Method for manufacturing spring member and control device

Abstract

A method for manufacturing a spring member according to the present invention includes: a cold forming step for performing cold forming on a base material to fabricate a spiral molding material; a quenching step for performing quenching on the molding material; and a tempering step for performing tempering on the quenched molding material. During the heating in at least one of the quenching and the tempering, the molding material is energized and heated by energizing a first energization member and a second energization member in a state where both ends of the molding material are held by the first energization member and the second energization member, wherein, in each energization member, energization is performed by setting the current ratio R2, which is the ratio of a current that flows through one holding member to the sum of currents that flow through the energizing members, to a value in the vicinity of the contact area ratio R1, including the contact area ratio R1, which is the ratio of the area of contact of one holding member with the molding material to the sum of the areas of contact of the molding material and the holding members in the energizing members.

Description

Method for manufacturing spring member and control device

[0001] The present invention relates to a method for manufacturing a spring member and a control device.

[0002] Conventionally, hot forming and cold forming are employed in the process of manufacturing coil springs. Of these, hot forming allows for the formation of thick wire rods, but has limited flexibility in the shape of the formed wire. On the other hand, cold forming allows for a high degree of freedom in the shape of the formed wire, but has difficulty in forming thick wire rods. A technique that allows for a high degree of freedom in the shape and for forming thick wire rods is known in which the wire rod is cold formed and then heat treated, such as quenched and tempered (see, for example, Patent Document 1). In Patent Document 1, heat treatment is performed by attaching electrodes to both ends of the coil-shaped formed product (workpiece) after cold forming and passing electricity through them.

[0003] Patent No. 5574772

[0004] However, when attempting to heat a workpiece in a short period of time during heat treatment by passing current, the amount of power input to the workpiece increases, and even if the current is stopped when the workpiece reaches the target temperature, the temperature of the low-temperature part of the workpiece may rise due to heat transfer from the high-temperature part. In this case, the heating temperature may vary between workpieces, or the heat distribution in the workpiece may vary, which may result in variation in the quality of the produced coil springs.

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide a method for manufacturing a spring member and a control device that can reduce variations in the quality of spring members.

[0006] In order to solve the above-mentioned problems and achieve the object, a method for manufacturing a spring member according to the present invention is a method for manufacturing a spring member by processing a base material made of a wire, and includes 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 a tempering step of tempering the quenched formed material, and in heating in at least one of the quenching step and the tempering step, a first current-carrying member that clamps and holds one end of the formed material between a pair of holding members, and The formed material is heated by passing current through the first and second current-carrying members while both ends of the formed material are held by a pair of gripping members, and the other end of the formed material is held by a pair of gripping members, and the current ratio R2, which is the ratio of the current flowing through one gripping member to the sum of the currents flowing through the current-carrying members, is set to a value close to the contact area ratio R1, which is the ratio of the contact area of ​​one gripping member with the formed material to the sum of the contact areas of the formed material and the gripping members on the current-carrying members, and current is passed through the current ratio R2.

[0007] Furthermore, in the method for manufacturing a spring member according to the present invention, in the above invention, current is passed by setting the current ratio R2 within the range of the contact area ratio R1 ±0.1.

[0008] In addition, the method for manufacturing a spring member according to the present invention is characterized in that, in the above invention, cooling water is circulated inside the current-carrying member.

[0009] The control device according to the present invention is a control device for controlling the manufacture of a spring member, the control device including a cold forming step of cold forming a base material made of a wire to produce a spiral formed material, a quenching step of quenching the formed material, and a tempering step of tempering the formed material after quenching, the control device including a first current-carrying member that holds one end of the formed material by a pair of holding members, and a second current-carrying member that holds the formed material by a pair of holding members, the first current-carrying member that holds the formed material by a pair of holding members, and the second current-carrying member that holds the formed material by a pair of holding members. The other end of the formed material is clamped by a pair of gripping members, and current is passed through the first and second current-carrying members while both ends of the formed material are gripped by a second current-carrying member which clamps and holds the other end of the formed material, and in each current-carrying member, a current ratio R2 which is the ratio of the current flowing through one of the gripping members to the sum of the currents flowing through the current-carrying member is set to a value close to and including a contact area ratio R1 which is the ratio of the contact area of ​​the one gripping member with the formed material to the sum of the contact areas of the formed material and the gripping members in the current-carrying member.

[0010] According to the present invention, it is possible to reduce variations in the quality of spring members.

