JPS5855373B2 - 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 are exposed to mutual impact due to vibrations, shocks, etc. that occur during running. When they come into contact with each other, a so-called tapping sound is generated.

In particular, in products with non-linear characteristics such as tapered coil springs and unequal pitch coil springs, the spring wires are configured so that they collide with each other in a portion of the longitudinal direction, so the generation of knocking noise is noticeable. It is.

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 (e.g. road antifreeze), etc. that enter the tube are used. Depending on the situation, the spring wire 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 where repeated stress is applied. I can't expect that.

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, in the case of fluidized dip powder coating, the spring body should be
It is not possible to apply a thick coating without preheating to a temperature above ℃, and it is impossible to apply a thick coating of more than one layer in one coat using fluidized dip powder coating or coating by dipping in a highly concentrated resin solution. A masking process is essential for partial painting.

Furthermore, as seen in Japanese Utility Model Publication No. 10408/1983, there is also a method in which a resin coating is applied to the wire before coiling.

However, for coil springs for vehicle suspension systems that need to be hot-formed and are heat-treated at a high temperature of 800°C or higher as specified in JIS G4801, the above-mentioned Utility Model Publication No. 10408/1983 is applicable. If resin is attached before molding, as in the case of molding, the resin will burn during coiling or heat treatment, rendering it completely useless.

The present invention has been made under the above circumstances, and its purpose is to facilitate the formation of a coating on the spring wire with high productivity, and to ensure that the coating firmly adheres to the spring wire. To provide a method for forming a sheathing part of a coil spring that does not easily separate from the coil spring, effectively prevents tapping noise and corrosion of the spring wire, and does not adversely affect the characteristics of the coil spring body. .

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

In FIG. 1, the main body 1 of the coil spring includes a spring wire 2 wound into a coil.

This spring wire 2 is provided with a covering portion 3 located on a portion of the portion facing the adjacent spring wires or over the entire spring wire including the mutually opposing surfaces.

This covering part 3 is made by spraying a desired amount of synthetic resin powder with an electrostatic spray gun onto a desired position of the spring wire 2 that has been preheated to 100 to 150°C, and then depositing the powder at a temperature of about 200°C for a predetermined period of time. It is formed by fusing and bonding by heating.

The coil spring main 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.

When a coating drying step is included, it is preferable to provide a subsequent electrostatic spraying step and to perform the preheating using the heat in the coating drying step.

Further, in order to facilitate the identification of the coil spatter, the powder may be subjected to an appropriate treatment in advance so as to develop a desired color after being fused.

Note that if the preheating temperature is less than 100°C, the adhesion efficiency of the resin powder to the surface of the spring will deteriorate, so it is not preferable.
Furthermore, if the melting point of the resin powder exceeds 250° C., the residual stress obtained by shot peening will decrease significantly due to the heat required for melting, which is not preferable.

It has also been confirmed that if an electrostatic spray gun is also used, a sufficient amount of coating can be obtained even at a relatively low preheating temperature of 150'C or less.

An example in which modified nylon was used as the powder material and was electrostatically sprayed onto the spring wire and then heated at 200°C for 20 minutes to fuse it, and another example in which the spring wire was inserted into a tube. The test results with the comparative example are shown in the table below.

As can be seen from the same table, the above examples have soundproofing effects equivalent to those of the comparative examples, and are excellent in durability and rustproofing effects, and in particular, productivity is significantly improved.

Note that the soundproofing effects in the table are for amplitudes between 0 and ±25 and frequencies of 1.
When the H2 square wave was input, the sound pressure level was 80 to 85 dB without the covering, but became O with the covering.

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

The rust prevention effect was determined by a salt spray test. In the comparative examples, rust occurred after 72 to 120 hours, but in the examples, no rust occurred after 240 hours or more.

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

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

In a second example in which a foam grade modified nylon was used as the powder coating and treated in the same manner as described above, 50%
% foaming, 1/1 of the amount of powder in the first example above.
Almost the same soundproofing effect was obtained with 2.

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. In addition, the presence or absence of the highlight portion and the cross-sectional shape of the strands can be set arbitrarily.

The position of the welding of the covering part 3 to the main body 1 may be any one of the axial ends, both ends, the middle part, the entire length, etc., and in any of these, the welding position may be continuous or spaced in the longitudinal direction of the spring wire. It may be either.

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 the coating is applied to a normal level, there will be no peeling due to contact, which is sufficient to prevent rusting.

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

As described above, the spring wire of the coil spring body, which has been previously formed into a coil shape and preheated to a surface temperature of 100° C. to 150° C., is provided with at least one of the mutually opposing surfaces of the adjacent spring wires. Spray thermoplastic resin powder with a melting point of 250°C or less using an electrostatic 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 in that it is applied and adhered and then heated and 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 above-mentioned covering portion will not be present. This makes it possible to effectively prevent the occurrence of knocking noise.

In addition, since the covering part is preheated to 100'C to -50°C and fused to the spring wire using an electrostatic spray gun, both of them are sealed so that no moisture can penetrate. It is tightly adhered, and it is possible to reliably prevent detachment of the coating and corrosion of the spring strands, especially the mutually contacting parts, and it is possible to exhibit the desired performance over a long period of time.

Furthermore, by using powder with a melting point of 250°C or less, setting the preheating temperature to a relatively low temperature of 100° to 150'c, and using an electrostatic spray gun, we can achieve a good amount of resin adhesion even at low temperatures. Therefore, there is no adverse effect on the dimensions of the coil spring body, the spring constant, and the residual stress obtained by shot peening.

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. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a cutaway front view showing one embodiment of the present invention, and FIGS. 2 and 3 are front views showing different modifications on the same side. 1...Body of coil spring, 2...Spring element wire, 3...Coating portion.

Claims (1)

[Claims] 1 Pre-formed into a coil shape and heated to 100°C to 150°C
The spring strands of the coil body, which have been preheated to a surface temperature of The melting point is 2.
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 50° C. or less is sprayed using an electrostatic spray gun to adhere the powder, and then heated and fused.