CN117600568A - Method for accurately evaluating grinding quantity of tooth surface of shaft gear after heat treatment - Google Patents

Abstract

The invention discloses a method for accurately evaluating the grinding quantity of a tooth surface of a shaft gear after heat treatment, wherein the maximum grinding quantity and the minimum grinding quantity of j teeth on the section of the i-position of the shaft gear are calculated according to formulas (1) and (2):Wijmax=Wreservation +½Limaxcos(90-. Alpha. - θ) +c (1) andWijmin=Wreservation-½Limaxsin(θ - α) -c (2); wherein:Wthe reserved grinding quantity is reserved for the single side of the common normal line,Limaxfor the maximum radial runout, alpha is a pressure angle, theta is an included angle formed by j teeth on the section of the i position and the position of the radial maximum runout, and c is 0.05mm. The applicant adopts the deformation quantity which is the easiest to measure to calculate the grinding quantity of the tooth surface of the shaft gear after heat treatment, the method is simple and easy to grasp, and the semi-finished gear shaft with the grinding quantity which does not meet the requirement is removed before the tooth grinding process, so that the waste and defective rate is reduced.

Description

Method for accurately evaluating grinding quantity of tooth surface of shaft gear after heat treatment

Technical Field

The invention relates to processing of a shaft gear, in particular to a method for accurately evaluating the grinding quantity of a tooth surface of the shaft gear after heat treatment.

Background

Gear shafts are a common elongated piece made of metal material that integrates gears with shafts, on which gears (shaft gears) are used to mesh with the gears, transmitting motion and power.

The shaft gear is sequentially processed through the working procedures of rough machining, heat treatment (carburization, high temperature tempering after air cooling, quenching, low temperature tempering), finish machining and the like, and enters the final gear grinding working procedure, and if the gear surface is ground to the size required by the drawing, the gear surface is free of black skin, thus obtaining a finished product; if black skin remains on the tooth surface, it is a waste product.

The reason for the black skin on the tooth surface of the shaft gear after grinding is that the shaft gear is deformed after being processed by the working procedures such as machining, heat treatment and the like, and the factors causing the deformation generally have the following aspects: 1. the design aspect is as follows: the structural shape and design of the product are unreasonable; 2. the material aspect: due to chemical components, hardenability, grain size, inclusion segregation and other reasons of the material; 3. forging: the forging compactness, forging process, forging cooling, preliminary heat treatment and other reasons; 4. the mechanical processing aspect: the machining performance of the material, the quality of the cutter, sharpening, cutting specification, machining residual stress and the like; 5. carburizing: the quality of the clamp, the clamping mode, the carburizing process, the using equipment, the charging position and the like are unreasonably caused; 6. quenching: quenching equipment, a quenching process method, process parameters and other factors, and oil quality and oil temperature, stirring and other reasons.

Problems due to shaft gear deformation mainly include: 1. the tooth grinding time is increased, and the processing efficiency is reduced; 2. uneven grinding amount causes uneven depth of a hardening layer, so that the carrying capacity of a workpiece is reduced; 3. in the tooth grinding process, after grinding, the tooth surface still has black skin, so that the workpiece is scrapped, the product qualification rate is reduced, and the production cost of the gear shaft is increased.

Aiming at the deformation problem in heat treatment, different control measures are adopted in a plurality of countries, for example, standardization of a control production process is proposed in the last 70 th century in Japan, and the deformation amount of the gear after heat treatment is quantized, so that the quality of the gear is controlled; the us also proposes the assumption that the heat treatment distortion is zero and the heat treatment mass dispersion is zero in the beginning of this century; the Germany considers that the quenching deformation is the distortion potential accumulated in a series of operations of the whole processing process, and is considered from the aspects of people, machines, materials, methods and ring links; the concept of 'precise heat treatment' is put forward in the Chinese heat treatment and surface modification technology roadmap led by Zhao Zhenye institutions in China so as to control the deformation after heat treatment to be as small as possible; the Chinese heat treatment institute of science and technology Xu Yueming proposes a concept of "uniform heat treatment" to reduce the dispersion of deformation after heat treatment.

