JPH04193459A - Tool holder for detecting overload torque and thrust - Google Patents

Abstract

PURPOSE:To detect both of an overload torque and overload thrust load by one detector, by equipping plural reference detecting elements provided on the holder main body outer periphery, a displacement detecting element provided on a tool holding cylinder, and a detection display part for detecting thrust on the displacement detecting element. CONSTITUTION:In the case of torque exceeding the transmission torque set by a twist coil spring, a displacement detecting element 31 causes a rotation delay for a reference detecting element 34, and the side face 40b of a lower step part 40 is abutted on a detection display part 33a with the reference detecting element 34 being rotated by play (a) relatively. By this relative turning the length in the circumferential direction of a detection zone 38 becomes at value L-a, also the length in the circumferential direction of a detection zone 39 at value L+a. In the case of an overload thrust load being caused on a tool, a support shaft is retreated to the main body together with a tool holding cylinder. Consequently the 2nd detection display part 33b of the displacement detecting element 31 is opposed in the circumferential direction to the detection display part 36 of the reference detection 34, a thrust detection zone 38a is formed between the both, and the turning locus thereof is opposed to a proximity switch 45.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a tool holder for predicting breakage of drills, taps, etc.

Conventional technology If chips are not discharged properly during cutting using a drill, etc., the cutting torque will increase and the drill will break, or if the drill is worn out and machining at a constant speed, excessive thrust force will be generated. This could cause the drill to buckle.

Excessive thrust load detection equipment is available, for example, in
No. 28742. In this system, a valve body with a collet chuck at the tip is fitted into a tool holder so that it can slide in the axial direction, and forms a switching valve with three pressure passages inside the tool holder. The thrust load is detected by operating a pressure switch connected to the passage.

In addition, a test device with excessive torque can be used, for example, in Japanese Patent Application Laid-open No.
No. 42049. This uses a phase detector to detect the phase shift between a reference gear that rotates integrally with the main shaft and a displacement gear that is connected to the reference gear via an elastic displacement part that causes twisting in response to cutting torque. be.

Problems to be Solved by the Invention As mentioned above, breakage of drills and the like occurs due to both overload torque and thrust, so it is necessary to detect both of these. Although this objective can be achieved by combining the two prior art techniques described above, separate detectors are required for detecting overload torque and overload thrust, and the structure becomes complicated.

Means for Solving the Problems In order to solve the above problems, in the present invention, a tool holding cylinder having a collet chuck at the tip is attached to a holder body having a tapered shank in a predetermined direction in the circumferential direction via an elastic member for transmitting torque. In a tool holder that is connected to allow play and that causes rotational deviation between the holder body and the tool holding cylinder when overload torque is generated, the tool holding cylinder is supported on the holder body so as to be slidable in the axial direction, and the tool holding cylinder is A thrust load setting spring is interposed between the holder body and the holder body, and a plurality of reference detectors provided at predetermined intervals in the circumferential direction on the outer periphery of the holder body and a displacement detector provided on the tool holding cylinder are placed between each other. The rotational deviation detection area is formed between the displacement detector and the displacement detector, and the displacement detector is provided with a thrust detector that faces the reference detector in the circumferential direction due to the axial movement of the tool holding cylinder when overload thrust occurs. It is characterized by having a detection display section.

According to the above, when overload torque occurs in the tool, a rotational deviation occurs between the tool holding cylinder and the holder body, and the rotational deviation is detected between the displacement detector and the reference detector, which face each other in the circumferential direction. Since the circumferential length of the area changes, this is detected by a detection means such as a proximity switch and the occurrence of excessive torque is known. Additionally, when an overload thrust occurs on the tool, the tool holding cylinder moves backward in the axial direction with respect to the holder body, and the detection display section for thrust detection of the displacement detector faces the reference detector in the circumferential direction. The occurrence of excessive thrust can be detected from the thrust detection area formed in the circumferential direction between the detection display section and the reference detector.

