JPH0410962Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention relates to the structure of a tool attachment part formed at the tip of the spindle in the spindle head of a machine tool such as a vertical milling machine, and particularly relates to the structure of the tool attachment part formed at the tip of the spindle. Regarding the extension of

[Conventional technology]

Generally, in a machine tool such as a vertical milling machine, a spindle is rotatably supported by a spindle head, the shank of the tool is inserted into a tapered hole formed at the tip of the spindle, and the shank is pulled with a drawbar to form the taper. The tool is firmly fitted into the hole, thereby supporting the tool, and is configured to be rotationally driven via the spindle.

Recently, tool changers (hereinafter referred to as ATC) have been installed to automatically replace the tools supported by the spindle with tools suitable for various types of machining, making it possible to perform various types of machining continuously. I have to. In such machine tools,
The accuracy of the tapered hole portion of the spindle deteriorates due to wear due to frequent tool replacement, damage from chips adhering to the tool, and micro-motion wear during machining, and as a result, machining accuracy tends to decrease. A problem arises.

Conventionally, in order to suppress the deterioration of the machining accuracy, various surface hardening treatments have been applied to the tapered hole portion, such as nitriding treatment of Mo-based nitriding steel, quenching treatment of high C high alloy steel, and carburizing treatment of corrosion-resistant steel. This suppresses wear of the tapered hole, thereby maintaining tool support accuracy.

[Problem that the invention attempts to solve]

However, although the above-mentioned surface hardening treatment method achieves a certain degree of effect, it is still not fully satisfactory. Therefore, if the tool support accuracy deteriorates after long-term use, the entire spindle must be replaced.

In view of the above-mentioned conventional problems, the purpose of the present invention is to maintain tool support accuracy even during long-term use.
Therefore, it is an object of the present invention to provide a tool mounting structure for a spindle head in a machine tool that makes it unnecessary to replace the entire spindle.

[Means for solving problems]

The present invention has the following features in the tool mounting structure of the spindle head:
A cylindrical body support hole is formed at the tip of the spindle, and a cylindrical body having a tapered hole for attaching a tool on the inner surface is fitted into the support hole by shrink fitting, and the axially outer portion of the cylindrical body is fitted into the support hole. The cylindrical body is formed in a stepped shape with a slightly larger diameter than the inner part, and a concave groove is formed in a portion of the cylindrical support hole corresponding to the stepped portion, and a hydraulic pressure supply passage is communicated with this portion. It is characterized by being removable.

Here, the step portion in the present invention includes one formed in an inclined shape.

[Effect]

In the tool mounting part structure according to the present invention, a cylinder having a taper hole for tool mounting is removably attached to the tip of the spindle, so if the tapered hole part is worn or damaged, it can be replaced with a new one. Therefore, the tool supporting accuracy of the tapered hole can be maintained over a long period of time, and as a result, it is not necessary to replace the entire spindle.

Furthermore, since the cylindrical body is attached by shrink fitting, it is possible to avoid the occurrence of looseness and improve the attachment accuracy. In shrink-fitting the cylindrical bodies, if misalignment occurs when inserting the cylindrical bodies, it is very difficult to refit them correctly, but in this invention, the cylindrical bodies are Since the cylindrical body can be removed even in such a case, the shrink fitting operation can be repeated.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 3 are diagrams for explaining the structure of a tool attachment part of a spindle head in a vertical milling machine according to a first embodiment of the present invention.

The third diagram shows a vertical milling machine to which this embodiment is applied.
In the figure, 1 is a base fixed on a foundation surface, a saddle 2 is disposed on the base 1 so as to be movable in the Y direction shown in the figure, and a table 3 is placed on the saddle 2 so as to be movable in the X direction shown in the figure. Furthermore, a column 4 is erected on the base 1. Further, 5 is an ATC, and 7 is a tool exchange arm, and the arm 7 is configured to grasp a tool with gripping claws formed at both ends, descend in this state, rotate 180 degrees, and then ascend. ing. Note that 6 is an operation panel.

