JPH11333657A - Abnormality monitoring device for tool change operation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device to monitor abnormal phenomenon of tool change operation due to the manufacture error of a tool change arm and prevent the damage of a machine tool and a work. SOLUTION: The torque waveform pattern of a drive motor 1 during the normal effect operation of a tool change arm is stored at a memory circuit 2. By comparing this torque waveform pattern with a torque waveform pattern storing the torque waveform pattern of a drive motor 1 under current operation by a comparing circuit 4, propriety is decided. Further, the rate of change of a time of a torque waveform pattern during normal operation is stored at a memory circuit 8, and compared with the rate of change of a time of the torque pattern of a drive motor during current operation. In a case of no- coincidence therebetween, the rate of change of a time of motor torque under current operation is added the given number of times and compared with a torque waveform pattern during normal operation to decide propriety.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for monitoring an abnormal change of a tool changing arm in an automatic tool changing apparatus of a numerically controlled machine tool. The present invention relates to a device for detecting an abnormality in a tool changing operation by detecting a torque waveform pattern of a driving motor in the above and comparing the torque waveform pattern of the driving motor during a normal operation of a tool changing arm.

[0002]

2. Description of the Related Art First, an example of an automatic tool changer is shown in FIGS.
It will be described based on the following. FIG. 5 is an explanatory view showing a state in which a used tool mounted on the main spindle is replaced with a next tool indexed to a tool replacement position in the magazine.

A spindle 102 is vertically mounted in a spindle head 101 so as to be rotatable and positionable, and a used tool T1 is mounted on a lower end of the spindle 102. And the spindle 10
Numeral 2 is stopped at a predetermined angular position, and the used tool T1 is maintained by dividing a key groove position into a predetermined angular position by a key 103 fixed to a tip of the main shaft 102.

[0004] In a tool magazine (not shown), a number of tools are stored with key grooves at predetermined angular positions. At the indexing position 104, the next tool T2 is maintained in a state where the angular position of the key groove is maintained in a constant direction from the tool magazine (not shown).
Is held and positioned.

[0005] A tool change arm 105 used for changing the two tools T1 and T2 has grippers 105a and 105b for gripping the tool at both ends, and pivots at a central portion at right angles to the arm 105 in the vertical direction. A shaft 107 is provided.

FIG. 6 is a skeleton diagram showing a driving mechanism of the tool changing arm 105. The center turning shaft 107 of the tool changing arm 105 is formed as a ball screw spline shaft, and the ball screw nut 108 meshing with the ball screw portion 107a is prevented from moving in the ball screw axial direction so that it can rotate only. It is attached to the body. The ball screw nut 108 has a gear 1
The gear 109 meshes with a gear 111 fixed to an output shaft of a servomotor 110 for tool insertion and removal attached to a main body (not shown). Further, a position detector 112 for detecting a rotation angle position of an output shaft of the motor is attached to the servomotor 110 for tool insertion and removal.

The spline portion of the ball screw spline shaft 107 is meshed with a spline nut 113. The spline nut 113 is also prevented from moving in the axial direction of the ball screw and is attached to a tool changer body (not shown) so that it can rotate only. I have. The spline nut 1
Reference numeral 13 has a gear 114 on the outer periphery. The gear 114 is a gear 117 fixed to an output shaft of a speed reducer 116 connected to an output shaft of a servomotor 115 for rotating the exchange arm 105 attached to a main body (not shown) and an intermediate gear. Meshing via 118. A position detector 119 for detecting the rotation angle position of the output shaft of the motor is attached to the servo motor 115 for turning the exchange arm 105.

Therefore, the servomotor 11 for tool insertion and removal
When 0 rotates by a predetermined angle, the ball screw nut 109 rotates and the ball screw spline shaft 107 moves in the axial direction, and the grippers 105a, 105 at both ends of the exchange arm 105
The tools T1 and T2 grasped by b are inserted and removed. Further, when the servo motor 115 for turning the replacement arm 105 rotates by a predetermined angle, the spline nut 113 rotates, and the ball screw spline shaft 107 rotates accordingly, whereby the replacement arm 105 is turned.

The case where such a tool change arm 105 causes various errors at the time of manufacture will be described item by item with reference to FIG.

(1) Center 1 of rotation of tool change arm 105
In the case where there is a slight dimensional error in the distances L1 and L2 from 05c to the gripping centers of the tool grips of both end grippers 105a and 105b (FIG. 7A). (2) When the tool change arm 105 is turned to position the grippers 105a and 105b at both ends at a predetermined position at an angle, a slight stop position error occurs in the circumferential direction between the grippers 105a and 105b at both ends [FIG. (B), FIG. 7 (c)]. (3) When the gripper 105a and 105b at both ends are angularly positioned at predetermined positions by rotating the tool change arm 105, a slight stop position error occurs in the tool axis direction between the grippers 105a and 105b at both ends [FIG. d),
FIG. 7 (e)].

