JPH10263973A - Gravity shaft falling down prevention device at time of power failure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a gravity shaft from falling down due to power failure, and thereby prevent tools, works and the like from being damaged. SOLUTION: When power failure is detected by a power failure detection circuit provided in a power supply circuit 10, a detection signal S1 is outputted to a CNC 7, and respective motor control circuits 14 through 16. The respective motor control circuits 14 through 16 executes deceleration control with a speed command (or moving command) forcibly set at zero. As a result, a spindle motor and servo motoers MZ and MX are decelerated by great torque. Besides, when a power failure detection signal S1 is inputted in the CNC 7, the CNC allows a switch 9 to be turned off, and also allows the brake to be applied to a gravity shaft by a braking device Br. Since the servo motor MZ of the gravity shaft is being decelerated so as to be controlled by great torque until braking becomes effective after power has been failed, the gravity shaft is thereby prevented from falling down to the utmost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine such as a machine tool or a robot having a shaft which may move under the influence of gravity (hereinafter referred to as a "gravity axis"). The present invention relates to a power failure prevention control device.

[0002]

2. Description of the Related Art In a machine having a gravity axis, when the power to a servomotor for driving the gravity axis is cut off due to a power failure or the like, the gravity falls by gravity. As a method of preventing the natural fall, a servo motor for the gravity axis is provided with a brake device, and when a power failure occurs, the brake device is actuated to apply a brake to the servo motor, thereby causing the gravity axis to fall. Has been prevented.

FIG. 4 shows an example of a machine tool having a gravity axis. Reference numeral 1 denotes a spindle, and the spindle 1 is driven by a spindle motor Ms to rotate a tool 2 attached to the spindle 1.
The main shaft 1 is driven in the gravity axis direction (Z-axis direction) by a feed screw mechanism 3 such as a ball screw / nut mechanism by a gravity axis servomotor Mz. The gravity servomotor M
A brake device Br is attached to the z, and when the operation of the machine is stopped and the power is cut off, the brake device Br operates to drop the gravity axis, that is, the main shaft 1 and the main shaft motor Ms.
Etc. are prevented from falling naturally. Sign M
x is an X-axis servomotor that drives the table T on which the work W is mounted in a horizontal direction via a feed screw mechanism 4 such as a ball screw / nut mechanism.

Reference numeral 6 denotes a rectifier circuit for rectifying single-phase AC power and converting it to DC. The output of the rectifier circuit 6 is input to a brake device Br via a switch 9 to drive the brake device Br. It has become. The output of the rectifier circuit 6 is supplied to a control power supply circuit 8, where the voltage and the like are adjusted, and the spindle motor Ms, the servo motors Mz, Mx
Power for control is supplied to the spindle motor control circuit 14 and the servo motor control circuits 15 and 16 for driving and controlling the motor.
Spindle motor control circuit 14, servo motor control circuit 15,
Numeral 16 is a feedback control of a speed and a position in response to a speed command and a movement command from a numerical controller (CNC) 7 (a speed detector, a servo motor Mz, M
x is provided with a position / speed detector, and a feedback signal from these is fed back to the spindle motor control circuit 14 and the servo motor control circuits 15 and 16 as shown in FIG.
In addition, the feedback control of the current is performed, and the drive of the spindle motor Ms and the servo motors Mz and Mx is performed by driving the spindle amplifier 11 and the servo amplifiers 12 and 13 each composed of an inverter. . A power supply for power is supplied to the spindle amplifier 11 and the servo amplifiers 12 and 13 from a power supply circuit 10 that rectifies three-phase AC and supplies DC power.

The switch 9 is turned off by a command from the CNC 7 when an abnormality occurs in the machine or when an emergency stop command is input, cuts off the power supply to the brake device Br, and turns off the gravity by the brake device Br. The brake is applied to the axis to stop the movement of the gravity axis.

[0006]

When a power failure occurs, the single-phase AC power supplied to the rectifier circuit 6 is cut off, and the three-phase AC power supplied to the power supply 10 is also cut off. As a result, no power is supplied to the control power supply circuit 8, so that no power is also supplied to the spindle motor control circuit 14 and the servo motor control circuits 15 and 16. Amplifier 1
Since the switching elements 2 and 13 are all turned off and motive power is not supplied from the power supply circuit 10, the spindle motor Ms, the servo motors Mz and M
x is not supplied with power, and is in a free state. For this reason, the gravity axis under the action of gravity, that is, the spindle 1, the spindle motor Ms, and other spindle heads tend to fall. However, since no power is also supplied to the brake device Br due to the power failure, the brake is applied and the fall of the gravity axis is prevented.
The switch 9 is turned off by an emergency stop command, and is not turned off at the time of a power failure.

