JPH0596451A - Tool holder - Google Patents

Abstract

PURPOSE:To decrease rotational deflection and resistance at the time of moving in an axial direction, of a tool holding unit during machining, in the case of a tool holder in which breaking of a tool can be predicted. CONSTITUTION:A tool holding unit 6 is movably supported respectively in circumferential and axial directions through a rolling bearing 204, which guides the tool holding unit 6 rolled in the axial direction and the direction of rotation, to a holder unit 2 of a tool holder 200. When overload torque and/or overload thrust are applied to a tool 4, the tool holding unit 6 is moved with the rolling bearing 204 in the direction of rotation or in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool holder that detects tool overload torque and tool overload thrust during cutting to predict tool breakage.

[0002]

2. Description of the Related Art As a conventional technique, Japanese Patent Laid-Open No. 63-245304 discloses a tool holder having a tool abnormality predicting device for predicting a tool abnormality during cutting with a drill or the like. According to this technique, as a method of supporting the tool holder on the tool holder so as to move in the rotational direction and the axial direction, the tool holder is axially moved via a slide bearing (needle-shaped rolling bearing) on the rotating holder body, And it is rotatably supported. The tool holder has a radial gap between it and the slide bearing so that it can move in the axial direction easily. It is designed to slide on. As another method, actual Kaihei 2-278
According to the one disclosed in Japanese Patent Publication No. 08-08, the tool holder is rotatably supported on the rotating holder body via the ball bearing, and a minute gap is provided between the inner ring of the ball bearing and the tool holder. The lubricating oil is fed into this gap to improve the sliding and to be movable in the axial direction.

[0003]

When a workpiece is cut by the tool holder as described above, a minute gap is formed between the tool holder and the bearing that supports the tool holder, which causes the rotating tool holder to swing and the tip to move. There was a problem that the tool attached to the machine would run out and deteriorate the machining accuracy. The clearance can be reduced to reduce the runout of the tool, but doing so increases the frictional resistance during sliding when the tool holder moves in the axial direction, which results in a slight overload torque generated during cutting. In addition, there is a possibility that a problem that the overload thrust cannot be detected may occur. Therefore, an object of the present invention is to improve the conventional support structure for a tool holder by reducing rolling resistance of the tool holder and frictional resistance during axial movement by rolling bearings interposed between the holder body and the tool holder. (EN) It is possible to obtain a tool holder that can improve accuracy and can minimize the adverse effect on tool abnormality prediction.

[0004]

In order to solve the above-mentioned problems, in a tool holder of the present invention, a tool holder is axially and rotationally guided through a rolling bearing for rolling and guiding the tool holder in the axial direction and the rotational direction. The tool is equipped with a conversion mechanism that converts the axial movement of the tool holder into a circumferential rotation between the tool holder and the holder body, and supports the tool at the tip of the tool holder. And the overload thrust is taken out as a predetermined amount of rotation deviation between the tool holder and the holder body.

[0005]

In the tool holder according to the present invention, the tool holder is supported by the rolling bearing mounted on the holder body so as to guide the rolling in the circumferential direction and the axial direction. Therefore, when the tool bearing is rotated by applying a preload to the rolling bearing. Can be reduced, and the resistance when moving in the axial direction can be reduced.

[0006]

1 and 2, a tool holder 200 of the present invention comprising a holder body 2 integrally connected to a spindle 1 of a machine tool and a tool holder 6 having a collect chuck 5 for holding a tool 4 at a tip thereof. explain. The holder body 2 has a tapered portion 2a, a grip portion 2b integral with the tapered portion 2a, and a cylindrical portion 201 protruding from the grip portion 2b to the front. Tube 2
In 01, a support shaft 203 of the tool holder 6 is supported in a support hole 202 formed in the center through a rolling bearing 204.

