A method for accurately evaluating the amount of grinding on the tooth surface of shaft gears after heat treatment

Abstract

The present invention discloses a method for accurately evaluating the grinding amount of the tooth surface of a shaft gear after heat treatment. The maximum grinding amount and the minimum grinding amount of the j tooth on the cross section at position i of the shaft gear are calculated according to formulas (1) and (2): Wijmax = W Reserved + ½Limaxcos (90‑α‑θ) + c (1) and Wijmin = W Reserved ½Limaxsin (θ‑α)‑c(2); where: W The reserved grinding amount is for the single side of the common normal line. Limax is the maximum radial runout, α is the pressure angle, θ is the angle between tooth j and the position of maximum radial runout on section i, and c is 0.05 mm. The applicant used deformation, which is easily measurable, to calculate the grinding amount of the axle gear tooth surface after heat treatment. This method is simple and easy to master. Semi-finished gear shafts that do not meet the grinding requirements are removed before the gear grinding process, reducing the scrap rate.

Description

Technical Field

[0001] The present invention relates to the machining of shaft gears, and in particular to a method for accurately evaluating the grinding amount of shaft gear tooth surfaces after heat treatment. Background Art

[0002] A gear shaft is a common long part made of metal material that integrates a gear and a shaft. The gear (shaft gear) on it is used to mesh with the gear to transmit motion and power.

[0003] The shaft gear undergoes rough machining - heat treatment (carburizing - high temperature tempering after air cooling - quenching - low temperature tempering) - fine machining and other processes in sequence, and enters the final gear grinding process. If there is no black skin on the tooth surface after grinding to the size required by the drawing, it is a finished product; if there is still black skin on the tooth surface, it is a waste product.

[0004] The reason why black skin appears on the tooth surface of the shaft gear after gear grinding is that the shaft gear is deformed after machining and heat treatment. The factors causing deformation are generally the following: 1. Design: unreasonable design of product structure and shape; 2. Material: chemical composition, hardenability, grain size, inclusion segregation and other reasons of the material; 3. Forging: forging density, forging process, forging cooling, pre-heat treatment and other reasons; 4. Machining: material processing performance, tool quality and grinding, cutting specifications, processing residual stress and other aspects; 5. Carburizing: unreasonable fixture quality, clamping method, carburizing process, equipment used, loading position, etc.; 6. Quenching: quenching equipment, quenching process methods and process parameters and other factors, as well as oil quality and oil temperature, whether there is stirring, etc.

[0005] The main problems caused by shaft gear deformation include: 1. Increased grinding time and reduced processing efficiency; 2. Uneven grinding volume, resulting in uneven hardened layer depth, which in turn reduces the workpiece's load-bearing capacity; 3. During the gear grinding process, after grinding to the required volume, black skin still exists on the tooth surface, causing the workpiece to be scrapped, reducing the product qualification rate, and increasing the production cost of the gear shaft.

[0006] In response to the deformation problem during heat treatment, many countries have adopted different control measures. For example, Japan proposed the standardization of production process control in the 1970s and quantified the distortion of gears after heat treatment in order to control the quality of gears. The United States also proposed the idea of ​​zero heat treatment distortion and zero dispersion of heat treatment quality at the beginning of this century. Germany believes that quenching deformation is the distortion potential accumulated in a series of operations in the entire processing process, and it should be considered comprehensively from the aspects of people, machines, materials, methods and environment. The concept of "precision heat treatment" was proposed in the China Heat Treatment and Surface Modification Technology Roadmap led by Academician Zhao Zhenye of my country to control the deformation after heat treatment as small as possible. Xu Yueming, chairman of the China Heat Treatment Society, proposed the concept of "consistent heat treatment" to reduce the dispersion of deformation after heat treatment.

[0007] Although various measures are currently in place to control shaft gear deformation, and due to the structural differences between shaft gears and disc gears, shaft gear deformation primarily involves axial bending, unlike disc gear deformation, which is primarily caused by gear ovality and end face runout. Therefore, methods suitable for accurately assessing the amount of tooth surface grinding after heat treatment for disc gears are not suitable for shaft gears. If the amount of tooth surface grinding of shaft gears could be accurately assessed using simple measurement data after heat treatment, and shaft gears that do not meet the grinding requirements could be promptly removed from subsequent grinding, the yield rate of gear shafts could be improved, effectively reducing the processing cost of gear shafts. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for calculating the tooth surface grinding amount of a shaft gear after heat treatment, so as to estimate in advance the maximum and minimum grinding amount of the shaft gear tooth surface and the actual effective hardened layer depth of the tooth surface after grinding, which can not only improve the yield and working performance of the gear shaft, but also reduce the production cost of the gear shaft.

[0009] To achieve the above purpose, the present invention can adopt the following technical solutions:

[0010] The method for accurately evaluating the amount of gear tooth surface grinding after heat treatment described in the present invention is:

[0011] The maximum grinding amount and minimum grinding amount of tooth j on the section i of the shaft gear are calculated according to the following formula:

[0012] Wijmax = W Reserved + ½Limaxcos (90 - α - θ) + c (1)

[0013] Wijmin = W Reserved- ½Limaxsin (θ - α) - c (2)

[0014] Where:

[0015] W The reserved grinding amount is for the single side of the normal line when gear hobbing. Limax is the maximum radial runout measured on the section at position i of the shaft gear, α is the pressure angle, θ is the angle between the j tooth and the position of the maximum radial runout on the section at position i, and c is the correction value for the influence of other changes on the wear, which is taken as 0.05mm.