Each case of the above-mentioned manufacturing error will be described. In the case of (1); as shown in FIG.
When the gripper 105a having a long distance L1 from the gripper 105c grips the tool T1, the root side of the gripper 105a is
As a result, the tool T1 cannot be gripped over the entire inner periphery of the gripper. Therefore, the grip of the tool T1 becomes unstable. In addition, the tool T1 is pressed toward the tip end of the exchange arm 105, and the gripper 105a receives a force in the direction of decreasing the distance from the turning center 105c as a reaction force of this pressing.

When the gripper 105b having a short distance L2 from the turning center grips the tool T2, the gripper 1
The tip of 05b contacts the V-groove of the tool T2, so that the tool T2 cannot be gripped on the entire inner peripheral surface of the gripper. Therefore, the grip of the tool T2 becomes unstable. In addition, the tool T2 is pressed toward the turning center 105c of the exchange arm 105, and the gripper 105b receives a force in the direction of increasing the distance from the turning center 50a as a reaction force of this pressing.

As a turning motor of the exchange arm 105, the exchange arm 105 gradually receiving such a reaction force is rotated to the positioning position immediately before the gripping of the tools T1 and T2, and the motor torque is different from the normal value. Becomes Further, as the insertion / removal motor 110 of the exchange arm 105, the tool T1 or T2 is pressed by the exchange arm 105, and the tool T1 is inserted or removed while the shank portion of the tool T1 or T2 is pressed against, for example, a tapered hole of the main shaft 102. The motor torque must be different from the normal value.

In the case of (2), as shown in FIG. 7 (b), the exchange arm 105 is pivoted to grippers 105a and 105
When b is angularly positioned at a regular position, an angular error θ
When one of the gripper 105a by ₁ is to have stopped in a state of pressing strongly the tool T1, the gripper 105a is subject to reaction force to the turning circumference of the exchange arm 105 by the tool T1.

Therefore, the swing motor 1 of the exchange arm 105
As for 15, the exchange arm 105 gradually receiving such a reaction force is rotated to the positioning position immediately before gripping the tool T1, and the torque value of the rotation motor 115 becomes a value different from the normal value. In addition, as the insertion / removal motor 110 of the exchange arm 105, the tool T1 must be pulled out in a state where the tool T1 is pushed by the gripper 105a and the shank portion of the tool T1 is pressed, for example, by the tapered hole of the main shaft 102. The torque value of the motor 110 is also different from the normal value.

On the contrary, as shown in FIG.
When the gripper 105a and the tool T1 are stopped at a position slightly apart from the tool T1 due to the angular error θ2 when the gripper 105a and the tool T1 are angularly positioned by rotating the 05. There is no gap between them and no excessive force acts. Therefore, the motor torque values of both the rotation motor 115 and the insertion / removal motor 110 of the exchange arm 105 become normal values. However, the gripper 105a grips the tool T1 in an unstable state, and for example, there is a possibility that the tool T1 may drop when the tool T1 is pulled out from the spindle 102.

In the case of (3), as shown in FIG. 7D, when one gripper 105a is displaced by a distance α toward the tip end of the tool T1 in the main axis direction of the tool T1, the tool T1 moves in the axial direction. Immediately before the end of the rotation of the exchange arm 105, the V-shaped projecting portion 105d provided on the entire inner periphery of the gripper 105a comes into contact with the lower slope of the V-groove of the tool T1, and the tool T1 is extracted. Receives pressing force in the direction.
The gripper 105a receives a force in the tool shank direction as a reaction force of the pressing force.

As shown in FIG. 7 (e), when one gripper 105a is displaced by a distance β toward the shank side of the tool T1 in the axial direction of the tool T1, the gripper 105a immediately before the end of the turning of the exchange arm 105. The protruding portion 105d having a V-shaped cross section provided on the entire inner circumference thereof comes into contact with the upper slope of the V-groove of the tool T1, and the tool T1 receives a pressing force in the shank direction.
As a reaction force of this pressing force, the gripper 105a receives a force in the tool extracting direction. When there is no displacement at all, FIG.
In both (d) and (e), the protruding portion 105 is at the position of the virtual line.

