JP2501282Y2 - 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. 4 shows an example of the structure of the spindle head of a machine tool.
In this figure, a spindle 1 is firmly supported at the center of a spindle head 2 by radial roller bearings 3 and 4 and thrust ball bearings 5. 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, the tip of the spindle 1 has a tapered tool mounting hole 6
Is formed, and the taper shank portion (hereinafter, shank portion) 7a of the tool (tool holder in this drawing) 7 is fitted into the tool mounting hole 6. A pull stud 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 can be held by the pull stud portion 7b. .

The chuck mechanism is composed of a draw bar 9 and a disc spring group 10 in addition to the collet 8.
The pull stud portion 7b is strongly pulled to the right in the figure by the spring force of the disc spring group 10 via the, so that the tool 7 and the spindle 1 are coupled. When the tool 7 is replaced, the right end (not shown) of the drawper 9 is pressed by hydraulic pressure or the like, and the collet 8 opens the pull stud 7b. An automatic tool changer (not shown) (hereinafter, ATC: Automatic Tool Cha
In a machining center equipped with a nger), a tool 7 suitable for various kinds of machining is automatically exchanged by interlocking the ATC and the chuck mechanism so that various kinds of machining can be continuously performed.

The taper ratios of the tool mounting hole 6 of the spindle 1 and the tool 7 and the shank portion 7a are basically the same, and the taper ratio of the tool mounting hole 6 side is strictly controlled using a gauge. And
The surface of the tool mounting hole 6 has various surface hardening treatments, such as nitriding treatment using molybdenum steel, in order to prevent wear 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.

<Problems to be Solved by the Invention> Meanwhile, the above-described conventional spindle 1 has the following problems.

FIG. 5 shows the surface pressure distribution of the fitting surface generated when the drawbar 9 pulls the tool 7 with a predetermined tensile force Q in the conventional tool mounting structure. The solid line in the figure shows a state in which the taper ratio of the tool mounting hole 6 is accurately controlled using a gauge, and the broken line shows a state in which it is used to some extent. As can be seen from this figure, the surface pressure at the front and rear end portions is high initially, and thereafter the surface pressure at the central portion gradually increases and the surface pressure at the tip portion decreases.

When this state becomes remarkable, the actual support length of the tool 7 becomes short, and the tool 7 starts to make a slight swinging motion, so-called chattering motion.

As a result of investigation and analysis through experiments, it was found that the following two points caused chattering. First, the first
As a point, the tip of the tool mounting hole 6 (the part on the left side in the figure) is more susceptible to the stress during processing, fine movement, etc. than other parts, causing more wear and plastic deformation (so-called sag). There is. The second point is that the shape of the shank portion 7a of the tool 7 that fits into the tool mounting hole 6 is slightly different within the manufacturing tolerance, so the surface pressure distribution is not constant, and the pulling force Q of the draw bar 9 with respect to the fitting area is Q. However, since the size of the device cannot be made too large due to downsizing of the device, chattering may be promoted and wear and fatigue may be further expanded. It should be noted that these abrasions and fatigues are not limited to the tip portion and extend over a fairly wide range.

Currently, in machining centers, etc., NC (Numerica
l Control) is used for high-precision machining,
When the tool 7 itself causes the chatter movement as described above, the machining accuracy naturally deteriorates. Therefore, the gauge 1 is appropriately checked, and if there is a predetermined amount of wear or fatigue, the spindle 1 is replaced. This work requires a great deal of time and man-hours 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 immediate improvement has been demanded.

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

<Means for Solving the Problem> Therefore, in order to solve this problem, the present invention mounts the tool by fitting the shank portion of the tool into the tapered tool mounting hole formed at the tip of the spindle. In the structure, the taper angle of the tool mounting hole is the same as the taper angle of the shank portion, and an annular diameter increasing portion is provided at an intermediate portion in the axial direction of the tool mounting hole, and the diameter increasing portion is provided with the diameter increasing portion. An object of the present invention is to provide a structure of a tool mounting portion in a spindle of a machine tool, characterized in that an elastic member having a lower compression rigidity than a shank portion is fitted to make the inner surface of the tool mounting hole flush.