[0011] FIG. 1 is a diagram illustrating the configuration of a coil spring manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a manufacturing method of a coil spring according to an embodiment of the present invention. FIG. 3 is a diagram illustrating electrical heating. FIG. 4 is a diagram viewed from the direction of arrow A shown in FIG. 3. FIG. 5 is a diagram (part 1) illustrating setting of a current ratio during electrical heating. FIG. 6 is a diagram (part 2) illustrating setting of a current ratio during electrical heating. FIG. 7 is a diagram (part 3) illustrating setting of a current ratio during electrical heating. FIG. 8 is a diagram illustrating electrical heating according to Modification 1. FIG. 9 is a diagram illustrating electrical heating according to Modification 2. FIG. 10 is a diagram illustrating electrical heating according to Modification 3. FIG. 11 is a cross-sectional view taken along line A-A shown in FIG. 10. FIG. 12 is a diagram illustrating electrical heating according to Modification 4.

[0012] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying 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 also include parts with different dimensional relationships and ratios.

[0013] (Embodiment) This figure shows the structure of a coil spring manufactured by a manufacturing method according to one embodiment of the present invention. The coil spring 1 is manufactured by spirally winding a wire material. The coil spring 1 is manufactured using a wire material made of, for example, a metal or alloy.

[0014] Next, a method for manufacturing the coil spring 1 will be described with reference to Figures 2 to 4. Figure 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 manufactured by processing a base material.

[0015] First, a base material 100 (see FIG. 2(a)) made of a wire is subjected to a wire drawing process to obtain a drawn wire material 101 (see FIG. 2(b)). At this time, the base 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 by, for example, passing it through a die, thereby obtaining a wire material (drawn wire material 101) with a designed diameter.

[0016] 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. This 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.

[0017] The formed material 102 obtained by winding and cutting the drawn wire material 101 is subjected to electrical heating (see (d) of FIG. 2). In electrical heating, a first current-carrying member 211 is attached to one end of the formed material 102, and a second current-carrying member 212 is attached to the other end, and current is passed through the first current-carrying member 211 and the second current-carrying member 212. 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 made of a conductive material, and the movement of the members (gripping of the formed material 102) and the current flow are controlled under the control of a control device 210.

[0018] 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 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 water or oil may be used instead of the water-soluble quenchant 222.

[0019] After quenching, the formed material 103 is subjected to electrical heating (electrical tempering) for tempering (see (f) in FIG. 2). In electrical tempering, a first electrical conducting member 231 is attached to one end of the formed material 103, and a second electrical conducting member 232 is attached to the other end, and electrical current is passed through the first electrical conducting member 231 and the second electrical conducting member 232. This electrical conduction generates heat, which heats the formed material 103. In electrical tempering, electrical conduction conditions are set for reheating the formed material 103 to a predetermined hardness. The first electrical conducting member 231 and the second electrical conducting member 232 are controlled by the control device 230, which controls the movement of the members (gripping of the formed material 103) and the electrical current.

[0020] Here, the control of the electrical heating will be described with reference to Figures 3 to 5. The electrical heating control described here can be used in at least one of the following cases: when electrical heating is performed on the formed material 102 before quenching (see Figure 2(d)), and when electrical heating is performed on the formed material 103 during tempering (see Figure 2(f)). Here, the control used during tempering (see Figure 2(f)) will be described as an example.

[0021] Fig. 3 is a diagram for explaining the electrical heating. Fig. 4 is a diagram seen from the direction of arrow A shown in Fig. 3. The first electrical conducting member 231 has a first gripping member 231a and a second gripping member 231b, and is located on one end side of the formed material 103.

[0022] The first gripping member 231a has a rectangular columnar shape and is located on the outer periphery of the formed material 103. The first gripping member 231a has a flat portion 2311, the surface of which contacts the formed material 103. The first gripping member 231a may have a cylindrical shape or another polygonal shape. The surface of the first gripping member 231a which contacts the formed material 103 may also have a curved shape.

[0023] The second gripping member 231b is cylindrical and located on the inner periphery of the molded material 103. In this case, by making the radius of curvature of the side surface (outer periphery) of the second gripping member 231b smaller than the radius of curvature of the inner periphery of the applicable molded material 103, the second gripping member 231b can be applied to various types of 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 of the molded material 103 (the winding axial direction). Note that as long as the surface of the second gripping member 231b that contacts the molded material 103 is curved, other portions may be polygonal.