A spindle head 10 is disposed on the column 4 so as to be movable in the Z direction in the figure, and as shown in FIG.
Inside the body 11 of the spindle head 10 is a spindle 1.
2 is rotatably inserted and supported by a plurality of bearings 13. The spindle 12 has a cylindrical shape, and a drawbar 14 is inserted into the spindle 12 so as to be able to move vertically, and is biased upward by a biasing spring 17. This drawbar 14 is rod-shaped, and an engagement recess 15a of a collet 15 is engaged with an engagement recess 14a formed at the lower end thereof, and an engagement claw 15b of the collet 15 is engaged with an engagement recess 14a formed at the lower end of the drawbar 14.
The engagement portion 16b of the shank portion 16a of No. 6 can be engaged with and detached from the engagement portion 16b of the shank portion 16a.

A tool attachment portion 18 to which the tool 16 is attached is formed at the lower end of the spindle 12. The mounting portion 18 is constructed by forming a cylindrical support hole 19 at the lower end of the spindle 12, and fitting the cylindrical body 20 into the support hole 19 in a detachable manner. This cylindrical body 20 is made of ceramic, for example, zirconia (ZrO ₂ ), and as shown in FIG.
It has a cylindrical shape with a large-diameter stepped portion 20c on its inner surface, and the shank portion 16 of the tool 16 is formed on its inner surface.
A tapered hole 20d is formed which fits into the hole 20d with high accuracy.

Further, the cylindrical support hole 19 is formed in a shape that fits into the cylindrical body 20 with high precision. Further, an annular groove 19a is formed in the central portion of the cylinder support hole 19 above the stepped portion 20c, and a hydraulic passage 19b for supplying hydraulic pressure thereto is formed in the groove 19a.
are connected. Although not shown, this hydraulic passage 19b is connected to a hydraulic power source.

Next, the effects of this embodiment will be explained.

First, attachment and detachment of the cylindrical body 20 will be explained. The cylindrical body 20 is attached by normal shrink fitting. That is, the portion of the spindle 12 near the cylinder support hole 19 is heated, the cylinder 20 is cooled, and in this state the cylinder 20 is inserted to a predetermined position in the cylinder support hole 19.
When the temperature is returned to room temperature, the cylindrical body 20 is fitted into the spindle 12.

In addition, when removing the cylindrical body 20, the groove 1
Supply hydraulic oil into 9a at a hydraulic pressure of approximately 300Kg/ ^cm2 . Then, the hydraulic oil flows into the cylinder body 20 and the cylinder support hole 1.
9 and applies an outward force to the stepped portion 20c, whereby the cylinder 20 is removed from the cylinder support hole 19.

In this way, in this embodiment, the cylinder 20 can be removed from the spindle 12, so that the cylinder 20 can be removed from the spindle 12.
If the tapered hole 20d of 0 becomes worn or damaged, this cylinder body 20 can be replaced,
Therefore, there is no need to replace the entire spindle when the tool support precision deteriorates as in the conventional case, and an increase in cost due to replacing the spindle can be prevented.

In addition, in this embodiment, the cylinder body 20 and the spindle 1
A concave groove 19a is formed between the cylinder support hole 19 of the cylinder 2 and the cylinder support hole 19 of the cylinder 2, and high pressure oil is supplied thereto.
Since the structure is such that the cylindrical body 20 can be removed, it is possible to prevent damage to the spindle 12 side when the cylindrical body 20 is removed.

Furthermore, when the cylinder body is shrink-fitted, it may be difficult to achieve accurate fitting between the cylinder body and the support hole due to lack of skill of the operator. It was extremely difficult to remove and in some cases had to be disposed of. On the other hand, in this embodiment, since the cylindrical body can be removed, it is possible to perform the shrink fit again to obtain the above-mentioned fitting accuracy.

