JP2783052B2 - Tool holder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 63-245304 discloses a conventional tool holder provided with a tool abnormality prediction device for predicting a tool abnormality during cutting by a drill or the like. According to this technique, as a method of supporting the tool holder in the tool holder so as to move in the rotation direction and the axial direction, the tool holder is axially moved to the rotating holder body via a slide bearing (needle rolling bearing). And it is rotatably supported. The tool holder has a radial gap between the slide bearing and the slide bearing so that it can move easily in the axial direction. To slide. As another method, Japanese Utility Model Laid-Open No. 2-278
According to the technology disclosed in Japanese Patent Application Publication No. 08-108, a tool holder is rotatably supported on a rotating holder via a ball bearing, and a minute gap is provided between the inner ring of the ball bearing and the tool holder. In addition, lubricating oil is supplied into the gap to improve the slip and make it possible to move in the axial direction.

[0003]

When a workpiece is cut with the above-described tool holder, there is a minute gap between the tool holder and the bearing supporting the tool holder. There was a problem that the run-out of the tool attached to the machine caused the machining accuracy to deteriorate. To reduce the runout of the tool, the clearance should be reduced, but this will increase the frictional resistance during sliding when the tool holder moves in the axial direction, resulting in a slight overload torque generated during cutting. In addition, there may be a problem that the overload thrust cannot be detected. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the conventional support structure of the tool holder and reduce the run-out of the tool holder and the frictional resistance during axial movement by a rolling bearing interposed between the holder body and the tool holder. An object of the present invention is to provide a tool holder that can improve accuracy and minimize the adverse effect on tool abnormality prediction.

[0004]

According to the present invention, there is provided a tool holder for rolling a tool holder in a circumferential direction by a rolling bearing which guides a tool holder to a holder body in an axial direction and a rotational direction. respectively movably supported on direction, provided with a conversion mechanism for converting the axial movement of the tool holder in the circumferential direction rotation between the tool holder and the holder body, further the converter
The structure is the holder of the tool holder when overload torque occurs.
Is configured to allow relative rotation in the circumferential direction with respect to the body.
The overload torque and overload thrust applied to the tool at the tip of the tool holder are taken out as a predetermined amount of rotational deviation between the tool holder and the holder.

[0005]

In the tool holder of the present invention, since the tool holder is supported by the rolling bearing mounted on the holder body so as to roll and guide in the circumferential direction and the axial direction, a preload is applied to the rolling bearing to rotate the tool holder. And the resistance when moving in the axial direction can be reduced.

[0006]

1 and 2, a tool 4 is held at a tip end of a holder body 2 which is integrally connected to a spindle 1 of a machine tool.
The tool holder 200 of the present invention including the tool holder 6 provided with the collet chuck 5 will be described. The holder body 2 has a tapered portion 2a, a grip portion 2b integrated with the tapered portion 2a, and a tubular portion 201 protruding forward from the grip portion 2b. Tube part 2
In reference numeral 01, a support shaft 203 of the tool holder 6 is supported via a rolling bearing 204 in a support hole 202 formed at the center.

The rolling bearing 204 is a well-known rolling bearing in which a large number of balls 204a are rotatably held in arbitrary directions by a high steel retainer 204b, and are arranged in a spiral so as not to overlap in the circumferential direction. Part of the outer periphery of the ball 204a protrudes from the inner and outer peripheral surfaces of the retainer 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,
The rolling bearing 20 is caused by the rolling of each ball 204a.
4 as a whole is movable in the axial direction and the circumferential direction. As described above, the tool holder 6 is guided to roll 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.
, The clearance between the rolling bearing 204 and the support shaft 203 and the support hole 202 can be eliminated, the run-out of the tool holder 6 during machining can be reduced, and when overload thrust occurs. Can be smoothly moved in the axial direction.

A press-contact block 206 is fitted in a center hole 205 in the holder body 2 continuous with the support hole 202 so as to be movable in the axial direction, and is located between a press stud 207 screwed to the rear end of the holder body 2. A compression spring 208 for transmitting torque is interposed between the tool holder 6 and the pressing block 206 urges the support shaft 203 forward through the steel ball 209 to rotate the holder body 2 with the pressing force of the steel ball 209. To be communicated. The spring force of the compression spring 208 is set to be equal to or smaller than the smaller of the maximum allowable thrust load and the maximum allowable torque so as to correspond to both the thrust load and the torque applied to the tool 4.

At the rear end of the support shaft 203, cam grooves 211 are formed on the left and right as shown in FIG. As shown in FIG. 4, the shape of the cam groove 211 is formed so as to have a downward slope toward the rear in the axial direction. Further, the holder body 2
Guide pins 210 are respectively implanted at positions opposed to the cam grooves 211 in the cylindrical portion 201, and the inner ends of the guide pins 210 are slidably fitted into the cam grooves 211. Accordingly, when the tool holder 6 is moved backward in the axial direction by the guide pins 210 and the cam grooves 211, the guide pins 210
A conversion mechanism 214 in which the tool holder 6 is moved in the circumferential direction while the cam groove 211 is guided by the cam groove 211 is formed. Also, this conversion
The mechanism 214 holds the tool when overload torque is generated.
The relative rotation of the body 6 with respect to the holder body 2 is allowed.
ing.

