JPS60150946A - Breakage preventing device of rotating tool - Google Patents

Abstract

PURPOSE:To realize the use of the breakage preventing device even during automatic operation of a tool with a small diameter, by exerting pressure of the piezoelectric body by the relative motion generated between the tool holder and power transmission member when the torque limitter is in action, and further by detecting the electromagnetic wave which is generated as a result of discharge of the high voltage from the piezoelectric body. CONSTITUTION:If the machining torque is increased during machining due to wear of the blade tip of blocking caused by the machined chips and there is a danger of damage or breakage or the tool, torque limitter 30 is actuated to generate a slippage between a power transmission member 20 and transmission cylindrical shaft 10, and the part between a rotating tool 15 and a cam projection 44 is stopped. However, as a tool holder main body 1 continues to rotate, a leaf spring 42 rotates around the cam projection 44 which is at rest. Due to this relative motion, the leaf spring 42 intermittently comes in contact with the cam projection 44 and snapped, and hammer 41 exerts a pressure on a piezoelectric body 40. A high voltage is generated intermittently, and it, in turn, generates an electromagnetic wave as a result of spark or corona discharge between discharge terminals 45, 46. When the voltage exceeding the specified value is detected, it is output to the pulse generator.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects abnormal conditions such as the risk of tool damage and breakage during cutting using rotating tools such as drills and taps, and reduces tool life. The present invention relates to a breakage prevention device for a rotary tool that can be used for determining, replacing a tool, or performing an appropriate tool protection operation to prevent tool breakage.

It is well known that a torque limiter is used as a breakage prevention device for rotating tools to prevent breakage, but simply using a torque limiter is not enough to perform durability tests on torque limiters when one worker is not present. This leads to the same situation as above, which leads to the destruction of the torque limiter, and there is a problem that it cannot be applied to automatic machining.

As a breakage prevention device for rotating tools that can be applied to automatic processing,
A method of predicting tool breakage using changes in the load current of the electric motor that rotates the tool, and a method of detecting cutting resistance or its common ratio using a strain gauge attached to the tool holder or machine spindle, and detecting tool breakage based on these changes. How to predict, and how to predict the occurrence of acoustic damage that naturally occurs when a tool is damaged or broken? y (Acous
There is a method of predicting tool damage or breakage by externally detecting elastic vibrations generated during the operation of a torque limiter or a torque limiter. However, in all of these methods that do not use a torque limiter, the detection signal is related to the magnitude of the cutting torque applied to the tool.
Small diameter tools (49mm or less) that require special prevention of breakage
In this case, since the cutting torque is small, the detection signal is also small, resulting in lower reliability and difficulty in applying it to automatic driving.

In addition, there are two types of methods using torque limiters: a contact method that detects the elastic vibrations generated when the torque limiter operates directly from the tool holder, and a non-contact method that detects the elastic vibrations that occur when the torque limiter operates by installing a detector at a location away from the tool holder. There is. But in the former,
There are difficulties in transmitting elastic vibrations between the rotating and non-rotating parts of the tool holder, requiring special measures for signal transmission means, and in the latter case, the 9N ratio of the signal is poor, making it difficult to ensure reliability. There were problems such as inferiority.

The present invention has been made in view of the current situation.
When the torque limiter attached to the tool holder operates,
An object of the present invention is to provide a breakage prevention device for a rotary tool that stably generates a large-level detection signal regardless of the magnitude of the cutting torque applied to the tool and can be applied to automatic operation of small-diameter tools.

Specifically, the breakage prevention device of the present invention includes a tool holder main body that is attached to a machine main shaft and rotated, a tool gripping shaft that is rotatably fitted in the tool holder main body, and a tool holder main body that is attached to the tool gripping shaft. a transmission member that transmits the rotational force of the
a torque limiter assembled to the transmission member; a piezoelectric body attached to the tool holder body; A pressurizing means that pressurizes and generates a high voltage, a discharge terminal that guides the high voltage of the piezoelectric body and generates an electromagnetic wave, and an antenna receives the electromagnetic wave from the discharge terminal as a detection signal, amplifies it, detects it, and generates a pulse. The present invention is characterized in that it includes a detection section that converts the pulse signal into a signal and confirms that the pulse signal is generated during operation of the torque limiter.

