JPH06344208A - Tool holding structure of machine tool - Google Patents

Abstract

PURPOSE:To accurately and easily mount a tool by making a mounting part of the tool in an approximately truncated conical shape, and positioning a holding ball and an opening part of the holding groove and a holding recess on the outer circumferential tapered surface on the tip side at a cylindrical fitting part. CONSTITUTION:A tool 22 is arranged to the lower part of a main spindle 21. A locking member 27 is moved downward against the energizing force of a spring 28 by the pressure oil to be supplied to a cylinder 29. A mounting part 32 is fitted to a holding recessed part 23 of a main spindle 21 by elevating the tool 22. The mounting part 32 is of approximately truncated conical shape, and the tip side is thin, and the shaft center of the tool 22 need not be positioned with high accuracy relative to the shaft center of the main spindle 21. After fitting, the pressure oil of the cylinder 29 is discharged, the locking member 27 is moved upward, and a holding ball 26 is pressed by a projecting part 30 of the locking member 27 to advance in the holding recessed part 23, and engaged with the holding groove 33 of the tool 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool holding structure for a machine tool, and more particularly to a tool holding structure for a machine tool such as a machining center in which a tool such as a grindstone or a drill is replaced.

[0002]

2. Description of the Related Art Generally, in a machine tool such as a machining center, as shown in FIG. 4, a tool for holding a mounting portion 4 for a tool 3 in a holding recess 2 formed in a tip end surface of a spindle 1 of a machine tool body. A holding structure is adopted. Conventionally, such a tool holding structure is shown in FIGS. 5 and 6.

In the structure shown in FIG. 5, the holding recess 2 is formed in a tubular shape, and a plurality of cutout holes 5 are evenly formed in the side wall in the circumferential direction. A holding ball 6 is provided in each notch hole 5.
Are arranged respectively, and can be moved back and forth in the holding recess 2. The holding ball 6 is moved by a lock member 7 slidably mounted on the main shaft 1. A cylindrical mounting portion 4a of the tool 3 is fitted in the holding recess 2 and a holding groove 8 for engaging and disengaging the holding ball 6 is formed on the outer periphery of the mounting portion 4a. There is. Therefore, when the mounting portion 4a is fitted in the holding recess 2 and the lock member 7 is slid upward, the holding ball 6 is pushed by the tip of the lock member 7 and advances into the holding recess 2 for holding. The tool 3 is retained in the groove 8 by being retained in the groove 8.

On the other hand, in the structure shown in FIG. 6, the holding recess 2 is formed in a truncated cone shape, and a central hole 9 is formed in the center of the bottom surface thereof, while the mounting portion 4 corresponds to the holding recess 2. It is formed in the shape of. In this structure, when the tapered mounting portion 4b is fitted into the holding concave portion 2, the shaft portion 10 provided in the central portion is inserted into the central hole 9 of the holding concave portion 2 and pulled, so that the tool 3 is rotated. It is designed to be held at.

In both holding structures, when the honing grindstone 11 is used for the tool 3, the air microsensor 12 can detect the distance between the grindstone 11 and the grinding surface 13. That is, the honing stone 11
A hole 14 for a sensor, which is connected by the upper end surface of the mounting portion 4 of the tool 3 and the bottom surface of the holding concave portion 2, is opened between them. Then, by supplying air from the main shaft 1 side and blowing the air toward the grinding surface 13, the air microsensor 12 detects the pressure value that changes depending on the distance from the grinding surface 13.

[0006]

However, in the tool holding structure shown in FIG. 5, in order to mount the tool 3 on the spindle 1, high positioning accuracy is required between the cylindrical mounting portion 4a and the holding recess 2. It That is, since the outer diameter of the mounting portion 4a and the inner diameter of the holding recess 2 are substantially the same diameter so that the fitted state can be maintained, the tool 3 is attached if there is a misalignment between the axes of the two during positioning. There is a problem that you can not.

