Coiling machine and method for manufacturing coil springs

Abstract

To improve manufacturing efficiency of a coil spring and manufacture a coil spring with a good shape.SOLUTION: A coiling machine includes: a laser heating machine for heating part of a wire by radiating a laser beam to the wire formed spirally; and a cut-off unit for cutting off the portion of the wire heated by the irradiation of the laser beam. The output density of the laser beam is 10 W / mm2 to 100 W / mm2.SELECTED DRAWING: Figure 19

Description

[Technical Field]

[0001] The present invention relates to a coiling machine for manufacturing coil springs and a method for manufacturing coil springs. [Background technology]

[0002] As an apparatus for manufacturing coil springs, for example, the coil spring forming machine described in Patent Document 1 is known. This coil spring forming machine pre-calculates the position of the cutting site based on the length of the wire to be formed in a spiral shape, and cuts the wire while the cutting site is softened by high-frequency heating.

[0003] On the other hand, coiling machines that cut spirally formed wires with laser light are also known, such as the spring manufacturing apparatus described in Patent Document 2.

[0004] When high-frequency heating is used, as in the coil spring forming machine described in Patent Document 1, the response of heating at the cutting site is poor. Moreover, in this coil spring forming machine, the wire is cut while the cutting site is continuously heated by high-frequency heating, so the material used for cutting may be affected by the high-frequency heating. Furthermore, in this coil spring forming machine, the insufficient response of high-frequency heating and the fact that the wire is coiled while partially heated may make it difficult to maintain a consistent spring forming accuracy.

[0005] On the other hand, the spring manufacturing apparatus described in Patent Document 2 requires a high-power laser beam capable of cutting the wire. In this case, sputtering may occur due to the irradiation of the laser beam, and since the laser beam may irradiate not only the wire but also various parts of the spring manufacturing apparatus, countermeasures must be taken to address these issues.

[0006] In response to this, the applicant of the present application proposes a method, as described in Patent Document 3, of cutting a portion of a wire heated by laser light with a cutting tool such as a cutter. This method makes it possible to easily cut the wire and obtain a coil spring with a good cut surface. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 62-50028 [Patent Document 2] Japanese Patent Application Publication No. 6-218476 [Patent Document 3] Patent No. 7066880 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, there is room for various improvements in the method of cutting a wire heated by laser light with a cutting tool. For example, the irradiation conditions of the laser light on the wire need to be appropriately determined so that the wire is heated to a temperature suitable for cutting and the cross-section of the wire after cutting has a good shape.

[0009] One of the objectives of this invention is to provide a coiling machine and a method for manufacturing coil springs that can improve the manufacturing efficiency of coil springs and produce coil springs with good shape. [Means for solving the problem]

[0010] The coiling machine according to the present invention forms a spiral shape metal For wire , so that the wire does not protrude The wire is heated by irradiating it with laser light. This forms a heated area that includes a molten pool and a heat-affected zone located around the molten pool, where the properties of the wire base material have changed. A laser heating machine, The device includes a mandrel that supports the inner circumferential surface of the wire which is formed into a spiral shape, and a cutter that protrudes from the end of the mandrel and descends toward the outer circumferential surface of the wire, and the cutter applies an impact to the heated area by The system comprises a cutting unit for cutting the aforementioned wire, The diameter of the wire is 8 mm or more and 18 mm or less, and the area of ​​the irradiation region defined by the full width at half maximum of the output distribution of the laser light on the surface of the wire when viewed in the direction of irradiation of the laser light is 16 mm². 2 and 108mm or more 2 The following conditions apply, and the output of the laser light is 500W or more and 8000W or less. The This is the value obtained by dividing the output by the area of ​​the irradiation region. output density of the laser light is 10 W / mm 2 or more and 100 W / mm 2 or less.

[0011] In addition, the method for manufacturing a coil spring according to the present invention includes heating the wire by irradiating the wire, which is formed in a spiral shape, with laser light, and cutting the wire. metal with respect to the , so that the wire does not protrude laser light, and cutting the wire. The process involves forming a heating area that includes a molten pool and a heat-affected zone located around the molten pool, where the properties of the wire's base material have changed, and supporting the inner circumferential surface of the spirally formed wire with a mandrel, and lowering a cutter toward the outer circumferential surface of the wire protruding from the end of the mandrel to apply impact to the heating area. The diameter of the wire is 8 mm or more and 18 mm or less, and the area of ​​the irradiation region defined by the full width at half maximum of the output distribution of the laser light on the surface of the wire when viewed in the direction of irradiation of the laser light is 16 mm². 2 and 108mm or more 2 The following conditions apply: the output of the laser light is 500W or more and 8000W or less, and the output of the laser light is the value obtained by dividing the area of ​​the irradiation region by the area of ​​the irradiation region. The output density is 10 W / mm 2 or more and 100 W / mm 2 or less.

[0012] In each of the coiling machine and the manufacturing method, it is preferable that the output density is 31 W / mm 2 or more and 74 W / mm 2 or less.

[0013] before The irradiation region may have a shape that is long in the width direction of the wire. In this case, the output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the axial direction of the wire may be Gaussian type, and the output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the width direction may be top-hat type.

