Hob cutter

Abstract

To provide a hob cutter capable of suppressing abnormal wear.SOLUTION: The hob cutter includes a cylindrical base body that rotates about a central axis, and a plurality of cutting edges 3 spirally arranged on an outer peripheral surface of the base body, wherein a cutting edge shape of one of two adjacent cutting edges of the cutting edge 3 has an asymmetrical shape in which a protuberance portion 5 having a large protrusion amount is provided on one side in a central axis direction, and a cutting edge shape of the other of the two adjacent cutting edges of the cutting edge 3 has an asymmetrical shape in which a protuberance portion 5 having a large protrusion amount is provided on the other side in the central axis direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hob cutter for cutting gears to be cut. [Background technology]

[0002] In conventional gear cutting techniques, a hob body is rotated around an axis, and multiple cutting edges are formed on the outer periphery of the body, along a spiral tooth trace, to cut the gear to be cut, thereby creating a tooth profile.

[0003] Patent Document 1 describes a hob cutter that can improve chip discharge during finish machining. Specifically, by making the tooth height of the hob during rough machining larger than that during finish machining, the chips are less likely to form a U-shape and become rod-shaped chips with the center of the U cut off, so the chips do not press against the tooth surface and are therefore better able to be discharged.

[0004] Furthermore, Patent Document 2 states that in a gear cutting tool using rolling, by increasing the amount of chamfering of the cutting edge of the hob on the follower side, it is possible to form a high-precision gear that is symmetrical after rolling. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-221598 [Patent Document 2] Japanese Unexamined Patent Publication No. 58-143916 Summary of the Invention [Problem to be solved by the invention]

[0006] The cutting edge of each hob in Patent Documents 1 and 2 has a protruding hump (hereinafter referred to as a protuberance portion) symmetrically formed on both ends in the axial direction. This is to ensure that the tooth root shape of the gear to be cut (hereinafter referred to as a work gear) will smoothly connect when cutting and grinding are completed. Furthermore, the tooth flank of the work gear has an involute curve in the cross section perpendicular to the tooth axis. The range of this involute curve (hereinafter referred to as an involute portion (flank portion)) can be widened by reducing the flank angle of the protuberance portion of the hob cutter, thereby ensuring the involute portion.

[0007] Reducing the flank angle of the protuberance portion means reducing the flank relief angle of the protuberance portion, which results in thin-cutting that increases the contact area during cutting. However, such thin-cutting can accelerate flank wear in the side relief portion of the cutting edge of the hob cutter. Furthermore, as crater wear on the rake face approaches the edge of the cutting edge of the hob cutter, the flank wear and crater wear can merge, rapidly accelerating abnormal wear.

[0008] The present invention has been made in view of the above technical problems, and has an object to provide a hob cutter that can suppress abnormal wear. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides a hob cutter comprising a cylindrical base body that rotates around a central axis and a plurality of cutting edges arranged in a spiral on the outer peripheral surface of the base body, wherein the cutting edge shape of one of two adjacent cutting edges of the cutting edges is asymmetrical with a protuberance portion that protrudes to a greater extent on one side in the direction of the central axis, and the cutting edge shape of the other of the two adjacent cutting edges of the cutting edges is asymmetrical with a protuberance portion that protrudes to a greater extent on the other side in the direction of the central axis. [Effects of the Invention]

[0010] The hob cutter of the present invention has a plurality of cutting edges, and the cutting edge shape of the cutting edges of the cutting edges is asymmetrical with a protuberance portion that protrudes to a greater extent on one side in the direction of the central axis, and the cutting edge shape of the other of two adjacent cutting edges of the cutting edges is also asymmetrical with a protuberance portion that protrudes to a greater extent on the other side in the direction of the central axis.

[0011] Therefore, the protuberance portion is not cut with each revolution of the workpiece. For example, in a hob cutter with two cutting edges, the workpiece is only cut once every two revolutions, so the thickness cut in one revolution is combined into two revolutions, and the thickness cut is thicker than the amount cut each revolution. This makes it possible to avoid promoting flank wear in the side relief portion of the cutting edge of the hob cutter, thereby suppressing hob wear. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a hob cutter according to the present invention. [Figure 2] FIG. 2 is a diagram illustrating the cutting edge shape of the hob cutter of the present invention. [Figure 3] 4A to 4C are diagrams for explaining the operation of the hob cutter of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0014] A hob cutter is a cutting tool used to form workpiece teeth by cutting gears on a workpiece. As shown in Fig. 1, the hob cutter 1 includes a cylindrical base body 2 that rotates about a central axis L, and a plurality of cutting edges 3 arranged in a spiral on the outer circumferential surface of the base body 2. The hob cutter 1 is assembled by inserting the cutting edges 3 into the base body 2 and tightening a nut 4.

