JPH0794106B2 - Toolholder for overload torque and thrust detection - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool holder for predicting breakage of a drill, a tap or the like.

Conventional technology If cutting chips are not properly discharged during cutting with a drill etc., the cutting torque will increase and the drill will break, or if the drill is worn and processed at a constant feed rate, an excessive thrust force will be generated. Sometimes the drill buckled.

A device for detecting an excessive thrust load is disclosed in, for example, Japanese Patent Publication No. 63-28.
No. 742 is shown. This is a valve body equipped with a collet chuck at the tip is fitted in the tool holder so as to be slidable in the axial direction.
A switching valve is formed by the three pressure passages in the tool holder, and the thrust load is detected by operating the pressure switch connected to the pressure passage by the switching operation of the switching valve.

A device for detecting excessive torque is disclosed in, for example, Japanese Patent Laid-Open No. 59-1420.
No. 49 is shown. The phase detector detects a phase shift between a reference gear that rotates integrally with a main shaft and a displacement gear that is connected to the reference gear via an elastic displacement portion that twists with respect to cutting torque.

Problems to be Solved by the Invention As described above, since breakage of a drill or the like is caused by both overload torque and thrust, it is necessary to detect both of these. Although this object can be achieved by combining the two conventional techniques described above, separate detectors are required for detecting overload torque and overload thrust, and the structure is complicated.

Means for Solving the Problems In order to solve the above problems, according to the present invention, a holder main body having a taper shank is provided with a tool holding cylinder having a collet chuck at a tip thereof in a circumferential direction via an elastic member for torque transmission. In a tool holder that contacts to allow play and causes a rotational deviation between the holder main body and the tool holding cylinder when overload torque occurs, the tool holding cylinder is supported by the holder main body so as to be slidable in the axial direction. A thrust load setting spring is interposed between the holder body and the holder body, and a plurality of reference detectors provided on the outer circumference of the holder body at predetermined intervals in the circumferential direction and a plurality of displacement detectors provided on the tool holding cylinder are placed between each other. The length change in the circumferential direction with respect to the reference length when overload torque is generated between the two, and it is detected by the change means in the circumferential direction provided opposite to the rotation locus. Times A roll deviation detection area is formed, and further, when overload thrust occurs in the displacement detector and the tool holding cylinder moves axially,
The reference detector is circumferentially opposed to the reference detector, and the reference detector has a circumferential length different from the reference length, and its rotation locus forms a thrust detection area facing the detection means. It is characterized by including a detection display unit for thrust detection.

Action According to the above, when an overload torque is generated in the tool, a rotation deviation occurs between the tool holding cylinder and the holder body, and a rotation deviation detection area between the displacement detector and the reference detector that face each other in the circumferential direction is detected. The circumferential length of the tool changes, and this is detected by means of a change in the circumferential length of the detection area, such as a proximity switch, and when overload thrust occurs on the tool, the tool holding cylinder Along with the axial direction, the detection display for thrust detection of the displacement detector faces the reference detector in the circumferential direction, and a thrust detection area different from the reference length is formed between the two. Since the motion locus faces the detection means,
The thrust detection area can also be detected by the detection means. In this way, even if an overload is caused by either torque or thrust, it can be detected by one detecting means.

Embodiment As shown in FIG. 1, the holder body 1 has a taper shank 2a.
2, a grip portion 3 integrated with the main body 2, a support shaft 4 inserted slidably in the center of the main body 2, and a thrust load setting for urging the support shaft 4 forward (left in FIG. 1). Spring 5
Is equipped with. This spring 5 receives a thrust load generated in a tool 13 such as a drill of a tool holding cylinder described later, and does not bend axially rearward until a predetermined set thrust load is exceeded. A front end surface of the support shaft 4 is formed as a conical surface 6, a sleeve 7 is loosely fitted to the support shaft 4, and a rear end surface of the sleeve 7 is formed as a conical surface 8. These conical surfaces 6,
Large and small pivot ball bearings 9 and 10 for supporting 8 are fitted in a supporting cylinder 21 of a tool holding cylinder 20. The spacer 11 mounted on the support shaft 4 so as not to move axially forward and the collar portion 7a of the sleeve 7.
A spring 12 is interposed between the spring 12 and
Preload is applied to the pivot ball bearings 9, 10 via the two conical surfaces 6, 8 by the spring force of. 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. A collet chuck 23 for holding the tool 13 is attached to the front end of the support cylinder 21. A deep groove ball bearing may be used instead of the pivot ball bearing.

