JPH0214900Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

The present invention relates to a helical broach for cutting helical internal gears or helical involute spline grooves.

[Prior art]

Cutting tools for machining twisted internal gears include:
Helical pinion cutters are well known, but there are also helical involute spline shafts, which are mainly used for helical internal gears installed on the outer ring of planetary reduction units used in automobile transmissions, or for power transmission means. Because it is impossible to machine the helical involute spline grooves and the like that fit into the helical pinion cutter due to the dimensions and shapes of the component parts, a helical broach is usually employed. This type of helical brooch can be found in the "Tool Encyclopedia" (published by Seibundo Shinkosha).
As shown in Figure 8.7 on page 272, each cutting edge of the spline blade is arranged along the required helix angle, but generally speaking, the handle is aligned as shown in the partially omitted schematic diagram in Figure 2. Following the section 11, a guide section P, a rough blade group R, and a finishing blade group F are provided, and a support section 12 is provided at the rear end. As shown in FIG. 3, the rough blade group R has a cutting mechanism in which the required tooth profile of the internal teeth is driven in the tooth height direction H to the prepared hole 14 of the workpiece 13, and the tooth height to be formed is sequentially adjusted. A gradually increasing number of spline blades 15 are provided, and the finishing blade group F is used to finish cutting the tooth profile cut by the rough blade group R into a desired regular tooth profile. The spline blades 15 and round blades 16 whose outer diameters are gradually increased in order to cut only the top portions T of the teeth are provided alternately in the axial direction. It goes without saying that each of the spline blades 15 is arranged along a required helix angle α, but the cutting edges of each spline blade 15 are formed on both left and right sides, and both cutting edges 17 and 18 are used for cutting at the same time. It is common to be involved. In addition, 19 is a chip plume provided between each blade.

[Problem that the invention attempts to solve]

By the way, in the conventional helical broach having the above configuration, the guide part P of the broach C is inserted into the pilot hole 14 of the workpiece 13, as shown in the cross-sectional view in FIG. C is used by relatively rotating and lowering the blade C. However, when both cutting edges 17 and 18 of each spline blade 15 are involved in cutting at the same time as described above, each cutting edge 17, A problem arises in that the chips discharged from the tips of the chips 18 collide with each other and interfere with each other, so that they do not fit into the chip plume 19 but protrude. In that case, chips may get caught between the cutting edge and the cutting surface, damaging the cutting surface, or may be welded to the cutting edge, causing problems such as deterioration of the finished surface accuracy and shape. Also,
Not only that, but the interference of the chips significantly accelerates the boundary wear of the cutting boundary surface at the tip of the cutting blade. As a means to solve this problem, a method is generally adopted in which the cutting edges involved in the cutting of each spline blade are formed on each side. FIG. 5 is an explanatory diagram schematically showing each cutting edge in each spline blade formed by this method. In the example shown in this figure, the spline blades 25 that are the first to seventh in the order of involvement in cutting are placed on the left acute angle side in the figure. A guide blade 22 (a blade with a cutting step of 0) that does not participate in cutting is formed in the obtuse-angled side part 24 on the right side of the guide blade 22 . On the other hand, in the 9th to 17th spline blades 26, a cutting edge 21 that participates in cutting is formed on the obtuse side side part 24, and a guide blade that does not participate in cutting is formed on the acute side side part 23. 22 is formed. Cutting with such spline blades 25 and 26 does not cause the interference of chips as described above. However, since the cutting is performed with a single edge, the cutting force acts biased to one side, and the spline blade involved in cutting is pressed toward the guide blade 22 side opposite to the cutting blade 21, which is the cutting side, and the guide blade 22 side Welding occurs. In extreme cases, the cutting edge 21 may be pushed out of balance due to being pushed from the cutting side, resulting in damage to the cutting edge 21. Furthermore, when welding occurs, the balance during cutting is lost and minute vibrations are generated, which accelerates the wear of the cutting blade 21 and the guide blade 22. The present invention has been devised in view of the above-mentioned problems and to effectively solve them. Therefore, the purpose is to provide a helical broach that can prevent welding on the guide blade side and damage to the cutting edge due to uneven cutting force during single-edged cutting, ensure tooth profile finish accuracy, and extend tool life. It's about doing.