[0015] Next, the cutting edge 3 of the hob cutter 1 of the present invention will be described with reference to Fig. 2. Fig. 2 is a view of a portion of the cutting edge 3 as viewed perpendicularly to the central axis L. The cutting edge 3 is a double-start hob.

[0016] The cutting edge shape of the first-tooth cutting portion 3 has a protuberance portion 5 that protrudes more on one side in the direction of the central axis (left-right direction centered on the tooth trace direction), resulting in an asymmetrical shape centered on the tooth trace direction. The cutting edge shape of the second-tooth cutting portion 3 has a protuberance portion 5 that protrudes more on the other side in the direction of the central axis L, resulting in an asymmetrical shape. In other words, the cutting edge shapes of adjacent teeth of the cutting portion 3 are inverted shapes. Note that the only difference between the first and second teeth is the position of the protuberance portion; otherwise, the width and height in the axial direction of the blade are the same.

[0017] Next, the operation of the hob cutter 1 of the present invention will be described with reference to Fig. 3. The hob cutter 1 of the embodiment of the present invention cuts a workpiece up to two revolutions counterclockwise, as shown in the left diagram of Fig. 3.

[0018] In part A of the work gear 6, the first rotation of the work starts with the first thread of the cutting edge 3 of the hob cutter 1. As shown in the right diagram of Figure 3, in part A of the first rotation of the work, the cutting edge 3 of the hob cutter 1 cuts only the involute portion (flank portion) 7, which is the tooth surface of the work gear 6. In the right diagram of Figure 3, the state before cutting is shown by a two-dot chain line, and the state after cutting is shown by a solid line. Then, in part A of the workpiece in the second rotation of the work, the cutting edge 3 of the hob cutter 1 cuts the involute portion 7 and tooth dedendum 8 of the work gear 6. The tooth dedendum 8 is cut by the protuberance portion 5 of the cutting edge 3, and the cutting allowance is thicker than the cutting allowance of the involute portion 7 per rotation, resulting in a thick cut.

[0019] The hob cutter 1 of the present invention has a multi-thread cutting edge, and the cutting edge shapes of adjacent threads of the cutting edge 3 are inverted, so that, for example, the tooth base 8 of the work gear 6 is not cut by the protuberance portion 5 every time the workpiece is rotated.

[0020] Specifically, with a hob 1 having a two-tooth cutting edge, cutting occurs only once every two revolutions, reducing the frequency of cutting at the involute portion 7 by half. This reduces the amount of flank wear and makes it possible to avoid accelerating flank wear at the side relief portions of the cutting edge of the hob 1.

[0021] In addition, the thickness cut in one go is cut over two revolutions, and the resulting cut is thicker than the amount cut in each revolution. Therefore, the wear position of the crater wear that occurs on the rake face is moved away from the edge (flank) of the cutting edge of the hob cutter 1. As a result, it is possible to prevent the flank wear and crater wear from merging, and it is possible to suppress wear on the hob cutter 1.

[0022] The hob cutter 1 of the present invention is effective when rotating a workpiece with a multi-start hob, and is therefore effective when the number of teeth on the work gear 6 and the number of threads on the hob are not divisible by an integer. While the above example uses a two-start hob with an odd number of teeth, the present invention is not limited to this and similar effects can be achieved with hobs with three or more threads, simply by changing the cutting edge shape of the cutting portion 3 for each number of threads. In short, the involute portion 7 of the tooth flank needs to be identical to accurately reproduce the involute portion, and only the protuberance portion 5 of the cutting edge needs to be asymmetric depending on the number of threads. [Explanation of symbols]

[0023] 1 hob cutter 2 Base 3 Blade 4 nuts 5 Pro-Chute Balance Club 6 Work gear 7 Involute section 8 Tooth root L center axis

Claims

[Claim 1] A hob cutter comprising a cylindrical base body rotating around a central axis line and a plurality of blades arranged spirally on the outer peripheral surface of the base body, The cutting edge shape of one of the two adjacent grooves of the cutting portion has an asymmetric shape in which a protuberance portion having a large protrusion amount is provided on one side in the central axis direction, The cutting edge shape of the other of the two adjacent grooves of the cutting portion is asymmetrical in that the protuberance portion has a larger protrusion amount on the other side in the direction of the central axis. A hob cutter characterized by:

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