Next, on the outer periphery of the rear end of the detection cylinder 215 which forms the tool holder 6 together with the support shaft 203, displacement detectors 216 are provided at 120 ° intervals in the circumferential direction. Further, a reference detector 217 is projected forward from the grip portion 2b of the holder body 2 at intervals of 120 degrees in the circumferential direction so as to face between the displacement detectors 216. The reference detector 217 includes a low step portion 217a and a protrusion 217b.
The circumferential lengths of b and the displacement detector 216 are each set to 30 degrees. When there is no overload thrust load or overload torque, the detection cylinder 215 is urged in the Z direction (same as the rotation direction) in FIG. 5 by the spring force of the compression spring 208 via the conversion mechanism 214. Therefore, the state where the low step portion 217a and the displacement detector 216 are in contact with each other is maintained. The position of the guide pin 210 at this time is the position indicated by the solid line in FIG. As shown in FIG. 1, one proximity switch 35 for detecting the displacement detector 216 and the reference detector 217 is mounted on a bracket 37 fixed to the front surface of the spindle head 36. The signal from the proximity switch 35 is sent to the overload torque and overload thrust discriminating means 40.

According to the above-described 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 are applied to the tool 4. Until the displacement, the displacement detector 216 and the reference detector 217 rotate relative to the holder body 2 while maintaining the relationship of FIG. In this state, for example, the proximity switch 35 is turned on at the detection display unit 216c of the displacement detector 216, and the next reference detector 2 is turned on.
The distance during which the detection display unit 217c turns ON again is constant at 60 degrees, and no overload signal is 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 retreats.
The guide groove 211 is guided along the guide pin 210 by the conversion mechanism 214, and the displacement detector 216 rotates in the direction opposite to the Z direction while retreating, so that a slip occurs between the steel ball 209 and the pressure contact block 206. At this time, rolling bearing 2
The ball 204a of 04 rolls in the axial direction and the circumferential direction with the retreat of the tool holder 6, and the entire rolling bearing 204 also retreats. When the displacement detector 216 rotates in this manner, the interval between the detection display sections 216c and 217c changes.
), And outputs an overload signal when the value deviates from a preset allowable value. Further, when an overload torque is generated, the tool holder 6 rotates relative to the holder body 2, so that the displacement detector 216 retreats while rotating via the conversion mechanism 214, and the rolling bearing 204 becomes the ball as described above. 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 includes a support shaft 3 integrated with the holder body 2 and a tool holder 6 including a holding tube 9, a connection tube 10 and a support tube 11 fitted therein. A support hole 11a of a support cylinder 11 having an axial length corresponding to the upper part of the shaft 3;
Guide grooves (lead grooves) 12 that are inclined with respect to the rotation axis of the tool holder 51 are formed in opposition to each other, and a ball 13 is interposed between the guide grooves 12 to apply an overload thrust load to the tool 4. The conversion mechanism 1 converts the axial movement of the tool holder 6 with respect to the holder body 2 to the rotation in the circumferential direction.
4 are configured. The outer periphery 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.

[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 via the rolling bearings that guide the tool holder in the holder body in the axial direction and the circumferential direction. Since the support is supported, the tool holder can be smoothly rolled and guided in the axial direction and the circumferential direction even when a preload is applied to the rolling bearing. Therefore, the gap between the rolling bearing and the tool holder can be eliminated, and the runout of the tool holding cylinder during processing, that is, the runout of the tool can be reduced, thereby improving the processing accuracy. Also, when the tool is overloaded and the overload thrust, the tool holder is guided by the rolling bearings, so that the frictional resistance when moving in the axial direction is reduced, and it is possible to detect subtle overload torque and increased thrust. It has the effect of preventing breakage of small diameter drills and extending the life of drills.

[Brief description of the 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 the embodiment.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

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

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

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

[Explanation of symbols]

2 holder body, 4 tools, 6 tool holder, 20
0 tool holder, 204 rolling bearing, 204a ball, 204b retainer, 214 conversion mechanism, 21
6 Displacement detector, 217 reference detector

────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Publication No. 3-46242 (JP, B2) Japanese Utility Model Publication No. 4-13045 (JP, Y2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B23Q 17/09 B23B 31/38 B23Q 3/12

Claims (1)

(57) [Claims] 1. A tool holder is movably supported in a circumferential direction and an axial direction via rolling bearings for rolling and guiding a tool holder in a holder body in an axial direction and a rotation direction, and is provided between the tool holder and the holder body. comprising a conversion mechanism for converting the axial movement of the tool holder in the circumferential direction rotation, further the conversion mechanism, the overload torque
Circumference of the tool holder with respect to the holder body when cracks occur
A tool holder configured to allow relative rotation of the tool holder and an overload torque and an overload thrust applied to the tool at the tip of the tool holder as a predetermined amount of rotation deviation between the tool holder and the holder body.