JPS6351779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a tapered bar for a coil spring.

Tapered bars for coil springs are generally required to have a perfect circular cross-sectional shape, a desired taper, and high dimensional accuracy. However, the method of applying tensile deformation by applying a temperature gradient to the material, such as conventional dieless drawing, has poor dimensional accuracy and tends to cause netting, so there is a limit to the molding dimensions. In addition, in normal roll rolling, the cross-sectional shape becomes a polygonal shape with curved sides, which increases stress and inferior fatigue properties compared to a perfect circle with the same torsional rigidity, and depending on the material diameter, roll replacement may be required. The preparation process is complicated, and it is difficult to continuously taper the cross-sectional shape axially with high accuracy.

The present invention has been made under the above circumstances, and an object thereof is to provide a method for manufacturing a tapered bar for a coil spring, in which the dimensional accuracy of the molded product is high and the preparation process is simple.

Hereinafter, the present invention will be explained with reference to the drawings. In the rough forming step shown in FIG. 1, a first stand 1, a second stand 2, and a drawer chuck 3 for moving the material a in the forward direction of these stands 1 and 2 are provided. The first stand 1 is equipped with four flat rolls 4 arranged at angles of 90 degrees around the movement path of the material a.
These rolls 4 are supported so as to be rotatable around respective rotational axes arranged on a plane perpendicular to the moving direction of the material a, and to be able to move toward and away from the material a. The second stand 2 has substantially the same structure as the first stand, except that the four flat rolls 5 have a phase difference of 45 degrees from the flat rolls 4 in the first stand. and,
The amount of reduction of each of the rolls 4 and 5 is controlled according to the amount of movement of the material a, and the amount of movement is controlled, for example, by a pulse generator (not shown) connected to the roller 6 that rolls into contact with the material a. detected.

Therefore, in the rough forming step, the round bar-shaped material a, which has been heated to a predetermined temperature in advance as necessary, is
When the rollers 4 and 5 are moved in the longitudinal direction via the chuck 3, the rolls 4 and 5 are rolled down in accordance with the amount of movement, and are driven to rotate by coming into pressure contact with the material a. The material a is rolled in the first stand 1 so that the cross-sectional shape gradually approaches a square as shown in FIG. 2, and in the second stand 2 the cross-sectional shape becomes closer to a square as shown in FIG. is gradually rolled so that it approaches a regular octagon. In this way, a tapered intermediate material b having a round bar shape at its base end and a regular octagonal shape at its distal end is formed. In this case, the inscribed circle diameter d ₁ and circumscribed circle diameter d ₂ of the cross section at each position in the longitudinal direction of the material b are both within the tolerance of +0.70 and -0.05 mm with respect to the desired true circle diameter d ₀ at that position. is formed. As an example, as a result of rolling a round bar material a with an outer diameter of 12 mm with a target diameter of 9 mm at the small diameter part, d ₁ and
At the tip where the deviation from d ₂ is maximum, d ₁ = 9.0,
d ₂ =9.6.

Next, in the finishing forming step shown in FIG. 4, a roll housing 7 that is rotationally driven around the movement path of the intermediate material b and a drawer chuck 8 for moving the intermediate material b in the longitudinal direction are provided. ing. There are three roll housings 7 arranged around the intermediate material b at an angle of 120 degrees (two are shown in the figure).
It is equipped with cylindrical rolls 9, and these rolls 9 are supported so as to be rotatable about a rotation axis substantially parallel to the direction of movement of the intermediate material b, and to be able to move toward and away from the intermediate material b. Further, the chuck 8 is constructed so as not to allow rotation of the intermediate material b. The amount of rolling of the rolls 9 is controlled according to the amount of movement of the intermediate material b, and the amount of movement is
For example, it is detected by a pulse generator (not shown) connected to the roller 10 that rolls into contact with the intermediate material b. FIG. 5 and FIG. 6 are examples of stands for finishing molding. In this case, the three-jaw scroll chuck of the lathe is modified, and the roll 9 is attached to the tip of the chuck.
An experiment was conducted with the feed speed of material B at 200 mm/min and the rotation speed of the scroll chuck at 150 rpm. The rolling down control of each roll 9 is performed by rotating a surface plate having a spiral groove, for example, to move the claws in the radial direction of the material b in synchronization with each other.
In the case of the four-roll taper processing method as illustrated in FIG. 7, the amount of reduction of the rolls 9 may be changed by rotating the eccentric die 12. A rotary encoder or Magnescale is used to measure the amount of product pulled out.

