JP2020020027A - Heating method for coil spring, heating device for end coil part, and coil spring - Google Patents

Abstract

To provide a heating method of a coil spring, in which uneven heating can be circumvented in the coil spring having an end coil part, and to provide a heating device for the end coil part, and the coil spring.SOLUTION: A heating method of a coil spring heats a coil spring 1 composed of a wire material W extending in a spiral shape and having an end coil part 2 in which a cross-sectional area changes along the extending direction by defining a cross-sectional area of the wire material W in the orthogonal direction with respect to the extending direction of the wire material W as a cross-sectional area, and a general part 3 which is continuous to the end coil part 2 and in which a cross-sectional area is constant along the extending direction. The heating method of the coil spring includes: an end coil part heating step of heating the end coil part 2 by adjusting a thermal load in consideration of the change in cross-sectional area; and a general part heating step of heating the general part 3 before or after the end coil part heating step.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method of heating a coil spring used for heating such as heat treatment of a coil spring, hot setting, warm shot peening, and baking of paint, such as quenching, tempering, and annealing, an end turn heating device, and a coil spring. .

  Patent Document 1 discloses a method of heating a coil spring. According to the heating method of the coil spring described in the document, both ends of the coil spring are gripped by a pair of clamp mechanisms, and an electric current is supplied between the both ends, whereby the intermediate portion of the coil spring can be heated. In addition, an electrode section is disposed on each of the pair of clamp mechanisms. A portion having higher electric resistance than other portions is arranged in the electrode portion. For this reason, the electrode portion is likely to generate heat when energized. Therefore, both ends of the coil spring can be heated by the heat generated by the electrode portions during energization. As described above, according to the coil spring heating method described in the document, the intermediate portion and both end portions of the coil spring, in other words, the entire coil spring can be heated at once.

JP 2011-195919 A

  However, some coil springs have an end turn, such as a compression spring that is compressed during use. The wire diameter of the end winding portion gradually changes along the extending direction of the wire. In other words, when the cross-sectional area of the wire in the direction perpendicular to the direction in which the wire is extended is defined as the cross-sectional area, the cross-sectional area of the end winding portion changes for each part along the direction in which the wire extends. For this reason, the portion of the end winding portion having a small cross-sectional area is easily heated. Conversely, a portion of the end winding portion having a large cross-sectional area is not easily heated.

  For this reason, when the coil spring having the end turns is heated by the coil spring heating method described in Patent Document 1, the end turns are excessive with respect to portions other than the end turns (portions having a constant cross-sectional area). May be heated. Further, in the end winding portion, a portion having a small cross-sectional area may be excessively heated with respect to a portion having a large cross-sectional area. As described above, when the entire coil spring having the end winding portion is uniformly heated, uneven heating is likely to occur due to a difference in cross-sectional area.

  The coil spring heating method, the end turn heating device, and the coil spring of the present invention have been completed in view of the above problems. An object of the present invention is to provide a coil spring heating method, an end coil heating device, and a coil spring in which uneven heating is unlikely to occur even with a coil spring having an end coil.

  (1) In order to solve the above-mentioned problems, a method for heating a coil spring according to the present invention comprises a helically extending wire, and a cross-sectional area of a cross section of the wire in a direction perpendicular to an extending direction of the wire. As a coil spring, comprising: an end winding part whose cross-sectional area changes along the extending direction; and a general part connected to the end winding part and having a constant cross-sectional area along the extending direction. A heating method of a coil spring to be heated, wherein a heat load is adjusted in consideration of a change in the cross-sectional area, and an end turn heating step of heating the end turn, and before or after the end turn heating step A general part heating step of heating the general part.

  The heating method of the coil spring of the present invention includes an end winding heating step and a general heating step. For this reason, the end winding part and the general part can be separately heated. Therefore, the heating condition for the end winding portion and the heating condition for the general portion can be set separately. Therefore, each of the end winding portion and the general portion can be heated at a temperature within a predetermined range. For this reason, uneven heating is unlikely to occur in the coil spring.

  Further, in the end turn heating step, the heat load is adjusted in consideration of a change in the cross-sectional area in the end turn. For this reason, each part of the end winding portion can be heated at a temperature within a predetermined range. Therefore, uneven heating is unlikely to occur in the end winding portion.

  (2) Preferably, in the configuration of the above (1), in the end turn heating step, the end turn is heated by induction heating. According to this configuration, induction heating is used in the end winding heating step. For this reason, it is easy to adjust the heat load (for example, heating conditions) in consideration of the change in the cross-sectional area in the end winding portion. Further, the end winding portion can be quickly heated.

  (3) Preferably, in the configuration of the above (1) or (2), in the general section heating step, the general section is preferably heated by electric heating. According to this configuration, in the general-portion heating step, electric heating is used. Therefore, the general portion can be quickly heated. In addition, the general part can be easily heated.

  (4) Preferably, in the configuration of the above (3), the general portion is a pair of abutting portions that abut on a pair of electrodes that are spaced apart in the extending direction of the wire in the general portion heating step. And a non-contact portion disposed between the pair of corresponding contact portions, wherein the pair of corresponding contact portions are heated in the end winding portion heating step, and the non-contact portion is provided in the general portion heating step. It is better to adopt a configuration in which heating is performed in

  In the electric heating, an electrode (heating electrode) that can sufficiently heat the general part by its own heat is used, and an electrode (non-heating electrode) that cannot sufficiently heat the general part by its own heat is used. There is. This configuration corresponds to a case where a non-heating electrode is used.