[0024] Under the control of the control device 230, power is transmitted to the first gripping member 231a and the second gripping member 231b via a power transmission line (not shown). The first gripping member 231a is movable toward or away from the second gripping member 231b under the control of the control device 230. The second gripping member 231b is movable toward or away from the first gripping member 231a under the control of the control device 230. The second gripping member 231b may be configured to be movable toward the first gripping member 231a in order to correspond to the winding diameter of the formed material 103, or the first current-carrying member 231 and the second current-carrying member 232 may be configured to be movable toward or away from each other in order to correspond to the number of turns of the formed material 103, etc.

[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 molded material 103. The first gripping member 232a is prismatic 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 is cylindrical and is located on the inner periphery side of the molded material 103. The first gripping member 232a and the second gripping member 232b of the second current-carrying member 232 can have the same configuration as the first gripping member 231a and the second gripping member 231b of the first current-carrying member 231.

[0026] The first current-carrying member 231 and the second current-carrying member 232 are controlled to be energized via power lines (not shown) under the control of the control device 230. 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, for example, places the formed material 103 at a predetermined position and moves the gripping members of the first and second current-carrying members 231 and 232 to grip one end and the other end of the formed material 103, respectively. Thereafter, the control device 230 passes current through the first and second current-carrying members 231 and 232 via the power transmission lines. Current flows between the first and second current-carrying members 231 and 232 and the formed material 103 through the contact points. The heat generated at this time heats the formed material 103.

[0028] Here, the control of heating will be described with reference to Figures 5 to 7. Figures 5 to 7 are diagrams for explaining the setting of the current ratio during electrical heating, in which the first electrical conducting member 231 and the second electrical conducting member 232 have different contact area ratios.

[0029] The current ratio is calculated by integrating the resistance values ​​along the current transmission path. The current ratio here is the ratio of the current flowing through one of the current-carrying members (here, the second gripping member 232b) to the sum of the currents flowing through the first gripping member 232a and the second gripping member 232b. Specifically, the current ratio is the ratio (current side / total input) of the current flowing through the inner diameter gripping member (current side) to the sum of the currents flowing through the current-carrying members (total input). In the case of the second gripping member 232b, the ratio is (current flowing through the second gripping member 232b) / (sum of the currents flowing through the second gripping member 232b). The contact area ratio is the proportion of the contact area of ​​the gripping member with the molded material, calculated based on the shape of the gripping member and the shape of the molded material. This contact area ratio is the ratio of the contact area of ​​one gripping member (here, second gripping member 232b) to the sum of the contact area of ​​the gripping member with the formed material 103 and the contact area of ​​the other gripping member (here, first gripping member 232a) with the formed material 103. Note that while the above ratios have been described for the second gripping member 232b of the second current-carrying member, it is preferable that the contact area ratio and current ratio are similarly uniform for the second gripping member 231b of the first current-carrying member. In this case, "uniform" includes errors in material and manufacturing.

[0030] Figure 5 shows the case where the contact area ratio is 0.35, and shows curves showing the relationship between the temperature of the first contact portion and the second contact portion versus the current ratio, and the relationship between the current ratio and temperature on the outer diameter side / inner diameter side of the formed material 103 at 0.2 turns. Here, the first contact portion refers to the portion of the formed material 103 where the first gripping member 232a contacts, and the second contact portion refers to the portion of the formed material 103 where the second gripping member 232b contacts. The contact position of each contact portion with the formed material 103 was 0.08 turns. In Figure 5, curve L1 shows the relationship between the current ratio and the temperature of the first contact portion, and is an approximation curve for the temperature measurement points (plot: square) at each current ratio. Curve L2 shows the relationship between the current ratio and the temperature of the second contact portion, and is an approximation curve for the temperature measurement points (plot: circle) at each current ratio.

[0031] 5, curve L3 shows the relationship between the current ratio and temperature on the outer diameter side of the 0.2 turn of the formed material 103, and is an approximation curve for the measurement points (plot: ◇) of the temperature versus the current ratio. Curve L4 shows the relationship between the current ratio and temperature on the inner diameter side of the 0.2 turn of the formed material 103, and is an approximation curve for the measurement points (plot: ×) of the temperature versus the current ratio.

