JPS63245304A - Precognition device for abnormality of tool - Google Patents

Abstract

PURPOSE:To prevent the apprehension of drill breakage even during slight feed of a main spindle due to inertia by providing a coupling means to make a tool fitting shaft free from a sleeve body in both axial and rotational directions when resistance acting on the tool fitting shaft exceeds its set value. CONSTITUTION:When a damaged or wrongly selected drill and clogging chips increase resistance acting on a tool fitting shaft 8 above its fixed value during machining process, a ball 12 leaves a recess 14 formed on the protruding part 13 of the shaft 8, which can not follow the rotation of a member 4 to cause an exhaust hole 25 to get out of the position of a communicating hole 27 for shutting off the exhaust hole 25. The above-mentioned shutting off causes pneumatic pressure in an air feed passage to rise rapidly, and a pressure sensor detects the above-mentioned rapid pressure rise to input the signal of the pressure rise into a control amplifier and then into the control part of a machining center for stopping a main spindle 2 and simultaneously giving the alarm of an abnormal state. In addition to that, the shaft 8 is made free from the rotary member 4 in both axial and rotational directions simultaneously with the occurrence of the abnormal state, and therefore moves back to check the action of torque or thrust load on itself even during the continuous rotation or feed of the main spindle 2. Thus the breakage of a drill can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a tool holder attached to a numerically controlled machine tool equipped with an automatic tool changer (ATC), a so-called machining center, a turning center, and other machine tools. This invention relates to a device for predicting a tool abnormality, and in particular, is designed to allow the tool mounting shaft to escape both in the rotational direction and the axial direction with respect to the main shaft when a tool abnormality is predicted.

[Conventional technology]

As a conventional technique, a plunger pressed by a spring is placed between the spindle of a machine tool and a drill chuck, and an engagement recess into which the tip of the plunger engages, as described in Japanese Utility Model Application Publication No. 59-132710. When the resistance applied to the drill fixed to the drill chuck reaches a certain value, the plunger disengages from the engagement recess and separates the spindle and drill chuck, allowing the drill chuck to rotate freely relative to the spindle and increasing the torque. There is one in which a switch is activated to bring the spindle to an emergency stop.

[Problem that the invention seeks to solve]

In the case of the above conventional technology, in order to separate the spindle and drill chuck when a tool abnormality occurs, the drill does not turn even if the spindle that has been put into an emergency stop rotates slightly due to the +i characteristic, but the automatic movement that moves the spindle in the axial direction Since the inertia of the feed mechanism also acts, there is a problem in that the stopped drill is fed and the drill may break.

[Means for solving problems]

In order to solve the above problems, the present invention rotatably attaches a tool mounting shaft within a cylindrical body of a tool holder body which is detachably attached to the main axis of a machine tool such as a machining center, The cylindrical body and tool mount shaft are engaged together until the resistance applied to the mount shaft reaches a set value, and when the resistance applied to the tool mount shaft exceeds the set value, the tool mount shaft is moved in the axial direction relative to the cylindrical body. and a coupling means that allows the tool to be freely rotated in either direction, and a detection means that issues an abnormal signal such as stopping the rotation of the main shaft when the resistance applied to the tool mounting shaft exceeds a set value. .

[Effect]

Since this invention has the above configuration, a tool holder with a tool such as a drill attached to the lower end of the tool mounting shaft is attached to the main shaft of a machine tool, and operations such as drilling a hole in a desired workpiece are performed by rotation of this main shaft. In this state, when machining is performed normally, the cylindrical body and the tool mounting shaft are connected and rotate as one.

However, if abnormally large resistance acts on the tool mounting shaft for some reason, the rotation of the tool mounting shaft lags behind the rotation of the cylinder. As a result, the coupling between the cylinder and the tool mounting shaft by the coupling means is displaced.

When the coupling between the cylindrical body and the tool mounting shaft is disengaged as described above, the coupling means is removed, and the tool mounting shaft becomes free with respect to the cylindrical body in the axial and rotational directions.

In addition, when the cylinder and the tool mounting axis become misaligned as mentioned above, the detection means also works to stop the main spindle of the machine tool, but due to inertia, the main spindle rotates slightly together with the cylinder, etc., and the feed mechanism of the main spindle also has inertia. Therefore, the cylinder moves slightly after the abnormality occurs.

