Rotating electrical machine

Abstract

Provided is a rotating electrical machine in which deformation and fatigue in split cores are reduced by relaxing press-fitting stress during assembly and thermal stress during operation, whereby driving performance and reliability can be improved while ensuring assemblability of the split cores. The rotating electrical machine comprises: a substantially cylindrical stator; and a rotor concentrically disposed inside the stator. The rotor comprises: a substantially cylindrical fixing member; a plurality of split cores fixed to the outer circumferential surface of the fixing member at substantially equal intervals as viewed in the axial direction; and circumferential magnetization magnets disposed in the portions between the plurality of split cores. The fixing member has, on the outer circumferential surface, a plurality of trapezoidal fastening recesses having long edges on the rotation axis side as viewed in the axial direction. The split cores have teeth for holding the circumferential magnetized magnets on the outside in the radial direction, and have, on the inside in the radial direction, trapezoidal fastening protrusions having long edges on the rotation axis side as viewed in the axial direction. Foamable materials are disposed in the portions between the edges on the rotation axis side of the fastening protrusions and the fixing member, and the fastening protrusions protrude to the outside of the fastening recesses by a prescribed radial distance δr.

Description

Rotating electrical machine

[0001] The present invention relates to a rotating electrical machine mounted in automobiles, trucks, buses, construction machines, railway vehicles, elevators, home appliances, and the like.

[0002] In order to improve the material utilization rate of the core used in a rotating electrical machine, split cores have been utilized more than before. Also, in the permanent magnet type rotating electrical machine of Patent Document 1, by using a split core for the rotor and providing a gap portion on the radially outer side of the magnet, leakage magnetic flux of the magnet is reduced, and an increase in effective magnetic flux and an increase in torque are achieved. Thus, in conventional rotating electrical machines, by utilizing split cores, improvement in material utilization rate and reduction of leakage magnetic flux of magnets have been achieved. [[ID=⑧]]

[0003] Japanese Unexamined Patent Application Publication No. 2015 - 115986

[0004] However, the split core in a conventional rotating electrical machine had a problem that since it had to be press-fitted using an extrusion device when fastening to a fixed member, the introduction of the device increased the equipment cost. Also, when press-fitting by the extrusion device, the split core deformed, and the roundness of the gap between the rotor and the stator after press-fitting decreased, resulting in problems such as a decrease in torque and an increase in vibration and noise. Furthermore, there was a problem that stress concentration occurred in the press-fitted portion, making the split core prone to deformation and breakage. In particular, in applications such as automobiles where the operating temperature of the rotating electrical machine becomes high, when the fixed member of the split core thermally expands during operation, the thermal stress repeatedly generated in the press-fitted portion is superimposed on the stress applied during press-fitting, resulting in excessive stress concentration and making the core prone to breakage.

[0005] Therefore, an object of the present invention is to provide a rotating electrical machine capable of improving drive performance and reliability by reducing deformation and fatigue of the split core by alleviating press-fitting stress during assembly and thermal stress during operation while ensuring the assemblability of the split core.

[0006] To achieve the above objective, the present invention includes various embodiments, but one example is a rotating electric machine comprising a substantially cylindrical stator and a rotor concentrically arranged inside the stator, wherein the rotor comprises a substantially cylindrical fixed member, a plurality of segmented cores fixed to the outer circumferential surface of the fixed member at substantially equal intervals in an axial view, and circumferentially magnetized magnets arranged between the plurality of segmented cores, wherein the fixed member has a plurality of trapezoidal fastening recesses on its outer circumferential surface, with the side on the rotation axis side being longer in an axial view, and the segmented cores have teeth on the radially outward side for holding the circumferentially magnetized magnets and trapezoidal fastening protrusions on the radially inward side, with the side on the rotation axis side being longer in an axial view, and a foamed material is placed between the side of the fastening protrusion on the rotation axis side and the fixed member, and the fastening protrusion protrudes to the outside of the fastening recess by a predetermined radial distance δr.

[0007] According to the rotating electric machine of the present invention, while ensuring the ease of assembly of the segmented core, it is possible to reduce deformation and fatigue of the segmented core by mitigating press-fitting stress during assembly and thermal stress during operation, thereby improving drive performance and reliability.

[0008] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments.

