Method for manufacturing coil spring

Abstract

The purpose of the present invention is to provide a method for manufacturing a coil spring capable of suppressing variations in quality. This method for manufacturing a coil spring is a method for manufacturing a coil spring in which a base material (100) made of a wire material is processed, and is provided with: a cold-forming step (c) in which the base material (100) is cold-formed to produce a spiral shaped material (102); a quenching step (e) in which the molded material (102) is quenched; and an energized tempering step (f) in which the quenched molded material (103) is tempered by energized heating.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a spiral spring. Background Art

[0002] In the past, in the process of making coil springs, hot forming or cold forming was used. Among them, hot forming can form a thicker wire, but the degree of freedom of the formed shape is small. On the other hand, although the degree of freedom of the formed shape is high, it is difficult to form a thicker wire. As a technology that has a high degree of freedom in shape and can form a thicker wire, there is a known technology that quenches and tempers the wire after cold forming (for example, refer to Patent Document 1).

[0003] Patent document 1: Japanese Patent Publication No. 63-059775. Summary of the invention

[0004] However, Patent Document 1 uses an electric furnace or a gas furnace for tempering, which has poor thermal efficiency and sometimes causes uneven temperature in the furnace, which may lead to variations in the quality of the produced coil springs.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a coil spring capable of suppressing variations in quality.

[0006] In order to solve the above-mentioned problems and achieve the purpose, the manufacturing method of the coil spring of the present invention is a manufacturing method of the coil spring formed by processing a base material formed by a wire rod, comprising: a cold forming step of cold forming the base material to produce a spirally formed material; a quenching step of quenching the formed material; and an electric tempering step of tempering the quenched formed material by electric heating.

[0007] Furthermore, the method for manufacturing a coil spring of the present invention in the above invention may further include: a drawn wire material generating step of subjecting the base material to a wire drawing process to produce a drawn wire material, and in the cold forming step, cold forming the drawn wire material.

[0008] In the method for producing a coil spring of the present invention, in the above invention, in the quenching step, the formed material may be immersed in a heated water-soluble quenching agent to perform quenching.

[0009] Furthermore, the method for manufacturing a coil spring of the present invention in the above invention may further include: an electrical heating step, which is performed before the quenching step, and electrically heats the drawn wire material.

[0010] In addition, the manufacturing method of the coil spring of the present invention may also be that in the above invention, in the electric tempering step, electricity is applied in a state where the two ends of the quenched formed material are gripped by a first electric current carrying component that grips one end of the quenched formed material and a second electric current carrying component that grips the other end of the quenched formed material, the first electric current carrying component and the second electric current carrying component grip the formed material through a first gripping component and a second gripping component, the first gripping component is located on the outer peripheral side of the formed material, the second gripping component is located on the inner peripheral side of the formed material and clamps the formed material together with the first gripping component, and the curvature radius of the surface of the second gripping component in contact with the formed material is smaller than the curvature radius of the inner periphery of the formed material, and the second gripping component clamps the formed material together with the first gripping component.

[0011] In addition, the manufacturing method of the coil spring of the present invention may also be that the first gripping member has a planar portion arranged on the surface in contact with the formed material, and in the electric tempering step, the formed material is gripped by the planar portion of the first gripping member and the outer peripheral curved surface of the second gripping member, and the formed material is electrically heated.

[0012] In addition, the manufacturing method of the coil spring of the present invention may also be that in the above invention, the first gripping member has a curved surface bent into a concave shape, the curved surface is arranged on the surface in contact with the formed material, and the curvature radius of the curved surface is greater than the wire diameter of the formed material, and in the electric tempering step, the formed material is gripped by the curved surface of the first gripping member and the outer peripheral curved surface of the second gripping member, and the formed material is electrically heated.

[0013] In addition, the manufacturing method of the coil spring of the present invention may also be that the first gripping member has a groove portion, the groove portion is arranged on the surface in contact with the formed material, and is in the shape of a V-shaped groove. In the electric tempering step, the formed material is gripped by the groove portion of the first gripping member and the outer peripheral curved surface of the second gripping member, and the formed material is electrically heated.

[0014] Furthermore, in the method for producing a coil spring of the present invention, in the above invention, in the current tempering step, the formed material may be heated by changing the temperature increase rate in stages.

[0015] Furthermore, the method for manufacturing a coil spring of the present invention in the above invention may further include: an electrical heating step, which is performed before the quenching step, for electrically heating the cold-formed formed material.

