CN112524222B

CN112524222B - Bearing clearance adjusting method, gear box and prefabricated gasket

Info

Publication number: CN112524222B
Application number: CN202011365134.5A
Authority: CN
Inventors: 傅久定; 王文厚; 姜巨标; 轩宇; 尹荣栋
Original assignee: Nanjing Gaojing Track Traffic Equipment Co ltd
Current assignee: Nanjing Gaojing Track Traffic Equipment Co ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2022-01-04
Anticipated expiration: 2040-11-27
Also published as: CN112524222A

Abstract

The application provides a bearing play adjusting method, a gear box and a prefabricated gasket, and relates to the technical field of transmission, wherein the bearing play adjusting method comprises the following steps: a calculation step: establishing a size chain and calculating an adjusting ring; and (3) correcting: calculating the axial size variation l of the bearing to obtain a theoretical thickness range; an adjusting step: forming an adjustment member using a pre-fabricated shim, the pre-fabricated shim having a plurality of pre-fabricated thicknesses; defining a set of ranges comprising thickness values obtained from a combination of the preformed thicknesses; the set of ranges covers the theoretical thickness range of the adjustment member. The bearing clearance adjusting method takes the bearing fit deformation into account in the calculation of the axial clearance of the bearing of the subway gearbox axle, makes up the deviation between the calculation of the size chain of pure parts and the actual calculation, and provides a theoretical basis for practical application. By adopting the calculation method, more accurate adjustment range is obtained, and the range set is obtained by combining the prefabricated thicknesses, so that the assembly efficiency and reliability are improved, and the production and manufacturing cost is greatly reduced.

Description

Bearing clearance adjusting method, gear box and prefabricated gasket

Technical Field

The application relates to the field of rail transit gear boxes, in particular to a bearing clearance adjusting method, a gear box and a prefabricated gasket.

Background

The bearing is a key component of a gear box, such as a subway gear box, the service life of the bearing has important influence on the performance of the gear box, and the axial clearance of the bearing is an important technical parameter influencing the service life of the bearing and directly influencing the load distribution, vibration, noise, friction, temperature rise, service life and mechanical operation precision of the bearing.

Currently, the subway gearbox assembly mainly has 3 methods for adjusting the axial clearance of the bearing: the actual matching (commonly called matching grinding) adjustment and the adjustment are carried out by adopting a strippable gasket.

The actual-distribution adjusting method is a traditional adjusting method, is applied more in the development initial stage of the subway gearbox, carries out distribution grinding on an adjusting pad or a part according to the actually-measured size of assembly, realizes the control of the bearing clearance, has the adjusting precision subject to the precision of distribution grinding processing, has long distribution abrasion and low assembly efficiency, and is suitable for the subway gearbox assembled in a single set or in small batches.

The strippable gasket is formed by laminating and bonding precise metal foils, can be randomly stripped according to the size requirement in use, has high use cost and is suitable for the subway gearbox with high precision requirement.

Disclosure of Invention

A first object of the present application is to provide a bearing play adjustment method to achieve high assembly efficiency and low use cost.

A second object of the present application is to provide a gearbox obtained by the above bearing play adjustment method.

A third object of the present application is to provide a prefabricated gasket to achieve high assembly efficiency and low use cost.

In a first aspect, the present application provides a bearing play adjustment method for assembling a shaft system, the shaft system including:

a positioning surface;

a shaft member;

a bearing including an outer ring fitted with the positioning surface and an inner ring fitted with the shaft member;

a positioning member and an adjustment member, the adjustment member being positioned by the positioning member;

the bearing play adjusting method includes:

a calculation step: establishing a size chain, defining a ring of the adjusting component corresponding to the size chain as an adjusting ring, and calculating the range of the adjusting ring by using the difference value of the sum of the increasing rings and the sum of the decreasing rings;

and (3) correcting: calculating the axial dimension variation l caused by the matching of the outer ring and the inner ring of the bearing, and adding the axial dimension variation l to the range of the adjusting ring according to the number of the bearings to obtain a theoretical thickness range;

an adjusting step: forming the conditioning member using a pre-fabricated shim having a plurality of pre-fabricated thicknesses;

defining a set of ranges comprising thickness values obtained from the combination of the preformed thicknesses; the set of ranges covers a theoretical thickness range of the adjustment member.

