JPH0741521B2 - Tool overload torque detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload torque detecting device for detecting tool overload torque generated during cutting and predicting tool breakage.

Conventional technology A reference gear integrated with a tool holder and displacement gears connected to this reference gear via elastic displacement parts that generate torsion in proportion to the cutting torque are separated by phase detectors such as proximity switches. One that detects and estimates the cutting torque from the phase difference of both gears in the signal processing unit and compares it with the case of a normal tool (Japanese Patent Laid-Open No. 59-142049), chuck attachment to the rotating member integrally mounted on the spindle When the screw rod of the member is screwed so as to be rotatable relative to each other and the set transmission torque of the torsion coil spring between the rotating member and the chuck mounting member is exceeded, the phase of the rotating member and the chuck mounting member deviates, which causes the screw rod to There is one that displaces in the axial direction by the action to extract the overload torque (No. 54-10060).

Problems to be Solved by the Invention According to the above, since there are two phase detectors, for example, malfunction due to adhesion of cutting chips to the phase detector is likely to occur. Also, according to this, in order to take this out as an axial displacement of the screw rod when an overload torque is generated, the phases of the rotating member and the chuck mounting member are considerably deviated, so that the torsional strength of the torsion coil spring is resisted. The overload torque cannot be detected unless the set transmission torque of the torsion coil spring is greatly exceeded. Further, since it takes time for the phase of the rotating member and the chuck mounting member to largely shift, there is also a problem that a stop command is not instantaneously output to the spindle.

Means for Solving the Problems In order to solve the above problems, the present invention detects an overload torque of a tool as a rotational deviation between detectors provided on a holder shaft and a tool holding cylinder, respectively. While meshing with each other to allow a certain amount of play in the circumferential direction, both the detectors are brought into contact with each other in the circumferential direction by the torsion coil spring, and the opposite contact side edges of both detectors in the contact state are detected and displayed. As a part, a rotation deviation detection area between these detection display portions is provided, and a proximity switch that outputs an ON signal when the detection area is detected is provided in proximity to the passage surface of this detection area when the tool holter is rotated, The play is set to such an amount that the proximity switch is not turned off even if a gap is created between the two detectors, and the proximity switch is connected to the discriminating means, which discriminates a predetermined number of times per spindle rotation. Standard power The spindle rotation angle pulse generator that generates the pulse, the counter that counts this reference pulse while the proximity switch is detecting the detection range, the comparison circuit that compares the counter count value with the preset value, and the comparison result. And an output circuit for outputting an overload torque detection signal based on the above.

When the overload torque is generated, the detector of the tool holding cylinder causes a rotation delay with respect to the detector of the holder shaft, and rotates in the circumferential direction by a predetermined play. As a result, the length of the detection area formed between the detectors becomes longer than in the normal state, so the proximity switch detects this increased detection area and turns it on.
While outputting the signal, the counter counts the reference pulse generated by the spindle rotation angle pulse generator, and the comparison circuit compares the count value in this counter with the preset value, When the set value is exceeded, the output circuit outputs the overload torque detection signal.

Embodiment As shown in FIG. 1, a holder shaft 1 has a taper shank 2 fitted in a main shaft taper hole 12, a gripping part 3 for a tool exchanging arm in front of it, and a center of the gripping part 3 protruding forward. The support shaft 4 is provided. From the outer circumference of the grip 3 to the front,
Reference detectors 5 are provided so as to project at positions that divide the entire circumference into four equal parts. As shown in FIG. 4, the reference detector 5 includes a protrusion 5a and a step 5b, and a side edge of the protrusion 5a in the rotational direction indicated by an arrow R (a side opposite to the displacement detector 31 which will be described later). The edge is a detection display section 5c that indicates the start of detection of a proximity switch described later.

The conical surface 7 at the rear end of the sleeve 6 which is slidable in the axial direction on the support shaft 4 and the conical surface 8 at the front end of the support shaft 4 shown in FIG. It is supported by pivot ball bearings 9 and 10. These pivot ball bearings 9,
A spring 11 interposed between the support shaft 4 and the sleeve 6 of 10 applies pressure to the conical surfaces 7 and 8. A collet chuck 23 for holding a tool 13 such as a drill is attached to the front end of the support cylinder 21.

