JP5125405B2 - Stop detection device, stop detection method, and safety system - Google Patents

Description

  The present invention relates to a stop detection device, a stop detection method for detecting the stop of a motor as a drive source of various machines such as machine tools and industrial robots, and a production site where various machines and workers coexist using the same. The present invention relates to a safety system for ensuring safety.

  Conventionally, various safety systems have been proposed in order to ensure safety in production sites where workers and various machines such as machine tools and industrial robots coexist. For example, the stop of a three-phase machine (three-phase motor), which is a drive source for various machines such as machine tools and industrial robots, is monitored and until the stop is confirmed, the work area where the various machines are installed is monitored. It has been proposed that the door of the doorway cannot be opened (see, for example, Patent Document 1).

In Patent Document 1, when a voltage generated from a three-phase machine serving as a driving source falls below a threshold voltage, it is determined that the three-phase machine has stopped.
Japanese Patent No. 3344931

  Generally, the threshold voltage is set by an analog volume as described above. However, the analog volume has a relatively large variation in parts, and therefore, the adjustment of the threshold voltage varies, and the accuracy of motor stop detection is improved. There is a problem of being bad.

  Further, since the setting angle of the analog volume depends on the sense of the setter, an error is likely to occur, and there is a problem similar to the above.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a stop detection device, a stop detection method, and a safety system with improved accuracy of motor stop detection.

A stop detection device according to claim 1 of the present invention is a stop detection device that detects stop of a motor, and detects a counter electromotive force detection unit that detects a counter electromotive force of the motor, and detection of the counter electromotive force detection unit. value, when the set time from the time when equal to or less than a fixed threshold has elapsed, said the determination unit motor is stopped, the set time with and a setting unit that sets as a digital value, the motor A selection unit that selects whether to determine whether to stop the operation in the first determination mode or the second determination mode. The determination unit sets the fixed threshold as a first threshold, and the selection unit According to the selection, in the first determination mode, the motor is stopped when the determination time has elapsed since the detection value of the back electromotive force detection unit becomes equal to or less than the first threshold. Determining, the second determination mode It determines that the detection value of the counter electromotive force detecting portion, when it becomes less than the second threshold value fixed, the motor is stopped.

  According to the stop detection device of the present invention, the threshold value to be compared with the detection value of the back electromotive force detection unit is fixed, and there is no need to set the threshold value using an analog volume as in the conventional example. The threshold adjustment does not vary depending on the feeling of the setter or the setting person, and the setting time for adjusting the timing of motor stop determination is set digitally, which improves the reproducibility of the setting and The accuracy of stop detection can be increased.

  The second threshold is preferably a value different from the first threshold, but may be the same value.

Furthermore, according to the stop detection device of the present invention , the user can determine the stop of the motor by selecting one of the first and second determination modes having different determination criteria according to the application. Therefore, it can cope with a wider range of applications. Further, when the user does not need a specific timing setting for the determination, the user can use it as it is without going through the adjustment process by selecting the second determination mode.

A stop detection device according to a second aspect of the present invention is a stop detection device that detects stop of a motor, wherein the counter electromotive force detection unit detects the counter electromotive force of the motor, and the detection of the counter electromotive force detection unit. When the set time has elapsed since the value became equal to or less than the fixed first threshold value, or when the detected value became equal to or less than the fixed second threshold value that is smaller than the first threshold value. A determination unit that determines that the motor has stopped, and a setting unit that sets the set time as a digital value.

  The second threshold value smaller than the first threshold value is preferably a small value for ensuring safety, and may be a value corresponding to a state in which the motor is almost completely stopped.

  According to the stop detection device of the present invention, the first and second threshold values to be compared with the detection value of the back electromotive force detection unit are fixed, and it is necessary to set the threshold value using an analog volume as in the conventional example. Therefore, the threshold adjustment does not vary, and the setting time for adjusting the motor stop determination timing is set digitally, improving the reproducibility of the setting and the accuracy of motor stop detection. Can be increased.

  Further, when the set time elapses when the detection value of the back electromotive force detection unit becomes equal to or less than the first threshold value by the selection of the set time by the user, the second threshold value where the detected value is smaller than the first threshold value It can be set before (early) or after (slow) the time point when it becomes below, and if it is set before, the detection value of the back electromotive force detection unit falls below the first threshold and the set time elapses. The time is an effective motor stop determination, and if set later, the time when the detected value is equal to or less than the second threshold is an effective motor stop determination.

  Therefore, the user can select the timing for determining that the motor is stopped according to the application. For example, in the case where safety cannot be ensured unless the motor is stopped almost completely, the counter electromotive force detection is performed. When the detected value of the part becomes equal to or smaller than a fixed second threshold value smaller than the first threshold value, it can be determined that the motor is stopped and safety can be ensured, for example, the motor does not stop almost completely. However, when the machine driven by the motor via the speed reduction mechanism stops and safety can be ensured, the detection value of the back electromotive force detection unit is before the second threshold value or less, Eliminate unnecessary waiting time until the motor stops almost completely while ensuring safety by determining that the motor has stopped when the set time has elapsed since the time when it became below the first threshold. Can It is possible to improve the productivity.

