RU2688550C1 - Support plain bearing - Google Patents

Abstract

FIELD: machine building.SUBSTANCE: invention relates to machine building, particularly, to plain bearings with self-adjusting cushions, and can be used, for example, in high-speed centrifugal compressors. Support sliding bearing includes housing (1) with internal cylindrical surface (2) and self-adjusting cushions (3–7) arranged in it, resting on elastic elements in the form of plate springs (8). Plate springs (8) are installed on paired support platforms (15) on surface (2), between which there are grooves (16), providing possibility of deflection of plate springs (8). Pair support platforms (15), on which plate springs (8) are installed, which are located under unloaded cushions, are made at a smaller distance from longitudinal axis of surface (2), in comparison with paired support platforms (15), on which plate springs located under loaded cushions are installed.EFFECT: increased reliability and durability of operation of the plain bearing at dynamic loads.4 cl, 2 dwg

Description

The invention relates to mechanical engineering, in particular, to the details of machines - bearings with self-aligning pads. Known support bearing, comprising a housing with an annular groove on the inner surface and self-aligning pads installed therein on elastic elements, on the back sides of which U-shaped grooves are made, the walls of which are cylindrical with axes located in planes perpendicular to the longitudinal axis of the bearing, and with protuberances inside the grooves, and the elastic elements are made in the form of cylindrical rods installed parallel to the longitudinal axis of the bearing in the grooves of the pillows and resting on the chrome Key ring undercut housing (USSR Copyright Certificate № SU 1083001 A, published 03/30/1984)

The disadvantage of this technical solution is that the gaps between the working surfaces of all pillows and the surface of the shaft at its central position (the shaft axis and the inner surface of the bearing housing are the same) in the planes passing through the axis of the inner surface of the housing and the points of contact of the pillows with elastic elements are equal. As a result, when the bearing is in operation, when the shaft axis is not in the center position, the gaps between the working surfaces of the unloaded cushions and the shaft surface become larger than the gap that occurs when the shaft is in the center position. This leads to a significant decrease in hydrodynamic forces in the lubricant layers of these pillows and to an increase in the amplitude of oscillation of the shaft journal in the bearing in the event of dynamic loads, for example, from the unbalance of the rotor.

The disadvantage is the complexity of the manufacture of pillows, low accuracy ensure the calculated values of the gaps in the bearing due to the long dimensional chain. In addition, with this configuration of the groove, there is a point contact between the pillow and the elastic element, which often leads to the pinching of the contact zone and the deterioration of the pillow self-installation.

Also known is the thrust bearing bearing, comprising a housing with an inner cylindrical surface and self-aligning pads accommodated therein, resting the back side on elastic elements made in the form of leaf springs through hinges enabling the cushions to be self-installing. Lamellar springs are installed on paired bearing pads on the inner cylindrical surface of the body, between which there are grooves, which provide the possibility of deflection of lamellar springs (USSR Author's Certificate No. 418642, published on 03/05/1974)

This technical solution in terms of the accuracy of ensuring the calculated values of the gaps in the bearing and avoiding a hug in the contact area of the back side of the pillows is preferred, although simpler solutions are known when the ability to self-install the pillows is provided, for example, by making the back side of the pillow in the form of a cylindrical surface, longitudinal axis which is parallel to the longitudinal axis of the inner cylindrical surface of the bearing housing, with a radius smaller than the radius of the inner cylindrical surface buildings (V.A. Maksimov, G.S. Batkis, High-speed sliding bearings for hydrodynamic friction, Kazan, publishing house “Feng”, 2004, 406 p.).

However, the main disadvantage of this technical solution is to increase the amplitude of oscillation of the shaft journal in the bearing when dynamic loads occur due to a decrease in hydrodynamic forces in the lubricant layers of the unloaded pillows.

Despite the fact that the known technical solutions provide the possibility of providing a given stiffness of the elastic elements depending on the intended operating modes of the bearing, they do not provide for the establishment of various gaps between the shaft surface and the working surfaces of loaded and unloaded pillows at the central position of the shaft.

The problem to which the invention is directed is to increase the reliability and durability of the support bearing under dynamic loads, by reducing the effect of shock loads on self-aligning airbags and reducing the amplitude of the shaft shaft oscillation relative to the bearings.

The technical result is achieved by the fact that in a known support bearing, comprising a housing with an inner cylindrical surface and self-aligning pads accommodated therein, supported by the back side, made in the form of a cylindrical surface, the longitudinal axis of which is parallel to the longitudinal axis of the inner cylindrical surface of the housing, with a radius smaller the radius of the inner cylindrical surface of the housing, on the elastic elements in the form of a leaf spring, forming a contact line located in p Adial plane, in which the thickness of the cushion is maximum, while the leaf springs are installed on paired bearing pads on the inner cylindrical surface of the housing, between which there are grooves providing the possibility of sagging plate springs, paired bearing pads on which the plate springs are installed under the differently loaded cushions , made at different distances from the longitudinal axis of the inner cylindrical surface of the housing.