[0016] In addition, the manufacturing method of the coil spring of the present invention may also be that in the above invention, in the power-on tempering step, a first power-on period and a second power-on period are set, the first power-on period is from the start of heating of the formed material to the elapse of a specified time, and the second power-on period is from the elapse of the specified time to the end of heating, and the temperature rise rate of the formed material in the second power-on period is lower than the temperature rise rate of the formed material in the first power-on period.

[0017] In the coil spring manufacturing method of the present invention, in the above invention, in the current conduction tempering step, a current value in the second current conduction period may be smaller than a current value in the first current conduction period.

[0018] Furthermore, the method for manufacturing a coil spring of the present invention in the above invention may further include: an electrical heating step, which is performed before the quenching step, for electrically heating the cold-formed formed material.

[0019] According to the present invention, there is an effect of being able to suppress variations in quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a figure which shows the structure of the coil spring manufactured by the manufacturing method of Embodiment 1 of this invention.

[0021] Figure 2 These are diagrams for explaining the method for manufacturing the coil spring according to the first embodiment of the present invention.

[0022] Figure 3 It is a figure for demonstrating the manufacturing method of the coil spring which concerns on Embodiment 2 of this invention.

[0023] Figure 4 This is a diagram for explaining electric heating.

[0024] Figure 5 is from Figure 4 The figure is viewed in the direction of arrow A.

[0025] Figure 6 This is a diagram for explaining the relationship between the temperature of the formed material and time during electrical heating in the second embodiment of the present invention.

[0026] Figure 7 It is a diagram for explaining the electric heating according to the first modification of the second embodiment of the present invention.

[0027] Figure 8 This is a diagram for explaining electric heating according to Modification 2 of Embodiment 2 of the present invention.

[0028] Fig. 9This is a diagram for explaining the change over time of the current value and the temperature of the formed material during electric heating in the third embodiment of the present invention. DETAILED DESCRIPTION

[0029] Hereinafter, a method for implementing the present invention (hereinafter referred to as "implementation method") will be described with reference to the accompanying drawings. In addition, the accompanying drawings are schematic diagrams, and the relationship between the thickness and width of each part, the ratio of the thickness of each part, etc. may be different from the actual object, and sometimes the drawings may also include parts with different size relationships or ratios.

[0030] Implementation Method 1

[0031] 1 is a diagram showing the structure of a coil spring manufactured by the manufacturing method according to the first embodiment of the present invention. The coil spring 1 is manufactured by winding a wire into a spiral shape. The coil spring 1 is manufactured using a wire made of, for example, a metal or alloy.

[0032] Then, refer to Figure 2 A method for manufacturing the coil spring 1 will be described. Figure 2 This is a diagram for explaining a method for manufacturing a coil spring according to Embodiment 1 of the present invention. The coil spring 1 is manufactured by processing a base material.

[0033] First, a base material 100 (see Figure 2 (a)) is subjected to wire drawing to obtain a drawn wire material 101 (see Figure 2 (b)). At this time, the base material 100 (drawn wire material 101) is not subjected to heat treatment, but a wire drawing machine is used, for example, to pass the base material 100 through an eye die to reduce the diameter of the wire, thereby obtaining a wire material (drawn wire material 101) of a designed diameter.

[0034] Thereafter, the drawn wire material 101 is formed by cold forming (see Figure 2 (c)). Specifically, the wire drawing material 101 is wound using a winding machine 200. The winding machine 200 includes, for example, a winding pin and a cutting tool, and the wire drawing material 101 is formed by contacting the winding pin, and the wire drawing material 101 is cut into a predetermined length using the cutting tool.

[0035] The formed material 102 obtained by winding and cutting the drawn wire material 101 is electrically heated (see Figure 2 (d)). In the energization heating, a first energizing member 211 is installed at one end of the formed material 102, and a second energizing member 212 is installed at the other end, and current is passed through the first energizing member 211 and the second energizing member 212, thereby energizing the formed material 102. Heat is generated by the energization, thereby heating the formed material 102.

[0036] After the formed material 102 is electrically heated, the formed material 102 is quenched (see Figure 2 (e)). The formed material 102 is immersed in a tank 221 containing a water-soluble quenching agent 222. At this time, the temperature and concentration of the water-soluble quenching agent are managed to obtain an appropriate heat treatment quality. By immersing the formed material 102 in the water-soluble quenching agent 222, a formed material 103 after quenching is obtained. In addition, oil can also be used instead of the water-soluble quenching agent 222.

