Design method for cutter output length of variable-pressure-angle hob

Abstract

The invention relates to a gear machining process, in particular to a design method for the output length of a variable-pressure-angle hob, and mainly solves the technical problem that the output length of the hob cannot be accurately controlled in an existing method. The method comprises the following steps that 1, according to the generating machining principle, the circumferential length needed by a variable pressure angle hob for hobbing a complete tooth width of a to-be-machined gear is calculated; (2) based on the circumferential length obtained in the step (1), in combination with the helix angle of the variable-pressure-angle hob and the helix angle of the gear to be machined, the axial length of the variable-pressure-angle hob for hobbing a complete tooth width is obtained through calculation; and (3) according to the axial length obtained through calculation in the step (2), in combination with the axial feed amount during hobbing, the cutter output length of the variable-pressure-angle hobbing cutter during hobbing is obtained through calculation. On the basis of the method, the cutter output length of the variable-pressure-angle hob can be accurately controlled, the risk of machining interference of the variable-pressure-angle hob is fundamentally avoided, and then high-precision machining of the gear is achieved.

Description

Technical Field

[0001] The invention relates to a gear processing technology, and in particular to a method for designing the cutting length of a variable pressure angle hob. Background Art

[0002] In the gear hobbing process of certain shaft gears and duplex gears with stepped structures, a common method is to roughly simulate the gear hobbing cutout through two-dimensional drawing based on experience during the gear structure interference verification and tool design stages, and then use this as the basis for structural adjustment and hob outer diameter selection. However, in the simulation results of hobbing helical gears obtained by this method, the need for the machine tool headstock to rotate a large axis angle is ignored, resulting in large processing errors. Therefore, if the gear hobbing cutout length is not accurately considered during the design stage, there is often a risk of machining interference (i.e., the gear tooth groove cannot be hobbed in place on one side because the hob cannot fully cut in the tooth width direction).

[0003] With the increasing complexity of gear structures and the widespread use of helical gears, variable pressure angle hobs are now widely used. When machining helical gears with long ring gears, a hob with a larger outer diameter is required to meet gear machining accuracy and ensure the overall strength of the hob. However, judging from the workpiece structure, there is a risk of interference with the larger ring gear when machining the long ring gear, resulting in significant machining errors.

[0004] Chinese patent publication number CN110039123A discloses a method for machining inverted tapered gears using a variable pressure angle hob. This method calculates the standard root taper angle from the inverted tapered gear pressure angle, then determines the pressure angle of the root taper after the variable pressure angle. The root taper angle after the variable pressure angle is then calculated. Finally, the machine tool axis motion path is adjusted on the gear hobbing machine based on the root taper angle after the variable pressure angle, enabling the inverted tapered gear machining using a variable pressure angle hob. This method can reduce machining errors, but it still cannot precisely control the hob's cutter length, and therefore cannot fundamentally solve the interference problem associated with variable pressure angle hob machining. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the existing method cannot accurately control the cutting length of the hob cutter, and to provide a design method for the cutting length of the hob cutter with a variable pressure angle.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for designing the cutting length of a variable pressure angle hob cutter is characterized in that it includes the following steps:

[0008] Step [1], based on the principle of generating processing, calculate the circumferential length required for the variable pressure angle hob to cut a complete tooth width of the gear to be processed;

[0009] Step [2]: Based on the circumferential length obtained in step [1], combined with the helix angle of the variable pressure angle hob and the helix angle of the gear to be processed, calculate the axial length of the variable pressure angle hob for cutting a complete tooth width;

[0010] Step [3]: Based on the axial length calculated in step [2] and the axial feed amount during gear hobbing, the length of the tool exit during the variable pressure angle hob cutting is calculated, thereby completing the design of the length of the tool exit during the variable pressure angle hob cutting.