According to the present invention, the piezoelectric body is pressurized in conjunction with the relative movement between the tool holder body and the transmission member that occurs when the torque limiter operates, and the high voltage generated in the machined piezoelectric body is discharged. Since electromagnetic waves are generated and the electromagnetic waves are used as detection signals, a constant signal can be obtained regardless of the magnitude of the cutting torque applied to the tool. Therefore, it can also be applied to prevent damage and breakage of small diameter tools. In particular, the detection unit converts the electromagnetic wave into a pulse signal and determines whether the number of occurrences of the pulse signal within a certain period of time matches the number of occurrences of the pulse signal determined from the spindle rotation speed and the structure of the torque limiter. , electric motors and electromagnetic switches inside factories,
Reliability will be extremely high if the detection signal is reliably distinguished from noise from high-frequency generators, welders, and other equipment.

In addition, since the electromagnetic wave that is the detection signal can be detected outside the tool holder in a non-contact state, it is only necessary to assemble the piezoelectric body, the pressure means for the piezoelectric body, and the discharge terminal into the tool holder body. The device is simple, lightweight, and easy to handle.

Embodiments of the present invention will be described below based on the drawings. 1
1 is a tool holder main body, which has a cylindrical part 2 for holding rotary tools such as drills and taps, and a taber shank part 3 and a collar part 4 that are integrally connected to the rear end. It is installed by fitting into the tapered hole 7 of the main shaft 6 of the machine.

A drive key 8 protruding from the main shaft 6 is engaged with a keyway 5 provided in the collar 4 and rotates together with the main shaft 6.

9 indicates a mechanical fixing part.

10 is a transmission cylinder shaft, which is connected to the tool holder main body 1 via a key 11.
The adjustment nut 13 is screwed into the threaded part 12 carved on the outer periphery of the front part of the cylindrical part 2.

It has a structure in which the length of protrusion from the cylindrical portion 2 can be adjusted.

Reference numeral 14 denotes a tool gripping shaft, which is rotatably fitted to the transmission cylinder shaft 10. In the illustrated embodiment, a tag 15 is used as the rotary tool, and its floating mechanism 16 is incorporated, so that it can be rotated in the axial direction within a certain range. It is also possible to slide into the

A rotary tool (tap) 15 is fitted onto and held at the tip of the tool grip shaft 14 . Further, the latter half of the tool gripping shaft 14 is formed into a hollow shaft, and a square hole 18 is provided in the rear wall portion 17 in order to engage a transmission member to be described later.

Reference numeral 20 denotes a transmission member, which includes a main body of a disk 21, a square shaft 22 protruding from one side thereof, and a screw shaft 23 protruding from the opposite side.
The square shaft 22 is slidably engaged with the square hole 18, and the screw shaft 23 is assembled with a torque limiter to be described later. Further, clutch grooves 24 of the torque limiter are provided at eight locations on the surface on the side of the first disc 23, and an annular mounting groove 26 is formed on the outer circumference (see FIG. 3). Above transmission part 2
0 is rotatably fitted to the transmission cylinder shaft 10 by fitting the first disc 21 to the rear end of the transmission cylinder shaft 10 via a steel ball 26 that engages with the annular groove 26.

The torque limiter 30 includes a steel ball 31 that engages with each clutch groove 24, a retainer 32 that is rotatably fitted onto the screw shaft 23 and holds the copper balls 31, and a retainer 32 that is fitted into the retainer 32 and holds the copper balls 31. A buck ring 33 that presses against the screw shaft 23, a disc spring 34 that is fitted onto the screw shaft 23 and presses the steel ball 31 into the clutch groove 24 via the buck ring 33, and a disc spring 34 that is screwed onto the screw shaft 23 and adjusts the spring pressure of the disc spring 34. The torque setting nut 35 is comprised of a torque setting nut 35. As clearly shown in FIG. 4, a pair of protrusions 36, 36 provided diametrically opposite each other on the front end surface of the retainer 32 form a notch 37 at the rear end of the transmission cylinder shaft 10. 37, rotational force is transmitted from the transmission cylinder shaft 10 to the retainer 32, and further transmitted from the retainer 32 to the tool gripping shaft 14 via the steel balls 31, the disc 21, and the square shaft 22.

