CN115837492A

CN115837492A - Method for improving gear root enveloping precision in hob generating method machining

Info

Publication number: CN115837492A
Application number: CN202310067038.XA
Authority: CN
Inventors: 刘燕; 刘竺林; 宋世强; 杨超; 李一鑫
Original assignee: MIANYANG MIANGONG TOOLS CO Ltd
Current assignee: MIANYANG MIANGONG TOOLS CO Ltd
Priority date: 2023-01-13
Filing date: 2023-01-13
Publication date: 2023-03-24
Anticipated expiration: 2043-01-13
Also published as: CN115837492B

Abstract

The invention discloses a method for improving gear root enveloping precision in hob generating method machining, which comprises the following steps: s1, establishing a gear machining model of a gear hob before grinding through KISSsoft software; s2, finding out a position alpha at which the tooth root enveloping precision of the gear is greater than a design value; determining a tooth top arc position beta which is positioned on the gear hob before grinding and is used for processing the position alpha; s3, fitting the whole circular arc of the addendum circular arc at the position beta into a plurality of circular arc sections with different radiuses, and enabling any adjacent circular arc sections to be tangent to generate a new gear hob before grinding; s4, machining a gear by using the new gear hob before grinding produced in the step S3; by the means, the invention can ensure the enveloping precision of the gear tooth surface and improve the enveloping precision of the gear tooth root under the condition that the number of the effective cutting edges of the hob gear before grinding is not changed _。

Description

Method for improving gear root enveloping precision in hob generating method machining

Technical Field

The invention relates to the technical field of gear machining, in particular to a method for improving the gear root enveloping precision in a generating method machining process.

Background

A gear hob before grinding is used for generating method machining of gears, two design methods are available for the gear hob before grinding in the same industry at home and abroad at present, one method is to design a universal gear hob before grinding with common grinding allowance according to national standard gears, and the other method is to design the gear hob according to the required hobbing involute starting circle diameter, tooth root circle diameter, convex angle height and grinding allowance in the parameters of the gears to be machined.

The second method is a design method generally adopted at home and abroad, under the consideration of economic applicability, cost and other factors, the diameter of the pre-grinding gear hob designed by the method confirms the number of effective cutting edges (the number of circumferential edges) of a single disc cutter, and the number of the effective cutting edges is related to the tooth flank enveloping precision of the machined gear.

In view of the above, there is a need for a method for improving the tooth root enveloping accuracy of a gear during generating machining.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for improving the gear root enveloping precision in hob generating method machining.

In order to achieve the purpose, the invention adopts the following technical scheme:

the method for improving the gear root enveloping precision in hob generating method machining comprises the following steps:

s1, establishing a gear machining model of a gear hob before grinding through KISSsoft software;

s2, finding out a position alpha at which the tooth root enveloping precision of the gear is greater than a design value; determining a tooth top circular arc position beta which is positioned on the gear hob before grinding and is used for machining the position alpha;

s3, fitting the whole circular arc of the addendum circular arc at the position beta into a plurality of circular arc sections with different radiuses, and enabling any adjacent circular arc sections to be tangent to generate a new gear hob before grinding;

and S4, machining the gear by using the new gear hob before grinding produced in the step S3.

Preferably, in steps S1 to S3 of the above method, the number of circumferential edges on the pre-grinding gear hob is constant.

Compared with the prior art, the invention has the following beneficial effects:

in the invention, the addendum circular arc of a hob used for processing a cutting edge at the tooth root of a gear before grinding is changed, the addendum circular arc is divided into a plurality of circular arc sections with different radiuses, and any adjacent circular arc sections are tangent; by the aid of the method, the enveloping precision of the tooth surface of the gear can be guaranteed and the enveloping precision of the tooth root of the gear can be improved under the condition that the number of the effective cutting edges of the hob gear before grinding is not changed.