[0011] Furthermore, step [1] is specifically as follows: according to the principle of unfolding processing, combined with the tooth top height h of the variable pressure angle hob a0 , the helix angle β of the gear to be processed ′ and the normal pressure angle α of the gear to be machined ′ n , calculate the circumferential length L required for the variable pressure angle hob to cut a complete tooth width of the gear to be processed t ;

[0012] The circumferential length L t The calculation formula is:

[0013]

[0014] Furthermore, in step [2], the variable pressure angle hob cuts the axial length L of a complete tooth width. ′ x Calculated by the following formula:

[0015] L ′ x =L t ×tan|β ′ -λ0|

[0016] Among them, λ0 is the helix angle of the variable pressure angle hob.

[0017] Furthermore, in step [3], the length of the cutter during the variable pressure angle cutting is L x Calculated as follows:

[0018]

[0019] Where f is the axial feed during gear hobbing.

[0020] Furthermore, step [1] is specifically to calculate the circumferential length required for the variable pressure angle hob to roll a complete tooth width of a shaft gear or a duplex gear with a step structure based on the principle of generating processing.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention provides a method for designing the run-out length of a variable pressure angle hob. First, based on the principles of gear hobbing, the circumferential length required for the variable pressure angle hob to cut a complete tooth width of the gear being machined is calculated. Next, based on this calculation, the axial length required for the variable pressure angle hob to cut a complete tooth width is calculated, combining the helix angle of the variable pressure angle hob and the helix angle of the gear being machined. Finally, the run-out length of the variable pressure angle hob during cutting is calculated, combining the axial feed rate of the hob. This method allows for precise control of the run-out length of the variable pressure angle hob, fundamentally avoiding the risk of interference with the variable pressure angle hob during machining and enabling high-precision gear machining.

[0023] 2. The method for designing the cutting length of a variable pressure angle hob provided by the present invention can be applied to shaft gears or duplex gears with a stepped structure, as well as to ordinary spur and helical teeth, and has a wide range of applications.

[0024] 3. The present invention provides a method for designing the length of a variable pressure angle hob cutter, which has a convenient and quick calculation process and provides a strong theoretical basis for the overall design of the gear processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural schematic diagram of a variable pressure angle hob cutting a gear to be machined in an embodiment of a method for designing the cutting length of a variable pressure angle hob according to the present invention.

[0026] Figure 2 This is a schematic structural diagram of the engagement between a variable pressure angle hob and a gear to be machined in an embodiment of a method for designing the cutting length of a variable pressure angle hob according to the present invention. DETAILED DESCRIPTION

[0027] To make the purpose, advantages and features of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that the embodiments of the present invention are only used to explain the technical principles of the present invention, and are not used to limit the scope of protection of the present invention.

[0028] Combine Figure 1 and Figure 2 As shown, this embodiment provides a method for designing the length of a variable pressure angle hob cutter, comprising the following steps:

[0029] Step [1]: Based on the principle of generating, calculate the circumferential length required for the variable pressure angle hob to cut a complete tooth width of the gear to be machined.

[0030] In this embodiment, the gear to be processed can be a shaft gear or a duplex gear with a step structure, or a gear of other structural types; at the same time, the tooth shape of the gear to be processed can be straight teeth or helical teeth.

[0031] In addition, the design method of the design parameters of the variable pressure angle hob itself is the same as the conventional design method. This embodiment only specifically describes how to determine the specific tool length during gear processing after the variable pressure angle hob is designed.

[0032] Step [1] is specifically, based on the principle of generating processing, combined with the tooth top height h of the variable pressure angle hob a0 , the helix angle β of the gear to be processed ′ and the normal pressure angle α of the gear to be machined ′ n , the circumferential length L required for the variable pressure angle hob to cut a complete tooth width of the gear to be processed is obtained by calculation t .

[0033] Circumferential length L t The calculation formula is:

[0034]

[0035] Step [2]: Based on the circumferential length required for the variable pressure angle hob to roll a complete tooth width of the gear to be processed obtained in step [1], and then combined with the helix angle of the variable pressure angle hob and the helix angle of the gear to be processed, the axial length required for the variable pressure angle hob to roll a complete tooth width is calculated.

[0036] The axial length L of a complete tooth width cut by a variable pressure angle hob ′ x Calculated by the following formula:

[0037] L ′ x =L t ×tan|β ′ -λ0|

[0038] Among them, λ0 is the helix angle of the variable pressure angle hob, β ′ is the helix angle of the gear to be machined.

