JPS5855372B2 - Method for forming a covering part of a coil spring for a vehicle suspension system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a covering portion of a coil spring.6 In a coil spring used in an automobile suspension system, adjacent spring wires collide with each other due to vibrations, shocks, etc. that occur during running. This produces a so-called tapping sound.

In particular, in products with non-linear characteristics such as tapered coil springs and unequal pitch coil springs, the spring wires are intercepted so that they collide with each other at a portion in the longitudinal direction, which can cause knocking noise. Remarkable.

In order to prevent the occurrence of such knocking noise, a tube with a spring wire inserted into it is used, but water or electrolytic solution (such as road surface antifreeze) that enters the tube can be used. In some cases, spring wires may break due to corrosion or corrosion fatigue, and even if adhesives or sealants are used to prevent moisture from entering, they may not be sufficiently effective under conditions of repeated stress. I can't wait.

Furthermore, inserting the spring wire into the tube requires a large number of man-hours both manually and mechanically, making it extremely difficult to improve productivity.

Furthermore, in the case of using a tube provided with slits, productivity is slightly improved, but there is a disadvantage that the adverse effects of moisture are more significant than in the former case.

Furthermore, methods such as immersion in a highly concentrated resin solution or coating with powder may be considered, but in order to obtain a thickness that is effective in preventing the occurrence of tapping noise, it is necessary to repeat the treatment at least several times. Not only is this necessary, and there is a risk of air pollution, but masking is also required in the case of partial painting.

Further, as seen in Japanese Utility Model Publication No. 10408/1983, a resin coating is applied to the wire before coiling.

However, for coil springs for vehicle suspension systems that require hot forming and are heat treated at a high temperature of 800°C or higher as specified in JIS G 4801, If a resin is attached to the molding surface as in No. 10408, the resin will burn during coiling or heat treatment, making it completely useless.

The present invention has been made in view of the above circumstances, and its purpose is to facilitate the formation of a covering portion on a spring wire and to increase productivity, and to ensure that the covering portion is firmly attached to the spring wire. To provide a method for forming a sheathing part of a coil spring that does not easily come off due to the windings, effectively prevents tapping noise and corrosion of spring wires, and does not adversely affect the characteristics of the coil spring body. be.

Hereinafter, the present invention will be explained with reference to the drawings.

In FIG. 1, a main body 1 of a coil spring is formed by winding a spring wire 2 into a coil shape.

The spring wire 2 is provided with a covering portion 3 that covers the entire spring wire including at least a portion of the portion facing adjacent spring wires or the mutually opposing surfaces thereof.

The formation of this covering portion 3 is performed when the surface temperature of the spring wire 2 is 100%.
The main body 1 is preheated to about ~250°C, and a thermoplastic resin powder with a melting point of 250°C or less is injected from a spray gun along with fire, and the desired amount is sprayed onto the desired position of the spring cable chain 2. This is done by fusing them together.

Note that the coil spring body 1 is subjected to a surface coating similar to that of a general coil spring in a step before forming the covering portion 3.

In this case, if the coil spring body 1 is heated and dried in a drying oven or the like after painting, for example, this drying step may be used instead of the preheating step for attaching the coating portion 3. In such a case, it is preferable to arrange an injection stage at an appropriate position on the exit side of the drying oven.

Further, it is preferable to use a single spray gun that can inject both resin powder and flame at the same time, and it is preferable to keep the temperature of the spring wire always below 250°C.

It should be noted that if the preheating temperature is less than 100°C, the adhesion efficiency of the resin powder to the spring surface will deteriorate, which is undesirable, and if it exceeds 250'C, the residual stress obtained by shot peening will drop significantly, which is not preferred.

Modified ethylene-vinyl acetate copolymer was used as the powder material, and
Spray from a distance of 50 to 1000 degrees at a spray angle of 90' (
Table 1 shows the test results of an example in which the device was manufactured by 5CHRI Co., Ltd. and a comparative example in which a spring wire was inserted into a tube.

As can be seen from the table, the above Examples have soundproofing effects equivalent to those of the Comparative Examples, and are excellent in durability and antirust effects, and in particular, productivity is significantly improved.

Further, in both cases, no change in the spring constant was observed depending on the presence or absence of the covering portion.

In addition, the soundproofing effect in the table is for amplitude O to ±25 and frequency IH.
When a rectangular wave of z was input, the sound pressure level was 80 to 85 dB without the coating, but became O with the coating.

Durability is indicated by the number of repetitions of compressive load.