[0032] In this case, it can be seen from curves L1 and L2 that the temperatures of the first and second contact portions become the same when the current ratio is approximately the same as the contact area ratio of 0.35. In other words, by making the contact area ratio and the current ratio the same, the temperatures of the first and second contact portions can be made uniform when the first gripping member 232a and the second gripping member 232b are gripped and electrically heated.

[0033] Furthermore, it can be seen that in the formed material 103, at the 0.2 turn away from the contact position with the gripping member (first and second contact portions), the temperature is almost constant regardless of the current ratio.

[0034] 6 shows the relationship between the temperature of the first contact portion and the temperature of the second contact portion and the current ratio when the contact area ratio is 0.5. 11 is a curve showing the relationship between the current ratio and the temperature of the first contact portion, and is an approximation curve for the measurement points (plot: square) of the temperature of the first contact portion at each current ratio. 12 is a curve showing the relationship between the current ratio and the temperature of the second contact portion, and is an approximation curve for the measurement points (plot: O) of the temperature of the second contact portion at each current ratio.

[0035] 7 shows the relationship between the temperature of the first contact portion and the temperature of the second contact portion and the current ratio when the contact area ratio is 0.6. 21 is a curve showing the relationship between the current ratio and the temperature of the first contact portion, and is an approximation curve for the measurement points (plot: square) of the temperature of the first contact portion at each current ratio. 22 is a curve showing the relationship between the current ratio and the temperature of the second contact portion, and is an approximation curve for the measurement points (plot: O) of the temperature of the second contact portion at each current ratio.

[0036] 6 and 7, it can be seen that the intersection of the curves is approximately the same as the contact area ratio. In other words, by making the contact area ratio and the current ratio the same regardless of the contact area ratio, it can be said that when the formed material 103 is held between the first gripping member 232a and the second gripping member 232b and heated by electrical current, the temperatures of the first and second contact portions of the formed material 103 can be made uniform.

[0037] The current ratio may be in the vicinity of the contact area ratio, including being the same as the contact area ratio. Specifically, the current ratio may be in the range R of ±0.1 of the contact area ratio, including being the same as the contact area ratio. A By setting a value within this range, it is possible to make the temperatures of the first contact portion and the second contact portion of the formed material 103 uniform. For example, with respect to the contact area ratio R1 of the gripping member, the current ratio R2, which is the ratio of the current flowing through the gripping member to the sum of the currents flowing through the current-carrying members, can be set within the range of R1 ± 0.1.

[0038] The coil spring 1 shown in Fig. 1 is produced by processing the base material 100 according to the above-described process. Here, annealing may be performed before or after the wire drawing process. Also, if the wire diameter of the base material is as designed, it is possible to perform cold forming on the base material 100 without performing wire drawing.

[0039] In the embodiment of the present invention described above, electrical heating is performed so that the contact area ratio of the gripping members that grip the formed material to the formed material is the same as the current ratio of the current passed through the gripping members, so the entire formed material can be heated to a uniform temperature. According to this embodiment, quenching / tempering through uniform heating improves the shape accuracy of the coil spring, and improved shape accuracy improves yield, thereby reducing variation in the quality of the coil springs.

[0040] Furthermore, according to this embodiment, CO2 emissions can be reduced by employing electrical heating for quenching / tempering.

[0041] (Modification 1) Next, Modification 1 of the present embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining electrical heating according to Modification 1. In Modification 1, the configuration of the current-carrying member that performs electrical heating is different from the current-carrying member according to the embodiment. Since Modification 1 is the same as the embodiment except for the configuration of the current-carrying member, a description thereof will be omitted. Note that in Fig. 8, the same components as those in the embodiment are assigned the same reference numerals.

[0042] The movement of the first current-carrying member 231A and the second current-carrying member 232A according to the first modification (gripping of the formed material 103) and the energization of the members are controlled under the control of the control device 230, as in the embodiment.

[0043] 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 formed material 103. The first gripping member 231c is prismatic and located on the outer periphery of the formed material 103. The first gripping member 231c has a curved surface 2312, where a portion of the surface that contacts the formed material 103 is concavely curved. The radius of curvature of the wall surface that forms this curved surface 2312 is preferably larger than the wire diameter of the formed material 103. Note that as long as the surface that contacts the formed material 103 has the above-mentioned shape, other portions of the first gripping member 231c may be cylindrical or have another polygonal shape. Furthermore, the first gripping member 231c can be moved toward or away from the second gripping member 231b under the control of the control device 230.