[0014] Furthermore, the irradiation area may be circular. In this case, the output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the axial direction of the wire, and the output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the width direction, may both be of the Gaussian type.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a coiling machine and a method for manufacturing a coil spring that can improve the manufacturing efficiency of the coil spring and manufacture a coil spring with a good shape.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a schematic perspective view showing a main part of a coiling machine according to an embodiment. [Figure 2] FIG. 2 is a schematic front view of a coiling machine according to an embodiment. ​ [Figure 3] Figure 3 is a flowchart showing the operation of a coiling machine according to one embodiment. [Figure 4] Figure 4 is a schematic perspective view showing a specific example of a spiral molding process using a coiling machine according to one embodiment. [Figure 5] Figure 5 is a schematic perspective view showing a specific example of a heating process using a coiling machine according to one embodiment. [Figure 6] Figure 6 is a perspective view showing a first example of a method in which a portion of the wire is heated and softened during the heating process. [Figure 7] Figure 7 is a cross-sectional view of the wire along line VII-VII in Figure 6. [Figure 8] Figure 8 is a perspective view showing a second example of a method in which a portion of the wire is heated and softened during the heating process. [Figure 9] Figure 9 is a cross-sectional view of the wire along the IX-IX line in Figure 8. [Figure 10] Figure 10 is a schematic perspective view showing a specific example of a cutting process using a coiling machine according to one embodiment. [Figure 11] Figure 11 is a schematic cross-sectional view of a wire irradiated with laser light. [Figure 12] Figure 12 is a cross-sectional view showing an example of a preferred positional relationship between the cutter, mandrel, and laser beam irradiation area. [Figure 13] Figure 13 is a cross-sectional view showing the state after the cutter has been lowered and the wire has been cut from the state shown in Figure 12. [Figure 14] Figure 14 is a schematic side view of a coil spring cut from a wire using the method shown in Figures 12 and 13. [Figure 15] Figure 15 is a schematic plan view of the surface of a wire irradiated with laser light having a rectangular beam profile, as seen in the direction of irradiation. [Figure 16] Figure 16 is a diagram illustrating the definition of the irradiation area shown in Figure 15. [Figure 17]Figure 17 is a schematic plan view of the surface of a wire being irradiated with laser light having a circular beam profile, as seen in the direction of irradiation. [Figure 18] Figure 18 is a diagram illustrating the definition of the irradiation area shown in Figure 17. [Figure 19] Figure 19 is a table showing irradiation conditions and examples that can be applied to laser light. [Modes for carrying out the invention]

[0017] The following describes embodiments of a coiling machine and a method for manufacturing coil springs with reference to the drawings.

[0018] Figure 1 is a schematic perspective view showing the main parts of the coiling machine 100 according to this embodiment. Figure 2 is a schematic front view of the coiling machine 100 shown in Figure 1. As shown in Figures 1 and 2, the conveying direction X, the vertical direction Y, the forming direction Z, and the circumferential direction Dθ are defined. The conveying direction X, the vertical direction Y, and the forming direction Z are orthogonal to each other. The conveying direction X is the direction in which the straight wire 1 is conveyed before being formed into a spiral. The forming direction Z is the direction in which the coil spring, formed by the spirally bent wire 1, extends (the direction in which the coil spring grows). The circumferential direction Dθ is the direction in which the wire 1 constituting the coil spring is wound.

[0019] The coiling machine 100 comprises a transport unit 10, a spiral forming unit 20, a heating unit (laser heater 30), a cutting unit 40, and a control unit 50.

[0020] In the examples shown in Figures 1 and 2, the transport unit 10 comprises a pair of drive rollers 11, a pair of driven rollers 12, and a wire guide 13. The transport unit 10 may have more drive rollers 11 and driven rollers 12.

[0021] Each drive roller 11 and each driven roller 12 are opposite each other via a wire 1. When each drive roller 11 rotates, each driven roller 12 rotates via the wire 1. As this rotation occurs, the wire 1, which is held between each drive roller 11 and each driven roller 12, is conveyed in the conveying direction X. The wire 1 is inserted into the wire guide 13. The wire guide 13 guides the wire 1 to move in a straight line in the conveying direction X, leading the wire 1 to the helical forming unit 20.

[0022] The spiral forming unit 20 forms the wire 1, which is conveyed by the conveying unit 10, into a spiral shape. In the examples shown in Figures 1 and 2, the spiral forming unit 20 includes a first forming roller 21, a second forming roller 22, and a pitch tool 23.

[0023] The first forming roller 21, the second forming roller 22, and the pitch tool 23 are arranged sequentially along the circumferential direction Dθ. The positions of the first forming roller 21, the second forming roller 22, and the pitch tool 23 in the forming direction Z are different from each other.

[0024] The first forming roller 21 and the second forming roller 22 sequentially bend the wire 1, which is being conveyed in the conveying direction X, in the vertical direction Y. The wire 1, bent in this manner, traces an arc along the circumferential direction Dθ. The bent wire 1 is guided by the pitch tool 23 at a position offset in the forming direction Z from the second forming roller 22.

