High frequency heating coil and coil spring forming device

Abstract

To provide a high frequency heating coil which can improve the carburization property without reducing the feeding speed of a steel wire material and simply expanding and increasing the heating coil.SOLUTION: There is provided a high frequency heating coil which performs high frequency heating by making a steel wire material inserted from a coil inlet pass therethrough. A double coil part 48 made of a closely wound inner coil part 41 and a closely wound or coarsely wound outer coil part 43 arranged on the outer side of the inner coil part 41 is provided on the coil inlet side. A closely wound single coil part 45 having the larger outer diameter than the outer diameter of the inner coil part 41 is provided so as to be adjacent to a coil outlet side of the double coil part 48. A coarsely wound coil part 46 which is coarsely wound and has the larger outer diameter than the outer diameter of the single coil part is extended to the coil outlet adjacently to the coil outlet side of the single coil part 45.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a high-frequency heating coil and a spring forming apparatus for heating steel wire by high-frequency waves, and in particular to a technology for improving carburization properties by shortening the time required to reach the maximum temperature and thereby extending the holding time at the maximum temperature. [Background technology]

[0002] For example, in the manufacturing process of coil springs, steel wire is heated to the austenite region by a high-frequency heating coil, hot-coiled, and quenched and tempered. In such a process, the steel wire is sometimes carburized by contacting it with a hydrocarbon gas while being heated and held.

[0003] For example, in the high-frequency hot coiling technology disclosed in Patent Document 1, a carbon-enriched layer of uniform thickness is formed on the surface of a steel wire by carburizing the steel wire by supplying a hydrocarbon gas when the steel wire is heated. Here, the depth of the carbon-enriched layer is affected by the heating temperature and time. If the heating time is short, carburization does not proceed and the desired carburized layer depth cannot be obtained. On the other hand, the higher the heating temperature, the higher the carburization property, but it leads to coarsening of the crystal grain size, so the heating temperature is preferably 1000°C or higher and 1100°C or lower, or 1000°C or higher and 1050°C or lower. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6251830 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, in order to obtain a uniform carburized layer of the desired depth, it was necessary to slow down the feed speed of the steel wire. The slower the feed speed of the steel wire, the longer the contact time between the steel wire and the hydrocarbon gas, and the longer the diffusion time of C. This improves the carburization property, but on the other hand, reduces productivity.

[0006] Therefore, it is preferable to obtain the desired carburized layer depth without reducing the steel wire feed speed, but if the steel wire feed speed is increased, there is a problem that a sufficient carburized layer depth cannot be obtained or a uniform carburized layer cannot be obtained over the entire circumference of the wire. In addition, in hot coiling, the coil length is limited to 350 mm or less because expanding the heating area causes buckling and shape variation in the steel wire.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide a high-frequency heating coil and a spring forming device that can improve carburization properties without reducing the feed speed of the steel wire and without simply expanding or adding to the heating coil. [Means for solving the problem]

[0008] The present invention is a high-frequency heating coil that heats a steel wire inserted from the coil inlet by passing it through the inside. And, Entrance side of the ile To be placed in Densely wound inner coil and, The inner coil portion is disposed on the outer side of the inner coil portion. The end of the coil inlet side is connected to the end of the inner coil part on the coil inlet side by a connecting piece extending in the radial direction. Densely or loosely wound outer coil section and the inner coil portion Adjacent to the coil exit end Connected A tightly wound single coil portion having an outer diameter larger than the outer diameter of the inner coil portion. and, Adjacent to the coil outlet end of the single coil portion Connected, The single coil portion has an outer diameter larger than the outer diameter of the single coil portion. Extends to the coil outlet Coarsely wound coil part and Equipped The high-frequency heating coil is characterized by the above.

