A machining method for a tangential variable tooth thickness external gear

Abstract

The present invention belongs to the technical field of gear processing and relates to a method for machining a tangential variable tooth thickness external gear. First, the tooth part of the tangential variable tooth thickness external gear is rough machined by a gear shaping method, and then the finished tangential variable tooth thickness external gear is machined by form grinding. A gear shaper cutter with a tooth thickness smaller than the tooth slot width at the small end of the tangential variable tooth thickness external gear is used for rough machining the tooth part. First, the gear shaper cutter is used to machine the middle of the tooth slot of the tangential variable tooth thickness external gear in the way of machining a spur gear; then the gear shaper cutter is used to machine the left helical tooth surface and the right helical tooth surface in the way of machining a helical gear, leaving a grinding allowance for the tooth thickness. The form grinding process is to grind the left helical tooth surface and the right helical tooth surface first, and then grind the root circle of the tooth. The present invention uses the gear shaping method to rough machine the tooth part of the tangential variable tooth thickness external gear, and uses form grinding to finish machine the tooth surface and the root circle of the tooth. The gear shaping rough machining can reduce the machining allowance and has high efficiency. At the same time, the form grinding can improve the gear accuracy and can meet the requirements of mass production.

Description

Technical Field

[0001] The present invention belongs to the technical field of gear processing, and relates to a method for machining a tangentially variable tooth thickness external gear. Background Art

[0002] The structure of the tangentially variable tooth thickness external gear is as Figure 1 shown. This type of gear includes two modification coefficients, namely tangential modification Xt and radial modification Xh. At the same time, the addendum circle and dedendum circle of this type of gear do not change with the above-mentioned radial modification coefficient, and only the tooth thickness changes with the radial modification coefficient. The existing processing method for this type of variable tooth thickness external gear is to use a wire cutting machine, taking the large-end tooth thickness and small-end tooth thickness as processing parameters, and cutting the tooth part into shape by wire cutting. However, wire cutting has low efficiency and high cost, and is not suitable for mass production. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to solve the processing problem of variable tooth thickness external gears, and provide a method for machining a tangentially variable tooth thickness external gear.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A method for machining a tangentially variable tooth thickness external gear, first rough machining the tooth part of the tangentially variable tooth thickness external gear by hobbing, and then machining the finished tangentially variable tooth thickness external gear by form grinding.

[0006] Further, a hob with a tooth thickness smaller than the width of the tooth slot at the small end of the tangentially variable tooth thickness external gear is used for rough machining the tooth part. First, the hob is used to machine the middle of the tooth slot of the tangentially variable tooth thickness external gear in the way of hobbing a spur gear; then the hob is used to machine the left helical tooth surface and the right helical tooth surface in the way of hobbing a helical gear, and a grinding allowance is left for the tooth thickness.

[0007] Further, the process of form grinding is to grind the left helical tooth surface and the right helical tooth surface first, and then grind the dedendum circle.

[0008] Further, when hobbing and form grinding the left helical tooth surface and the right helical tooth surface, the spiral angle β is set as arctan[(S1 - S2) / (2 * tooth width)],

[0009] wherein, S1 is the large-end tooth thickness of the tangentially variable tooth thickness external gear; S2 is the small-end tooth thickness of the tangentially variable tooth thickness external gear.

[0010] Further, when hobbing, a margin of 0.1 mm is left for the tooth height, a margin of 0.5 mm is left for the large-end tooth thickness, and a margin of 0.5 mm is left for the small-end tooth thickness.

[0011] The beneficial effects of the present invention are as follows: The present invention uses the gear shaping method to rough machine the tooth part of the external gear with tangentially variable tooth thickness, and uses form grinding to finish machine the tooth surface and the root circle of the gear. The gear shaping rough machining can reduce the machining allowance and has high efficiency. At the same time, form grinding can improve the gear accuracy and can meet the requirements of mass production.

[0012] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. Brief Description of the Drawings

[0013] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, wherein:

[0014] Figure 1 is a schematic structural diagram of the external gear with tangentially variable tooth thickness in the present invention;

[0015] Figure 2 is a gear parameter diagram in an embodiment of the present invention;

[0016] Figure 3 is a diagram of the change of the tangential modification coefficient of the gear in the embodiment;

[0017] Figure 4 is a schematic diagram for calculating the helix angle β. Detailed Embodiments

[0018] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0019] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be understood as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0020] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be construed as a limitation of the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0021] A machining method for a tangential variable tooth thickness external gear is to first rough machine the tooth part of the tangential variable tooth thickness external gear by gear shaping, and then finish machine the finished tangential variable tooth thickness external gear by profile grinding.

