Manufacturing method of coil spring

Abstract

To provide a manufacturing method of a coil spring which can suppress lowering of productivity when manufacturing a plurality of coil springs with different shapes.SOLUTION: A manufacturing method of a coil spring includes: a cold molding step of cold molding the base material, and manufacturing a spiral molding material; a quenching step of quenching the molding material; and an electric tempering step of tempering the quenched molding material by electric heating, wherein in the electric tempering step, currents are carried to the molding material in a state where both ends of the molding material are held by a first current-carrying member for holding one end of the quenched molding material and a second current-carrying member for holding the other end of the quenched molding material, and the first and second current-carrying members hold the molding material by a first holding member, and a second holding member for sandwiching the molding material together with the first holding member, in which a radius of curvature of a surface contacting the molding material is smaller than a radius of curvature formed by the inner periphery of the molding material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a coil spring. [Background technology]

[0002] Conventionally, hot forming and cold forming are employed in the process of manufacturing coil springs. Of these, hot forming allows for the forming of thick wire rods, but the degree of freedom in the shape to be formed is small. On the other hand, cold forming allows for a high degree of freedom in the shape to be formed, but it has been difficult to form thick wire rods. As a technology that allows for a high degree of freedom in the shape and allows for the forming of thick wire rods, there is known a technology in which wire rods are cold formed and then heat treated, such as quenching and tempering, is performed (see, for example, Patent Document 1). In Patent Document 1, heat treatment is performed by attaching electrodes to both ends of the coil-shaped product (workpiece) after cold forming and passing electricity through them. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5574772 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the electrode portion is formed with a contact surface conforming to the surface properties of the workpiece, and it was necessary to prepare an electrode portion for each shape of the workpiece (wire shape or coil diameter). This resulted in a problem that when producing coil springs of various shapes, a large number of types of electrode portions had to be prepared, which increased the number of jigs and tools required and the number of setups required for production, reducing the productivity of producing coil springs of various shapes.

[0005] The present invention has been made in consideration of the above, and has an object to provide a manufacturing method for a coil spring that can suppress a decrease in productivity when producing coil springs of a plurality of shapes. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a method for manufacturing a coil spring according to the present invention is a method for manufacturing a coil spring by processing a base material made of a wire, and includes a cold forming step of cold forming the base material to produce a formed material having a spiral shape, a quenching step of quenching the formed material, and an electric tempering step of tempering the formed material after the quenching by electric heating, wherein the electric tempering step includes a first electric member that holds one end of the formed material after the quenching, and a second electric member that holds the formed material after the quenching. The formed material is gripped at both ends by a second conductive member which grips the other end of the formed material, and the first and second conductive members are a first gripping member located on the outer periphery of the formed material and a second gripping member located on the inner periphery of the formed material and clamping the formed material between the first gripping member, and the radius of curvature of the surface in contact with the formed material is smaller than the radius of curvature of the inner periphery of the formed material, and the second gripping member which clamps the formed material between the first gripping member and the first gripping member grips the formed material.

[0007] In addition, the manufacturing method of a coil spring according to the present invention is characterized in that, in the above invention, the first gripping member has a flat portion having a planar shape provided on a surface that contacts the formed material, and the electric tempering step grips the formed material with the flat portion of the first gripping member and the outer curved surface of the second gripping member, and heats the formed material by electric current.

[0008] In addition, the manufacturing method of a coil spring according to the present invention is characterized in that, in the above invention, the first gripping member has a curved surface that is provided on a surface that contacts the formed material, is concavely curved, and the radius of curvature of the curved surface is larger than the wire diameter of the formed material, and the electric tempering step grips the formed material with the curved surface of the first gripping member and the outer curved surface of the second gripping member, and heats the formed material by applying electric current.

[0009] In addition, the manufacturing method of a coil spring according to the present invention is characterized in that, in the above invention, the first gripping member has a groove portion formed on a surface that contacts the formed material and has a V-shaped groove shape, and the electric tempering step grips the formed material with the groove portion of the first gripping member and the outer curved surface of the second gripping member, and heats the formed material by applying electric current.