As the turning motor 115 of the changing arm 105, the changing arm 105 which gradually receives such a reaction force immediately before gripping the tool T1 is turned to the positioning position, and the torque value of the turning motor 115 becomes a normal value. And a different value. Removal / insertion motor 11 for exchange arm 105
If the tool T1 is pushed in the shank direction as shown in FIG. 7E, the shank portion of the tool T1 may bite into the tapered hole of the main shaft 102. The operation requires a large torque, and the torque value is different from the normal value.

In the tool change arm 105 having a manufacturing error as described above, various pressing forces act on the grippers 105a and 105b at the time of pivoting positioning for gripping the tool, and therefore unnecessary portions of the tool change arm 105 are required. An excessive force will be applied, an abnormal condition will occur, and sudden damage will occur during repeated use.

[0021]

A technique for monitoring an abnormality of a replacement arm as a method for preventing damage described in the prior art has not been developed yet. For this reason, there has been a problem that the replacement arm is suddenly damaged, and there is a possibility that the tool is dropped and the tool is damaged, and the dropped tool may damage the workpiece or the machine tool. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to monitor an abnormal phenomenon caused by a manufacturing error of an exchange arm, predict damage to the exchange arm, and prevent damage. It is intended to provide a device to prevent such a problem.

According to a first aspect of the present invention, there is provided an apparatus for monitoring an abnormality in a tool changing operation of a machine tool, comprising: A storage circuit that stores a waveform pattern, a detection circuit that detects a torque waveform pattern of a driving motor during a tool changing operation, and a comparison between an output waveform pattern of the storage circuit and an output waveform pattern of the detection circuit. A comparison circuit for obtaining an error amount of the torque value at the same position during the exchange operation of the tool exchange arm, and an error amount of the torque value output from the comparison circuit being an allowable range for the output waveform pattern of the torque waveform pattern storage circuit. And a judgment circuit for judging whether or not it exists in the inside.

According to the above-described apparatus, the motor torque waveform pattern during the current operation is compared with the set width for the motor torque waveform pattern during the normal operation to determine whether the current torque is within the set width. Abnormal conditions that deviate from are immediately detected and dealt with immediately to prevent an accident.

According to a second aspect of the present invention, there is provided an apparatus for monitoring an abnormality of a tool changing operation of a machine tool, wherein the pattern of a torque waveform of a driving motor relating to a tool changing operation during a normal operation of a tool changing arm is changed. Tool change operation of the arm A memory circuit that stores the time rate of change calculated for the instantaneous torque value at each position and the pattern of the torque waveform of the drive motor during the tool change operation Tool change operation of the tool change arm A calculation circuit for calculating a time change rate with respect to an instantaneous torque value at each position, and comparing a time change rate of the torque value output from the storage circuit with a time change rate of the torque value output from the calculation circuit; A comparison circuit
A judgment circuit for judging whether or not an output of the calculation circuit is different from an output of the storage circuit as a result of comparison in the comparison circuit; An arithmetic circuit for repeatedly adding a torque value having the same rate of change to the time rate of change output from the calculation circuit in the future for a predetermined number of times; and a torque waveform output from the arithmetic circuit for a torque waveform pattern in a normal operation. A judgment circuit for judging whether or not it is within an allowable range.

According to the above-described apparatus, the time change rate of the motor torque value during the current operation is predicted and calculated after the specified number of repetitions, and the calculation result is used to calculate the motor torque waveform pattern during the normal operation. Abnormality is predicted in comparison with the set width for the motor, so that even if the time change rate of the motor torque during the current operation is within the set width of the motor torque waveform pattern during the normal operation, the abnormality is detected early. It is possible to predict and prevent damage in advance.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a torque waveform pattern (a) of the driving motor 1 when the tool changing arm performs a normal changing operation, and a torque waveform pattern (b) of the motor 1 when the tool changing arm performs an abnormal operation. It is the figure which showed typically.

A predetermined allowable torque range is set for the normal torque waveform pattern (a), and when the torque waveform pattern of the motor 1 currently operating deviates from this set range, abnormal operation of the tool change arm is performed. Thus, the motor 1 is stopped, and an alarm signal is issued to notify the operator.

FIG. 2 shows the motor 1 currently operating in FIG.
Even if the torque waveform pattern is within the set range, if there is a possibility that the torque waveform pattern will eventually run out of the set range, a process such as stopping the motor 1 in advance is performed. FIG. 6 is a diagram schematically showing a state to be attempted. That is, a change rate per unit time (hereinafter, simply referred to as a time change rate) of the torque value of the operating motor 1 is obtained. This rate of change is compared with the time rate of change of the torque waveform pattern (a) of the motor 1 during normal operation. If they do not match, the torque value, which is the rate of change of the torque waveform pattern of the motor 1 currently operating, is added a predetermined number of times to determine whether or not the torque value is within the set range. To predict whether or not an abnormal state will occur. Therefore, FIG. 2 shows a state in which the motor 1 is stopped at the point A in anticipation that the time rate of change (c) with respect to the torque value of the currently operating motor 1 at the point A will exceed the set range at the point B in the future. ing.

