KR20020019737A - coil spring and manufacturing process thereof - Google Patents

Abstract

PURPOSE: A coil spring and a method for manufacturing the same are provided to improve the endurance of the coil spring by removing the residual stress and brittleness before coiling wire material which is used for manufacturing the coil spring. CONSTITUTION: A circular-type wire material is gradually rolled through first rollers and second rollers such that a sectional area thereof is formed in a taper shape(N10,N11). The rolled wire material passes through a heater, so that the rolled wire material is subject to a tempering process at the temperature of 380 to 400°C for 10 to 30 minutes(N12). Then, the coil is prepared by using the wire material. At this time, the difference between inner and outer sectional areas of the wire material is compensated for by using a difference of deformation according to a difference of the radius of inner and outer radius of the coil spring, thereby uniformly forming the interval between pitches(N13). Then, the coil spring is subject to the tempering process at the temperature of 400 to 420°C more than 30 minutes(N14). After that, a setting process is carried out for setting the coil spring(N14a) and both ends of the coil spring is polished(N15). After performing a shot peening process with respect to the coil spring(N16), the setting process is again carried out for maintaining the tolerance at the free end of the coil spring(N16a). Then, the coil spring is subject to the tempering process at a lower temperature for removing the stress thereof(N17).

Description

Coil spring and manufacturing method thereof

The present invention relates to a coil spring and a method of manufacturing the same, and more particularly, to prevent the sudden change of the cross-sectional shape by gradual molding in roller forming to change the cross-sectional shape of the wire rod to minimize the stress in the metal structure, The present invention relates to a coil spring and a method of manufacturing the same, which allow tempering heat treatment before winding to make a spring to remove residual stress and improve durability.

In general, the coil spring is made into a desired number of turns while forming a coil at a predetermined bending angle using a forming tool positioned by a servo motor or a cam after straightening by passing a wire rod in a straightener.

As such, wire rods used in the manufacture of coil springs are mainly used in the form of circular or rectangular cross-sections. Particularly, since rectangular wire rods are compression molded at a time by a single forming roller, stress is generated due to rapid changes in the cross section. When the coil spring is used for the coil spring, there is a problem in that the service life is shortened due to the residual stress under the use conditions in which heavy loads are frequently applied, such as a press die, a vehicle suspension system, and an intake / exhaust valve of an engine.

That is, the coil spring 20 manufactured by the conventional rectangular wire in Figs. 1 and 2 is shown in the drawing, and as shown therein, the fine edges 22a are sharp at the sharp edges 22a in the process of forming the wire 22 into a rectangular shape. Cracks are generated, and coil springs manufactured using wire rods having such fine cracks have short lifespan as fine cracks develop into large cracks due to repeated loads.

In addition, the conventional coil spring 20 is severely changed in the free field of the spring due to the repeated load, and when the bending of the inner portion and the outer portion of the spring is not horizontal, uneven compression load occurs when the load is received There was a problem.

In other words, when coiling using a square wire, when the coil spring 20 is compressed as shown in FIG. 2, there is a difference in deformation amount inside and outside due to the difference in the inner and outer radii of the coil spring. There was a problem that a gap 22b occurred between them.

In addition, since the heat treatment for removing the stress before coiling the wire rod was not performed, there is a problem that cracks are generated by the stress remaining in the coiling process.

The present invention has been made to solve the above problems, the object is to remove the residual stress and brittleness before coiling the wire used as the material of the spring, the coil spring that can improve the durability of the coil spring and its To provide a manufacturing method.

Coil spring for achieving the object of the present invention is formed so that the radius of the small diameter portion of the wire rod located inside the spring is smaller than the radius of the large diameter portion of the wire rod is located outside the spring, the tangential form of the small diameter portion and large diameter portion The row has a feature that the tapered surfaces on both sides are formed in a plane.

On the other hand, the manufacturing method of the coil spring for achieving the object of the present invention is to gradually roll the circular wire rod by the primary forming roller and the secondary forming roller so that the cross-sectional shape is formed into a tapered shape Process, the primary tempering process while passing the rolled wire rod through the heater, and winding the coil by using the primary tempered wire rod, the difference between the inner and outer cross-sectional area of the wire rod according to the difference in the inner and outer radii of the coil spring Compensating for the difference in deformation to make the interval between pitches uniform; process of secondary winding of wound coil spring; process of polishing both ends of secondary tempered coil spring; and polished coil spring Process of short-pinning, process of removing stress by tempering the short-pinned coil spring, and anticorrosive treatment by painting the inside and outside of the cold-tempered coil spring. Has configured features.

1 is a longitudinal cross-sectional view of a free field state of a coil spring manufactured using a conventional rectangular wire rod.

2 is a longitudinal cross-sectional view of a compressed state of a coil spring manufactured using a conventional rectangular wire rod.

