JPS6127133A - Warm forming method of coil spring - Google Patents

Abstract

PURPOSE:To form a large diameter and high strength coil spring by heating quickly a wire rod up to a prescribed temperature area immediately before passing through a bending stress working point, and subsequently, deflecting and forming it in a shape of a coil. CONSTITUTION:A wire rod 1 of a large diameter and a high strength passes through a wire rod path 31 of a wire guard 3 by a thrust P of a feed roller group 2 and advances in the direction of a coiling roller 4. An induction heating coil 6 is provided in a space in front of a bending stress working point F in case the wire rod 1 is worked plastically, and its outside periphery is covered with an insulating magnetic material 7. The wire rod 1 passing through the roller group 2 in a room temperature state is heated quickly to a prescribed temperature area of a tempering temperature or below, etc. in the heating coil 6, and thereafter, collides and contacts with the roller 4 and it is formed to a coil. According to this method, a plastic deformation resistance of the time of forming the coil becomes small, and a coil spring of a large diameter and a high strength can be formed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for warm forming coil springs, particularly large-diameter high-strength coil springs, which are frequently used in various mechanical devices.

(Prior art) When manufacturing springs, coil springs made of thin wire rods with a wire diameter of 8 to 9 mm or less are usually made by drawing or heat treating the raw wire rods to a predetermined strength, and then cold forming them into coil springs. Coil springs made of large-diameter wire rods with a wire diameter of 19 mm or more are difficult to form, so the wire rods are hot-formed into a coil spring shape and then heat-treated to give a predetermined strength.

However, in recent years, coil springs made of the above-mentioned large-diameter wire rods have also been developed, for example, in Japanese Patent Publication No. 59-1356 according to the invention filed by the present applicant.
As disclosed in No. 8, by subjecting the raw material wire to a predetermined heat treatment, a spring wire material with a tensile strength of 150 Kgf/mn (or more) and extremely good cold formability has been developed. It has also become possible to cold form high-strength wire rods.

On the other hand, Japanese Patent Publication No. 59-1999, which is also related to the invention filed by the present applicant,
As disclosed in No. 1'0975, tensile strength 150Kgf
/mrJ or more, wire rods such as oil-tempered wires for springs are continuously heated to 300 to 600 by rapid heating such as high-frequency induction heating.
“A method for manufacturing a coil spring has also been developed, which allows coil springs to be easily formed while maintaining the mechanical properties required for a spring material by heating the coil to an appropriate temperature of C. By the way, in the embodiment shown in the above-mentioned Japanese Patent Publication No. 59-10975, as shown in FIG. Before being fed to the coil spring forming mechanism (■) consisting of a guide 3 and guide rollers or guide pins 4, it passes through a warm heating device (II) equipped with, for example, a high frequency induction heating coil 6. The feed roller group 2 and the wire guide 3, through which the wire heated to the warm temperature range passes, must be made of heat-resistant material, and in order to bend the large-diameter high-strength wire, the wire 1 must be subjected to a strong thrust. If you set the reduction blade of feed roller 2 to large because it is necessary to feed the material with
There is a risk that problems such as a decrease in the roundness of the wire rod, which has decreased plastic deformation resistance, may occur. In addition, what is shown as 5 is a wire straightening roller.

(Object of the Invention) The present invention was made with the aim of solving the problems existing in the above-mentioned conventional methods, and provides a coil spring warm forming method that enables forming a large-diameter high-strength wire rod without heating the feed roller group. This is what we provide.

(Structure of the Invention) The structure of the present invention is as follows: (1) Continuously supplied large-diameter high-strength spring wire is fed into a forming mechanism consisting of a feed roller, a wire guide, and a coiling pin or coiling roller to form a coil into a predetermined shape. In the case of forming into a spring, (2) the wire rod is heated to a warm region by a rapid heating means provided on the feed line immediately before passing through the point of bending stress applied during forming on the wire guide; A method for warm forming a coil spring, characterized in that the wire heated in the intermediate region is deflected in the traveling direction by the coiling pin or the coiling roller to form a coil shape.

(Example) The present invention will be described in detail below according to the example shown in FIGS. 1(a) and 1(b).

FIGS. 1(a) and 1(b) are a front view and a sectional view taken along the line A-A of the present invention, respectively, showing the forming mechanism (I).
) The wire rod 1 is given a thrust P by the rotational force of the feed roller group 2 in the direction of the arrow, passes through the wire rod passage 31 provided in the wire guide 3, and then passes through the coiling roller 4.
, moving in four directions. Wire passage 31 of the wire guide 3
At a position shown as point F near the exit of the coiling rollers 4, there is a bending stress application point that occurs in the wire when the wire is plastically worked by deflecting its running direction by the coiling rollers 4, 4. A space 32 of a predetermined shape including a wire passage 31 is provided behind the stress application point F in the wire feeding direction, and an induction heating coil 6 whose winding inner diameter is larger than the wire diameter by a predetermined value is inserted into the space through the wire passage. A rapid "heating means" is provided which is arranged concentrically with 31 and whose outer periphery is constructed so as to fill the space 31 with an insulating magnetic material 7.The induction heating coil 6 is connected to a predetermined frequency and output power source E. The wire is connected to the induction heating coil 6 at a predetermined feed rate and is set to be able to be inductively heated to a predetermined warm region. The above-mentioned warm region must be at a temperature that does not reduce the strength of the wire, and if the wire is a hardened and tempered wire, the temperature is below the tempering temperature.
For example, it must be in the range of 300 to 600°C. The insulating magnetic body 7 is made of, for example, a ferrite core,
It is provided to converge the magnetic flux generated from the induction heating coil 6 to increase heating efficiency, and to prevent the wire guide 3 itself and its surroundings from being heated.