The term "cover" as used herein means that the set of ranges includes the same thickness value as the lower limit value of the theoretical thickness range and the same thickness value as the upper limit value of the theoretical thickness range, and further includes a plurality of thickness values between the lower limit value and the upper limit value of the theoretical thickness range, which are all thickness values that may be required for the adjustment member to adjust the bearing play in the actual production process.

Therefore, by using the bearing play adjusting method, on one hand, the obtained theoretical thickness range is more accurate by taking the axial dimension variation l of the calculated bearing as a correction means for correcting a pure dimension chain calculation mode, and on the other hand, the theoretical thickness range is covered by the range set, so that the thickness of the adjusting component can meet the adjusting requirement of the theoretical thickness range in the actual production process.

Preferably, the adjusting step further comprises:

the set of ranges consists of the thickness values obtained after combining two of the pre-manufactured shims.

The combination of two pre-manufactured shims may be a combination of two pre-manufactured shims having the same pre-manufactured thickness, but may of course also be a combination of two pre-manufactured shims having different pre-manufactured thicknesses. Two pre-manufactured shims have a great advantage in terms of the number of used pre-manufactured shims, and a single pre-manufactured shim, when meeting the adjustment requirements of the same theoretical thickness range, will result in a larger pre-manufactured thickness and a larger specification of the pre-manufactured shims than a single pre-manufactured shim, while the risk that lubrication oil in the gearbox will leak between the pre-manufactured shims via the pre-manufactured shims is difficult to control than more pre-manufactured shims.

Preferably, the thickness values within the set of ranges form increments in predetermined increments.

With the range set formed in the above manner, the adjustment requirement of the bearing play can be sufficiently satisfied with a reduction in the number of required preform thicknesses, i.e., a reduction in the specification of the preform shim.

Preferably, at least some of the preformed thicknesses form increments in the predetermined increments.

Providing the preform thickness in the above manner enables a significant reduction in the specification of the preform sheet. For example, given a theoretical thickness range of Jmm-Kmm, with the predetermined increment being pmm, taking the upper limit value of the theoretical thickness range of Kmm as an example, and considering that the upper limit value of Kmm is obtained by stacking two prefabricated gaskets, one specification of the prefabricated gasket may be half of the upper limit value, namely 0.5Kmm (one prefabricated thickness is half of the upper limit value).

Then when the required bearing play adjustment thickness is (K-p) mm, by forming incremental (0.5K-p) mm-sized pre-fabricated shims in pmm with 0.5Kmm, this thickness value of (K-p) mm can be obtained by simply superimposing the gauge shims with the existing 0.5 Kmm-sized pre-fabricated shims. This greatly reduces the gauge of the pre-formed gasket required.

Preferably, the remaining preform thicknesses of the preform thicknesses except for the portion of the preform thickness that increases by the predetermined increment are formed to increase by an integer multiple of the predetermined increment.

By providing the preform thickness as above, the specification of the preform can be further reduced.

Preferably, the predetermined increment is 0.05 mm.

0.05mm is a preferred predetermined increment suitable for use in the field of gearboxes, in particular rail transit gearboxes, and furthermore, a predetermined increment of 0.05mm is provided, so that a complete value can be obtained during the assembly of the pre-shims, thus further reducing the pre-shims specification.

Preferably, the correcting step includes:

the locating surface and the outer ring form an interference fit, and the shaft member and the inner ring form an interference fit;

respectively calculating the expanded amount of the outer diameter of the inner ring serving as a containing piece and the reduced amount of the outer diameter of the outer ring serving as a contained piece by using GB/T5371-2004 interference fit calculation and selection;

subtracting the difference of the reduction amount from the expansion amount to obtain a variation Δ d of the diameter of the bearing;

the axial dimension change is calculated using i ═ Δ d/(2tan θ), where θ is the nominal contact angle of the bearing.