Roll 9 having the shape shown in FIGS. 8 and 9
is used under conditions where the roll axis inclination angle is zero and the feed angle θ is 30° or less, but when the roll axis inclination angle φ (0≦
φ≦60°).

Therefore, in the above finishing forming process, when the intermediate material b is moved in the longitudinal direction via the chuck 8 and the roll housing 7 is rotationally driven, the rolls 9 are rolled down according to the amount of movement of the intermediate material b. It is rotationally driven by being in pressure contact with the material b. As a result, the intermediate material b is rolled into a tapered shape with a circular cross section, and the desired product c is formed.

When this finishing forming process was applied to the above example, when a roll with a diameter of 40 mm was used, the deviation from the desired perfect circular diameter d ₀ at each position in the longitudinal direction was all ±0.1 mm or less. FIG. 11 shows the results of measuring the dimensions and shape of the tapered portion in the longitudinal direction, and it was confirmed that the accuracy of the tapered shape in the longitudinal direction was also improved by performing the finishing forming step.

In the above, a case has been described in which roll rolling is applied to the rough forming process, but instead of this, the material a may be subjected to tension forming with a temperature gradient, such as dieless drawing. Further, even when rolling with rolls, the number of rolls generally needs to be two or more, and the number of stages can be set arbitrarily. Furthermore, in the final forming process, the number of rolls may be any number as long as it is two or more, and the rotational axis of the roll 9 has an inclination angle with respect to the moving direction of the intermediate material b.
It is sufficient that the feed angle is 60 degrees or less and the feed angle is 30 degrees or less, and they do not necessarily need to be parallel. Further, the intermediate material b and the roll housing 7 only need to rotate relative to each other, and at least one of them needs to rotate, and if necessary, the roll 9 may be rotationally driven. In addition, various modifications and applications are possible within the scope of the gist of the present invention.

As described above, the present invention includes a rough forming step of forming a rod-shaped material into a tapered intermediate material, and rolling of these rolls while rotating a plurality of rolls in the circumferential direction of the intermediate material while moving the intermediate material in the longitudinal direction. The process includes a finishing step of rolling and forming a tapered bar having a circular cross section while moving these rolls in a spiral manner relative to the intermediate material by changing the amount of movement in the longitudinal direction of the intermediate material. According to the method of the present invention, an extremely smooth and good surface texture can be obtained after rolling, and dimensional accuracy such as slope and roundness can be greatly improved. It can greatly contribute to improving the quality level of things that are used dynamically. Furthermore, as described above, the finishing allowance is small, so the forming load is small, the rigidity of the device can be set low, precise rolling control is facilitated, and consideration for wear and the like is reduced. Furthermore, since the rolling rolls may be flat rolls, there is less need for roll replacement based on differences in material diameter, and the preparation process is simple, and recycling grinding is easy. Also,
When a means for applying tensile deformation by applying a temperature gradient to the rough forming process is used, the final finishing accuracy can be made sufficiently good even when the forming area reduction rate is set to a large value and netting occurs.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the rough forming process of the present invention, Figs. 2 and 3 are sectional views taken along lines - and -, respectively, in Fig. 1, and Fig. 4 is an explanatory diagram of the final forming process of the present invention. , FIG. 5 is a side view showing one embodiment of the finishing stand, FIG. 6 is a front view of the stand shown in FIG. 5, and FIG. 7 is a schematic front view showing another embodiment of the finishing stand. , Fig. 8 is a side view showing an example of the roll, Fig. 9 is a plan view of the roll shown in Fig. 8, Fig. 10 is a side view showing a modified example of the roll, and Fig. 11 shows the intermediate material and finished product. It is a figure which shows the dimension shape of the longitudinal direction. 1...First stand, 2...Second stand, 3,8
...Drawer chuck, 4, 5, 9...Roll, 7...Roll housing, a...Material, b...Intermediate material, c...
Finished product.

Claims (1)

[Claims] 1. When forming a rod-shaped material into a tapered bar with a circular cross section, the material is rolled by a plurality of rolls while moving in the longitudinal direction, or by drawing the material with a temperature gradient as in dieless drawing. A rough forming process of forming a tapered intermediate material, and a plurality of rolls rotating in the circumferential direction of the intermediate material while moving the intermediate material in the longitudinal direction, and the amount of rolling of these rolls is adjusted according to the amount of longitudinal movement of the intermediate material. A method for manufacturing a tapered bar for a coil spring, comprising a final forming step of rolling and forming a tapered bar having a circular cross section while moving these rolls in a spiral manner relative to an intermediate material by changing the shape of the material.