[0044] The second current-carrying member 232A has a first gripping member 232c and a second gripping member 232b, and is located on the other end side of the formed material 103. The first gripping member 232c is shaped like a rectangular pillar and is located on the outer periphery of the formed material 103. The first gripping member 232c has a curved surface 2322, where a portion of the surface that comes into contact with the formed 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 formed material 103. Furthermore, the first gripping member 232c can be moved toward or away from the second gripping member 232b under the control of the control device 230.

[0045] The first current-carrying member 231A and the second current-carrying member 232A are controlled to be energized via a power transmission line (not shown) under the control of the control device 230. At this time, as in the embodiment, the contact area ratio and the current ratio are controlled to be the same.

[0046] For example, the control device 230 places the formed material 103 at a predetermined position and moves the gripping members of the first and second current-carrying members 231A and 232A to grip one end and the other end of the formed material 103, respectively. The control device 230 then applies current to the first and second current-carrying members 231A and 232A via the power transmission lines. 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.

[0047] In the first modification described above, similar to the embodiment, the current ratio of the current flowing through the gripping members to the formed material is equal to the contact area ratio of the gripping members to the formed material, so that the entire formed material can be heated to a uniform temperature. This first modification can reduce variation in the quality of coil springs.

[0048] Furthermore, according to this modified example 1, the first gripping members 231c, 232c each have a concave curved surface 2312, 2322 formed on the surface that comes into contact with the molded material 103, and the molded material 103 is gripped by each curved surface, thereby enabling the molded material 103 to be gripped more reliably.

[0049] (Modification 2) Next, Modification 2 of the present embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram for explaining electrical heating according to Modification 2. In Modification 2, the configuration of the current-carrying member that performs electrical heating is different from the current-carrying member according to the embodiment. Since Modification 2 is the same as the embodiment except for the configuration of the current-carrying member, a description thereof will be omitted. Note that in Fig. 9, the same components as those in the embodiment are assigned the same reference numerals.

[0050] The movement of the first current-carrying member 231B and the second current-carrying member 232B according to the second modification (gripping of the formed material 103) and the energization of the members are controlled under the control of the control device 230, as in the embodiment.

[0051] The first current-carrying member 231B has a first gripping member 231d and a second gripping member 231b and is located on one end of the formed material 103. The first gripping member 231d is prismatic and located on the outer periphery of the formed material 103. The first gripping member 231d has a V-shaped groove 2313 on a portion of its surface that contacts the formed material 103. The formation area (forming width and depth) of this groove 2313 is set so that the first gripping member 231d and the second gripping member 231b do not come into contact with each other. Note that as long as the surface that contacts the formed material 103 has the above-mentioned shape, other portions of the first gripping member 231d may be cylindrical or have another polygonal shape. Furthermore, the first gripping member 231d can be moved toward or away from the second gripping member 231b under the control of the control device 230.

[0052] The second current-carrying member 232B has a first gripping member 232d and a second gripping member 232b, and is located on the other end side of the formed material 103. The first gripping member 232d has a rectangular column shape and is located on the outer periphery of the formed material 103. The first gripping member 232d has a groove portion 2323 in the form of a V-shaped groove on a portion of the surface that comes into contact with the formed material 103. The formation area (forming width) of this groove portion 2323 is preferably larger than the wire diameter of the formed material 103. Furthermore, the first gripping member 232d can be moved toward or away from the second gripping member 232b under the control of the control device 230.

[0053] The first current-carrying member 231B and the second current-carrying member 232B are controlled by the control device 230 via a power transmission line (not shown). As in the embodiment, the contact area ratio and the current ratio are controlled to be the same. The contact area ratio is the sum of the area ratios at multiple points where the gripping members contact the molding material.

[0054] 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 231B and 232B. The control device 230 then applies current to the first and second current-carrying members 231B and 232B via the power transmission lines. Current flows between the first and second current-carrying members 231B and 232B and the formed material 103 through the contact points. The heat generated at this time heats the formed material 103.

[0055] In the second modification described above, similar to the embodiment, the current ratio of the contact area between the gripping members gripping the formed material and the formed material is equal to the current ratio of the current flowing through the gripping members, so that the entire formed material can be heated to a uniform temperature. According to the second modification, it is possible to reduce the variation in the quality of the coil springs.