The rust prevention effect is based on one salt spray test. In the comparative example, rust occurred in 72 to 120 hours, but in the example, rust occurred in 72 to 120 hours.
No rust occurred after 40 hours or more.

Productivity is indicated by the time required to form the covering part on one main body.

G and E are the tensile strength and elongation of the coating.

Table 2 shows the measurement results of residual compressive stress before and after thermal spraying in the above examples.

As can be seen from the same table, the influence of thermal spraying on residual compressive stress is substantially negligible, and it can be seen that the effect of shot peening is not lost.

Note that the residual compressive stress was measured by the X-ray method.

In the second embodiment in which modified nylon was used instead of the modified ethylene vinyl acetate copolymer in the above embodiment, the thickness of the covering portion 3 was 1 times the thickness in the first embodiment.
72, the same soundproofing effect was obtained.

In addition, in the third embodiment using polyolefin powder, the same soundproofing effect as in the first embodiment can be obtained with a thickness of 4 mm in the case of polyethylene and 1 mm in the case of ionomer resin. I was able to do that.

Note that the present invention is not limited to the above-mentioned embodiments. For example, the coil spring main body 1 may be unequal in all or part of the coil inner diameter, coil outer diameter, coil pitch, strand diameter, etc. The presence or absence of the end turn portion, the cross-sectional shape of the strands, etc. can be arbitrarily set.

The covering portion 3 may be fused to the main body 1 at one end, both ends, the middle portion, the entire length, etc. in the axial direction, and in any of these, it may be fused continuously or at intervals in the longitudinal direction of the spring wire. It may be.

Further, instead of being provided on both sides of the spring wire 2 in the coil axial direction as shown in FIG. 1, it may be provided on either side as illustrated in FIGS. 2 and 3.

If necessary, they may be provided continuously in the circumferential direction of the spring wire 2. In this case, the inner and outer portions of the main body 1 should be formed thinner than the opposing portions of the adjacent spring wires. It's okay.

In addition, when the coating portion 3 is applied only to the portions of the mutually opposing surfaces of the spring wires that are likely to come into contact with each other, the other portions are coated in the same manner as a general coil spring.

However, since this area is a surface where the spring wires do not come into contact with each other, even if a normal coating is applied, there will be no peeling due to contact, and this is sufficient to prevent rusting.

The material forming the covering portion 3 may be any thermoplastic resin powder having a melting point of 250° C. or lower.

In addition, various modifications and applications are possible within the scope of the gist of the present invention.

As described above, the spring wires of the coil spring body are preheated to a surface temperature of 100° C. to 250° C., and at least mutually Spray thermoplastic resin powder with a melting point of 250'C or less with flame from a spray gun on some or all of the points that may come into contact, or on the entire spring wire including these mutually opposing surfaces. It is characterized by being fused.

Therefore, even if the spring is hot-formed, such as a coil spring for vehicle suspension, and adjacent spring wires collide with each other due to vibrations, shocks, etc., the presence of the above-mentioned covering portion will prevent The generation of knocking noise can be effectively prevented.

In addition, since the coating is preheated to 100°C to 250°C and fused to the spring wire, the two are firmly adhered to each other to prevent moisture from entering, preventing the coating from coming off or boiling. It is possible to reliably prevent corrosion of the wires, especially at mutually contacting parts, and it is possible to exhibit the desired performance over a long period of time.

Furthermore, since powder with a melting point of 250°C or less is used and the preheating temperature is set at 100'C to 250°C, there is no adverse effect on the dimensions of the coil spring body, the spring constant, or the residual stress obtained by shot peening. There is no possibility that it will cause any adverse effects.

Moreover, when forming the coating, no pollution such as air pollution is caused, and even when applying partial coating, there is no need for a masking process, which, combined with the ease of automation and production line, greatly improves productivity. can.

Claims (1)

[Claims] 1. Pre-formed into a coil shape and heated at 100°C to 250°C
The spring strands of the coil spring body are preheated to a surface temperature of °C, including at least some or all of the mutually opposing surfaces of adjacent spring strands that may come into contact with each other, or these mutually opposing surfaces. Located throughout the spring wire, the melting point is 25
A method for forming a covering part of a coil spring for a vehicle suspension system, characterized in that thermoplastic resin powder at a temperature of 0° C. or lower is sprayed with fire from a spray gun and fused. 2. Formation of a covering portion of a coil spring for a vehicle suspension system according to claim 1, wherein the preheating is performed using the heat of a drying oven used in a heating drying step after coating the coil spring. Method.