JPH0730261Y2 - Structure of tool attachment part on the spindle of machine tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a structure of a tool mounting portion on a spindle of a machine tool, and more particularly to a technique for extending the life of the portion.

<Prior Art> Machine tools such as a milling machine, a machining center, or a die-sinker are equipped with a spindle for rotationally driving a tool such as a milling cutter or a cone used for cutting or grinding.
The spindle is rotatably supported by the spindle head, and is rotationally driven by an electric motor or the like. In many cases, a taper-shaped tool mounting hole is formed at the tip of the main shaft, and the shank of the tool is fitted and fixed in this tool mounting hole.

FIG. 6 shows an example of the structure of the spindle head of the machine tool. In this figure, the spindle 1 is firmly supported by the radial roller bearings 3 and 4 and the thrust ball bearing 5 at the center of the spindle head 2. . Therefore, the main shaft 1 does not swing even when subjected to a large machining component force generated in the case of heavy cutting or the like, and a desired rotation is secured.

On the other hand, a taper-shaped tool mounting hole 6 is formed at the tip of the spindle 1, and a taper shank portion (hereinafter, shank portion) of a tool (a tool holder in this drawing) 7 is formed in the tool mounting hole 6.
7a is fitted. A pull-stat portion 7b is integrally formed at the rear end (right side in the drawing) of the shank portion 7a, and a collet 8 of a chuck mechanism provided in the main shaft 1 is held by the pull-stat portion 7b.

The chuck mechanism is composed of a draw bar 9 and a disc spring group 10 in addition to the collet 8, and the pull stud 7b is strongly moved to the right in the figure by the spring force of the disc spring group 10 via the draw bar 9 and the collet 8. The tool 7 and the spindle 1 are connected by pulling. When replacing the tool 7, push the right end (not shown) of the draw bar with hydraulic pressure to make the collet 8 pull pull 7b.
It is done by opening. And an automatic tool changer (not shown) (hereinafter ATC: Automatic Tool Changer)
In a machining center equipped with the above, a tool 7 suitable for various kinds of processing is dynamically exchanged by linking the ATC and the chuck mechanism, and various kinds of processing can be continuously performed.

The tool mounting hole 6 of the spindle 1 and the shank portion 7a of the tool 7 have basically the same taper ratio, and the taper ratio on the tool mounting hole 6 side is strictly controlled using a gauge. Then, on the surface of the tool mounting hole 6, various surface hardening treatments, for example, nitriding treatment using molybdenum steel, in order to prevent abrasion caused by replacement of the tool 7 and fine movement during machining and maintain machining accuracy,
Quenching treatment using high carbon steel and carburizing treatment using corrosion resistant steel are performed.

Further, as shown in FIG. 7 (enlarged perspective view of portion A in FIG. 6), key grooves 11 and 12 are formed in the tip portion of the spindle 1 and the flange portion 7c of the tool 7, respectively. A parallel key (hereinafter, key) 13 is fitted in 12. Keyway on spindle 1 side 11
Penetrates to the tool mounting hole 6, and the keyway on the tool 7 side
The reference numeral 12 is formed so that the flange portion 7c is hollowed out. Key 13
Is to prevent the tool 7 and the spindle 1 from rotating relative to each other due to a large torque during heavy cutting. In the illustrated example, two tools are provided at 180 ° intervals. The key 13 is fixed to the spindle 1 side by a hexagon socket head bolt 14.

<Problems to be solved by the invention> By the way, in the above-described conventional spindle 1, when the frequency of tool 7 replacement and the operating rate are high, a short period (for example, 1 to 3 months)
However, there is a problem in that the machining accuracy is reduced and the spindle 1 must be replaced. In the spindle 1 in which the machining accuracy has been reduced, a sag phenomenon and a fine wear phenomenon are recognized on the surface of the tool mounting hole 6, and these phenomena are observed on the tip side (especially the key groove
(Near 11). These phenomena are caused by a slight swinging motion of the tool 7, so-called chattering. As a result of investigation and analysis through experiments and the like, the following two points were found to be the cause of chattering.

First, as the first point, since the key groove 11 (that is, the notch) is provided in the tip end portion of the main shaft 1, the restraining force is smaller than that in the rear portion. When the tool 7 is pulled by the draw bar 9, a high surface pressure is generated in the tool mounting hole 6 due to the pulling force P thereof. However, the tip is keyway 11
Therefore, the surface pressure of the portion is reduced due to a slight expansion deformation toward the outside.

