Helical broach

Abstract

This helical broach forms a twisted groove at the inner periphery of a machined hole of a work by means of a plurality of cutting blades. The plurality of cutting blades have: a plurality of groove depth-expanding blades that are arrayed towards the tip of a broach body; and a plurality of groove width-expanding blades that are arrayed towards the base of the broach body. The plurality of groove width-expanding blades have a cutting blade and a guiding blade. The groove width-expanding blade positioned furthest towards the base of the broach body is formed with a guiding blade instead of a cutting blade at the edge of intersection of a scooping surface and the lateral surface that faces one of the wall surfaces from among both groove wall surfaces of the twisted groove of the work.

Description

technical field [0001] The present invention relates to a helical broach used for cutting a workpiece, for example, when manufacturing a helical internal gear having a helical groove on the inner periphery. [0002] this application claims priority based on Japanese Patent Application No. 2010-191074 for which it applied to Japan on August 27, 2010, and uses the content. Background technique [0003] An example of a helical internal gear is a planetary internal gear. Various planetary internal gears are offered as gears for automatic transmissions. However, with recent high-quality automatic transmissions, high-quality gears are also required. [0004] Helical broaches are used in the machining of such helical internal gears. For example, the following Patent Document 1 proposes a helical broach in which a plurality of cutting teeth (cutting teeth) protruding toward the radially outer peripheral side of the broach main body extend from the outer peripheral portion of the ...

AI Technical Summary

Problems solved by technology

[0007] However, in the final stage of processing, when the helical broach is pulled out from the workpiece, the number of final teeth acting on the workpiece on the circumference of the rear end side of the broach body changes, so the action of the helical broach on the workpiece become unstable

As a result, the workpiece is overcut by finishing the final tooth, and the accuracy of the tooth line deteriorates.

[0008] In particular, in a non-standard type helical broach in which adjacent cutting teeth are arranged obliquely with respect to the axis of the broach main body, when the helical broach in the final stage of processing is pulled out from the workpiece, the final teeth arranged along the circumference The teeth are extracted sequentially rather than simultaneously, so the above problems are more pronounced

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