  In the general part heating step, the pair of contact parts are in contact with the pair of electrodes. For this reason, it is difficult to heat the pair of contact portions in the general portion heating step. In this regard, according to this configuration, the pair of contact portions can be heated in the end winding portion heating step. Therefore, the pair of contact portions can be sufficiently heated.

  (5) Preferably, in any one of the above-mentioned constitutions (1) to (4), the general section heating step is performed before the end winding section heating step. The end winding has a smaller cross-sectional area than the general part. For this reason, the end winding portion is easily cooled compared to the general portion. In this regard, according to this configuration, the end winding heating step is performed after the general section heating step. That is, the end winding portion that is easily cooled is heated after the general portion. For this reason, the temperature difference between the general portion and the end winding portion after the end winding portion heating step can be reduced. Therefore, the subsequent process can be performed in a state where the temperature difference between the general portion and the end winding portion is small.

  Further, of the end winding portion, a portion that is continuous with the general portion is a portion having a large cross-sectional area. For this reason, according to this configuration, a portion having a large cross-sectional area in the end winding portion can be heated in advance before the end winding portion heating step.

  (6) Preferably, in the configuration of the above (2), the end turn portion has a maximum portion having the maximum cross-sectional area and a minimum portion having the minimum cross-sectional area; In the heating step, the induction heating is performed on the end winding portion by using a fixed induction heating coil arranged opposite to the end winding portion. It is preferable that the distance from the fixed induction heating coil is set smaller than the distance from the fixed induction heating coil to the minimum part.

  The maximum part has a larger cross-sectional area than the minimum part. For this reason, the maximum part is less likely to be heated than the minimum part. Therefore, in the present configuration, at the time of induction heating, the distance from the fixed induction heating coil to the maximum portion is set smaller than the distance from the fixed induction heating coil to the minimum portion. According to this configuration, uneven heating is unlikely to occur between the maximum part and the minimum part.

  (7) Preferably, in the configuration of the above (2), the end turn has a maximum portion having the maximum cross-sectional area and a minimum portion having the minimum cross-sectional area. In the heating step, the induction heating is performed on the end winding portion by using a moving induction heating coil that is arranged to face the wire and moves relatively to the wire along the extending direction of the wire. In the induction heating, the moving speed of the moving induction heating coil when passing through the maximum portion is set smaller than the moving speed of the moving induction heating coil when passing through the minimum portion. It is better to do.

  Here, the moving induction heating coil and the wire need only be relatively movable. For example, only the movement induction heating coil may move, and the wire may be stationary. Conversely, only the wire may move and the moving induction heating coil may be stationary. Further, the moving induction heating coil and the wire may move in the same direction but at different speeds or in opposite directions.

  The maximum part has a larger cross-sectional area than the minimum part. For this reason, the maximum part is less likely to be heated than the minimum part. Therefore, in the present configuration, at the time of induction heating, the moving speed of the moving induction heating coil when passing through the maximum portion is set smaller than the moving speed of the moving induction heating coil when passing through the minimum portion. . According to this configuration, uneven heating is unlikely to occur between the maximum part and the minimum part.

  (8) Preferably, in the above configuration (1), in the end turn heating step, the end turn is heated using a heat source capable of setting a heating temperature. According to this configuration, it is possible to easily suppress uneven heating of the end winding portion.

  (9) In order to solve the above-mentioned problem, an end turn heating device according to the present invention is used in the method for heating a coil spring having the configuration of (6) above, and is provided with the fixed induction heating coil. Wherein the fixed induction heating coil has a maximum portion heating portion that heats the maximum portion, and a minimum portion heating portion that heats the minimum portion, and when the induction heating is performed, the maximum portion heating portion The distance from the minimum part to the maximum part is set smaller than the distance from the minimum part heating part to the minimum part.

  The fixed induction heating coil of the end turn heating device of the present invention has a maximum portion heating portion and a minimum portion heating portion. At the time of induction heating, the distance from the maximum heating section to the maximum section is set smaller than the distance from the minimum heating section to the minimum section. Therefore, according to the end winding heating device of the present invention, uneven heating is unlikely to occur between the maximum portion and the minimum portion.

  (10) In order to solve the above-mentioned problem, an end turn heating device of the present invention is used for the method of heating a coil spring having the configuration of (7), and is provided with the moving induction heating coil. And further comprising a speed adjusting device for adjusting a moving speed of at least one of the coil spring and the moving induction heating coil, and the speed adjusting device passes through the maximum portion during the induction heating. The moving speed of the moving induction heating coil at that time is set to be smaller than the moving speed of the moving induction heating coil when passing through the minimum part.

  The speed adjusting device of the end turn heating device of the present invention, during induction heating, the moving speed of the moving induction heating coil when passing through the maximum portion, the moving speed of the moving induction heating coil when passing through the minimum portion, Is also set small. Therefore, according to the end winding heating device of the present invention, uneven heating is unlikely to occur between the maximum portion and the minimum portion.

  (11) In order to solve the above-mentioned problems, a coil spring of the present invention is characterized by being manufactured by using the coil spring heating method having any one of the constitutions (1) to (8). In the coil spring of the present invention, uneven heating is unlikely to occur during heating. For this reason, the heterogeneity of the structure of the end winding portion can be suppressed. Therefore, characteristics (for example, hardness) hardly vary over the entire end winding portion. Therefore, the durability is good.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a coil spring which has an end winding part, the heating method of a coil spring which is hard to produce uneven heating, an end winding part heating apparatus, and a coil spring can be provided.

