Machining method of slender gears with large helical angle

Abstract

The present invention relates to a method for machining slender gears with large helix angles. By reducing the helix angle of the gear, the hob installation angle is also reduced, reducing the axial cutting force during gear hobbing. This is equivalent to increasing the rigidity of the workpiece, effectively ensuring the gear hobbing accuracy and surface quality. Since the hob installation angle is reduced, the height of the far end of the hob turret is increased, eliminating interference between the turret and the bottom of the machine tool and the oil pipe. At the same time, the hob can be properly shifted, increasing the service life of the hob and reducing the cost of gear hobbing. Before the implementation of the present invention, the original hobbing process required two feeds, taking about 50 minutes. Now, conventional gear hobbing only requires one feed, 12 minutes, and the hobbing is completed, which is at least 4 times more efficient. The present invention has been applied to the mass production process of differential planetary gears and can be widely promoted and applied within and outside the industry.

Description

Technical Field

[0001] The present invention relates to the technical field of gear processing, and in particular to a method for processing a slender gear with a large helical angle. Background Art

[0002] The planetary gear of a certain car differential has Mn=2.5, number of teeth Z=7, helix angle Bf1=±47.9167° (divided into left and right rotation, see the specific structure for details). Figure 1 ), the normal pressure angle afn1 = 30°, the displacement coefficient Xn = 0.0105, Da = 29.4, Di = 21.684, and the tooth width L = 93.5 (with a 30mm gap in the middle). When machining these slender gears with large helix angles, the hob head is typically angled significantly (greater than 45°), which can cause interference between the distal end of the hob head and the machine bottom and oil pipes.

[0003] Problems with existing technical methods:

[0004] 1. Commonly used CNC gear hobbing machines can generally only process gears with a helix angle within ±45°;

[0005] 2. The gear hobbing machine tool holder interferes with the bottom of the machine tool and the oil pipe;

[0006] 3. The hob cannot move and the tool life is short;

[0007] 4. The cutting force is large, the torque transmitted to the workpiece is unreliable, and the quality is unstable;

[0008] 5. Gear hobbing efficiency is low and processing cost is high.

[0009] The planetary gear can only be processed by a special gear hobbing machine, which is expensive and has high processing costs. Summary of the Invention

[0010] In order to solve the above problems, the present invention provides a method for machining slender gears with large helical angles, which can be used to machine gears with a helical angle greater than 45° on conventional machine tools.

[0011] The technical solution adopted by the present invention is: a method for processing a slender gear with a large helical angle, characterized in that it includes the following steps:

[0012] S1: Determine the basic parameters of the gear: normal module Mn1, number of teeth Z, normal pressure angle afn1, helix angle Bf1, normal arc tooth thickness Sfn1;

[0013] The pressure angle of the original circular end surface aft1=arctg(tg(afn1) / cos(Bf1))

[0014] Original circle diameter df1=Mn1 / cos(Bf1)*Z

[0015] Original base circle diameter d01 = Mn1 / cos(Bf1)*Z*cos(aft1) = d02

[0016] S2: Parameters converted to small helix angle Bf2:

[0017] According to gear lead = π*df1 / tg(Bf1) = π*df2 / tg(Bf2), we can get

[0018] New circle diameter df2 = df1 / tg(Bf1)*tg(Bf2)

[0019] New circular normal modulus Mn2=df2*cos(Bf2) / Z1

[0020] New circular end face pressure angle aft2 = arccos(d01 / df2)

[0021] invaft2=tg(aft2)-aft2

[0022] New circular normal pressure angle afn2=arctg(tg(aft2)*cos(Bf2))

[0023] New arc tooth thickness Sft2 = (Sft1 / df1+invaft1-invaft2)*df2

[0024] New circular normal arc tooth thickness Sfn2=Sft2*cos(Bf2)

[0025] New circular normal displacement coefficient Xn2 = (Sfn2-π*Mn2 / 2) / 2 / Mn2 / tg(afn2);

[0026] S3: Design a special hob: The hob helix angle Wf satisfies: Sin(Wf) = Mn2*Zn / dfg. Increasing the number of hob heads Zn and reducing the hob diameter dfg can increase the hob helix angle Wf, thereby further reducing the hob installation angle.

[0027] dfg=Mn2*Zn / Sin(Wf)

[0028] deg=dfg+2*(df2-Di) / 2, deg is the outer diameter of the hob.

[0029] Preferably, it is suitable for machining slender gears with a helix angle of 45° to 50°.

[0030] Preferably, Bf2 is less than 45°.