A connecting cylinder 24 is integrally screwed to the outer periphery of the support shaft 21, one end of a torsion coil spring 25 for torque transmission is connected to the connecting cylinder 24, and the other end of the spring is connected to the main body 2. As shown in FIG. 2, two upper and lower positioning pins 26 are planted in the connecting cylinder 24, and a locking ring 28 having a plurality of locking holes 27 that engages and disengages from the positioning pins 26 is provided on the main body 2. It is biased forward by a spring 29 interposed between the two. Therefore, the torsional strength of the torsion coil spring 25 is such that the detection ring 28 is moved backward (rightward in FIG. 1) against the spring force to disengage the engagement hole 27 and the positioning pin 26, and the bearing is supported in that state. It is adjusted by engaging the locking hole 27 of the detection ring 28 and the positioning pin 26 after rotating the cylinder 21 and the connecting cylinder 24 in the circumferential direction. As shown in FIG. 3, a plurality of recesses 30 are provided on the outer circumference of the detection ring 28.
(Three in this drawing) are cut and formed between three displacement detectors 31 at equal angular intervals (every angle θ (120 degrees) shown in FIG. 4) in the circumferential direction. As shown in FIG. 4, the displacement detector 31 has a detection display portion in which both edges in the rotation direction of the tool holder indicate detection start or detection end by the proximity switch 45 described later.
32 and 33. The detection display portion 33 is formed in a stepwise shape from the recess 30 and is a first detection display circumferentially opposed to a central protrusion 35 of a reference detector 34 described later when no overload thrust load is applied to the tool holding cylinder 20. It comprises a portion 33a and a second detection display portion 33b for thrust detection which faces the central protruding portion 35 of the reference detector 34 when the tool holding cylinder 20 is retracted in the axial direction by an overload thrust load. The second detection display portion 33b protrudes from the first detection display portion 33a on the opposite side in the rotational direction by twice the circumferential play (a in FIG. 4) between the reference detector 34 and the displacement detector 31. When an axial load is moved rearward due to an overload thrust load, a thrust detection area 38a is formed between the reference detection element 34 and the reference detection element 34 as shown in FIG. 4 (b).

The holder main body 2 is provided with three reference detectors 34 protruding from the holding portion 3 into the insides of the three recesses 30, and the reference detectors 34 and the displacement detectors 31 face each other. There is. As shown in FIG. 4, each of the reference detectors 34 has a stepped shape with the center protruding, and the one side surface 40a of the low step portion 40 and the detection display portion 32 are brought into contact with each other by the torsional force of the torsion coil spring 25. When there is a slight circumferential play between the other side surface 40b of the low step portion 40 and the facing detection display portion 33a (a in FIG. 4, absolute value 2a
The pulse count value corresponding to is larger than a set value t described later). Both edges in the rotation direction of the central protruding portion 35 are a pair of detection display portions 36, 37 indicating detection start or detection end by the proximity switch 45 described later, and a pair of detection display portions 36 between 120 degrees in the rotation direction. 37
And a pair of detection display portions 32 and 33a corresponding to the detection areas 38 and 39, respectively, are formed.
Three pairs of 8 and 39 are provided along the circumference. When no overload torque is applied, the circumferential lengths of the pair of detection areas 38, 39 and the central protrusion 35 and the circumferential lengths of the detection display portions 32 and 33a of the displacement detector 31 are all. Same reference length L (3
0 degree) is set.

The proximity switch 45 is arranged at a position for detecting the axial front part of the detection areas 38, 39 through the bracket 16 fixed to the front surface of the main spindle head 15 so as to face the rotation locus of the detection areas 38, 39.
The proximity switch 45 functions as a detection means for detecting a change in the circumferential length of the detection areas 38, 39. The proximity switch 45 also detects the thrust detection area 38a when an excessive thrust load is generated. When each detection area 38, 38a, 39 is detected,
The proximity switch 45 outputs an OFF signal.
The signal from the proximity switch 45 is sent to the overload torque (or thrust load) discriminating means 50 shown in FIG.

