JP3978148B2 - Broach for helical internal gear machining - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a broach for helical internal gear machining having a helical blade groove in which a plurality of cutting blade grooves are provided in a screw shape around the axis of the broach with a spline twist angle β and a blade groove twist angle α.
[0002]
[Prior art]
As a conventional broach for processing helical internal gears, for example, as shown in FIG. 7 in Patent Document 1 (described as FIG. 4 in Patent Document 1), a predetermined spline in the longitudinal direction is formed on cylindrical blade portions 3 and 4 constituting the broach. A large number of blade rows 8 and 8a are formed toward the rear with a twist angle β, and a large number of blade grooves 7 (referred to as axial straight blade grooves) perpendicular to the axis (XX) of the broach are provided. And what formed many cutting blades 6 in each blade row 8 and 8a is known. In such a straight shaft groove broach, all the ring-shaped cutting blades 6 of the shaft straight blade groove start cutting at the same time during cutting, and the cutting is completed at the same time, so that intermittent cutting is performed, and pitch marks are added to the finished surface at regular intervals. The surface roughness becomes large. In order to avoid this, in 1 16A 00-08 of Non-Patent Document 1, “1.1.6 ^A .3. Other processing conditions and finished surface roughness” “(1) Unequal pitch and finished surface” In order to avoid the pitch mark, a broach combining a plurality of pitches, which is called an unequal pitch, is introduced without making the pitch of the cutting edge constant.
[0003]
However, in a broach of a shaft straight blade groove, because of intermittent cutting, it is inevitable that a so-called dog leg, pitch mark and surface roughness become large. Therefore, the helical internal gear shown in FIGS. The processing broach has helical blade grooves each having a spline twist angle β and a blade groove twist angle α of selected angles, and a plurality of cutting blade grooves provided in a screw shape around the axis of the broach. Since this broach has a spline twist angle β and a blade groove twist angle α of a selected angle, the cutting blades 6 (6a) of the respective strips arranged along the spline-shaped groove groove twist angle α at the time of cutting are Since each of them started cutting almost continuously and finished cutting almost continuously, it was avoided that so-called dog legs, pitch marks and surface roughness became large.
[0004]
[Patent Document 1]
Japanese Patent Publication No. 8-18181 FIG. 1, FIG. 2, FIG. 4, Claim 1
[Non-Patent Document 1]
"Machining Technology Data File" issued by Japan Institute of Mechanical Engineering
[0005]
[Problems to be solved by the invention]
However, the helical internal gear machining broach shown in FIG. 1 and FIG. 2 of Patent Document 1 was able to achieve a good effect, but the axial groove pitch is different between each line due to problems in manufacturing and regrinding. The pitch was equal. For this reason, the conventional broach for processing helical internal gears with an equal pitch has a so-called chatter when the cutting load is larger than the mechanical rigidity, that is, when machining a workpiece having a large diameter, a thin wall, and requiring a high load pulling force. The tooth trace error was increased, and a machined surface with good tooth trace accuracy could not be obtained.
The subject of the present invention is a helical internal gear machining broach that solves such a conventional problem, when the cutting load is large compared to the mechanical rigidity, that is, the workpiece having a large diameter, thin wall, and requiring a high load pulling force. It is an object of the present invention to provide a helical internal gear machining broach that does not generate so-called chatter and does not increase tooth trace errors and that can provide a machined surface with good tooth trace accuracy.
[0006]
[Means for solving the problems]
For this reason, the present invention has a helical blade groove in which a plurality of cutting blade grooves are provided in a screw shape around the axis of the broach with a spline helix angle β and a blade groove helix angle α. The above-described problem has been solved by a helical internal gear machining broach characterized in that it differs between the strips.
[0007]
【The invention's effect】
With this configuration, the axial groove groove pitch is varied between the respective strips, so that the cutting cycle of each cutting edge of the broach makes the workpiece discontinuous, and the cutting load is large compared to the mechanical rigidity, that is, a large Even when machining workpieces that have a large diameter and a thin, high-load extraction force, chatter does not occur during workpiece cutting, and high-precision tooth trace accuracy that does not increase tooth trace errors can be obtained. A broach for machining internal helical gears has been provided.