At present, although various measures for controlling the deformation of the shaft gear are adopted, and because of the structural difference between the shaft gear and the disc gear, unlike the deformation of the disc gear which is mainly the ovality and the end face runout of the gear, the deformation of the shaft gear is mainly bent along the axial direction, so that the method suitable for accurately evaluating the grinding amount of the tooth surface of the disc gear after heat treatment is not suitable for evaluating the shaft gear. If the tooth surface grinding quantity of the shaft gear can be accurately evaluated through simple measurement data after heat treatment, the shaft gear which cannot meet the tooth grinding quantity requirement is picked out in time and no subsequent tooth grinding treatment is performed, so that the yield of the gear shaft can be improved, and the processing cost of the gear shaft is effectively reduced.

Disclosure of Invention

The invention aims to provide a method for calculating the grinding amount of the tooth surface of a shaft gear after heat treatment, which is used for estimating the maximum and minimum grinding amount of the tooth surface of the shaft gear and the actual effective hardening depth of the tooth surface after grinding in advance, so that the yield and the working performance of the gear shaft can be improved, and the production cost of the gear shaft can be reduced.

In order to achieve the above purpose, the present invention may adopt the following technical scheme:

the method for accurately evaluating the grinding quantity of the tooth surface of the shaft gear after heat treatment comprises the following steps:

the maximum grinding amount and the minimum grinding amount of j teeth on the section of the shaft gear i are calculated according to the following formula:

Wijmax=Wreservation +½Limaxcos（90 - α - θ）＋c （1）

Wijmin=WReservation-½Limaxsin（θ - α）- c （2）

Wherein:

Wthe reserved grinding quantity is reserved for the single side of the common normal line during the hobbing,Limaxfor measuring the maximum radial runout quantity of the section of the shaft gear i, alpha is a pressure angle, theta is an included angle formed by j teeth on the section of the i and the position of the radial maximum runout quantity, c is a correction value of the influence of other changes on the grinding quantity, and 0.05mm is taken.

The invention has the advantages that:

the applicant adopts the deformation (maximum radial runout) which is the easiest to measure to calculate the grinding quantity of the tooth surface of the shaft gear after heat treatment, the method is simple and easy to grasp, and the semi-finished gear shaft with the grinding quantity which does not meet the grinding requirement is removed before entering the grinding process (can be remedied by adopting means of straightening and the like), so that the waste and defective rate is reduced, and the production cost of the gear shaft is reduced.

Drawings

FIG. 1 is a schematic diagram of the derivation of the formula of the present invention.

Fig. 2 is an enlarged view of a portion a in fig. 1.

Fig. 3 is a diagram of a shaft gear structure in example 1.

Fig. 4 is an enlarged cross-sectional view at the shaft gear i of fig. 3.

Fig. 5 is a photograph of a furnace gear shaft actually processed.

Detailed Description

The method of the present invention will be described in detail with reference to specific examples so as to facilitate understanding by those skilled in the art.

The method for calculating the grinding quantity of the tooth surface after the heat treatment of the shaft gear comprises the following steps:

the maximum grinding amount and the minimum grinding amount of j teeth on the section of the shaft gear i are calculated according to the following formula:

Wijmax=Wreservation +½Limaxcos（90 - α - θ）＋c （1）

Wijmin=WReservation-½Limaxsin（θ - α）- c （2）

Wherein:

Wthe reserved grinding quantity is reserved for the single side of the common normal line during the hobbing,Limaxfor measuring the maximum radial runout quantity of the section of the shaft gear i, alpha is a pressure angle, theta is an included angle formed by j teeth on the section of the i and the position of the radial maximum runout quantity, c is a correction value of the influence of other changes on the grinding quantity, and 0.05mm is taken.