[0025] As shown in Figure 2, the laser heating machine 30 irradiates a portion of the spirally shaped wire 1 with laser light L. This irradiation with laser light L creates a heated area 1V on the wire 1 that is hotter than other parts.

[0026] In the examples shown in Figures 1 and 2, the laser heater 30 comprises a laser oscillator 31, an optical fiber 32, and a laser head 33. The laser head 33 includes, for example, a beam spot adjuster.

[0027] For example, a semiconductor laser can be used as the laser oscillator 31 to generate laser light L. The optical fiber 32 transmits the laser light L generated by the laser oscillator 31 to the laser head 33. The laser head 33 adjusts the beam shape of the laser light L to a rectangular or circular shape using the beam spot adjuster described above. As the beam spot adjuster, for example, an optical element such as a beam homogenizer can be used.

[0028] The laser heater 30 may further include a measuring instrument 34 for measuring the temperature of the heated area 1V. The measuring instrument 34 has, for example, a sensor for detecting the temperature of the heated area 1V of the wire 1. The measuring instrument 34 may be located to the side of the cutting unit 40 to avoid interference with the cutting unit 40. The measuring instrument 34 may also be configured to move away from the cutter 41 in conjunction with the operation of the cutter 41 to avoid interference with the cutter 41, which will be described later. The measurement results from the measuring instrument 34 can be used, for example, to control the timing of the cutting of the wire 1 by the cutting unit 40.

[0029] Note that the measuring instrument 34 is not an essential component. In other words, various conditions for cutting the wire 1 can be set in advance without using the measuring instrument 34, and the cutting unit 40 may cut the heated portion 1V based on those conditions.

[0030] The laser heating machine 30 may further include a moving stage that moves the laser head 33 closer to and further away from the heating portion 1V of the wire 1. The moving stage can be configured, for example, as a linear stage or a robotic hand. If the working distance of the laser head 33 is set to be sufficiently long or interference with the cutting unit 40 can be avoided, it is not necessary to use a moving stage.

[0031] The cutting unit 40 cuts the heated portion 1V of the wire 1, which is hotter than before the laser beam was applied after the irradiation of the laser beam L has stopped. In the examples in Figures 1 and 2, the cutting unit 40 includes a cutter 41 and a mandrel 42.

[0032] The cutter 41 is positioned between the second forming roller 22 and the pitch tool 23 in the circumferential direction Dθ. The cutter 41 has, for example, a sharp cutting blade at its tip whose cutting edge is aligned with the forming direction Z. The cutter 41 is configured to be movable along the vertical direction Y by a drive mechanism (not shown).

[0033] The mandrel 42 is positioned inside the first forming roller 21, the second forming roller 22, and the pitch tool 23. The mandrel 42 has a semicircular shape along the XY plane, as shown in Figure 2, for example, and extends elongated in the forming direction Z. The mandrel 42 supports the inner circumferential surface of the spirally formed wire 1, mainly at its ends in the vertical direction Y of the arcuate surface.

[0034] The control unit 50 controls the transport unit 10, the helical forming unit 20, the laser heating machine 30, and the cutting unit 40. Such a control unit 50 includes a controller 51.

[0035] The controller 51 includes ROM (Read Only Memory), CPU (Central Processing Unit), and RAM (Random Access Memory). The ROM stores computer programs for controlling the transport unit 10, the spiral forming unit 20, the laser heating machine 30, and the cutting unit 40. The CPU executes the computer programs stored in the ROM. The RAM temporarily stores various data generated during the execution of the computer programs by the CPU.

[0036] Next, a method for manufacturing a coil spring 2 using the coiling machine 100 according to this embodiment will be described with reference to Figures 3 to 13.

[0037] Figure 3 is a flowchart showing the operation of the coiling machine 100. The operation shown in this flowchart is mainly achieved by the controller 51 executing a computer program. The manufacturing process of the coil spring 2 by the coiling machine 100 includes a helical forming process S01, a heating process S02, and a cutting process S03.

[0038] In the spiral forming process S01, the wire 1 is formed into a spiral shape. In the heating process S02, which follows the completion of the spiral forming process S01, a laser beam L is irradiated onto a portion of the wire 1, thereby forming a heated portion 1V on the wire 1. The heated portion 1V includes a portion that is softer than the rest of the wire 1 (base material). In the cutting process S03, which follows the completion of the heating process S02, the heated portion 1V of the wire 1 is cut.

[0039] Figure 4 is a schematic perspective view of a coiling machine 100 showing a specific example of the spiral forming process S01. In the spiral forming process S01, the conveying unit 10 guides the wire 1 in a straight line in the conveying direction X using the drive roller 11 and the driven roller 12 to the wire guide 13. The wire 1 led out from the wire guide 13 is bent in the vertical direction Y by the first forming roller 21 and the second forming roller 22 and formed into an arc shape. The arc-shaped wire 1 is guided by the pitch tool 23 to be formed into a spiral shape with a predetermined pitch. Through this operation, the spiral wire 1 gradually extends in the forming direction Z.