The rolling bearing 204 is a well-known one in which a large number of balls 204a are held by a retainer 204b having high steel property so as to be rotatable in any direction, and arranged in a spiral shape so as not to overlap in the circumferential direction. A part of the outer circumference of the ball 204a projects from the inner peripheral surface and the outer peripheral surface of the cage 204b. Each ball 204a is fitted into the support hole 202 and the support shaft 203 so as to roll in the axial direction and the circumferential direction along the inner peripheral surface of the support hole 202 and the outer peripheral surface of the support shaft 203,
As the balls 204a roll, the rolling bearing 20
The whole 4 is movable in the axial direction and the circumferential direction. In this way, the tool holder 6 is rollingly guided in the axial direction and the circumferential direction by the rolling bearing 204, so that the ball 204a has a minus clearance (preload) between the support hole 202 and the support shaft 203.
By providing the above, it is possible to eliminate the gap between the rolling bearing 204, the support shaft 203, and the support hole 202, to reduce the runout of the tool holding body 6 during processing, and when an overload thrust occurs. Can be smoothly moved in the axial direction.

A pressure contact block 206 is fitted in a central hole 205 in the holder body 2 continuing from the support hole 202 so as to be movable in the axial direction, and is arranged between a pull stud 207 screwed to the rear end of the holder body 2. A compression spring 208 for torque transmission is interposed in the pressure contact block 206, and the pressure contact block 206 urges the support shaft 203 forward through the steel ball 209, and the pressing force of the steel ball 209 causes the tool holder 6 to rotate the holder body 2. It is transmitted to. The spring force of the compression spring 208 is set so as to correspond to both the thrust load and the torque applied to the tool 4 and less than or equal to the smaller one of the maximum allowable thrust load and the maximum allowable torque.

At the rear end of the support shaft 203, as shown in FIG. 3, left and right cam grooves 211 are cut. As shown in FIG. 4, the shape of the cam groove 211 is formed so as to have a downward gradient toward the rear in the axial direction. Also, the holder body 2
A guide pin 210 is planted in the cylindrical portion 201 at a position facing the cam groove 211, and an inner end portion of the guide pin 210 is slidably fitted into the cam groove 211. Therefore, when these guide pins 210 are moved backward in the axial direction of the tool holder 6 by the cam grooves 211, the guide pins 210
The cam groove 211 is guided to the conversion mechanism 214 for moving the tool holder 6 in the circumferential direction.

Next, displacement detectors 216 are provided on the outer periphery of the rear end of the detection cylinder 215 which constitutes the tool holder 6 together with the support shaft 203 at intervals of 120 degrees in the circumferential direction. Further, reference detectors 217 are provided so as to protrude between the displacement detectors 216 from the grip portion 2b of the holder body 2 at 120 ° intervals in the circumferential direction. The reference detector 217 includes a low step portion 217a and a protruding portion 217b, and the low step portion 217a and the protruding portion 217 are provided.
The circumferential lengths of b and the displacement detector 216 are set to 30 degrees, respectively. When there is no overload thrust load or overload torque, the detection cylinder 215 is urged by the spring force of the compression spring 208 in the Z direction (the same as the rotation direction) of FIG. 5 via the conversion mechanism 214. Therefore, the low step portion 217a and the displacement detector 216 are kept in contact with each other. The position of the guide pin 210 at this time is the solid line position shown in FIG. 4 with respect to the cam groove 211. The proximity switch 35 for detecting the displacement detector 216 and the reference detector 217 is attached to a bracket 37 fixed to the front surface of the spindle head 36 as shown in FIG. The signal from the proximity switch 35 is sent to the overload torque / overload thrust discrimination means 40.

According to the above-mentioned configuration, during normal cutting, the rotation of the holder body 2 is transmitted to the tool holder 6 via the compression spring 208 to perform the machining, and the overload thrust and / or the overload torque is generated. Until the above, the displacement detector 216 and the reference detector 217 are relatively rotated with respect to the holder body 2 by the spring force of the compression spring 208 while maintaining the relationship of FIG. In this state, for example, the proximity switch 35 is turned on in the detection display portion 216c of the displacement detector 216, and the next reference detector 2
The distance while the detection display unit 217c of 17 is turned on again is constant at 60 degrees, and the overload signal is not output.