[0031] Preferably, Da=29.4, Di=21.684, Mn1=2.5, Z=7, Bf1=47.9167°, afn1=30°, Sfn1=3.957-(0.09+0.12) / 2=3.852,

[0032] Pressure angle of the original divided circle end face:

[0033] aft1=arctg(tg(afn1) / cos(Bf1))=40.74314°

[0034] invaft1=tg(aft1)-aft1=0.1503448

[0035] Original circle diameter: df1 = Mn1 / cos(Bf1)*Z = 2.5 / cos47.9167° = 26.1112 Original base circle diameter: d01 = Mn1 / cos(Bf1)*Z*cos(aft1) = 19.78298

[0036] New gear parameters after conversion to small helix angle:

[0037] Initial helix angle at the new dividing circle: Bf2 = 42.51737°

[0038] According to gear lead = π*df1 / tg(Bf1) = = π*df2 / tg(Bf2), we can get

[0039] New circle diameter: df2 = df1 / tg(Bf1) * tg(Bf2) = 21.61983

[0040] New circular normal modulus: Mn2=df2*cos(Bf2) / Z=2.27648

[0041] New circular end face pressure angle: aft2 = arccos (d01 / df2) = 23.78835°

[0042] invaft2=tg(aft2)-aft2=0.0256247

[0043] New circular normal pressure angle: afn2 = arctg (tg (aft2) * cos (Bf2)) = 18.00 degrees

[0044] New circular end face arc tooth thickness:

[0045] Sft2=(Sft1 / df1+invaft1-invaft2)*df2=7.638

[0046] New circular normal arc tooth thickness: Sfn2=Sft2*cos(Bf2)=5.6298

[0047] New circle normal modification coefficient:

[0048] Xn2=(Sfn2-π*Mn2 / 2) / 2 / Mn2 / tg(afn2)=1.3884;

[0049] Design a special hob: reduce the hob circle diameter dfg and increase the number of hob heads Zn;

[0050] dfg=Mn*Zn / Sin(Wf)

[0051] Since the number of gear teeth is too small Z = 7, the initial number of hob heads Zn = 1, the helix angle ωf = 2°,

[0052] deg=Mn*Zn / Sin(ωf)+(21.61983-21.684)=65.1, according to the standard, the hob diameter deg=70mm

[0053] dfg=deg-2*(df2-Di) / 2=70-(21.61983-21.684)=70.0642,

[0054] ωf=1°52′12″=1.87°;

[0055] Gear hobbing interference check:

[0056] The hob installation angle δ = β - ωf = 42.51737° - 1.87° = 40.64737°.

[0057] The beneficial effects achieved by the present invention are:

[0058] 1. It can effectively ensure product processing quality: by reducing the gear helix angle to 42.51737°, the hob installation angle is also reduced to 40.64737°, which reduces the axial cutting force during gear hobbing and increases the rigidity of the workpiece, effectively ensuring the gear hobbing accuracy and surface quality;

[0059] 2. Completely eliminates the risk of gear hobbing interference: Because the hob mounting angle is reduced by approximately 5.4°, the height of the hob holder at the far end is increased by 400*tan(5.4°)=38mm, eliminating interference between the holder and the machine bottom and oil pipes. This also allows the hob to shift appropriately, extending its service life and reducing gear hobbing costs.

[0060] 3. Significantly improves product processing efficiency: Before the implementation of this invention, hobbing a piece of gear required two passes and approximately 50 minutes. Now, conventional gear hobbing can be completed in just one pass, 12 minutes, a fourfold increase in efficiency. This time can be even shorter if a high-efficiency gear hobbing machine is used. This invention has already been applied to the mass production of differential planetary gears and is expected to be widely adopted within the industry and beyond. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1-2 It is a structural diagram of the gear to be processed; DETAILED DESCRIPTION

[0062] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0063] like Figure 1-2 The present invention provides a method for processing a large helical angle slender gear, comprising the following steps:

[0064] 1. First determine the gear parameters:

[0065] Given: gear tooth tip diameter Da, tooth root diameter Di, module Mn1, number of teeth Z, helix angle Bf1, normal arc tooth thickness Sfn1 (see Figure 1 and Figure 2 ).