<Operation> Since the diameter-increased portion is formed in the middle portion of the tool mounting hole, the shank portion of the tool is not actually supported at this portion,
As a result, the actual support length does not decrease even if the tip portion is slightly worn or worn. Further, since the shank portion of the tool is supported by the front portion and the rear portion of the tool mounting hole, the surface pressure is inevitably improved due to the reduction of the actual fitting area, and chattering is suppressed. Furthermore, since an elastic member with low compression rigidity is fitted to the increased diameter part and the inner surface of the tool mounting hole is flush, chips such as chips adhere to the increased diameter part and the shank part gets caught. Does not occur.

<Embodiment> An embodiment of the present invention will be specifically described with reference to the drawings.
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 duplicated description will be omitted.

FIG. 1 shows an enlarged half section of the tool mounting portion of the spindle according to this embodiment, and FIG. 2 shows the surface pressure distribution of the tool mounting portion in this embodiment. Then, FIG. 3 is a graph showing the effective range when the present invention is applied.

In FIG. 1, the spindle 1 is formed with a tool mounting hole 6 having the same taper angle as that of the shank portion 7a of the tool 7, and an annular diameter increasing portion 6a is formed in the middle of the tool mounting hole 6. Are formed. Increase the amount of size is 2mm in the radial direction in the present embodiment, the length 1 ₀ is about 60% of the engagement length L of the tool attachment hole 6 and the tool 7. Therefore, before and after that, the remaining portion 6 that abuts and fits with the shank portion 7a of the tool 7
b and 6c are formed, but in this embodiment, these lengths 1 ₁ and 1 _{2 are formed.}
Are 23% and 17% of the fitting length L, respectively.

In the case of the present embodiment, the diameter increasing portion 6a has a collar 11 made of a copper alloy.
Is fitted, and then hard chrome plating is applied to the whole. As a result, the inner surface of the tool mounting hole 6 has a finish that is seemingly the same as a normal one.

 Hereinafter, the operation of the present embodiment will be described.

When the shank portion 7a of the tool 7 is fitted in the tool mounting hole 6 of the main spindle 1 and the pull stud portion 7b is pulled by the above-described check mechanism, in the main spindle 1 of the present embodiment, the shank portion 7a has an increased diameter portion at the intermediate portion. It comes into contact with the collar 11 fitted in the 6a. Since the collar 11 is made of a copper alloy, its compression rigidity is remarkably lower than that of the main shaft 1 and easily elastically deforms. Therefore, as shown in FIG. 2, the surface pressure is significantly high in the front and rear remaining portions 6b and 6c, and is considerably low in the diameter increasing portion 6a.

The broken line in FIG. 2 shows a state of being used to some extent. Even in this case, the surface pressure slightly fluctuates as in the conventional device, but basically the above-mentioned tendency does not change, and
The surface pressures of 6b and 6c are secured at sufficiently high values. Therefore, the shank portion 7a is held with the same actual support length as that at the beginning, and the occurrence of chattering can be suppressed. Further, even if there is a shape difference within the manufacturing tolerance of the shank portion 7a, the surface pressure is increased, so that the fitting / fixing is firmly performed.

Due to the reasons described above, wear and fatigue of the tool mounting hole 6 are significantly reduced as compared with the conventional one, and the life of the spindle 1 is dramatically improved. In this embodiment, a tool 7 having a diameter of 100 mm and a number of teeth of 12 is used for milling, and the feed is 100 to 150 m
Under the machining conditions of m / min, cutting width 80 mm, depth of cut 5 mm, and rotation speed 200 rpm, the life of the spindle 1 has been extended several times compared to the conventional one. Further, in this embodiment, not only is the diameter-increased portion 6a simply formed, but the collar 11 is fitted so that no step can be formed in the tool mounting hole 6, so that cutting chips or the like adhere to the portion.
The problem that the shank portion 7a is caught when the tool 7 is attached does not occur.