However, it takes several tens of milliseconds from when the power to the gravity axis servomotor Mz is cut off to when the brake device Br operates to activate the brake, during which the gravity axis may fall. By this drop, tool 2
In the case of a robot, there is a problem that the end effector or the work attached to the tip of the arm is damaged. Therefore, an object of the present invention is to prevent the gravity axis from dropping at the time of a power failure, and to prevent the above-mentioned problem from occurring.

[0008]

SUMMARY OF THE INVENTION According to the present invention, when a power failure is detected, a switch for supplying power to a brake device is turned off to brake the gravity axis and to drive the gravity axis. The movement command or speed command to the servomotor is set to “0” to perform deceleration control to stop the movement of the gravity axis. By turning off the switch that supplies power to the brake device immediately after a power failure,
The brake is activated immediately on the gravity axis. Also, when the movement command or the speed command to the servomotor for driving the gravity axis becomes "0", the servomotor is decelerated with a large torque, so that the fall of the gravity axis is prevented. become.

[0009]

FIG. 1 shows an embodiment in which the present invention is applied to a machine tool. Since they are almost the same as those in FIG. 4, the same reference numerals are given. The difference is that a power failure detection circuit is provided in the power supply circuit 10, and when the power failure is detected by the detection circuit, a detection signal S1 is output to the CNC 7, the spindle motor control circuit 14, and the servo motor control circuits 15 and 16. . The detection signal S1 is also output to a power regeneration control circuit in the power supply circuit 10.

FIG. 2 is a main block diagram of the power supply circuit 10, the amplifiers 14 to 16 and the control unit. The power supply circuit 10 includes a power failure detection circuit 10a that detects a power failure of the three-phase AC power supply. As shown in FIG. 3, the power failure detection circuit 10a rectifies a three-phase AC power supply with a bridge circuit of a diode D, detects a voltage divided by a resistor R, and compares the detected voltage with a power failure detection voltage Vs by a comparator 2.
When the detection voltage is lower than the power failure detection voltage Vs, the power failure detection signal S1 is output. Note that C in FIG.
Is a noise absorbing capacitor. The power failure detection circuit 1
0a, a detection signal S1 is sent to the power regeneration control circuit 10b in the power supply circuit 10,
7, spindle motor control circuit 14, servo motor control circuit 1
5 and 16 are output.

The power regeneration control circuit 10b that has received the power failure detection signal S1 negates the function of regenerating the electric power stored in the electrolytic capacitor (not shown) in the power supply circuit 10 into a three-phase power supply. That is, all the transistors Tr as switching elements for regenerating the three-phase power supply are turned off, and the regeneration is invalidated. The power regeneration function is to regenerate the power stored in the electrolytic capacitor on the output side to the three-phase power source having a high voltage, which is the input side of the power supply circuit 10, but the three-phase power source is regenerated due to a power failure. This power regeneration function is invalidated in order to prevent the power regeneration function from malfunctioning due to lack of a point.

Further, the CNC 7 receiving the power failure detection signal S1
Processes this signal as an emergency stop command,
, An emergency stop signal is output and the switch 9 is turned off. Further, the power failure detection signal S1 is input to the spindle motor control circuit 14, servo motor control circuits 15 and 16, and these control circuits 14 to 16
When 1 is input, the speed command or the movement command is set to “0”, ignoring the command from the CNC 7. At this time, power supply is also stopped to these control circuits 14 to 16 due to the power failure, but immediately after the power failure, power is supplied by the energy stored in the smoothing electrolytic capacitor in the rectifier circuit 6, and this energy is supplied. Control circuit 1 until it runs out
4 to 16 are supplied with power via the control power supply circuit 8. As a result, the control circuits 14 to 16 operate normally for a short time after the power failure (several 10 ms until the above-mentioned brake Br is applied).

The spindle amplifier 11 and the servo amplifier 1
Power supply circuit 1 immediately after power failure
The remaining power is supplied to the electrolytic capacitor for smoothing the rectified voltage within 0, and these amplifiers 11 to 13 operate until the power is exhausted.