[0008]
Preferably, the axial groove pitch (P) between the strips is
0.66 L / N ≦ P ≦ 1.33 L / N
However, L: Axial blade groove leads, N: Multiple in the range of the number of threads, so that the extreme land width variation is not caused by each line in the state after regrinding the broach for helical internal gear machining. Thus, the guide property of the broach was not reduced.
[0009]
More preferably, the axial blade groove pitch (P) between the strips may be different for each strip (P, P ′, P ″, P ′ ″...), But at least 2 By using a broach with a combination of more than one type of axial groove pitch (P), high precision tooth trace accuracy without chattering and increasing tooth trace error during workpiece cutting. It can be obtained and is practical in the management of regrinding.
[0010]
Preferably, a plurality of cutting blade grooves having different axial blade groove pitches between the respective strips can be provided in the shell of the broach. In the broach shell, the blade thickness of each cutting edge of the broach increases sequentially according to the cutting direction. However, in the case of the conventional pitch groove groove broach, the cutting start / end of each blade of the broach is performed. Occasionally, when the cutting load is larger than the mechanical rigidity, that is, when machining a workpiece having a large diameter, a thin wall and a high load, a chatter is generated during workpiece cutting. Such an inconvenience could be eliminated by changing the pitch of the axial groove groove on the broach shell.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view of a workpiece and a schematic side view of a broach cutting blade during machining of a helical internal gear machining broach according to an embodiment of the present invention, and FIG. 2 shows a cutting method of each blade of the broach of FIG. (A) shows an enlarged view of the cutting method of each blade for rough cutting of the broach, each blade of the broach sequentially increases the blade height, that is, the outer diameter of the broach according to the cutting direction, (b) of FIG. FIG. 5 is an enlarged view showing a cutting method of each blade of the broach when each blade of the broach is applied to a shell part for finishing the broach, and the blade thickness of each blade of the broach increases sequentially according to the cutting direction. As shown in FIG. 1, the broach cutting blade 8 of the helical internal gear machining broach according to the embodiment of the present invention has multiple lines around the axis 10-10 of the broach with a spline twist angle β and a blade groove twist angle α. A helical blade groove 11 having a plurality of cutting blade grooves provided in a thread shape, and the axial blade groove pitch P is P, P ′, P ″, P ′ ″ that is different among the respective strips. This is a broach for processing a helical internal gear.
[0012]
With this configuration, the axial cutting groove pitch P is P, P ′, P ″, P ′ ″ that is different between the respective strips, so that each cutting edge 8 of the broach cuts the cycle of cutting the workpiece 1. When the cutting load is large compared to the machine rigidity, that is, when machining a workpiece with a large diameter, thin wall and a high load, there is no chatter during workpiece cutting, and tooth trace error Therefore, the present invention provides a helical internal gear machining broach capable of obtaining high precision tooth trace accuracy without increasing the torque.
FIG. 3 shows a broach having a helical blade groove in each rough cutting blade according to the embodiment of the present invention. As shown in FIG. 2 (a), each rough cutting blade of the broach has teeth sequentially according to the cutting direction. Graph showing the fluctuation in cutting load when the cutting force is large compared to the mechanical rigidity, that is, when machining a workpiece that requires a large diameter, thin wall, and a high pulling force. It is. FIG. 4 is a graph showing the fluctuation of the cutting load when the same workpiece as FIG. 3 is machined with a broach having a helical groove pitch of the shell part of the broach in the axial direction. It can be seen that chatter is occurring. According to FIGS. 3 and 4, when the cutting load is larger than the mechanical rigidity, the cutting load fluctuation generated in the conventional helical shell groove of the equal pitch shell does not occur according to the broach of the present invention, and the workpiece is being cut. Good results were obtained in which high precision tooth trace accuracy was obtained without chattering and without increasing tooth trace error.
[0013]
The axial groove pitch (P) between each strip is
0.66 L / N ≦ P ≦ 1.33 L / N
However, L: Axial blade groove leads, N: Multiple in the range of the number of threads, so that the extreme land width variation is not caused by each line in the state after regrinding the broach for helical internal gear machining. Thus, the guide property of the broach was not reduced.
[0014]
The axial groove pitch (P) between each strip may be different for each strip (P, P ′, P ″, P ′ ″...), But at least two types of axial directions By using a broach with a combination of blade groove pitch (P), a helical that does not cause chatter during workpiece cutting, and does not increase tooth trace error, and can provide high precision tooth trace precision. An internal gear machining broach was provided.