In the discriminating means 50, a signal 51 from the proximity switch 45 is averaged by a frequency-voltage converter 52 and a voltage-frequency converter 53, multiplied by a predetermined multiple, and a predetermined number of reference pulses are generated by one rotation of the spindle 17. The spindle angle pulse generator, 54 is a gate circuit that rises at the fall of the signal of the proximity switch 45 and falls at the rise (opens while the proximity switch 45 is OFF), 55 while the gate circuit 54 is open A counter for adding or subtracting the spindle angle pulse Ps inputted to the switch 56, 56 switches the addition or subtraction command to the counter 55 in one cycle of the ON / OFF signal of the proximity switch 45, and at the same time, compares the judgment command signal with the comparison command signal 57. An addition / subtraction switching circuit for outputting to 57, a comparison for judging whether the count value in the counter 55 exceeds a set value t preset by the setting circuit 58 when a judgment command is given. Reference numeral 59 is a reset circuit for resetting the counter 55 after the comparison circuit 57 makes a decision, and 60 is an output signal C for outputting an overload torque (or thrust) detection signal when the comparison result in the comparison circuit 57 exceeds a set value t. Is an output circuit that outputs as. The set value t is set by the proximity switch 45 in the pair of detection areas when there is no load before cutting.
The difference between the pulse count values of the counter 55 when 38 and 39 are detected is added with the allowable value. If there is no manufacturing error, the difference between the pulse count values in the pair of detection areas 38 and 39 is zero in this embodiment. Note that the spindle angle pulse Ps may use the encoder output of the motor for driving the spindle 17 instead. Also, the spindle angle pulse Ps
Instead of outputting a time pulse at a constant frequency,
Counting this with a counter, the pair of detection areas 38,
If the difference between the count values of 39 exceeds the set value t, an overload output signal may be output. In this case, the set value is the spindle
Since it depends on the rotation speed of 17, the correction for the rotation speed is necessary.

Now, according to the above-mentioned configuration, during normal cutting, the rotation of the holder shaft 1 is transmitted to the tool holding cylinder 20 via the torsion coil spring 25, and machining is performed. ON from the proximity switch 45,
The OFF signal is repeatedly output. It turns off in the detection area 38, during which the gate circuit 54 opens and the addition / subtraction switching circuit 56
When the spindle angle pulse Ps is added to the counter 55 based on the addition command of, and the proximity switch 45 detects the central protruding portion 35 and turns ON, the gate circuit 54 is closed and switched to subtraction.
When the proximity switch 45 detects the detection area 39 again and turns off, the spindle angle pulse Ps is subtracted from the pulse count value added in the counter 55, and the proximity switch 45 detects the displacement detector 31 and turns on. A command signal is output and the count value in the counter 55 is compared with the set value t. In the case of normal machining, since the torsion coil spring 25 causes the displacement detector 31 and the detection display portion 32 of the reference detector 34 and the one side surface 40a of the low step portion 40 to be in contact with each other, the lengths of the detection areas 38 and 39 are the same. Therefore, the count value in the counter 55 becomes zero,
No output signal for overload torque is issued.

When the sharpness of the tool 13 becomes poor, or when the torque exceeds the transmission torque set by the torsion coil spring 25 due to clogging of chips, the displacement detector 31 causes a rotation delay with respect to the reference detector 34, and is relatively moved. The reference detector 34 rotates by the play a shown in FIG. 4, and the side surface 40b of the low step portion 40 comes into contact with the detection display portion 33a. By this relative rotation, the circumferential length of the detection area 38 becomes L-a, and the circumferential length of the detection area 39 becomes L + a. Therefore, the result of addition in the detection area 38 and subtraction in the detection area 39 becomes -2a, and the absolute value thereof becomes larger than the set value t, so that the output circuit 60 outputs the output signal C due to the overload torque. In response to the output signal C of the overload torque, a stop command is output to the spindle drive motor, a step back operation is instructed, and a life counter for counting the output signal is provided. When the count value exceeds the predetermined number of times, the tool is replaced with a new tool that is the same as the tool even during machining. Depending on the detection timing of the proximity switch 45, it may add in the detection area 39 and subtract in the detection area 38. Even in this case, the absolute value of the comparison result (difference) is 2a. Overload will be detected. The discriminating means 50 may be processed by a computer as software.