[0037] After quenching, the formed material 103 is subjected to electrical heating for tempering (electrical tempering) (see Figure 2 (f)). In the current tempering, a first current-carrying member 231 is installed at one end of the formed material 103, and a second current-carrying member 232 is installed at the other end, and current is passed through the first current-carrying member 231 and the second current-carrying member 232, so that the formed material 103 is energized. Heat is generated by the energization, thereby heating the formed material 103. For the current tempering, the energization conditions required for reheating the formed material 103 to a predetermined hardness are set.

[0038] By processing the base material 100 according to the above process, Figure 1 The coil spring 1 is shown.

[0039] In addition, if the wire diameter is the designed wire diameter in the state of the base material, the base material 100 can be cold-formed without wire drawing.

[0040] In the first embodiment of the present invention described above, the tempering treatment for adjusting the hardness is performed by electric heating, so the entire formed material 103 is uniformly heated, and as a result, the hardness of the entire formed material 103 can be adjusted uniformly. In addition, by performing electric tempering, the shape deviation between the formed materials 103 is suppressed, and the forming accuracy of the shape can be improved. According to the first embodiment, by performing the tempering treatment by electric heating, the quality deviation can be suppressed. In addition, in the manufacture of the coil spring 1, the yield rate can be improved.

[0041] Furthermore, according to the first embodiment, by performing the electric tempering, the time required for the tempering can be shortened compared to the case where the tempering is performed using a furnace, and the amount of carbon dioxide emissions can be reduced.

[0042] Implementation Method 2

[0043] Next, refer to Figure 3 to Figure 6 Embodiment 2 of the present invention will be described. In addition, the coil spring manufactured in this embodiment 2 is Figure 1The coil spring 1 shown. Hereinafter, a method for manufacturing the coil spring according to the second embodiment will be described. Figure 3 It is a figure for demonstrating the manufacturing method of the coil spring which concerns on Embodiment 2 of this invention.

[0044] In the second embodiment, similarly to the first embodiment, a base material 100 (see Figure 3 (a)) is subjected to wire drawing to obtain a drawn wire material 101 (see Figure 3 (b)). Thereafter, the drawn wire material 101 is formed by cold forming (see Figure 3 (c)).

[0045] The formed material 102 obtained by winding and cutting the drawn wire material 101 is electrically heated (see Figure 3 (d)). In the energization heating, a first energizing member 211 is installed at one end of the formed material 102, and a second energizing member 212 is installed at the other end, and current is passed through the first energizing member 211 and the second energizing member 212, thereby energizing the formed material 102. Heat is generated by the energization, thereby heating the formed material 102.

[0046] In the second embodiment, the movement (gripping of the formed material 102 ) and the conduction of electricity to the first conducting member 211 and the second conducting member 212 are controlled by the control device 210 .

[0047] After the formed material 102 is electrically heated, the formed material 102 is quenched (see Figure 3 (e)). The formed material 102 is immersed in a tank 221 containing a water-soluble quenching agent 222.

[0048] After quenching, the formed material 103 is subjected to electrical heating for tempering (electrical tempering) (see Figure 3 (f)).

[0049] In the second embodiment, the movement (gripping of the formed material 103 ) and the conduction of electricity to the first conducting member 231 and the second conducting member 232 are controlled by the control device 230 .

[0050] Here, refer to Figures 4 to 6 , for tempering with power (see Figure 3 In addition, when the formed material 102 before quenching is electrically heated (see Figure 3 (d)), the same structure can also be used for heating.

[0051] Figure 4 This is a diagram for explaining electric heating. Figure 5 is from Figure 4The figure is viewed in the direction of arrow A. The first conducting member 231 has a first gripping member 231 a and a second gripping member 231 b and is located at one end side of the forming material 103 .

[0052] The first gripping member 231a is prismatic and is located on the outer peripheral side of the forming material 103. The first gripping member 231a has a flat surface portion 2311 whose surface in contact with the forming material 103 is flat. In addition, the first gripping member 231a only needs to have a flat surface in contact with the forming material 103, and the other parts may be cylindrical or other polygonal shapes.

