JP2007175814A - Helical broach for machining internal gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a helical broach for machining an internal gear, improving work helix form accuracy by eliminating deterioration of work helix form accuracy due to finishing of acute-angled tooth flank side of a former half part when the former half of a cutting part of a tooth thickness rise shell finish-cuts a work taking an obtuse-angled tooth flank as a guide using an acute-angled finishing edge, and in the rear half, an obtuse-angled finishing edge finish-cuts the work taking an acute-angled tooth flank as a guide using an obtuse-angled finishing edge immediately after the acute-angled finish edge performs finish-cutting. <P>SOLUTION: When the front half 2a of the cutting part of the tooth thickness rise shell cuts a work using the acute-angled finishing blades T1 to T8 and the rear half 3c' of the tooth thickness rise shell cuts the work using the obtuse-angled finishing edges T9 to T17, as shown in Fig. 3(a), an acute-angled start finishing blade T11 is disposed in a longer span than the work cut length (w) in the rear of the final acute-angled finishing edge T8, whereby the final acute-angled finishing edge T8 and the obtuse-angled cutting start finishing edge T11 are prevented from machining the work at the same time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an internal gear machining helical broach for machining a helical internal gear with a small tooth trace error, and more particularly to improvement of a broach cutting edge.

Patent Document 1 discloses a finish tooth of a shell having increased tooth thickness of a helical internal gear machining broach for machining a general helical internal gear having a structure in which a shell having increased tooth thickness disposed on a main body and a rear portion of a rough processed portion is assembled. The group is divided into three groups in the cutting direction. In the first half, the acute angle tooth surface is finish-cut with the obtuse angle side as the guide surface, and in the middle portion, the obtuse angle tooth surface is finish-cut with the acute angle side as the guide surface, and in the latter half the obtuse angle There is disclosed a technique in which an acute angle tooth surface is finished and cut again using the side as a guide surface.
Utility Model No. 2532834

  However, as shown in FIG. 1 (b), the configuration of the shell cutting pattern of Patent Document 1 is finished cutting with an acute-side finishing blade 2a with an obtuse-angle side tooth surface 2b as a guide in the front half, and an acute-side finishing blade in the intermediate portion. Immediately after finishing cutting, 2a was a shell cutting pattern in which the obtuse-side finishing blade 2d finished-cuts using the acute-side tooth surface 2c as a guide surface. For this reason, only the sharp-side finishing blade 2a is finish-cut in the first half, so that what has been cut in a stable state in the middle part is at the time of cutting the sharp-side finishing blade, which has the greatest effect on the sharpness on the sharp-angle side. The cutting of the obtuse angle side finishing blade was started. Specifically, as shown in FIG. 2 (b), the cutting of the obtuse-angle-side finishing blade T9 has already started on the inlet side of the workpiece in a state where the acute-angle-side finishing blade T7 is not completely removed from the workpiece. As a result, abnormal deformation and rotation of the workpiece during processing acted, and as a result, as shown in FIG. This phenomenon was particularly noticeable for workpieces with long cutting lengths. Further, in the cutting of the obtuse angle side finishing blade at the intermediate portion, the clearance angle θ3 is provided on the acute angle side tooth surface that is a guide, so that the cutting force at the time of obtuse angle finishing blade cutting reduces the sharp tooth surface to the work tooth streak. There was a problem that biting occurred, and as a result, the work tooth trace accuracy of the acute angle tooth surface was deteriorated.

  In view of the problems described above, the problem of the present invention is that the first half of the cutting part of the shell with increased tooth thickness is finished with an acute-side finishing blade with the obtuse-angle side tooth surface as a guide, and immediately after the acute-side finishing blade is finish-cut in the second half. When the obtuse side finishing blade is finished with the acute angle side tooth surface as the guide surface, the work tooth line accuracy caused by finishing the sharp angle side tooth surface in the latter half is not deteriorated and the work tooth line accuracy is improved. It is to provide a helical broach for gear machining.

  For this reason, the present invention is a helical broach for machining internal gears, in which the main part of the rough machining part and the tooth thickening shell arranged at the rear part are assembled, and the first half of the cutting part of the tooth thickening shell is an acute-side finishing blade When cutting with the obtuse angle side finishing blade in the latter half of the shell with increased tooth thickness, the obtuse side starting finishing blade is placed on the span longer than the workpiece cutting length behind the final acute angle side finishing blade position, The above problems have been solved by providing an internal gear machining helical broach characterized in that the sharp-angle-side finishing blade and the obtuse-angle-side cutting start finishing blade are not simultaneously machined.

  In the present invention, when the first half of the cutting part of the shell with increased tooth thickness is cut with an acute-side finishing blade and when the second half of the shell with increased tooth thickness is cut with the obtuse-side finishing blade, the workpiece is moved backward from the final acute-side finishing blade position. Placing the obtuse-side start finishing blade in a span longer than the cutting length so that the final acute-side finishing blade and obtuse-side cutting start finishing blade do not machine the workpiece at the same time, and the final acute-side finishing blade completely cuts the workpiece In order not to start the cutting of the obtuse angle tooth surface, the obtuse angle side cutting start blade is moved backward from the final sharp side finishing blade beyond the workpiece cutting length, so that It has become possible to provide a helical broach for internal gear machining that eliminates the deterioration of workpiece tooth trace accuracy caused by finishing and improves the workpiece tooth trace accuracy.