[0010] In addition, in the method for manufacturing a coil spring according to the present invention, in the above-mentioned invention, the current tempering step heats the formed material by changing a temperature increase rate stepwise.

[0011] In addition, the manufacturing method of a coil spring according to the present invention is characterized in that, in the above invention, it further includes an electrical heating step that is performed before the quenching step, and that performs electrical heating on the formed material after the cold forming. Effect of the Invention

[0012] According to the present invention, it is possible to suppress a decrease in productivity when manufacturing coil springs of a plurality of shapes. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the structure of a coil spring produced by a manufacturing method according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining a method for manufacturing a coil spring according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram for explaining resistive heating. [Figure 4] FIG. 4 is a view seen from the direction of an arrow A shown in FIG. [Diagram 5] FIG. 5 is a diagram for explaining the relationship between the temperature of the forming material and time during electrical heating. [Figure 6] FIG. 6 is a diagram for explaining the resistive heating according to the first modification. [Figure 7] FIG. 7 is a diagram for explaining the resistive heating according to the second modification. [Figure 8] FIG. 8 is a diagram for explaining the relationship between the temperature of the formed material and time when electrically heated according to the third modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention (hereinafter, referred to as "embodiment") will be described with reference to the attached drawings. Note that the drawings are schematic, and the relationship between the thickness and width of each part, the thickness ratio of each part, etc. may differ from the actual ones, and the drawings may include parts with different dimensional relationships and ratios.

[0015] (Embodiment) 1 is a diagram showing the structure of a coil spring manufactured by a manufacturing method according to an embodiment of the present invention. The coil spring 1 is manufactured by spirally winding a wire material. The coil spring 1 is manufactured using, for example, a wire material made of a metal or an alloy.

[0016] Next, a method for manufacturing the coil spring 1 will be described with reference to Fig. 2 to Fig. 4. Fig. 2 is a diagram for explaining a method for manufacturing a coil spring according to an embodiment of the present invention. The coil spring 1 is produced by processing a base material.

[0017] First, a wire material 100 (see FIG. 2(a)) is drawn to obtain a drawn wire material 101 (see FIG. 2(b)). At this time, the wire material 100 (drawn wire material 101) is not subjected to a heat treatment, and a wire drawing machine is used to reduce the diameter of the wire material, for example by passing it through a die, thereby obtaining a wire material (drawn wire material 101) with a designed diameter.

[0018] Thereafter, the drawn wire material 101 is shaped by cold forming (see FIG. 2(c)). Specifically, the drawn wire material 101 is wound using a winding machine 200. The winding machine 200 includes, for example, a winding pin and a cutting tool, and shapes the drawn wire material 101 by bringing it into contact with the winding pin, and cuts the drawn wire material 101 to a predetermined length using the cutting tool.

[0019] The formed material 102 obtained by winding and cutting the drawn wire 101 is subjected to electrical heating (see FIG. 2(d)). The electrical heating is performed by attaching a first current-carrying member 211 to one end of the formed material 102 and a second current-carrying member 212 to the other end, and passing a current through the first current-carrying member 211 and the second current-carrying member 212 to pass the current through the formed material 102. This current flow generates heat, and the formed material 102 is heated. The first current-carrying member 211 and the second current-carrying member 212 are controlled under the control of the control device 210 so that the movement of the members (the gripping of the molding material 102) and the current supply thereto are controlled.

[0020] After the formed material 102 is electrically heated, the formed material 102 is quenched (see FIG. 2(e)). The formed material 102 is immersed in a tank 221 containing a water-soluble quenchant 222. At this time, the temperature and concentration of the water-soluble quenchant are controlled so as to obtain an appropriate heat treatment quality. By immersing the formed material 102 in the water-soluble quenchant 222, a quenched formed material 103 is obtained. Note that oil may be used instead of the water-soluble quenchant 222.