[0022] Use a gear shaper cutter with a tooth thickness smaller than the tooth space width at the small end of the tangential variable tooth thickness external gear to rough machine the tooth part. First, use the gear shaper cutter to machine the middle of the tooth space of the tangential variable tooth thickness external gear in the way of machining a spur gear; then use the gear shaper cutter to machine the left helical tooth surface and the right helical tooth surface in the way of machining a helical gear, leaving a grinding allowance for the tooth thickness. The profile grinding process is to first grind the left helical tooth surface and the right helical tooth surface, and then grind the root circle.

[0023] Among them, when gear shaping and profile grinding are used to machine the left helical tooth surface and the right helical tooth surface, the set helix angle β = arctan[(S1 - S2) / (2 * tooth width)],

[0024] In the formula: S1 is the tooth thickness at the large end of the tangential variable tooth thickness external gear; S2 is the tooth thickness at the small end of the tangential variable tooth thickness external gear.

[0025] The tangential variable tooth thickness external gear machined in this embodiment is as Figure 1 shown, and its gear parameters are as Figure 2 、 3 shown. Its tangential modification coefficient X = -0.32257 to -0.47641, and according to Figure 2 it is given that M = 125.059 ± 0.03.

[0026] Since this type of gear includes two modification coefficients, tangential modification Xt and radial modification Xh, it can be deduced from the following formula:

[0027] 1. Δh = Xh × m = Δw / (2sinα),

[0028] 2. Δw = Xt × m,

[0029] 3. Substitute into the formula to obtain: Xt = 2Xh × sinα,

[0030] 4. Given \(X_t = (-0.47641)\sim(-0.32257)\), it is derived that \(X_h = (-0.69646)\sim(-0.471566)\).

[0031] 5. Finally, the tangential modification coefficient is converted into the radial modification coefficient.

[0032] The specific processing procedure includes the following implementation steps:

[0033] S1. Calculate the tooth space widths at the large and small ends of the tangential modified tooth thickness external gear, and obtain the normal tooth space width at the large end as 13.506 mm; the normal tooth space width at the small end as 12.441 mm.

[0034] S2. Calculate half of the difference between the tooth space width at the large end and the tooth space width at the small end, and compare this value with the tooth space width at the small end, taking the smaller value as the tooth thickness dimension of the gear shaper cutter.

[0035] S3. Calculate the helix angle \(\beta\), please refer to Figure 4 , where \(S1 = 7.979\) mm, \(S2 = 6.915\) mm, and the tooth width is 30 mm; it is calculated that \(\beta = 1.016^{\circ}\).

[0036] S4. Input the helix angle \(\beta\) into the CNC gear shaper, and cut the teeth in the way of cutting helical teeth to rough machine the straight tooth surface, the left tooth surface, and the right tooth surface in sequence, ensuring a tooth height allowance of 0.1 mm, a tooth thickness allowance of 0.5 mm at the large end, and a tooth thickness allowance of 0.5 mm at the small end.

[0037] S5. Input the helix angle \(\beta\) into the form grinding machine, and machine the finished product of the left tooth surface by form grinding and dressing, and ensure the finished tooth height;

[0038] S6. Machine the finished product of the right tooth surface by form grinding and dressing, and ensure the finished tooth height;

[0039] S7. Grind and dress the finished tooth height of the middle straight tooth part to complete the entire processing procedure.

[0040] 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 them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A machining method for a tangential variable tooth thickness external gear, characterized in that: First, rough machine the tooth part of the external gear with variable tooth thickness in the tangential direction by gear shaping, and then finish machine the finished external gear with variable tooth thickness in the tangential direction by form grinding; Use a gear shaper cutter with a tooth thickness smaller than the tooth space width at the small end of the external gear with variable tooth thickness in the tangential direction to rough machine the tooth part. First, machine the middle of the tooth space of the external gear with variable tooth thickness in the tangential direction by using the gear shaper cutter in the way of machining a spur gear; then machine the left helical tooth surface and the right helical tooth surface by using the gear shaper cutter in the way of machining a helical gear, leaving a grinding allowance for the tooth thickness; The process of form grinding is to grind the left helical tooth surface and the right helical tooth surface first, and then grind the root circle; When gear shaping and form grinding are used to machine the left helical tooth surface and the right helical tooth surface, the set helix angle β = arctan[(S1 - S2) / (2 * tooth width)], where S1 is the tooth thickness at the large end of the external gear with variable tooth thickness in the tangential direction; S2 is the tooth thickness at the small end of the external gear with variable tooth thickness in the tangential direction.

2. The machining method of the tangential variable tooth thickness external gear according to claim 1, characterized in that: When gear shaping, leave a margin of 0.1 mm for the tooth height, a margin of 0.5 mm for the tooth thickness at the large end, and a margin of 0.5 mm for the tooth thickness at the small end.

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