  Preferably, in the latter half of the shell, a positive clearance angle is not attached to the acute angle side guide tooth surface in the tooth thickness direction with respect to the cutting direction of the acute angle guide side tooth surface that is guided when cutting with the obtuse angle side finishing blade, or a negative clearance angle or It is a straight having the same angle as the spline torsion angle, and it has become possible to improve the guide property of the acute angle tooth surface that becomes the guide during obtuse angle side cutting, and to obtain a good workpiece tooth trace accuracy.

  Embodiments of the present invention will be described with reference to FIGS. FIG. 1A is an explanatory view schematically showing a shell cutting pattern of a helical broach for internal gear machining showing an embodiment of the present invention, and FIG. 1B is a general shell cutting pattern of a conventional product of Patent Document 1. FIG. 2 is an explanatory view schematically showing, FIG. 2 is a fragmentary sectional view showing a cutting state in the vicinity of the cutting length of the shell and the workpiece, and FIG. 3A is a cutting state in the vicinity of the cutting length of the workpiece in FIG. FIG. 3B is an enlarged view of a main part showing a cutting state in the vicinity of the cutting length of the workpiece of FIG. 1B, and FIG. 4A is an internal gear machining according to an embodiment of the present invention. FIG. 5B is an explanatory diagram showing the tooth streak accuracy of a work 1 tooth by a conventional helical broach for internal gear machining of Patent Document 1; FIG.

  As shown in FIG. 1 (a), the internal gear machining helical broach according to the embodiment of the present invention has a configuration in which a main body of a rough machining portion (not shown) and a tooth thickness increasing shell arranged at the rear portion are assembled. When the first half 2a of the cutting part of the shell with increased tooth thickness is cut with the acute-side finishing blades T1 to T8, and the second half 2c 'of the shell with increased tooth thickness is cut with the finishing edge T9 to T17 with the obtuse angle side, as shown in FIG. As shown in the drawing, the obtuse angle side finishing blade T11 and the obtuse angle side finishing start blade T11 are arranged in a span longer than the workpiece cutting length w from the final acute angle side finishing blade T8 position. At the same time, the workpiece is not machined.

  In the embodiment of the present invention, when the first half of the cutting portion of the tooth thickening shell is cut with an acute-side finishing blade, and when the second half of the tooth thickening shell is cut with the obtuse-side finishing blade, the final acute-side finishing blade position An obtuse-side start finishing blade is placed in a span longer than the workpiece cutting length from the rear to prevent the final acute-side finishing blade and obtuse-side cutting start finishing blade from machining the workpiece at the same time, and the final acute-side finishing blade is the workpiece In order not to start the cutting of the obtuse angle tooth surface until the cutting is completely completed, the obtuse angle side cutting start blade is moved backward from the final sharp side finishing blade beyond the workpiece cutting length, so the acute angle in the second half It has become possible to provide a helical broach for machining internal gears that eliminates the deterioration of the workpiece tooth trace accuracy resulting from the finishing of the side tooth surfaces and improves the workpiece tooth trace accuracy.

  As shown in FIG. 1 (b), which is a schematic diagram illustrating a typical shell cutting pattern of a conventional product of Patent Document 1, the conventional product has a clearance angle with respect to the cutting direction in the front half portion 2a of the shell. Amount of ΔT in the tooth thickness direction only on one side of the acute angle side from the acute angle side cutting start blade T1 to the final acute angle side finishing blade T8 using the obtuse angle side tooth surface 2b as a guide (generally, the ΔT amount gradually decreases as approaching the finishing blade) To cut. At this time, θ1 represents the clearance angle of the acute side cutting edge 2a. Next, from the obtuse angle side cutting start blade T9 to the obtuse angle side cutting edge T9 with the acute angle side guide portion 2c minus 5 to 20 μm in the same dimension or tooth thickness direction from the acute angle side finishing blade 2a provided in the first half, the obtuse angle side finishing blade # 17 Only the obtuse angle side is cut in the same manner as the acute angle side. At this time, the clearance angle of the acute angle side guide portion 2c is θ3, and the clearance angle of the obtuse angle side cutting blade 2d is θ2. The problem with this shell cutting pattern is that the obtuse angle cutting edge and the obtuse angle side cutting edge are cut immediately by the obtuse angle cutting start blade T9 provided after the acute angle finishing edge T8. In the switching portion (between T8 and T9), as shown in FIG. 3 (b), the acute angle side finishing blade T8 and the obtuse angle side cutting start blade T9 are temporarily cut simultaneously. This phenomenon extends to the obtuse angle tooth cutting blades T10 and T11 as the workpiece cutting length increases. Normally, the finishing blade T8 with an acute angle tooth surface has a cutting amount of 0 or very small. Therefore, the workpiece rotates due to the cutting resistance (back pressure) of the obtuse angle cutting start blade T9, and the force that bites into the acute angle tooth surface of the workpiece is Will work. Part (A) of FIG. 4 (b) is data of a tooth streak error generated by the bite on the acute angle side tooth surface.

