RU2629401C1 - Method to strengthen cylindrical helical springs - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: method involves winding the spring with a pitch exceeding the pitch of the finished spring, heat treatment, wheel blasting, lumo control, grinding the ends of the heat-treated spring, spring hardening. In the final stage, the spring is hardened and compressed prior to contacting the coils, and pressing of compressed spring outer and inner surfaces is performed by means of hardening device when the compressed spring is located in the matrix opening. Pressing of outer and inner surfaces of compressed spring is carried out in one operation by stamping when compressed spring is in the matrix opening by spreading spring coils to the matrix opening surface with a punch entering therein, the diameter of the matrix opening equals the diameter of the compressed spring. The gap between the matrix opening and the punch surface is chosen less than the diameter of the spring coil by 0.2…5 mm.

EFFECT: increased productivity of hardening and the stability of the spring elastic properties.

1 dwg

Description

FIELD OF THE INVENTION

The invention relates to mechanical engineering, in particular to a method for hardening helical cylindrical compression springs.

State of the art

A known method of spring hardening is shot blasting, which is the most common in the production of springs. The essence of the process by processing shot is that the parts after the final mechanical or heat treatment are subjected to the impact of the flow of steel or cast iron shots. Shot blasting of springs is performed on mechanical or pneumatic shot blasting machines with steel or cast-iron beads with a diameter of 0.4 to 1.8 mm (Ostroumov, V.P. Production of coil cylindrical springs. / V.P. Ostroumov. - M.: Mechanical Engineering, 1970 . - 135 p., P. 74 ... 75).

When shot blasting on the surface of the coils, two-sided residual compressive stresses are created that prevent the opening of fatigue cracks and increase the endurance limit by 40-80% (Lavrinenko, Yu.A. Spring hardening. / Yu.A. Lavrinenko, E.G. Belkov, V. V. Fadeev. - Ufa: Publishing House "Business Partner", 2002. - 124 p., P. 16).

The disadvantage of this method is that shot blasting does not eliminate the uneven distribution of stresses over the cross section of the coil of the spring. Coils of a coil spring usually have significant curvature. This leads to a significant increase in stresses, reaching 40% on the inner fiber of the coils, compared with the stresses arising on the outer fiber of the coils (Ponomarev, S.D. Calculation of the elastic elements of machines and devices. / S.D. Ponomarev, L.E. Andreeva. - M.: Mechanical Engineering, 1980 .-- 326 p., P. 88). During operation of the spring, fatigue cracks develop on the inner side of the coil section.

It is known that the greatest stability of elastic properties, depending on the type of spring treatment, is shown after processing in the stressed state (Ostroumov, V.P. Production of coil cylindrical springs. / V.P. Ostroumov. - M.: Mechanical Engineering, 1970. - 135 p. , p. 93 ... 96). By analogy with this, the shot blasting of the springs should be carried out in a compressed state until the coils touch. During shot blasting of a compressed spring, the shot flow will reach only the outer side of the coils, and the inner side of the coils will remain unstressed, which is a drawback.

A known method of hardening cylindrical coil springs, including winding, hardening, tempering, bead-blasting and troweling, and at the final stage, the inner surface of the springs is hardened. Hardening is carried out by pulling the mandrel or by impact on the inner surface of the coil of the spring. The proposed device for implementing the method — a mandrel or a reinforcing head with rollers — is mounted on a lathe, in the clamping device of which a spring is fixed (Patent RU 2462519, IPC C21D 9/02, C21D 7/06, B21F 35/00. A method for strengthening cylindrical coil springs. / Shavrin O.I., 2011115786/02; Stated April 20, 2011; published September 27, 2012. Bull. No. 27).

The disadvantage of this method, adopted as a prototype, is the difficulty of securing the spring in the clamping device of the lathe and the possibility of damage to its coils with an uneven distribution of clamping forces and forces from pulling the mandrel or from the impact of the rollers of the head of an unnamed brand (model).

The disadvantages are the length of the process of installing the spring in the clamping device (it is known that the clamping device of the lathe is a three-jaw chuck in which it is impossible to do this) and removing from it, bringing the spring and the working tool (mandrel or head with rollers) into rotation, feeding and removal of the working tool. The issue of removing the spring from the working tool is not resolved, which is also a drawback.

In this method, the term “regrowing” refers to a 3- or 5-fold compression of the spring until the coils touch, which is not in fact a regression, but is considered as preliminary draft, which is used to detect gross deviations from the process. The main draft of the springs, including cyclic ones, is carried out by the gouging operation, which occurs in the first 20-30 hours and then increases slightly (Ostroumov, V.P. Production of coil cylindrical springs. / V.P. Ostroumov. - M.: Mechanical Engineering, 1970. - 135 p., P. 65 ... 68). Therefore, in this method, regressing is not actually presented or applied.

It is known that the greatest stability of elastic properties, depending on the type of spring treatment, is shown after processing in the stressed state (Ostroumov, V.P. Production of coil cylindrical springs. / V.P. Ostroumov. - M.: Mechanical Engineering, 1970. - 135 p. , p. 93 ... 96). By analogy with this, the hardening of the inner surface of the spring in the present invention should be carried out in a compressed state, which is not done. This is also a disadvantage of the prototype method.

Disclosure of invention

The objective of the invention is to increase the stability of the elastic properties of the spring and reduce the installation time and removal of the spring from the device and the hardening time of the springs in a compressed state. The technical result to which the invention is directed is to create plastic deformations riveted on the outer and inner surfaces of the coils of a compressed spring in one operation.

