JPH0732982B2 - Tool holder support structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool holder that detects tool overload torque generated during cutting and predicts tool cutting.

Prior Art A similar technique is disclosed in Japanese Patent Publication No. 54-6102. According to this, the spindle is supported on the rotating tubular body through the deep groove ball bearing with a predetermined play in the circumferential direction, and the tubular body and the spindle are connected through the spring for torque transmission, When an overload torque is generated by a tool at the tip (for example, a drill), the spindle lags behind the cylinder,
This is taken out as the axial movement of the operating rod.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above technique, it is necessary to minimize the ratio of the friction torque of the bearing to the transmission set torque by the spring, particularly for predicting cutting loss of a very small diameter drill. is there. Since the preload applied to the bearing has a great influence on the friction torque, it is necessary to make the processing accuracy of the spindle supported by the cylindrical body and the bearing into which the deep groove ball bearing is fitted extremely high to give an appropriate preload. Not easy to make.

Means for Solving the Problems The present invention has an object to solve the above-mentioned problems, and a holder shaft tip portion having a taper shank and a rear end portion of a sleeve loosely fitted to the holder shaft are respectively formed in conical surfaces. However, these conical surfaces are supported by pivot ball bearings, the pivot ball bearings are fitted into the tool holding cylinder, and a spring for applying a preload is interposed between the holder shaft and the sleeve. To do.

Action The two conical surfaces receive a force in a direction in which they are separated from each other by the spring, and thereby a preload is applied to the pivot ball bearing, so that the preload can be adjusted by the spring force. Therefore, the preload for minimizing the friction torque can be easily applied to the pivot ball bearing, and as a result, a minute overload torque can be accurately detected.

Embodiment As shown in FIG. 1, a holder shaft 1 comprises a taper shank 2, a grip portion 3, and an intermediate shaft portion 4 projecting forward from the grip portion 3 and a support shaft portion 5. The tip end of the support shaft portion 5 is formed on the conical surface 6, a sleeve 7 is loosely fitted on the support shaft portion 5, and the rear end portion of the sleeve 7 is formed on the conical surface 8. Large and small pivot ball bearings 9 and 10 for supporting these conical surfaces 6 and 8 are fitted to a supporting cylinder 21 of the tool holding cylinder 20.
A spring 12 is interposed between a collar 11 mounted on the support shaft portion 5 immovably forward in the axial direction and a collar portion 7a of the sleeve 7, and the spring force of the spring 12 causes two conical surfaces 6 to be formed. Preload is applied to the pivot ball bearings 9, 10 via 8. This spring force is set so as to provide a preload that minimizes the friction torque generated by the pivot ball bearings 9 and 10.

As shown in FIG. 2, a diamond-shaped locking surface 15 is formed on the intermediate shaft portion 4 of the holder shaft 1, and the detection cylinder 22 that constitutes the tool holding cylinder 20 together with the support cylinder 21 has the diamond shape. Locking surface 15
An engaging hole 16 is formed on the opposite side of the engaging hole 16, and the engaging surface 15 is fitted in the engaging hole 16. The locking hole 16 and the locking surface 15 have a predetermined play (angle θ in FIG. 2) in the circumferential direction, which allows the tool holding cylinder 20 to rotate by a predetermined angle (θ) with respect to the holder shaft 1. is there. Since the rotation angle with respect to the holder shaft 1 is regulated inside the tool holding cylinder 20 in this way, chips and the like do not enter between the locking surface 15 and the locking hole 16,
The rotation of the predetermined angle θ is reliable for a long period of time.

A torque adjusting ring 25 is further loosely fitted to the intermediate shaft portion 4 so as to be movable in the axial direction and the circumferential direction. Torque adjustment ring
One end of a torsion coil spring 26 for torque transmission is connected to 25, and the other end of the spring is connected to the detection cylinder 22. The rear end portion of the torque adjusting ring 25 is fitted in the ring groove 3a formed in the grip portion 3 of the holder shaft 1. As shown in FIG. 4, a large number of locking holes 27 are formed in the torque adjusting ring 25 at a predetermined angle, and the locking pin 28 and the locking hole 28 are formed on the front surface of the grip portion 3 of the holder shaft 1. 27 and 27 form a locking means 29 that allows the torque adjusting ring 25 to be engaged with and disengaged from the holder shaft 1. Therefore,
If the locking pin 28 and the locking hole 27 are unlocked and the torque adjustment ring 25 is rotated and locked again, the torsion coil spring
Twist strength of 26 can be finely adjusted.

