Spring forming device and forming method therefor

Abstract

A spring forming device in which the steel wire can be continuously cut off without stopping the feeding of the steel wire in cutting, and in which the steel wire can be uniformly heated, is provided. The spring forming device has a wire supplying mechanism for supplying a steel wire using a plurality of feeding rollers, a heating mechanism for heating the steel wire, a coiling mechanism for forming in a coil state the heated steel wire, and a cutting mechanism for cutting the steel wire coiled at a given number of turns off the steel wire remained backward. A cutting blade of the cutting mechanism follows tracks having a speed Va that moves to the receiving blade and a speed Vc that moves in an axial direction of the coiled steel wire, in cutting of the steel wire.

Claims

1. A method for forming spring, comprising a heating step for heating a steel wire while feeding the steel wire, a coiling step for coiling the heated steel wire in a coiled shape, and a cutting step for cutting the steel wire coiled at a given number of turns off the steel wire remained backward, wherein the cutting step is carried out by a receiving blade and a cutting blade which closes and separates to the receiving blade, and the cutting blade follows tracks, has a speed Va that moves to the receiving blade and has a speed Vc that moves in an axial direction of the coiled steel wire, in cutting of the coiled steel wire, and wherein when the steel wire is cut off by the cutting blade, a feeding speed Vw of the steel wire and the speed Vc of the cutting blade are controlled satisfying the relationship Vc/Vw1.1.

2. The method for forming the spring according to claim 1, wherein roundness of coil diameters at a coiling start side terminal of a coiled spring is set to be substantially 1.0.

3. The method for forming the spring according to claim 1, wherein the steel wire is heated to an austenite range for 2.5 seconds or less.

4. The method for forming the spring according to claim 1, wherein both ends of the coiled steel wire are provided with a grain size number of 10.5 or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a side view showing a coiling machine in an embodiment of the present invention.

(2) FIG. 2 is a side view showing a coiling mechanism in an embodiment of the present invention.

(3) FIG. 3 is a perspective view showing a coiling mechanism in an embodiment of the present invention.

(4) FIG. 4 is a side view showing tracks of a cutting blade in an embodiment of the present invention.

EXPLANATION OF REFERENCE NUMERALS

(5) Reference numeral 10 denotes a wire supplying mechanism, 11 denotes a feeding roller, 20 denotes a heating mechanism, 21 denotes a high frequency heating coil, 30 denotes a coiling mechanism, 31 denotes a wire guide, 32 denotes a coiling tool, 33 denotes a pitching tool, 40 denotes a cutting mechanism, 41 denotes a cutting blade, 42 denotes a receiving blade, and W denotes a steel wire.

MODE FOR CARRYING OUT THE INVENTION

(6) In the following, embodiments of the present invention will be explained with reference to FIGS. 1 to 4. Reference numeral 10 in FIG. 1 denotes a wire supplying mechanism. The wire supplying mechanism 10 has a plurality of feeding rollers 11 which are continuously provided in a horizontal direction. Wire guides 12 for guiding a steel wire W are arranged between the feeding rollers 11.

(7) A heating mechanism 20 is arranged at a downstream side of the wire feeding mechanism 10. The heating mechanism 20 has a spiral high frequency heating coil 21 coaxially placed to the steel wire W. The steel wire W is heated to an austenite range for 2.5 seconds or less by the high frequency heating coil 21. Here, the high frequency heating coil 21 is not limited to a spiral coil shown in FIG. 1, and it may use coils in a suitable shape for heating performance and setup performance, such as a coil in a channel shape in which a side in an axial cross section is opened, etc.

(8) A coiling mechanism 30 is arranged at a downstream side of the heating mechanism 20. Reference numeral 31 in the figures denotes a wire guide, and the wire guide 31 induces the steel wire W supplied by the feeding rollers 11 to an appropriate position in the coiling mechanism 30. A coiling tool 32 consisting of two coiling pins (or coiling rollers) and a pitching tool 33 for forming pitches are arranged at a downstream side of the wire guide 31. The steel wire W that passed through the wire guide 31 is bent at a given curvature by contacting with a first coiling tool 32, and furthermore, it is bent at a given curvature by contacting with a next coiling tool 32 at a downstream side. Then, pitches are formed to the steel wire W by contacting with the pitching tool 33, so as to form a desired coiled shape. Here, the coiling tool 32 may also be an aspect having one coiling pin (or coiling roller).