[0021] After quenching, the formed material 103 is subjected to electrical heating (electrical tempering) for tempering (see FIG. 2(f)). In electrical tempering, a first electrical member 231 is attached to one end of the formed material 103 and a second electrical member 232 is attached to the other end, and an electric current is passed through the first electrical member 231 and the second electrical member 232 to pass an electric current through the formed material 103. This electrical current generates heat, and the formed material 103 is heated. In electrical tempering, electrical current conditions are set for reheating the formed material 103 to a predetermined hardness. The first current-carrying member 231 and the second current-carrying member 232 are controlled by the control device 230 so that the movement of the members (the gripping of the molding material 103) and the current supply thereto are controlled.

[0022] Here, the electric heating performed during electric tempering (see FIG. 2(f)) will be described with reference to FIG. 3 to FIG. 5. When electric heating is performed on the formed material 102 before quenching (see FIG. 2(d)), heating can also be performed using a similar configuration.

[0023] Fig. 3 is a diagram for explaining electrical heating. Fig. 4 is a diagram seen from the direction of an arrow A shown in Fig. 3. The first electrical current conducting member 231 has a first gripping member 231a and a second gripping member 231b, and is located on one end side of the molding material 103. The first gripping member 231a has a rectangular column shape and is located on the outer periphery side of the molded material 103. The first gripping member 231a has a flat portion 2311 having a flat surface on the side that comes into contact with the molded material 103. Note that as long as the surface of the first gripping member 231a that comes into contact with the molded material 103 is flat, other portions may be cylindrical or have another polygonal shape. The second gripping member 231b is cylindrical and is located on the inner periphery side of the molded material 103. The radius of curvature of the side surface (outer periphery) of the second gripping member 231b is smaller than the radius of curvature of the inner periphery of the molded material 103. Here, the radius of curvature of the inner periphery of the molded material 103 corresponds to the radius of curvature of the inner periphery of the molded material 103 in a plan view (see FIG. 4) seen from the axial direction (winding axial direction) of the molded material 103. By making the radius of curvature of the side surface of the second gripping member 231b smaller than the radius of curvature of the inner periphery of the applicable molded material 103, it can be applied to various types of molded materials 103.

[0024] The first gripping member 231a and the second gripping member 231b are supplied with power through a power transmission line (not shown) under the control of the control device 230. The first gripping member 231a can be moved in a direction approaching or away from the second gripping member 231b under the control of the control device 230. The second gripping member 231b can be moved in a direction approaching or away from the first gripping member 231a under the control of the control device 230. In addition, the second gripping member may be configured to be movable toward the first gripping member in order to correspond to the diameter of the winding of the formed material 103, and the first current-carrying member 231 and the second current-carrying member 232 may be configured to be movable in a direction approaching or away from each other in order to correspond to the number of turns of the formed material 103.

[0025] The second current-carrying member 232 has a first gripping member 232a and a second gripping member 232b, and is located on the other end side of the formed material 103. The first gripping member 232a has a prismatic shape, and is located on the outer periphery side of the molded material 103. The first gripping member 232a has a flat portion 2321, the surface of which that comes into contact with the molded material 103 is flat. The second gripping member 232b has a cylindrical shape, and is located on the inner periphery side of the molded material 103. The radius of curvature of the side surface (outer periphery) of the second gripping member 232b is smaller than the radius of curvature of the inner periphery of the molded material 103.

[0026] The first current-carrying member 231 and the second current-carrying member 232 have their current applied thereto controlled via a power transmission line (not shown) under the control of the control device 230. In addition, the first gripping member 232a and the second gripping member 232b are movable under the control of the control device 230.

[0027] The control device 230 is placed on the molding material 103 at a predetermined position, and grips one end and the other end of the molding material 103 by moving the gripping members of the first current-carrying member 231 and the second current-carrying member 323, respectively. Thereafter, the control device 230 passes a current through the first current-carrying member 231 or the second current-carrying member 232 via the power transmission line. A current flows between the first current-carrying member 231 and the second current-carrying member 232 and the molding material 103 through the contact points. The heat generated at this time heats the molding material 103.