As shown in FIG. 4, cutouts are formed on the outer periphery of the grip portion 3 every 90 degrees.
31 is cut away, and the reference detector 32 is formed between them. A displacement detector 33 having an L-shaped cross section, which corresponds to these reference detectors 32, is provided on the outer circumference of the detection cylinder 22, and a gap 34 is provided between the displacement detectors 33. The reference detector 32 and the displacement detector 33 have the same circumferential length and the same outer diameter, but the torsional force of the torsion coil spring 26 causes the diamond-shaped engaging surface 15 of the holder shaft 1 to rotate. One set of opposite sides is a tool holding tube
When it is in contact with the locking holes 16 of 20, as shown in FIGS. 3 and 4, there is a phase shift in the circumferential direction between the detectors 32 and 33 by the angle θ. A collet chuck 24 holding a drill 23 is integrally attached to the tip of the tool holding cylinder 20.

Next, a bracket 41 is raised from the spindle head 40, and the bracket 41 detects the reference and displacement detectors 32 and 33 and outputs an ON signal, and the cutouts 31 and 34 output an OFF signal. Switches 42 and 43 are attached. Proximity switch
The signals of 42 and 43 are input to the AND element 45 via the knot element 44 and transmitted to the NC device 46. Reference numeral 47 denotes a spindle rotatably supported by the spindle head 40.

Such a tool holder is mounted on the spindle 47 and rotated. The rotation of the holder shaft 1 is transmitted to the tool holding cylinder 20 via the torque adjusting ring 25 and the torsion coil spring 26, and is used for drilling.
Rotate 23 and cut. An allowable torque according to the drill 23 is set by the torsion coil spring 26, and in the case of normal processing that does not exceed this allowable torque, the reference detector 32 and the displacement detector 33 rotate with a phase shift of the angle θ. . Therefore, the signals A and B from the proximity switches 42 and 43 are not turned off at the same time, and the overload signal C is not output (fifth
Figure). When the drill 23 wears, the cutting torque exceeds the allowable torque set by the torsion coil spring 26, and the holder shaft 1
Is a tool holding cylinder against the torsional strength of the torsion coil spring 26.
Rotate by an angle θ with respect to 20. At this time, since the preload applied to the pivot ball bearings 9 and 10 by the spring 12 is the minimum required, the frictional resistance due to the ball bearings 9 and 10 is small, and the cutting torque slightly exceeding the allowable torque is applied to the drill. twenty three
Even if this occurs, the holder shaft 1 can rotate with respect to the tool holding cylinder 20. As a result, the opposite side of the diamond-shaped locking surface 15 on the side not contacting the locking hole 16 in FIG. 2 contacts the locking hole 16. In this state, the reference and displacement detectors 32 and 33 have no phase shift, and the notches 31 and 34 also have no phase shift. Therefore, although the ON signal or the OFF signal is simultaneously output from the proximity switches 42 and 43, when the OFF signals are simultaneously output,
Since it is inverted by the knot element 44 and input to the AND element 45, the overload signal C is output from the AND element 45 to the NC device 46. The NC device 46 causes the spindle 47 to step back by this overload signal C, or counts the number of times the overload signal C is input to judge the life of the drill 23, and commands a tool exchange with the same tool before cutting. To do. Since the allowable torque according to the drill diameter is set on the holder side in this way, when the overload signal C is output, it means that the allowable torque has been exceeded, and the torque value is calculated and estimated as in the conventional case. , No need to compare with normal values.

As described above, according to the device of the present invention, the tool holding cylinder is supported on the holder shaft through the pivot ball bearing, and the preload is applied to the pivot ball bearing by the spring and the sleeve arranged between the pivot ball bearings. Therefore, the preload for minimizing the friction torque of the bearing can be easily applied to the pivot ball bearing by the spring strength of the spring. As a result, the friction torque of the pivot ball bearing can be minimized, and even if the drill at the tip of the tool holding cylinder has an extremely small diameter and a slight overload torque is generated, this can be It can be taken out accurately as a rotation delay.

[Brief description of drawings]

1 is a sectional view of a tool holder according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a sectional view taken along the line III-III of FIG. 1, and FIG. -IV sectional view and FIG. 5 show a relationship diagram of detection signals. 1 ... Holder shaft, 2 ... Taper shank, 6, 8 ... Conical surface,
7 ... Sleeve, 9, 10 ... Pivot ball bearing, 12 ... Spring, 15 ... Locking surface, 16 ... Locking hole, 20 ... Tool holding cylinder, 25 ... Torque adjusting ring, 26 ... Torsion coil spring 26, 29 ... Engagement Stop means, 32 ... Reference detector, 33 ... Displacement detector

Claims (1)

[Claims] 1. A holder for holding a tool holding cylinder so that the allowable torque is set by a torque transmitting spring and the tool holding cylinder rotates a predetermined angle with respect to a holder shaft when the cutting torque exceeds the set allowable torque. A tool holder supported on a shaft to detect overload torque, wherein the tip of the holder shaft and the rear end of a sleeve loosely fitted to the holder shaft are formed into conical surfaces, and the conical surfaces are formed. A support structure for a tool holding cylinder, in which a pivot ball bearing for supporting a bearing is fitted into a tool holding cylinder, and a spring is interposed between a holder shaft and a sleeve to apply a preload to the pivot ball bearing.