The technical result is achieved by the fact that in the method of hardening coil cylindrical springs, including winding a spring from a pre-hardened or hardened wire with a step exceeding the step of the finished spring by the amount of allowance for covering and stamping (6-14% of the height of the finished spring), heat treatment - tempering for springs made of pre-hardened wire or hardening and tempering for springs made of hardened wire, lumocontrol, grinding of the ends, shot blasting, lacing for 20-30 hours, after which compresses the spring located in the hole of the matrix of the hardening device until the coils touch and harden its outer surface and inner surface by stamping in one operation. The outer and inner surfaces of the compressed spring are hardened by expanding the device punch that enters the spring, where the diameter of the device’s matrix hole is equal to the diameter of the compressed spring, and the gap between the matrix hole surface and the punch surface is 0.2 ... 5 mm less than the diameter of the coil of the spring, depending on the diameter coil. The compression of the spring, the hardening of the outer and inner surfaces of the compressed spring and their sequence provides the design of the device.

The implementation of the invention

The method of hardening coil springs is as follows. The spring is coiled with a step exceeding the step of the finished spring by the amount of allowance for troweling and stamping (6 ... 14% of the height of the finished spring), heat treat, perform lumocontrol, grind the ends, perform shot blasting and grate for 20-30 hours. Then, the spring located in the hole of the hardening device is compressed until the coils touch and the outer and inner surfaces of the compressed spring are riveted by means of the hardening device punch included in the spring, the diameter of the device opening being equal to the diameter of the compressed spring, and the gap between the hole and punch surfaces being chosen less than the diameter of the spring coil by 0.2 ... 5 mm. In this case, the compression and hardening of the inner and outer surfaces of the compressed spring is carried out by stamping in one operation. The sequence of compression of the spring and the bursting of its coils provides the design of the hardening device.

For hardening by stamping the inner and outer surfaces of the compressed spring, it is proposed to use the device shown in FIG. 1 (a.s. 825253 USSR, M. Cl. ³ B21F 35/00, F16F 01/00. Device for covering the springs. / Tebenko Yu.M. - No. 2822172 / 25-12; claimed 06.08.79; publ. 04.30.81, Bull. No. 16 for 1981 - 3 pp.). Hardening is performed as follows. The upper plate 2 is lowered by the movement of the press. The entrance part of the punch (mandrel 1), and then the expanding part of the punch, enter the hardened spring 5 located in the device matrix, after which the movable sleeve 9 abuts the spring, compressing it until the coils touch. Next, the working part 4 of the punch enters the compressed spring 5, bursting its coils and pressing them to the surface of the hole of the device matrix (cup bore 6). Due to the fact that the gap between the surfaces of the hole of the matrix and the working part 4 of the punch is smaller than the diameter of the coil of the spring, the inner and outer surfaces of the compressed spring are riveted. After exposure, the upper plate 2 with the punch 1 is raised. The movable sleeve 9, sliding along the mandrel under the action of the springs 10, pushes the spring 5 from the punch, leaving the spring 5 in the hole, from where it is removed mechanically or manually.

Using the presented device, it is possible to compress to the contact of the coils and create on the inner and outer surfaces of the spring compressed to the contact of the coils of the spring plastic deformations (hardening) in one operation, accelerating the draft and increasing the life of the spring, working under conditions of prolonged cyclic loading.

The presented operation of hardening the springs in a compressed state makes it possible to create compressive residual stresses on the inner and outer surfaces of the coil turns that add up to the tensile stresses arising during the spring operation and reduce them.

The heat-treated spring (hardening and tempering for hardened wire springs and tempering for pre-hardened wire springs), grinding of the ends, shot blasting, troweling for 20-30 hours, undergoes compression until the coils come into contact and additional processing of the inner and outer surfaces of the coils in compressed state in one operation.

The presented operation of hardening the inner and outer surfaces of a compressed spring by stamping is more productive than the known operation of hardening the inner surface by turning, since it occurs on a high-speed stamping press and can be mechanized using the devices used for stamping to install and remove parts from the device. The installation time of the spring in the hardening and recessing device of the spring does not exceed 1-2 s, while the duration of the installation of the spring in the clamping device of the lathe, the time of rotation and pushing of the mandrel or rolling rollers on the inner surface of the spring and the time of removal of the spring from the clamping device of the lathe is significantly exceeds the time of the hardening operation according to the proposed method.

It is supposed to increase the durability (resource) of springs hardened in this way by 1.4 ... 2 times relative to the durability of springs hardened by known methods, which is consistent with that shown in the work (Tebenko, Yu.M. Problems of production of high-speed springs and ways to solve them. Monograph. / Yu.M. Tebenko. - Stavropol: PA "World of Data", 2007. - 152 p.) Increase in durability (resource) of springs when using plastic hardening of coils with loads of 10 ... 300F ₃ .

The invention in comparison with the prototype and other known technical solutions has the following advantages:

- hardening of the inner and outer surfaces of the spring is performed in a compressed state in one operation;

- the greatest stability of the elastic properties of the springs;

- high performance spring hardening.

Claims (1)

A method of hardening screw cylindrical compression springs, including winding the spring in increments greater than the finished spring pitch, heat treatment, lumi-control, grinding the ends of the heat-treated spring, shot blasting, numbing the spring by compressing the spring until the coils come into contact and hardening the outer and inner surfaces of the compressed spring, characterized in that regrowing is carried out within 20-30 hours, and the hardening of the outer and inner surfaces of the spring is performed in one operation by stamping when the compressed spring is in the hole Only the matrix between which the hole diameter is equal to the diameter of the compressed spring and the gap between the surface of the hole of the matrix and the surface of the punch is chosen to be 0.2 ... 5 mm less than the diameter of the coil of the spring .

Images