The above steps are equivalent to converting the obtaining process of the axial dimension variation l into the variation delta d of the diameter of the bearing, so that the axial dimension variation l can be more conveniently obtained by using the known parameter of the bearing, namely the nominal contact angle. GB/T5371-2004 interference fit's calculation and selection gives definite formula calculation mode to containing piece and by the containing piece, has further simplified the acquisition process of axial dimension variation l.

In a second aspect, the present application provides a gearbox obtained by assembling using the bearing play adjustment method as described above.

Preferably, the gearbox is formed as a rail transit gearbox.

In a second aspect, the present application provides a prefabricated shim for adjusting bearing play;

the pre-fabricated shim has a plurality of pre-fabricated thicknesses;

defining a set of ranges comprising thickness values obtained from the combination of the preformed thicknesses; the set of ranges comprises thickness values that meet requirements for adjusting the bearing play;

in particular, the thickness values within the set of ranges form increments in predetermined increments; in particular, at least part of said preformed thicknesses form increments in said predetermined increments; more particularly, where portions of the preform thickness are incremental in the predetermined increments: the prefabricated thicknesses except for the part of the prefabricated thickness which is increased by the preset increment are increased by integral multiple of the preset increment;

in particular, the predetermined increment is 0.05 mm.

According to the bearing clearance adjusting method provided by the embodiment, the bearing fit deformation is considered in the calculation of the axial clearance of the bearing of the subway gearbox axle, the deviation between the calculation of the pure part size chain and the actual part size chain is made up, and a theoretical basis is provided for practical application. By adopting the calculation method, the selection range of the more accurate adjusting component is obtained, the assembly efficiency and reliability are improved, and the manufacturing cost is greatly reduced.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 shows a schematic representation of a cross-sectional view of an axle system of a gearbox;

FIG. 2 is a schematic diagram of a chain of part sizes for the shafting arrangement of FIG. 1;

FIG. 3 shows a schematic diagram of the size chain of FIG. 2;

fig. 4 shows a schematic illustration of a partial view of the axle system structure.

Reference numerals:

1-a box body; 2-output gearwheel; 3-a bushing; 4-adjusting the spacer; 5-tapered roller bearings; 6-axle.

Detailed Description

The technical solutions of the present application will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present application.

The method for adjusting the bearing play provided in the present embodiment will be specifically described below with reference to fig. 1 to 4.

As shown in fig. 1, fig. 1 shows a cross-sectional view of a part of the structure of a gear box (i.e., a shafting structure), and a bearing play adjustment method will be specifically described below with the part of the structure shown in fig. 1 as a main example. Therefore, for the convenience of the following description, in the present embodiment, a partial structure of the gear box shown in fig. 1 will be explained first, and further, as an example, the gear box in fig. 1 may be formed as a subway gear box.

As shown in fig. 1, the housing 1 may be formed with a hole portion for accommodating the axle 6, and the axle 6 may be passed through the hole portion and supported in the hole portion by two bearings, which may be formed as tapered roller bearings 5, for example. As shown in fig. 1, as an example, the tapered roller bearings 5 are installed in a "face-to-face" manner (i.e., a manner in which the bearing fulcrums are close to each other), and the end surfaces of their inner rings close to each other are respectively positioned by both end surfaces in the axial direction of the output large gear 2, and it is apparent that the output large gear 2 is installed to the axle 6 and is located inside the housing 1. The outer sides of the two tapered roller bearings 5 are positioned by the bush 3, and taking the right tapered roller bearing 5 as an example, the cylindrical part of the bush 3 is inserted between the outer side part of the outer ring of the tapered roller bearing 5 and the box body 1 to position the tapered roller bearing 5 in the radial direction; the lower annular surface of the bush 3 abuts against the right-side end face of the outer ring of the tapered roller bearing 5 to position the right side of the tapered roller bearing 5 in the axial direction.

Similarly, the left-side tapered roller bearing 5 is similarly positioned by the other bush 3, the upper ring surface of which bush 3 abuts on the left-side end surface of the housing 1. With further reference to fig. 1, the bearing play can be adjusted in the manner given in fig. 1, i.e. by arranging an adjusting shim 4 between the upper annular surface of the right-hand bush 3 and the right-hand end face of the housing 1, by adjusting the thickness of the adjusting shim 4, the bearing play is adjusted.