(A) is a top view of the coil spring which is a heating target of the coil spring heating method of the first embodiment. (B) is a side view of the same coil spring. (A) is a top view of a coil spring in a general part heating process of the coil spring heating method of the first embodiment. (B) is a side view of the same coil spring. (A) is a top view of a coil spring in the end winding part heating process of the coil spring heating method of the first embodiment. (B) is a side view of the same coil spring. FIG. 2 is a relationship diagram between θ shown in FIG. 1 and an axial thickness of each part of an end winding portion and a distance from a fixed induction heating coil to each part. (A) is a top view of a coil spring in an end winding part heating process of a coil spring heating method of a second embodiment. (B) is a side view of the same coil spring. FIG. 2 is a relationship diagram between θ shown in FIG. 1, an axial thickness of each part of an end winding portion, and a moving speed of a moving induction heating coil. It is a side view of three coil springs in an end winding part heating process of a coil spring heating method of a third embodiment. It is a side view of four coil springs in the end turn part heating process of the heating method of the coil spring of a fourth embodiment.

  Hereinafter, embodiments of a coil spring heating method, an end turn heating device, and a coil spring of the present invention will be described.

<First embodiment>
[Coil spring]
First, the configuration of the coil spring, which is a heating target of the coil spring heating method of the present embodiment, will be described. FIG. 1A shows a top view of a coil spring to be heated by the coil spring heating method of the present embodiment. FIG. 1B shows a side view of the coil spring.

  As shown in FIGS. 1A and 1B, the coil spring 1 is formed of a spring steel wire W formed in a spiral shape (coil shape). The coil spring 1 includes a pair of upper and lower end winding portions 2 and a general portion 3.

  The pair of end turns 2 forms both ends in the axial direction (vertical direction) of the coil spring 1. Here, the configuration of the pair of end winding portions 2 is the same. Hereinafter, the configuration of the upper end winding portion 2 will be described as a representative of the pair of end winding portions 2.

  As shown by hatching in FIG. 1A, the upper end surface of the upper end turn 2 has a flat shape. That is, as shown by a dotted line in FIG. 1B, the end winding portion 2 is subjected to grinding, cutting, and rolling. Therefore, in the end winding portion 2, the cross-sectional area of the wire W in the direction orthogonal to the extending direction (spiral direction) of the wire W gradually changes.

  More specifically, as shown in FIG. 1A, the tip of the end winding portion 2 is set to θ = 0 ° with the axis A of the coil spring 1 as the center, and θ becomes closer to the general portion 3. It is assumed that it becomes large. The end winding portion 2 is set, for example, in a section where θ = 0 ° or more and 270 ° or less. As θ increases from θ = 0 ° → 90 ° → 180 ° → 270 °, the vertical thickness and cross-sectional area of the wire W increase. At the position of θ = 270 °, the cross section of the wire W has a perfect circular shape. The position of θ = 0 ° in the end winding portion 2 is the minimum portion 21 where the cross-sectional area is minimum. The position of θ = 270 ° in the end winding portion 2 is the maximum portion 20 where the cross-sectional area is maximum.

  The general portion 3 spirally connects the pair of end winding portions 2 to each other. In the general portion 3, the cross-sectional area of the wire W is constant. It is the general part 3 that mainly carries the expansion and contraction function of the coil spring 1.

[Coil spring heating method]
The coil spring 1 is formed by cold forming. That is, the coil spring 1 is manufactured by forming a linear wire W into a spiral shape. Residual stress in the tensile direction remains in the radially (horizontally) inner portion of the coil spring 1. Conversely, residual stress in the compression direction remains on the radially outer portion of the coil spring 1. The method for heating the coil spring of the present embodiment is executed to remove these residual stresses, in other words, to anneal the coil spring 1. The method for heating the coil spring according to the present embodiment includes a general part heating step and an end winding part heating step.

(General part heating process)
FIG. 2A shows a top view of the coil spring in the general portion heating step of the method for heating the coil spring of the present embodiment. FIG. 2B shows a side view of the coil spring. As shown in FIGS. 2A and 2B, in the general-portion heating step, the general-portion heating device 5 applies heating to the coil spring 1. The general-portion heating device 5 includes a pair of upper and lower electrode units 50, a switch 51, and a DC power supply 52.

  The pair of upper and lower electrode portions 50 is electrically connected to upper and lower ends of the general portion 3 of the coil spring 1. Here, the configuration of the pair of electrode units 50 is the same. Hereinafter, the configuration of the upper electrode unit 50 will be described as a representative of the pair of electrode units 50. The electrode unit 50 includes a pair of clamp members 500. The pair of clamp members 500 hold the upper end of the general portion 3 from inside and outside in the radial direction. Each of the pair of clamp members 500 includes an electrode 500a. Each of the pair of electrodes 500a is in contact with the upper end of the general portion 3. The upper electrode unit 50 is electrically connected to a DC power supply 52 via a switch 51. The lower electrode section 50 is electrically connected to a DC power supply 52.

  In this step, a DC voltage is applied from the DC power supply 52 to the general unit 3 by closing the switch 51. Due to the DC voltage, Joule heat based on the internal resistance is generated in the general unit 3. The Joule heat heats the general portion 3 at a temperature within a predetermined range (for example, 430 ° C. or more and 500 ° C. or less) for 1 to 100 seconds.