Drawings

FIG. 1 is a flow chart of a method for increasing gear root envelope accuracy in accordance with the present invention;

FIG. 2 is an envelope plot of the roots of a gear machined by a prior art set of pre-ground gear hobs;

FIG. 3 is a schematic diagram of a normal tooth profile of a gear hob before grinding in the prior art;

FIG. 4 is a schematic diagram of the normal tooth profile of a gear hob before grinding in an embodiment of the present invention;

FIG. 5 is an envelope of gear roots machined by a pre-ground gear hob in accordance with an embodiment of the present invention prior to fitting an addendum arc;

FIG. 6 is a schematic diagram of a normal tooth profile of a gear hob after fitting an addendum circular arc before grinding in an embodiment of the present invention;

FIG. 7 is an envelope plot of gear roots machined after fitting an addendum arc for a pre-ground gear hob in an embodiment of the present invention;

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

referring to FIG. 1, the present invention provides a method for increasing gear root envelope accuracy, comprising the steps of:

s2, finding out a position alpha at which the tooth root enveloping precision of the gear is greater than a design value; determining a tooth top arc position beta which is positioned on the gear hob before grinding and is used for processing the position alpha;

s3, fitting the whole circular arc of the tooth top circular arc at the position beta into a plurality of circular arc sections with different radiuses, and enabling any adjacent circular arc sections to be tangent to each other so as to generate a new gear hob before grinding;

The following will be specifically discussed in embodiments:

referring to fig. 2, in a group of gear hob before grinding in the prior art, the diameter of a cutter head is 320mm, the maximum effective cutting edges of each cutter head are 7 groups, and it is simulated by kissft software that the precision of an envelope pattern at a tooth root of a gear processed by the gear hob before grinding is 0.04mm-0.06 mm.

Referring to fig. 3, according to the generating method machining principle, different positions on the effective cutting edge correspond to different positions on the gear to be machined, the tooth root of the gear is machined by the tooth top arc part on the effective cutting edge in the gear hob before grinding, and in the prior art, the tooth top arc is generally composed of a full arc R.

Therefore, through simulation by the KISSsoft software, the tooth tip circular arc position β on the pre-grinding gear hob and used for machining the position α can be determined through the position α where the enveloping precision at the gear root is greater than the design value.

In one embodiment of the invention, a set of gear design parameters to be machined is taken as an example: the normal modulus is 22.5, the number of teeth is 30, the normal section pressure angle is 22.5 degrees, the helix angle on a pitch circle is 0 degree, the diameter of a tooth root circle is 629.604mm, the diameter of a tooth top circle is 737.21mm, the design precision grade meets 9 GB/T10095, the span number K =5, the common normal tolerance is 314.3152 +/-0.03 mm, the tooth grinding allowance (single face) is 0.34mm, the diameter of an involute initial circle is 654.624mm, the height of a convex angle is 0.85mm, the number of effective cutting edges (the number of circumferential edges) of each disc cutter is 7 groups, and the enveloping precision of the tooth root is less than or equal to 0.03mm.

And inputting the parameters into KISSsoft software to obtain a normal tooth profile schematic diagram of the gear hob before grinding shown in figure 4, wherein the unit of the parameter is mm.

Referring to fig. 5, after the gear is machined by the hob of the pre-ground gear shown in fig. 4 and simulated by the KISSsoft software, the precision of the obtained enveloping ring at the tooth root of the gear is 0.046mm-0.056mm, and the parameters of the enveloping ring are greater than the precision of the enveloping ring at the tooth root of the gear in the design requirement, so that the circular arc part of the tooth top on the effective cutting edge in the hob of the pre-ground gear needs to be improved and designed.

Referring to fig. 6, the addendum circular arc R on the effective cutting edge of the gear hob before grinding is divided into a plurality of groups of circular arc sections, and contour lines between adjacent circular arc sections are tangent, that is, the plurality of groups of circular arc sections are fitted to form a first section with a radius of 10mm, a second section with a radius of 12mm, a third section with a radius of 8.11mm, and a fourth section with a radius of 8 mm.

Referring to fig. 7, after the addendum circular arc R on the effective cutting edge in the gear hob before grinding is fitted, the gear hob before grinding is used for machining the gear, the obtained precision of the envelope pattern at the gear root of the gear is 0.015mm-0.018mm, the requirement of the precision of the envelope pattern at the gear root of the gear is met, and the envelope edge degree at the gear root of the gear is greatly reduced.

It should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations and positional relationships based on the orientations and positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, it should 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 meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The above examples are only used to illustrate the technical solutions of the present invention, and do not limit the scope of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from these embodiments without making any inventive step, fall within the scope of the present invention.

Claims

1. The method for improving the gear root enveloping precision in hob generating method machining is characterized by comprising the following steps of:

2. The method of claim 1 for improving gear root envelope accuracy in hob generating machining, wherein: in the steps S1 to S3, the number of circumferential edges on the gear hob before grinding is not changed.