Rotating electric machines

Abstract

To provide a rotating electric machine capable of suppressing loosening of fastening members due to thermal stress without impairing costs or fixing reliability. [Solution] The rotating electric machine comprises a stator core made of laminated electromagnetic steel plates with an insulating layer on the surface, a case made of a material with a higher linear expansion coefficient than the stator core, which houses the stator core, and a fastening member that fastens the stator core to a female threaded portion provided in the case, and a countersink of C0.5 mm or more is provided at the mouth of the female threaded portion so that the fastening member cannot fit into it.

Description

[Technical Field]

[0001] The present disclosure relates to a rotating electric machine. [Background technology]

[0002] Patent Document 1 discloses a structure in which an indirect member is embedded in a female threaded portion of a case, and a stator is fastened and fixed to the case via the indirect member, thereby preventing loosening of the fastening member due to thermal stress. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-080958 Summary of the Invention [Problem to be solved by the invention]

[0004] In the structure disclosed in Patent Document 1, the cost of the indirect member is high, and the stator seating surface is only the upper surface of the indirect member, which poses a problem in terms of fixing reliability.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a rotating electric machine that can suppress loosening of fastening members due to thermal stress without compromising costs or fixing reliability. [Means for solving the problem]

[0006] The rotating electric machine of the present disclosure comprises a stator core formed by laminating electromagnetic steel plates having an insulating layer on the surface, a case made of a material having a higher linear expansion coefficient than the stator core and accommodating the stator core, and a fastening member for fastening the stator core to a female threaded portion provided in the case, and a countersink of C0.5 mm or more is provided at the mouth of the female threaded portion so that the fastening member does not fit into it. [Effects of the Invention]

[0007] According to the present disclosure, by simulating the linear expansion change of a stator core with a long axial length using a stator core with a short axial length, it is possible to suppress loosening of fastening members due to thermal stress without compromising costs or fixing reliability. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing the configuration of a rotating electric machine according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing a case of the rotating electrical machine according to the embodiment. [Figure 3] FIG. 3 is a plan view showing the configuration of the rotating electric machine according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the configuration of the rotating electric machine according to the embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing an example of a rotating electrical machine in which a stator having a long axis is fastened and fixed by fastening members having a long axis. [Figure 6] FIG. 6 is a cross-sectional view showing an example of a rotating electrical machine in which a stator having a short axial length is fastened and fixed by fastening members having a short axial length. [Figure 7] FIG. 7 is a graph showing the relationship between the amount of change in linear expansion of the stator core and the case and the depth of the counterbore. [Figure 8] FIG. 8 is a cross-sectional view showing the configuration of a modified example of the rotating electric machine according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A rotating electric machine according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same.

[0010] A rotating electric machine according to an embodiment will be described with reference to FIGS. 1 to 4. The rotating electric machine according to an embodiment is used, for example, as a power source for a vehicle. The rotating electric machine according to an embodiment is mounted, for example, in a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like. The rotating electric machine according to an embodiment may also be mounted, for example, in a fuel cell electric vehicle (FCEV), a battery electric vehicle (BEV), or the like.

[0011] As shown in FIGS. 1 to 4, the rotating electrical machine 1 includes a stator core 11, a case 12, and fastening members 13.

[0012] Stator core 11 is made by laminating electromagnetic steel sheets having insulating layers on their surfaces. As shown in Fig. 4, stator core 11 is provided with through holes 111 into which fastening members 13 are inserted. In addition, slots into which coils (not shown) are attached are provided on the inner periphery of stator core 11.

[0013] Case 12 is for housing stator core 11. Case 12 is made of a material having a larger linear expansion coefficient than stator core 11, such as aluminum. Also, case 12 is provided with a female thread portion 121 for fastening fastening member 13, as shown in FIG. 2 .

[0014] The fastening member 13 is used to fasten and fix the stator core 11 to a female thread portion 121 provided in the case 12 .

[0015] Here, the stator core 11 and the case 12, which are fixed by the fastening members 13, are made of materials with different linear expansion coefficients, and the material (aluminum) that makes up the case 12 has a larger linear expansion coefficient than the material (iron) that makes up the stator core 11. Therefore, when the temperature of the rotating electric machine 1 changes from room temperature to a high temperature, the difference in linear expansion between the stator core 11 and the case 12 causes a force to act on the fastening members 13 that are fastened to the case 12, tending to move them radially outward of the rotating electric machine 1.

[0016] Meanwhile, a frictional force (a force that tries to hold the fastening member 13 in place) acts on the bearing surface (the surface that comes into contact with the stator core 11). The balance between these two forces determines whether the interface between the bearing surface of the fastening member 13 and the stator core 11 will slip, i.e., whether the fastening member 13 will loosen. The frictional force acting on the bearing surface of the fastening member 13 is determined by "frictional force = friction coefficient x axial force." However, the longer the axial length of the stator core 11, the greater the thermal expansion of the length fastened by the fastening member 13, and therefore the greater the axial force and the greater the frictional force. Therefore, the longer the axial length of the stator core 11, the less likely it is that the interface between the bearing surface of the fastening member 13 and the stator core 11 will slip (the more unlikely the fastening member 13 will loosen).