[0053] The second gripping member 231b is cylindrical and is located on the inner circumference of the forming material 103. The curvature radius of the side surface (outer circumference) 2312 of the second gripping member 231b is smaller than the curvature radius of the inner circumference of the forming material 103. Here, the curvature radius of the inner circumference of the forming material 103 corresponds to the curvature radius of the inner circumference of the forming material 103 when viewed from above along the axial direction (winding axial direction) of the forming material 103 (see Figure 5 ) The curvature radius of the inner circumference of the forming material 103. By making the curvature radius of the side surface of the second gripping member 231b smaller than the curvature radius of the inner circumference of the forming material 103 that may be applied, it can be applied to various forming materials 103.

[0054] The first gripping member 231a can move toward or away from the second gripping member 231b under the control of the control device 230. The second gripping member 231b can move toward or away from the first gripping member 231a under the control of the control device 230. In addition, in order to correspond to the winding diameter of the shaped material 103, a structure can be formed in which the second gripping member can be moved toward the first gripping member side, or in order to correspond to the number of windings of the shaped material 103, a structure can be formed in which the first conducting member 231 and the second conducting member 232 can be moved toward or away from each other.

[0055] The second conducting member 232 includes a first holding member 232 a and a second holding member 232 b and is located on the other end side of the formed material 103 .

[0056] The first gripping member 232a has a prism shape and is located on the outer peripheral side of the forming material 103. The first gripping member 232a has a flat surface portion 2321 whose surface on the side in contact with the forming material 103 is flat.

[0057] The second gripping member 232b is cylindrical and is located on the inner circumference side of the forming material 103. The curvature radius of the side surface (outer circumference) 2322 of the second gripping member 232b is smaller than the curvature radius of the inner circumference of the forming material 103.

[0058] Under the control of the control device 230 , the energization of the first energizing member 231 and the second energizing member 232 is controlled via a live wire (not shown). In addition, under the control of the control device 230 , the first gripping member 232 a and the second gripping member 232 b are movable.

[0059] The control device 230 is disposed at a predetermined position on the shaped material 103, and moves the gripping members of the first and second energizing members 231 and 232 so that they grip one end and the other end of the shaped material 103, respectively. Thereafter, the control device 230 causes current to flow through the first energizing member 231 or the second energizing member 232 via the live wire. Current flows through the contact portion between the first and second energizing members 231 and 232 and the shaped material 103. The heat generated at this time is used to heat the shaped material 103.

[0060] Figure 6 1 is a diagram for explaining the relationship between the temperature of the formed material 103 and time during electric heating. Figure 6 As shown, the control device 230 increases the temperature at a constant rate. At this time, the control device 230 supplies electricity at a current value that increases the temperature at a constant rate, thereby increasing the temperature of the formed material 103. By heating at a constant rate, the formed material 103 can be heated in a short time.

[0061] By processing the base material 100 according to the above process, Figure 1 The coil spring 1 is shown.

[0062] Here, annealing treatment may be performed before or after the wire drawing process. In addition, if the wire diameter is the designed wire diameter in the state of the base material, the base material 100 may be cold-formed without wire drawing process.

[0063] In the second embodiment of the present invention described above, the tempering treatment for adjusting hardness etc. is performed by electric heating as in the first embodiment, so that the tempering treatment by electric heating can suppress quality variation. In addition, the yield rate can be improved in the manufacture of the coil spring 1.

[0064] In addition, in the Japanese Patent Gazette No. 5574772, a contact surface corresponding to the surface property of the workpiece is formed on the electrode part, and the electrode part needs to be manufactured according to the shape (linear shape or coil diameter) of each workpiece. Therefore, when manufacturing coil springs of various shapes, the types of electrode parts that need to be prepared increase, the number of jigs increases, or the number of preparations in the manufacturing process increases, which leads to the problem of reduced productivity when manufacturing coil springs of various shapes. In response to this, in the present embodiment 2, one of the gripping parts (here, the outer peripheral side) that grips the forming material 103 is set as a plane, and the other (here, the inner peripheral side) is set as a curved surface, and the curvature radius of the other curved surface is made smaller than the curvature radius of the inner periphery of the forming material 103, thereby, regardless of the shape of the forming material 103 (coil spring 1), it can be reliably gripped and energized. According to the present embodiment 2, it is possible to suppress the reduction in productivity when manufacturing coil springs of various shapes.

[0065] Furthermore, according to the second embodiment, by performing the electric tempering, the time required for the tempering can be shortened compared to the case of performing the tempering using a furnace, and the amount of carbon dioxide emissions can be reduced.