Further, in the tool holding structure shown in FIG. 6, the holding concave portion 2 and the mounting portion 4 are formed with a conical surface. However, it is very difficult to machine such a conical surface so that the entire surface is brought into contact with each other, and the accuracy is high. It's hard to put out. Moreover, when the mounting portion 4 is fitted in the holding recessed portion 2, the conical surface is in full contact, so processing should be performed so that no gap is created between the bottom surface of the holding recessed portion 2 and the tip surface of the mounting portion 4. Is even more difficult. Therefore, even if an attempt is made to connect the sensor hole 14 to the tip end surface of the mounting portion 4, the connected state of the sensor hole 14 deteriorates and air leakage occurs, so that the distance between the grindstone 12 and the processed surface 13 is increased. There is a problem that can not be measured accurately. The present invention has been made in view of the above problems, and an object of the present invention is to provide a tool holding structure for a machine tool in which a tool can be attached accurately and easily.

[0008]

According to the present invention, in order to achieve the above object, a holding recess is formed in a spindle end surface of a machine tool main body, and a tool mounting portion is fitted into the holding recess.
In a tool holding structure of a machine tool for holding the tool on the spindle, a holding ball is provided on the inner side wall of the holding recess so as to be able to move back and forth from the inner side wall to the holding recess.
The mounting portion of the tool is formed into a substantially truncated cone shape, and a holding groove for engaging and disengaging the holding ball is formed in the tapered outer peripheral portion of the mounting portion, and the body is fitted into the opening of the holding recess. A cylindrical fitting portion is formed. Further, a sensor hole may be formed in the machined portion of the tool from the spindle side, and the sensor hole may be connected between the bottom surface of the holding recess and the end surface of the mounting portion.

[0009]

According to the present invention, when the tool is attached to the spindle of the machine tool main body, the tool mounting portion is formed in a substantially truncated cone shape, so that the spindle and the tool do not have to be exactly aligned with each other. Easily fits into the holding recess. Then, when the lock member is moved upward to move the holding ball into the holding recess, the holding ball is positioned in the holding groove of the tapered mounting portion on the distal end side and has a cylindrical shape on the base side. The joint portion is located in the holding recess and holds the tool on the spindle. Further, the tool is also pressed upward by the holding ball, the end surface of the mounting portion is pressed against the bottom surface of the holding recess, and the sensor hole is tightly connected.

[0010]

Embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing a tool holding structure, in which 21 is a spindle and 22 is a tool. As shown in FIG. 2, a cylindrical holding recess 23 is formed on the tip end surface of the main shaft 21. The bottom surface of the holding recess 23 has a sensor hole 24a.
However, a plurality of cutout holes 2 are equally divided in the circumferential direction on the inner surface.
5 is provided, and holding balls 26 are provided in the respective cutout holes 25.

As shown in FIG. 3, a substantially cylindrical lock member 27 is slidably mounted on the outer peripheral portion of the tip of the main shaft 21. The lock member 27 is biased upward by a spring 28 and is moved downward by increasing the hydraulic pressure in the upper pressure chamber 29.

An annular projection 30 is formed on the inner peripheral surface of the lock member 27, and the tip of the projection 30 is an inclined surface that gradually widens upward.
As a result, when the lock member 27 is slid upward, the inclined surface of the protruding portion 30 presses the holding ball 26 so that it can advance into the holding recess 23. Since the diameter of the cutout hole 25 is slightly larger than the outer diameter of the holding ball 26, the holding ball 26 is locked by the locking member 27.
It is pressed slightly upward by the upward movement.

For the tool 22, for example, a honing head is used. This honing head is a conventionally known one in which a plurality of grindstones 31 are arranged on the outer peripheral portion of the tip.
These grindstones 31 swell in the outer peripheral direction by spring force, hydraulic pressure, etc., and perform honing of the work W by rotating and reciprocating the main shaft 21.

The upper end of the tool 22 has a mounting portion 32.
Has become. The mounting portion 32 has a substantially frustoconical shape, a holding groove 33 is formed on the tapered outer peripheral surface, and the body portion has a cylindrical fitting portion 34 that fits into the opening of the holding recess 23.
Has become. The mounting portion 32 has an end face and a grindstone 3
A sensor hole 24b connecting between the two is formed. The sensor hole 24b is provided on the tip surface of the mounting portion 32 and the holding recess 2
When the bottom surface of 3 is brought into pressure contact, it communicates with the sensor hole 24a provided on the main shaft 21 side. An O-ring 35 is provided on the end surface of the mounting portion 32 to prevent air leakage from the connecting portion of the sensor holes 24a and 24b. A fitting recess 36 is formed in the opening of the main shaft 21 to allow the mounting portion 3 of the tool 22 to be mounted.
By engaging a transmission pin 37 projectingly provided on the outer peripheral portion of the two, both are integrally rotated.