(End winding heating step)
FIG. 3A shows a top view of the coil spring in the end winding heating step of the coil spring heating method of the present embodiment. FIG. 3B shows a side view of the coil spring. As shown in FIGS. 3A and 3B, in the end turn heating step, induction heating is applied to the coil spring 1 by a pair of upper and lower end turn heating devices 4. Here, the configuration of the pair of end turn heating devices 4 is the same. Hereinafter, the configuration of the upper end turn heating device 4 will be described as a representative of the pair of end turn heating devices 4. The end winding heating device 4 includes a fixed induction heating coil 40, a switch 41, and an AC power supply 42.

  The fixed induction heating coil 40 has a spiral shape. As shown in FIG. 3B, the fixed induction heating coil 40 is arranged above and close to the upper end turn 2. As shown in FIG. 3A, the diameter of the fixed induction heating coil 40 and the diameter of the coil spring 1 are substantially the same. When viewed from above, the fixed induction heating coil 40 includes an arc portion 40a and a straight portion 40b. The arc portion 40a has a 3/4 arc shape. When viewed from above, the arc portion 40a overlaps with the circular coil spring 1. The arc portion 40a is arranged in the section of θ = 0 ° or more and 270 ° or less in FIG. The straight portion 40b has a straight shape. The straight part 40b is arranged between both ends of the arc part 40a. Seen from above, the straight portion 40b does not overlap with the coil spring 1, that is, the general portion 3. The linear portion 40b is disposed in a section where θ is more than 270 ° and less than 360 ° (= 0 °) in FIG.

  On the lower surface of the fixed induction heating coil 40, a maximum heating section 400 and a minimum heating section 401 are arranged. The maximum section heating section 400 is arranged at the position θ = 270 ° shown in FIG. The maximum heating section 400 and the maximum section 20 of the end winding section 2 face each other in the vertical direction. The distance from the maximum heating section 400 to the maximum section 20 is L4. The minimum-portion heating unit 401 is disposed at the position of θ = 0 ° shown in FIG. The minimum part heating part 401 and the minimum part 21 of the end winding part 2 are vertically opposed. The distance from the minimum heating section 401 to the minimum section 21 is L1.

  FIG. 4 shows the relationship between θ shown in FIG. 1 and the axial thickness of each part of the end winding part and the distance from the fixed induction heating coil to each part. As shown in FIG. 4, the thickness D of the wire W in the axial direction (however, the axial direction (vertical direction) of the coil spring 1) is θ = 0 ° → 90 ° → 180 ° → 270 ° as θ increases. , D1 → D2 → D3 → D4. Similarly, the cross-sectional area of the wire W increases as θ = 0 ° → 90 ° → 180 ° → 270 ° as θ increases, such as S1 → S2 → S3 → S4.

  On the other hand, the distance (axial distance) L from the fixed induction heating coil 40 to the end turn portion 2 is L1 → L2 as θ = 0 ° → 90 ° → 180 ° → 270 °. → L3 → L4.

  As described above, the fixed induction heating coil 40 is arranged such that the closer the cross-sectional area of the wire W becomes to the end turn 2, the closer to the end turn 2. The fixed induction heating coil 40 is electrically connected to an AC power supply 42 via a switch 41.

  In this step, an AC voltage is applied from the AC power supply 42 to the fixed induction heating coil 40 by closing the switch 41. The AC voltage generates Joule heat in the end winding 2 based on the eddy current. The end winding 2 is heated by the Joule heat at a temperature within a predetermined range (for example, 360 ° C. or more and 600 ° C. or less) for 1 to 100 seconds.

  As described above, the residual stress of the coil spring 1 is removed by the coil spring heating method of the present embodiment. After the residual stress is removed, a process such as hot setting is performed on the coil spring 1 using the residual heat of the coil spring heating method of the present embodiment.

[Effects]
Next, the effects of the coil spring heating method, the end turn heating device, and the coil spring according to the present embodiment will be described. The heating method of the coil spring of the present embodiment includes a general part heating step and an end winding part heating step. For this reason, the end winding part 2 and the general part 3 can be heated separately. Therefore, the heating condition for the end winding portion 2 and the heating condition for the general portion 3 can be set separately. Therefore, the end winding part 2 and the general part 3 can be heated at a temperature within a predetermined range, respectively. For this reason, uneven heating is unlikely to occur in the coil spring 1.

  Further, in the end winding portion heating step, the heat load is adjusted in consideration of changes in the cross-sectional areas S1 to S4 in the end winding portion 2. For this reason, each part of the end winding part 2 can be heated at a temperature within a predetermined range. Therefore, uneven heating is unlikely to occur in the end winding portion 2.

  Further, according to the coil spring heating method, the end turn heating device 4 and the coil spring 1 of the present embodiment, induction heating is used in the end turn heating step. Therefore, it is easy to adjust the heat load (specifically, the heating condition) in consideration of the change in the cross-sectional areas S1 to S4 in the end winding portion 2. Further, the end winding portion 2 can be quickly heated. In addition, in the general part heating step, electric heating is used. Therefore, the general section 3 can be quickly heated. Further, the general portion 3 can be easily heated.