[0066] Modification 1 of Implementation Example 2

[0067] Next, refer to Figure 7 Modification 1 of Implementation Example 2 is described. Figure 7 This is a diagram for explaining the energized heating of the variant 1 of the second embodiment. In the variant 1, the structure of the energized component for energized heating is different from that of the embodiment. In the variant 1, except for the structure of the energized component, the rest is the same as the embodiment, so the description is omitted. In addition, Figure 7 In the present invention, the same reference numerals are used to denote the same components as those in the embodiment.

[0068] The first conducting member 231A and the second conducting member 232A of Modification 1 are similar to those of the embodiment, and the movement of the members (gripping of the formed material 103 ) and the conduction of electricity are controlled by the control device 230 .

[0069] The first conducting member 231A includes a first holding member 231 c and a second holding member 231 b and is located on one end side of the formed material 103 .

[0070] The first gripping member 231c is prismatic and is located on the outer peripheral side of the forming material 103. The first gripping member 231c has a curved surface 2313 in which a portion of the surface on the side in contact with the forming material 103 is curved into a concave shape. The curvature radius of the wall surface forming the curved surface 2313 is preferably larger than the wire diameter of the forming material 103. In addition, the first gripping member 231c only needs to have a curved surface in contact with the forming material 103, and the other portion may be cylindrical or other polygonal shapes.

[0071] In addition, the first gripping member 231 c can move toward or away from the second gripping member 231 b under the control of the control device 230 .

[0072] The second conducting member 232A includes a first holding member 232 c and a second holding member 232 b and is located on one end side of the formed material 103 .

[0073] The first gripping member 232c is prismatic and is located on the outer peripheral side of the forming material 103. The first gripping member 232c has a curved surface 2323 in which a portion of the surface on the side in contact with the forming material 103 is curved into a concave shape. The curvature radius of the wall surface forming the curved surface 2323 is preferably larger than the wire diameter of the forming material 103.

[0074] In addition, the first gripping member 232c can move toward or away from the second gripping member 232b under the control of the control device 230.

[0075] Under the control of the control device 230 , energization of the first energizing member 231A and the second energizing member 232A is controlled via a live wire (not shown).

[0076] The control device 230 is disposed at a predetermined position on the shaped material 103, for example, and moves each gripping member of the first energizing member 231A and the second energizing member 232A so that they grip one end and the other end of the shaped material 103, respectively. Thereafter, the control device 230 causes current to flow through the first energizing member 231A and the second energizing member 232A via the live wire. Current flows through the contact portion between the first energizing member 231A and the second energizing member 232A and the shaped material 103. The heat generated at this time is used to heat the shaped material 103.

[0077] In the above-described Modification 1, regardless of the shape of the formed material 103 (coil spring 1), gripping and electrical heating can be performed reliably, as in Embodiment 2. According to Modification 1, a decrease in productivity can be suppressed when manufacturing coil springs of various shapes.

[0078] Furthermore, according to the first modification, the surfaces of the first gripping members 231c and 232c that contact the formed material 103 are respectively formed with concave curved surfaces 2313 and 2323, and the formed material 103 is gripped at each curved surface, so that the formed material 103 can be gripped more reliably.

[0079] Modification 2 of Implementation Example 2

[0080] Next, refer to Figure 8 Modification 2 of Implementation Example 2 is described. Figure 8This is a diagram for explaining the energized heating of Modified Example 2. In Modified Example 2, the structure of the energized component for energized heating is different from that of the energized component of the embodiment. In Modified Example 2, except for the structure of the energized component, the rest is the same as that of the embodiment, so the description is omitted. In addition, Figure 8 In the present invention, the same reference numerals are used to denote the same components as those in the embodiment.

[0081] The first conducting member 231B and the second conducting member 232B of the second modification are similar to those of the embodiment, and the movement of the members (gripping of the formed material 103 ) and the conduction of electricity are controlled by the control device 230 .

[0082] The first conducting member 231B has a first holding member 231 d and a second holding member 231 b and is located on one end side of the forming material 103 .

[0083] The first gripping member 231d is prism-shaped and is located on the outer peripheral side of the forming material 103. The first gripping member 231d has a groove 2314 in which a portion of the surface on the side in contact with the forming material 103 is V-shaped. The formation area (formation width and depth) of the groove 2314 is set to a formation area where the first gripping member 231d and the second gripping member 231b do not contact. In addition, the first gripping member 231d only needs to have a curved surface on the surface in contact with the forming material 103, and the other part may also be cylindrical or other polygonal shapes.

[0084] In addition, the first gripping member 231d can move toward or away from the second gripping member 231b under the control of the control device 230.