3 is a view schematically showing a primary rolling process of the coil spring manufacturing process according to the present invention;

Figure 4 schematically shows a secondary rolling process and heat treatment process of the coil spring manufacturing process according to the present invention

5 is a cross-sectional view showing that the wire rod is roller formed by the primary forming roller during the manufacturing process of the coil spring according to the present invention.

6 is a cross-sectional view showing that the wire rod is roller-formed by the secondary forming roller during the manufacturing process of the coil spring according to the present invention.

FIG. 7 is a cross-sectional view taken along line A-A of FIG. 3, which shows a cross-sectional view of a wire rod before rolling in the manufacturing process of the coil spring according to the present invention.

8 is a cross-sectional view of the wire rod formed by the primary forming roller during the manufacturing process of the coil spring according to the present invention.

9 is a cross-sectional view of the wire rod formed by the secondary forming roller during the manufacturing process of the coil spring according to the present invention.

10 is a longitudinal cross-sectional view of a free field state of the coil spring according to the present invention.

11 is a longitudinal cross-sectional view of a compressed state of the coil spring according to the present invention.

12 is a process chart for explaining the manufacturing method of the coil spring according to the present invention.

* Explanation of Signs of Major Parts of Drawings *

100: coil spring 30: wire rod

37: small diameter part R, r: radius

36: large diameter part 32, 34: tapered surface

60,62: 1st forming roller 70,72: 2nd forming roller

H: heater

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 9, the coil spring according to the present invention is formed such that the radius r of the small diameter portion 37 of the wire rod 30 is smaller than the radius R of the large diameter portion 36. 37) and the tapered surfaces 32 and 34 on both sides connecting the large-diameter portion 36 in a tangential form were formed in a plane.

That is, the wire 30 is a material used when the coil spring 100 is wound, and the large diameter part 36 is less deformed than the small diameter part 37 when the coil spring 100 is located outside the coil spring 100 to be bent. When the spring 100 is completed, the tapered surfaces 32 and 34 on both sides facing in the spring pitch direction are formed to have a predetermined interval.

On the other hand, the manufacturing method of the coil spring according to the present invention is the primary wire forming roller 60 as shown in Figure 3 and Figure 4 of the circular wire (30) as shown in the accompanying drawings 62) and the secondary forming rollers (70, 72) to gradually roll the process (N10, N11) to form a tapered shape of the cross-sectional shape as shown in Figs. 8 and 9, and the rolled wire 30 While passing through the heater (H), the first tempering treatment (N12) in the range of 10 to 30 minutes at 380 ° C to 400 ° C and the coil by using the primary tempered wire (30) to wound the wire (30) Compensation for the difference between the inner and outer cross-sectional area of the coil) by the difference in the deformation amount according to the difference in the inner and outer radii of the coil spring 100 to make the interval between pitches uniform (N13), and the wound coil spring 100 at 400 ° C. Second tempering treatment (N14) for 30 minutes or more at -420 DEG C, a step N15 for polishing both end surfaces of the secondary tempering coil spring 100, and Process (N16) of short-pinning the coiled spring (100), a step (N17) of removing the stress by tempering the short-pinned coil spring (100) at 200 ° C. to 230 ° C. for at least 10 minutes, and It is composed of a process (N18) for the anticorrosive treatment by painting the inside and outside of the coiled coil spring 100.

Here, the primary forming rollers 60 and 62 and the secondary forming rollers 70 and 72 have a half cross-sectional shape of the wire 30 to be molded on the outer circumferential surface as shown in FIGS. 5 and 6, respectively. Annular grooves 60a, 62a, 70a, 72a are formed, respectively.

In FIG. 3, reference numeral 40 denotes a first bobbin, 50 denotes a second bobbin, and reference numeral 52 in FIG. 4 denotes a third bobbin.

Hereinafter, the operation according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3, the primary forming roller 60 as shown in FIG. 5 is provided while unwinding the wire 30 from the first bobbin 40 in which the circular wire 30 is wound. When primary rolling is performed by 62, the circular wire 30 is compressed and wound around the second bobbin 50 while being molded as shown in FIG. (Step N10 of Fig. 12)

Thereafter, as shown in FIG. 4, the second bobbin 50 on which the primary rolled wire 30 is wound is reset and then unrolled to be secondary rolled by the secondary forming rollers 70 and 72. Then, the primary processed wire rod 30 is more flat compression molded to form a cross section as shown in FIG. (Step N11 of Fig. 12)

At this time, the radius (r) of the small diameter portion 37 of the wire rod 30 is formed smaller than the radius (R) of the large diameter portion 36, the tapered surface of both sides connecting the small diameter portion 37 and the large diameter portion 36 in a tangential form 32 and 34 are formed flat.