[0028] Fig. 5 is a diagram for explaining the relationship between the temperature of the molding material 103 and time during electrical heating. For example, as shown in Fig. 5, the control device 230 increases the temperature at a constant rate. At this time, the control device 230 increases the temperature of the molding material 103 by passing an electrical current at a value that increases the temperature at a constant rate. By heating at a constant rate, the molding material 103 can be heated in a short time.

[0029] By processing the base material 100 in the above-described manner, the coil spring 1 shown in FIG. 1 is produced. Here, annealing may be performed before or after the wire drawing process. Also, if the wire diameter is as designed in the base material state, it is possible to perform cold forming on the base material 100 without performing the wire drawing process.

[0030] In the embodiment of the present invention described above, one side (here, the outer periphery) of the gripping member that grips formed material 103 is flat and the other side (here, the inner periphery) is curved, and the radius of curvature of the other curved surface is made smaller than the radius of curvature of the inner periphery of formed material 103, so that formed material 103 (coil spring 1) can be securely gripped and electrified regardless of its shape. According to this embodiment, it is possible to suppress a decrease in productivity when producing coil springs of a variety of shapes.

[0031] Furthermore, according to the present embodiment, by performing electric tempering, the time required for tempering can be shortened compared to tempering using a furnace, and carbon dioxide emissions can also be reduced.

[0032] (Variation 1) Next, a first modified example of the present embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram for explaining the electrical heating according to the first modified example. In the first modified example, the configuration of the current-carrying member that performs the electrical heating is different from that of the current-carrying member according to the embodiment. In the first modified example, the configuration of the current-carrying member is the same as in the embodiment, and therefore the description will be omitted. In Fig. 6, the same components as in the embodiment are denoted by the same reference numerals.

[0033] In the first and second current-carrying members 231A and 232A according to the first modification, the movement of the members (the gripping of the molding material 103) and the energization are controlled under the control of the control device 230, similarly to the embodiment.

[0034] The first current-carrying member 231A has a first gripping member 231c and a second gripping member 231b, and is located on one end side of the molding material 103. The first gripping member 231c has a prismatic shape and is located on the outer periphery side of the molded material 103. The first gripping member 231c has a curved surface 2312 in which a part of the surface that comes into contact with the molded material 103 is curved concavely. The radius of curvature of the wall surface that forms this curved surface 2312 is preferably larger than the wire diameter of the molded material 103. Note that as long as the surface of the first gripping member 231c that comes into contact with the molded material 103 is flat, the other parts may be cylindrical or have another polygonal shape. Moreover, the first gripping member 231c is movable under the control of the control device 230 in a direction toward or away from the second gripping member 231b.

[0035] The second current-carrying member 232A has a first gripping member 232c and a second gripping member 232b, and is located on one end side of the molding material 103. The first gripping member 232c has a rectangular column shape and is located on the outer periphery of the molded material 103. The first gripping member 232c has a curved surface 2322 in which a part of the surface that comes into contact with the molded material 103 is curved concavely. The radius of curvature of the wall surface that forms this curved surface 2322 is preferably larger than the wire diameter of the molded material 103. Moreover, the first gripping member 232c is movable under the control of the control device 230 in a direction toward or away from the second gripping member 232b.

[0036] The first current-carrying member 231A and the second current-carrying member 232A are controlled by the control device 230 so that the current therethrough is controlled via a power transmission line (not shown).

[0037] The control device 230 is placed on the formed material 103 at a predetermined position, and grips one end and the other end of the formed material 103 by moving the gripping members of the first and second current-carrying members 231A and 232A. Thereafter, the control device 230 passes a current through the first and second current-carrying members 231A and 232A via the power transmission line. A current flows between the first and second current-carrying members 231A and 232A and the formed material 103 through the contact points. The heat generated at this time heats the formed material 103.