  Further, the end winding portion 2 has a smaller cross-sectional area than the general portion 3. For this reason, the end winding portion 2 is more easily cooled than the general portion 3. In this regard, according to the coil spring heating method of the present embodiment, the end turn heating step is performed after the general section heating step. That is, the end winding portion 2 that is easily cooled is heated after the general portion 3. For this reason, the temperature difference between the general section 3 and the end winding section 2 after the end winding section heating step can be reduced. Therefore, the subsequent process can be performed in a state where the temperature difference between the general section 3 and the end winding section 2 is small. Further, in the end winding portion 2, continuous with the general portion 3 is a maximum portion 20 having a large cross-sectional area. Therefore, the maximum portion 20 can be heated in advance before the end winding portion heating step.

  Further, the maximum section 20 of the end winding section 2 has a larger cross-sectional area than the minimum section 21. Therefore, the maximum portion 20 is less likely to be heated than the minimum portion 21. Therefore, in the end turn heating step of the coil spring heating method of the present embodiment, the distance L4 from the maximum heating section 400 to the maximum section 20 is changed from the minimum heating section 401 to the minimum section 21 during induction heating. Is set smaller than the distance L1. Therefore, uneven heating is unlikely to occur between the maximum portion 20 and the minimum portion 21.

  Further, according to the coil spring 1 of the present embodiment, uneven heating is unlikely to occur during heating. For this reason, the heterogeneity of the structure of the end winding portion 2 can be suppressed. Therefore, characteristics (for example, hardness) hardly vary over the entire end winding portion 2. Therefore, the durability is good.

<Second embodiment>
The difference between the coil spring heating method, the end turn heating device, and the coil spring of the present embodiment and the coil spring heating method, the end turn heating device, and the coil spring of the first embodiment is that It is only the configuration of the heating device. Here, only the differences will be described.

  FIG. 5A shows a top view of the coil spring in the end turn heating step of the coil spring heating method of the present embodiment. FIG. 5B shows a side view of the coil spring. 3A and 3B are denoted by the same reference numerals.

  As shown in FIGS. 5A and 5B, in the end turn heating step, the coil spring 1 is subjected to induction heating by the end turn heating device 4. The end winding heating device 4 includes a switch 41, an AC power supply 42, a movement induction heating coil 43, and a speed adjusting device 44.

  The speed adjusting device 44 includes a motor (not shown) and a table 440. The coil spring 1 is fixed on the upper surface of the table 440. The table 440 is rotatable around the axis A of the coil spring 1 by the driving force of the motor.

  The moving induction heating coil 43 is disposed above the wire W of the end winding portion 2. The moving induction heating coil 43 is fixed. For this reason, the distance (axial direction (vertical direction) distance) from the movement induction heating coil 43 to the end winding portion 2 is constant. The rotation of the table 440 allows the movement induction heating coil 43 to relatively move with respect to the end winding portion 2.

  FIG. 6 shows the relationship between θ shown in FIG. 1 and the axial thickness of each portion of the end winding portion and the moving speed of the moving induction heating coil. As shown in FIG. 6, the thickness D of the wire W in the axial direction (however, the axial direction (vertical direction) of the coil spring 1) is θ = 0 ° → 90 ° → 180 ° → 270 ° as θ increases. , D1 → D2 → D3 → D4. Similarly, the cross-sectional area of the wire W increases as θ = 0 ° → 90 ° → 180 ° → 270 ° as θ increases, such as S1 → S2 → S3 → S4.

  On the other hand, the moving speed V of the moving induction heating coil 43 decreases as θ = 0 ° → 90 ° → 180 ° → 270 ° as θ increases, such as V1 → V2 → V3 → V4.

  As described above, the moving speed of the movement induction heating coil 43 is set to be slower as the cross-sectional area of the wire W becomes larger with respect to the end winding portion 2. The moving induction heating coil 43 is electrically connected to an AC power supply 42 via the switch 41.

  In this step, an AC voltage is applied from the AC power supply 42 to the moving induction heating coil 43 by closing the switch 41. Due to the AC voltage, Joule heat based on the eddy current is locally generated in a portion of the end winding portion 2 directly below the movement induction heating coil 43.

  In this step, the table 440 is rotated. By rotating the table 440, the movement induction heating coil 43 relatively moves from the minimum part 21 to the maximum part 20 along a 3/4 arc-shaped trajectory along the extending direction of the wire W. The end winding portion 2 is heated at a temperature within a predetermined range (for example, 360 ° C. or more and 600 ° C. or less).

  The method for heating the coil spring, the end turn heating device, and the coil spring of the present embodiment, and the method for heating the coil spring, the end turn heating device, and the coil spring of the first embodiment are related to portions having a common configuration. Has a similar effect.

  Further, according to the heating method of the coil spring of the present embodiment, the moving speed V4 of the moving induction heating coil 43 when passing through the maximum portion 20 is set to the moving induction heating coil when passing through the minimum portion 21 during induction heating. 43 is set lower than the moving speed V1. Therefore, uneven heating is unlikely to occur between the maximum portion 20 and the minimum portion 21.

<Third embodiment>
The difference between the coil spring heating method, the end turn heating device, and the coil spring of the present embodiment and the coil spring heating method, the end turn heating device, and the coil spring of the first embodiment is that a plurality of coils are provided. The point is that the end turns of the spring are heated at a time. Here, only the differences will be described.

  FIG. 7 shows a side view of the three coil springs in the end turn heating step of the coil spring heating method of the present embodiment. 3A and 3B are denoted by the same reference numerals.