FIG. 3 is a block line showing a control for detecting a waveform pattern of the motor torque during the replacement operation of the driving motor 1 to monitor an abnormality in the replacement operation of the tool replacement arm and stopping the motor in the case of an abnormality. FIG.

When the tool change operation of the tool change arm is performed normally, a torque waveform pattern corresponding to the lapse of time of the motor torque value is detected in advance and stored in the storage circuit 2. Then, the detection circuit 3 detects the torque waveform pattern of the driving motor 1 during the replacement operation, and compares the torque waveform pattern of the storage circuit 2 with the comparison circuit 4 to obtain the error amount of the torque waveform pattern during the operation. . A determination circuit 6 determines whether or not this error amount is within an allowable range of an allowable range setting circuit 5 for the torque waveform of the storage circuit 2.
Determined by. If the error amount is within the allowable range, a signal to continue the motor rotation is sent to the motor control unit 7, and if the error amount is outside the allowable range, a signal to stop the motor rotation is sent to the motor control unit 7. Further, with respect to the motor torque waveform pattern at the time of normal operation, which is the output of the storage circuit 2, the time change rate of the instantaneous torque value at each position of the tool change arm is calculated and stored in the storage circuit 8.

On the other hand, with respect to the torque waveform of the motor, which is the output of the detection circuit 3, the calculation circuit 9 calculates the time change rate with respect to the instantaneous momentary torque value at each position of the tool change arm during the tool change operation. The output of the storage circuit 8 and the output of the calculation circuit 9 are compared by a comparison circuit 10, and a determination circuit 11 determines whether or not the comparison results match. If they match, the determination circuit 11 sends a signal to the motor control unit 7 to continue the motor rotation. If they do not match, the same time change rate value is predicted to occur repeatedly in the future, and the time change rate value of the torque value at the change operation position of the tool change arm that does not match is calculated. The circuit 12 performs addition for a predetermined number of repetitions determined by experiments or the like.

The determination circuit 1 determines whether or not the torque value output from the arithmetic circuit 12 is within the allowable range of the allowable range setting circuit 5 for the torque waveform pattern of the storage circuit 2.
Determined in 3. If the torque value output from the arithmetic circuit 12 is within the permissible range, a signal to continue the motor rotation is sent to the motor control unit 7, and if the torque value is out of the permissible range, a signal to stop the motor rotation is sent to the motor control unit 7. Send. When a signal for stopping the rotation of the motor is sent from at least one of the determination circuit 6 and the determination circuit 13, the motor control unit 7 stops the rotation of the motor 1 and simultaneously issues an alarm signal to call attention to the worker. .

FIG. 4 is a flowchart showing an operation procedure for monitoring an abnormal change of the tool changing arm.

In step S1, the detection circuit 3 detects a torque waveform pattern of the drive motor 1 during the replacement operation of the replacement arm. In step S2, the comparison circuit 4 compares the torque waveform pattern detected in step S1 with the torque waveform pattern during normal operation stored in the storage circuit 2. In step S3, the determination circuit 6 determines whether or not the difference between the output value of the comparison result detection circuit 3 and the output value of the storage circuit 2 in step S2 is within an allowable range for the torque waveform pattern of the storage circuit 2. Judgment. If YES, the process moves to the next step. If NO, step S
Move to 9.

In step S4, the time change rate of the torque waveform pattern detected in step S1 is calculated by the calculation circuit 9 with respect to the instantaneous torque value at each position of the tool change operation of the tool change arm. In step S5, the comparison circuit 10 compares the time change rate calculated in step S4 with the time change rate for the torque waveform pattern when the tool change operation is normal stored in the storage circuit 2.

In step S6, as a result of the comparison in step S5, the determination circuit 11 determines whether the two rates of change match. In the case of YES, the process returns to step S1 to perform the above operation. In the case of NO, the process moves to the next step. In step S7, the value of the time rate of change obtained in step S4 is repeatedly added a predetermined number of times by the arithmetic circuit 12.