In general, when a tool is supported by the tapered hole and used for a long period of time, a detailed observation of the wear condition shows that both ends of the tapered hole in the axial direction are particularly prone to wear, while the center part is relatively free of wear. I understand that. Therefore, the center part of the tool comes into strong contact with the tapered hole, and the tool tends to swing around this part, causing chatter. In contrast, in this embodiment, the groove 19a formed on the back side of the axially central portion of the cylinder 20 allows the central portion of the cylinder 20 to be elastically deformed, even when the wear at both ends progresses. By weakening the contact in the center, the occurrence of chatter can be suppressed accordingly.

FIG. 4 shows a second embodiment of the present invention, which is an example in which the stepped portion of the cylindrical body is formed into a substantially tapered shape. In the figure, the same reference numerals as in FIG.

Reference numeral 30 denotes a cylinder made of ceramic, and the cylinder 30 has a large-diameter outer portion 30a and a small-diameter inner portion 30b having approximately the same wall thickness as the inclined portion (step portion) 3.
They are connected at 0c. Further, the cylinder support hole 29 is formed in a shape that fits with the outer part 30a and the inner part 30b of the cylinder 30 with high precision. The inclined portion 30 of the cylinder support hole 29
A concave groove 29a is formed on the back surface of the cylinder c, and a hydraulic passage 19b is communicated with the concave groove 29a.

In this embodiment as well, as in the above embodiment, by applying hydraulic pressure in the groove 29a, the cylindrical body 3
0 can be removed, and the elastic deformation of the cylindrical body 30 has the effect of suppressing chatter.

Further, in this embodiment, since the cylinder 30 is formed into a substantially tapered shape, there is no sudden change in the thickness of the cylinder 30, the internal stress during shrink fitting can be equalized, and the supporting rigidity of the tool can be improved.

In each of the above embodiments, the case where the cylindrical body is made of ceramic has been explained, but in the present invention, various materials can be selected for the cylindrical body.
It may be made of the same material as No. 2, and in this case as well, tool support accuracy can be maintained over a long period of time by replacing it.

[Effect of idea]

As described above, according to the structure of the tool attachment part of the spindle head according to the present invention, the cylinder body is attached to the spindle by shrink fitting and removed by hydraulic pressure. While improving accuracy, it is now possible to replace the cylindrical body when it wears out, allowing tool mounting accuracy to be maintained for a long period of time, and eliminating the need to replace the entire spindle, which has the effect of reducing costs. be.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining the structure of the tool attachment part of the spindle head according to the first embodiment of the present invention, FIG. 1 is a cross-sectional side view of the tool attachment part, and FIG. FIG. 3 is a perspective view of a vertical milling cutter to which the structure of the embodiment is applied, and FIG. 4 is a sectional side view of the tool attachment portion of the second embodiment of the present invention. In the figure, 10 is the spindle head, 12 is the spindle, 16 is the tool, 18 is the tool mounting part, 19, 29
is a cylinder support hole, 19a, 29a are grooves, 19b,
29b is a hydraulic passage, and 20 and 30 are cylindrical bodies.

Claims (1)

[Scope of utility model registration request] In a tool mounting structure of a spindle head in a machine tool in which a tool is attached by fitting a shank portion of the tool into a tapered hole formed at the tip of the spindle, a cylindrical support hole is provided at the tip of the spindle. A cylindrical body having a tapered hole that fits into the shank portion of the tool is installed in the support hole by shrink fitting, and the cylindrical body is formed so that the outer part in the axial direction has a slightly larger diameter than the inner part. The outer surface has a cylindrical shape with a stepped portion, and an annular groove is formed in a portion of the cylinder body support hole of the spindle corresponding to the stepped portion, and a hydraulic pressure supply passage is communicated with the groove. A tool mounting structure of a spindle head in a machine tool, characterized in that the body is removable.