However, when an overload thrust load is applied to the tool 4 during machining, the steel ball 209 compresses the compression spring 208 via the pressure contact block 206, and the tool holder 6 retracts,
The conversion mechanism 214 guides the guide groove 211 along the guide pin 210, and the displacement detector 216 retracts and rotates in the direction opposite to the Z direction, so that a slip occurs between the steel ball 209 and the pressure contact block 206. Rolling bearing 2 at this time
The ball No. 04 of No. 04 rolls in the axial direction and the circumferential direction as the tool holder 6 moves backward, and the entire rolling bearing 204 also rotates backward. When the displacement detector 216 rotates in this way, the interval between the detection display portions 216c and 217c changes. Therefore, the change in this interval is captured and the steady-state value (60
If the value exceeds a preset allowable value, an overload signal is output. Further, when the overload torque is generated, the tool holder 6 rotates relative to the holder body 2, so that the displacement detector 216 rotates and retracts via the conversion mechanism 214, and the rolling bearing 204 has the same ball shape as described above. It retreats in the rolling direction of 204a.

Next, the tool holder 51 of the second embodiment will be described with reference to FIG. The tool holder 51 has a support shaft 3 integrated with the holder body 2 in which a tool holder 6 including a holding cylinder 9, a connecting cylinder 10 and a support cylinder 11 is fitted, and an upper outer periphery of the support shaft 3 and the support shaft 3. In the support hole 11a of the support cylinder 11 having an axial length corresponding to the upper part of the shaft 3,
Guide grooves (lead grooves) 12 that are inclined respectively with respect to the rotation axis of the tool holder 51 are provided facing each other, and a ball 13 is interposed between the guide grooves 12 to apply an overload thrust load to the tool 4. At this time, the conversion mechanism 1 for converting the axial movement of the tool holder 6 with respect to the holder body 2 into the circumferential rotation.
4 are configured. Also, the outer circumference of the lower part of the support shaft 3 and the holding cylinder 9
A rolling bearing 52 similar to that of the first embodiment is interposed between the inner circumferences of the above.

[0014]

As described above, according to the apparatus of the present invention, the tool holder can be moved in the circumferential direction and the axial direction through the rolling bearings that guide the tool holder in the axial direction and the circumferential direction. Since the support is provided, the tool holder can be smoothly rolled and guided in the axial direction and the circumferential direction even if a preload is applied to the rolling bearing. Therefore, it is possible to eliminate the gap between the rolling bearing and the tool holder, and to reduce the swing of the tool holding cylinder during processing, that is, the swing of the tool, thereby improving the processing accuracy. Further, during tool overload torque and overload thrust, the tool holder is rolled and guided by the rolling bearings, so the frictional resistance when moving in the axial direction is reduced, and a slight increase in overload torque and thrust can be detected. This has the effect of preventing breakage of a small diameter drill and extending the life of the drill.

[Brief description of drawings]

FIG. 1 is a front view of a tool holder according to an embodiment.

FIG. 2 is a sectional view of a tool holder according to an embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an explanatory diagram of a conversion mechanism of the embodiment.

FIG. 5 is a development view of the displacement detector of the tool holder and the reference detector of the embodiment in the entire circumference in the circumferential direction.

FIG. 6 is a sectional view of a second embodiment.

[Explanation of Codes] 2 Holder Body, 4 Tool, 6 Tool Holder, 20
0 tool holder, 204 rolling bearing, 204a ball, 204b retainer, 214 conversion mechanism, 21
6 displacement detector, 217 reference detector

Claims (1)

[Claims] 1. A tool holder is movably supported in a circumferential direction and an axial direction, respectively, via a rolling bearing for rolling and guiding the holder body in an axial direction and a rotation direction, and is provided between the tool holder and the holder body. Equipped with a conversion mechanism that converts the axial movement of the tool holder into a rotational movement in the circumferential direction, the overload torque and overload thrust applied to the tool at the tip of the tool holder can be rotated by a predetermined amount between the tool holder and the holder body. Tool holder designed to be taken out as a misalignment.