  As shown in FIG. 7, in the end turn heating step, four end turn heating devices 4a to 4d and three coil springs 1a to 1c are alternately arranged left and right in the horizontal direction. Specifically, the four end turn heating devices 4a to 4d and the three coil springs 1a to 1c are connected to the end turn heating device 4a → the coil spring 1a → the end turn heating device 4b → the coil spring 1b → the end turn. The section heating device 4c → the coil spring 1c → the end winding portion heating device 4d are arranged in this order. If the number of coil springs 1a to 1c is N (N is a natural number of 1 or more), the number of coil winding heaters 4a to 4d is N + 1.

  A pair of end windings 2 adjacent in the axial direction (left-right direction) have the right and left positions of θ = 90 ° and θ = 270 ° so that the θ = 0 ° positions shown in FIG. The positions are set such that the positions of θ = 270 ° and the position of θ = 90 ° are opposed to each other in the left-right direction such that θ = 180 ° are opposed to each other in the left-right direction so as to face each other.

  The left end turn 2 of the left end coil spring 1a is heated by the left end end turn heating device 4a. The right end turn 2 of the left end coil spring 1a and the left end turn 2 of the center coil spring 1b are heated by the end turn heating device 4b. The right end turn 2 of the center coil spring 1b and the left end turn 2 of the right end coil spring 1c are heated by the end turn heating device 4c. The right end turn 2 of the right end coil spring 1c is heated by the right end end turn heating device 4d. The distance from the fixed induction heating coil 40 of each of the end turn heating devices 4a to 4d to the end turn 2 of each of the coil springs 1a to 1c is set in the same manner as in FIG. An AC voltage is applied from the AC power supply 42 to the fixed induction heating coils 40 of the end turn heating devices 4a to 4d at the same time. That is, the three coil springs 1a to 1c are simultaneously heated.

  The method for heating the coil spring, the end turn heating device, and the coil spring of the present embodiment, and the method for heating the coil spring, the end turn heating device, and the coil spring of the first embodiment are related to portions having a common configuration. Has a similar effect.

  According to this embodiment, in the end winding heating step, the plurality of coil springs 1a to 1c can be heated simultaneously. For this reason, the productivity of the coil springs 1a to 1c is improved. Further, the two coil springs 1a and 1b can be heated simultaneously by the single end turn heating device 4b. Similarly, the two coil springs 1b and 1c can be heated simultaneously by a single end turn heating device 4c.

<Fourth embodiment>
The difference between the coil spring heating method, the end turn heating device, and the coil spring of the present embodiment and the coil spring heating method, the end turn heating device, and the coil spring of the second embodiment is that a plurality of coils are provided. The point is that the end turns of the spring are heated at a time. Here, only the differences will be described.

  FIG. 8 shows a side view of the four coil springs in the end turn heating step in the coil spring heating method of the present embodiment. 3A and 3B are denoted by the same reference numerals.

  As shown in FIG. 8, in the end turn heating step, five end turn heating devices 4e to 4i and four coil springs 1d to 1g are alternately arranged on the left and right in the horizontal direction. Specifically, the five end turn heating devices 4e to 4i and the four coil springs 1d to 1g comprise the end turn heating device 4e → the coil spring 1d → the end turn heating device 4f → the coil spring 1e → the end turn. Part heating device 4g → coil spring 1f → end winding heating device 4h → coil spring 1g → end winding heating device 4i. When the number of coil springs 1d to 1g is N (N is a natural number of 1 or more), the number of coil winding heaters 4e to 4i is N + 1.

  A pair of end turns 2 adjacent in the axial direction (left-right direction) are arranged such that θ = 0 ° positions shown in FIG. 1 oppose each other in the left-right direction, and θ = 90 ° positions oppose each other in the left-right direction. , Θ = 180 ° are opposed in the left-right direction, and θ = 270 ° positions are opposed in the left-right direction.

  The left end turn 2 of the left end coil spring 1d is heated by the left end end turn heating device 4e. The right end turn 2 of the left end coil spring 1d and the left end turn 2 of the center left coil spring 1e are heated by the end turn heating device 4f. The right end turn 2 of the center left coil spring 1e and the left end turn 2 of the center right coil spring 1f are heated by the end turn heating device 4g. The right end turn 2 of the center right coil spring 1f and the left end turn 2 of the right end coil spring 1g are heated by the end turn heating device 4h. The right end turn 2 of the right end coil spring 1g is heated by the right end end turn heating device 4i.

  Each of the coil springs 1d to 1g is fixed. The moving induction heating coil 43 of each of the end winding heating devices 4e to 4i has a 3/4 arc-shaped trajectory along the extending direction of the wire W by a speed adjusting device (not shown). To move relatively.

  The moving speed of the movement induction heating coil 43 of each of the end turn heating devices 4e to 4i is set in the same manner as in FIG. An AC voltage is applied from the AC power supply 42 to the moving induction heating coil 43 of each of the end turn heating devices 4e to 4i at the same time. That is, the four coil springs 1d to 1g are simultaneously heated.

  The method of heating the coil spring, the end turn heating device, and the coil spring of the present embodiment, and the method of heating the coil spring, the end turn heating device, and the coil spring of the second embodiment are related to portions having a common configuration. Has a similar effect.

  According to the present embodiment, in the end winding portion heating step, the plurality of coil springs 1d to 1g can be heated simultaneously. For this reason, the productivity of the coil springs 1d to 1g is improved. Further, the two coil springs 1d and 1e can be heated simultaneously by a single end turn heating device 4f. Similarly, the two coil springs 1e and 1f can be heated simultaneously by a single end turn heating device 4g. Similarly, the two coil springs 1f and 1g can be heated simultaneously by a single end turn heating device 4h.