(9) Reference numeral 40 in the figures denotes a cutting mechanism. The cutting mechanism 40 has a cutting blade 41 which can be vertically moved by a crank mechanism (not shown). The cutting blade 41 can be horizontally moved by a moving mechanism (not shown). In this manner, when the cutting blade 41 moves downward as shown in FIG. 4A, it moves at a speed Va which moves downward and a speed Vc which moves in a horizontal direction (a left direction in the figure), and an edge 41a of the cutting blade 41 is inserted obliquely downward into the steel wire W, so that it follows tracks of a straight line. The speed Vc is set to be faster than a speed Vw at which the steel wire W is fed in cutting.

(10) A receiving blade 42 is arranged downward of the cutting blade 41. The receiving blade 42 functions as a lower blade, and it is supported in a cantilever state in the cutting mechanism 40, as shown in FIG. 3. The cutting blade 41 moves downward when the steel wire W is bent by the coiling tool 32 until a number of turns is attained at a given value, and the coiled steel wire W is cut off a steel wire W supplied from a rear side by shearing between the cutting blade 41 and a straight portion of the receiving blade 42. Here, after the steel wire W is cut by the cutting blade 41, as shown in FIG. 4A, interference with the steel wire W is avoided by moving the cutting blade 41 at almost right angles to a moving direction thereof.

(11) In the spring forming device having the above structure, the cutting blade 41 follows tracks having a speed Va that moves downward and a speed Vc that moves in a horizontal direction, in cutting of the steel wire W, and the steel wire W is fed at a speed Vw without stopping the moving. Therefore, non-uniformity of heating time of the steel wire W by the heating mechanism 20 is avoided, and heating temperature of the steel wire W is made further uniform. In the case in which the speed Vw in cutting is closer to the feeding speed when the steel wire W is heated and coiled while feeding, the non-uniformity of the heating time of the steel wire W is further avoided.

(12) In particular, in the above embodiment, the cutting blade 41 moves at speed Va, which moves downward, and the speed Vc, which moves in a horizontal direction; however, the feeding speed Vw in an axial direction in the cutting of the steel wire W is smaller than the speed Vc. Therefore, the cutting blade 41 moves in a feeding direction at a faster speed than that of a cut surface of the steel wire W, and as a result, deformation of the cut surface is prevented without pressing the cut surface of the steel wire W by a flank 41b of the cutting blade 41, and the roundness of the coil diameter is improved.

(13) Here, in the above embodiment, the cutting blade 41 is moved linearly and obliquely downward; however, the cutting blade 41 is not limited in this manner, and it may carry out optional motion. For example, the cutting blade 41 may carry out an oval motion as shown in FIG. 4B. Alternatively, it may carry out a rotary motion as shown in FIG. 4C. Such motion of the cutting blade 41 is realized by guiding the cutting blade 41 in a reciprocating motion between a top dead center and a bottom dead center.

EXAMPLES

(14) Next, examples of the present invention will be explained by verifying numerical limitations in preferable aspects thereof. Spring forming devices and forming conditions of springs in Examples are shown below. Length of a heating coil: 170 mm Space distance between a feeding roller and a receiving blade: 400 mm Oscillating frequency of a high frequency heating coil: 200 kHz Feeding speed of a steel wire in coil forming: 40 to 50 m/min Feeding speed of a steel wire in coil cutting: 8 to 50 m/min Speed Vc in a vertical direction of a cutting blade: 40 to 120 m/min Diameter of a steel wire: 2 to 5 mm Heating temperature: 900 degrees centigrade Average diameter of coils per diameter of a steel wire: 6.0 Number of turns: 5.75

Example 1

(15) Crystal grain sizes and coil outer diameters of coiled springs which were produced while feeding speed in cutting off of steel wire was changed from 8 to 50 m/min, are shown in Table 1. In the Examples of the present invention, in the case in which feeding speed (a) in cutting off of steel wire was the same as feeding speed (b) in forming of steel wire, and in the case in which feeding speed (a) in cutting off of steel wire was 90% of feeding speed (b) in forming of steel wire, there was no difference between crystal grain size at both edge portions of a coil and crystal grain size at an effective portion of the coil, and grain size number thereof was 12.2. In addition, coil outer diameters at the both edge portions and the effective portion of the coil were the same. Furthermore, in the case in which feeding speed (a) in cutting off of steel wire was 50% of feeding speed (b) in forming of steel wire, the grain size number was 10.5 and was sufficient, and a difference of coil outer diameters between both edge portions and the effective portion of the coil was in an allowable range. Therefore, it was confirmed that feeding speed in cutting off of the steel wire was preferably 50 to 100% of the feeding speed in coiling of the steel wire, and that it was more preferably 90 to 100% thereof.