[Means to solve the problem]

The helical broach according to the present invention has the following configuration in order to solve the problems of the prior art and achieve the purpose. That is, each spline blade of the finishing blade group arranged in a spiral configuration constitutes a first finishing blade group which is approximately the front half of the finishing blade group and a second finishing blade group which is approximately the rear half of the finishing blade group. There is. The spline blades of the first finishing blade group form a cutting edge having a cut step on either the acute side or the obtuse side, and have a cut step on the other same side. forms a guide blade with 0. Further, the spline blades of the second finishing blade group form cutting blades and guide blades on the opposite sides of the first finishing blade group.
Of these cutting edges, the side relief angle of the cutting edge formed on the obtuse side side portion is set to be larger than the side relief angle of the cutting edge formed on the acute side side portion. Further, the side clearance angle of the guide blade is set to be larger than 0° and smaller than the side clearance angle of the cutting blade on the acute side. The side clearance angle of the cutting blade is preferably 20′ or more and 1°, and the side clearance angle of the guide blade is preferably more than 0°,
In particular, it is preferably 20' or less.

[Effect]

The helical broach according to the present invention works as follows to solve the problems of the prior art and achieve the objectives. In other words, in the cutting by the cutting blades of the first finishing blade group and the cutting by the cutting blades of the second finishing blade group, the cutting edge on the obtuse side side, which normally has poor cutting performance, is By making the side relief angle larger than the side relief angle of the cutting edge on the acute side, the machinability is balanced and even cutting is performed. Regarding the side clearance angle of the guide blade, by giving this clearance angle, even if a force is applied toward the guide blade during cutting, the side surface will not come into contact with the surface to be cut to the extent that welding occurs (sticky contact). ). In addition, the cutting step of the guide blade is 0 and is not involved in cutting, but even if it is strongly pressed from the cutting edge side or a small amount of cutting step occurs due to manufacturing errors, this side surface will escape. This pressing force is released by performing micro-cutting to prevent welding. Moreover, even if such micro-cutting is performed, the depth of cut is extremely small, and the effect on the tooth profile error of the workpiece is negligible. If the side clearance angle of the cutting edge and the guide blade is too large, there is a risk of leaving traces of chatter vibration on the cut surface. Regarding the side clearance angle of the blade,
It is preferably greater than 0°, particularly less than 20'.

【Example】

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram schematically showing each cutting edge in each spline blade in an embodiment of the helical broach according to the present invention. As shown in the figure, in this embodiment, the spline blade 2 of the finishing blade group 1 is
There are 17 spline blades, and each of the first to seventh spline blades ₂₁ , which is roughly the first half, is
In the figure, a cutting edge 3 ₁ that has a cutting step and is involved in cutting is formed on the left acute side 5, and a guide blade 4 with a cutting step of 0 is formed on the right obtuse side 6.
₁ is formed to constitute a first finishing blade group ₁₁ .
On the other hand, each spline blade 2 ₂ from the 9th to the 17th spline blade, which is approximately the latter half of the finishing blade group 1, has a cutting step on the right obtuse side side 6 in the figure, and is a cutting blade that participates in cutting. 3 ₂ is formed, and a guide blade 4 ₂ with a cutting step of 0 is formed on the left acute side side portion 5 to constitute a second finishing blade group 1 ₂ . It should be noted that the eighth spline blade 2 ₃ has a guide blade 4 ₃ formed on both the acute-angle side portion 5 and the obtuse-angle side portion 6 thereof. A plurality of such spline blades 2 ₃ having only a guiding function may be provided before and after the spline blades 2 3 or may not be provided at all. In this example, θ ₁ in the figure is the first finishing blade group 1
₁ , _{and θ 2 is} the side relief angle of the cutting edge 3 ₂ of the second finishing blade group 1 ₂ . Further, θ ₃ is the side clearance angle of the guide blade 4 ₁ of the first finishing blade group 1 ₁ , and θ ₄ is the side clearance angle of the guide blade 4 ₂ of the second finishing blade group 1 ₂ . Between these side clearance angles, θ ₂ > θ ₁ > θ ₄ or θ ₃ > 0°, especially for θ ₂ and θ ₁ , 1° ≧θ ₂ > θ ₁ ≧20′ for θ ₄ and θ _3. The relationship 20′゜≧θ ₄ orθ ₃ >0゜ is satisfied.