[0015]
Multiple cutting groove grooves with different axial cutting groove pitches between the respective grooves can be provided in the shell of the broach. In the broach shell, as shown in FIG. 2 (b), the blade thickness of each cutting edge of the broach sequentially increases in accordance with the cutting direction. However, the conventional axial pitch groove pitch P between each strip is equal pitch blade groove broach. Then, at the start and end of cutting of each blade of the broach, if the cutting load is larger than the mechanical rigidity, that is, even when machining a workpiece that has a large diameter, thin wall, and requires a heavy load, there is chatter during workpiece cutting. appear. Such an inconvenience can be eliminated by making the pitch of the axial groove groove in the shell of the broach different between the strips.
FIG. 5 shows an embodiment of the present invention in which a helical internal gear machining broach is used as a shell-shaped helical blade groove, and the cutting load is larger than the mechanical rigidity, that is, a large diameter, thin wall and The measurement result of the work tooth trace when processing a work that requires a high load pull-out force is shown. FIG. 6 shows the measurement results of the work tooth traces when the same workpiece is machined with a broach having a shell part helical blade groove of the broach having an equal axial groove pitch. According to FIGS. 5 and 6, tooth trace errors and waviness generated in the conventional helical shell groove of the equal pitch shell portion were suppressed by the broach of the present invention, and good results were obtained.
[Brief description of the drawings]
FIG. 1 shows a sectional view of a workpiece and a schematic side view of a broach cutting blade during machining of a broach for helical internal gear machining according to an embodiment of the present invention.
2 shows the cutting method of each blade of the broach of FIG. 1, (a) shows an enlarged view of the cutting method of each blade for rough cutting of the broach, and each blade of the broach sequentially increases the tooth height according to the cutting direction. That is, the outer diameter of the broach is increasing, and (b) is an enlarged view showing the cutting method of each blade of the broach when each blade of the broach of FIG. 1 is applied to the finishing shell portion of the broach. The tooth thickness of each blade increases in accordance with the cutting direction.
FIG. 3 shows a case where a broach having a helical blade groove according to an embodiment of the present invention is used and the cutting load is larger than the mechanical rigidity, that is, a workpiece having a large diameter, a thin wall and requiring a high load extraction force. It is a graph which shows cutting load fluctuation when processing.
4 is a graph showing fluctuations in cutting load when the same workpiece as in FIG. 3 is machined with a broach having a shell part helical blade groove of the broach having an equal axial groove groove pitch.
FIG. 5 shows a case where the broach for processing the helical internal gear according to the embodiment of the present invention is used for the helical blade groove of the shell, and the cutting load is large compared to the mechanical rigidity, that is, the large diameter and the thin wall. And the measurement result of a work tooth trace is shown when processing a work that requires a high load pull-out force.
6 shows a measurement result of a work tooth trace when the same workpiece as FIG. 5 is machined with a broach having a shell part helical blade groove of the broach having an equal axial groove groove pitch.
FIG. 7 is a perspective view of a main part of a conventional broach for machining a helical internal gear with a shaft straight blade groove.
[Explanation of symbols]
1 ··· Work 8 · · Broach cutting edge 10 · · · Broach axis 11 · · Helical blade groove α · · Spline twist angle β · · · Blade groove twist angle P, P ', P ", P"'... Axial groove pitch

Claims (4)

Spiral helix angle β and blade groove helix angle α have a helical blade groove with multiple threads in the form of threads around the axis of the broach, and the axial groove groove pitch is varied between the threads. A broach for processing helical internal gears. The axial groove pitch (P) between each of the above-mentioned strips is
0.66 L / N ≦ P ≦ 1.33 L / N
However, there are a plurality of L: axial blade groove leads, and N: a number within the range of the number of ridges. Whether the axial groove pitch (P) between the respective strips is different for each strip (P, P ′, P ″, P ′ ″...), Or at least two different axial blade grooves. The helical internal gear machining broach according to claim 1 or 2, characterized by having a combination of pitches (P). The helical internal gear according to any one of claims 1 to 3, wherein a plurality of cutting blade grooves having different axial blade groove pitches between the respective strips are provided in a shell of a broach. Brooch for processing.

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