RU2811968C1 - Method for forming rollers with convex generatrix - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to the production of bearings, and can also be used for shaping crowned rollers used as free rolling bodies. The method includes placing the workpieces on transport rollers or on the surface of the leading abrasive wheel and communicating a longitudinal feed to the workpieces with respect to the abrasive tool that performs stock removal. A gap is provided between the parts being processed, which is determined using the given relationship.

EFFECT: use of transport rolls of complex shape in medium-scale production of bearings is eliminated.

1 cl, 7 dwg, 1 ex

Description

The invention relates to mechanical engineering, in particular to the production of bearings, and can also be used for shaping rollers used as free rolling bodies.

Modern friction units, containing roller bearings in their design, perceive enormous work loads transmitted from the outer ring to the inner ring through the rolling elements. At the same time, it is well known that if the shape of the rolling elements is cylindrical, narrow areas of stress concentrators are formed in their cross sections adjacent to the ends (the so-called “edge” effect), which leads to their rapid destruction. It is advisable to make surfaces operating under load under conditions of linear or plane contact slightly convex (Fig. 1), which ensures central application of the load and eliminates increased edge pressures arising from inaccuracies in manufacturing and installation. This technique, called bombing, is widely used for parts operating under high loads under rolling conditions.

Currently, the convex profile of the generatrix is mainly formed during centerless grinding and superfinishing operations [1-8]. In this case, the generatrix of the rollers transporting the processed rollers through the processing zone is made of a complex shape, combining convex and concave sections. This ensures the advancement of the rollers being processed during the process of removing the allowance along a trajectory that is a copy of the profile of the transport rolls.

A device is known [10], which contains a method for superfinishing bombed rollers (prototype), in which the workpieces 2 are placed on transport rollers 1, made with a generatrix of complex shape with convex and concave sections (Fig. 2).

The transport rolls 1 impart a longitudinal feed to the workpieces 2 along a complex trajectory under the oscillating abrasive bars 3, which remove the material. In this case, a profile of the longitudinal section of the processed parts is formed, which has a convex shape.

The main disadvantages of this method are the following: the manufacture of rolls for processing parts with complex profiles requires expensive specialized multi-axis machines, as a result of which the cost of the roller device reaches up to 40% of the cost of the entire machine [3]. In addition, during long-term operation of machines, wear of the rolls occurs, requiring restoration, which is difficult in the conditions of tool shops of machine-building enterprises that lack specialized expensive equipment. Therefore, due to the high cost, the same roller device is used to process parts of a certain size range, which leads to errors in the shape of parts due to the deviation of the forming trajectory from the required one.

The technical problem of the invention is the development of a method for forming rollers with a convex generatrix, allowing it to be used not only in mass and large-scale production, but also in medium-scale production without the use of transport rolls of complex shape.

The proposed technical solution is a method of forming a convex generatrix of the profile of roller rolling elements without the use of expensive profiled transport rolls, the accuracy of which does not depend on the degree of their wear. In addition, the proposed method provides a significant reduction in the technological cost of processing operations for bombed rollers.

To consider the essence of the proposed method, let us consider the mechanism of profile formation in the longitudinal section of parts processed with abrasive tools (Fig. 3).

In fig. 3 schematically shows an abrasive tool with a length , which is pressed against the surface being processed with a force P having a constant value. In the general case, the source of force P can be springs, pneumatic and hydraulic drives (with force closure of the contact between the tool and the workpiece) or elastic tension in the AIDS system (with kinematic closure of the contact).

Let us assume that the characteristic size of the tool (the width of the abrasive stone or the diameter of the grinding wheel) is the same along its entire length. We assume that the properties of the material being processed are uniform throughout the entire volume of the layer being removed; The cutting properties of abrasive grains are also uniform over the working surface of the tool.

Under the conditions described above, the number of cutting grains passing through the sections of the part on segment AB (Fig. 3) is variable, since it depends on the cutting depth. The cutting depth in this case is variable, because at a constant force P, with increasing overtravel, the number of active (cutting) grains decreases and, as a result, the pressure on each of them increases, because of this the grains are embedded to a greater depth. Therefore, in section AB equal to the length of the block , additional removal takes place.

There is a known dependence for determining the number of active grains when changing the depth of their penetration into the treated surface [9]:

where Z ₀ is the total number of grains per unit surface of an abrasive tool for a given grain size (grain size);

h is the distance from the top of the most protruding grain from the bunch to a certain level;

d ₀ - grain size (granularity).

As the overtravel increases, the number of active grains decreases in proportion to the ratio and Z(x) grains will pass through an arbitrary section X-X of segment AB (Fig. 3)

where t(x) is a function of changing the cutting depth

As a result, the load on the abrasive grains increases, and the depth of incision of the grains into the treated surface also increases. The function describing this phenomenon has the form:

Expression (3) is the equation of a curved segment with a generatrix of length , adjacent to the end of the part (Fig. 3), formed as a result of one working stroke of the tool, in the case when the block completely runs over the edge of the part.

In fig. Figure 4 shows a graph of the function of the amount of allowance removal in a processing scheme with the bar completely extending beyond the right end of the workpiece.