New is also the fact that paired bearing pads, on which lamellar springs are installed under less loaded cushions, are made at a shorter distance from the longitudinal inner cylindrical surface of the body than paired bearing pads to which lamellar springs are placed under more loaded cushions.

In addition, the paired bearing pads are made on both sides, symmetrically and parallel to the line of contact of the back side of the cushion and the leaf spring, while the depth of the groove between the pair of bearing feet is less than the allowable amount of deflection of the leaf spring.

The implementation of paired bearing pads, on which the leaf springs located under the differently loaded cushions are installed, at different distances from the longitudinal axis of the inner cylindrical surface of the housing allows for the installation of reduced gaps between the shaft surface and the working surfaces of the unloaded cushions for the central position of the shaft. When the bearing is in operation, when the shaft is displaced from the center position, the gaps in the lubricant layers of the unloaded pillows increase, which leads to a decrease in hydrodynamic forces in the lubricant layers of these pillows. But thanks to the previously established reduced clearances, these forces remain sufficient to prevent the shaft from moving towards the unloaded cushions when dynamic loads occur.

As a result, the amplitude of oscillation of the shaft journal relative to the bearing is reduced, the reliability of its operation increases.

Due to the fact that lamellar springs under unloaded cushions are installed at a shorter distance from the center of the bearing than under loaded cushions, the unloaded cushions acquire the ability to track the movement of the shaft under the action of dynamic load, which contributes to reducing the impact loads on the cushions and increasing the reliability and durability of the bearing.

The proposed plain bearing is illustrated by the drawings shown in FIG. 12:

in fig. 1 shows a cross section of the bearing;

in fig. 2 shows a longitudinal section of the bearing A-A of FIG. one.

The plain bearing (Fig. 1) includes a housing 1 with an inner cylindrical surface 2, mounted self-aligning pillows 3, 4, 5, 6.7, uniformly around the circumference, in the housing 1, relying on the elastic elements in the form of plate springs 8, O-rings 9 (Fig. 2), which are mounted on the inner cylindrical surface 2 of the housing 1 with their seating surfaces 10 and secured to it with screws 11. The cushions 3, 4, 5, 6, 7 are held in place by the sealing in the axial and radial directions and the rings 9, on the inner end surfaces of which are made annular recess in which the shoulder portions 12 are self-aligning pads.

From displacement in the circumferential direction of the cushion are held by cylindrical rods 13 mounted parallel to the longitudinal axis of the bearing in the spaces between the cushions and fixed in the holes 14 made in the sealing rings 9.

Lamellar springs 8 are installed on paired bearing pads 15 on the inner cylindrical surface 2, between which there are grooves 16, providing the possibility of deflection of lamellar springs 8. From falling out, lamellar springs are retained by flats 17 made on the seating surfaces 10 of the sealing rings 9.

The possibility of self-installation of pillows is ensured by the fact that its back side is made in the form of a cylindrical surface with a radius less than the radius of the inner cylindrical surface 2 of the housing 1 by an amount that prevents them from touching, and their longitudinal axes are parallel.

Touching the back side of the cushion and the leaf spring occurs along the contact line 18, around which the cushion rotates during self-installation. In the housing 1 there are channels 19 for supplying lubricating fluid to the working surfaces of the pillows.

The distance L _i from the longitudinal axis of the inner cylindrical surface 2 of the housing 1 to the paired support sites located under the i-th pad is determined from the expression

L _i = r + H + h + h _oi ,

where r is the radius of the shaft journal 20; H - the height of the pillow in the area of the line of contact; h is the thickness of the leaf spring; h _oi - the gap between the working surface of the i-th pillow and the surface of the shaft 20 at its central position (the longitudinal axis of the shaft and the inner cylindrical surface coincide); i = 1 ... z; z is the number of pillows.

A characteristic feature of the plain bearings with self-aligning pads is that due to the self-aligning of the pads, the hydrodynamic forces in the lubricating layers of the pads occur even when the shaft is in the center position, for example, for vertical shafts. But when the shaft is displaced from the center position, the hydrodynamic forces in the lubricant layers of the unloaded cushions (with increased gaps) become insignificant or turn to zero, for example, for reversing cushions.

Therefore, in order that when the bearing operation, when the neck of the shaft, located under the force F, is in some equilibrium point not coinciding with a bearing center in lubricating layers of loaded and unloaded cushions arose hydrodynamic forces necessary to satisfy the conditions 0 <h _Pi ≤α⋅δ, where h _Pi - the gap between the working surface of the i-th pillow and the surface of the shaft, located at some equilibrium point; δ = (R _P -r) is the radial clearance in the bearing; R _P - the radius of the working surface of the pillow; α - the safety factor, taken with regard to the degree of irreversibility of the pillow and the mode of operation of the bearing.