In this way, in the determination of the overload due to the torque, a value twice the relative rotation amount (play) of the displacement detector 31 and the reference detector 34 is output as the comparison result, so the value of the relative rotation amount is extremely small. Even then, the overload torque is detected. Therefore, even when the transmission torque set by the torsion coil spring 25 is slightly exceeded, this can be instantly detected and the subsequent corresponding operation can be started.

Next, due to tool wear, only the overload thrust load is
The case of occurrence will be described with reference to FIG. The spring 5 does not bend backward until an overload thrust load exceeding the set thrust load by the spring 5 is generated in the tool 13, and the displacement detector 31 and the reference detector 34 have the relationship shown in FIG. 4 (a). . When an overload thrust load is generated on the tool 13, the support shaft 4 retracts with respect to the main body 2 together with the tool holding cylinder 20. As a result, the second detection display portion 33b of the displacement detector 31 faces the detection display portion 36 of the reference detection 34 in the circumferential direction, and a thrust detection area 38a is formed between the second detection display portion 33b and the reference display 34. Opposite 45. The length of the thrust detection area 38a in the circumferential direction is different from the reference length L (L-2a).
Therefore, if you add the spindle angle pulse PS in this thrust detection area 38a and subtract it in the detection area 39 (or vice versa), the other absolute values will be 2a, which is the same as in the case of overload detection by torque. Overload due to thrust is detected by comparison with the value t.

EFFECTS OF THE INVENTION As described above, according to the tool holder of the present invention, when an excessive torque is generated, the circumferential length of the rotational deviation detection area formed between the reference detector and the displacement detector is increased. Since it changes, it can be detected by the detection means that detects the change in the length of the detection area in the circumferential direction, which is arranged so as to face the rotation locus of the detection area, and when an excessive thrust occurs, The tool holding cylinder retracts with respect to the holder body,
The detection display section for thrust detection of the displacement detector faces the reference detector in the circumferential direction, and forms a thrust detection area different from the reference length between the reference detection element and the rotational locus of the thrust detection area. Since it is opposed to the means, it is possible to detect the overload caused by either the torque or the thrust by one detecting means, and it is possible to prevent the breakage of the tool by simplifying the configuration.

[Brief description of drawings]

FIG. 1 is a sectional view of a tool holder used in the device of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a sectional view taken along the line III-I of FIG.
II sectional view, FIG. 4 is a development view and operation view of the reference detector and the displacement detector along the entire circumference in the circumferential direction, and FIG. 5 is a block diagram of the discriminating means. 1 …… Holder body, 20 …… Tool holding cylinder, 25 …… Torsion coil spring, 31 …… Displacement detector, 32,33,36,37 …… Detection indicator, 34 …… Reference detector, 38,39 ...... Detection area, 38a ...... Thrust detection area, 45 ...... Proximity switch, 50 ...... Discrimination means

Claims (1)

[Claims] 1. A holder main body having a taper shank is connected to a tool holding cylinder having a collet chuck at its tip through an elastic member for torque transmission so as to allow a predetermined play in the circumferential direction, and an overload torque is exerted. In a tool holder in which a rotation deviation occurs between the holder body and the tool holding cylinder when it occurs, the tool holding cylinder is axially slidably supported on the holder body, and a thrust load setting spring is interposed between the tool holding cylinder and the holder body. Then, place a plurality of reference detectors on the outer circumference of the holder body in the circumferential direction at predetermined intervals and a plurality of displacement detectors on the tool holding cylinder, and place an overload torque between them. When generated, the length in the circumferential direction changes with respect to the reference length, and a rotation deviation detection area is formed which is detected by means for detecting the change in the length in the circumferential direction which is provided so as to face the rotation locus. The displacement detector includes When a load thrust occurs and the tool holding cylinder moves in the axial direction, it faces the reference detector in the circumferential direction and has a circumferential length different from the reference length between the reference detector and the reference detector. A tool holder for overload torque / thrust detection, comprising a detection display portion for thrust detection whose rotation locus forms a thrust detection area facing the detection means.