Embodiment As shown in FIG. 1, a holder body 1 has a tapered shank 2.
a main body 2, a grip part 3 integrated with the main body 2, a support shaft 4 inserted through the center of the main body 2 so as to be slidable in the axial direction;
It is equipped with a thrust load setting spring 5 that urges forward (leftward in FIG. 1). This spring 5 receives a thrust load generated on a tool 13 such as a drill in a tool holding cylinder, which will be described later.
It will not deflect backward in the axial direction until it exceeds a certain set thrust load. The front end surface of the support shaft 4 is formed into a conical surface 6, and a sleeve 7 is loosely fitted onto the support shaft 4.
The rear end surface is formed into a conical surface 8.

Large and small pivot ball bearings 9.1o that support these conical surfaces 6.8 are fitted into the support tube 21 of the tool holding tube 20, and a spacer is attached to the support shaft 4 so as not to be able to move forward in the axial direction. 11 and the flange 7a of the sleeve 7 is a spring 1.
2 is interposed, and the spring force of this spring 12 applies a preload to the pivot ball bearing 9.10 via the two conical surfaces 6.8. This spring force is set to provide a preload that minimizes the friction torque caused by the pivot ball bearings 9 and 1o. A collet chuck 23 for holding the tool 13 is attached to the front end of the support cylinder 21.

Note that a deep groove ball bearing may be used instead of the pivot ball bearing.

A connecting tube 24 is integrally screwed onto the outer periphery of the supporting tube 21. One end of a torsion coil spring 25 for transmitting torque is connected to the connecting tube 24, and the other end of the spring is connected to the main body 2. As shown in FIG. 2, two positioning pins 26 (upper and lower) are implanted in this connecting cylinder 24, and a locking ring 28 having a number of locking holes 27 that engages and disengages with the positioning pins 26 is attached to 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 can be determined by moving the detection ring 28 backward (to the right in Figure 1) against the spring force to disengage the locking hole 27 and the positioning pin 26, and then supporting it in that state. After rotating the cylinder 21 and the connecting cylinder 24 in the circumferential direction, adjustment is made by engaging the locking hole 27 of the detection ring 28 with the positioning pin 26. As shown in FIG. 3, a plurality of recesses 30 (three in this figure) are cut out on the outer periphery of the detection ring 28, and the recesses 30 are spaced at equal angular intervals in the circumferential direction (angle θ (as shown in FIG. 4)). Three displacement detectors 31 are formed at 120 degree intervals). As shown in FIG. 4, the displacement detector 31 has a detection display section 3 at which both edges of the tool holder in the rotational direction indicate the start or end of detection by a proximity switch 45, which will be described later.
It is 2.33.

The detection display section 33 is formed in a stepped shape from the recess 30, and is a first detection display that faces a central protrusion 35 of a reference detector 34, which will be described later, in the circumferential direction when no overload thrust load is applied to the tool holding cylinder 20. part 33a, and a second detection display part 3 that faces the central protrusion 35 of the reference detector 34 when the tool holding cylinder 20 retreats in the axial direction due to an overload thrust load.
3b. The second detection display section 33b protrudes from the first detection display section 33a on the opposite side in the rotational direction by twice the play in the circumferential direction between the reference detector 34 and the displacement detector 31 (a in FIG. 4). Therefore, when it moves rearward in the axial direction due to an overload thrust load, a thrust detection area 38a is formed between it and the reference detector 34 as shown in FIG. 4(b).

Three reference detectors 34 are provided in the holder main body 2 so as to protrude from the holding part 3 toward the inside of the three recesses 30, and each reference detector 34 and the displacement detector 31 face each other in between. There is. As shown in FIG. 4, each reference detector 34 has a stepped shape with a protruding center, and one side surface 40a of the low step portion 40 and the detection display portion 32 come into contact with each other due to the torsional force of the torsion coil spring 25. 4, there is a slight play in the circumferential direction between the other side surface 40b of the low step part 40 and the opposing detection display part 33a (a in FIG. 4, the pulse count value corresponding to the absolute value 2a is set as described later). t). Both edges in the rotation direction of the central protrusion 35 form a pair of detection display parts 36 and 37 that indicate the start or end of detection by a proximity switch 45, which will be described later. A pair of rotational deviation detection areas 38 and 39 are formed between the detection display parts 32 and 37 and the corresponding pair of detection display parts 32 and 33a.
．． 39 is three pairs of membranes between the circumferential direction and the circumference. When no overload torque is applied, the pair of detection areas 38, 39
The circumferential length of the central protrusion 35 and the circumferential length of the detection display parts 32 and 338 of the displacement detector 31 are all set to be the same length (30 degrees).