[0085] The second conducting member 232B includes a first holding member 232 d and a second holding member 232 b and is located on one end side of the formed material 103 .

[0086] The first gripping member 232d is prism-shaped and is located on the outer peripheral side of the forming material 103. The first gripping member 232d has a groove portion 2324 in which a portion of the surface on the side in contact with the forming material 103 is V-shaped. The formation area (formation width) of the groove portion 2324 is preferably larger than the wire diameter of the forming material 103.

[0087] In addition, the first gripping member 232d can move toward or away from the second gripping member 232b under the control of the control device 230.

[0088] Under the control of the control device 230 , energization of the first energizing member 231B and the second energizing member 232B is controlled via a live wire (not shown).

[0089] The control device 230 is disposed at a predetermined position on the shaped material 103, for example, and moves each gripping member of the first energizing member 231B and the second energizing member 232B so that they grip one end and the other end of the shaped material 103, respectively. Thereafter, the control device 230 causes current to flow through the first energizing member 231B and the second energizing member 232B via the live wire. Current flows through the contact portion between the first energizing member 231B and the second energizing member 232B and the shaped material 103. The heat generated at this time is used to heat the shaped material 103.

[0090] In the above-described second modification, regardless of the shape of the formed material 103 (coil spring 1), gripping and electrical heating can be performed reliably, as in the second embodiment. According to the second modification, a decrease in productivity can be suppressed when manufacturing coil springs of various shapes.

[0091] Furthermore, according to the second modification, grooves 2314 and 2324 are formed on the surfaces of the first gripping members 231d and 232d that come into contact with the shaped material 103, respectively, and the shaped material 103 is gripped at each bending surface, so that the shaped material 103 can be gripped more reliably.

[0092] Implementation 3

[0093] Next, refer to Fig. 9 Embodiment 3 of the present invention will be described. In addition, the coil spring manufactured in this embodiment 3 is Figure 1 The coil spring 1 shown in the figure. Hereinafter, a method for manufacturing a coil spring according to the third embodiment will be described. Figure 2 and Figure 3 The manufacturing method shown is the same, so the description of the manufacturing sequence is omitted. Specifically, in the third embodiment, the heating method during tempering or quenching is different from that in the second embodiment.

[0094] Reference Fig. 9 During the power-on tempering of the third embodiment (see Figure 3 In addition, when the formed material 102 before quenching is electrically heated (see Figure 3 (d)) can also be heated in the same manner.

[0095] Fig. 9 This is a diagram for explaining an example of the change over time of the current value and the temperature of the forming material 103 during electric heating. Fig. 9 In FIG. 1 , the solid line represents the current value, and the dotted line represents the temperature of the formed material 103 . Therefore, the slope of the dotted line represents the temperature increase rate of the formed material 103 .

[0096] The control device 230 is, for example, Fig. 9 The current value is changed in two stages as shown to increase the temperature of the formed material 103. At this time, the control period of the control device 230 is roughly divided into a first power-on period S1 and a second power-on period S2. The first power-on period S1 is a period from the start of power-on to the elapse of a predetermined time when power is supplied at a current value I2, and the second power-on period S2 is a period of power supply at a current value I1 smaller than that of the first power-on period. Fig. 9 In the embodiment, the period from the start of power-on (t0) to time t1 is defined as the first power-on period, and the period from time t1 to time t2 is defined as the second power-on period. During this power-on heating, the temperature rise rate during the second power-on period is lower than the temperature rise rate during the first power-on period, and the temperature of the forming material 103 rises relatively slowly.

[0097] The control device 230 allows a large current to flow during the first power-on period, thereby rapidly raising the temperature to a predetermined temperature T1, i.e., heating (for example, a temperature 50°C lower than the heating end temperature). During the second power-on period, a small current (for example, a current value 1kA lower than the current value during the first power-on period) is used to gradually raise the temperature to the heating end temperature T2, thereby stabilizing the temperature at the end of heating. Fig. 9 The ratio of the heating time between the first energizing period and the second energizing period is about 2: 1. In addition, the set current value and the heating time of each period are determined according to the material diameter or the target heating time.

[0098] Here, the current value I (A) can be set based on the calculation formula shown in the following formula (1). For example, the value obtained by the formula (1) is determined as the current value, or the current value is determined based on the value.

[0099]

[0100] Where S is the cross-sectional area of ​​the formed material 103 (mm 2 ), ΔT is the temperature difference (°C), t is the heating time (sec), and α is a constant.