A piezoelectric body 40 is attached to the rear end of the cylindrical portion 2 of the tool holder main body 1 by being fitted from the side thereof, as shown in FIGS. 1 and 2. A hammer 41 applies pressure to the piezoelectric body 4°, and is attached to the tip of a leaf spring 42 which is attached in a cantilevered manner to the inner side of the cylindrical portion 2 via a mounting piece 43. 44 is a cam protrusion that engages with the leaf spring 42, and is set at equal intervals on the outer circumference of the rear end of the torque setting nut 36, and is engaged with the leaf spring 42 at regular intervals when the torque limiter 30 is operated. The plate spring 42 is engaged and acts to flip the leaf spring 42.

45 and 46 are discharge terminals, and one discharge terminal 46 is connected to the planu side of the piezoelectric body 4o.

The other discharge terminal 46 is connected to the main side of the piezoelectric body 40 via the tool holder body 1 and is disposed inside the cylindrical portion 2 so as to face each other. 47 is both discharge terminal 45.4
This is a through hole for emitting electromagnetic waves as a detection signal generated between the holes 6 and 6 to the outside, and an insulating nulligue 48 is fitted therein.

An antenna 49 receives electromagnetic waves emitted through the through hole 47, and is installed on a mounting base 9' attached to the machine fixing part 9.

Next, the operation of the above device will be explained. First, the torque setting nut 36 is adjusted so that the torque limiter 3o is activated when the torque applied to the rotary tool 15 during cutting exceeds a certain threshold (life torque).

Therefore, when the cutting edge of the rotary tool 15 wears out during the cutting process and approaches the end of its life, the cutting torque increases significantly due to the accumulation of chips, and there is a risk that the tool 15 may be damaged or broken. The torque limiter 30 is activated, and a null is generated between the transmission member 20 and the retainer 32 and therefore the transmission cylinder shaft 10, causing the rotation of the tool 15, the tool gripping shaft 14. The transmission member 20 and the torque setting nut 35L, therefore, the cam protrusion 44 stops. On the other hand, since the tool holder main body 1 continues to rotate, the leaf spring 42 rotates around the cam projection 44 which is in a stopped state, and this relative movement causes the leaf spring 42 to intermittently engage with the cam projection 44. It was bounced.

Due to the elastic force, the hammer 41 attached to the leaf spring 42 applies pressure to the piezoelectric body 40, and a high voltage is intermittently generated. The high voltage thus generated in the piezoelectric body 40 generates a spark discharge or a corona discharge between the discharge terminals 45 and 46 to generate electromagnetic waves. The electromagnetic wave is received by the antenna 49 through the through hole 47 as a detection signal.

The electromagnetic waves received by the antenna 49 are sent to the detection section 100 shown in FIG. Next, when a voltage larger than a preset threshold is detected in the amplitude discriminator 63, an oscillation command is given to the pulse oscillator 54. Note that if the voltage is smaller than the threshold value, it is determined that the torque limiter 30 is not operating and that the tool 15 is performing normal cutting.

However, as mentioned above, since electromagnetic waves are used to transmit signals from the discharge terminals 45, 46 to the antenna 49 without contact, a lot of noise is mixed into the factory during the above transmission process. This may become an obstacle to reliably detecting only the signal when the torque limiter 30 is activated. Therefore, an angle detector 101 is provided which outputs a signal when the main shaft 6 reaches a certain angular position.
A counter 102 counts the number of pulses sent from the pulse transmitter 64 between two signals sent from the main shaft 6, that is, during one rotation of the main shaft 6. This count number is input to the comparator 103, and it is compared whether this count number matches the number of times the hammer 41 hits the piezoelectric body 40 (the number of hits) during one rotation of the main shaft 6. The number of strikes is preset by the structure of the torque limiter 30.

If the count number and the number of strikes match, it is determined that the torque limiter 30 has been activated, and the alarm signal generator 104 issues an abnormality alarm and sends it to the controller, and the tool 16 is activated. A protective operation to prevent breakage is performed according to a preset command procedure. If the two do not match, it is determined that the torque limiter 30 is not operating, and processing and monitoring continue.