[0039] Step [3]: Based on the axial length of the variable pressure angle hob for cutting a complete tooth width calculated in step [2], combined with the axial feed rate during gear hobbing, the length of the tool exit when the variable pressure angle hob is cutting is calculated, thereby completing the design of the tool exit length of the variable pressure angle hob.

[0040] The length of the cutter during rolling cutting with the variable pressure angle cutter L x Calculated as follows:

[0041]

[0042] Where f is the axial feed during gear hobbing.

[0043] The present invention is based on the principle of gear hobbing engagement, and comprehensively considers the parameter design of the gear to be processed and the variable pressure angle hob. First, according to the gear hobbing principle, the hobbing process is converted into the gear rack movement process of the gear end face, thereby obtaining the circumferential length requirement required for the hobbing gear end face tooth profile.

[0044] Secondly, based on the helix angle of the variable pressure angle hob, the axial cutter length required for the hob to cut a complete tooth width is calculated.

[0045] Finally, to ensure the effective tooth width of gear hobbing, the machine tool error is comprehensively considered, and the axial feed of gear hobbing is added to the theoretical result to obtain the variable pressure angle cut length that matches the tooth shape of the gear to be machined, thereby achieving precise gear machining.

[0046] The present invention combines the current widespread use of variable pressure angle hobs and proposes a method for designing the cutting length of variable pressure angle hobs. This method can be used as a reference for structural verification in the product design stage, and can also be used as a reference for selecting parameters such as the hob outer diameter and the number of heads in the tool (i.e., variable pressure angle hob) design stage.

[0047] This invention combines analysis of the gear hobbing principle with the calculation of the hob cutter's lead-out length based on gear parameters, variable pressure angle hob parameters, and the axial feed rate of the hobbing process. This result can be applied to the three-dimensional interference simulation process of gear hobbing during the variable pressure angle hob design phase to determine the appropriate interference distance and variable pressure angle hob parameters. Furthermore, during the hobbing programming phase, the minimum lead-out length can be used to determine the axial displacement of the machine tool turret, thereby ensuring that the full tooth width is processed, saving machine tool debugging time and the total hobbing process time, thereby improving hobbing efficiency.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for designing the length of a variable pressure angle hob cutter, characterized in that: The following steps are involved: Step [1], according to the principle of generating processing, calculate the circumferential length required for the variable pressure angle hob to roll a complete tooth width of the gear to be processed; Step [2], based on the circumferential length obtained in step [1], combined with the helix angle of the variable pressure angle hob and the helix angle of the gear to be processed, calculate the axial length of a complete tooth width that the variable pressure angle hob cuts; Step [3], based on the axial length calculated in step [2], combined with the axial feed amount during gear hobbing, calculate the tool length of the variable pressure angle hob during hobbing, thereby completing the design of the tool length of the variable pressure angle hob.

2. The method for designing the length of a variable pressure angle hob according to claim 1, characterized in that: Step [1] is as follows: according to the principle of generating processing, the tooth top height h of the variable pressure angle hob is combined a0 , the helix angle β of the gear to be processed ′ and the normal pressure angle α of the gear to be processed ′ n , calculate the circumferential length L required for the variable pressure angle hob to cut a complete tooth width of the gear to be processed t ; The circumferential length L t The calculation formula is:

3. The method for designing the length of a variable pressure angle hob according to claim 2, characterized in that: In step [2], the variable pressure angle hob cuts the axial length L of a complete tooth width. ′ x Calculated by the following formula: L ′ x =L t ×tan|β ′ -λ0| Among them, λ0 is the helix angle of the variable pressure angle hob.

4. The method for designing the length of a variable pressure angle hob according to claim 3 is characterized in that: In step [3], the length of the blade during the rolling cutting of the variable pressure angle hob is L x Calculated by: Where f is the axial feed during gear hobbing.

5. The method for designing the length of a variable pressure angle hob according to claim 1, characterized in that: Step [1] specifically includes calculating, based on the principle of generating processing, the circumferential length required for a variable pressure angle hob to roll a complete tooth width of a shaft gear or a duplex gear with a step structure.

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