[0040] Figure 5 is a schematic perspective view of the coiling machine 100 showing a specific example of the heating process S02. In the heating process S02, the laser heater 30 directly irradiates the portion of the spirally formed wire 1 located near the end in the vertical direction Y of the mandrel 42 (below the cutter 41) with laser light L. The energy of this laser light L heats the base material of the wire 1 and forms a softened heated portion 1V.

[0041] During the heating process S02, the transport of the wire 1 by the transport unit 10 is stopped. The laser heater 30 is fixedly positioned, for example, at a predetermined location, and irradiates a portion of the stopped wire 1 with laser light L from this position. As another example, if the laser heater 30 has the moving stage described above, the laser heater 30 may bring the laser head 33 closer to the wire 1 before irradiating the laser light L. Alternatively, the laser heater 30 may irradiate the portion of the wire 1 being transported in the circumferential direction Dθ without stopping the transport of the wire 1 by the transport unit 10 during the heating process S02. In this case, the movement of the laser heater 30 may be controlled so that the irradiation position of the laser light L moves in accordance with the movement of the cutting position due to coiling.

[0042] Figure 6 is a perspective view of wire 1 showing a first example of a method for heating and softening a portion of the wire 1. In this example, the laser heater 30 irradiates the surface of wire 1 with laser light L1 in the irradiation direction DL. The laser light L1 has, for example, a rectangular beam profile that is elongated in the width direction of wire 1. A heated area 1V is formed in and around the irradiation area 1a of wire 1 irradiated with this laser light L1.

[0043] Figure 7 is a cross-sectional view of wire 1 along the line VII-VII in Figure 6. The heated area 1V extends not only around the irradiation area 1a on the surface of wire 1, but also into the interior of wire 1. In this example, the width of the laser beam L1 is smaller than the diameter R of wire 1. Therefore, most of the laser beam L1 is irradiated onto wire 1.

[0044] Figure 8 is a perspective view of wire 1 showing a second example of a method for heating and softening a portion of wire 1. In this example, the laser heater 30 irradiates the surface of wire 1 with laser light L2 in the irradiation direction DL. The laser light L2 has, for example, a circular beam profile. Similar to the first example, a heated area 1V is formed in and around the irradiation area 1a of wire 1 irradiated with this laser light L2.

[0045] Figure 9 is a cross-sectional view of wire 1 along the line IX-IX in Figure 8. The heated area 1V extends not only around the irradiation area 1a on the surface of wire 1, but also into the interior of wire 1. For example, the diameter of the laser beam L2 is smaller than the diameter R of wire 1. Therefore, most of the laser beam L2 is irradiated onto wire 1.

[0046] The heated area 1V may extend further into the wire 1 than in the examples shown in Figures 7 and 9. The shape of the laser beam L emitted by the laser heater 30 is not limited to the first and second examples.

[0047] In both the first and second examples, the heated area 1V may include a molten pool formed by the melting of the base material of the wire 1 by the energy of the laser beam L. The molten pool may extend not only to the irradiated area 1a but also to its surroundings.

[0048] Figure 10 is a schematic perspective view of the coiling machine 100 showing a specific example of the cutting process S03. In this embodiment, the cutting process S03 is performed after the irradiation of the laser beam L is stopped. In another example, the cutting process S03 may be performed while the laser beam L is being irradiated. In the cutting process S03, the heated portion 1V of the wire 1, which is hotter than before the laser beam L was irradiated, is cut by the cutting unit 40. This produces a coil spring 2.

[0049] Specifically, in the cutting process S03, the cutter 41 descends toward the vicinity of the portion of the wire 1 supported by the mandrel 42. At this time, the wire 1 is cut by the impact applied by the cutter 41.

[0050] If the heating area 1V includes a molten pool, the molten pool may solidify between the time the laser beam L stops irradiating and the time the cutter 41 starts operating. Alternatively, after the cutter 41 has started operating, the heat from the heating area 1V may be removed by the cutter 41 when it comes into contact with the surface of the wire 1, causing the molten pool to solidify. In this way, solidification of the molten pool before or during the operation of the cutter 41 can prevent the molten metal from adhering to the cutter 41.

[0051] In the cutting process S03, the cutter 41 can also be operated based on the temperature measurement result of the measuring instrument 34 for the heated area 1V. That is, after irradiation with the laser beam L, the cutter 41 may be operated when the temperature of the heated area 1V drops to a predetermined target temperature. The above target temperature may be, for example, the temperature at which the molten base material solidifies. Of course, in the cutting process S03, the heated area 1V may be cut without using the measuring instrument 34 by pre-determining a delay time from the stop of irradiation with the laser beam L to the start of operation of the cutter 41.

[0052] The cut coil spring 2 has a first end 61 including a first end face 61a and a second end 62 including a second end face 62a. After one coil spring 2 is manufactured, the helical forming process S01, heating process S02, and cutting process S03 described above are performed again to manufacture the next coil spring 2. Therefore, both the first end 61 and the second end 62 are cut through the above-described processes.