<Others>
The embodiments of the coil spring heating method, the end turn heating device, and the coil spring according to the present invention have been described above. However, embodiments are not particularly limited to the above embodiments. Various modifications and improvements that can be performed by those skilled in the art are also possible.

  In the above embodiment, the end winding 2 is heated by induction heating. However, heating may be performed by a salt bath, infrared irradiation, plasma irradiation, a burner, pressing of a holding mold, hot air blowing, superheated steam, a fluidized bed, or the like.

  Further, in the case of a heat source (for example, a salt bath, pressing of a heating and holding mold, blowing of hot air, superheated steam, or a fluidized bed) capable of setting the heating temperature of the end winding portion 2, the entire end winding portion 2 can be easily formed. It can be heated to a temperature within a predetermined range.

  In the case of a heat source (for example, infrared irradiation, plasma irradiation, burner) in which the heating temperature of the end winding part 2 cannot be set, by adjusting the distances L1 to L4 as in the first embodiment, or in the second embodiment. By adjusting the moving speeds V1 to V4 as described above, the entire end winding portion 2 can be heated to a temperature within a predetermined range.

  Further, by adjusting the output of the heat source, the entire end winding portion 2 may be heated to a temperature within a predetermined range. Specifically, as the cross-sectional area of the wire W increases, the output may be increased to set the entire end winding portion 2 to a temperature within a predetermined range. Further, an AC power supply may be used instead of the DC power supply 52 as a power supply for the general-portion heating device 5.

  Further, a robot may be arranged instead of the motor and the table 440 of the speed adjusting device 44 of the second embodiment. That is, the moving speed of the movement induction heating coil 43 may be controlled by a robot.

  Further, as shown by a dotted line in FIG. 4, the change in the distance L may be a step shape instead of a slope shape (solid line). Similarly, as shown by a dotted line in FIG. 6, the change in the moving speed V may be a step shape instead of a slope shape (solid line). In these cases, the number of steps is not particularly limited.

  Further, the end turn portion 2 of the coil spring 1 may be arranged on only one side in the axial direction. Further, the cross-sectional shape of the wire W may be a polygonal shape such as an elliptical shape, an elliptical shape, a triangular shape, or a quadrangular shape, in addition to a perfect circular shape. Further, the wire W may be solid (rod-shaped) or hollow (tubular).

  The material of the wire W is not particularly limited. The wire W preferably has conductivity. For example, carbon steel, stainless steel, chromium vanadium steel, silicon chrome steel, silicon manganese steel, spring steel, copper alloy, etc. may be used. Further, as the spring steel, an oil-tempered wire for a spring (SWOSC-B, SAE9254, etc.), a hardened steel for a spring (SUP9, SUP10, SUP12, etc.) can be used.

  Further, the pair of end turns 2 may be heated at the same time. Moreover, you may heat one by one. Further, the length of the end winding portion 2 is not particularly limited. For example, the section may be set to a section between θ = 0 ° and 180 ° or a section between θ = 0 ° and 360 °. Further, the direction of the axis A of the coil spring 1 during heating may be vertical or horizontal.

  In the general part heating step of the first embodiment, as shown in FIGS. 2A and 2B, the part of the general part 3 connected to the upper end winding part 2 is formed from both sides in the radial direction. It is sandwiched between a pair of electrodes 500a. In addition, a portion of the general portion 3 that is continuous with the lower end winding portion 2 is sandwiched by a pair of electrodes 500a from both sides in the radial direction.

  When the general portion 3 is not heated by the heat generated by the electrode 500a itself (when the electrode 500a is a non-heated electrode), the portions in contact with the electrodes 500a (a pair of abutting portions) are sufficiently removed in the general portion heating step. Can not be heated. In this case, in the end winding portion heating step, the pair of contact portions may be heated. In this case, the pair of contact portions can be sufficiently heated.

  Further, the coil spring 1 was moved in the second embodiment, and the movement induction heating coil 43 was moved in the fourth embodiment. However, both the coil spring 1 and the movement induction heating coil 43 may be moved in the same direction but at different speeds or in opposite directions. The number of coil springs 1a to 1g in the third and fourth embodiments is not particularly limited.

  Further, in the above-described embodiment, the general section heating step is performed first, and the end winding section heating step is performed later, but the end winding section heating step may be performed first, and the general section heating step may be performed later. Good.

  In the above embodiment, the coil spring heating method and the end turn heating device of the present invention are used for annealing a coil spring manufactured by cold forming. However, the coil spring heating method and the end turn heating device of the present invention may be used for quenching, tempering, and the like of a coil spring manufactured by cold forming. Further, it may be used for tempering a coil spring manufactured by hot forming. Moreover, you may use for hot setting, warm shot peening, baking of a coating, etc. Further, the coil spring 1 after heating may be subjected to creep tempering instead of hot setting.

  Further, in the first embodiment, as shown in FIGS. 3A and 3B, a pair of upper and lower end winding heating devices 4 are arranged on both upper and lower sides of the coil spring 1. However, a plurality of pairs of small end winding heating devices 4 may be arranged on both upper and lower sides of the coil spring 1. For example, a plurality of end turn heating devices 4 are arranged above the upper end turn 2 at a predetermined angle (30 °, 45 °, 60 °, 90 °, 120 °, etc.) in the circumferential direction. You may. In this case, as shown by the distances L1 to L4 in FIG. 3B, the plurality of fixed induction heating coils 40 are closer to the end winding 2 as the cross-sectional area of the wire W becomes larger with respect to the end winding 2. And so on. The same applies to a plurality of end turn heating devices 4 arranged below the coil spring 1.