However, in the case of the device of this invention, as soon as the abnormality occurs, the tool mounting shaft becomes free in both the axial and circumferential directions with respect to the cylinder, so the cylinder rotates slightly due to inertia. Even when moving in the axial direction, there is no risk of the drill biting into the workpiece.

〔Example〕

In the embodiment shown in FIG. 1, 1 is a non-rotating part of a machine tool body such as a machining center, and 2 is a main shaft driven by a suitable driving means. 3 is a tool holder, and a rotating member 4
and a non-rotating support member 5 that supports this rotating member.

A tapered shank 6 that fits into the tapered hole of the main shaft 2 is provided at the upper part of the rotating member 4. The lower part of this Taber shank is AT
The holding portion 7 has a circumferential groove into which the claw of the manipulator C fits, and its lower end is integrally screwed into the rotating member 4.

The rotating member 4 has a cylindrical shape, and a tool mounting shaft 8 is installed inside the rotating member 4 through front and rear slide bearings 9 and 10. Both are free.

11 is a coupling means for coupling the member 4 and the tool mounting shaft 8;
This coupling means 11 includes a ball 12, a protrusion 13 integrally provided on the outside of the tool mounting shaft 8 to receive the ball, and
It consists of a spring 15 and a spring receiver 16 that press the ball 12 against a recess 14 provided in the protrusion 13.

The above-mentioned recess 14 has a concave spherical shape, and the protrusion 13 has a concave spherical shape.
It is shaped like a crater, surrounding it.

Further, an adjustment cylinder 18 supported by a support nut 17 screwed here is rotatably mounted on the front end of the member 4, and the outer end of the spring receiver 16 is crimped to the support part 19 on the inner circumference of the adjustment cylinder 18. let When there are two protrusions 13 as shown in Fig. 2, this support part 19 is formed in two places within a range of about 180°, which gradually deepens from one end so as to form part of a spiral. As shown in FIG. 3, there is one in which support portions 19 are provided at regular intervals in the form of a plurality of arc-shaped recesses that are deepest at positions separated by 180° and gradually become shallower.

In the case shown in Fig. 2, as the adjusting cylinder 18 is turned in the direction of the arrow from the position shown in Fig. 2, the spring 15 is gradually compressed and the recess 1
Although the pressure of the ball 12 against 4 becomes stronger, the adjustment cylinder 18
In order to fix it in a desired position, a set screw 20 screwed into a screw hole provided in a part of the adjustment tube 18 is pressed onto the support nut 17 as shown in FIG.

In the case of FIG. 3, the adjustment tube 18 is fixed to each support portion 19, so a set screw is not required.

In the embodiment, a detection means that utilizes pressure changes in compressed air is shown.

That is, the tool mounting shaft 8 has an exhaust hole 2 that crosses the center thereof.
A sleeve 26 fixed between the tool mounting shaft 8 and the rotating member 4 is provided with communication holes 27 in the radial direction opposite to the exhaust hole 25, and one communication hole 27 is provided in the axial direction on the outside of the sleeve 26. This groove 28 is opened to the outside air through an exhaust path 29 provided in the tool holder 3, and one communication hole 27 is communicated with a communication hole 30 provided in the rotating member 4.

Reference numeral 31 denotes an annular member fixed to the inner periphery of the non-rotating support member 5, and the inner periphery of this member 31 is in airtight contact with the outer periphery of the communication hole 30 of the rotating member 4.

A circumferential groove communicating with the communication hole 30 is formed all around the inner circumference of the annular member 31, and a communication hole 32 in the radial direction communicating with this circumferential groove is provided in the member 31.

An example of the non-rotating support member 5 is provided with a protruding fluid receiving part 35, and the lower part of the engaging pin 36 is fitted into a vertical hole passing through the receiving part 35 vertically. The large diameter lid 38 is fixed.

An engaging portion 33 into which the engaging pin 36 is fitted is provided on the lower surface of the non-rotating portion 1, and the upper portion of the engaging pin 36 is fitted into the engaging portion 33, and a sliding member is pressed against the lower surface of the non-rotating portion 1 by a spring 34. The moving body 37 is provided with an air inlet 40 having a check valve 39, and this inlet 40 is communicated with a communication passage 41 provided in the pin 36, and the fluid receiving portion 35 is connected with the communication passage 41 and the communication hole 32. A communication path 42 is provided to allow the

Further, the non-rotating portion 1 is provided with an air supply path 43 communicating with the air introduction port 40.