A proximity switch 45 is disposed at a position to detect the front part of the detection area 38, 39 in the axial direction via a bracket 16 fixed to the front surface of the spindle head 15, facing the rotation locus of the detection area 38.39. . This proximity switch 45 also detects the thrust detection area 38a when an excessive thrust load occurs.

The proximity switch 45 is designed to output an OFF signal when each detection area 38° 38a, 39 is detected. The signal from the proximity switch 45 is sent to overload torque (or thrust load) determining means 50 shown in FIG.

In the determining means 50, 51 is a frequency-voltage converter 52
The signal pulses from the proximity switch 45 are averaged by the voltage-frequency converter 53 and multiplied by a predetermined multiple.
7, a spindle angle pulse generator that generates a predetermined number of reference pulses in one rotation; 54, a proximity switch 45;
The gate circuit 55 rises when the signal falls and falls when the signal rises (opens while the proximity switch 45 is FF), and the gate circuit 55 adds or subtracts the spindle angle pulse Ps that is input while the gate circuit 54 is open. A counter 56 is an addition/subtraction switching circuit that switches addition or subtraction commands to the counter 55 in one period of the ON/OFF signal of the proximity switch 45, and outputs a judgment command signal to a comparator circuit 57 at the rising edge. Counter 5 when there was
A comparison circuit 59 determines whether the count value in 5 exceeds a set value t preset by a setting circuit 58;
7 is a reset circuit that resets the counter 55 after the determination, and 60 is an output circuit that outputs an overload torque (or thrust) detection signal as an output signal C when the comparison result of the comparison circuit 57 exceeds a set value t. be. The set value t is set to be the difference between the pulse count values of the counter 55 when the proximity switch 45 detects the pair of detection areas 38 and 39 during no-load before cutting, plus a tolerance value.

Assuming that there are no manufacturing errors, the difference in pulse count values in the pair of detection areas 38 and 39 will be zero in this embodiment. Incidentally, the encoder output of the drive motor for the spindle 17 may also be used as the spindle angle pulse Ps. In addition, instead of the spindle angle pulse PS, a time pulse is output at a constant frequency, and this is counted by a counter. The output signal may be output.

In this case, since the set value depends on the rotational speed of the spindle 17, correction for the rotational speed is required.

Now, according to the above configuration, during normal cutting, the rotation of the holder shaft 1 is caused by the rotation of the tool holding cylinder 2 via the torsion coil spring 25.
0 and processing is performed.

The proximity switch 45 repeatedly outputs ON and OFF signals. It is turned OFF in the detection area 38, and during this time the gate circuit 54 opens and the spindle angle pulse Ps is added in the counter 55 under the addition command from the addition/subtraction switching circuit 56.The proximity switch 45 detects the central protrusion 35. When it turns ON, the gate circuit 54 closes and switches 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 earlier in the counter 55, and when the proximity switch 45 detects the displacement detector 31 and turns ON, the judgment is made. 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, the detection display parts 32 of the displacement detector 31 and reference detector 34 are in contact with one side 40a of the low step part 40 due to the torsion coil spring 25, so the lengths of the detection areas 38 and 39 are the same. Therefore, the count value in the counter 55 becomes zero, and the overload torque output signal is not affected.

When the cutting edge of the tool 13 becomes dull or the torque exceeds the transmission torque set by the torsion coil spring 25 due to cutting chips clogging, etc., the displacement detector 31 causes a rotation delay with respect to the reference detector 34, and the relative 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. Due to this relative rotation, the length of the detection area 38 in the circumferential direction becomes L-a, and the length of the detection area 39 in the circumferential direction becomes L+a. Therefore, it is added in the detection area 38,
The result of subtraction in the detection area 39 is -28, and its absolute value is greater than the set value t, so the output circuit 60 outputs the overload torque output signal C.