A power failure detection signal S is sent to the spindle motor control circuit 14.
When 1 is input, the speed command is set to "0" and the speed loop is processed. The spindle 1 keeps rotating immediately after the power failure according to the current command. The actual speed is fed back from a speed detector (not shown) and input to the speed loop. As a result, in the speed loop, in order to set the speed of the spindle motor Ms to “0”, a drive current in the reverse direction is commanded to the spindle motor Ms to decelerate with a large torque and stop.

Similarly, servo motor control circuits 15 and 16
When the power failure detection signal S1 is input to the controller and the speed command is set to “0”, the torque command from the speed loop of the servo motor control circuits 15 and 16 to the time immediately before the power failure becomes the same as in the control of the spindle motor. A torque command is issued in the reverse direction, deceleration control is performed, and deceleration control is performed on the servo motors Mz and Mx.

When the power failure detection signal S1 is input,
When the servo motor control circuits 15 and 16 set the movement command to be “0”, the position deviation in the position loop in the servo motor control circuits 15 and 16 is such that the movement command is “0”. However, from the position and speed detectors (not shown) attached to the servo motors Mz and Mx,
Since the position feedback signal in the direction of rotation just before the power failure is fed back, the sign becomes the reverse sign immediately before the power failure, and a speed command in the reverse rotation direction is output from the position loop. Also, in the speed loop, the speed command in the reverse rotation direction and the speed feedback signal in the rotation direction immediately before the power failure, which is fed back from the position / speed detector,
As a result, a torque command in the reverse rotation direction is output, and the servo motors Mz and Mx are subjected to deceleration control with a large torque.

As described above, conventionally, when a power failure occurs, the apparatus is in a free state, and the gravity axis naturally falls until a brake is applied. However, in the present invention, since the spindle motor MS and the servo motors Mz and Mx are decelerated by the energy remaining in the electrolytic capacitor, the speeds of these motors Ms, Mz and Mx rapidly decrease immediately after the power failure and the rotation amount thereof is reduced. Is also reduced. Then, the servomotor Mz of the gravity axis is braked by the brake device Bz by turning off the switch 9 immediately after the power failure, so that the gravity axis falls slightly and is much less than the conventional one. Becomes If the power is already stopped at the time of the power failure, the control is continued at the current position (so as not to drop) until the power is turned off. As a result, it is possible to prevent a problem that the tool 2 and the workpiece W collide and break due to a drop of the gravity axis due to a power failure.

In the above embodiment, the power failure detection circuit 1
0a, when the power failure is detected, the spindle motor control circuit 14
Also, the power failure detection signal S1 is output to the servo motor control circuit 16 of the servo motor Mx for driving the table so that the speed command and the movement command are set to "0", but only to prevent the gravity axis from falling. In this case, the power failure detection signal S1 is not output to the spindle motor control circuit 14 or the servo motor control circuit 16 of the servo motor Mx, and the gravity axis servo motor Mz is not output.
May be output only to the servo motor control circuit 15, the CNC 7, and the power regeneration control circuit 10b.

[0019]

In the event of a power failure, the servomotor for driving the gravity axis is controlled to decelerate and brake is applied, so that the fall of the gravity axis is extremely small, and damage to tools and workpieces due to the fall of the gravity axis is reduced. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a machine tool to which the present invention is applied.

FIG. 2 is a main part block diagram of a power supply circuit, an amplifier, and a control unit in the embodiment.

FIG. 3 is a circuit diagram illustrating an example of a power failure detection circuit according to the first embodiment;

FIG. 4 is a block diagram of a machine tool before applying the present invention.

[Explanation of symbols]

 Reference Signs List 1 spindle 2 tool 3 feed screw mechanism 4 feed screw mechanism 6 rectifier circuit 7 numerical controller (CNC) Mz gravity axis servo motor Mx X axis servo motor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02P 3/04 H02P 3/04 B

Claims (1)

[Claims] 1. A fall prevention control device for a machine having a shaft which may move under the influence of gravity when a power failure occurs in a shaft, wherein a switch for supplying power to a brake device when a power failure is detected is provided. When the brake is applied to the axis by the brake device by turning off,
A power failure prevention control device that stops the movement of the shaft by performing a deceleration control by setting a movement command or a speed command to a servo motor that drives the shaft to “0”.