[0017] 5 shows an example of a rotating electric machine 101 in which a stator core 11A having a long axial length is fastened and fixed by fastening members 13 having a long axial length (for example, 76 mm). In the case of a stator core 11A having a long axial length, the fastening members 13 are accordingly long (the fastened length is long).

[0018] In the rotating electric machine 101, the axial force of the fastening member 13 also changes in response to temperature changes, but the frictional force acting on the seating surface of the fastening member 13 increases, making the fastening member 13 less likely to loosen. Furthermore, in the case of the stator core 11A having a long axial length, the amount of thermal deformation of the fastening member 13 is smaller than the amount of thermal deformation of the case 12, so the fastening member 13 deforms toward the center of the stator core 11A at high temperatures. This prevents slippage between the fastening member 13 and the stator core 11A.

[0019] 6 shows an example of a rotating electric machine 102 in which a stator core 11 having a short axial length similar to that of this embodiment is fastened and fixed by fastening members 13 having a short axial length (for example, 50.5 mm). In the case of a stator core 11 having a short axial length, the axial force of the fastening members 13 exhibits unstable behavior in which it suddenly decreases when the temperature rises, which causes the fastening members 13 to loosen.

[0020] When the axial length of stator core 11 is short, fastening members 13 are shorter and the amount of deformation due to bending is smaller than when the axial length is long. Therefore, when the temperature changes from room temperature to a high temperature, slippage occurs between fastening members 13 and stator core 11, reducing the axial force. Furthermore, in the case of stator core 11 with a short axial length, the amount of thermal deformation of fastening members 13 is equivalent to the amount of thermal deformation of case 12, so slippage between fastening members 13 and stator core 11 is not hindered.

[0021] Therefore, in the rotating electric machine 1, as shown in Fig. 4, in order to suppress a decrease in the axial force of the fastening member 13 of the stator core 11 having a short axial length, a counterbore 122 of C0.5 mm or more (preferably C1.0 mm or more) is provided at the mouth of the female thread portion 121 of the case 12, so that the fastening member 13 will not fit in. This ensures that even in the case of a short axial length like the stator core 11, the axial length is equivalent to that in the case of a long axial length (see Fig. 5).

[0022] Unlike the female thread portion 121, the countersunk portion 122 is not threaded on the inside. A threaded surface (female thread portion 121) is provided below the countersunk portion 122, thereby extending the length of the fastening member 13 and fixing it in place.

[0023] The above-mentioned "axial length equivalent to that when the axial length is long" means that "axial length of stator core 11 plus depth of countersunk 122 (see length A in Fig. 4)" is equivalent to the axial length of stator core 11A shown in Fig. 5, for example. For example, if the axial length of stator core 11A is "76 mm" and the axial length of stator core 11 is "50.5 mm," it is preferable that the depth of countersunk 122 be "14.6 mm or more."

[0024] Fig. 7 shows the relationship between the amount of change in linear expansion of stator core 11 and case 12 and the depth of countersunk 122. As shown in Fig. 7, for example, if the axial length of stator core 11 is set to "50.5 mm," setting the depth of countersunk 122 to "14.6 mm" will result in the same amount of change in linear expansion as when the axial length is "76 mm."

[0025] As shown in Fig. 4, by providing a countersunk hole 122 at the mouth of the female thread portion 121, the thickness of the case 12 extended by the countersunk hole 122 is laminated onto the stator core 11, thereby achieving an effect equivalent to that of a structure in which the axial length of the stator core 11 is increased (see Fig. 5). In other words, by simulating the amount of change in linear expansion of the stator core 11A with a long axial length using the stator core 11 with a short axial length, it is possible to suppress loosening of the fastening member 13 due to thermal stress.

[0026] (Variation) The configuration of the countersunk portion 122 is not limited to the configuration shown in Fig. 4. For example, as in the rotating electric machine 1A shown in Fig. 8, a separate member 14 having a countersunk portion 141 similar to the countersunk portion 122 formed therein may be provided in the seating portion of the stator core 11. By providing the countersunk portion 141 as a separate member 14 in this way, the manufacturing cost can be further reduced compared to when the countersunk portion 122 is provided in the case 12 itself.

[0027] According to the rotating electric machine of the embodiment described above, the linear expansion change amount equivalent to that of the stator core 11A having a long axial length can be simulated using the stator core 11 having a short axial length, thereby suppressing loosening of the fastening member 13 due to thermal stress without compromising costs or fixing reliability.

[0028] Further advantages and modifications will readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0029] 1,1A,101,102 Rotating electric machine 11,11A stator core 111 Through hole 12 cases 121 Female thread 122 Countersink 13 Fastening members 14 Separate parts 141 Counterbore

Claims

[Claim 1] a stator core formed by laminating electromagnetic steel sheets each having an insulating layer on its surface; a case made of a material having a linear expansion coefficient larger than that of the stator core and configured to accommodate the stator core; a fastening member that fastens and fixes the stator core to a female thread portion provided in the case; Equipped with A counterbore of C0.5 mm or more is provided at the mouth of the female thread portion so that the fastening member does not fit into it. Rotating electric motor.

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