[0009] According to the present invention, a densely wound inner coil portion is provided on the coil inlet side. Place the Outside of the inner coil Close to Wound or loosely wound outer coil Place the part Because, The area where the inner coil section and the outer coil section overlapIn this coil, the steel wire can be rapidly heated to the austenite region over a short feed distance. The rapidly heated part of the steel wire then reaches the single coil section. Since the single coil section has an outer diameter larger than that of the inner coil section, the magnetic flux density at the position where the steel wire passes through is reduced, suppressing heat generation in the steel wire. As a result, the rapidly heated part of the steel wire that has entered the single coil section is in a heat-retaining state where the temperature in the austenite region is maintained.

[0010] Furthermore, the portion of the steel wire rod that is kept warm reaches the coarsely wound coil portion. Since the coarsely wound coil portion has an outer diameter larger than that of the single coil portion and is coarsely wound, the magnetic flux density at the position where the steel wire rod passes through is further reduced, and heat generation of the steel wire rod is further suppressed. As a result, the portion of the steel wire rod that has entered the coarsely wound coil portion and is kept warm is maintained at a temperature in the austenite range. Therefore, carburizing can be performed in the long portion of the high-frequency heating coil.

[0011] Note that "dense winding" refers to a case where the gap between the high-frequency heating coil wires that do not include an insulating coating is 2 mm or less, and "loose winding" refers to a case where the gap between the high-frequency heating coil wires that do not include an insulating coating is greater than 2 mm.

[0012] In the above-mentioned configuration, the single coil portion can be extended to the coil outlet side. In such a configuration, the above-mentioned effect of the single coil is maintained up to the coil outlet, so that carburizing can be performed in the long portion of the high frequency heating coil.

[0013] In the present invention, outside The coil section Single coil and , outside Side coil Department A first terminal can be fixed to an end portion on the coil outlet side of the coarsely wound coil portion, and a second terminal can be fixed to an end portion on the coil outlet side of the coarsely wound coil portion.

[0014] In this case, the second terminal extends in a direction perpendicular to the end face of the coarsely wound coil portion, and the first terminal includes a first horizontal terminal portion extending in a direction perpendicular to the end face of the outer coil portion and substantially parallel to the second terminal; No. 1 It is preferable that the terminal is composed of an axial terminal portion extending from an end of the lateral terminal portion in the axial direction of the outer coil portion, a vertical terminal portion extending from an end of the axial terminal portion toward the second terminal, and a second lateral terminal portion extending from the end of the vertical terminal portion in the same direction as and parallel to the second terminal. With this configuration, the second terminal and the second lateral terminal are arranged parallel to and close to each other, making it easy to connect these terminals to a power supply device.

[0015] Also, The overlapping area between the inner coil section and the outer coil section It is preferable that the length of the high-frequency heating coil is 1 / 3 or less of the total length of the high-frequency heating coil. In other words, the carburizing treatment can be performed on a portion having a length of 2 / 3 or more of the total length of the high-frequency heating coil, so that the carburizing property can be improved without extending the high-frequency heating coil. As a result, the total length of the high-frequency heating coil can be reduced to 350 mm or less.

[0016] Next, the present invention is a coil spring forming apparatus comprising a feed roller for continuously supplying steel wire material, a coiling section for forming the steel wire material into a coil shape, cutting means for coiling the steel wire material a predetermined number of turns and then separating it from the steel wire material continuously supplied from the rear, and heating means provided between the feed roller and the coiling section, the heating means comprising a high-frequency heating coil having the above-mentioned configuration, inside which the steel wire material passes, and hydrocarbon supplying means for creating a hydrocarbon gas atmosphere in the area where the steel wire material passes.