The second point is the deformation due to the force (indicated by p in the figure) acting on the side surface 11a of the key groove 11 on the main shaft 1 side during machining. FIG. 8 shows a BB cross section in FIG. 6, but the force p is generated by the cutting resistance of the tool 7 or the like, and acts via the key 13 in the direction opposite to the rotation of the spindle 1. Then, in the case of heavy cutting or the like, the spindle 1 is deformed as shown by the broken line, and the gap δ is generated. The hexagon socket head cap bolt 14 is for fixing the key 13 to the main shaft 1 and cannot prevent the key 13 from moving.

Currently, in machining centers, NC (Numerical
Control) is used to perform high-precision machining, but naturally the machining precision deteriorates when the tool 7 itself causes the chattering motion described above. Therefore, a check by a gauge is appropriately performed, and when there is a predetermined amount of wear or fatigue, the spindle 1 is replaced as described above. However, this work requires a great deal of time and labor for disassembling the spindle head 2 and the cost of replacement parts (spindle 1, etc.) is high. When the frequency of tool replacement is high, the effect on the operating rate of the machine cannot be ignored, and there is a demand for immediate improvement.

The present invention has been made in view of the above circumstances, and an object thereof is to improve the durability of the tool mounting hole 6 and thus extend the life of the spindle 1.

<Means for Solving the Problem> Therefore, in the present invention, the shank portion of the tool is fitted into the tapered tool mounting hole formed at the tip portion of the spindle to mount the tool, and the tip portion of the spindle and the In the structure of the tool mounting portion in the spindle for fitting the key into the key groove formed in each of the tool and stopping rotation of the tool, the key groove and the key groove formed in the tip portion of the spindle A residual wall portion is formed between the tool mounting hole and a recess is formed on the entire circumference of the tip portion of the main shaft between the residual wall portion and the key groove.

<Operation> Due to the remaining portion formed between the key groove and the tool mounting hole, there is no notch, and the tip end portion of the main spindle is not expanded and deformed due to the pulling force of the drawbar. In addition, since there is a gap between the remaining portion and the keyway, the keyway and the tool mounting hole are completely separated, and the force in the direction of rotation caused by the cutting resistance from the key during heavy cutting etc. Does not affect the tool mounting hole.

<Embodiment> An embodiment of the present invention will be specifically described with reference to the drawings. still,
In the description of the embodiments, the same members as those in the above-described conventional example are designated by the same reference numerals, and the duplicated description will be omitted.

FIG. 1 shows an enlarged half section of a tool mounting member for a spindle according to an embodiment of the present invention, and FIGS. 2 and 3 are perspective views of a key groove in this embodiment and C- in FIG. The C section and the C section are respectively shown. Further, FIG. 4 shows an EE section in FIG. 2, and FIG. 5 shows an FF section in FIG.

In these drawings, reference numeral 15 is a residual portion formed between the key groove 11 of the main shaft 1 and the tool mounting hole 6. The remaining portion 15 is provided in both of the two key grooves 11, and as a result, the tool mounting hole 6 is not cut out to the tip. The remaining portion 15 is made as thick as possible in consideration of the strengths of the key groove 11 and the key 13, but the depth of the key groove 11 that fits with the key 13 (the length in the front-back direction) is fitted to avoid an increase in stress. ) Is made larger than the conventional one, and the key 13 fitted into the key groove 11 is formed into a substantially L-shape so that the fitting area with the tool 7 side is secured at the same level as the conventional one. The key
13 is fixed to the spindle 1 by means of a hexagon socket head 14 as in the conventional case. In addition, a relief portion, that is, a so-called recess 16 is provided at the lower end of the key groove 11 in the figure, and the recess 16 is formed in an annular shape around the entire circumference of the main shaft 1. Therefore, the residual portion 15 has a cylindrical shape without undulations, and the residual portion 15 including the tool mounting hole 6 and the key groove 11 are not continuous.
Reference numeral 17 in the drawing denotes an attachment mounting screw hole for mounting the attachment.

The operation of this embodiment will be described below.

