Layered core

Abstract

To provide a layered core that is able to prevent the possibility of decreasing fatigue life.SOLUTION: A layered core 10 according to the present disclosure is a layered core 10 in which steel plates 1 are layered. The layered core 10 includes: a weld bead 1a formed by using a predetermined welding method; and a plasma weld portion 1e formed by plasma-welding a boundary 1c between a base material 1b and the weld bead 1a. The layered core 10 preferably includes: the weld bead 1a; and a plasma weld portion 1f formed by plasma-welding a boundary 1d between the base material 1b and the weld bead 1a.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to laminated cores. [Background technology]

[0002] The electromagnetic steel sheet laminated core disclosed in Patent Document 1 includes a laminate in which electromagnetic steel sheets are laminated, and a welded portion in which the outer circumferential surface of the laminate is welded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2016-530861 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have discovered the following technical problems. At the boundary between the weld bead and the base material, a notch or a recess is formed, which may cause a change in hardness. As a result, stress tends to concentrate at the boundary between the weld bead and the base material. Therefore, there is a risk that the fatigue life will be reduced at the boundary between the weld bead and the base material. Furthermore, when such an electromagnetic steel laminated core is used as a rotor, vibrations will occur due to attraction and repulsion (torque ripple) caused by the imbalance and the number of poles. Furthermore, when such an electromagnetic steel laminated core is used as a stator, high-frequency vibrations will occur because the N pole and S pole are switched at high speed in the same way. Therefore, if the fatigue life deteriorates, breakage will easily occur.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and provides a laminated core that can suppress the risk of a decrease in fatigue life. [Means for solving the problem]

[0006] The laminated core according to the present disclosure is A laminated core made of laminated steel plates, A weld bead formed using a predetermined welding method; The welded joint is provided with a plasma welded portion formed by plasma welding the boundary between the base material and the weld bead. Effect of the Invention

[0007] According to the present disclosure, the risk of a decrease in fatigue life can be suppressed. [Brief description of the drawings]

[0008] [Figure 1A] FIG. 2 is a plan view of a laminated core according to the first embodiment. [Figure 1B] FIG. 2 is a side view of the laminated core according to the first embodiment. [Diagram 2] 3A to 3C are schematic diagrams illustrating a method for manufacturing the laminated core according to the first embodiment. [Diagram 3] 1 is a graph showing hardness versus measurement position according to an example and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings are appropriately simplified for clarity of explanation.

[0010] <Embodiment 1> A first embodiment will be described with reference to Figures 1A and 1B. Figure 1A is a plan view of a laminated core according to the first embodiment. Figure 1B is a side view of the laminated core shown in Figure 1A.

[0011] Naturally, the right-handed XYZ coordinate system shown in Figure 1A and other drawings is for the convenience of explaining the positional relationship of the components. Usually, the positive direction of the Z axis is vertically upward, and the XY plane is a horizontal plane, which is common among the drawings.

[0012] As shown in FIG. 1A and FIG. 1B, the laminated core 10 includes a plurality of laminated steel plates 1. The steel plate 1 is, for example, a substantially circular plate. The steel plate 1 may be formed, for example, by punching an electromagnetic steel plate. The laminated core 10 may be used as a stator or rotor in a motor. An example of the laminated core 10 shown in FIG. 1B is a rotor that can rotate around the Z1 axis and includes a shaft 2. The shaft 2 extends from the laminated steel plates 1 along the Z1 axis. In the example of the laminated core 10 shown in FIG. 1B, the laminated steel plates 1 are substantially cylindrical or cylindrical.

[0013] The laminated core 10 may have at least one of the welding regions 1A, 1B, 1C, 1D, 1E, and 1F. An example of the laminated core 10 shown in FIG. 1B has the welding regions 1A, 1B, 1C, 1D, 1E, and 1F. The welding regions 1A, 1B, and 1C are arranged at a predetermined interval on the upper end of the outer circumferential surface of the laminated core 10. The welding regions 1D, 1E, and 1F are arranged at a predetermined interval on the lower end of the outer circumferential surface of the laminated core 10.

[0014] As shown in FIG. 2, a weld bead 1a and plasma welds 1e and 1f are formed in a base material 1b in a welded region 1A.

[0015] The weld bead 1a may be formed using a predetermined welding method. The welding method may be, for example, TIG (Tungsten Inert Gas) welding, MIG (Metal Inert Gas) welding, laser welding, or the like. The weld bead 1a may contain more impurities than the base material 1b. The weld bead 1a may be alloyed. The hardness of the weld bead 1a may be higher than the hardness of the base material 1b. The cross-sectional shape of the weld bead 1a may be, for example, substantially arc-shaped, substantially semicircular, substantially semi-elliptical, or the like.