[0009] Diagram illustrating the overall structure of the rotating electric machine in Example 1 Diagram illustrating the fastening structure of the divided core in Example 1 (before foaming) Diagram illustrating the fastening structure of the divided core in Example 1 (after foaming) Diagram illustrating the separation distance of the divided core structure after foaming in Example 1 Diagram illustrating the overall structure of the rotating electric machine in Example 2 Diagram illustrating the fastening structure of the divided core in Example 2 (before foaming) Diagram illustrating the fastening structure of the divided core in Example 2 (after foaming) Diagram illustrating the fastening structure of the divided core in a modified example of Example 2 (before foaming) Diagram illustrating the fastening structure of the divided core in a modified example of Example 2 (after foaming) Diagram illustrating the overall structure of the rotating electric machine in Example 3 Diagram illustrating the conventional fastening structure of the divided core Diagram illustrating the conventional fastening structure of the divided core Diagram illustrating the conventional fastening structure of the divided core

[0010] Embodiments of the present invention will be described below with reference to the drawings. In the following description, identical components are denoted by the same symbols. Their names and functions are the same, and redundant explanations will be avoided. Furthermore, although the following description focuses on an inner rotor type rotating electric machine, the effects of the present invention are not limited to this and can also be applied to an outer rotor type rotating electric machine. Also, the combination of the number of poles and the number of slots is just one example, and the present invention can be applied to other combinations as well. Furthermore, although the following description focuses on a rotor structure in which permanent magnets magnetized in the circumferential direction are arranged in a spoke-like manner, this is just one example, and the present invention can also be applied to rotor structures having other permanent magnet arrangements.

[0011] Hereinafter, an embodiment 1 of the rotating electric machine of the present invention will be described with reference to Figures 1 to 3.

[0012] Figure 1 is an explanatory diagram of the overall structure of the rotating electric machine 1 in this embodiment, viewed from the direction of the rotation axis. As shown here, the rotating electric machine 1 comprises a substantially cylindrical stator 10 and a rotor 20 concentrically arranged inside it with a gap 30 in between. In the following explanation, the direction parallel to the rotation axis of the rotor 20 is defined as the "axial direction," the diametrical direction of the rotor 20 perpendicular to the rotation axis is defined as the "radial direction," and the circumferential direction centered on the rotation axis is defined as the "circumferential direction."

[0013] The stator 10 has a stator core 11 with multiple teeth 11a and a coil (not shown) wound around each tooth 11a. A slot 11b, which is a space for winding the coil, is formed between adjacent teeth 11a. In the stator 10 illustrated in Figure 1, there are 12 slots.

[0014] The rotor 20 has a structure in which a segmented core 21 fixed to the outer circumferential surface of a substantially cylindrical fixed member 40 and permanent magnets 22 magnetized in the circumferential direction are arranged alternately in the circumferential direction. As a result, the permanent magnets 22 arranged in a spoke-like manner and the segmented core 21 sandwiched between them constitute either a north pole or a south pole. In the rotor 20 illustrated in Figure 1, the number of poles is 10.

[0015] Figures 2A and 2B are explanatory diagrams of the fastening structure between the divided core 21 and the fixing member 40. Figure 2A shows the foamed material 50 before foaming, and Figure 2B shows the state after foaming. As shown here, the divided core 21 has a fastening projection 21a, a hypotenuse 21b, a projection starting point 21c, teeth 21d, and an overhang 21e, and the fixing member 40 has an outer peripheral surface 41 and a fastening recess 42. The foamed material 50 is also placed on one surface of the divided core 21. Each of these will be described in turn below.

[0016] <Teeth 21d, protruding portion 21e> As shown in Figure 1, each permanent magnet 22 is held within a space enclosed by a pair of divided cores 21 and a fixing member 40. The teeth 21d and protruding portion 21e of the divided core 21 are used to hold the magnets. That is, even when the rotating electric machine 1 is in operation, the circumferential position of the permanent magnet 22 is held in a predetermined position by the pair of teeth 21d, and the radial position of the permanent magnet 22 is held in a predetermined position by the pair of protruding portions 21e.

[0017] <Fastening projection 21a, fastening recess 42, foamed material 50> As shown in Figure 1, fastening recesses 42 are provided on the outer circumferential surface 41 of the fixing member 40 at approximately equal intervals in the circumferential direction when viewed in the axial direction, in order to fix the divided core 21 to the fixing member 40.

[0018] Furthermore, as shown in Figures 2A and 2B, each segmented core 21 is provided with a fastening projection 21a on the end face facing the fixing member 40, which fits into the fastening recess 42. Since this fastening projection 21a has a substantially trapezoidal cross-sectional shape with the side on the rotation axis side being longer in an axial view, the fastening recess 42 that fits into it has a substantially trapezoidal cross-sectional shape with the side on the rotation axis side being longer in an axial view. In addition, a foamed material 50 is arranged on the rotation axis side surface of the fastening projection 21a so as to face the inner surface of the fastening recess 42.