[0016] The advantages of the present invention are:

[0017] The applicant used the most easily measurable deformation (maximum radial runout) to calculate the grinding amount of the shaft gear tooth surface after heat treatment. The method is simple and easy to master. Before entering the gear grinding process, the semi-finished gear shaft whose grinding amount does not meet the gear grinding requirements will be eliminated (correction can be made by straightening and other means), thereby reducing the scrap rate and lowering the production cost of the gear shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a simplified diagram of the derivation of the formula of the present invention.

[0019] Figure 2 yes Figure 1 Magnified view of part A.

[0020] Figure 3 This is the shaft gear structure diagram in Example 1.

[0021] Figure 4 yes Figure 3 Enlarged cross-section of shaft gear i.

[0022] Figure 5 This is a photo of the gear shaft of a furnace that was actually processed. DETAILED DESCRIPTION

[0023] The method of the present invention is described in detail below with reference to specific examples to facilitate understanding by those skilled in the art.

[0024] The calculation method of the tooth surface grinding amount after heat treatment of a shaft gear described in the present invention is:

[0025] The maximum grinding amount and minimum grinding amount of tooth j on the section i of the shaft gear are calculated according to the following formula:

[0026] Wijmax = W Reserved + ½Limaxcos (90 - α - θ) + c (1)

[0027] Wijmin = W Reserved- ½Limaxsin (θ - α) - c (2)

[0028] Where:

[0029] W The reserved grinding amount is for the single side of the normal line when gear hobbing. Limax is the maximum radial runout measured on the section at position i of the shaft gear, α is the pressure angle, θ is the angle between the j tooth and the position of the maximum radial runout on the section at position i, and c is the correction value for the influence of other changes on the wear, which is taken as 0.05mm.

[0030] The formula derivation is attached. Figure 1 、 Figure 2 .

[0031] Example 1:

[0032] like Figure 3 As shown, the shaft gear is formed after the gear is hobbed in the middle of the long shaft, and the position distribution of the j teeth at the section i is as follows Figure 3 As shown, j = 0, 1, 2, 3, …, 16.

[0033] After heat treatment, the maximum radial runout is measured. Limax The position is on the 0th tooth, so the 3rd tooth position θ = 67.5°.

[0034] Assuming that the reserved grinding allowance of the common normal line during gear hobbing is 0.6mm, then W Reserve = 0.3mm; Assuming the pressure angle α is 20°, the maximum and minimum grinding amounts of the third tooth at position i are:

[0035] Wijmax = W Reserved + ½Limaxcos (90 - α - θ) + c = 0.3 + ½Limaxcos (90 - 20 -67.5) + 0.05.

[0036] Wijmin = W Reserved- ½Limaxsin (θ - α)- c = 0.3- ½Limaxsin (67.5 - 20)-0.05.

[0037] For shaft gears, as long as the maximum runout of a certain section of the shaft gear is measured Limax , the maximum grinding amount of the section can be calculated Wijmax and minimum grinding amount Wijmin , when the minimum grinding amount Wijmin When it is less than 0, it means that the shaft gear is greatly deformed and needs to be straightened before entering the next processing step.

[0038] Project Cases:

[0039] One furnace processes 10 gear shafts with a length of 2m and teeth at both ends, such as Figure 4 According to the deformation law of the shaft gear, find the four points with the largest deformation and measure the maximum runout of the four points. The data are shown in the following table.

[0040]

[0041] The pressure angle α of the shaft gear is 25°, and the normal grinding allowance is 0.8mm. How can I determine whether the teeth on both ends of the shaft can be ground after carburizing and quenching? What is the maximum grinding allowance under the condition of extreme grinding?

[0042] Evaluation was performed according to the method of the present invention:

[0043] The normal line reserve grinding allowance is 0.8mm, then W Reserve = 0.4mm;

[0044] When ensuring the minimum grinding amount Wijmin When ≥0, the shaft gear can be ground out, and substituting it into formula (2),

[0045] Wijmin = W Reserved- ½Limaxsin (θ - α), ensuring Limax ≤0.7 / sin (θ - α),

[0046] ensure Limax Not greater than 0.7mm, at this time θ - α = 90°, that is, θ = 115°.

[0047] Therefore, when the maximum radial runout of the shaft gear is less than 0.7mm, no black skin will appear on the grinding gear.

[0048] when Wijmax When the maximum value is 0.7, the maximum grinding amount can be obtained by substituting it into formula (1):

[0049] Wijmax = W Reserved + ½Limaxcos (90 - α - θ) + c = 0.4 + [0.7 cos (90°-α-θ) / 2]+0.05,

[0050] When 90°-α - θ=0, that is, θ=65°, the maximum grinding amount Wijmax The maximum value is 0.8mm.

[0051] Therefore, when the limit is ground out, the maximum grinding amount is 0.8mm.

[0052] Conclusion: The two shafts No. 1 and 6 need to be straightened and then fine-machined, and the remaining 8 shaft gears can be directly fine-machined.

Claims

1. A method for accurately evaluating the amount of gear tooth surface grinding after heat treatment, characterized by: The maximum grinding amount and minimum grinding amount of tooth j on the section i of the shaft gear are calculated according to the following formula: Wijmax = W Reserved + ½Limaxcos (90 - α - θ) + c (1) Wijmin = W Reserved- ½Limaxsin (θ - α) - c (2) Where: W The reserved grinding amount is for the single side of the normal line when gear hobbing. Limax is the maximum radial runout measured on the section at position i of the shaft gear, α is the pressure angle, θ is the angle between the j tooth and the position of the maximum radial runout on the section at position i, and c is the correction value for the influence of other changes on the wear, which is taken as 0.05mm.

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