[0101] In addition, the temperature difference ΔT represents the difference between the temperature of the formed material 103 before the start of heating and the temperature T1, or the difference between the temperature T1 and the temperature T2, and the temperature difference ΔT changes according to each period (the first power-on period S1 or the second power-on period S2). Specifically, the temperature difference ΔT in the first power-on period S1 is the difference between the temperature of the formed material 103 before the start of heating and the temperature T1, and the temperature difference ΔT in the second power-on period S2 is the difference between the temperature T1 and the temperature T2.

[0102] The control device 230 is disposed at a predetermined position on the shaped material 103, and moves the gripping members of the first and second energizing members 231 and 232 so that they grip one end and the other end of the shaped material 103, respectively. Thereafter, the control device 230 causes current to flow through the first energizing member 231 or the second energizing member 232 via the live wire. Current flows through the contact portion between the first and second energizing members 231 and 232 and the shaped material 103. The heat generated at this time is used to heat the shaped material 103.

[0103] By processing the base material 100 according to the above process, Figure 1 The coil spring 1 is shown.

[0104] Here, annealing treatment may be performed before or after the wire drawing process. In addition, if the wire diameter is the designed wire diameter in the state of the base material, the base material 100 may be cold-formed without wire drawing process.

[0105] In the third embodiment of the present invention described above, the tempering treatment for adjusting hardness etc. is performed by electric heating as in the first embodiment, so that the tempering treatment by electric heating can suppress quality variation. In addition, the yield rate can be improved in the manufacture of the coil spring 1.

[0106] However, in the past, when heat treatment is performed by energizing, if the workpiece is to be heated in a short time, the amount of electricity input to the workpiece is large, and even if the energization is stopped at the time when the workpiece reaches the target temperature, the temperature of the workpiece may continue to rise. In this case, there may be deviations in the heating temperature between the workpieces, resulting in deviations in the quality of the produced coil springs. In response to this, in the present embodiment 3, when heat treatment is performed (at least energization tempering is performed here), the current value is changed in two stages, and when the temperature of the formed material 103 approaches the heating end temperature, control is performed to reduce the temperature rise rate. By slowing down the temperature rise before the end of heating, the temperature rise of the formed material 103 after the heating is stopped is suppressed. According to the present embodiment 3, the quality deviation of the coil spring can be reduced.

[0107] Furthermore, according to the third embodiment, by performing the electric tempering, the time required for the tempering can be shortened compared to the case where the tempering is performed using a furnace, and the amount of carbon dioxide emissions can be reduced.

[0108] In addition, the temperature control during the electric heating is not limited to the two-stage current value control shown in the above-mentioned embodiment 3. For example, Fig. 9The example of making the current value as large as possible at the time of the start of power-on is shown in FIG. 1 , but the current value may be gradually increased from the start of power-on. In addition, the current value may be reduced in stages when the current is switched between the first power-on period and the second power-on period. The temperature rise at this time is set according to the beat time of the heating process.

[0109] In addition, the heating temperature can also be adjusted by controlling the current on and off. For example, the on period of the second power-on period is shorter or the off period is longer than that of the first power-on period. In addition, regarding the on and off control of the current, for example, the control method of Japanese Patent No. 6077790 can be used.

[0110] In addition, in the present third embodiment, the structures of the current-carrying members of the modified examples 1 and 2 of the second embodiment may be adopted.

[0111] Although the modes for carrying out the present invention have been described above, the present invention should not be limited to the above-described embodiments.

[0112] Thus, the present invention can include various embodiments and the like that are not described herein, and various design changes and the like can be implemented without departing from the technical concept specified in the claims.

[0113] Industrial Applicability

[0114] As described above, the method for producing a coil spring according to the present invention is suitable for suppressing variations in quality.

[0115] Explanation of symbols:

[0116] 1 Coil spring

[0117] 100 Base material

[0118] 101 Wire drawing

[0119] 102, 103 forming materials

[0120] 200 Winding Machine

[0121] 210, 230 Control device

[0122] 211, 231 First energized component

[0123] 212, 232 Second energized component

[0124] 221 slots

[0125] 222 Water-soluble quenching agent

[0126] 231a, 231c, 231d, 232a, 232c, 232d first gripping member

[0127] 231b, 232b second gripping member

[0128] 2311, 2321 plane part

[0129] 2312, 2322 side

[0130] 2313, 2323 Curved surface

[0131] 2314, 2324 groove parts.

