figure 5) of the rotor slot 5a before machining.

[0034] In the case of electric motors that require inverse current drive at high frequencies, such as those used in vehicles, the skin effect causes high-frequency alternating currents to concentrate on the surface.

[0035] Therefore, as shown in Figures 4(a), (b), and (c), if the slit 15 is formed with the same dimensions (L1) as the opening 5b formed in the rotor slot 5a, some of the die-cast material poured into the rotor slot 5a will remain on the side wall of the slit 15. Due to the skin effect, current will flow through the remaining die-cast material, causing excessive losses in that area and degrading the temperature characteristics of the motor.

[0036] Therefore, in this embodiment, as shown in Figures 5(a), (b), and (c), the slit 15 is cut with a width (L1) wider than the width (L2) of the opening 5c ​​of the rotor slot 5 before processing, so that the die-cast material does not remain on the side of the slit 15, and the laminated structure of the electromagnetic steel sheet of the rotor 1 is exposed. As a result, the die-cast material does not remain on the side wall of the slit 15, and no current flows through the die-cast material, so excessive losses do not occur, and there is no risk of deterioration of the temperature characteristics of the electric motor 20.

[0037] Furthermore, as shown in Figure 5(c), the slit 15 is machined such that the depth of the slit groove to the exposed portion of the rotor bar 5 is greater than the depth of the slit groove to the non-exposed portion of the rotor bar 5. In other words, the slit 15 is machined such that the distance (L4) from the slit 15 to the exposed portion of the rotor bar 5 is greater (deeper) than the distance (L5) to the non-exposed portion of the rotor bar 5.

[0038] As will be explained later, this is due to increasing the feed rate of the tool used for machining to cut even deeper than the depth of the slit 15.

[0039] In this way, by providing a slit groove whose depth to the exposed portion of the rotor bar 5 is greater than the depth to the non-exposed portion of the rotor bar 5, the cross-sectional area of ​​the flow path of the slit 15 is increased, which increases the airflow rate and improves the heat dissipation efficiency as the surface area of ​​the slit 15 increases.

[0040] Furthermore, since the grooves extending from the slit 6 continue all the way to the end ring 3, a ventilation passage is also formed in the end ring 3, making it possible to significantly improve the amount of airflow.

[0041] Next, the method for forming the slits in the rotor slot 5a of this embodiment will be described.

[0042] The method for forming the slits in the rotor slot 5a in this embodiment is a die-cast rotor in which a plurality of rotor bars 5 of the rotor 1, which is formed by laminating electromagnetic steel sheets, are formed at predetermined intervals in the circumferential direction, and die-cast material is poured into the rotor slot 5a which extends in the axial direction. The rotor slot 5a is an open slot in which the rotor bars 5 are exposed through slits 15 formed on its outer circumference. In creating the slits 15 on the outer circumference of the rotor slot 5a, a rotor slot 5a with an opening 5c ​​is created, then die-cast material is poured into the rotor slot 5a to form the rotor bars 5, the outer circumference of the rotor 1 is cut, and then the opening 5c ​​is cut with a circumferential dimension (L1) wider than the circumferential dimension (L2) of the opening 5c ​​to create the slits 15 on the outer circumference of the rotor slot 5a.

[0043] The method for forming the slits in the rotor slot 5a of this embodiment will be explained below using Figures 5(a), 5(b), and 5(c), in comparison with the conventional method for forming the slits in the rotor slot 5a shown in Figures 4(a), 5(b), and 5(c).

[0044] Figures 4(a), (b), and (c) show a conventional method for creating slits in a rotor slot 5a, in which die-cast material remains in the opening 5b. Each step shows the dotted line B in Figure 2(a) as viewed from the end ring 3 side.

[0045] First, as shown in Figure 4(a), a rotor slot 5a is created with an opening 5b of circumferential dimension (L1) at the top. Then, as shown in Figure 4(b), die-cast material 13 is poured into the rotor slot 5a to form a rotor bar 5. Finally, as shown in Figure 4(c), the outer circumference 14 of the rotor is machined, and a slit 15 of circumferential dimension (L1) is created to match the circumferential dimension (L1) of the opening 5b.

[0046] As with conventional slit creation methods, creating the slit 15 to match the circumferential dimension (L1) of the opening 5b can cause a small amount of die-cast material to remain in the opening 5b.

[0047] Figures 5(a), (b), and (c) show the method for forming the slits in the rotor slot 5a of this embodiment, in which no die-cast material remains in the opening 5c, and each step shows the dotted line B in Figure 3(a) as seen from the end ring 3 side.

[0048] First, as shown in Figure 5(a), a rotor slot 5a is created with an opening 5c ​​of circumferential dimension (L2) at the top. Then, as shown in Figure 5(b), die-cast material 13 is poured into the rotor slot 5a to form a rotor bar 5. After cutting the outer circumference 14 of the rotor as shown in Figure 5(c), the opening 5c ​​is cut wider than the circumferential dimension (L2) of the opening 5c ​​to create a slit 15 of circumferential dimension (L1).

[0049] In this embodiment, where the slit 15 is formed by cutting with a circumferential dimension (L1) wider than the opening 5c, there is no residue of the die-cast material 13 on the surface of the opening 5c. Therefore, it is possible to suppress the occurrence of excessive losses that may be caused by the concentration of alternating current due to the skin effect.

[0050] Therefore, according to this embodiment, even when using a die-cast rotor, it is possible to obtain an electric motor 20 in which the heat dissipation characteristics of the rotor 1 are improved and the temperature characteristics do not deteriorate, and a method for forming slits in the rotor slot 5a can be obtained that can suppress the occurrence of excessive losses that may occur due to the concentration of AC current due to the skin effect.

[0051] It should be noted that the present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of Symbols]

[0052] 1...Rotor, 2...Stator, 3...End ring, 4...Rotating shaft, 5...Rotor bar, 5a...Rotor slot, 5b, 5c...Opening of rotor slot, 6, 15...Slit, 7...Casing, 8...Bearing, 9...Stator coil, 9a...Coil end, 10...Slit of conventional end ring, 11...Slit of end ring in this embodiment, 13...Die-cast material, 14...Outer circumference of rotor, 20...Electric motor.

Claims

1. It comprises a rotor formed by laminating electrical steel sheets, and a stator arranged on the outer circumference of the rotor, The rotor is a die-cast rotor formed by pouring die-cast material into rotor slots that are formed by multiple rotor bars at predetermined intervals in the circumferential direction and extending in the axial direction. The rotor slot is an open slot through which the rotor bar is exposed from a slit formed on its outer circumference. The circumferential width of the slit is narrower than the circumferential width of the rotor bar, the side wall of the slit exposes the side surface (laminated surface) of the electrical steel sheet, and the slit is a groove in which the depth to the exposed portion of the rotor bar is greater than the depth to the non-exposed portion of the rotor bar. A rotating electric machine characterized by having end rings at both axial ends of the rotor, and grooves extending from the slits also being formed in the end rings.

2. A rotating electric machine according to claim 1, The rotating electric machine is characterized in that the end ring has a forward taper structure in which the distance between the end ring and the coil end of the stator gradually widens towards the axial end.

3. A rotating electric machine according to claim 2, A rotating electric machine characterized in that the slit, which is an extension of the forward tapered structure formed in the end ring, also has a forward tapered structure.

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