[0016] The plasma welded portion 1e is formed by plasma welding the boundary 1c between the base material 1b and the weld bead 1a. Specifically, the base material 1b and the weld bead 1a in the vicinity of the boundary 1c are melted and solidified to form the plasma welded portion 1e. The plasma welded portion 1f is formed by plasma welding the boundary 1d between the base material 1b and the weld bead 1a. The base material 1b and the weld bead 1a in the vicinity of the boundary 1d are melted and solidified to form the plasma welded portion 1e. In the base material 1b in the welded regions 1B, 1C, 1D, 1E, and 1F, the weld bead 1a and the plasma welded portions 1e and 1f are formed, as in the welded region 1A. The thickness of the plasma welded portions 1e and 1f may be determined according to the required mechanical strength.

[0017] <Manufacturing method> Next, a method for manufacturing the laminated core 10 will be described with reference to FIG.

[0018] In the manufacturing method of the laminated core 10, a commercially available welding device can be used. The welding device may include, for example, a robot, a wire feed motor, a welding torch TR shown in FIG. 2, and a welding machine. The robot movably holds the welding torch TR and is equipped with a wire feed motor. The wire feed motor appropriately supplies the welding wire to the welding torch TR. The welding torch TR or the welding wire supplied to the welding torch TR, the laminated steel plates 1, and the welding machine are arranged on an electric circuit so that an arc discharge can occur. The welding machine appropriately supplies a current to the electric circuit. Depending on the welding method, the configuration of the welding device, for example, the welding torch TR, may be replaced. Also, depending on the welding method, a different welding device may be used.

[0019] A plurality of steel plates 1 are welded together to form a weld bead 1a (step ST1). Specifically, a plurality of steel plates 1 are stacked. The upper and lower ends of the outer circumferential surfaces of the stacked steel plates 1 are welded together. The welding method used in step ST1 is, for example, TIG (Tungsten Inert Gas) welding, MIG (Metal Inert Gas) welding, laser welding, or the like.

[0020] Next, the boundary 1c between the weld bead 1a and the base material 1b is plasma welded to form a plasma weld 1e (step ST2). Specifically, the welding torch TR is brought close to the boundary 1c. An arc discharge is generated near the boundary 1c using a plasma welding method. Then, the boundary 1c melts and then solidifies. This forms the plasma weld 1e. Note that in this step ST2, weld dressing may be performed using the plasma welding method. The thickness of the plasma weld 1e may be determined by appropriately changing the welding conditions, such as the voltage and current value of the welding power source, the attitude of the welding torch TR, and the flow rate of the shielding gas.

[0021] Finally, the boundary 1d between the weld bead 1a and the base material 1b is plasma welded to form a plasma welded portion 1f (step ST3). Specifically, the welding torch TR is brought close to the boundary 1d. An arc discharge is generated near the boundary 1d using a plasma welding method. Then, the boundary 1d melts and then solidifies. This forms the plasma welded portion 1f. Note that in this step ST3, weld dressing may be performed using the plasma welding method. The thickness of the plasma welded portion 1f may be determined by appropriately changing the welding conditions, such as the voltage and current value of the welding power source, the attitude of the welding torch TR, and the flow rate of the shielding gas.

[0022] The above-mentioned steps ST1 to ST3 are also carried out on the welding regions 1B, 1C, 1D, 1E, and 1F of the laminated core 10.

[0023] In this manner, the laminated core 10 can be manufactured. In the welded region 1A of the laminated core 10, plasma welds 1e, 1f are formed between the weld bead 1a and the base material 1b. Therefore, the plasma welds 1e, 1f are flatter than the boundaries 1c, 1d between the weld bead 1a and the base material 1b, and do not have recesses or notches. This can reduce the risk of a decrease in fatigue life.

[0024] Furthermore, even if the weld bead 1a contains a large amount of impurities, the plasma welded parts 1e and 1f are formed by plasma welding. This ensures the penetration depth of the weld bead 1a and the base material 1b, and ensures the thickness of the plasma welded parts 1e and 1f. This reduces the risk of a decrease in fatigue life.