Claims

1. A method for manufacturing a coil spring, which is a method for manufacturing a coil spring by processing a base material formed of a wire, characterized in that: include: A cold forming step of cold forming the base material to produce a spiral shaped material; A quenching step, quenching the formed material; as well as The electric tempering step is to temper the quenched formed material by electric heating.

2. The method for manufacturing a coil spring according to claim 1, characterized in that: Also includes: a step of producing a drawn wire material, wherein the base material is subjected to a wire drawing process to produce the drawn wire material; In the cold forming step, the drawn wire material is cold formed.

3. The method for manufacturing a coil spring according to claim 1 or 2, characterized in that: In the quenching step, the formed material is immersed in a heated water-soluble quenching agent to perform quenching.

4. The method for manufacturing a coil spring according to claim 2, characterized in that: Also includes: The electrical heating step is performed before the quenching step, and the drawn wire material is electrically heated.

5. The method for manufacturing a coil spring according to claim 1, characterized in that: In the power-on tempering step, The first conducting member holding one end of the quenched formed material and the second conducting member holding the other end of the quenched formed material hold both ends of the formed material, and current is applied thereto. The first current-carrying component and the second current-carrying component grip the shaped material through a first gripping component and a second gripping component. The first gripping component is located on the outer peripheral side of the shaped material, and the second gripping component is located on the inner peripheral side of the shaped material and clamps the shaped material together with the first gripping component. The curvature radius of the surface of the second gripping component in contact with the shaped material is smaller than the curvature radius of the inner periphery of the shaped material, and the second gripping component clamps the shaped material together with the first gripping component.

6. The method for manufacturing a coil spring according to claim 5, characterized in that: The first gripping member has a planar portion provided on a surface in contact with the forming material. In the electrical tempering step, the formed material is gripped by the flat surface portion of the first gripping member and the outer peripheral curved surface of the second gripping member, and the formed material is electrically heated.

7. The method for manufacturing a coil spring according to claim 5, characterized in that: The first gripping member has a curved surface that is curved into a concave shape, the curved surface is provided on a surface that contacts the shaped material, and a curvature radius of the curved surface is greater than a wire diameter of the shaped material. In the electrical tempering step, the shaped material is gripped by the curved surface of the first gripping member and the outer peripheral curved surface of the second gripping member, and the shaped material is electrically heated.

8. The method for manufacturing a coil spring according to claim 5, characterized in that: The first gripping member has a groove portion, which is provided on a surface in contact with the forming material and is in a V-shaped groove shape. In the electrical tempering step, the formed material is gripped by the groove portion of the first gripping member and the outer peripheral curved surface of the second gripping member, and the formed material is electrically heated.

9. The method for manufacturing a coil spring according to claim 5, characterized in that: In the electric tempering step, the formed material is heated by changing the temperature increase rate in stages.

10. The method for manufacturing a coil spring according to claim 5, characterized in that: Also includes: The electrical heating step is performed before the quenching step, and the cold-formed formed material is electrically heated.

11. The method for manufacturing a coil spring according to claim 1, characterized in that: In the power-on tempering step, A first power-on period and a second power-on period are set, wherein the first power-on period is from when the heating of the forming material starts to the time when a predetermined time has passed, and the second power-on period is from when the predetermined time has passed to when the heating ends. The temperature increase rate of the formed material in the second energization period is lower than the temperature increase rate of the formed material in the first energization period.

12. The method for manufacturing a coil spring according to claim 11, characterized in that: In the energization tempering step, the current value in the second energization period is made smaller than the current value in the first energization period.

13. The method for manufacturing a coil spring according to claim 11, characterized in that: In the power-on tempering step, The first conducting member holding one end of the quenched formed material and the second conducting member holding the other end of the quenched formed material hold both ends of the formed material, and current is applied thereto. The first current-carrying component and the second current-carrying component grip the shaped material through a first gripping component and a second gripping component. The first gripping component is located on the outer peripheral side of the shaped material, and the second gripping component is located on the inner peripheral side of the shaped material and clamps the shaped material together with the first gripping component. The curvature radius of the surface of the second gripping component in contact with the shaped material is smaller than the curvature radius of the inner periphery of the shaped material, and the second gripping component clamps the shaped material together with the first gripping component.

14. The method for manufacturing a coil spring according to claim 11, characterized in that: Also includes: The electrical heating step is performed before the quenching step, and the cold-formed formed material is electrically heated.

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