[0053] The shear force required to cut wire 1 decreases as the wire 1 is heated and its temperature rises. Furthermore, the shear force can be reduced even if wire 1 has not reached its melting point. Moreover, this tendency does not depend on the diameter of wire 1. As an example, when cutting wire 1 with cutter 41, it is preferable that the temperature of at least a portion of the heated area 1V is 500°C or higher.

[0054] Figure 11 is a schematic cross-sectional view of wire 1 irradiated with laser light L. Here, we assume that laser light L2, having the shape shown in Figure 8, is irradiated onto the surface of wire 1, forming a molten pool. In the figure, O indicates the center of the irradiation region 1a (see Figures 6 and 8) of laser light L on the outer surface of wire 1. For example, this irradiation center O corresponds to the position where the highest intensity peak portion of the laser light L beam profile is irradiated. Alternatively, the irradiation center O can be considered as the center of the molten pool.

[0055] As described above, when the laser beam L is irradiated onto the wire 1, a heated area 1V is formed. During or immediately after irradiation with the laser beam L, a molten pool is formed around the irradiation center O. Subsequent cooling causes the molten pool to solidify, forming a hardened area 1C. Around the molten pool, a heat-affected zone 1H (HAZ) is formed, which is not melted but has altered properties from the base material of the wire 1 due to the heat generated during irradiation with the laser beam L. Thus, the heated area 1V includes the hardened area 1C and the heat-affected zone 1H.

[0056] Figure 11 shows the results of measuring the Vickers hardness [HV] for the quenched hardened portion 1C, the heat-affected zone 1H, and the base material of wire 1. The quenched hardened portion 1C is generally harder than the base material. On the other hand, the heat-affected zone 1H is generally harder than the base material. The hardness of the heat-affected zone 1H gradually increases from the vicinity of the quenched hardened portion 1C towards the base material.

[0057] Thus, the hardness distribution is not uniform even in the heated area 1V. Therefore, it is necessary to appropriately determine the relationship between the positions of the cutter 41 and the mandrel 42 and the irradiation area of ​​the laser beam L.

[0058] Figure 12 is a cross-sectional view showing an example of a preferred positional relationship between the cutter 41, the mandrel 42, and the irradiation area of ​​the laser beam L. In the helical forming process S01 described above, the helically formed wire 1 is fed between the cutter 41 and the mandrel 42. In the feeding direction of the wire 1 (circumferential direction Dθ), a clearance G is provided between the end 41a of the cutter 41 and the end 42a of the mandrel 42. Hereinafter, the center of the clearance G in the circumferential direction Dθ will be referred to as the clearance center C.

[0059] In the example shown in Figure 12, the clearance center C and the irradiation center O are offset in the circumferential direction Dθ. Specifically, the irradiation center O is located on the cutter 41 side (downstream in the circumferential direction Dθ) of the clearance center C.

[0060] In the example shown in Figure 12, the heated area 1V includes a molten pool 1P that will become the hardened portion 1C described above after solidification. For example, the molten pool 1P overlaps with the clearance center C. Also, the molten pool 1P overlaps with the end portion 41a of the cutter 41 in the vertical direction Y.

[0061] On the other hand, the molten pool 1P does not overlap with the end portion 42a of the mandrel 42 in the vertical direction Y. In the example in Figure 12, the end portion 42a of the mandrel 42 and the portion of the heat-affected zone 1H located upstream of the molten pool 1P in the circumferential direction Dθ overlap in the vertical direction Y.

[0062] Figure 13 is a cross-sectional view showing the state in which the wire 1 is cut by lowering the cutter 41 parallel to the vertical direction Y from the state shown in Figure 12. As described above, when the wire 1 is cut by the cutter 41, the molten pool 1P is either already solidified or solidifies due to heat being removed by contact with the cutter 41. Therefore, a hardened portion 1C is formed during cutting. Note that some of the molten pool 1P may remain inside the heated portion 1V during cutting.

[0063] When the tip of the cutter 41 strikes the outer surface of the wire 1 protruding from the end 42a of the mandrel 42, a shear force is applied to the heated area 1V and its surroundings, causing the wire 1 to break. The cutter 41 descends, for example, up to near the axis of the wire 1. An indentation B (recess) is formed in the cut wire 1, i.e., the coil spring 2, by the cutter 41. In the example in Figure 13, the hardened portion 1C and the heat-affected portion 1H overlap with the indentation B, but they may be offset from each other.

[0064] As described above, the heat-affected zone 1H is softer than the hardened zone 1C and the base material of the wire 1. Therefore, when the cutter 41 impacts the wire 1, the heat-affected zone 1H is prone to fracture at the heated area 1V. In particular, as shown in Figure 12, if the irradiation center O is shifted towards the cutter 41 side of the clearance center C, a load can be effectively applied to the portion of the heat-affected zone 1H located upstream of the molten pool 1P in the circumferential direction Dθ, causing the wire 1 to fracture along that portion.

[0065] Figure 14 is a schematic side view of a coil spring 2 cut from wire 1 in the manner shown in Figures 12 and 13. The coil spring 2 has a first end 61 including a first end face 61a and a second end 62 including a second end face 62a.