[0017] According to such a coil spring forming apparatus, the steel wire is rapidly heated to the austenite region in the heating means and then carburized by a hydrocarbon gas within a sufficient temperature retention period, so that the carburization property can be improved without reducing the feed speed of the steel wire and without simply expanding or adding to the heating coil. Effect of the Invention

[0018] According to the present invention, there is provided a high-frequency heating coil and a spring forming device that can improve the carburizing property without reducing the feed speed of the steel wire and without simply expanding or adding to the heating coil. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a side view showing a spring forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2A is a side view showing a high-frequency heating coil according to an embodiment of the present invention, and FIG. [Diagram 3] FIG. 2A is a side view showing a high-frequency heating coil according to a reference example of the present invention, and FIG. [Figure 4] 1 is a graph showing a relationship between a distance from a coil inlet of a steel wire and a temperature of the steel wire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 1. Spring forming equipment configuration 1, the spring forming apparatus 1 includes feed rollers 10 for continuously supplying steel wire material M, and a coiling section 20 for forming the steel wire material M into a coil shape. The coiling section 20 includes a wire guide 21 for guiding the steel wire material M supplied by the feed rollers 10 to an appropriate position, a coiling tool 22 consisting of a coiling pin (or coiling roller) 22a for processing the steel wire material M supplied via the wire guide 21 into a coil shape, and a pitch tool (not shown) for providing a pitch.

[0021] The spring forming apparatus 1 also includes a cutting means 30 having a cutting blade 30a and an inner die 30b for separating the steel wire material M that is continuously supplied from the rear after coiling a predetermined number of turns, and a high-frequency heating coil 40 for heating the steel wire material M between the exit of the feed roller 10 and the coiling tool 22.

[0022] A hydrocarbon-based gas supplying section (hydrocarbon-based gas supplying means) 50 is disposed near the middle between the high-frequency heating coil 40 and the feed roller 10, for creating a hydrocarbon-based gas atmosphere at the location where the steel wire material M passes. An enclosure member 51 made of, for example, ceramics is disposed inside the high-frequency heating coil 40, and a hydrocarbon-based gas is supplied from the hydrocarbon-based gas supplying section 50 into the enclosure member 51 so that the steel wire material M passes through.

[0023] 2. Configuration of high frequency heating coil High-frequency heating coil 40 according to an embodiment of the present invention will be described with reference to Fig. 2. Note that in Fig. 2, the left side is the coil inlet and the right side is the coil outlet. High-frequency heating coil 40 is made up of various coil sections with a uniform coil wire diameter but different pitches and outer diameters.

[0024] A densely wound inner coil part 41 is disposed on the coil inlet side, and the inner coil part 41 extends for three and a half turns toward the coil outlet. One end of a connecting piece 42 protruding radially outward is fixed to the end face on the coil inlet side of the inner coil part 41, and the other end of the connecting piece 42 is fixed to the end face of a loosely wound outer coil part 43.

[0025] The inner diameter of the outer coil portion 43 is larger than the outer diameter of the inner coil portion 41, so that a gap is formed between the inner coil portion 41 and the outer coil portion 43. The outer coil portion 43 extends two turns toward the coil outlet. The outer coil portion 43 and the inner coil portion 41 form a double coil. Part 4 8 is configured.

[0026] A first terminal 44 is fixed to the end face on the coil outlet side of the outer coil portion 43. The first terminal 44 is composed of a first horizontal terminal portion 44a extending toward the rear side perpendicular to the paper surface, an axial terminal portion 44b extending in the axial direction from an end portion of the first horizontal terminal portion 44a, a vertical terminal portion 44c extending downward from an end portion of the axial terminal portion 44b, and a second horizontal terminal portion 44d extending from an end portion of the vertical terminal portion 44c toward the rear side perpendicular to the paper surface.

[0027] A densely wound single coil portion 45 extends from the end of the inner coil portion 41 on the coil outlet side toward the coil outlet side with three turns. The outer diameter of the single coil portion 45 is larger than the outer diameter of the inner coil portion 41 and smaller than the outer diameter of the outer coil portion 43.

