JPH11347874A - Stop control device for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stop control device for a machine tool capable of keeping stop condition without falling a vertically movable portion in power failure and miniaturizing the machine size for a limit switch position defining a movable range of the movable portion of a machine. SOLUTION: A machine tool provided with a movable portion driven and controlled by a servo motor and a brake 5 is provided with a resistor 11 connected with the brake 5 in series so as to supply minimum current or voltage, and current or voltage enough to excite the brake is supplied when the brake 5 is released.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a machine tool, and more particularly to a stop control for stopping a machine operation when an abnormality occurs.

[0002]

2. Description of the Related Art In general machine tools such as machining centers and lathes, movable parts such as a spindle head in a machining center and a tool post in a lathe are driven and controlled by a servomotor. FIG. 3 shows a configuration of a control device of a general machine tool. The servo motor 1 is generally an AC synchronous motor, and AC power of an arbitrary frequency and an arbitrary voltage corresponding to the speed is supplied by a servo amplifier 2. The servo amplifier 2 generally converts an AC power supply into an arbitrary frequency and an arbitrary voltage by a power converter. The servo amplifier 2 receives a position command or a speed command according to the machining program from the NC device 3 and controls the servo motor 1 so as to follow the command.

In the machine tool control device described above, the movable range of the machine movable portion is generally stored in the internal memory of the NC device 3 and exceeds the movable range due to a mistake in input of a machining program or an operator's operation mistake. When an abnormal position is instructed, the machine is prevented from being damaged by ignoring this instruction or generating an error signal. However, if the movable range data stored in the internal memory is incorrectly input, or if a hardware failure such as a failure of the servo amplifier 2 or the NC device 3 occurs, the movable portion exceeds the movable range. In such a case, the limit switch 4 operates the brake 5 to stop the machine. The brake 5 is released by applying a current to the servo motor 1.
Can be operated, and the servomotor 1 is braked by turning off the current to be in a braking state.

[0004]

In the machine tool control device described above, the servo amplifier 2 cannot supply power to the servomotor 1 when the AC power supply is interrupted, so that the movable part that moves in the vertical direction Begins to fall by gravity. At this time, the brake power supply 6 shown in FIG. 3 cannot supply the current due to the power failure, so that the brake 5 is in the braking state and the movable part stops. However, since the operation is slow, the falling amount is large, and as a result, The tool may be damaged or the work may be damaged due to the bite of the tool into the work being processed.

When the limit switch 4 detects that the mechanical movable portion has exceeded the movable range, the mechanical movable portion moves during a delay time from when the limit switch 4 operates to when the brake 5 exerts a braking force. Will continue. This moving amount is a so-called idle running distance, and the position where the movable part actually stops is a position apart from the installation position of the limit switch 4 by the sum of the idle running distance and the braking distance from the start of braking to the deceleration stop. There is a need to. For this reason, the machine movable range is generally designed with a sufficient margin with respect to the position where the limit switch 4 is installed, and as a result, there is a problem that the machine size increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to maintain a stopped state without dropping a vertically movable part when a power failure occurs, and to provide a mechanical movable part. It is an object of the present invention to provide a machine tool stop control device capable of reducing the machine size with respect to a limit switch position that defines the movable range of the machine tool.

[0007]

According to the present invention, there is provided a movable part which is driven and controlled by a servomotor, and a current or voltage is supplied by turning on an input brake release signal to be in a release state and the movable part is released. And a brake for stopping the moving operation of the movable part by turning off the brake release signal and cutting off the current or voltage by turning off the brake release signal. It is an object of the present invention to provide a brake system in series with said brake so as to supply the minimum current or voltage necessary to maintain said release state during the period when said brake is energized and released. And a release holding circuit having a resistor connected to the power supply, and the current or voltage is supplied when the brake is released. A brake release circuit having a timer relay for short-circuiting both ends of the resistor so as to supply a current or a voltage sufficient to excite the brake for a predetermined time after the brake is released. This is achieved by quickly bringing the movable portion into a braking state in response to a release signal. Further, abnormality detection means for turning off the brake release signal by using an output of a power failure detection circuit for detecting a stop of the power supply of the machine or an output of a limit switch for detecting that the movable portion has exceeded the movable range as an input. By providing it is more effectively achieved.

Alternatively, there is provided a resistor connected in series with the brake, and a brake operation sensor for detecting whether a brake pad of the brake is in a release position or a braking position, and the brake operation sensor detects the brake operation. During the period when the pad is detected to be in the braking position, a sufficient current or voltage is supplied to short-circuit both ends of the resistor to excite the brake, and the brake operation sensor releases the brake pad. The position sensing period is achieved by providing the brake with the minimum current or voltage required to maintain the released condition.

[0009]

In the machine tool stop control device according to the present invention, the delay time until the brake actually exerts the braking force after the current supplied to the brake is cut off can be reduced. Therefore, the movable part of the machine can be stopped immediately.

FIG. 1 shows a system configuration of an embodiment of a machine tool stop control device according to the present invention. In FIG. 1, reference numeral 7 denotes a power failure detection circuit which detects a power failure of an AC power supply at high speed and turns off conduction between two output signals. As a result, the current supplied to the brake 5 is cut off. The brake release holding circuit 8 is realized by a resistor 11 for limiting a current supplied to the brake 5, and supplies the brake 5 with a minimum current necessary to maintain the released state. By keeping the value of the supplied current small, the brake 5 transitions to the braking state very quickly after the power failure detection circuit interrupts the current. Can be stopped. The brake release circuit 9 is realized by a timer relay 10. By bypassing the resistor 11 only for a predetermined time (for example, about one second) after the start of energization of the brake, the brake release circuit 9 is sufficient to release the brake 5. Supply current.