[0025] Moreover, an example of the laminated core 10 shown in FIG. 1A and FIG. 1B is a rotor. Moreover, the welding regions 1A, 1B, and 1C are arranged at a predetermined interval at the upper end of the outer peripheral surface of the laminated core 10. Moreover, the welding regions 1D, 1E, and 1F are arranged at a predetermined interval at the lower end of the outer peripheral surface of the laminated core 10. Therefore, when the laminated core 10 is used as a rotor capable of clockwise and counterclockwise rotation, abnormal noises, such as wind noises, during rotation of the laminated core 10 can be suppressed. Furthermore, since the rotor rotates at high speed in many cases, even a slight imbalance generates vibrations. Furthermore, in the rotor of an IPM (Interior Permanent Magnet) motor, magnets are not uniformly arranged, so magnets are attracted and repelled periodically. Therefore, the repulsive force received by the rotor is not constant, and vibrations occur. As described above, the laminated core 10 can suppress the risk of a decrease in fatigue life, so that it is possible to ensure a sufficient fatigue life even when used as a rotor. When the laminated core 10 is used as a rotor that can rotate in only one direction, at least one of the welded regions 1A, 1B, 1C, 1D, 1E, and 1F may be arranged at a predetermined interval at the lower end or upper end of the outer circumferential surface of the laminated core 10. If the cross-sectional shape of the weld bead 1a is, for example, a substantially arc-like, substantially semicircular, substantially semielliptical, or the like, wind noise generated when the laminated core 10 rotates can be suppressed when the laminated core 10 is used as a rotor.

[0026] In many cases, a high-frequency alternating current flows through the coil of the stator, and the rotor is rotated by switching between the north pole and the south pole at high speed. One example of the number of switching times is the product of the rotor rotation speed of 17,000 rpm and the number of poles of 8. Each time, an attractive force and a repulsive force are generated in the coil, and the NV (vibration and noise) is propagated, causing vibrations in the entire stator. Therefore, if the conventional plasma welding is not performed, there is a problem that the stator easily breaks. As described above, since the laminated core 10 can suppress the risk of a decrease in fatigue life, it is good for ensuring a sufficient fatigue life even when used as a stator.

[0027] <Example> Next, the results of measuring the hardness of the example and the comparative example will be described with reference to FIG.

[0028] In the embodiment, the hardness of the welded region corresponding to the welded region 1A was measured in a laminated core having the same configuration as the laminated core 10 described above. The positions where the hardness was measured were each position on a straight line crossing the welded region, specifically, the positions corresponding to the base material 1b, the plasma welded portion 1f, the weld bead 1a, the plasma welded portion 1e, and the base material 1b near the welded region 1A. A hardness curve PC showing the measured hardness is shown in FIG. 3.

[0029] In the comparative example, the hardness of the laminated core manufactured by performing only step ST1 of the manufacturing method of the laminated core 10 described above was measured. The positions for measuring the hardness were positions on a straight line crossing the welded region, as in the example, specifically, positions corresponding to the base material 1b, the boundary 1d, the weld bead 1a, the boundary 1c, and the base material 1b near the welded region 1A. A hardness curve RC showing the measured hardness is shown in FIG. 3.

[0030] As shown in Fig. 3, the hardness curve RC according to the comparative example is constant from the base material 1b to the position corresponding to the boundary 1d of the comparative example, and increases from the boundary 1d to the position corresponding to the weld bead 1a. The hardness curve RC according to the comparative example also decreases from the weld bead 1a to the position corresponding to the boundary 1c, and is constant from the boundary 1c to the position corresponding to the base material 1b. In other words, the change in the slope of the hardness curve RC is greatest at the positions corresponding to the boundaries 1d and 1c. Therefore, stress is likely to concentrate at the positions corresponding to the boundaries 1d and 1c in the laminated core according to the comparative example.

[0031] On the other hand, the hardness curve PC according to the embodiment is constant at a position corresponding to the base material 1b of the embodiment, and rises from the plasma welded portion 1f to a position corresponding to the welded bead 1a. The hardness curve PC according to the embodiment also falls from the welded bead 1a to a position corresponding to the plasma welded portion 1e, and is constant at a position corresponding to the base material 1b. The change in the slope of the hardness curve PC is smaller than the change in the slope of the hardness curve RC at the boundaries 1d and 1c. Therefore, the change in the slope of the hardness at each measurement position in the embodiment is smaller than the change in the slope of the hardness at the boundaries 1d and 1c in the comparative example. As a result, the laminated core according to the embodiment is less likely to concentrate stress than the laminated core according to the comparative example. Therefore, the fatigue life of the laminated core according to the embodiment is longer than the fatigue life of the laminated core according to the comparative example.

[0032] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. In addition, the present invention can be implemented by appropriately combining the above-described embodiment and examples thereof. [Explanation of symbols]

[0033] 10 Laminated Core 1 steel plate 1A, 1B, 1C, 1D, 1E, 1F Welding Area 1a Weld bead 1b Base material 1c, 1d boundary 1e, 1f Plasma welded parts 2 Shaft TR Welding Torch PC, RC hardness curve

Claims

[Claim 1] A laminated core made of laminated steel plates, A weld bead formed using a predetermined welding method; A laminated core having a plasma welded portion formed by plasma welding the boundary between a base material and the weld bead.

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