[0028] The coarsely wound coil portion 46 extends one turn from the end of the single coil portion 45 on the coil exit side toward the coil exit side. The outer diameter of the coarsely wound coil portion 46 is approximately the same as the outer diameter of the outer coil portion 43, but the pitch is approximately 2.5 times the pitch of the outer coil portion 43. A second terminal 47 is fixed to the end of the coarsely wound coil portion 46, extending toward the rear side perpendicular to the paper surface. The first and second terminals 44, 47 are connected to a power supply device.

[0029] 3. Operation of spring forming equipment The steel wire M is fed into the enclosing member 51 by the feed roller 10 and passes through the enclosing member 51. At that time, the steel wire M is heated by the high-frequency heating coil 40. In the high-frequency heating coil 40, when a high-frequency alternating current is supplied to the first and second terminals 44, 47, an alternating magnetic flux is generated that passes through the inside thereof, and Joule heat is generated by eddy currents in the conductive object to be heated.

[0030] In the high-frequency heating coil 40 having the above-mentioned configuration, a double coil portion 48 consisting of an inner coil portion 41 and an outer coil portion 43 is provided on the coil inlet side, so that an alternating magnetic flux with high density passes through the inside. As a result, the steel wire M passing through the high-frequency heating coil 40 is rapidly heated, and reaches a temperature in the austenite region within 2.5 seconds, for example.

[0031] The portion of the steel wire M that has been heated to the austenite region temperature then enters the single coil portion 45. Since the single coil portion 45 has an outer diameter larger than that of the inner coil portion 41, the magnetic flux density at the position where the steel wire M passes through is reduced, and heat generation of the steel wire M is suppressed. As a result, the steel wire M that has entered the single coil portion 45 is in a heat-retaining state in which the temperature of the austenite region is maintained.

[0032] Next, the part of the steel wire M that has maintained the temperature in the austenite region enters the coarsely wound coil portion 46. Since the coarsely wound coil portion 46 has a larger outer diameter and pitch than the single coil portion 45, the magnetic flux density at the position where the steel wire M passes through is further reduced, heat generation of the steel wire M is suppressed, and the temperature in the austenite region is maintained.

[0033] The part of the steel wire M that has been kept at the austenite temperature is carburized by contacting with the hydrocarbon gas supplied from the hydrocarbon gas supply unit 50 into the enclosure member 51. Then, the part is supplied to the coiling unit 20 via the wire guide 21. In the coiling unit 20, the steel wire M that has passed through the wire guide 21 is bent with a predetermined curvature by contacting with the coiling pin 22a, and is further bent with a predetermined curvature by contacting with the downstream coiling pin 22a. Then, the steel wire M is contacted with a pitch tool to give a pitch so as to form a desired coil shape. When the desired number of turns is reached, the cutting blade 30a of the cutting means 30 is sheared between the straight portion of the inner mold 30b to separate the steel wire M supplied from the rear and the spring-shaped steel wire M.

[0034] In the high-frequency heating coil 40 having the above configuration, the temperature rise region by the double coil portion 48 is short, and the heat retention region consisting of the single coil portion 45 and the loosely wound coil portion 46 is long, so that the steel wire rod M can be in contact with the hydrocarbon gas for a long time in the heat retention region and can be sufficiently carburized. Therefore, the carburization property can be improved without reducing the feed speed of the steel wire rod M and without simply expanding or adding the high-frequency heating coil 40.

[0035] In particular, in the above embodiment, a second terminal 47 is fixed to the end of the coarsely wound coil portion 46, and a second lateral terminal portion 44d is arranged adjacent to this second terminal 47 and extending in the same direction, so that connection to a power supply device can be easily made.

[0036] 4. Example of changes The present invention is not limited to the above-described embodiment, and various modifications are possible as follows.

[0037] (1) The single coil portion 45 can be extended to the coil outlet without providing the coarsely wound coil portion 46.

[0038] (2) Outer coil portion 43 may be densely wound. This can further shorten the temperature rise region caused by double coil portion 48 and extend the heat retention region.

