RU2450904C2 - Method of fabricating shaft-sleeve-type parts - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building, particularly, to jointing of parts by inserting internal part 1 into external part 2. The latter has lengthwise channels 3, 4 to divide said part 2 into load bearing part 2.1 and sleeve part 2.2 to be jointed together to form closed cavity. Rods 5 are fitted into channels 3, 4. Permanent joint is produced on end faces of said rods by welding to seal said closed cavity. External part 2 is placed on internal part 1 to fill said closed cavity with working body at pressure required to transmit load by friction forces on joint surface between said parts 1 and 2.

EFFECT: higher durability, possibility of multiple assembly/disassembly.

3 cl, 5 dwg

Description

The invention relates to mechanical assembly production, and in particular to methods of mounting and dismounting the shaft-sleeve connection, transmitting the load due to friction on the mating surface.

A known method of obtaining a conical connection with a guaranteed interference fit, in which the oil pressure in the mating zone of the parts is served to obtain the necessary radial interference. In this case, the pressure of the oil ensures that the conical surface of the enclosing part is barrel-shaped, which makes it possible to obtain a pressure diagram on the mating surface close to the diagram of the distribution of tangential stresses under the condition of elastic deformation of the joint, as a result of which the allowable load determined by the criterion of fretting resistance increases. (See AS of the USSR No. 1229002, IPC B23P 11/02 of 06.16.82).

To ensure the installation of a known connection by a hydropress method, oil is supplied under pressure through an oil supply channel directly to the interface zone of the parts. As a result of this, after mounting the joint, an oil film remains on the mating surface, which reduces the friction coefficient and the amount of transmitted load. In addition, the position of the oil supply channel relative to the edges of the interface changes during installation, which significantly complicates the conditions of assembly due to leakage of oil at the end from the side of the short or less dense part of the interface. With multiple installation-dismantling of the connection by a hydropress method, due to the absence or insufficient size of the oil wedge, mating surfaces at the ends of the parts may be damaged.

A known method of obtaining the connection of parts of the shaft-sleeve type with a guaranteed interference fit for operation under variable loads, in which annular grooves are made on the outer surface of the sleeve before pressing in, the diameter of which is determined from the condition of equal torsional stiffnesses of the shaft and the sleeve. (See AS of the USSR No. 1656805, IPC B23P 11/02 of 12/04/87.). Taken as an analogue.

The specified method increases the bearing capacity of the connection. However, the presence of grooves on the outer surface of the sleeve does not allow to place sealing (cuffs, seals) and supporting elements (rolling and sliding bearings) on it. The magnitude of the interference fit in a known connection when it is installed by a hydropress method is limited by the concentration of stresses in the grooves of the enclosing part.

A known method of assembly with an interference fit of the female and hollow male parts, in which a male component having an internal cavity is installed in the female component with a gap. The internal cavity is communicated with a pressure source, after which the working fluid is pumped into it, with the help of which the calculated autofretting pressure is created. After stabilization of the stress-strain state of the parts, the pressure of the working fluid is removed. As a result of autofreting, a residual stress state is formed in the details, which leads to the emergence of a reliable connection with an interference fit (See AS USSR No. 1288012, IPC V23P 11/02 of 03/25/85). Adopted for the prototype.

The specified assembly method reduces the complexity and improves the quality of the assembly. However, this assembly method involves autofretting the covered part, as a result of which it cannot be reused after dismantling the connection. Thus, the resulting compound is one-piece. In addition, the presence of a cavity in the male part reduces its torsional rigidity. This even more increases the ratio of the stiffnesses of the female and hollow male parts, which worsens the condition of the load transferring by the connection (the optimal condition is the equality of the stiffnesses).

The invention is as follows. The problem to which the invention is directed, is to simplify the installation and dismantling of parts and increase the bearing capacity of the resulting compound.

This problem is solved by achieving a technical result in the implementation of the invention, which consists in reducing the mounting pressure to a minimum and in providing an increase in the allowable load on the connection.

The specified technical result in the implementation of the invention is achieved by the fact that in the known method of connecting parts of the shaft-sleeve type, which consists in pressing the shaft into the sleeve, longitudinal channels are made in the female part before being assembled, the channels being connected and separating the female part into a retaining part and bearing parts with the simultaneous formation of a closed cavity, which is filled with a working fluid under the pressure necessary to transfer the load by friction to the mating surfaces Part spans, the shape, size and location of the channels are determined from the conditions for ensuring the predetermined values of the radial stiffness of the connection of the shaft and the sleeve and (or) the value of the ratio of torsional stiffness of the cross section of the shaft and the bearing part of the sleeve, and before the injection of the working fluid, the rods are installed in the channels the cavity is "welded" along the ends, and after creating the pressure, the cavity is sealed with shut-off devices.