(Operation of the invention) By setting as described above, the feed roller group 2
The wire rod fed with a stronger thrust P is at room temperature when it passes through the feeding roller group 2, and there is no decrease in plastic deformation resistance.On the other hand, during coiling, the bending stress application point F is on the wire guide 30 and the wire rod passage 31. Since the guide roller 4 is heated to a warm region by the heating means provided immediately before the guide roller 4, the plastic deformation resistance is reduced.
The force acting on the bending stress application point F when it collides with 4 and deflects its traveling direction also becomes small.

(Experimental Example) The inventor conducted the following experiment to confirm the effects of the present invention.

◎ Experimental Method The specimens shown below were molded into coil springs according to the conditions described below, and the temperature rise state of the wire guide 3 during molding was observed and the performance of the formed coil springs was tested.

Specimen: Wire material: 3iCr steel wire Diameter: φ14mm Strength: 1,80 to 195Kgf/mm (quenched/
Tempered wire forming machine specifications: Torque: 60 Kgm Feed speed: 28 m/min High frequency power: Frequency: 100'KHz Output: -150 Kw Heating temperature: 350 to 370°C Coil spring shape: Winding diameter: φ84 mm Number of turns: 8 N 440 mm ◎ Wire Guide Observation Almost no temperature increase was observed in the vicinity of the wire guide 3 where the induction heating coil 6 was provided, and a temperature increase of approximately 300°C was observed in the front of the wire guide 3 in the feeding direction, that is, near the exit.

◎Settling resistance test The constant strain tightening test was conducted under the conditions of shear stress of 115Kg f /mrd (including correction coefficient) for 2 hours and 100hr, and the same specimen wire was made into a coil spring of the same shape by cold forming. The results were compared with those of the same test.

Permanent deformation of the specimen of the present invention---2, OX 10-'Permanent deformation of the cold-formed specimen-2,8 Since the wire guide 3 is covered with an insulating magnetic material 7, the wire guide 3 is not heated, and the rapid heating means operates only when the wire is running, so the temperature rise near the outlet is also compared. It was confirmed that the coil spring could be pressed as low as possible, and the molded coil spring was
Similar to the technique disclosed in No. 975, it was confirmed that the coil spring had better performance than the coil spring produced by cold plastic working.

(Effects of the Invention) By carrying out the present invention, (1) large-diameter, high-strength spring wire rods can be formed into coils with guaranteed roundness, and (2) since they are warm-formed, 1. There is no decrease in strength, no scale is present in the wire, and there is no risk of decarburization. 9. There is no change in surface roughness, and hot stretching As well as the effects of the above-mentioned JP 59-1, creep resistance and fatigue resistance are improved.
Of course, the effect equivalent to or greater than the effect of the invention shown in No. 0975 can be obtained, (3) the roller group for feeding the wire does not need to be made of heat-resistant material, and (4) the wire guide is made of induction heating. Despite containing a coil, there is almost no leakage magnetic flux, and only the tip of the wire guide in front of the bending stress application point comes into contact with the wire heated to a predetermined warm temperature range. The force acting on the bending stress application point is lowered due to the lower elastic limit of the wire rod, so the wire guide is less prone to guide flaws, so there is no wear and tear, and the service life is extended. The effect of the seal is enormous.

[Brief explanation of the drawing]

FIG. 1(a) is a partially sectional front view of an embodiment of the method for warm forming a coil spring of the present invention, and FIG. 1(b) is a partial front view of FIG. 1(a).
FIG. 2 is a partially sectional front view showing the conventional method. 1--m--Wire rod for large diameter high-strength spring 2--Feeding roller' 3--Wire guide 31-Wire feeding passage 32-Space 4--Coiling pin, coiling roller 6-- -1 Rapid heating means, induction heating coil 7----1 Insulating magnetic material F---1--Bending stress application point (III)-m-Forming mechanism

Claims (1)

[Claims] 1) In the case where continuously supplied large-diameter high-strength spring wire is fed into a forming mechanism consisting of a feeding roller, a wire guide, and a coiling pin or coiling roller to form a coiled spring of a predetermined shape. , the wire rod is heated to a warm region by a rapid heating means provided on the feed line immediately before passing through the bending stress application point during forming on the wire guide, and the wire rod heated to the warm region is coiled. A method for warm forming a coil spring, characterized by deflecting the running direction using a pin or a coiling roller to form a coil spring. 2) The method for warm forming a coil spring according to claim 1, wherein the warm region is a temperature region that does not reduce the strength of the wire rod. 3) The method for warm forming a coil spring according to claim 1, wherein the warm region is below the tempering temperature when the wire is a quenched/tempered heat-treated material. 4) The rapid heating means is provided in a space of a predetermined shape provided on the rear side in the wire rod feeding direction of the bending stress application point on the wire rod feeding path in the wire guide, the periphery of which is covered with an insulating magnetic material, and is concentric with the wire rod feeding path. 2. The method of warm forming a coil spring according to claim 1, wherein the coil spring is an induction heating coil arranged in a shape. 5) The method for warm forming a coil spring according to claim 1, wherein the rapid heating means operates only when the wire is running.