The diameter increment majority 6a length 1 ₀ result of variously varied test the ratio of engagement length L of the third as shown in FIG 30%
It has been confirmed that the life of the spindle 1 is remarkably improved in the range of 70% to 70%. Further, front and rear balance 6b, the length of 6c 1 _1, 1 ₂ also results of tests by changing the ratio for, the fitting length L
It became clear that when the content is 15% or less, the occurrence of wear and fatigue becomes unacceptable.

Although the description of the embodiment has been completed, the present invention is not limited to this embodiment. For example, a material other than a copper alloy such as an aluminum alloy, resin, or rubber may be used as the material of the collar 11, or the collar 11 itself may be omitted. Further, diameter increment length 1 ₀ and the remainder of the length 1 ₁ of the most, 1 for ₂ is also not limited to the ratio of the present embodiment, it can be appropriately selected according to the tool 7 to the reasons or practical work is there.

<Effect of the Invention> According to the structure of the tool mounting portion in the spindle of the machine tool according to the present invention, the taper angle of the tool mounting hole is made the same as the taper angle of the shank portion, and the intermediate portion of the tool mounting hole in the axial direction is formed. Since a diameter-increased portion is formed in the diameter-increased portion and an elastic member having a lower compression rigidity than the shank portion is fitted to make the inner surface of the tool mounting hole flush, the surface pressure of the remaining portion is increased. The wear and fatigue of the tip part will decrease and the chattering of the tool will not occur even when these phenomena occur, and chips such as cutting chips will adhere to the enlarged diameter part and the shank part will be caught. As a result, the life of the spindle can be extended, and maintenance costs can be reduced and the operating rate of machine tools can be improved.

[Brief description of drawings]

FIG. 1 is an enlarged half sectional view showing a tool mounting portion of a spindle according to this embodiment, and FIG. 2 is a surface pressure distribution diagram of the tool mounting portion in this embodiment. FIG. 3 is a graph showing the effective range when the present invention is applied. On the other hand, FIG. 4 is a longitudinal sectional view showing an example of a conventional spindle head structure of a machine tool, and FIG. 5 is a surface pressure distribution diagram of a tool mounting portion in this example. 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, 6a is a diameter increasing portion, 6b and 6c are the rest, 7 is a tool, 7a is Taper shank part, 7b pull stud part, 8 collet,
9 is a draw bar, 10 is a disc spring group, and 11 is a collar.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Haruyoshi Kuwahara, 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Prefecture, Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Kinji Katayama, 3 Gion, Asanan-ku, Hiroshima-shi, Hiroshima Prefecture 2-1-1 Mitsubishi Heavy Industries, Ltd. Inside the Hiroshima Koki Plant (56) References: 61-141038 (JP, U)

Claims (2)

(57) [Scope of utility model registration request] 1. A structure for mounting a tool by fitting a shank portion of the tool into a tapered tool mounting hole formed at a tip portion of a main shaft, wherein a taper angle of the tool mounting hole is set to a value of the shank portion. The tool has the same taper angle, and an annular diameter increasing portion is provided at an intermediate portion in the axial direction of the tool mounting hole, and an elastic member having a compression rigidity lower than that of the shank portion is fitted in the diameter increasing portion. A structure of a tool mounting portion on a spindle of a machine tool, characterized in that the inner surface of the mounting hole is flush. 2. The length of the diameter-increased portion is in the range of 30% to 70% of the fitting length of the tool mounting hole with the tool, and the length of one remaining portion is at least the fitting length. It is 15% or more, The structure of the tool attachment part in the spindle of the machine tool of Claim 1 characterized by the above-mentioned.