(16) TABLE-US-00001 TABLE 1 Crystal grain Coil outer Feeding speed of wire size (G) diameter (mm) Wire a in Both Both diameter cutting b in a/b edge Effective edge Effective Nos. (mm) off forming (%) portions portion portions portion Note Examples 1 4 40 40 100 12.2 12.2 28.7 28.7 2 4 36 40 90 12.2 12.2 28.7 28.7 3 4 32 40 80 11.8 12.2 28.6 28.7 4 4 28 40 70 11.5 12.3 28.6 28.7 5 4 20 40 50 10.5 12.1 28.5 28.7 6 4 50 50 100 12.2 12.2 28.7 28.7 Comparative 7 4 16 40 40 9.9 12.2 28.3 28.7 Examples 8 4 8 40 20 not coiling (buckling)

(17) In contrast, in Comparative Examples in which the feeding speed (a) in cutting off of the steel wire was not more than 50% of the feeding speed (b) in forming of the steel wire, a difference of heating temperature between the both edge portions and the effective portion of the steel coil was increased, and the both edge portions were excessively heated. As a result, crystal grains were coarsened, and grain size number was 10 or less. Additionally, a difference of the coil outer diameter was 0.4 mm or more, and required qualities were not satisfied. In particular, in Comparative Example in which the feeding speed (a) in cutting off of the steel wire was not more than 20% of the feeding speed (b) in forming of the steel wire, buckling occurred, and therefore, coiling could not be carried out.

Example 2

(18) Roundness of coil diameters at a coiling start side terminal of coiled springs, produced while Vc/Vw was changed from 1.00 to 3.00, is shown in Table 2.

(19) TABLE-US-00002 TABLE 2 Wire diameter Vc Vw Vc/ Roundness Nos. (mm) (m/min) (m/min) Vw (mm) Note Examples 1 4 44 40 1.10 1.000 2 4 50 40 1.25 1.000 3 4 70 40 1.75 1.000 4 4 100 40 2.50 1.000 5 2 50 40 1.25 1.000 6 5 50 40 1.25 1.000 7 4 75 50 1.50 1.000 8 4 120 40 3.00 1.000 Over specification 9 4 42 40 1.05 0.995 Terminal deformation Comparative 10 4 40 40 1.00 Not coiling Example (buckling)

(20) In Examples 1 to 9 in which Vc/Vw was 1.05 to 2.50, in the case in which the steel wire diameter was 2 to 5 mm (in the present invention, it was a diameter in the case in which roundness was calculated from a cross sectional area of the steel wire, and it contained the case in which a circle equivalent diameter including a non-circular cross section such as a rectangle, an ellipse, etc., was 2 to 5 mm), the coiling could be carried out when the roundness was 0.995 to 1.000. In particular, in Examples 1 to 8 in which Vc/Vw was 1.10 to 2.50, the roundness was 1.000, there was no terminal deformation at all, and the coiling could be carried out.

(21) Steel wires having a diameter of 1.5 to 9 mm except for samples shown in Table 2, could be hot-coiled. That is, when the steel wire diameter was not more than 1.5 mm, the strength as a steel wire was low, and as a result, the steel wire could often not be coiled due to deformation or buckling in coiling, etc. Therefore, in order to improve yield rate, it is preferable that the steel wire diameter be 1.5 mm or more. However, in order to further improve the yield rate by more surely preventing the deformation or the buckling in coiling, it is desirable that the steel wire diameter be 2 mm or more.

(22) In contrast, when the steel wire diameter exceeded 9 mm, incomplete hardening portions remained from the vicinity of a surface of the steel wire having high load stress to the inside of the steel wire. Therefore, it was desirable that the steel wire diameter be 9 mm or less. When the steel wire diameter exceeded 5 mm and was 9 mm or less, the incomplete hardening portions remained from the vicinity of the center of the steel wire. However, there was no problem in using the steel wire as a coiled spring, since the load stress was low in the vicinity of the center of the steel wire. Furthermore, in order to form a spring having a homogeneous structure over the whole area to the inside of the steel wire, it was more desirable that the steel wire diameter was 5 mm or less.

(23) In Comparative Example 10 in which Vc/Vw was 1.00, the steel wire was buckled, and the coiling could not be carried out. In Example 8 in which Vc/Vw was 3.00, the roundness was the same as those of Examples 1 to 7; however, it was uneconomical since equipment for increasing Vc was over specification. That is, in Example 8, it was necessary to have a high-performance motor in which a cutting blade was driven, and as a result, it was uneconomical. Therefore, it was desirable that Vc/Vw exceed 1.00 and be 2.50 or less, as in those of Examples 1 to 7 and 9, and in order to form a coiled spring having high accuracy (roundness), it was more desirable that it be 1.10 to 2.50 as in those of Examples 1 to 7.