[0066] Da=29.4, Di=21.684, Mn1=2.5, Z=7, Bf1=47.9167°, afn1=30°

[0067] Sfn1=3.957-(0.09+0.12) / 2=3.852

[0068] Pressure angle of the original divided circle end face:

[0069] aft1=arctg(tg(afn1) / cos(Bf1))=40.74314°

[0070] invaft1=tg(aft1)-aft1=0.1503448

[0071] Original sub-circle diameter: df1 = Mn1 / cos(Bf1)*Z = 2.5 / cos47.9167° = 26.1112 Original base circle diameter: d01 = Mn1 / cos(Bf1)*Z*cos(aft1) = 19.78298;

[0072] 2. New gear parameters after conversion to small helix angle

[0073] Initial helix angle at the new dividing circle: Bf2 = 42.51737°

[0074] According to gear lead = π*df1 / tg(Bf1) = = π*df2 / tg(Bf2), we can get

[0075] New circle diameter: df2 = df1 / tg(Bf1) * tg(Bf2) = 21.61983

[0076] New circular normal modulus: Mn2=df2*cos(Bf2) / Z=2.27648

[0077] New circular end face pressure angle: aft2 = arccos (d01 / df2) = 23.78835°

[0078] invaft2=tg(aft2)-aft2=0.0256247

[0079] New circular normal pressure angle: afn2 = arctg (tg (aft2) * cos (Bf2)) = 18.00 degrees

[0080] New circular end face arc tooth thickness:

[0081] Sft2=(Sft1 / df1+invaft1-invaft2)*df2=7.638

[0082] New circular normal arc tooth thickness Sfn2=Sft2*cos(Bf2)=5.6298

[0083] New circle normal modification coefficient:

[0084] Xn2=(Sfn2-π*Mn2 / 2) / 2 / Mn2 / tg(afn2)=1.3884

[0085] 3. Design a special hob (design the tool according to the new parameters)

[0086] Reduce the hob diameter dfg and increase the number of hob heads Zn;

[0087] dfg=Mn*Zn / Sin(Wf)

[0088] Since the number of gear teeth is too small Z = 7, the initial number of hob heads Zn = 1, and the helix angle ωf = 2°

[0089] Hob outer diameter deg = Mn*Zn / Sin(ωf)+(21.61983-21.684) = 65.1, according to the standard, the hob diameter deg = 70mm

[0090] dfg=deg-2*(df2-Di) / 2=70-(21.61983-21.684)=70.0642

[0091] ωf=1°52′12″=1.87°;

[0092] 4. Gear hobbing interference check:

[0093] Hob installation angle δ=β-ωf=42.51737°-1.87°=40.64737°

[0094] It should be noted that the description of the above technical solutions is illustrative only. This specification may be embodied in various forms and should not be construed as limiting the technical solutions set forth herein. Rather, these descriptions are provided to ensure that the disclosure of the present invention is thorough and complete and to fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of the present invention are limited only by the scope of the claims.

[0095] The shapes, sizes, ratios, angles, and numbers disclosed for describing various aspects of the present specification and claims are merely examples, and therefore, the present specification and claims are not limited to the details shown. In the following description, when a detailed description of a related known function or configuration is determined to be unnecessary to obscure the key points of the present specification and claims, the detailed description will be omitted.

[0096] When “including,” “having,” and “comprising” are used in this specification, unless otherwise used, there may also be another part or other parts, and the terms used may generally be singular but may also represent plural forms.

[0097] It should be noted that although the terms "first," "second," "top," "bottom," "one side," "the other side," "one end," "the other end," etc. may appear and be used in this specification to describe various components, these components and parts should not be limited by these terms. These terms are only used to distinguish one component or part from another. For example, without departing from the scope of this specification, a first component can be referred to as a second component, and similarly, a second component can be referred to as a first component. In certain circumstances, the components at the top and bottom can also be interchanged or switched with each other; the components at one end and the other end can have the same or different properties.

[0098] When describing positional relationships, for example, when the position sequence is described as "on," "above," "below," and "next," unless words or terms such as "just" or "directly" are used, situations where they are not in contact or in contact can also be included. If a first element is mentioned as being "on" a second element, it does not mean that the first element must be above the second element in the figure. The upper and lower parts of the components will change depending on the angle and orientation of observation. Therefore, in the drawings or in actual constructions, if it is mentioned that the first element is "on" a second element, it can include situations where the first element is "below" the second element as well as situations where the first element is "above" the second element. When describing temporal relationships, unless "just" or "directly" is used, situations where steps are not continuous can be included when describing "after," "subsequently," "followed," and "before." The features of the various embodiments of the present invention can be combined or spliced with each other in part or in whole, and can be implemented in various different configurations as can be fully understood by those skilled in the art. The embodiments of the present invention can be implemented independently of each other, or can be implemented together in a mutually dependent relationship.