This overload torque output signal C can be used to output a stop command to the spindle drive motor or to command a step-back operation. Furthermore, a lifespan counter is provided to count the output signal, and the lifespan counter is When the count value exceeds a predetermined number of times, the tool is replaced with a new tool that is the same as the previous tool even during machining. Proximity switch 45
Depending on the detection timing, addition may be performed in detection area 39 and subtraction may be performed in detection area 38. Even in this case, the comparison result (
Since the absolute value of the difference) is 2a, overload torque is detected by comparing it with the set value t. Incidentally, the above-described determination means 50 may be processed by software using a computer.

2, in determining overload torque, the displacement detector 3
Since a value twice the relative rotation amount (play) between 1 and the reference detector 34 is output as a comparison result, overload torque will be detected even if the value of the relative rotation amount is extremely small. . Therefore, even if the transmission torque slightly exceeds the transmission torque set by the torsion coil spring 25, this can be detected instantaneously and subsequent corresponding actions can be taken.

Next, due to tool wear, only the overload thrust load is applied to the tool 1.
The case where 3 occurs will be explained based on FIG. 4(b).

The spring 5 does not bend backward until an overload thrust load exceeding the thrust load set by the spring 5 is generated on the tool 13, and the displacement detector 31 and the reference detector 34 are in the relationship shown in FIG. 4(a). . When an overload thrust load is applied to the tool 13, the support shaft 4 and the tool holding cylinder 20 move backward relative to the main body 2. As a result, the second detection display section 33b of the displacement detector 31 faces the detection display section 36 of the reference detection 34 in the circumferential direction, and a thrust detection region 38a is formed between the two.
Its rotation locus faces the proximity switch 45. Since the length in the circumferential direction of this thrust detection area 38a is L-2a, if the spindle angle pulse PS is added in this thrust detection area 38a and subtracted in the detection area 39 (or vice versa), the absolute value of the difference is becomes 2a, and overload thrust is detected by comparing it with the set value t.

Effects of the Invention As described above, according to the tool holder of the present invention, the circumferential length of the rotational deviation detection area formed by the reference detector and the displacement detector changes due to overload torque applied to the tool. By detecting this, it is possible to detect the occurrence of overload torque.

In addition, the detection display section for thrust detection provided on the displacement detector due to overload thrust is arranged to face the reference detector in the circumferential direction to form a thrust detection area. If installed, this detector will be able to detect the rotational speed detection range except when thrust is occurring. Therefore, one detector can detect both overload torque and overload thrust load, and the structure can be simplified and tool breakage can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a tool holder used in the device of this invention, Fig. 2 is a sectional view taken along ■-■ in Fig. 1, and Fig. 3 is a sectional view taken along
A cross-sectional view, FIG. 4 is a developed view of the entire circumferential direction of the reference detector and the displacement detector, and an action diagram, 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, 32.3
3, 36, 37...Detection display section. 34...Reference detector, 38.39...Detection area, 38
a... Thrust detection area, 45... Proximity switch. 50...Discrimination means

Claims (1)

[Claims] 1. A tool holding cylinder with a collet chuck at the tip is connected to a holder body with a tapered shank through an elastic member for transmitting torque so as to allow a predetermined play in the circumferential direction. In a tool holder that causes rotational misalignment between the main body and the tool holding cylinder, the tool holding cylinder is supported by the holder body so as to be slidable in the axial direction, a thrust load setting spring is interposed between the tool holding cylinder and the holder main body, and the holder is A plurality of reference detectors provided on the outer periphery of the main body at predetermined intervals in the circumferential direction and a displacement detector provided on the tool holding cylinder are faced between each other to form the rotational deviation detection area between them,
Furthermore, the displacement detector is provided with a detection display section for detecting thrust that faces the reference detector in the circumferential direction when the tool holding cylinder moves in the axial direction when overload thrust occurs. , tool holder for thrust detection.