Method of molding electromagnetic steel sheets

Abstract

To provide a method of molding electromagnetic steel sheets, capable of suppressing the waviness of the electromagnetic steel sheets.SOLUTION: A method of molding electromagnetic steel sheets stacked to constitute a rotor core of a motor includes the steps of: crushing both ends of an electromagnetic steel sheet 10 in a width direction of a bridge to thicken a bridge center; bending the electromagnetic steel sheet in a length direction of the bridge to form a projecting portion 11; and restraining both ends in the length direction of the bridge to crush the projecting portion to an original thickness. A punch 20 and a die 21 used in the step of crushing the projecting portion have a groove 22 in a central part in the length direction of the bridge, and a depth of the groove is determined such that the electromagnetic steel sheet is pushed by a certain amount or more when the projecting portion has a predetermined finished thickness L1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for forming an electrical steel sheet. [Background technology]

[0002] Patent Document 1 discloses a rotor core structure in which a bridge press-down portion is formed on the bridge of the electromagnetic steel sheet that forms the rotor core, and a protrusion is formed on the longitudinal extension of the bridge that protrudes in the opposite direction to the recess of the bridge press-down portion. As a result, when hardening treatment is performed on the bridge by pressing, the force that tends to extend in the radial direction of the electromagnetic steel sheet is absorbed by the deformation of the protrusion, thereby suppressing warping of the electromagnetic steel sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-085776 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the rotor core structure disclosed in Patent Document 1, the protrusions are obtained by thickening the bridges and pressing one surface of the bridges. However, bending of the protrusions may result in a decrease in rigidity.

[0005] One solution to this problem is to crush the protrusions and process them into a flat surface after hardening. This allows the plate thickness and bending shape of the product after molding to be restored to their original state, which is expected to prevent a decrease in rigidity.

[0006] However, because there is a gap between the punch used in the process of crushing the protrusions and the thin-walled portion around the protrusions, it is difficult to fully restore the plate thickness and bent shape of the formed product to their original state, and minute undulations remain in the formed product. If such undulations remain in the formed product, they may interfere with each other when stacked to form the rotor core, resulting in a decrease in strength due to gaps and other reasons.

[0007] This processing example will be described with reference to Fig. 4. When an electromagnetic steel sheet 100 having a protrusion 111 is press-processed using a punch 120 and a die 121, the periphery of the protrusion 111 is not in contact with the punch 120 and the die 121 due to the protrusion 111, and therefore, the electromagnetic steel sheet 100 is not sufficiently processed into a flat shape.

[0008] The present disclosure has been made to solve such problems, and has an object to provide a method for forming an electromagnetic steel sheet that can suppress waviness in the electromagnetic steel sheet. [Means for solving the problem]

[0009] The method for forming an electromagnetic steel sheet according to the present disclosure is a method for forming an electromagnetic steel sheet to be laminated to form a rotor core of a motor, and includes a step of crushing both ends of a bridge of the electromagnetic steel sheet in the width direction to thicken the center of the bridge, a step of bending the electromagnetic steel sheet in the length direction of the bridge to form a protrusion, and a step of restraining both ends of the bridge in the length direction to crush the protrusion to its original thickness, wherein a punch and a die used in the step of crushing the protrusion have a groove in the center of the bridge in the length direction, and the depth of the groove is determined so that the electromagnetic steel sheet is pressed in by a certain amount or more when the protrusion has a predetermined finished thickness L1. In this way, a method for forming an electromagnetic steel sheet capable of suppressing waviness of the electromagnetic steel sheet can be provided. Effect of the Invention

[0010] The present disclosure makes it possible to provide a method for forming an electromagnetic steel sheet that can suppress waviness in the electromagnetic steel sheet. [Brief description of the drawings]

[0011] [Figure 1] 1 is a flowchart illustrating a forming method of an electrical steel sheet according to the present disclosure. [Diagram 2] 1A to 1C are diagrams illustrating a forming method of an electromagnetic steel sheet according to the present disclosure. [Diagram 3] 1A to 1C are diagrams illustrating a forming method of an electromagnetic steel sheet according to the present disclosure. [Figure 4] 1A to 1C are diagrams illustrating a conventional method for forming an electromagnetic steel sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The method for forming an electromagnetic steel sheet according to the present disclosure will be described below. The electromagnetic steel sheet according to the present disclosure is used to form a rotor core of a motor, and the rotor core is formed by stacking a plurality of the electromagnetic steel sheets.