When the above-mentioned sleep operation is repeated many times and exceeds a predetermined criterion, the tool 15 has reached the end of its life due to wear, etc., or the cutting conditions are inappropriate (for example, due to the hardness of the workpiece). If the tool is judged to be too large or the feed is excessive, etc., appropriate measures are taken, such as issuing a U alarm and stopping the machine to replace the tool.

The detection section shown in FIG. 5 uses an angle detector 101, but instead of the angle detector, the controller of the NC machine tool outputs the spindle rotation speed, and from this output the main
l]1II6 may be calculated, a signal may be generated at this time interval, and the counter 102 may count the number of pulses sent from the pulse oscillator 54 within this time interval.

If the noise is still not too bad, the torque limiter 3
It is also possible to determine whether or not 0 is operating. That is, the generation times ti, ti-, t, of each pulse signal
I-, . . . are measured, and the time interval Δt i =t i -t i-1 between each pulse signal is calculated.

Furthermore, the difference in one hour interval (△ti), that is, △ti~△
Calculate ti-. This is how I met △ti〜△t
Since i-, is a substantially constant value regardless of the magnitude of the set torque at which the torque limiter 30 operates, this value is used as a reference for comparison with noise. For example, △ti~△ti-, ≦0.
1△ti-.

If the following conditions are satisfied, it can be considered that the pulse signal is generated regularly, and therefore, it is determined that the torque limiter 30 is operating. On the other hand, △ti〜△ti−
, >0,1Δti-t, the pulse signal is irregular, and it is determined that this is not the torque limiter 30 activated, but a pass/I/pass signal due to noise.

As described above, according to the device of the present invention, when an overload is applied to a rotary tool during machining work and there is a risk that the tool will break, or when the tool life is nearing due to wear of the cutting edge, these accumulated Since the calculated state can be reliably detected regardless of the magnitude of the set torque value of the torque limiter, this method is particularly effective for improvising abnormal states of small-diameter tools with low cutting torque.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional front view showing an example of the breakage prevention device for a rotary tool according to the present invention, Fig. 2 is a sectional view taken along line 2-2' in Fig. 1, and Fig. 8 is a transmission member. FIG. 4 is a perspective view of the retainer and the rear end portion of the transmission cylinder shaft, and FIG. 5 is a system diagram of the detection section. 1...Ocharuda main body 2...Cylinder
Part 10... Transmission cylinder shaft 14... Tool gripping shaft 20
... Transmission mm material 30 ... Torque limiter 40 ... Piezoelectric body 41 ... Hammer 42 ...
Leaf spring 44...Cam projections 45, 46...Discharge terminal 47...Through hole 49...Antenna patent applicant Wasayaki Co., Ltd.

Claims (1)

[Scope of Claims] 1. A tool holder body that is mounted on a machine main shaft and rotated, a tool gripping shaft that is rotatably fitted to the tool holder body, and a tool gripping shaft that rotates the tool holder body. A transmission member that transmits force, a torque limiter attached to the transmission member, a piezoelectric body attached to the tool holder body, and a relationship between the tool holder body and the transmission member that occurs when the torque limiter operates. a pressurizing means that pressurizes the piezoelectric body to generate a high voltage in conjunction with the relative movement of the piezoelectric body, a discharge terminal that guides the high voltage of the piezoelectric body and generates an electromagnetic wave, and uses the electromagnetic wave from the discharge terminal as a detection signal. A rotary tool that receives the pulse signal with an antenna, amplifies it, detects it, and converts it into a P/L'nu signal, and a detection section that confirms that the pulse signal is generated during the operation of the torque limiter. breakage prevention device. 2. The pressurizing means is attached to a leaf spring attached to the tool holder main body in a cantilevered structure, a hammer attached to the leaf spring, and the transmission member, and the pressure generated when the torque limiter is operated a cam that intermittently engages with the leaf spring in conjunction with the relative movement of the tool holder body and the transmission member to act to flip the leaf spring, and The breakage prevention device for a rotary tool according to claim 1, wherein the device is configured to pressurize the piezoelectric body.