[0019] Thus, although the fastening projection 21a and the fastening recess 42 have similar cross-sectional shapes in an axial view, as shown in Figure 2A, the fastening recess 42 is slightly larger than the fastening projection 21a with the foamed material 50 attached. Therefore, the fastening projection 21a with the foamed material 50 attached can be easily slid into the fastening recess 42 from the axial direction.

[0020] The foaming material 50 is a material whose thickness increases when heated due to the expansion of foaming components, and is, for example, epoxy resin. In Figure 2A, a configuration in which the foaming material 50 is applied to the divided core 21 is shown as an example, but the foaming material 50 processed into a sheet shape may be attached to the divided core 21 or the fastening recess 42 of the fixing member 40, or the foaming material 50 may be arranged by other methods.

[0021] <Hypotenuse 21b, Protrusion Starting Point 21c> The hypotenuse 21b is the circumferential side surface of the fastening protrusion 21a. The protrusion starting point 21c is the boundary point (actually a straight line) between the teeth 21d and the fastening protrusion 21a. As is obvious from Figures 2A and 2B, there is one pair of hypotenuse 21b and protrusion starting point 21c for each divided core 21.

[0022] <Foaming action of foaming material 50> In the state shown in Figure 2A (before foaming of foaming material 50), the foaming material 50 is thin, so there is a sufficient gap between the fastening projection 21a and the fastening recess 42, and the fastening projection 21a can slide freely within the fastening recess 42. On the other hand, in the state shown in Figure 2B (after foaming of foaming material 50), the foaming material 50 has become thicker, and the fastening projection 21a and the fastening recess 42 are fitted together. The mechanism by which the state changes from Figure 2A to Figure 2B will be explained below.

[0023] When the foamed material 50 in Figure 2A is heated, the thickness dimension (radial dimension) of the foamed material 50 increases, as shown in Figure 2B. As a result, the divided core 21 is pushed radially outward, and the slanted side 21b of the fastening projection 21a comes into contact with the inner surface of the fastening recess 42 of the fixing member 40. The frictional force resulting from this contact fixes the divided core 21 to the fixing member 40. At this time, the slanted side 21b of the fastening projection 21a protrudes outside the fastening recess 42 by a predetermined radial distance δr.

[0024] As shown in Figure 3, the magnitude of the radial distance δr can be expressed by the following equation, using the circumferential width Wc between the starting points 21c of the protrusions of the divided core 21, the opening width Wh of the fastening recess 42 on the outer circumferential surface 41 of the fixing member 40, and the angle θ between the hypotenuse 21b of the fastening protrusion 21a and the outer circumferential surface 41.

[0025] δr = (Wh - Wc) / 2 × tanθ Furthermore, in the foamed state shown in Figure 2B, the segmented cores 21 may be further fixed to the fixing member 40 using resin or adhesive. This ensures that the fixation of the segmented cores 21 can be maintained even if the foamed material 50 deteriorates over time.

[0026] <Comparison with Prior Art> The principle of the present invention will be explained below in comparison with the prior art.

[0027] Figures 8A to 8C are explanatory diagrams of a conventional split core fastening structure. As shown in each figure, the conventional split core fastening structure, like this embodiment, utilizes the fastening projection 21a of the split core 21 and the fastening recess 42 of the fixing member 40. However, in this embodiment, an extrusion device is not required when inserting the split core 21 (see the large gap around the fastening projection 21a in Figure 2A), whereas in the prior art, an extrusion device is required to press-fit the split core 21 into the fixing member 40.

[0028] Thus, the conventional structure requires an extrusion device, which increases equipment costs. Also, as shown in Figure 8B, the divided core 21 undergoes deformation as shown in the deformed portion 21g during press-fitting. This deformation reduces the roundness of the gap surface 21f of the divided core 21 after fastening, leading to a decrease in torque and an increase in vibration and noise. Furthermore, the fastening projection 21a generates a stress concentration area 21h during press-fitting, making it prone to deformation and breakage. In particular, in automotive applications where the operating temperature of the rotating electric machine 1 is high, as shown in Figure 8C, the fixing member 40 undergoes thermal expansion during operation, generating repeated thermal stress 21i in the stress concentration area 21h and deformed portion 21g of the fastening projection 21a. This thermal stress 21i is superimposed on the stress applied during press-fitting, resulting in excessive repeated stress and making the divided core 21 prone to breakage.