In conjunction with fig. 2 and 3, fig. 2 shows a schematic representation of the cross-sectional view of fig. 1 with schematic dimensions indicated thereon, and fig. 3 shows a dimension chain of the current shafting arrangement on the basis of the schematic dimensions indicated in fig. 2. The thickness of the spacer shim 4 under the pure dimension chain is defined here as the basic dimension, so from fig. 3 it is clear that the basic dimension ═ Σ increasing loop- Σ decreasing loop, in which a1, A3 and a7 are decreasing loops, a2, a4, a5, a6 and A8 are increasing loops, the basic dimension being formed as the adjusting loop Δ. In one example, the basic dimensions, i.e., the design thickness range of the shim 4, are substituted for part dimensions and manufacturing tolerances in the manner of the calculations previously described.

As shown in fig. 4, fig. 4 shows a schematic view of one of the tapered roller bearings 5 of fig. 1 and 2 fitted with the axle 6. In the present embodiment, the fit between the inner ring of the tapered roller bearing 5 and the axle 6 and the fit between the outer ring of the tapered roller bearing 5 and the bush 3 (i.e., the above-described cylindrical portion of the bush 3) are both interference fits. Therefore, the present embodiment continues to consider the influence of the aforementioned interference fit on the amount of deformation of the tapered roller bearing 5 caused, specifically, on the width of the tapered roller bearing 5, on the basis of the basic dimensions obtained by the above calculation. For this reason, the present embodiment calculates the change in the width of the bearing according to the standard established in "calculation and selection of interference fit in GB/T5371-2004" (hereinafter referred to as standard), which will be described in detail in the following description.

In the embodiment, the tapered roller bearing 5, the bush 3, and the axle 6 are divided in "container" and "contained member" defined by the standard. Since the inner ring of the tapered roller bearing 5 and the axle 6 are in interference fit with each other, the inner ring of the tapered roller bearing 5 is divided into an accommodating member and the axle 6 is divided into an accommodated member with respect to the axle 6; similarly, since the bush 3 forms an interference fit with both the outer ring of the tapered roller bearing 5, the outer ring of the tapered roller bearing 5 is divided into an accommodated piece, and the bush 3 is divided into an accommodated piece. This is so:

reduction of inner diameter of the accommodated member:

amount of outer diameter expansion of the container:

wherein, in the above formula, E is the elastic modulus with the unit of N/mm²；p_fFor bonding pressure, in units of N/mm²；d_iIs the inside diameter of the accommodated part, d_aIs the outer diameter of the containing part; q is the diameter ratio; the subscripts "a", "i" denote the containing member and the contained member, respectively.

In this way, the reduction amount of the inner diameter of the outer ring of the tapered roller bearing 5 as the accommodated member and the expansion amount of the outer diameter of the inner ring of the tapered roller bearing 5 as the accommodated member are obtained by the above-described formulas, respectively. Δ d is the difference between the aforementioned expansion amount and reduction amount. Therefore, the width variation value l of the bearing can be calculated as follows:

l＝Δd/(2tanθ)

in the above formula, θ is a half cone angle of the tapered roller bearing 5, i.e., a nominal contact angle.

In the examples, the bonding pressure p is used_fThe range of (d) finally obtains the range of the difference Δ d between the amount of expansion and the amount of reduction, and further obtains the range of the width variation value l of the bearing. In the present embodiment, since the tapered roller bearing 5 is employed, Δ d is larger than 0, that is, the width of the tapered roller bearing 5 is increased. Based on the obtained range of the width variation value l of the bearing, values can be taken in the range, and the value is recorded as l₀. Two tapered roller bearings 5 are provided, and two tapered roller bearings l in total₀Superimposed on the above pure part dimension chain calculation, the theoretical thickness range is obtained, i.e. 2 times l₀Adding the lower limit value of the basic size to obtain the lower limit value of the theoretical thickness range, and multiplying l by 2 times₀The upper limit value of the theoretical thickness range is obtained by adding the upper limit value of the above basic size.

According to the above-described features, the theoretical thickness range has been determined by calculation, which is particularly advantageous for speeding up the assembly of the subway gearbox, i.e. improving the assembly efficiency.