In addition to the above configuration, the embodiment also includes fixing means for fixing the rotating member 4 to the non-rotating support member 5 when the shank 6 of the tool holder 3 is removed from the main shaft 2, and a means for supplying coolant fluid. However, detailed explanation will be omitted.

Although not shown, the air supply path communicating with the air supply path 43 leads to a compressed air source consisting of a compressor, a receiver tank, etc., and a pressure sensor is provided at a branch path in the middle thereof. This pressure sensor is like a pressure switch, and is connected to a control amplifier, from which a control signal for the machining center is transmitted.

Further, a solenoid valve is provided between the supply path 43 and the air supply path, and a circuit is configured such that the solenoid valve opens under the condition that the tool holder 3 is attached to the main shaft 2.

Next, to explain the operation of the above embodiment, the shank 6 of the tool holder 3 is fitted into the main shaft 2 using a tool changer or the like, and when the main shaft 2 starts rotating with the solenoid valve open, it is attached to the tool mounting shaft 8. Machining of the workpiece begins with a tool (not shown), but while the machining is being performed normally, the ball 12 fits into the recess 14 as shown in Figures 1 to 3, and the tool mounting shaft 8 and rotating member 4 are Ball 12 and recess 14
Since the mounting shaft 8 and the member 4 rotate together through engagement and maintain a constant positional relationship, the communication hole 27 is communicated with the exhaust path 2S through the exhaust hole 25 as shown in FIG. .

In this state, compressed air from the compressed air source is supplied to the supply path 43-
Check valve 3S - Air inlet 40 Series of passages 41 Series of passages 42
The air flows through the communication hole 32 - the exhaust hole 25 and is discharged from the groove 28 to the outside air via the exhaust path 29, so the air pressure in the air path is maintained at a normal value and the pressure sensor does not work.

During such machining operations, if the resistance applied to the tool mounting shaft 8 increases to a certain value or more due to drill wear, poor drill selection, chip clogging, etc., the tool mounting shaft 8 as shown in FIG. Ball 1 from recess 14 provided in protrusion 13
2 comes off as shown in Figures 4 and 5.

In this way, the ball 12 comes off from the recess 14 and the tool mounting shaft 8 no longer follows the rotation of the member 4 (then the exhaust hole 25 and the communication hole 27 are shifted from each other, and the exhaust hole 25 is blocked).

When the exhaust hole 25 is shut off in this way, the air pressure in the air supply path rises rapidly, the pressure sensor detects this, and the signal is sent to the control amplifier, which is amplified and sent to the control section of the machining center. is input to stop the spindle 2.

In this way, when the main shaft 2 stops, an alarm such as an audible beep or a high-lot lamp is activated to notify the user of an abnormal condition, so that this part can be inspected or the adapter replaced.

In addition, in the case of unmanned operation late at night, if an output signal is issued from the control amplifier and the spindle stops, the tool changer will operate and replace the tool with a spare tool holder, which will reduce the amount of time the manning center will be stopped due to an abnormal situation. It can be done in the shortest possible time.

As mentioned above, there is a slight time lag from the moment the exhaust hole 25 is blocked until the spindle 2 stops due to the signal from the control unit of the manning center, and there is also the inertia of the spindle 2, tool holder 3, etc. Although it takes some time for the main shaft 2 to completely stop, and there is also a slight delay in stopping the axial feed, in the case of this invention, the ball 12 comes off the recess 14 as described above. Then, this ball 12 moves to a state where it comes into contact with the outer peripheral surface of the cutting tool mounting shaft 8 at the front part of the protrusion 13, as shown in FIGS. 5 and 6.

Therefore, as soon as an abnormality occurs, the tool mounting shaft 8 becomes free in both the axial and rotational directions with respect to the rotating member 4, and retreats relative to the rotating member 4, so even if the main shaft continues to rotate 20 times or feed a little, the cutting tool cannot be mounted. No torque or thrust load acts on the shaft 8, preventing breakage of drills, etc.

FIG. 7 shows another embodiment, and different parts, that is, mainly the coupling means will be explained.

In this case, the outside of the ball 12 is sandwiched between an annular seat 45 and an annular pressing member 46. The pressing member 46 is a spring receiver 47
The rear part of this spring receiver 47 is supported by a ring 52 inside the rotating member 4, and
In this receiver, the projecting pieces 4S on both sides of the ring 52 are inserted into axial guide holes provided in the member 4, so that they can move forward and backward with respect to the member 4, but cannot rotate, and are slidably fitted to the outside of the member 4. screw import 50
The protruding piece 4S is engaged with the engagement notch 51 provided in the front part.