For reversible pillows, you can take α = 0,8 ÷ 0,9. For loaded pillows 3, 4, 7, this condition is always fulfilled when the shaft journal is displaced from the center of the bearing. For unloaded pillows 5, 6, this condition is satisfied for h _oi ≤α⋅δ (1 + ε⋅cosϕ _i ), where ε = е / δ is the relative eccentricity; e is the displacement of the center of the shaft from the center of the bearing under the action of force F; ϕ _i - the angle of the i-th unloaded cushion, measured from the line of action of the load.

Thus, for the considered bearing with the number of pillows z = 5 and the direction of load F on the pillow 3 (see Fig. 1), according to the condition considered, the gaps between the working surfaces of the pillows and the surface of the shaft journal at its central position should be determined from the conditions:

- for the loaded pillow 3 h _o1 ≤δ; - for loaded pillows 4, 7 h _o2 ≤δ; - for not loaded pillows 5, 6 h _o3 ≤α⋅δ (1 + ε⋅cosϕ _{i = 3} ).

The actual values h _o1 , h _o2 , h _o3 are specified when calculating the bearing for a given mode of operation.

The distances corresponding to these gaps from the longitudinal axis of the inner cylindrical surface to the paired bearing pads will be equal to:

- for the loaded pillow 3 L ₁ = r + H + h + h _o1 ; - for loaded pillows 4, 7 L ₂ = r + H + h + h _o2 ; - for not loaded pillows 5, 6 L ₃ = r + H + h + h _o3 .

The thickness of the leaf spring h is determined from the condition of ensuring the required compliance and strength at its expected maximum deflection.

The bearing works as follows. The lubricating fluid supplied to the bearing through the channels 19 is entrained by the rotating shaft 20 into the gaps between the shaft surface and the working surfaces of the pillows 3, 4, 5, 6, 7, which become wedge-shaped due to the self-installation of the pillows (turning around the contact line 18).

In this case, hydrodynamic forces arise in the lubricant layers, under the action of which the shaft occupies a certain equilibrium position, characterized by the displacement “e” of the shaft center from the bearing center “O” and the eccentricity angle measured from the load action line in the shaft direction.

For bearings with a symmetrical arrangement of pillows relative to the line of action of the load, this angle is small, and therefore it is customary to assume that the center of the shaft is in the line of action of the load in the equilibrium position. At the same time between the working surfaces of the pillows 3, 4, 5, 6, 7 and the surface of the shaft are set such values of the gaps h _Pi , in which the hydrodynamic forces are balanced by the elastic forces of the plate springs.

Due to the fact that for unloaded cushions, reduced gaps h _oi (for the center position of the shaft) were set, even with a significant displacement of the shaft from the center position, the hydrodynamic forces in the lubricant layers of the upper unloaded cushions 5, 6 would be sufficient to limit the movement of the shaft to the direction of the unloaded pillows when dynamic forces occur.

When a dynamic load of the pillow occurs due to the possibility of deflection of the leaf springs will move in the radial direction, thereby avoiding the action of significant shock loads that can lead to chipping of the anti-friction layer on the working surface of the pillow. Moving the pillow in the radial direction leads to an increase in the gap and a decrease in hydrodynamic forces. Therefore, under the action of the elastic forces of the leaf spring, the pillow returns to its original position.

The installation of leaf springs under unloaded cushions at a shorter distance from the center of the bearing than under loaded cushions allows unloaded cushions, along with loaded cushions, to track the movement of the shaft under the action of dynamic load.

The invention helps to reduce shock loads on self-aligning pads and to increase the reliability and durability of the bearing.

Claims (4)

1. A plain bearing, comprising a housing with an inner cylindrical surface and self-aligning pillows placed therein, supported by the rear side in the form of a cylindrical surface, the longitudinal axis of which is parallel to the longitudinal axis of the inner cylindrical surface of the housing, with a radius smaller than the radius of the inner cylindrical surface of the housing, on elastic elements in the form of a leaf spring, forming a contact line located in the radial plane in which the thickness of the cushion is maximum at that, lamellar springs are installed on paired bearing pads on the inner cylindrical surface of the housing, between which there are grooves providing the possibility of sagging lamellar springs, characterized in that the paired bearing pads on which lamellar springs under differently loaded cushions are installed are made on different distances from the longitudinal axis of the inner cylindrical surface of the housing. 2. Bearing according to claim 1, characterized in that the paired bearing pads, on which the leaf springs are installed, which are under less loaded cushions, are made at a smaller distance from the longitudinal axis of the inner cylindrical surface of the housing, than the paired bearing pads, on which the leaf springs are mounted under more loaded cushions. 3. The bearing according to Claim. 1, characterized in that the paired bearing pads are made on both sides, symmetrically and parallel to the line of contact of the back side of the cushion and the leaf spring. 4. The bearing according to claim. 1, characterized in that the depth of the groove between the paired bearing pads is less than the permissible value of the deflection of the leaf spring.

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