[0099] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and is susceptible to numerous variations. Any simple modifications, equivalent variations, and modifications to the above embodiments based on the technical essence of the present invention shall be deemed to fall within the scope of protection of the present invention.

Claims

1. A method for machining a slender gear with a large helical angle, characterized by: Applicable to the processing of slender gears with a helix angle of 45° to 50°, including the following steps: S1: Determine the basic parameters of the gear: normal module Mn1, number of teeth Z, normal pressure angle afn1, helix angle Bf1, normal arc tooth thickness Sfn1; The pressure angle of the original circular end surface aft1=arctg(tg(afn1) / cos(Bf1)) invaft1=tg(aft1)-aft1 Original circle diameter df1=Mn1 / cos(Bf1)*Z Original base circle diameter d01 = Mn1 / cos(Bf1)*Z*cos(aft1) S2: Parameters converted to small helix angle Bf2: Bf2 is less than 45° According to gear lead = π*df1 / tg(Bf1) = π*df2 / tg(Bf2), we can get New circle diameter df2 = df1 / tg(Bf1)*tg(Bf2) New circular normal modulus Mn2=df2*cos(Bf2) / Z New circular end face pressure angle aft2 = arccos(d01 / df2) invaft2=tg(aft2)-aft2 New circular normal pressure angle afn2=arctg(tg(aft2)*cos(Bf2)) New arc tooth thickness Sft2 = (Sft1 / df1+invaft1-invaft2)*df2 New circular normal arc tooth thickness Sfn2=Sft2*cos(Bf2) New circular normal displacement coefficient Xn2 = (Sfn2-π*Mn2 / 2) / 2 / Mn2 / tg(afn2); S3: Design a special hob: The hob helix angle Wf satisfies: Sin(Wf) = Mn2*Zn / dfg. Increasing the number of hob heads Zn and reducing the hob circle diameter dfg can increase the hob Wf, thereby further reducing the hob installation angle. dfg=Mn2*Zn / Sin(Wf) deg=dfg+2*(df2-Di) / 2 Among them: deg is the outer diameter of the hob, Di is the root circle diameter.

2. The method for machining a large helical angle slender gear according to claim 1, characterized in that: Gear tooth tip diameter Da = 29.4, Di = 21.684, Mn1 = 2.5, Z = 7, Bf1 = 47.9167°, afn1 = 30°, Sfn1 = 3.957-(0.09+0.12) / 2 = 3.852, Pressure angle of the original divided circle end face: aft1=arctg(tg(afn1) / cos(Bf1))=40.74314° invaft1=tg(aft1)-aft1=0.1503448 Original circle diameter: df1 = Mn1 / cos(Bf1)*Z = 2.5 / cos47.9167° = 26.1112 Original base circle diameter: d01 = Mn1 / cos(Bf1)*Z*cos(aft1) = 19.78298 New gear parameters after conversion to small helix angle: Initial helix angle at the new dividing circle: Bf2 = 42.51737° According to gear lead = π*df1 / tg(Bf1) = = π*df2 / tg(Bf2), we can get New circle diameter: df2 = df1 / tg(Bf1) * tg(Bf2) = 21.61983 New circular normal modulus: Mn2=df2*cos(Bf2) / Z=2.27648 New circular end face pressure angle: aft2 = arccos (d01 / df2) = 23.78835° invaft2=tg(aft2)-aft2=0.0256247 New circular normal pressure angle: afn2 = arctg (tg (aft2) * cos (Bf2)) = 18.00 degrees New circular end face arc tooth thickness: Sft2=(Sft1 / df1+invaft1-invaft2)*df2=7.638 New circular normal arc tooth thickness: Sfn2=Sft2*cos(Bf2)=5.6298 New circle normal modification coefficient: Xn2=(Sfn2-π*Mn2 / 2) / 2 / Mn2 / tg(afn2)=1.3884; Design a special hob: reduce the hob circle diameter dfg and increase the number of hob heads Zn; dfg=Mn*Zn / Sin(Wf) Since the number of gear teeth is too small Z = 7, the initial number of hob heads Zn = 1, the helix angle ωf = 2°, deg=Mn*Zn / Sin(ωf)+(21.61983-21.684)=65.1, take deg=70mm dfg=deg-2*(df2-Di) / 2=70-(21.61983-21.684)=70.0642, ωf=1°52′12″=1.87°; Gear hobbing interference check: The hob installation angle δ = β - ωf = 42.51737° - 1.87° = 40.64737°.

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