In the tool holding structure having the above structure, the tool 22 is attached to the spindle 21 as follows. That is, first, the tool 22 is arranged below the spindle 21. At this time,
The lock member 27 is moved downward against the biasing force of the spring 28 by the pressure oil supplied to the cylinder 29. Then, by raising the tool 22, the mounting portion 32 is fitted into the holding recess 23 of the spindle 21. In this case, since the mounting portion 32 has a substantially frustoconical shape and the tip side is thin, it is necessary to position the axis of the tool 22 with respect to the axis of the main shaft 21 with high accuracy as shown in FIG. Absent.

When the tool 22 is further raised and the mounting portion 32 is inserted into the holding concave portion 23, the cylindrical fitting portion 34 is fitted to the inner peripheral surface of the holding concave portion 23 on the opening side. Therefore, by discharging the pressure oil from the cylinder 29, the lock member 27 is moved upward by the urging force of the spring 28. As a result, the protrusion 3 of the lock member 27
At 0, the holding ball 26 is pressed to advance into the holding recess 23 and engage with the holding groove 33 of the tool 22. At this time, the tool 22 is also pressed upward by the holding balls 26, and the end surface of the mounting portion 32 comes into pressure contact with the bottom surface of the holding recess 23. As a result, the sensor holes 24 are tightly connected, and gas leakage can be sufficiently prevented. When the tool 22 is replaced, the lock member 27 is moved downward by the hydraulic pressure of the cylinder 29, the holding ball 26 is retracted from the holding groove 33, and the tool 22 is removed. The tool 22 may be attached.

[0017]

As is apparent from the above description, according to the tool holding structure for a machine tool of the present invention, the tool mounting portion has a substantially truncated cone shape, and the holding ball and the tip side tapered outer peripheral surface are held. Since the positioning is done by the groove for use and the opening of the holding recess and the cylindrical fitting part, the high accuracy of positioning required for mounting the spindle in the holding recess is not required, and automation is possible and the mounting part The outer circumference does not touch the entire surface and the mounting accuracy is good. Further, since the end surface of the mounting portion can be pressed against the bottom surface of the holding recess by the holding ball, the sensor hole is connected well, and gas leakage is eliminated. As a result, the accuracy of measurement by the air microsensor is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a tool holding structure of a machine tool according to this embodiment.

FIG. 2 is a partial cross-sectional view showing a state before the lock member exterior of FIG.

FIG. 3 is a partial cross-sectional view of FIG.

FIG. 4 is a side view showing a tool holding structure of a machine tool according to a conventional example.

5 is a partial cross-sectional view of FIG.

FIG. 6 is a partial cross-sectional view showing a tool holding structure according to another conventional example.

[Explanation of symbols]

21 ... Spindle, 22 ... Tool, 23 ... Holding recess, 26 ... Holding ball, 32 ... Mounting part, 33 ... Holding groove, 34 ... Fitting part.

Claims (2)

[Claims] 1. A tool holding structure for a machine tool, wherein a holding recess is formed on an end face of a spindle of a machine tool body, and a tool mounting portion is fitted into the holding recess to hold the tool on the spindle. In the above, the holding ball is arranged on the inner side wall of the holding recess so as to be able to move back and forth from the inner side wall to the holding recess, while the mounting part of the tool has a substantially truncated cone shape, and the tip side tapered outer peripheral part of the mounting part is A tool holding structure for a machine tool, characterized in that a holding groove for engaging and disengaging the holding ball is formed in the body, and a cylindrical fitting portion that fits into the opening of the holding recess is formed in the body portion. 2. A sensor hole is bored in the machined portion of the tool from the spindle side, and the sensor hole is connected between the bottom surface of the holding recess and the end surface of the mounting portion. Item 1. A tool holding structure for a machine tool according to Item 1.