[0056] Furthermore, according to this modified example 2, grooves 2313 and 2323 are formed on the surfaces of the first gripping members 231d and 232d that come into contact with the molded material 103, respectively, so that the molded material 103 is gripped on each curved surface, thereby enabling the molded material 103 to be gripped more reliably.

[0057] (Variation 3) Next, Variation 3 of the present embodiment will be described with reference to Figs. 10 and 11. Fig. 10 is a diagram for explaining electrical heating according to Variation 3. Fig. 11 is a cross-sectional view taken along line A-A in Fig. 10. Fig. 10 corresponds to a view seen from the direction of arrow A in Fig. 3. Fig. 11 is a cross-sectional view taken along a plane parallel to the winding axis of the formed material 103. In Variation 3, the configuration of the current-carrying member that performs electrical heating is different from the current-carrying member according to the embodiment. Variation 3 is the same as the embodiment except for the configuration of the current-carrying member, and therefore description thereof will be omitted.

[0058] As in the embodiment, the movement of the first current-carrying member 231C according to the third modification (gripping of the formed material 103) and the current flow are controlled under the control of the control device 230. Note that a similar configuration can also be adopted for the second current-carrying member.

[0059] The first current-carrying member 231C includes a first gripping member having a first member 231e and a second member 231f, and a second gripping member 231g, and is located at one end of the formed material 103. The first member 231e and the second member 231f are each prismatic and arranged side by side along the axial direction of the winding of the formed material 103, contacting the same winding position of the formed material 103. The first current-carrying member 231C according to the third modification has multiple (here, two) contact points on the outer periphery that contact the same winding of the formed material. Here, the contact points are not limited to the same winding and may be located at slightly separated positions. Furthermore, the first gripping member can be moved toward or away from the second gripping member 231g under the control of the control device 230.

[0060] The second gripping member 231g has a cylindrical shape and is located on the inner periphery side of the formed material 103. The second gripping member 231g may have a polygonal shape.

[0061] The control device 230 controls the current supply to the first current-carrying member 231C via a power line (not shown). As in the embodiment, the control is performed so that the contact area and the current ratio are the same. The contact area is the sum of the areas of the contact points between the first member 231e and the molding material 103 and the second member 231f.

[0062] 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 231C and 231C, respectively. The control device 230 then applies current to the first and second current-carrying members 231C and 231C via the power transmission lines. Current flows between the first and second current-carrying members 231C and 231C and the formed material 103 through the contact points. The heat generated at this time heats the formed material 103.

[0063] In the third modification described above, similar to the embodiment, the current ratio of the current flowing through the gripping members to the formed material is equal to the contact area ratio of the gripping members to the formed material, so that the entire formed material can be heated to a uniform temperature. According to the third modification, it is possible to reduce the variation in the quality of the coil springs.

[0064] (Modification 4) Next, Modification 4 of the present embodiment will be described with reference to Fig. 12. Fig. 12 is a diagram for explaining electrical heating according to Modification 4. In Modification 4, a water-cooling structure is provided inside the current-carrying member according to the embodiment. Since Modification 4 is the same as the embodiment except for the structure of the current-carrying member, a description thereof will be omitted. Note that in Fig. 12, the same components as those in the embodiment are assigned the same reference numerals.

[0065] As in the embodiment, the movement of the first current-carrying member according to the fourth modification (gripping of the formed material 103) and the current flow therethrough are controlled under the control of the control device 230. Note that a similar configuration can also be adopted for the second current-carrying member.

[0066] The first current-carrying member according to the fourth modification includes a first gripping member 231h and a second gripping member 231i, and is located on one end of the formed material 103. The first gripping member 231h has a hollow rectangular column shape and is located on the outer periphery of the formed material 103. A bottomed hollow space 2340 is formed in the first gripping member 231h. A pipe 2341 is provided in this hollow space 2340. In the fourth modification, cooling water for cooling the first gripping member 231h flows from the outside into the pipe 2341, and the cooling water discharged outside the pipe 2341 passes through the hollow space 2340 outside the pipe 2341 and is sent to the outside of the first gripping member 231h. Furthermore, the first gripping member 231h can be moved toward or away from the second gripping member 231i under the control of the control device 230.

[0067] The second gripping member 231i has a hollow rectangular column shape and is located on the outer periphery of the molding material 103. A bottomed hollow space 2350 is formed in the second gripping member 231i. A pipe 2351 is provided in this hollow space 2350. In this fourth modification, cooling water for cooling the second gripping member 231i is circulated from the outside into the pipe 2351, and the cooling water discharged outside the pipe 2351 passes through the hollow space 2350 outside the pipe 2351 and is sent to the outside of the second gripping member 231i.