[0066] The first end face 61a corresponds to the fracture surface of the coil spring 2 separated from the wire 1 in Figure 13. The first end face 61 has a first irradiation mark M1 of the laser beam L and an indentation B of the cutter 41. The first irradiation mark M1 includes a hardened portion 1C and a heat-affected zone 1H (first heat-affected zone).

[0067] The second end face 62a corresponds to the fracture surface of the wire 1 that remained above the mandrel 42 when a coil spring 2 manufactured before this coil spring 2 was cut. The second end face 62 has a second irradiation mark M2 of the laser beam L. The second irradiation mark M2 includes a heat-affected zone 1H (second heat-affected zone). If the wire 1 is cut as shown in Figure 13, the second irradiation mark M2 does not include a hardened portion 1C. However, the second irradiation mark M2 may include a smaller amount of hardened portion 1C than, for example, the first irradiation mark M1.

[0068] The heat-affected zone 1H contained in the first irradiation mark M1 extends to at least a portion of the first end face 61a. Similarly, the heat-affected zone 1H contained in the second irradiation mark M2 extends to at least a portion of the second end face 62a. On the other hand, the quenched hardened portion 1C contained in the first irradiation mark M1 does not extend to the first end face 61a. However, a portion of the quenched hardened portion 1C may extend to the first end face 61a. In this case, it is preferable that the area of ​​the quenched hardened portion 1C on the first end face 61a is smaller than the area of ​​the heat-affected zone 1H.

[0069] Next, we will explain the irradiation conditions for laser light L. Figure 15 is a schematic plan view of the surface of wire 1, which is irradiated with laser light L1 having a rectangular beam profile as shown in Figure 6, as seen in the irradiation direction DL. In the following description, the direction parallel to the axis of wire 1 will be called the axial direction DA, and the direction perpendicular to the axial direction DA and the irradiation direction DL will be called the width direction DW of wire 1.

[0070] In Figure 15, the dotted area corresponds to the irradiation area 1a of the laser beam L1 on the surface of wire 1. When viewed in the irradiation direction DL, this irradiation area 1a has a rectangular shape with a width W1 in the axial direction DA and a width W2 in the width direction DW. Width W1 is smaller than width W2. That is, in the example in Figure 15, the irradiation area 1a has an elongated shape in the width direction DW.

[0071] Figure 16 is a diagram illustrating the definition of the irradiation region 1a shown in Figure 15. In Figure 16, a center line CL1 passing through the irradiation center O of the irradiation region 1a and parallel to the axial direction DA, and a center line CL2 passing through the irradiation center O and parallel to the width direction DW are shown. On the surface of wire 1, the laser beam L1 has an output distribution PW1 along the center line CL1 and an output distribution PW2 along the center line CL2.

[0072] In the example in Figure 16, the output distribution PW1 is Gaussian-shaped, and the output distribution PW2 is top-hat-shaped. The Gaussian-shaped output distribution PW1 is bell-shaped, with the output value peaking in the center. The top-hat-shaped output distribution PW2 is trapezoidal, with the peak of the output value extending over a wide area.

[0073] In this embodiment, the full width at half maximum (FWHM) of the output distribution PW1 is defined as width W1, and the FWHM of the output distribution PW2 is defined as width W2. The FWHM of the Gaussian-type output distribution PW1 corresponds to the width of the output distribution PW1 at the point where the output value is half of the peak PK. Similarly, the FWHM of the top-hat-type output distribution PW2 corresponds to the width of the output distribution PW2 at the point where the output value is half of the peak. The FWHM of the top-hat-type output distribution PW2 can also be expressed as the sum of the bottom length Wb and top length Wt of the output distribution PW2 multiplied by 1 / 2.

[0074] Figure 17 is a schematic plan view of the surface of wire 1, which is irradiated with laser light L2 having a circular beam profile as shown in Figure 8, as seen in the irradiation direction DL. In the example in Figure 17, the irradiation area 1a is a perfect circle with diameter Ra.

[0075] Figure 18 is a diagram illustrating the definition of the irradiation area 1a shown in Figure 17. For example, the laser beam L2 has a Gaussian-type power distribution PW on the surface of wire 1 along line segments passing through the irradiation center O, such as the centerlines CL1 and CL2. The diameter Ra corresponds to the full width at half maximum of the power distribution PW, i.e., the width of the power distribution PW at the position where the output value is half of the peak PK.

[0076] The irradiation area 1a of the laser light L2 may be defined as a rectangle, represented by a width W1 in the axial direction DA and a width W2 in the width direction DW, as in the examples in Figures 15 and 16.

[0077] The shape of the irradiation area 1a and the output distributions of the laser beams L1 and L2 are not limited to those illustrated in Figures 15 to 18. For example, in Figures 15 and 16, both output distributions PW1 and PW2 may be top-hat type, or both output distributions PW1 and PW2 may be Gaussian type. Also, in the examples in Figures 17 and 18, the output distribution PW may be top-hat type.

[0078] The irradiation area 1a only needs to be defined as the area irradiated with laser light L at an output of half or more of its peak power, and its shape is not limited to a rectangle or a perfect circle. As another example, the irradiation area 1a may be elliptical. In this case, the major and minor axes of the irradiation area 1a may be defined by the full width at half maximum of the power distribution.