[0038] In the above-described first modification, similarly to the embodiment, the formed material 103 (coil spring 1) can be securely held and electrically heated regardless of its shape. According to the first modification, it is possible to suppress a decrease in productivity when coil springs of a variety of shapes are manufactured.

[0039] In addition, according to this modified example 1, the first gripping members 231c, 232c are each formed with concave curved surfaces 2312, 2322 on the surfaces that come into contact with the molding material 103, and the molding material 103 is gripped by each curved surface, so that the molding material 103 can be gripped more securely.

[0040] (Variation 2) Next, a second modified example of the present embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram for explaining the electrical heating according to the second modified example. In the second modified example, the configuration of the current-carrying member that performs the electrical heating is different from that of the current-carrying member according to the embodiment. Since the second modified example is the same as the embodiment except for the configuration of the current-carrying member, the description will be omitted. In Fig. 7, the same components as those in the embodiment are given the same reference numerals.

[0041] In the first current-carrying member 231B and the second current-carrying member 232B according to the second modification, the movement of the members (the gripping of the molding material 103) and the energization are controlled under the control of the control device 230, similarly to the embodiment.

[0042] The first current-carrying member 231B has a first gripping member 231d and a second gripping member 231b, and is located on one end side of the molding material 103. The first gripping member 231d has a rectangular column shape and is located on the outer periphery side of the molding material 103. The first gripping member 231d has a groove portion 2313 in which a part of the surface on the side that contacts the molding material 103 is a V-shaped groove. The formation area (formation width and depth) of this groove portion 2313 is set so that the first gripping member 231d and the second gripping member 231b do not contact each other. Note that the first gripping member 231d may have other parts that are cylindrical or have other polygonal shapes as long as the surface that contacts the molding material 103 is flat. Moreover, the first gripping member 231d is movable under the control of the control device 230 in a direction toward or away from the second gripping member 231b.

[0043] The second current-carrying member 232B has a first gripping member 232d and a second gripping member 232b, and is located on one end side of the molded material 103. The first gripping member 232d has a rectangular column shape and is located on the outer periphery side of the formed material 103. The first gripping member 232d has a groove portion 2323 having a V-shaped groove shape on a part of the surface on the side that contacts the formed material 103. The formation area (formation width) of the groove portion 2323 is preferably larger than the wire diameter of the formed material 103. Moreover, the first gripping member 232d is movable under the control of the control device 230 in a direction toward or away from the second gripping member 232b.

[0044] The first current-carrying member 231B and the second current-carrying member 232B are controlled in terms of current flow via a power transmission line (not shown) under the control of the control device 230.

[0045] The control device 230 is placed on the molding material 103 at a predetermined position, and grips one end and the other end of the molding material 103 by moving the gripping members of the first current-carrying member 231B and the second current-carrying member 232B. Thereafter, the control device 230 passes a current through the first current-carrying member 231B and the second current-carrying member 232B via the power transmission line. A current flows between the first current-carrying member 231B and the second current-carrying member 232B and the molding material 103 through the contact points. The heat generated at this time heats the molding material 103.

[0046] In the above-described second modification, similarly to the embodiment, the formed material 103 (coil spring 1) can be securely held and electrically heated regardless of its shape. According to the second modification, it is possible to suppress a decrease in productivity when coil springs of a variety of shapes are manufactured.

[0047] Furthermore, according to this modified example 2, grooves 2313, 2323 are formed on the surfaces of the first gripping members 231d, 232d that come into contact with the molding material 103, respectively, so that the molding material 103 is gripped on each curved surface, thereby making it possible to grip the molding material 103 more reliably.

[0048] (Variation 3) Next, a third modified example of the present embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining the relationship between the temperature of the molding material and time during electrical heating according to the third modified example. In the third modified example, the heating pattern when electrical heating is performed is different from the heating pattern according to the embodiment. In the third modified example, the components related to the processing are the same as those in the embodiment, and therefore the description will be omitted.