A connecting cylinder 24 is integrally screwed on the outer circumference of the support cylinder 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 grip 3. As shown in FIG. 2, two upper and lower positioning pins 26 are planted in the connecting cylinder 24, and a detection ring 28 having a large number of locking holes 27 that engages and disengages with the positioning pins 26 is provided on the grip portion 3. It is urged forward by a spring 29 interposed between and. Therefore, the torsional strength (transmission torque) of the torsion coil spring 25 moves the detection ring 28 backward (rightward in FIG. 1) against the spring force to disengage the engagement hole 27 and the positioning pin 26, In that state, after rotating the support cylinder 21 and the connection cylinder 24 in the circumferential direction, the detection ring
By engaging the locking hole 27 of 28 and the positioning pin 26, adjustment is made so that the allowable transmission torque according to the diameter of the tool 13 does not break the tool 13.

As shown in FIG. 4, the detection ring 28 is provided with displacement detectors 31 projecting rearward at positions corresponding to the reference detector 5 and dividing the circumferential direction into four equal parts. An edge on the opposite side of the displacement detector 31 in the rotation direction (an edge on the side opposite to the protruding portion 5a) serves as a detection display portion 31c indicating the end of detection of the proximity switch 45. Displacement detector 3
1 and the reference detector 5 are engaged with each other with a play (FIG. 4a) in the circumferential direction between the detection display portion 31c and the step portion 5b. The torsional force of the torsion coil spring 25 causes the protruding portion 5a of the reference detector 5 and the displacement detector 31 on the opposite side in the rotational direction to come into contact with each other, and the respective detection display portions
Between 5c and 31c, one or more (four in this embodiment) detection zones 32 for the rotation deviation of the circumferential length L, which the proximity switch 45 detects and outputs an ON signal, are formed. It

As shown in FIG. 1, one proximity switch 45 for detecting the detection area 32 is arranged close to the passage surface of the detection area 32 via a bracket 15 fixed to the spindle head 14. As shown in FIG. 5, the proximity switch 45 detects a detection object (in this case, the reference detector 5 and the displacement detector 31 forming the detection area 32) by the distance from the detection surface 45a and outputs an ON signal. The operation area A is determined. The play a is set to be equal to or less than the range of the operation area A. Therefore, when the displacement detector 31 lags the reference detector 5 by the play a due to the overload torque, a gap is generated between the displacement detector 31 and the reference detector 5 which are in contact with each other. Due to the gap, the proximity switch 45 does not turn off.

Next, the overload torque determination means 50 that processes the detection signal from the proximity switch 45 will be described. In FIG.
Reference numeral 51 denotes a spindle rotation angle pulse generator that generates a predetermined number of reference pulses per revolution of the main shaft 16, and is, for example, a rotary encoder connected to the main shaft 16. 52 has a proximity switch 45
A gate circuit that opens only during ON and sends the reference pulse to the counter 53, 53 is a counter that counts the reference pulse, and 54 is a comparison circuit that compares the count value in the counter 53 and the preset value set in the setting circuit 55. , This set value is a value obtained by adding a certain allowable value to the count value of the reference pulse in the counter 53 counted while the proximity switch 45 detects the detection area 32 and outputs the ON signal at no load torque. The counter value in the counter 53 when the displacement detector 31 is rotated by the play a is larger than the set value. Further, this set value corresponds to an angle obtained by calculating the angle of the section in which the proximity switch 45 is turned on by design and adding the manufacturing error and the allowable value of the circumferential lengths of the detectors 5 and 31 to this. The reference pulse number may be used. Further, in order to detect a precise rotation deviation that may be affected by manufacturing error, the reference pulse number detected during no-load torque corresponding to each detection region 32 is stored separately as a determination value in advance, On the other hand, during cutting, it is preferable to provide a counter for the detection area 32 that specifies each detection area 32, specify the detection area 32, and compare the corresponding set value with the count value in the counter 53. Is. Also, 56
Is a reset circuit that resets the counter 53 when the proximity switch 45 is turned off, and 57 outputs an overload torque detection signal when the count value in the counter 53 exceeds the set value according to the comparison result of the comparison circuit 54. Output circuit.