[0039] (3) The double coil portion 48 may be a multiple coil portion having three overlapping coils. This also makes it possible to further shorten the temperature rise region by the multiple coil portion and extend the heat retention region. (4) The heating coil may be formed as a single continuous coil without providing any connecting pieces or terminal parts.

[0040] 5.Reference example Next, a high-frequency heating coil that was prototyped in the process of completing high-frequency heating coil 40 of the present invention will be described.

[0041] 3A and 3B are a side view and a cross-sectional view showing a high-frequency heating coil 60 of a reference example. A densely wound single coil portion 61 is disposed on the coil inlet side of the high-frequency heating coil 60. The single coil portion 61 extends for seven and a half turns toward the coil outlet. A connecting piece 62 protruding radially outward is fixed to the coil outlet side end of the single coil portion 61, and an end of a coarsely wound coil portion 63 is fixed to an end of the connecting piece 62.

[0042] The coarsely wound coil portion 63 has a pitch and an outer diameter equivalent to those of the coarsely wound coil portion 46 of the above embodiment, and extends for three turns to the coil exit. A terminal 64 is fixed to an end of the coarsely wound coil portion 63. A terminal 65 is also fixed to the end of the single coil portion 61 on the coil inlet side. By supplying a high-frequency alternating current to the terminals 64, 65, an alternating magnetic flux passes inside.

[0043] It would appear that the high-frequency heating coil 60 having the above-mentioned configuration would also be able to rapidly heat the steel wire M in the single coil portion 61 and keep it warm in the loosely wound coil portion 63. However, according to the inventor's investigation, it has become clear that the carburization is insufficient in the high-frequency heating coil 60 described above, as shown in the following performance test.

[0044] 6. Performance Test (1) Temperature distribution of steel wire Assuming that a conventional high-frequency heating coil (conventional example) consisting only of a tightly wound coil portion, high-frequency heating coil 60 (reference example) shown in Fig. 3, and high-frequency heating coil 40 (invention example) shown in Fig. 2 are attached to spring forming apparatus 1 shown in Fig. 1 and heated while supplying steel wire material, the temperature distribution of the steel wire material was analyzed using electromagnetic field analysis software (JMAG). The results are shown in Fig. 4.

[0045] Figure 4 shows the temperature distribution of the steel wire from the coil inlet. In a conventional high-frequency heating coil consisting only of a tightly wound coil section, the temperature reaches 1000°C at a position 100 mm from the coil inlet, whereas in the reference example, it reaches 1000°C at a position 40 mm, and in the inventive example, it reaches 1000°C at a position 20 mm.

[0046] (2) Carburization test The above three types of high-frequency heating coils were attached to a spring forming apparatus 1 shown in FIG. 1, and coil springs were formed under the following conditions. Coil wire diameter: 4.1mm, heating temperature: 1050℃, feed speed: faster than conventional, spring index: 6

[0047] When the state of carburization was investigated in the cross section of the formed coil spring, carburization was confirmed in 100% of the circumference of the cross section in the example of the invention. The carburization depth was 30-40 μm and the carbon concentration was 0.7-1.0 mass %. Moreover, the area with a carbon concentration of 0.8 mass % or more covered 97% of the circumference of the cross section.

[0048] In contrast, carburization was confirmed in 70-80% of the circumference of the cross section in the conventional example, and in the reference example, carburization was confirmed in 78% of the circumference of the cross section. Therefore, in the conventional example and the reference example, carburization was not sufficient at a feed speed faster than the conventional one, and it was necessary to reduce the feed speed to the conventional level. Thus, it was confirmed that in the present invention, carburization is reliably achieved even when the feed speed of the steel wire is faster than the conventional one. [Industrial Applicability]

[0049] The present invention enables reliable carburizing without reducing production speed and without simply expanding or adding heating coils, and is therefore applicable to the coil spring industry used in all technical fields, such as transportation equipment such as automobiles, motorcycles, and trains, construction machinery, machine tools, and agricultural machinery. [Explanation of symbols]