[0013] 1 is a flowchart showing a method for forming an electromagnetic steel sheet according to the present disclosure. First, for an electromagnetic steel sheet having bridges, both ends of the bridges in the width direction are crushed to increase the thickness of the center of the bridges (S101).

[0014] Next, the bridge is bent in the longitudinal direction (S102). This forms protrusions on the electromagnetic steel sheets. After that, both ends of the bridge in the longitudinal direction are restrained, and the protrusions are crushed to their original thickness (S103).

[0015] Here, the step of crushing the protrusions will be described with reference to Figures 2(a) and (b). The electromagnetic steel sheet 10 having the protrusions 11 shown in Figure 2(a) is crushed by press working using a punch 20 and a die 21. The punch 20 and the die 21 have a groove 22 in the center in the longitudinal direction of the bridge.

[0016] 2(b) shows a state in which protrusion 11 has been crushed to a predetermined finished thickness L1. If the thickness of electromagnetic steel sheet 10 after press working is L2 and the thickness of electromagnetic steel sheet 10 before press working is L3, then the depth L4 of groove 22 is preferably determined according to the following formula (1). L4 = (L1 - L2) / 2 (1) However, L2 <L3である。

[0017] By setting the depth L4 of groove 22 in this manner, even if protrusion 11 is crushed and spreads in the width direction of the bridge during press working, a sufficient gap is obtained so that it does not come into contact with groove 22. In addition, because electromagnetic steel sheet 10 is pressed in by more than a certain amount, the bent shape of electromagnetic steel sheet 10 is processed into a flat shape.

[0018] 3(a) to (d) show the details of the process of crushing the protrusions. The left column of Fig. 3(a) to (d) shows cross-sectional views of the bridge in the width direction, and the right column shows cross-sectional views of the bridge in the length direction.

[0019] Fig. 3(a) shows a state in which the groove 22 of the punch 20 is in contact with the protrusion 11. Fig. 3(b) shows a state in which the punch 20 descends, and the bent shape of the protrusion 11 is processed into a flat shape. Fig. 3(c) shows a state in which the punch 20 descends further, and the bent shape of the electromagnetic steel sheet 10 including the periphery of the protrusion 11 is processed into a flat shape. Fig. 3(d) shows a state in which the punch 20 descends further, and the protrusion 11 reaches a predetermined finished thickness L1, completing the press working.

[0020] In this way, the press working is performed sufficiently on the electromagnetic steel sheet 10 including the periphery of the protrusion 11, so that the bent shape of the electromagnetic steel sheet 10 is processed into a flat shape, making it possible to suppress waviness of the electromagnetic steel sheet.

[0021] It should be noted that the present disclosure is not limited to the above and can be modified as appropriate without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0022] 10, 100 Electrical steel sheet 11, 111 Protrusion 20, 120 punch 21, 121 Die 22 Groove

Claims

[Claim 1] A forming method for laminating electromagnetic steel sheets to form a rotor core of a motor, comprising the steps of: a step of crushing both ends of the bridge in the width direction of the electromagnetic steel plate to thicken the center of the bridge; bending the electromagnetic steel sheet in a length direction of the bridge to form a protrusion; and compressing the protrusions to their original thickness by restraining both ends of the bridge in the longitudinal direction. The punch and die used in the step of crushing the protrusion have a groove in the center of the bridge in the longitudinal direction, The depth of the groove is determined so that the electromagnetic steel sheet is pressed in by a certain amount or more when the protrusion reaches a predetermined finished thickness L1. Method of forming electromagnetic steel sheets.

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