[Effect of the idea]

As is clear from the above description, the present invention provides the following excellent effects. In other words, in single-edged cutting with a helical broach,
It prevents welding on the guide blade side and damage to the cutting edge due to uneven cutting force, ensures precision in tooth profile finishing, and extends tool life.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing each cutting edge of each spline blade in an embodiment of the helical broach according to the present invention, FIG. 2 is a partially omitted front view showing the schematic structure of the helical broach, and FIG. Figure 3 is an explanatory diagram of the cutting mechanism of the rough blade group, Figure 4 is a diagram of how the helical broach is used, and Figure 5 is a schematic diagram of each cutting edge in each spline blade formed by the conventional technique. It is an explanatory diagram. 1... Finishing blade group, 1 ₁ ... First finishing blade group, 1 ₂ ...
...Second finishing blade group, 2...Spline blade, 2 ₁ ...
Spline blade of the first finishing blade group, 2 ₂ ... Spline blade of the second finishing blade group, 3 ₁ ... Cutting edge of the spline blade of the first finishing blade group, 3 ₂ ... Spline blade of the second finishing blade group cutting edge, 4 ₁ ... guide blade of the spline blade of the first finishing blade group, 4 ₂ ... guide blade of the spline blade of the second finishing blade group, 5 ... acute side side part, 6 ... obtuse side side , θ ₁ ... Side relief angle of the cutting edge formed on the side part of the acute angle side, θ ₂ ... Side relief angle of the cutting edge formed on the side part of the obtuse angle side, θ ₃ , θ ₄ ... Each guide Side clearance angle of the blade.

Claims (1)

[Claims for Utility Model Registration] (1) The spline blades 2 of each strip of the finishing blade group 1 arranged in a spiral are generally referred to as a first finishing blade group 1, which is approximately the front half of the finishing blade group ₁ . The spline blade 2 1 of the first finishing blade group 1 1 constitutes the second finishing blade group 1 ₂ which is the latter half, and the spline blade _{2 1 of} the first finishing blade group 1 1 is
A cutting edge 3 1 having a cut step is formed on either the acute side 5 or the obtuse side 6, and a guide blade _{4 1 with} a cut step of 0 is formed on the other same side. The spline blade 2 ₂ of the second finishing blade group 1 ₂ is
A cutting blade 3 2 and a guide blade 4 ₂ are formed on the same side opposite to the first finishing blade group 1 ₁ , and a cutting edge 3 ₂ and a guide blade 4 2 are formed on the obtuse side side 6 of the cutting blades 3 ₁ and 3 ₂ . The side relief angle θ ₂ of the blade is set to the acute side 5
The side relief angle θ 3 and θ ₄ of the guide blades 4 ₁ and 4 ₂ are set larger than 0° and the side relief angle θ ₁ of the cutting edge formed on the acute side portion 5 is set larger than θ ₁ of the cutting edge formed on the acute side portion 5. A helical broach characterized by having a side relief angle θ smaller than ₁ . (2) The side clearance angles θ ₁ and θ ₂ of the cutting edges 3 ₁ and 3 ₂ are set in a range of 20′ or more and 1° or less, and the side clearance angles θ 3 and θ ₄ of the guide blades 4 ₁ and 4 ₂ are set in the range of 20′ or more and ₁ ° or less. The helical brooch according to claim 1 of the utility model registration claim, wherein the angle is set in a range of more than 0° and less than 20′.