[0049] In the third modification, the control device 230 heats the molding material 103 by changing the temperature increase rate stepwise, for example, as shown in Fig. 8. At this time, the control device 230 controls the current value by changing it in two steps so that the temperature increase rate decreases after a predetermined time has elapsed.

[0050] In the third modification described above, similarly to the embodiment, the formed material 103 (coil spring 1) can be securely held and electrically heated regardless of its shape. According to the third modification, it is possible to suppress a decrease in productivity when coil springs of a variety of shapes are manufactured.

[0051] Furthermore, according to this modification example 3, the heating pattern is such that the molding material 103 is heated so that the rate of temperature rise of the molding material 103 changes stepwise and the rate of temperature rise decreases over time. Therefore, compared to the heating pattern of the embodiment, overheating can be suppressed and the heating temperature can be stabilized.

[0052] Although the embodiments for carrying out the present invention have been described above, the present invention should not be limited to the above-mentioned embodiments. For example, the first and second current-carrying members for gripping the ends of the formed material may be appropriately combined with the configurations of the current-carrying members according to the embodiment and the first and second modified examples.

[0053] In this manner, the present invention may include various embodiments not described here, and various design modifications may be made without departing from the technical idea defined by the claims.

[0054] As described above, the manufacturing method of a coil spring according to the present invention is suitable for suppressing a decrease in productivity when manufacturing coil springs of a variety of shapes. [Explanation of symbols]

[0055] 1 Coil spring 100 Base material 101 Wire drawing 102, 103 Molding materials 200 Winding machine 210, 230 Control device 211, 231 First current-carrying member 212, 232 Second current-carrying member 221 tank 222 Water-soluble quenching agent 231a, 231c, 231d, 232a, 232c, 232d First gripping member 231b, 232b Second gripping member 2311, 2321 Plane section 2312, 2322 Curved surface 2313, 2323 Groove

Claims

1. A method for manufacturing a coil spring by treating a base material made of a wire, comprising the steps of: a cold forming step of cold forming the base material to produce a spirally formed material; a quenching step of quenching the formed material; a current tempering step of tempering the quenched formed material by current heating; Including, The electric tempering step includes: a first current-carrying member that holds one end of the formed material after quenching and a second current-carrying member that holds the other end of the formed material after quenching, and a current is applied to the formed material while both ends of the formed material are held by the first current-carrying member that holds one end of the formed material after quenching, The first and second current-carrying members are a first gripping member located on the outer periphery of the formed material, and a second gripping member located on the inner periphery of the formed material and sandwiching the formed material between the first gripping member, and the radius of curvature of the surface that contacts the formed material is smaller than the radius of curvature of the inner periphery of the formed material, and the second gripping member that sandwiches the formed material between the first gripping member and the formed material is gripped by the first gripping member. A method for manufacturing a coil spring comprising the steps of:

2. The first gripping member has a flat surface portion provided on a surface that contacts the molding material, The electric tempering step includes holding the formed material by the flat surface of the first holding member and the outer circumferential curved surface of the second holding member, and electrically heating the formed material. The method for manufacturing a coil spring according to claim 1 .

3. The first gripping member has a curved surface that is provided on a surface that contacts the formed material and is concavely curved, and the curvature radius of the curved surface is larger than the wire diameter of the formed material, The electric tempering step includes holding the formed material by the curved surface of the first gripping member and the outer peripheral curved surface of the second gripping member, and electrically heating the formed material. The method for manufacturing a coil spring according to claim 1 .

4. The first gripping member has a groove portion provided on a surface that contacts the molding material and has a V-shaped groove shape, The electric tempering step includes holding the formed material by the groove portion of the first holding member and the outer peripheral curved surface of the second holding member, and electrically heating the formed material. The method for manufacturing a coil spring according to claim 1 .

5. The electric tempering step heats the forming material by changing the temperature rise rate stepwise. The method for manufacturing a coil spring according to claim 1 .

6. an electric current heating step, which is performed before the quenching step, for electrically heating the cold-formed material; The method for manufacturing a coil spring according to claim 1, further comprising:

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