[0050] 10...feed roller, 20...coiling section, 21...wire guide, 22...coiling tool, 22a...coiling pin, 30...cutting means, 30a...cutting blade, 30b...inner mold, 40, 60...high frequency heating coil, 41...inner coil section, 42...connecting piece, 43...outer coil section, 44...first terminal, 44a...first horizontal terminal section, 44b...axial terminal section, 44c...vertical terminal section, 44d...second horizontal terminal section, 45...single coil section, 46...coarsely wound coil section, 47...second terminal, 48...double coil Department, 50...hydrocarbon gas supply section (hydrocarbon gas supply means), 51...enclosure member, W...steel wire material.

Claims

1. A high-frequency heating coil that heats a steel wire inserted from a coil inlet by passing the steel wire through the coil, A densely wound inner coil portion disposed on the coil inlet side; a densely or coarsely wound outer coil section disposed outside the inner coil section, the coil inlet side end of which is connected to the coil inlet side end of the inner coil section by a radially extending connecting piece; a densely wound single coil portion connected adjacent to a coil outlet side end of the inner coil portion and having an outer diameter larger than an outer diameter of the inner coil portion; a coarsely wound coil section connected adjacent to the coil outlet side end of the single coil section, having an outer diameter larger than the outer diameter of the single coil section, and extending to the coil outlet.

2. The outer coil portion is a single coil, a first terminal is fixed to an end of the outer coil portion on the coil outlet side, the first terminal being in no contact with the single coil portion and the coarsely wound coil portion and having a portion extending to the coil outlet; The high-frequency heating coil according to claim 1, characterized in that a second terminal extending in a direction perpendicular to an end face of the coarsely wound coil portion is fixed to an end portion on a coil outlet side of the coarsely wound coil portion.

3. The first terminal, a first horizontal terminal portion extending from an end portion of the outer coil portion on a coil outlet side in a direction substantially parallel to the second terminal and perpendicular to an end face of the outer coil portion; an axial terminal portion extending in the axial direction of the outer coil portion from an end portion of the first lateral terminal portion opposite to an end portion of the outer coil portion on the coil outlet side to the coil outlet; a longitudinal terminal portion extending from a coil outlet side end of the axial terminal portion toward the second terminal; 3. The high frequency heating coil according to claim 2, further comprising a second horizontal terminal portion extending in the same direction as and parallel to the second terminal from an end of the vertical terminal portion on a second terminal side.

4. A high-frequency heating coil that heats a steel wire inserted from a coil inlet by passing the steel wire through the coil, A densely wound inner coil portion disposed on the coil inlet side; a densely or coarsely wound outer coil section disposed outside the inner coil section, the coil inlet side end of which is connected to the coil inlet side end of the inner coil section by a radially extending connecting piece; a densely wound single coil portion connected adjacent to the coil outlet side end of the inner coil portion, having an outer diameter larger than the outer diameter of the inner coil portion, and extending to the coil outlet.

5. A high-frequency heating coil as described in any one of claims 1 to 4, characterized in that the overlapping portion between the inner coil portion and the outer coil portion has a length of less than 1 / 3 of the total length of the high-frequency heating coil.

6. 6. The high frequency heating coil according to claim 1, wherein the overall length is 350 mm or less.

7. The wire feeder includes a feed roller for continuously feeding a steel wire material, a coiling section for forming the steel wire material into a coil shape, a cutting means for cutting the steel wire material from the steel wire material continuously fed from the rear after the steel wire material has been coiled by a predetermined number of turns, and a heating means provided between the feed roller and the coiling section, The heating means comprises the high-frequency heating coil according to any one of claims 1 to 6, the steel wire passing through the inside thereof, and a hydrocarbon supplying means for creating a hydrocarbon gas atmosphere at the location where the steel wire passes.

Images