RU2244176C2 - Method of tightening gas butt - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: method includes tightening up to force bounded between the limit of proportionality and flexibility.

EFFECT: improved design.

1 dwg

Description

The invention relates to the field of engineering and can be applied in the automotive industry, for example in the engine industry.

A known method of tightening and control torque [1]. The disadvantage of this method is that the dispersion of the axial force of the tightening bolts (studs) reaches ± 25%, which reduces the reliability and durability of the gas joint.

A device is known [2, 3, p. 347-350], the operation of which is based on a method of tightening a gas joint by the yield strength of a material of a bolt or stud, with tightening control using an electronic device. This method is adopted as a prototype. Its essence is that in the process of tightening the electronic device compares the signals of the increment of torque from the angle of rotation of the bolt (nut). When entering the fluidity section of the material, the equality of the compared signals is violated and the puff stops.

The disadvantage of this method is the following. When the engine is running, in the case of a large difference in temperature coefficients of linear expansion of the materials of the bolts and cylinder head (2 or more times), tensile stress in the bolts increases by 30 ... 40%, and inside the cylinders, in addition, a pulsating gas load always acts additionally loading bolts. These factors lead to the fact that the tensile stresses of the bolts can exceed not only the yield strength, but also the zone of hardening of the material, although the place of future rupture (with a smooth dynamic load) is already being outlined in the stage of hardening [4, p. 53, 54]. The combination of the above factors in practice often leads to relaxation of the structure of the material, which over time causes residual deformations in the body of the bolt (stud), leading to a weakening of the gas joint.

The problem solved by the invention is to increase the reliability and durability of the gas joint.

This task is carried out due to the fact that the tightening control is carried out using an electronic device, and the gas joint is completed in a non-linear section of the tensile diagram of the material of the tightening bolt (stud), and the tightening force is limited by the point of proportionality, on the one hand, and the point of elasticity, on the other hand.

This combination of known and new features can improve the reliability and durability of the gas interface.

The essence of the proposed technical solution can be explained by the tensile diagram of materials [4, p. 61], where σ _n is the proportionality limit, and σ _y is the elastic limit to which the material does not receive permanent deformations. The points σ _n and σ _y differ from each other in the parameter of relative deformation (ε) by only 0.001 ... 0.005,% and their finding is possible only with the use of high-precision (precision) laboratory equipment, special methods for measuring and processing the results. The practice of tightening the gas joints of internal combustion engines requires more accessible and simple methods for recording the points σ _n and σ _y . The proposed method is based on the determination of the inflection points σ _n 'and σ _y ' (the first derivative of the points σ _n and σ _y ) using the well-known in mathematics technique “study of functions” [5, p.520 and 6, p.371, 372] and their registration using, for example, magnetostrictive force or torque sensors [7, p. 156, 157 and 196].

The proposed method is illustrated in the drawing:

a) the dependence diagram σ (ε) [4, p. 61], where:

σ is the stress developed in the material of the bolt (stud);

ε is the relative deformation of the bolt (stud);

σ _n is the limit of proportionality;

σ _y is the elastic limit;

b) the dependence diagram σ ′ (ε) is the first derivative of the function σ (ε), where:

σ _n 'is the inflection point corresponding to the limit of proportionality;

σ _y 'is the inflection point corresponding to the elastic limit.

The method is as follows.

During the tightening of the gas joint using an electronic device, which can be used magnetostrictive sensors of forces, torques, whose work is based on the registration of the first derivative σ ′ (ε) [7, p. 156, 157 and 196], the rate of change functions σ ′ (ε). Upon reaching the point σ _n (Fig. 1a) corresponding to the proportionality limit, the sensor detects a sharp change in the function σ ′ (ε) (Fig. 1b), which is a signal for completing the tightening process. This fixes the relative strain (ε) at the level of 0.001%. By adjusting the magnetostrictive sensor to a value of relative deformation (ε) in the range of 0.001 ... 0.005%, the registration of the tightening force in the range between the points σ _n and σ _{y is} provided. Considering that the elastic properties of the material are preserved up to a stress called the elastic limit [4, p. 61], this method provides a technical effect, and can also be carried out using means known to the technique.

Sources of information

1. Gordeev V.N., Buryanov V.A. Improving the reliability of the gas joint of a VAZ-341 diesel, Automotive: Information Digest. Tolyatti, 1989

2. A.S. RF №1550341. Device for controlling the tightening of threaded connections, author Gordeev V.N., BI No. 10, 1990

3. Automation of tightening the gas joint of the internal combustion engine and increasing its reliability. Materials of the All-Russian Scientific and Technical Conference “Technical University-Science, Education and Production in the Region”, part 2, Tolyatti, 2001

4. Feodosiev V.I. Strength of materials. - M., Science, ed. 6, Ch. Physics and Mathematics Editorial Board, 1972

5. G. Korn, T. Korn. Math reference book for scientists and engineers. - M., 1874

6. I.N. Bronstein, K.A. Semendyaev. Math reference book for engineers and college students. - M., 1980

7. E.S. Levshina, P.V. Novitsky. Electrical measurements of physical quantities (measuring conversion), Textbook for universities. - L., Energoatomizdat, Leningrad Department, 1983

Claims (1)

The method of tightening the gas joint, in which the tightening is controlled by an electronic device, and the tightening is completed with a force that corresponds to a point located in the range of the non-linear section of the tensile diagram of the material of the tightening bolt or stud, characterized in that the tightening force is limited to a range corresponding to the range located between the point of limit of proportionality and the point of limit of elasticity.