The brake 5 is connected in series with a limit switch 4 which is turned off when the movable part of the machine moves beyond the movable range. When the power failure detection circuit interrupts the current when the power failure occurs, the vehicle can be shifted to the braking state very quickly.

FIG. 2 shows an alternative to the timer relay described above.
This is an embodiment in which a similar effect is realized by providing a sensor switch for detecting an operation state in the brake itself, and a cross-sectional structure showing a structural example of a brake and a sensor switch incorporated in a servomotor and a connection example of a resistor. FIG. The servo motor includes a stator core 12, a magnet 13, an encoder 14, and the like, and has a built-in brake for braking the shaft 15. The brake is composed of a coil 16, a fixed iron core 17, a movable iron core 18, a disk 19, a spring 20, and the like. When the coil 16 is not energized, the movable iron core 18 is moved rightward in FIG. At this time, the disk 19 is pressed so as to be sandwiched between the flange 21 and the movable iron core 18, thereby braking the shaft 15. The disk 19 is attached to the shaft 15 so as to be allowed to move slightly in the longitudinal direction of the shaft but not to rotate in the rotational direction. When the coil 16 is energized and excited, the movable iron core 18 is attracted to the fixed iron core 17 by magnetic force. At this time, the disk 19 is released from the above-described sandwiched state, so that the disk 19 is released.

The switch 22 is arranged so as to be turned off when the movable core 18 is at a position where the movable core 18 is attracted to the fixed core 17, that is, at a release position.
8 is a sensor switch for detecting the position of 8. When a voltage is applied between the terminal A and the terminal B when the brake is released, the switch 22 is turned on in the initial state. Therefore, the coil 16 is sufficiently excited. When the movable iron core 18 moves to the release position, the switch 22 is turned off, so that the current reduced by the resistor 11 is supplied to the coil 16 and the terminal A,
When the voltage supplied to the terminal B is cut off, it is possible to make a quick transition to the braking state.

[0014]

As described above, according to the present invention, the amount of the movable part in the vertical direction falling when a power failure occurs or the amount of the movable part moving in the horizontal direction or the like due to inertial force can be minimized. Damage and damage to the workpiece can be prevented. Further, when the limit switch for defining the movable range of the mechanical movable section operates, the movable section can be stopped at a small decomposing distance after the operation. for that reason,
Since the actual movable range can be reduced with respect to the limit switch position, the machine size can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment of a machine tool stop control device according to the present invention.

FIG. 2 is a sectional structural view showing a structure of a servomotor with a brake and a brake connection for realizing one embodiment of a stop control device for a machine tool according to the present invention.

FIG. 3 is a block diagram showing a system configuration of a conventional machine tool control device.

[Explanation of symbols]

 Reference Signs List 1 servo motor 2 servo amplifier 3 NC device 4 limit switch 5 brake 6 brake power supply 7 power failure detection circuit 8 brake release holding circuit 9 brake release circuit 10 timer relay 11 resistor 12 stator core 13 magnet 14 encoder 15 axis 16 coil 17 fixed iron core 18 Movable iron core 19 Disc 20 Spring 21 Flange 22 Switch

Claims (3)

[Claims] 1. A movable part driven and controlled by a servomotor, and a current or a voltage is supplied by turning on an input brake release signal to be in a release state to enable the movable part to move. When the brake release signal is turned off, the current or the voltage is cut off, a braking state is established, and a brake for stopping the moving operation of the movable unit is provided. Releasing the brake and a release holding circuit having a resistor connected in series with the brake so as to supply a minimum current or voltage necessary to hold the release state during a period in which the brake is released. For a predetermined time after the supply of the current or the voltage is started, a sufficient current for exciting the brake is provided. A brake release circuit having a timer relay for short-circuiting both ends of the resistor so as to supply a voltage, and when the machine tool is abnormal, the movable portion is quickly brought into a braking state in response to the brake release signal. A machine tool stop control device characterized in that: 2. An abnormality in which the brake release signal is turned off by receiving an output of a power failure detection circuit for detecting a stop of a power supply of a machine or an output of a limit switch for detecting that the movable portion has exceeded a movable range. The stop control device for a machine tool according to claim 1, further comprising a detection unit. 3. A movable portion driven and controlled by a servomotor, and a current or a voltage is supplied by turning on an input brake release signal to release the movable portion, thereby enabling the movable portion to move. A machine tool comprising: a brake that cuts off the current or voltage when the brake release signal is turned off to be in a braking state to stop the moving operation of the movable unit; and a resistor connected in series with the brake. And a brake operation sensor for detecting whether a brake pad of the brake is at a release position or a braking position. A period during which the brake operation sensor detects that the brake pad is at the braking position is provided. Providing a current or voltage sufficient to excite the brake by shorting across the resistor, During the period when the brake pad is in the release position by the rake operation sensor, the resistor supplies the brake with the minimum current or voltage necessary to maintain the brake in the released state. A machine tool stop control device.