The radial stiffness of the shaft-sleeve connection and the torsional stiffness of the bearing part of the sleeve are calculated according to known dependencies.

The load is transferred by the connection due to frictional interaction at the contact of the mating surfaces of the parts. The magnitude of the frictional interaction is determined by the diagrams of pressure and tangential contact stresses. For connections with guaranteed interference fit, the pressure curve is dependent on the ratio

k = D ₁ / D,

where k is the coefficient of thickness;

D ₁ is the diameter of the outer surface of the female part;

D is the diameter of the mating surface,

and the plot of the tangential contact stresses - from the ratio K = k ⁴ -1,

where K is the coefficient of relative rigidity of the covering and continuous covered parts.

Moreover, if under the same interference, to increase the pressure on the contact of the mating surfaces of the parts and increase the bearing capacity of the joint, an increase in k is necessary, then to increase the bearing capacity of the joint under the condition of fretting resistance, it is necessary that the value K = k ⁴ -1 tends to unity (i.e. k decreased). The optimum is the equality of the rigidity of the covering and covered parts (i.e., K = 1, which is true for k ⁴ = 2). For design reasons, the load transfer of the shaft-sleeve connection due to frictional interaction at the contact of the mating surfaces of the parts is only advisable for k> 1.4. Obviously, even with minimal values of k = 1.4, k ⁴ > 3.8, which is significantly more than its optimal value under the condition of fretting resistance. Thus, the simultaneous fulfillment of conditions k> 1.4 and k ⁴ = 2 is impossible without the proposed assembly method.

The analysis of the prior art allows us to conclude that no analogue was found with signs identical to those of the claimed invention.

The definition of the prototype as the closest in purpose and the combination of essential features made it possible to identify significant distinctive features in relation to the technical result achieved by the invention, set forth in the claims.

Therefore, the claimed invention meets the condition of "novelty."

The claimed invention does not follow explicitly from the prior art for the specialist, since the influence of the transformations provided for by the essential features of the claimed invention on the achievement of the technical result is not established from the prior art.

Therefore, the invention meets the condition of "inventive step".

Description of the invention is illustrated in the drawing.

Figure 1 - connection of the shaft-sleeve assembly; figure 2 is a section of a shaft sleeve along AA; figure 3 - local view of the section; figure 4 is a graph of the distribution of tangential contact stresses along the contact length of the mating surfaces of the connection for various ratios of the stiffness of the sleeve and shaft; figure 5 is a graph of changes in the bearing capacity of the connection under the condition of fretting resistance for various ratios of the stiffness of the sleeve and shaft.

The connection consists of a male part (shaft) 1 with an outer diameter D and a female part (sleeve) 2 with an inner diameter D and an outer D ₁ . Parts 1 and 2 in diameter D form the contact of the mating surfaces. In the female part at diameters D ₂ and D ₃ uniformly along the lengths of their circles and longitudinally relative to the axis of the female part 2 are channels 3, 4 with diameters d ₁ and d _2, respectively. The arrangement of channels 3, 4 is made in such a way that their projections on the mating surface overlap. In channels 3.4, rods 5, 6 are installed with diameters of d ₃ ≤ d ₁ and d ₄ ≤ d ₂ , respectively, forming at the ends an inseparable connection with the female part. Channels 3, 4 functionally, without breaking up, divide the covering part 2 into a carrier 2.1 and a retaining part 2.2. Each of these parts performs a different functional purpose. Channels 3, 4 are interconnected by channels 7 and form a closed cavity inside the enclosing part. The cavity is filled with a working fluid 8. To feed the working fluid into a closed cavity of the enclosing part, additional channels 9 are made in its retaining part 2.2. A locking device 10 is installed in the channels in the form of a check valve.