In sections adjacent to its left end, the shape of the generatrix is described by a mirror relationship with respect to (3), therefore the longitudinal profile of the machined part in this case is barrel-shaped.

On centerless cylindrical grinding and super-finishing machines in conditions of mass and large-scale production, the processing of cylindrical rollers is carried out with a longitudinal feed “per pass”. In this case, the workpieces in the processing zone move in a flow, resting their ends against each other and forming, as it were, a single workpiece of infinite length (Fig. 5).

The abrasive tool smoothly moves from processing the previous workpiece to processing the next workpiece without interrupting contact with them. Often there are even several workpieces in the processing zone at the same time. It is noteworthy that, although in fact the processing is carried out with the grinding wheel completely extending beyond the boundaries of the workpiece, the convex profile characteristic of this scheme is not formed. The implementation of such a scheme eliminates the influence of overtravel on the process of profile formation and avoids the formation of its error. If the workpieces are moved apart, providing some gap between them, then, due to the variable amount of removal, the patterns described above will begin to operate, since a real overtravel a will occur (Fig. 6).

In fig. Figure 6 shows one of the processing options for bombed rollers, namely their centerless grinding: 1 - the initial workpiece for the bombed roller, which moves from left to right into the working zone of centerless grinding; 2 - roller being processed in the cutting stage; 3 - roller being processed at the stage of removing the main allowance; 4 - final processed roller with a convex generatrix; 5 - grinding wheel; 6 - leading abrasive wheel; 7 - intermediate parts that provide a gap with a calculated distance a between the rollers being processed.

By changing the distance between the workpieces, i.e. By adjusting the amount of overtravel a, for example, using intermediate parts of standardized length (Fig. 6), you can control the amount of profile convexity and form the standard value of the “bomb”.

The distance a required to form a “bomb” can be determined as follows:

where Δ _b is the specified value of the “bomb”

Example

Let L=20 mm; t=0.01 mm; Δ _b =0.005 mm.

Then a=8.0 mm.

The proposed method can be similarly implemented with centerless superfinishing according to the scheme shown in Fig. 6, using intermediate parts that provide a distance a between the workpieces.

The dependencies obtained above describe the results of the formation of the longitudinal profile of parts processed with abrasive tools with a complete overrun of the latter, with the ratio ≤L, where L is the length of the workpiece, - length of the abrasive tool.

On centerless cylindrical grinding machines, rollers are processed per pass, while >>L. This scheme (Fig. 6) makes it possible to obtain a symmetrical convex profile of the processed part without kinks and without cylindrical sections (Fig. 7).

In fig. 7 shows the shape of the roller processed by the proposed method. The shaded area represents the amount of allowance removed from the surface of the original cylindrical workpiece; the size of the “bomb” is the half-difference between the diameters d _max and d _min .

Literature

1. A.s. 275773 USSR MKI V24V 5/18. Method for obtaining a convex rolling surface of rollers / N.N. Mikhailov, N.F. Spitsyn // Discoveries. Inventions, 1970, No. 22.

2. A.s. 347174 USSR MKI V24V 5/18. Method for processing bombed rollers / V.A. Petrov, B.A. Zyryanov // Discoveries. Inventions, 1972, No. 24.

3. Balaev Andrey Fedorovich Ensuring the accuracy of centerless superfinishing based on optimal geometric adjustment of equipment. Diss. Ph.D. those. Sci. 2006.

4. Bochkareva I.I. Study of the process of formation of a convex surface of cylindrical rollers during centerless superfinishing with longitudinal feed: Diss. Ph.D. Saratov, 1974. - 176 p.

5. Brodsky A.S., Antonova N.A. On the theory of setting up a centerless grinding machine for grinding the convex rolling surface of conical rollers // Proceedings of VNIPP. M., 1970, No. 3. - pp. 53-58.

6. Gundorin V.D., Bochkareva I.I., Afanasyeva A.I. Manufacturing of transport rolls for centerless superfinishing of rollers with a convex generatrix // Finishing of machine parts: Interuniversity. scientific Sat. Saratov, 1974. - pp. 59-64.

7. Gundorin V.D., Bochkareva I.I., Afanasyeva A.I. Formation of the longitudinal section profile of cylindrical rollers with a convex generatrix during centerless superfinishing // Bearing Industry, 1974, No. 1. pp. 24-29.

8. Kitaev V.I. Improving the accuracy of centerless grinding of barrel-shaped rollers // Bearing industry, 1960, No. 2. P. 2629.

9. Korolev A.V. Study of the processes of formation of tool surfaces and parts during abrasive processing. Publishing house Sarat. State University. 1975.

10. Patent No. RU 48294. Device for superfinishing bombed rollers.

Claims (3)

A method of forming rollers with a convex generatrix, in which the processed rollers are placed on transport rollers or on the surface of the leading abrasive tool, the processed rollers are given a longitudinal feed per pass relative to the abrasive tool that performs the stock removal, characterized in that a gap is provided between the processed rollers at the ratio L ≤ , where L is the length of the roller being processed, - the length of the abrasive tool, while the size of the gap a is determined taking into account the required convexity value Δ _b using the relationship: , where t is the cutting depth.