The formula derivation is shown in figure 1 and figure 2.

Example 1:

as shown in fig. 3, the shaft gear is formed after the middle gear of the long shaft is hobbing, and the j tooth position distribution at the section i is as shown in fig. 3, j=0, 1, 2, 3, … …, 16.

After heat treatment, the maximum radial runout is measuredLimaxThe position is on tooth 0, then tooth 3 position θ=67.5 °.

Assuming that the reserved grinding amount of the common normal line is 0.6mm in the hobbing process, thenWReservation = 0.3mm; assuming that the pressure angle α is 20 °, the maximum grinding amount and the minimum grinding amount of the 3 rd tooth at the position i are respectively:

Wijmax=Wreservation +½Limaxcos（90 - α - θ）＋c = 0.3＋½Limaxcos（90 - 20 - 67.5）＋0.05。

Wijmin=WReservation-½Limaxsin（θ - α）- c= 0.3-½Limaxsin（67.5 - 20）-0.05。

For the shaft gear, as long as the maximum runout of a certain section of the shaft gear is measuredLimaxThe maximum grinding amount of the section can be calculatedWijmaxAnd minimum grinding amountWijminWhen the minimum grinding amountWijminWhen the deformation of the shaft gear is less than 0, the shaft gear is larger, and the shaft gear can enter the next processing procedure after being straightened.

Engineering case:

and (3) treating 10 gear shafts with the length of 2m and teeth at two ends in one furnace, finding out four points with the maximum deformation according to the deformation rule of the gear shafts, and measuring the maximum jumping quantity of the four points according to the data shown in the following table.

How to judge whether teeth at two ends of a shaft can be ground after carburizing and quenching is the pressure angle alpha=25°, the reserved grinding amount of common normal is 0.8 mm? What is the maximum grinding amount in the case of limit grinding?

The evaluation is carried out according to the method of the invention:

reserved grinding capacity of 0.8mm for common normal lineWReservation = 0.4mm;

while ensuring the minimum grinding amountWijminWhen the ratio is more than or equal to 0, the shaft gear can be ground out and substituted into the formula (2),

Wijmin=Wreservation-½Limaxsin(θ -. Alpha.) guaranteeLimax≤0.7/sin（θ - α），

Guarantee ofLimaxNo greater than 0.7mm, when θ - α=90°, i.e., θ=115°.

Therefore, when the maximum radial runout of the shaft gear is less than 0.7mm, black skin cannot appear in the grinding teeth.

When (when)WijmaxWhen the maximum value is 0.7, substituting the maximum value into the formula (1) to obtain the maximum grinding amount:

Wijmax=Wreservation +½Limaxcos（90 - α - θ）＋c=0.4＋[0.7cos（90°-α - θ）/2]＋0.05，

Maximum grinding amount when 90 ° - α - θ=0, i.e., θ=65°WijmaxThe maximum value of (2) is 0.8mm.

Therefore, the maximum grinding amount was 0.8mm when the polishing was limited.

Conclusion: the two shafts numbered 1 and 6 need to be aligned and then finish machined, and the rest 8 shaft gears can be directly finish machined.

Claims (1)

1. A method for accurately evaluating the grinding quantity of the tooth surface of a shaft gear after heat treatment is characterized by comprising the following steps of:

the maximum grinding amount and the minimum grinding amount of j teeth on the section of the shaft gear i are calculated according to the following formula:

Wijmax = Wreservation +½Limaxcos（90 - α - θ）＋c （1）

Wijmin = WReservation-½Limaxsin（θ - α）- c （2）

Wherein:

Wthe reserved grinding quantity is reserved for the single side of the common normal line during the hobbing,Limaxfor measuring the maximum radial runout quantity of the section of the shaft gear i, alpha is a pressure angle, theta is an included angle formed by j teeth on the section of the i and the position of the radial maximum runout quantity, c is a correction value of the influence of other changes on the grinding quantity, and 0.05mm is taken.