[0029] In contrast, in the split core fastening structure of this embodiment, as shown in Figure 2A, a sufficient gap (clearance) is secured between the fastening projection 21a of the split core 21 and the recess 42 of the fixing member 40 in the pre-foaming state, thus eliminating the need for an extrusion device for press-fitting. This avoids an increase in equipment costs. Furthermore, since press-fitting is not required, deformation of the split core 21 can be avoided. As a result, the roundness of the gap surface does not decrease, and a decrease in torque and an increase in vibration and noise can be avoided. Moreover, although the fastening projection 21a is subjected to the expansion force of the foamable material 50 after foaming, this expansion force is only a few MPa, which is negligible compared to the stress generated by press-fitting (hundreds of MPa if deformation occurs), so it does not cause deformation or breakage. In addition, when the fixing member 40 expands due to thermal expansion during operation, the outer circumferential surface 41 of the fixing member 40 expands radially, but there is a gap 60 with a radial distance δr between the split core 21 and the outer circumferential surface 41. In other words, since the thermal expansion of the fixing member 40 is absorbed by the gap 60, it is possible to avoid a situation in which excessive thermal stress is repeatedly generated in the divided core 21.

[0030] Furthermore, the segmented core fastening structure of this embodiment facilitates recycling. In conventional segmented core structures, the segmented core 21 and the fixing member 40 are fastened by press-fitting, requiring the use of a powerful extrusion device for disassembly, which increases recycling costs. In contrast, in this embodiment, if the rotor 20 can be recovered in the state shown in Figure 2B, the expansion force of the foamed material 50 can be removed by removing the foamed material 50 with a machine tool or the like. That is, it is possible to return to a state where sufficient clearance is secured between the fastening protrusion 21a of the segmented core 21 and the recess 42 of the fixing member 40, making disassembly easy. Even if the foamed material 50 is not removed, the expansion force of the foamed material 50 is relatively small, so the segmented core 21 can be removed from the fixing member 40 even with a relatively simple extrusion device.

[0031] Furthermore, from the viewpoint of driving performance, it is preferable that the radial distance δr of the gap 60 after foaming, as shown in Figure 2B, be small. This is because the divided core 21 functions as a passage for magnetic flux, while the gap 60 becomes a dead space through which magnetic flux does not pass. On the other hand, as shown in Figure 2A, it is desirable to provide a predetermined clearance between the foaming material 50 and the fastening recess 42 of the fixing member 40 during assembly. Therefore, in order to achieve both ease of assembly and driving performance, it is desirable to configure the radial distance δr of the gap 60 to satisfy the following relationship with respect to the radial thickness δb of the foaming material 50 after foaming, as shown in Figure 2B.

[0032] 0 < δr < δb As described above, the segmented core fastening structure of this embodiment ensures the ease of assembly of the segmented core while mitigating press-fit stress during assembly and thermal stress during operation, thereby reducing deformation and fatigue of the segmented core and providing a rotating electric machine that can improve driving performance and reliability.

[0033] Next, an embodiment 2 of the rotating electric machine of the present invention will be described using Figures 4 to 6B. Note that common points with the above embodiment will be omitted from the explanation.

[0034] Figure 4 is an explanatory diagram of the overall structure of the rotating electric machine 1 in this embodiment. Figures 5A and 5B are explanatory diagrams of the split core fastening structure in this embodiment, with Figure 5A showing the foamable material 50 before foaming and Figure 5B showing the state after foaming.

[0035] As shown in Figures 5A and 5B, the first difference from Embodiment 1 is that the intersection of the hypotenuse 21b of the fastening projection 21a and the side surface (extension of the circumferential surface) of the teeth 21d is set as the projection starting point 21c of the divided core 21. In other words, the divided core 21 is formed such that the angle between the two sides extending radially inward and outward from the projection starting point 21c is obtuse. The second difference from Embodiment 1 is that the opening end of the outer peripheral surface 41 is cut off.

[0036] With this configuration, even if the fixed member 40 expands due to thermal expansion when the rotating electric machine 1 is driven, causing the outer peripheral surface 41 to expand radially, the possibility of the opening end of the outer peripheral surface 41 contacting the divided core 21 is reduced compared to the structure of Embodiment 1 shown in Figure 2B, etc., and the situation in which excessive thermal stress is repeatedly generated in the divided core 21 can be reliably avoided.