For the convenience of the following description, the lower limit of the theoretical thickness range is defined as J and the upper limit is defined as K, and then the theoretical thickness range can be expressed as Jmm to Kmm, J is greater than 0 and K is greater than 0. On this basis, a plurality of specifications of prefabricated gaskets are prefabricated separately, which can be increased in thickness (the manner of increase will be described later in the description), and a range set is set that includes the obtained thickness values of the two prefabricated gaskets superimposed. The thickness of the shim 4 is a value in the range set, that is, the thickness of the shim 4 includes the thickness formed by combining two pre-fabricated shims of the same specification and the thickness formed by combining two pre-fabricated shims of different specifications.

The above range set covers Jmm to Kmm. Covering as used herein means that the above set of ranges includes thickness values equal to Jmm, and equal to Kmm, as well as thickness values between Jmm and Kmm, which are all thickness values that may be required by the adjustment member to adjust the bearing play during actual production. Therefore, in the bearing clearance adjustment process, the range set can fully meet the actual requirement of the bearing clearance adjustment, and the adjustment process is more efficient. In an embodiment, the thickness values within the set of ranges may be made to increase in predetermined increments, which is advantageous for reducing the gauge of the pre-fabricated shim, preferably 0.05 mm.

Further, it is preferable that the thickness of at least some of the plurality of sizes of prefabricated gaskets is increased in increments of 0.05mm (i.e., the above-mentioned predetermined increments), 0.05mm being a preferred predetermined increment suitable for use in the field of gear boxes, particularly rail transit gear boxes, and further, the predetermined increments of 0.05mm are provided so that the full value can be obtained during the combination of the prefabricated gaskets, thereby further reducing the sizes of the prefabricated gaskets.

In light of the above-described features, some examples in practical applications will be specifically described below in specific numerical values. In one example, the theoretical thickness range of 1mm to 1.8mm can be obtained by calculation using the bearing play adjustment method of the present embodiment. The preformed shims may then be of a size of 0.5mm, 0.55mm, 0.65mm, 0.75mm, 0.85mm and 0.9mm, and of these 6 preformed thicknesses, 0.5mm and 0.55mm form increments of 0.05mm, and 0.85mm and 0.9mm form increments of 0.05 mm. While 0.55mm, 0.65mm, 0.75mm and 0.85mm form increments of 0.1mm (double 0.05mm), that is, more preferably, the remaining gauges of the plurality of gauges of the preformed gasket other than the gauge according to the increments of 0.05mm may form increments of integer multiples of 0.05mm, which is advantageous for further reducing the gauge of the preformed gasket.

A thickness of 1mm can be obtained when two prefabricated shims of 0.5mm thickness are used, and similarly a thickness of 1.8mm can be obtained when two prefabricated shims of 0.9mm thickness are used, whereas between 1mm and 1.8mm, all thickness values increasing in 0.05mm increments, i.e. 1.05mm, 1.1mm … 1.75.75 mm, can be obtained by the combination of the two prefabricated shims, these thickness values together with 1mm and 1.8mm being the thickness values of all possible required adjustment shims 4 during the bearing play adjustment. This enables the present embodiment to meet the above-mentioned requirements of the range set covering the theoretical thickness range only with a few specifications of the pre-fabricated shims, that is, the obtained spacer shims 4 can always meet the adjustment requirements of the bearing play.

According to the bearing clearance adjusting method provided by the embodiment, the bearing interference fit deformation is considered in the calculation of the axial clearance of the bearing of the subway gearbox axle, the deviation between the calculation of the pure part size chain and the actual part size chain is made up, and a theoretical basis is provided for practical application. By adopting the calculation method, the selection range of the adjusting shim 4 is more accurately obtained, the assembly efficiency and reliability are improved, and the manufacturing cost is greatly reduced. The adjusting shim 4 is designed according to the range, the requirement of the theoretical thickness range is greatly met only by using prefabricated shims with fewer specifications, the machining amount of the prefabricated shims is reduced, and the assembling efficiency is improved.

The embodiment also provides a gearbox, such as a subway gearbox, which is obtained by assembling the bearing play adjusting method, and also comprises the beneficial effects, and the details are not repeated.