[0068] The first current-carrying member according to the fourth modification is controlled by the control device 230 via a power transmission line (not shown). In this case, the control is performed so that the contact area and the current ratio are the same, as in the embodiment.

[0069] The control device 230, for example, places the formed material 103 at a predetermined position and moves the gripping members of the first and second current-carrying members to grip one end and the other end of the formed material 103, respectively. The control device 230 then applies current to the first and second current-carrying members via the power transmission lines. Current flows between the first and second current-carrying members and the formed material 103 through the contact points. The heat generated at this time heats the formed material 103.

[0070] In the fourth modification described above, similar to the embodiment, the current ratio of the contact area between the gripping members gripping the formed material and the formed material is equal to the current ratio of the current flowing through the gripping members, so that the entire formed material can be heated to a uniform temperature. According to the fourth modification, it is possible to reduce the variation in the quality of the coil springs.

[0071] Furthermore, according to this variant example 4, cooling water is circulated inside the first gripping member 231h and the second gripping member 232i, so that the temperature to which the molding material 103 is heated can be adjusted and damage to the gripping members due to heat can be suppressed.

[0072] Although the embodiments for carrying out the present invention have been described above, the present invention should not be limited to only the above-described embodiments. For example, the first and second current-carrying members that grip the ends of the formed material may be configured in a suitable combination of the current-carrying members according to the embodiments and modifications.

[0073] As described above, the present invention can include various embodiments not described herein, and various design changes can be made without departing from the technical concept defined by the claims. Note that, although the above-described embodiment has been described with respect to heating in the manufacture of a coil spring, the present invention can also be applied to heating in the manufacture of other spring members such as stabilizers, for example.

[0074] As described above, the method for manufacturing a spring member and the control device according to the present invention are suitable for suppressing variations in the quality of spring members.

[0075] 1 Coil spring 100 Base material 101 Drawn wire material 102, 103 Formed material 200 Winding machine 210, 230 Control device 211, 231, 231A to 231C First current-carrying member 212, 232, 232A, 232B Second current-carrying member 221 Tank 222 Water-soluble quenching agent 231a, 231c, 231d, 232a, 232c, 232d, 231h First gripping member 231b, 231g, 232b, 231i Second gripping member 231e First member 231f Second member 2311, 2321 Flat portion 2312, 2322 Curved surface 2313, 2323 Groove portion 2340, 2350 Hollow space 2341, 2351 Pipe

Claims

1. A method for manufacturing a spring member by processing a base material made of wire, comprising: 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 a tempering step of tempering the formed material after quenching, wherein in heating in at least one of the quenching step and the tempering step, the formed material is electrically heated by passing current through the first and second current carrying members in a state in which both ends of the formed material are held by a first current carrying member that holds one end of the formed material by a pair of holding members and a second current carrying member that holds the other end of the formed material by a pair of holding members, a current ratio R2, which is the ratio of the current flowing through one of the gripping members to the sum of the currents flowing through the current-carrying members, is set to a value close to the contact area ratio R1, which is the ratio of the contact area of ​​the one of the gripping members with the formed material to the sum of the contact areas of the formed material and the gripping members in the current-carrying members, and current is applied.

2. The method for manufacturing a spring member according to claim 1, characterized in that the current is passed by setting the current ratio R2 within the range of the contact area ratio R1 ±0.

1.

3. The method for manufacturing a spring member according to claim 1, characterized in that cooling water is circulated inside the current-carrying member.

4. A control device for controlling the manufacture of a spring member, the control device including a cold forming step of cold forming a base material made of wire to produce a spirally formed material, a quenching step of quenching the formed material, and a tempering step of tempering the quenched formed material, wherein in the heating in at least one of the quenching step and the tempering step, current is passed through the first and second current carrying members in a state in which both ends of the formed material are held by a first current carrying member which holds one end of the formed material by a pair of holding members and a second current carrying member which holds the other end of the formed material by a pair of holding members, a current ratio R2, which is the ratio of the current flowing through one of the gripping members to the sum of the currents flowing through the current-carrying members, is set to a value close to the contact area ratio R1, which is the ratio of the contact area of ​​the one of the gripping members with the formed material to the sum of the contact areas of the formed material and the gripping members in the current-carrying members.

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