According to such a configuration, when the load torque generated in the tool 13 is in a range that does not break the tool 13, the torsion force of the torsion coil spring 25 causes the protrusion 5a of the reference detector 5 and the displacement detector.
Since 31 is in contact with each other, the circumferential lengths of the four detection areas 32 are the same as the length L when there is no load. Therefore, the gate circuit 52 is opened while the proximity switch 45 is detecting one detection area 32, and the number of reference pulses counted in the counter 53 only during that time is the same as that in the no-load state, so that the setting circuit 55 is set. It is smaller than the set value inside, and the overload torque detection signal is not output.

When an overload torque exceeding the allowable transmission torque set by the torsion coil spring 25 is generated in the tool 13 due to defective chip discharge during cutting, the tool holding cylinder 20 causes the torsion force of the torsion coil spring 25 with respect to the holder shaft 1. Against this, a rotation delay is sent by play a. As a result, the protruding portion of the reference detector 5 that is in contact with
A gap of play a is generated between 5a and the displacement detector 31, but since the play a is set within the operation area of the proximity switch 45, the protruding portion 5a is out of the operation area A as shown in FIG. Since the displacement detector 31 comes into the operation area A before, the proximity switch 45 cannot detect this gap and, as a result, the detection area 32.
Becomes L + a. Therefore, the count value counted by the counter 53 while the proximity switch 45 detects the lengthened detection area 32 and outputs the ON signal exceeds the set value, and the output circuit 57 outputs the overload torque. The detection signal of is output. With this detection signal, the spindle head 14 steps back to prevent tool breakage, or the number of times this detection signal is generated is counted, and when the set value is reached, it is judged that the tool has reached the end of its service life and a new tool is replaced. .

As described above, according to the device of the present invention, the detector provided on each of the holder shaft and the tool holding cylinder connected to the holder shaft through the torsion coil spring for torque transmission is contacted by the torsion coil spring. Mesh with a certain play in the opposite direction,
A detection area that becomes longer due to overload torque is provided by both detectors,
Since the extension of the detection area is detected by the proximity switch, the rotation deviation between the detectors can be detected by one proximity switch, and compared with the conventional technique having two detection switches, It is possible to reduce error motion due to adhesion of cutting chips. Moreover, the play is set to an amount that does not turn off the proximity switch even if there is a gap due to the play between the two rotary jaws when there is a rotation deviation, so the amount is small and therefore set by the torsion coil spring. Even when the allowable transmission torque is slightly exceeded, the overload torque can be detected, the overload torque detection signal can be output promptly when the overload torque occurs, and tool breakage can be prevented.

[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 developed view showing the relationship between the reference detector and the displacement detector, and FIG. 5 is an explanatory view of the operation area of the proximity switch,
FIG. 6 shows the discrimination means. 1 ... Holder axis, 5 ... Reference detector, 5c, 31c ... Detection display section, 13 ... Tool, 20 ... Tool holding section, 25 ... Torsion coil spring, 31 ... Displacement detector, 32 ... … Detection area, 45 ……
Proximity switch (detection switch), 50 ... Distinguishing means, a ...
… Playing, A… Operating area

Claims (1)

[Claims] 1. A holder shaft is rotatably supported by a holder shaft, and both members are connected by a torsion coil spring for torque transmission. The holder shaft and the tool holder cylinder are connected to a detector provided on one side of the holder shaft. In a tool holder configured to detect an overload torque from a rotational deviation of a provided detector, the detectors are meshed with each other in a circumferential direction to allow a predetermined play, and both detectors are connected by the torsion coil spring. Abutting from the circumferential direction, the opposite contact side edges of both detectors in the contact state are used as the detection display portions, and the detection gap between these detection display portions is the detection area of the rotation deviation. A proximity switch that outputs an ON signal when the detection area is detected is provided in the vicinity of the passage surface, and the play is set to an amount that does not turn off even if a gap is created between the two detectors due to the play. Set and this proximity The switch is connected to a discriminating means, and the discriminating means is a spindle rotation angle pulse generator for generating a predetermined number of reference pulses in one rotation of the spindle, and a counter for counting the reference pulses while the proximity switch is detecting the detection area. An overload torque detection device for a tool, comprising: a comparison circuit that compares the counter count value with a preset value; and an output circuit that outputs an overload torque detection signal based on the comparison result. .