Further, the female thread of an adjustment cylinder 54 rotatably fitted on the outside of the member 4 is screwed into the male thread of the screw port 50, and the rear end of this adjustment cylinder 54 is supported by the holding part 7 of the tool holder 3. As the threaded ring 50 moves forward and backward due to the rotation of the adjustment cylinder 54, the receiver moves the ring 52 and the spring receiver 47 forward and backward, and the spring 48
Adjustments should be made.

Further, in this embodiment, the exhaust passage 29 is opened at the lower end surface of the rotating member 4.

In this embodiment, when the resistance applied to the tool mounting shaft 8 exceeds the limit, the pressing member 46 compresses the spring 48 and escapes to the right in FIG. Move to the outer periphery.

Therefore, the mounting shaft 8 becomes free with respect to the rotating member 4, and on the other hand, a pressure switch (not shown) is activated due to the misalignment between the exhaust hole 25 and the exhaust path 2S.

In each of the above embodiments, a pneumatic cutoff method was shown as a means of detecting an abnormality, but the opposite method is used, in other words, the exhaust path is shut off in a normal state, and the exhaust path is opened in an abnormality, and the pressure is reduced by a pressure sensor. The same thing can be done even if the abnormality is detected by detecting.

Further, as a means for detecting that the resistance applied to the tool mounting shaft 8 exceeds a set value, in addition to the method using a change in compressed air pressure as in the embodiment, any method such as an electric method can be used.

FIG. 8 is a graph illustrating the operating state of each of the above embodiments, in which the vertical axis shows the feed rate of the drill and the horizontal axis shows the passage of time from left to right.

In the above graph, if an abnormality occurs at point a while cutting pressure is being applied at a constant feed rate from point 0, the coupling means 11 will separate at point b with a slight delay.

In the case of this invention, immediately after the coupling means 11 is separated, the tool mounting shaft 8 becomes free as described above, and the feed of the drill etc. becomes almost zero at point C.

Then, the pressure sensor is activated at point d, and a stop signal is issued at point e.

Conventionally, the tool mounting shaft and tool holder are constrained in the axial direction until the tool stops at one point after a certain amount of time has passed from this point, so if the main spindle is moving quickly in the axial direction,
The feed action of the spindle until the spindle stops causes feed to be applied to the tool mounting shaft, which may damage the tool.

〔effect〕

As described above, this invention provides that when the resistance applied to the tool mounting shaft during cutting becomes abnormally large, the coupling means separates.
The tool mounting shaft is free both in the axial direction and in the rotational direction relative to the rotating member of the tool holder.

Therefore, even if the tool mounting axis suddenly stops during cutting with fast feed, even if the main spindle continues to feed for a while due to the time lag of the emergency stop device or the inertia of each part, the tool mounting shaft will not reach the tool holder. This has the unique effect of eliminating the risk of breakage of the tip of the drill because it moves backwards.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional side view of the main part showing an embodiment of the device of the present invention;
FIG. 2 is an enlarged cross-sectional view of the coupling means, FIG. 3 is an enlarged cross-sectional view showing another example of the same part, FIGS. 4 and 5 are enlarged cross-sectional views showing the action of the coupling means, and FIG. FIG. 6 is a longitudinal side view showing a separated state of the coupling means, FIG. 7 is a partially cutaway side view showing another embodiment, and FIG. 8 is a graph showing the operation. 2...Spindle, 3...Tool holder, 4
...Rotating member, 8... Tool mounting shaft, 1
1...Coupling means, 12...Ball, 1
3... Protrusion, 14... Concavity, 15...
...Spring, 45...Catch, 46...
・Press member, 47... Spring holder, 4th...
·Spring.

Claims (1)

[Claims] The tool mounting shaft is rotatably mounted within the rotating member of the tool holder, which is detachably attached to the main shaft of the machine tool. When the resistance applied to the tool mounting shaft exceeds a set value, the tool mounting shaft is integrally engaged with the shaft, and a coupling means is provided that allows the tool mounting shaft to move freely in both the axial and rotational directions relative to the cylinder. A tool abnormality prediction device comprising: a detection means for generating an abnormality signal such as stopping rotation of the main shaft when resistance applied to the shaft exceeds a set value.