In step S8, the determination circuit 13 determines whether or not the torque value obtained as a result of the calculation in step S7 is within an allowable range for the torque waveform pattern in the storage circuit 2. In the case of YES, the process returns to step S1 to perform the above operation. In the case of NO, the process proceeds to the next step. In step S9, the motor control unit 7 stops the drive motor 1 and simultaneously issues an alarm signal to warn the operator.
This completes the operation. Note that the present invention can be applied to both the motor for turning the tool changing arm and the motor for inserting and removing the tool changing arm.

In practicing the present invention, a torque waveform pattern is stored for each tool stored in the tool magazine of the machine tool in order to take account of the weight difference, and when the tool is replaced, Needless to say, it can be appropriately changed without departing from the gist of the present invention, such as using a torque waveform pattern adapted to a tool to be used.

[0039]

Since the apparatus according to the present invention is constructed as described above, the following effects can be obtained.

According to the first aspect of the present invention, the motor torque waveform pattern at the time of the normal change operation of the tool change arm is provided with an allowable set width, and the torque waveform pattern of the active motor is compared with the current motor torque waveform pattern. Is determined to be abnormal when it comes out of the set width, and the motor is stopped.Even if it goes out of the allowable set width, the tool change arm is not immediately damaged, but at this point, the motor is stopped. Stopping can prevent damage.

According to a second aspect of the present invention, the time change rate of the motor torque waveform pattern at the time of the normal change operation of the tool change arm is compared with the time change rate of the motor torque value currently in operation, and the two change rates are inconsistent. In the case that it is predicted that the same rate of change will occur repeatedly in the future with respect to the time change rate of the operating motor torque value, this torque value is repeatedly added a predetermined number of times, and the motor torque waveform when the added torque value is normal Is determined to be within an allowable range with respect to, and the operation of the motor is controlled. Even if the motor torque waveform pattern does not deviate from the normal motor torque waveform pattern, if the time change rate is expected to eventually deviate from the allowable setting range of the normal motor torque waveform pattern, damage prevention You can do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing motor torque waveform patterns in a normal state and an abnormal state.

FIG. 2 is a diagram showing a motor torque time change rate at an abnormal time with respect to a motor torque waveform pattern at a normal time.

FIG. 3 is a block diagram showing control for monitoring an abnormality of a tool changing operation and stopping a motor.

FIG. 4 is a flowchart showing an operation procedure for monitoring an abnormality in a tool changing operation.

FIG. 5 is an explanatory diagram showing a relationship between a spindle, a ready station, and a tool changing arm according to the related art.

FIG. 6 is an explanatory diagram of a driving relation of a tool changing arm according to the related art.

FIG. 7 is an explanatory diagram of a manufacturing error of the tool changing arm.

[Explanation of symbols]

1 Rotating motor 2 Normal torque waveform pattern storage circuit 3 Monitoring torque waveform pattern detection circuit 4, 10 Comparison circuit 8 Normal operation torque waveform pattern time change rate storage circuit 9 Torque waveform pattern time change rate during operation Calculation circuit 12 Operation circuit

Claims (2)

[Claims] An apparatus for monitoring an abnormality of a tool change operation of a machine tool, comprising: a storage circuit for storing a torque waveform pattern of a driving motor related to a tool change operation during a normal operation of a tool change arm; A detection circuit for detecting a pattern of a torque waveform of the driving motor during operation, and comparing an output waveform pattern of the storage circuit with an output waveform pattern of the detection circuit at the same position during the replacement operation of the tool change arm. A comparison circuit for determining an error amount of the torque value, and a determination circuit for determining whether or not the error amount of the torque value output from the comparison circuit is within an allowable range for the output waveform pattern of the torque waveform pattern storage circuit And an abnormality monitoring device for a tool changing operation. 2. An apparatus for monitoring an abnormality of a tool changing operation of a machine tool, comprising: a tool changing operation of a tool changing arm with respect to a pattern of a torque waveform of a driving motor related to a tool changing operation at a time of a normal operation of the tool changing arm. A memory circuit that stores the time rate of change calculated for the instantaneous torque value at the position, and the torque waveform pattern of the driving motor during the tool change operation. A calculation circuit for calculating a time change rate with respect to the torque value, a comparison circuit for comparing the time change rate of the torque value output from the storage circuit with the time change rate of the torque value output from the calculation circuit, A comparison circuit that determines whether an output of the calculation circuit is different from an output of the storage circuit as a result of comparison in a comparison circuit; An arithmetic circuit for repeatedly adding a torque value having the same rate of change to the time rate of change output from the calculating circuit at the same position during the replacement operation of the tool changing arm a predetermined number of times; and a torque value output from the arithmetic circuit. And a determination circuit for determining whether or not is within an allowable range for the torque waveform pattern in a normal operation.