In addition, when the primary rolled heat treatment is performed at 380 ° C. to 400 ° C. for 30 minutes or more while passing the secondary rolled wire 30 through a tubular heater H as shown in FIG. 4, in the process of rolling. After the remaining residual stress is removed, it is wound around the third bobbin 52. (Step N12 of Fig. 12)

Next, the small diameter portion 37 is positioned inside the coil spring 100 while the first bobbin wire 30 is wound with the third bobbin 52 wound on the forming machine (not shown). When the large diameter portion 36 is bent and cut after a predetermined number of turns so as to be positioned on the outside, the coil spring 100 is completed, and as shown in FIG. 10, the inner and outer radii of the coil spring 100 are formed. Inevitably, there is a difference in the amount of deformation inside and outside due to the difference. Since the inside of the small diameter portion 37 having a small cross-sectional area and the large diameter portion 36 having a large cross-sectional area are formed on the outside, the difference in deformation amount is compensated for. As shown in FIG. 11, when the coil spring 100 is compressed, a gap is not generated between the coil springs 100 and the coil spring 100 is compressed to show a uniform compressive load. (Step N13 of Fig. 12)

At this time, when the wound coil spring 100 is subjected to secondary tempering heat treatment again at 400 ° C. to 420 ° C. for 30 minutes or more, the stress remaining in the coiling process is removed, and the fragile property is improved. (N14 in Fig. 12)

In addition, the ductility of the material is increased by performing a primary setting process of bringing the heat-treated coil spring 100 into close contact with a hydraulic setter. (N14a in Fig. 12)

Then, when both ends of the secondary tempered coil spring 100 are polished while maintaining the polishing angle within ± 2 °, both ends of the coil spring 100 are formed flat. (Step N15 of Fig. 12)

In the above state, when a large number of forced small particles are sprayed on the surface of the coil spring 100, which is polished at both ends, for example, at a speed of 20 to 50 cm / sec, the cold stress is applied while the compressive stress is applied to the surface. (Step N16 of Fig. 12)

Then, the secondary setting step of pressing the hydraulic setter so that the tolerance of the free end is consistently performed is prevented from deformation of the coil spring. (Step N16a in Fig. 12).

Then, when the short-pinned coil spring 100 is tempered at 200 ° C. to 230 ° C. for at least 10 minutes at low temperature, the stress received in the short-pinning process is removed. (Step N17 of Fig. 12)

Finally, when painting the inner and outer sides of the low temperature tempered coil spring 100, it is possible to prevent the occurrence of rust. (Step N18 of Fig. 12)

As described above, since the cross-sectional shape of the wire rod used in the manufacture of the coil spring is formed in a round shape, it is possible to suppress the occurrence of cracks during bending, thereby extending the life of the coil spring. Of course, since it is configured to form gradually over two times in the course of rolling the wire rod, it is possible to prevent the stress deformation caused by the abrupt change of the cross section, and the inner and outer radius that can be generated when bending the coil spring In consideration of the difference in deformation between the inside and the outside due to the difference, the cross-sectional shape of the wire rod is formed into a tapered shape, so that the gap can be minimized during compression of the coil spring to improve the accuracy. It has the effect of obtaining a uniform compressive load, and before coiling the wire Because it is configured to a tempering treatment for removing the force which produces the effect of improving the durability by minimizing cracking in the coiling process.

Claims (2)

In the coil spring, the radius (r) of the small diameter portion 37 of the wire rod 30 that is located inside the coil spring 100 is located on the outside of the coil spring 100 of the large diameter portion ( 36) The coil spring is formed to be smaller than the radius R, and the tapered surfaces 32 and 34 on both sides connecting the small diameter portion 37 and the large diameter portion 36 in a tangential shape are formed in a plane. . In the coil spring manufacturing method, the circular wire rod 30 is gradually rolled by the primary forming rollers 60 and 62 and the secondary forming rollers 70 and 72 to form a cross section thereof. (N10, N11) for forming the tapered shape; A first tempering treatment in a range of 10-30 minutes at 380 ° C to 400 ° C while passing the rolled wire rod 30 through the heater H (N12); By winding the coil using the primary tempered wire 30, the gap between pitches is compensated by the difference in the amount of deformation according to the difference in the inner and outer radii of the coil spring 100. Process (N13) to make uniform; A secondary tempering treatment of the wound coil spring 100 at 400 ° C. to 420 ° C. for 30 minutes or more (N14); Primary setting process (N14a), in which the heat-treated coil spring is brought into close contact with a hydraulic setting device: Polishing both ends of the secondary tempering coil spring 100 (N15); Short-pinning the polished coil spring 100 (N16); Secondary set-up process (N16a) to keep the free-end tolerance of shot-pinned coil springs constant so as not to shrink: Tempering the short-pinned coil spring 100 at 200 ° C. to 230 ° C. for at least 10 minutes to remove stress (N17); The method of manufacturing a coil spring, characterized in that consisting of a process (N18) to coat the inner and outer sides of the low-temperature tempered coil spring (100).