[0079] Figure 19 is a table showing the irradiation conditions applicable to the laser beam L and Examples 1, 2, and 3. As in this embodiment, the cutting method using both heating by the laser beam L and the cutting unit 40 is suitable for cutting thick wires 1 with a diameter R of 8 mm or more. However, if the wire 1 is too thick, a good cut surface may not be obtained. Therefore, in this embodiment, as an example, we assume that the diameter R of the wire 1 is 8 mm or more and 18 mm or less, as shown in the irradiation conditions of Figure 19.

[0080] Considering heating efficiency, it is preferable to irradiate the wire 1 with the laser beam L so as not to extend beyond it. Furthermore, if the irradiation area 1a of the laser beam L is too small, it may not be possible to form a heat-affected zone 1H with a shape suitable for cutting on the wire 1. Therefore, for example, if the irradiation area 1a is rectangular as shown in Figures 15 and 16, and the diameter R of the wire 1 is 8 mm or more and 18 mm or less, it is preferable to set the width W1 of the irradiation area 1a to 2 mm or more and 6 mm or less, and the width W2 to 8 mm or more and 18 mm or less. In the case of such irradiation size, the irradiation area (width W1 × width W2) is 16 mm². 2and 108mm or more 2 This is the result.

[0081] The output of the laser beam L must be set so that a sufficient heat-affected zone 1H is formed on the wire 1, and the wire 1 is not cut by irradiation with the laser beam L alone. If the output of the laser beam L is too low, the irradiation time must be increased to form a sufficient heat-affected zone 1H for cutting, but if the irradiation time is too long, the manufacturing efficiency of the coil spring 2 will decrease. On the other hand, if the output of the laser beam L is too high, the laser heater 30 will become larger, reducing the freedom of layout for each part of the coiling machine 100. Furthermore, the wire 1 may overheat, causing the hardened zone 1C to enlarge or sputtering to occur.

[0082] For example, considering these factors, it is preferable that the output of the laser beam L be between 500W and 8000W. Furthermore, the power density, which corresponds to the output of the laser beam L per unit area, should be 10W / mm². 2 The above and 100W / mm 2 Preferably, the following conditions apply: Power density of 31 W / mm² 2 The above and 74W / mm 2 The following is even more preferable.

[0083] The power density is the value obtained by dividing the output of the laser beam L by the area of ​​the irradiation region 1a on the surface of the wire 1 when viewed in the irradiation direction DL. The irradiation region 1a referred to here is the region defined by the full width at half maximum of the output distribution of the laser beam L on the surface of the wire 1, as explained using, for example, Figure 16.

[0084] In Examples 1, 2, and 3 shown in Figure 19, the output power of the laser beam L is 3000W in all cases, but the irradiation size and irradiation area differ. The irradiation size is 4mm × 14mm in Example 1, 3.9mm × 12.1mm in Example 2, and 3.8mm × 15.4mm in Example 3. The irradiation area is 56mm in Example 1. 2 In Example 2, the result was 47.19 mm. 2 In Example 3, the value was 58.52 mm. 2 That is the case.

[0085] In this case, the power density was 53.57 W / mm² in Example 1. 2 In Example 2, the result was 63.57 W / mm². 2 In Example 3, the result was 51.26 W / mm². 2 These power densities are all 10 W / mm² as shown in the irradiation conditions in Figure 19. 2 The above and 100W / mm 2 Furthermore, 31W / mm 2 The above and 74W / mm 2 The following applies:

[0086] When manufacturing a coil spring 2 using a coiling machine 100 with a wire 1 having a diameter R of 8 mm or more and 18 mm or less, using the laser beam L under the conditions of Examples 1, 2, and 3 in the heating step S02 resulted in a small shear force required for cutting, and it was possible to manufacture a coil spring 2 with a good end shape.

[0087] In Figure 19, the irradiation size is assumed to be defined by widths W1 and W2, but if the irradiation area 1a is circular, the irradiation size may be defined by its radius. Furthermore, the irradiation size can be determined appropriately depending on the shape of the irradiation area 1a. Regardless of how the irradiation size is defined, similar effects can be obtained as long as the power density is within the range shown in Figure 19.

[0088] According to this embodiment, the portion of the spirally bent wire 1 that has become hot due to irradiation with laser light L (heated portion 1V) is cut by the cutting unit 40 (cutter 41 and mandrel 42), thus reducing the shear force required for cutting. Therefore, the wire 1 can be easily cut.

[0089] Furthermore, as explained using Figure 19, by determining the irradiation conditions of the laser light L, such as the power density, it is possible to increase the manufacturing efficiency of the coil spring 2 and obtain a high-quality coil spring 2 with good terminals.

[0090] The above embodiments do not limit the scope of the present invention to the configurations disclosed in those embodiments. The present invention can be implemented by modifying the configurations disclosed in those embodiments in various ways.

[0091] For example, when implementing the present invention, it goes without saying that the configuration and arrangement of each element of the coiling machine 100 can be changed in various ways as needed.