The present embodiment also provides a pre-fabricated shim for adjusting bearing play, the pre-fabricated shim having a plurality of pre-fabricated thicknesses. A set of ranges is defined, the set of preformed shims being arranged such that the set of ranges includes thickness values obtained by combining preformed thicknesses. Wherein the set of ranges comprises thickness values that meet the requirements for adjusting the bearing play.

In particular, the thickness values within the set of ranges form increments at predetermined increments, which allows the preform shim to have less preform thickness, facilitating adjustment while also saving cost. In particular, at least some of the preform thicknesses are formed in increments of predetermined increments, which further reduces the number of preform thicknesses.

More specifically, where portions of the preform thickness are incremental in predetermined increments: the remaining preform thicknesses except for the portion of the preform thickness that is increased by the predetermined increment are increased by an integral multiple of the predetermined increment, and further, the predetermined increment may be 0.05 mm. Thus, the number of prefabricated thicknesses is further reduced, adjustment is further facilitated, and cost is saved.

The above description is only a preferred embodiment of the present application, and not intended to limit the scope of the present application, and all changes that can be made in the details of the description and drawings, or directly/indirectly implemented in other related technical fields, are intended to be embraced therein without departing from the spirit of the present application.

Claims

1. A bearing play adjustment method for use in a shafting assembly, the shafting comprising:

a bushing formed with a positioning surface;

a shaft member;

an adjustment member positioned by the bushing;

the bearing play adjusting method is characterized by comprising the following steps:

defining a set of ranges comprising thickness values obtained from the combination of the preformed thicknesses; the range set covers a theoretical thickness range of the adjustment member;

the correcting step comprises the following steps:

calculating an amount of expansion of an outer diameter of the inner ring as a container and an amount of reduction of an inner diameter of the outer ring as a container, respectively;

wherein, with the bushing as an accommodating member and the outer ring as an accommodated member, a reduction amount of an inner diameter of the outer ring is calculated:

wherein, with the inner ring as an accommodating member and the shaft member as an accommodated member, an amount of expansion of the outer diameter of the inner ring is calculated:

wherein E is the elastic modulus; p is a radical of_fIs the bonding pressure; d_iIs the inner diameter of the member to be contained, d_aIs the outer diameter of the containing member; q is the diameter ratio; subscripts "a", "i" denote a containing member and a contained member, respectively;

2. The bearing play adjustment method according to claim 1, characterized in that the adjusting step further includes:

the set of ranges consists of thickness values obtained by combining one or both of the pre-shims.

3. Bearing play adjustment method according to claim 2, characterized in that the thickness values within the set of ranges form increments in predetermined increments.

4. The bearing play adjustment method according to claim 3,

at least some of the preform thicknesses form increments in the predetermined increments.

5. The bearing play adjustment method according to claim 4,

in the event that some of the preform thicknesses form increments in the predetermined increment:

the prefabricated thicknesses except for the part of the prefabricated thicknesses which are increased by the preset increment are increased by integral multiples of the preset increment.

6. The bearing play adjustment method according to claim 3, characterized in that the predetermined increment is 0.05 mm.

7. A gearbox, characterized in that it is assembled using the bearing play adjustment method as claimed in any one of claims 1 to 6.

8. Gearbox according to claim 7, formed as a rail transit gearbox.

9. A pre-fabricated shim, characterized in that it is obtained by the bearing play adjustment method of any one of claims 1 to 6 and is used for adjusting bearing play;

the pre-fabricated shim has a plurality of pre-fabricated thicknesses;

defining a set of ranges comprising thickness values obtained from the combination of the preformed thicknesses; the set of ranges includes thickness values that meet the requirements for adjusting the bearing play.

10. The pre-fabricated shim of claim 9,

the thickness values within the range set form increments in predetermined increments.

11. The pre-fabricated shim of claim 10,

12. The precast pad of claim 11,

in the event that some of the preform thicknesses form increments in the predetermined increment: the prefabricated thicknesses except for the part of the prefabricated thicknesses which are increased by the preset increment are increased by integral multiples of the preset increment.

13. The pre-fabricated shim of claim 10, wherein the predetermined increment is 0.05 mm.