The proposed method of obtaining the connection of parts of the shaft-sleeve type is as follows. Before assembly, in the female part at diameters D ₁ and D ₂ uniformly along the lengths of their circles and longitudinally relative to the axis of the female part 2, channels 3 with a diameter of d ₁ and channels 4 with a diameter of d _{2 are made} . In order to combine the channels 3, 4, the channels 7 are made in their adjacent walls. In this case, the female part 2 is divided into a bearing part 2.1 and a retaining part 2.2 with the formation of a closed cavity between them. The bandage covering parts 2.2 parts operate additional channels 9. Then, in the channels 3, 4 respectively mounted rods 5 with a diameter d ₁ ≤d ₃ and 6 with a diameter d ₄ ≥d _2, after which at their ends to form a welded one-piece female member connection. A tight cavity forms inside the female part. In the channels 9 install the locking device 10 in the form of a check valve. The cavity inside the female part allows the connection to be fixed during its installation with the male part in cases where the diameters of the internal female part and the external male part or their minor difference are equal. If the diameter of the male part is slightly smaller than the internal diameter of the female part, the mounting pressure is zero and mounting the joint is especially easy. Easy installation can be carried out with equal diameters. In this case, the mounting pressure is also equal to zero. Simple installation is ensured with the diameter of the male part slightly larger than the internal diameter of the female part, with a small geometric interference with a small mounting pressure. The female part 1 is mounted on the female part 2 with their predetermined longitudinal arrangement and through the channels 9 and the locking device 10 feed the working fluid 8 into the closed cavity of the female part formed by the channels 3, 4, 7. Upon reaching the required pressure, the connection is fixed to the pressure on all contact mating surfaces, providing the transfer of load. Sealing the cavity in order to maintain pressure for the period of operation of the connection is provided by means of a locking device 10.

An increase in the permissible load on the shaft-sleeve connection is ensured by the fact that the retaining part 2.2 of the female part 2 ensures the creation of the pressure necessary for transferring the load at the contact of the mating surfaces of the shaft-sleeve, the level of which is determined by hydrostatic pressure in the sealed cavity and is limited by the strength conditions on the internal and external surfaces of the bandage part. The dimensions of the retaining part do not affect the stiffness of the female part during torsion. The bearing part 2.1 of the female part 2 provides frictional interaction of the mating surfaces of the shaft-sleeve connection. The pressure on the contact of the mating surfaces is determined by the pressure of the working fluid in the sealed cavity of the enclosing part. The disassembly of the connection is carried out by depressurization of the cavity by mechanical action on the locking device in the direction of the arrow (figure 1).

The graph (figure 4) shows the distribution of the tangential contact stresses along the contact length of the mating surfaces of the connection for various ratios of the stiffness of the sleeve and shaft, where:

z is the current contact coordinate of the mating surfaces;

l is the contact length of the mating surfaces;

τ _z - tangential stresses on the contact of mating surfaces at a point with coordinate z;

τ ₀ - the average value of the tangential stresses on the contact of the mating surfaces;

- values of τz / τ ₀ at k ⁴ = 1.5;

- the values of τ _z / τ ₀ when k ⁴ = 2;

- the values of τ _z / τ ₀ at k ⁴ = 4,2;

- values of τ _z / τ ₀ at k ⁴ = 7.8.

The graph (figure 5) shows the change in the bearing capacity of the joint under the condition of fretting resistance, for various ratios of the stiffness of the sleeve and the shaft, where - M _{(k = 1,2)} is the moment transmitted by the joint provided that the stiffness of the sleeve and the shaft is ensured in the joint bushings with a thickness of k = 1.2 with a solid shaft;

- M _(k) is the moment transmitted by the connection, provided that the stiffness of the sleeve and the shaft is different, which is provided in the connection of the sleeve with a thickness k ≠ 1.2 with a solid shaft.

The magnitude of the load transmitted by the joint is determined by the magnitude of the hydrostatic pressure, as well as the magnitude of the predetermined ratio of torsional stiffnesses of the female and male components.

The torsional stiffness of the female part is determined by the torsional stiffness of its bearing part 2.1, taking into account the dimensions and location of the longitudinal channels 3, 4. These parameters are determined by known dependencies, providing a predetermined ratio of torsional stiffness to the male part of the supporting part 2.1 of the female part.

The above information shows that the claimed method of obtaining the connection of parts of the shaft-sleeve type during its implementation is intended for use in industry and is able to provide the required technical result.

Therefore, the claimed invention meets the criterion of "industrial applicability".

Claims (3)

1. A method of obtaining a connection of parts of the shaft-sleeve type, including pressing the male part into the female one, characterized in that longitudinal channels are made in the female part, dividing the female component into the bearing and retaining parts, which are interconnected to form a closed cavity; the rods and form at their ends by welding an integral part with a female part for sealing a closed cavity, and then mount the female part on the male one and fill it closed a cavity with a working fluid under the pressure necessary to transfer the load by friction forces on the mating surface of the female and male parts. 2. The method according to claim 1, characterized in that the dimensions of the channels and their location are determined from the condition of ensuring equality of torsional rigidity of the cross section of the covered part and the cross section of the bearing part of the covering part. 3. The method according to claim 1, characterized in that after filling the closed cavity with a working fluid under the necessary pressure, it is sealed with a locking device.

Images