Also in this embodiment, the tool mounting hole 6 is formed by the pulling force of the draw bar.
A high average surface pressure occurs on the inner surface of the. However, in this embodiment, since the residual thickness portion 15 is formed on the inner peripheral side of the key groove 11, the tip end portion of the tool mounting hole 6 has an annular shape with no notch. A recess 16 is formed between the remaining portion 15 and the key groove 11 over the entire circumference. Therefore, the tip portion of the main shaft 1 cannot be easily expanded and deformed, and the key groove 11
The tool mounting hole 6 and the tool mounting hole 6 are completely separated from each other, and even when a force p in the rotational direction due to cutting resistance is applied to the side surface 11a of the key groove 11 from the key 13 during heavy cutting, etc. The influence of the force acting on 11 on the tool mounting hole 6 has been cut off, and the deformation of the spindle 1 that causes a gap between the tool mounting hole 6 and the tool 7 has stopped.

As a result, chattering does not occur even when an out-of-plane bending load and a circumferential force, which are external processing forces, act strongly, and the tool mounting hole 6
The wear and settling of the spindle 1 is remarkably reduced as compared with the conventional one, and the life of the spindle 1 is dramatically improved. In this embodiment, in the milling process, a tool 7 having a diameter of 100 mm and 12 teeth is used, and the feed is 100 to 150 mm / min, the cutting width is 80 mm, the cutting depth is 5 mm, and the rotation speed is 200 r.
With the machining conditions of pm, the life of the spindle 1 has been extended several times compared to the conventional one.

Although the description of the embodiments has been completed, the present invention is not limited to these embodiments. For example, in each of the above embodiments, the structure of the tool mounting hole portion in which the two keys 13 are fixed to the spindle 1 has been described, but the present invention is applied to the one using one or three or more keys 13. Alternatively, the present invention may be applied to the tool 7 having the key 13 attached thereto. Further, the remaining portion 15 may take a form other than that shown in each of the above embodiments.

<Effects of the Invention> According to the structure of the tool mounting portion in the spindle of the machine tool according to the present invention, in the spindle in which the key groove into which the key for fixing the tool is fitted is formed at the tip end thereof, the key groove and the tool Since the residual part is formed between the mounting hole and the annular recess between the residual part and the key groove, the key groove and tool mounting hole are completely separated and pushed, and the drawbar As a result, the tip end portion does not spread when the tool is pulled, the force acting on the key groove does not affect the tool attachment hole 12, and the tool attachment hole is not deformed by cutting resistance. As a result, the tool is firmly held, wear and fatigue of the tip part due to chattering etc. are reduced, the life of the spindle is extended and maintenance costs are reduced and the operating rate of machine tools is improved. The effect of being able to be played.

[Brief description of drawings]

FIG. 1 is an enlarged half sectional view showing a tool mounting portion of a spindle according to an embodiment of the present invention, and FIGS. 2 and 3 are perspective views of a key groove in this embodiment and CC in FIG. Sectional views, FIGS. 4 and 5 are EE sectional views in FIG. 2 and FF sectional views in FIG. 2, and FIG. 6 is a sectional view showing an example of a conventional structure of a spindle head of a machine tool. FIG. 7, FIG. 7 and FIG. 8 are an enlarged perspective view and a sectional view taken along line BB in FIG. 6, respectively. In the figure, 1 is a spindle, 2 is a spindle head, 3 and 4 are radial roller bearings, 5 is a thrust ball bearing, 6 is a tool mounting hole, 7 is a tool, 8 is a collet, 9 is a draw bar, 10 is a disc spring group, 11, 12 is a keyway, 13 is a key, 15 is a residual part, 16
It's a sneeze.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Mitsuo Tani 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Prefecture Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute (72) Kinji Katayama 3 Gion, Asanan-ku, Hiroshima-shi, Hiroshima 2-1-1 Mitsubishi Heavy Industries, Ltd. Hiroshima Machinery Factory (56) References Sho 60-29036 (JP, U) JP 62-40133 (JP, B2)

Claims (1)

[Scope of utility model registration request] 1. A key is formed on each of the tip of the spindle and the tool while fitting the tool by fitting a shank portion of the tool into a tapered tool mounting hole formed at the tip of the spindle. In the structure of the tool mounting portion in the spindle that fits the key in the groove to prevent the tool from rotating, a residual thickness is formed between the key groove formed at the tip of the spindle and the tool mounting hole. And a recess is formed on the entire circumference of the tip portion of the main spindle between the remaining portion and the key groove, the structure of the tool mounting portion in the main spindle of a machine tool.