FIG. 1 (a) shows an outline of the cutting pattern of the shell according to the present invention, and FIG. 3 (a) shows a state at the time of switching between the final acute-side finishing blade T8 and the obtuse-angle cutting start finishing blade T11. . In the present invention, the configuration of the acute angle cutting edge provided in the front half of the shell blade is the same as that of the conventional product, but the obtuse angle cutting start blade T11 is set to be longer than the cutting length w of the workpiece from the final acute angle side finishing blade T8 position. Move to the rear and set so that the final sharp side finishing blade T8 and the obtuse angle cutting start blade T11 do not cut simultaneously.
For example, if the workpiece cutting length w is 20 mm and the broach pitch P is 12 mm,
20mm / 12mm = 1.666 The number of simultaneous cutting blades is 2 blades.
Therefore, if the final acute-side finishing blade is T8 as shown in FIG. 3A, the obtuse-angle cutting start blade is normally T9, but in the present invention, it is moved backward by two blades and is T11. Thereby, as shown by the shell cutting pattern of the present invention in FIG. 3A, the cutting edges T9 and T10 of the obtuse angle side finishing blade do not cut both the acute angle side and the obtuse angle side. The finishing blade guides the T8 until it completely cuts the workpiece.

  In addition, as shown in Fig. 3 (b) of the conventional product, the increase in tooth thickness due to the conventional shell is positive in the sharp angle side tooth surface with respect to the cutting direction, but the rake angle in the tooth thickness direction is positive. The blunt angle side tooth surface is negative with respect to the cutting direction. Therefore, in the conventional product, the obtuse angle side tooth surface has a large back load of the cutting load during cutting, and there is a risk that the acute angle side tooth surface guide portion that should not be cut originally bites into the workpiece. In the present invention, this obtuse angle side tooth surface is cut with an obtuse angle side finishing blade at the latter half of the shell so that the acute angle side tooth surface guide portion does not bite even when back pressure during cutting is applied during cutting. It is stable because it does not have a positive clearance angle in the tooth thickness direction with respect to the cutting direction of the acute angle guide side tooth surface, which is sometimes guided, and is a straight with the same angle as the negative clearance angle or spline helix angle. Cutting state is possible.

  Although the present invention has been described in the form of an off-normal blade groove shell, it is needless to say that the present invention can also be applied to a shaft perpendicular groove and a normal blade groove shell.

(A) is explanatory drawing which represented typically the shell cutting pattern of the helical broach for internal gear processing which shows embodiment of this invention, (b) is a typical shell cutting pattern of the conventional product of patent document 1 typically. It is explanatory drawing represented to. It is a principal part fragmentary sectional view which shows the cutting state of the cutting length vicinity of a shell and a workpiece | work. FIG. 3A is an enlarged view of a main part showing a cutting state in the vicinity of the cutting length of the workpiece in FIG. 1A, and FIG. 3B is a main part showing a cutting state in the vicinity of the cutting length of the work in FIG. Partial enlarged view. (A) is explanatory drawing which shows the streak accuracy of 1 tooth | gear of the workpiece | work by the internal gear processing helical broach of embodiment of this invention, (b) is the workpiece | work 1 tooth by the helical broach for internal gear processing of the conventional product of patent document 1. FIG. It is explanatory drawing which shows the tooth trace accuracy.

Explanation of symbols

2a: First half of cutting part of shell with increased tooth thickness, 2c ': Second half part of shell with increased tooth thickness,
T1 to T8: acute angle side finishing blade, T8: final acute angle side finishing blade, T9 to T17: obtuse angle side finishing blade
T11: Finishing edge for obtuse angle cutting, w: Work cutting length

Claims (2)

  This is a helical broach for internal gear machining, in which the main body of the rough machined part and the tooth thickening shell arranged at the rear part are assembled. The first half of the cutting part of the tooth thickening shell is cut with an acute-side finishing blade, and the tooth When cutting with the obtuse angle side finishing blade in the latter half of the thick shell, place the obtuse side starting finishing blade in the span longer than the workpiece cutting length behind the final acute angle side finishing blade position, A helical broach for internal gear machining, characterized in that the obtuse angle side cutting start finishing blade does not simultaneously machine the workpiece.   In the latter half of the shell, a negative clearance angle or a spline twist angle is applied to the acute angle guide tooth surface in the tooth thickness direction with respect to the cutting direction of the acute angle guide side tooth surface that is guided when cutting with the obtuse angle side finishing blade. A helical broach for machining internal gears according to claim 1, characterized in that the guide property of the acute angle tooth surface which is a straight having the same angle as that of the straight angle and becomes the guide during obtuse angle side cutting is improved.

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