JPS5937169B2 - Tokushiyuhagata Hob - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hob with a special blade shape, and its purpose is to prevent the flow of chips from converging at the boundary corner between the rounded part of the cutting edge and the side cutting part in gear cutting. However, by preventing the occurrence of such corner wear and reducing cutting resistance, the hob's wear resistance and durability have been improved. The purpose of the present invention is to provide a hob with a special blade shape that improves gear cutting, enables highly efficient gear cutting, has high hobbing accuracy, and is easy to grind during hob manufacturing.

Hitherto, hobs ranging from relatively small modules to large modules have been assembled, integrated, or with carbide blades, but the tooth profiles of these hobs have not changed to date.

This is because there are various constraints imposed by the tooth profile shape of the gear to be cut, and the tooth profile of the hob or milling cutter is naturally determined and constitutes the current basic shape in order to satisfy each dimension.

However, it is well known that when a cutting tool has a "corner" in its tooth profile, flank face wear at the corner is greater than at other cutting edge parts.

In addition, an abnormally large layer line occurs at the boundary between the rounded edge of the hob and the side cutting edge.

This wear is large on the rounded part of the cutting edge and small on the side cutting edge.

In extreme conditions, this wear not only doubles the cutting resistance, but also reduces the precision of the gear being cut and causes significant wear on a portion of the cutting edge of the tool, making it necessary to grind the tool, including the normal square shape, based on this wear. However, there were drawbacks such as further shortening the lifespan of expensive hobs.

Hob installation When viewed from above, the hob square 1 is shown in Figure 4.
The grinding wheel 2 is applied to the grinding wheel 2, and the grinding wheel forming part must grind the radiused part of the rounded part a of the cutting edge with the grinding wheel relief angle 3 open.

Therefore, the boundary corner b between the rounded part a of the cutting edge and the side cutting edge part C
? A large corner is formed, and cutting by this portion causes corner wear.

The cutting part where edge wear occurs is shown in Fig. 5 A2.

In other words, A is for downward cutting and the mouth is for upward cutting, but when the tooth groove is scraped at the cutting edge, the chips are sheared and distorted by the cutting force and flow out of the rake face. start.

As shown in Figure 6, the chip flow model is
The more flowing chips are restricted from spreading beyond the left and right tooth flanks and must shrink by 20.1% before passing the bb line.

This lateral pressure and cutting force from both tooth surfaces causes the chips to flow while buckling as if gouging the rake face, which can be understood to be the cause of crescent-shaped crater wear on the cutting edge.

When chips stronger than the side blade bc merge, the cutting edge bab
The flow of chips during twisting rises perpendicularly to the rake face at the bb line.
"Outflow model" that rises immediately from the cutting edge ridge rather than the side blade bc
Considering this, the interference power of the chips will be balanced.

As shown in Fig. 7, the flow from the cutting edge curves up at the edge connecting both corners, and merges with the flow from the side edges, which flow in different directions, at the edge.

At this time, when the heel has a so-called corner, as shown in FIG. 6 t, the cutting thickness of the cut heel made by the previous blade becomes rough, which tends to create creases and cause wear.

A22B and C in Figure 8 represent the flow of chips shown in a rectangular section at right angles to the center, edge, and side edges of the cutting edge in Figure 7. In A and C, the cut chips flow out. However, at the boundary corner where the radius of the rounded part a of the cutting edge and the side cutting edge part C contact, the tooth surface 4 must immediately rise as shown in 5 when it is ground.

If the cutting speed is high or the material to be rigid is hard, the shearing and warping deformation caused by rising from 4 to 5 will be inhibited by 5, and the lower end of 4 will be under high pressure due to compression.

Figure 9 shows the initial stage of heel wear and its growth, using SCM3. Using HB160, the conditions were such that edge wear was difficult to occur, and the width of the cutting marks on the rake face where flow was impeded was as small as 0.2 mm, and the edge of the cutting edge in this area was When it starts to glow faintly white, when you observe it with a tool microscope, you can see minute "
The mouth where "chip" had occurred.

As shown in Figure 2, it can be assumed that the above defects are caused by the growth of the mouth.

The above-mentioned chattering wear occurs when the chips from the cutting edge and the left and right side blades bend in three directions at the creases, and the tiny parts that form the creases prevent the outflow of chips, resulting in chipping of the cutting edge. It was found that the growth occurs due to the scraping of the gear material that passes through the hole without being cut.

Figure 10 shows the progress of edge wear in Experiment 1. rt
14. Case of Z33 and Experiment 2 y m 3 t Z42
The cases were compared.

When the sharply occurring wear at the edge reaches a certain wear range, when we compare the edge wear and the center wear of the cutting edge, there is a larger difference in the edge wear.

However, it can be seen that the growth of wear does not grow any more rapidly, but instead grows along a gentle curve.

The present invention eliminates the "corner" wear of the square, which greatly affects the life of the gear cutting tool, and keeps the average wear of the entire square to a minimum, thereby extending the life of the gear cutting tool and improving durability.
It provides a special rectangular configuration that improves wear resistance and realizes highly efficient gear cutting.

In the present invention, a chamfered part or a corrugated part is formed in the boundary corner where the rounded part a of the cutting edge and the side cutting edge ErfAc come into contact. /3 point.

FIG. 1 shows the square shape of a typical chamfer hob of the present invention.
Used as a finishing agent for small gears.

A chamfered portion 6 having a width of hh' is formed in a portion corresponding to a conventional corner portion.

It is chamfered at an angle of αl. By using the special edge shape hob of the present invention, chips can be removed from the rounded edge part a and the side cutting edge as shown in Figures 2 and 3. By separating into part C, a smooth flow of chips with no rising creases was obtained.

In this way, by incorporating the width h-h' portion, which replaces the conventional corner portion, into the standard square configuration from the beginning, creases and rising portions that obstruct the outflow of chips are completely eliminated.

Incidentally, the grinding process of the hob of the present invention can be easily carried out by cutting off the hob rectangle in a dotted line as shown in FIG. 4, and the problems of conventional machining can also be solved.

In the example shown in FIG. 11, the cutting edges of the formed corrugated portions are sequentially arranged alternately in the tooth direction.

Reference numeral 7 indicates a waveform portion, and 8 indicates a waveform portion in the next order in the tooth direction with a phase shift.

[Brief explanation of the drawing]

Fig. 1 is a front view showing one embodiment of the special blade shape of the present invention;
The figure is a perspective explanatory diagram of the flow of chips according to the present invention. Figure 3 (a) and (c) are explanatory diagrams of the flow of chips at the rounded part of the cutting edge, the chamfered part, and the side cutting edge, respectively. Fig. 5A is an explanatory diagram of the occurrence of corner wear depending on the cutting direction of the mahob; Fig. 6 is an explanatory diagram of the chip flow in the conventional example; Fig. 7 is a perspective explanatory diagram of the same chip flow; Figure I. Figures 9 and 9 are explanatory diagrams of chip flow at the rounded edge, boundary corner, and side cutting edge of the conventional example. 2 is an explanatory diagram showing the initial stage and growth state of heel wear; FIG. 10 is a graph showing the progressing state of heel wear; and FIG. 11 is a front explanatory diagram of a corrugated portion whose phase is shifted in the tooth direction. 1... Hob square, 6... Chamfered part,
7, 8... Waveform part, a... Rounded edge part, b... Boundary corner part, C... Side cutting edge part.

Claims (1)

[Claims] 1. A special blade hob having a boundary corner between a rounded tooth tip portion a and a side cutting edge portion C, characterized in that a chamfered portion or a corrugated portion is formed at the boundary corner.