  In the second embodiment, as shown in FIGS. 5A and 5B, the moving speed of the movement induction heating coil 43 is set such that the cross-sectional area of the wire W is larger than that of the end winding 2. It was set to be as slow as possible. However, the moving speed of the movement induction heating coil 43 in the circumferential direction may be constant. In this case, even if the distance from the movement induction heating coil 43 to the end winding portion 2 is set such that the larger the cross-sectional area of the wire W, the shorter the distances L1 to L4, as shown in FIG. Good. That is, the moving induction heating coil 43 may be moved in the circumferential direction at a constant moving speed while moving in the axial direction (adjusting the distances L1 to L4).

  Further, in the fourth embodiment, as shown in FIG. 8, a pair of coil springs 1d to 1g adjacent in the axial direction are arranged such that the winding directions of the wires are opposite to each other. However, you may arrange | position all the coil springs 1d-1g so that the winding direction of a wire may correspond. In this case, the rotation directions of the adjacent coil springs 1d to 1g may be opposite to each other.

1: coil spring, 1a to 1g: coil spring, 2: end winding section, 3: general section, 4: end winding section heating apparatus, 4a to 4i: end winding section heating apparatus, 5: general section heating apparatus.
20: maximum part, 21: minimum part, 40: fixed induction heating coil, 40a: arc part, 40b: linear part, 41: switch, 42: AC power supply, 43: moving induction heating coil, 44: speed adjustment device, 50 : Electrode part, 51: switch, 52: DC power supply.
400: maximum part heating part, 401: minimum part heating part, 440: table, 500: clamp member, 500a: electrode.
A: axis, D: axial thickness, L: distance, L1 to L4: distance, S1 to S4: cross-sectional area, V: moving speed, V1 to V4: moving speed, W: wire.

Claims (11)

It consists of a spirally extending wire,
The cross-sectional area of the wire in a direction orthogonal to the extending direction of the wire is defined as a cross-sectional area,
An end winding part whose cross-sectional area changes along the extending direction;
A general portion connected to the end winding portion and having a constant cross-sectional area along the extending direction;
A coil spring having
A method of heating a coil spring to be heated,
Adjusting the heat load in consideration of the change of the cross-sectional area, an end winding heating step of heating the end winding,
A general part heating step performed before or after the end winding part heating step, and heating the general part,
A method for heating a coil spring, comprising:   The method for heating a coil spring according to claim 1, wherein in the end winding heating step, the end winding is heated by induction heating.   The method for heating a coil spring according to claim 1, wherein, in the general part heating step, the general part is heated by electric heating. The general portion includes, in the general portion heating step, a pair of contact portions that contact a pair of electrodes that are separated from each other in the extending direction of the wire and a non-contact portion that is disposed between the pair of corresponding contact portions. And a contact portion,
The pair of corresponding contact portions are heated in the end winding portion heating step,
The method for heating a coil spring according to claim 3, wherein the non-contact portion is heated in the general portion heating step.   The method for heating a coil spring according to any one of claims 1 to 4, wherein the general portion heating step is performed before the end winding portion heating step. The end winding portion has a maximum portion having the maximum cross-sectional area and a minimum portion having the minimum cross-sectional area,
In the end turn heating step, the induction heating is performed on the end turn using a fixed induction heating coil disposed opposite to the end turn, and the fixed induction heating coil is provided at the time of the induction heating. The method for heating a coil spring according to claim 2, wherein a distance from the fixed induction heating coil to the minimum part is set smaller than a distance from the fixed induction heating coil to the minimum part. The end winding portion has a maximum portion having the maximum cross-sectional area and a minimum portion having the minimum cross-sectional area,
In the end turn heating step, a moving induction heating coil that is arranged to face the wire and moves relatively to the wire along the extending direction of the wire is used to attach the end turn to the end turn. Induction heating is performed, and during the induction heating, the moving speed of the moving induction heating coil when passing through the maximum portion is set to be smaller than the moving speed of the moving induction heating coil when passing through the minimum portion. 3. The method for heating a coil spring according to claim 2, wherein the heating is performed.   The heating method for the coil spring according to claim 1, wherein in the end winding heating step, the end winding is heated using a heat source capable of setting a heating temperature. It is used for the heating method of the coil spring according to claim 6, and is an end turn heating device including the fixed induction heating coil,
The fixed induction heating coil has a maximum heating unit that heats the maximum, and a minimum heating unit that heats the minimum.
In the induction heating, the distance from the maximum heating section to the maximum section is set smaller than the distance from the minimum heating section to the minimum section. It is used for the heating method of the coil spring according to claim 7, It is an end turn heating device provided with the movement induction heating coil,
Further, a speed adjusting device that adjusts the moving speed of at least one of the coil spring and the movement induction heating coil,
At the time of the induction heating, the speed adjustment device, the moving speed of the moving induction heating coil when passing through the maximum portion, than the moving speed of the moving induction heating coil when passing through the minimum portion, End winding heating device to be set small.   A coil spring manufactured by using the coil spring heating method according to claim 1.

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