[0092] In each embodiment, an example was shown in which the coiling machine 100 cuts the heated portion 1V of the wire 1 using a cutter 41. The coiling machine 100 is not limited to this configuration, and the heated portion 1V of the wire 1 may also be cut by cutting with a rotary saw blade.

[0093] The coil spring 2 manufactured by the coiling machine 100 can take on various forms; for example, the coil diameter and pitch may vary in the axial direction of the coil spring. That is, the coil spring 2 manufactured by the coiling machine 100 can be of various forms, including cylindrical coil springs, barrel-shaped coil springs, drum-shaped coil springs, tapered coil springs, unequal pitch coil springs, coil springs with negative pitch sections, and so on. [Explanation of symbols]

[0094] 1…Wire, 1a…Irradiation area, 1V…Heating area, 1P…Melting pool, 1C…Hardening and hardening area, 1H…Heat-affected zone, 2…Coil spring, 10…Transport unit, 11…Drive roller, 12…Driven roller, 13…Wire guide, 20…Spiral forming unit, 21…First forming roller, 22…Second forming roller, 23…Pitch tool, 30…Laser heater, 31…Laser oscillator, 32…Optical fiber, 33…Laser head, 34… Measuring instrument, 40...cutting unit, 41...cutter, 42...mandrel, 50...control unit, 51...controller, 61...first terminal, 62...second terminal, 100...coiling machine, L, L1, L2...laser beam, S01...spiral forming process, S02...heating process, S03...cutting process, M1...first irradiation mark, M2...second irradiation mark, B...indentation, X...conveying direction, Y...vertical direction, Z...forming direction, Dθ...circumferential direction, DL...irradiation direction.

Claims

1. A laser heating machine heats a metal wire that is formed into a spiral shape by irradiating it with laser light without extending the wire, thereby forming a heated area that includes a molten pool and a heat-affected zone located around the molten pool where the properties of the wire's base material have changed. A cutting unit comprising a mandrel that supports the inner circumferential surface of the wire which is formed into a spiral shape, and a cutter that protrudes from the end of the mandrel and descends toward the outer circumferential surface of the wire, wherein the wire is cut by applying an impact to the heated portion with the cutter, Equipped with, The diameter of the aforementioned wire is 8 mm or more and 18 mm or less. The area of ​​the irradiation region defined by the full width at half maximum of the output distribution of the laser light on the surface of the wire, when viewed in the direction of irradiation of the laser light, is 16 mm² or more and 108 mm² or less. The output of the laser light is 500W or more and 8000W or less. The power density, which is the value obtained by dividing the output of the laser light by the area of ​​the irradiation region, is 10 W / mm². ２ The above and 100W / mm ２ The following is: Coiling machine.

2. The aforementioned power density is 31 W / mm². ２ The above and 74 W / mm ２ The following is: The coiling machine according to claim 1.

3. The irradiation area has an elongated shape in the width direction of the wire, The output distribution of the laser beam on the surface of the wire, passing through the center of the irradiation area and along a center line parallel to the axial direction of the wire, is of the Gaussian type. The output distribution of the laser beam on the surface of the wire, passing through the center of the irradiation area and along a center line parallel to the width direction, is top-hat shaped. The coiling machine according to claim 1 or 2.

4. The irradiation area is circular, The output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the axial direction of the wire, and the output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the width direction of the wire, are both of the Gaussian type. The coiling machine according to claim 1 or 2.

5. A metal wire formed into a spiral shape is heated by irradiating it with laser light without extending beyond the wire, thereby forming a heated area that includes a molten pool and a heat-affected zone located around the molten pool, where the properties of the wire's base material have changed. The inner circumferential surface of the spirally formed wire is supported by a mandrel, and the wire is cut by lowering a cutter toward the outer circumferential surface of the wire protruding from the end of the mandrel and applying an impact to the heated area. Includes, The diameter of the aforementioned wire is 8 mm or more and 18 mm or less. The area of ​​the irradiation region defined by the full width at half maximum of the output distribution of the laser light on the surface of the wire, when viewed in the direction of irradiation of the laser light, is 16 mm² or more and 108 mm² or less. The output of the laser light is 500W or more and 8000W or less. The power density, which is the value obtained by dividing the output of the laser light by the area of ​​the irradiation region, is 10 W / mm². ２ The above and 100W / mm ２ The following is: A method for manufacturing coil springs.

6. The aforementioned power density is 31 W / mm². ２ The above and 74 W / mm ２ The following is: The method for manufacturing a coil spring according to claim 5.

7. The irradiation area has an elongated shape in the width direction of the wire, The output distribution of the laser beam on the surface of the wire, passing through the center of the irradiation area and along a center line parallel to the axial direction of the wire, is of the Gaussian type. The output distribution of the laser beam on the surface of the wire, passing through the center of the irradiation area and along a center line parallel to the width direction, is top-hat shaped. A method for manufacturing a coil spring according to claim 5 or 6.

8. The irradiation area is circular, The output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the axial direction of the wire, and the output distribution of the laser beam on the surface of the wire along a center line passing through the center of the irradiation area and parallel to the width direction of the wire, are both of the Gaussian type. A method for manufacturing a coil spring according to claim 5 or 6.

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