[0037] <Modified Version> Figures 6A and 6B are explanatory diagrams of the segmented core fastening structure in a modified version of this embodiment, with Figure 6A showing the foamed material 50 before foaming and Figure 6B showing the state after foaming. As shown in Figure 6A, in this modified version, by providing an arc-shaped recess at the starting point 21c of the protrusion, it becomes easier to avoid interference with the fastening protrusion 21a during assembly, even when the opening width Wh of the fastening recess 42 on the outer peripheral surface 41 becomes smaller due to manufacturing variations.

[0038] In this case, the starting point of the protrusion 21c is defined as the intersection of the extension of the hypotenuse 21b of the fastening protrusion 21a and the extension of the circumferential surface of the teeth 21d. Furthermore, the radial distance δr of the gap 60 after foaming refers to the radial distance between the starting point of the protrusion 21c and the outer circumferential surface 41, as shown in Figure 6B.

[0039] Next, an embodiment 3 of the rotating electric machine of the present invention will be described using Figure 7. Note that common points with the above embodiments will be omitted from the explanation.

[0040] Figure 7 is an explanatory diagram of the overall structure of the rotating electric machine 1 in this embodiment. The difference from Embodiment 2 is that permanent magnets 23 having radial magnetization are embedded in the divided core 21. This configuration increases the amount of magnetic flux, thereby further improving the driving performance.

[0041] In the above embodiment, the divided core 21 was fixed to the fixing member 40 by utilizing the expansion force of the foamed material 50 placed on one surface of the divided core 21. However, a similar effect may be used to fix the permanent magnets 22 and 23. That is, permanent magnets 22 and 23, each having foamed material 50 on one surface, may be inserted into a space slightly larger than the permanent magnets 22 and 23, and then heated to cause the foamed material 50 to foam. The resulting expansion force can then be used to fix the permanent magnets 22 and 23 in the desired position.

[0042] 1: Rotating electric machine, 10: Stator, 11: Stator core, 11a: Teeth, 11b: Slot, 20: Rotor, 21: Rotor split core, 21a: Fastening projection, 21b: Hypotenuse, 21c: Starting point of projection, 21d: Teeth, 21e: Overhang, 21f: Gap surface, 21g: Deformed part, 21h: Stress concentration area, 21i: Thermal stress, 22: Permanent magnet (circumferential magnetization), 23: Permanent magnet (radial magnetization), 30: Gap, 40: Fixing member, 41: Outer surface, 42: Fastening recess, 50: Foaming material, 60: Gap

Claims

1. A rotating electric machine comprising a substantially cylindrical stator and a rotor concentrically arranged inside the stator, wherein the rotor comprises a substantially cylindrical fixed member, a plurality of segmented cores fixed to the outer circumferential surface of the fixed member at substantially equal intervals in an axial view, and circumferentially magnetized magnets arranged between the plurality of segmented cores, wherein the fixed member has a plurality of trapezoidal fastening recesses on its outer circumferential surface, with the side on the rotation axis side being longer in an axial view, the segmented cores have teeth on the radially outward side for holding the circumferentially magnetized magnets and trapezoidal fastening protrusions on the radially inward side, with the side on the rotation axis side being longer in an axial view, a foamed material is arranged between the side of the fastening protrusion on the rotation axis side and the fixed member, and the fastening protrusion protrudes to the outside of the fastening recess by a predetermined radial distance δr.

2. The rotating electric machine according to claim 1, characterized in that radially magnetized magnets are embedded in the divided core.

3. The rotating electric machine according to claim 2, characterized in that a foaming material is arranged on one surface of the circumferential magnet and the radial magnet.

4. The rotating electric machine according to claim 1, wherein the radial distance δr is expressed by the following formula, using the circumferential width Wc between the starting points of the convex portions which are the boundary between the teeth and the fastening convex portions, the opening width Wh of the fastening recess on the outer circumferential surface of the fixing member, and the angle θ between the hypotenuse of the fastening convex portion and the outer circumferential surface of the fixing member: δr = (Wh - Wc) / 2 × tanθ 5. The rotating electric machine according to claim 4, characterized in that the angle between the two sides extending from the starting point of the protrusion is an obtuse angle.

6. The rotating electric machine according to claim 4, characterized in that an arc-shaped recess is provided at the starting point of the convex portion.

7. The rotating electric machine according to claim 1, characterized in that the relationship between the thickness δb of the foamed material after foaming and the radial distance δr is expressed by the following equation: 0 < δr < δb 8. A rotating electric machine according to claim 1, characterized in that, after foaming of the foaming material, part or all of the rotor is fixed with resin.

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