The stop detection device according to claim 3 of the present invention is the stop detection device according to claim 2, wherein the selection of whether to determine whether to stop the motor is performed in one of the first and second determination modes. The determination unit is configured to perform the setting from the time point when the detection value of the back electromotive force detection unit is equal to or lower than the first threshold value in the first determination mode according to the selection by the selection unit. When the time elapses or when the detection value becomes equal to or smaller than the second threshold value that is smaller than the first threshold value, it is determined that the motor has stopped, and in the second determination mode, , the detected value, when it becomes less than the third threshold value fixed, it determined that the motor has stopped.

  The third threshold value is preferably different from the first and second threshold values, but may be the same value.

According to the stop detection device according to claim 3 of the present invention , the user selects one of the first and second determination modes having different determination criteria according to the application, and determines the motor stop. It will be able to handle a wider range of applications. Further, when the user does not need a specific timing setting for the determination, the user can use it as it is without going through the adjustment process by selecting the second determination mode.

The stop detection device according to claim 4 of the present invention is the stop detection device according to claim 2 or 3, further comprising an output unit that outputs a determination result of the determination unit, wherein the output unit has the detection value as the first value. A determination result of stopping the motor when the set time has elapsed from a time when the threshold value is 1 or less, a determination result of stopping the motor when the detection value is less than or equal to the second threshold value, detection value and the determination result of the stop motor when it becomes less than the second threshold value, you output identifiably.

  For example, when the set value has elapsed from the time when the detected value is equal to or less than the first threshold, the determination result of stopping the motor and the detected value is equal to or less than the second threshold. The determination result of the stop of the motor at the time may be output individually from each corresponding output unit, or output from a common output unit and which determination result is output For example, display output may be performed.

  In machines driven by motors, such as grinders and milling machines, inertial rotation when the motor stops when the service period has elapsed and the grindstones and tools that are loads have been ground and become lighter and have reached the end of their lives. This shortens the time required for the counter electromotive force, and accelerates the decrease in the back electromotive force.

According to the stop detection device according to claim 4 of the present invention, at the initial stage of use of the grinding machine or the like, the output unit is configured so that the set time elapses from the time when the detected value becomes equal to or lower than the first threshold value. The output of the stop determination result is that the detection value becomes equal to or lower than the second threshold before the set time elapses because the back electromotive force decreases more quickly as the usage period elapses. As a result, it is possible to grasp the service life of a grindstone, which is a load of a grinder, for example.

A stop detection device according to a fifth aspect of the present invention is the stop detection device according to any one of the first to fourth aspects, wherein the stop detection device is interposed between a terminal of the motor and a power source to supply power to the motor. A contact input unit to which a contact input corresponding to a contact state of a switch that performs closing and closing is provided, and the determination unit is in a state in which the contact of the switch is turned off based on the contact state from the contact input unit This is a precondition for determining that the motor has stopped.

According to the stop detection device according to claim 5 of the present invention, on the precondition that the contact of the switch for turning on and off the power to the motor is turned off, that is, the power is cut off. As described above, the stop of the motor can be determined based on the back electromotive force.

Stop detection device according to claim 6 of the present invention, the judgment result that the motor by the determining unit is stopped, Ru used to unlock the door switch of the electromagnetic lock type.

According to the stop detection device according to the sixth aspect of the present invention, since the door switch is unlocked by detecting the stop of the motor, for example, the door of the work area where the machine driven by the motor is installed is provided. By providing the door switch, the door switch is not unlocked until the motor stops and the machine stops, and the operator cannot open the door and enter the work area, ensuring safety. Is done.

In a stop detection device according to a seventh aspect of the present invention, the setting unit is a digital setting switch.

According to the stop detection device of the seventh aspect of the present invention , for example, the setting time can be digitally set by a digital setting switch such as a rotary switch, and the timing of the motor stop determination can be adjusted.

A stop detection method according to an eighth aspect of the present invention is a stop detection method for detecting stop of a motor, wherein a setting step for setting a set time as a digital value in advance and detecting a back electromotive force of the motor are detected. A determination step for determining that the motor has stopped when the set time has elapsed from a time when the value becomes equal to or less than a fixed threshold, and a first determination and a second determination for determining whether the motor has stopped A selection step of selecting one of the determination modes of the mode, wherein the fixed threshold is the first threshold in the determination step, and the reverse is performed in the first determination mode according to the selection in the selection step. When the set time has elapsed since the detection value of the electromotive force detection unit becomes equal to or less than the first threshold, it is determined that the motor has stopped, and in the second determination mode, the detection is performed. It determines that the value is, when it is below the fixed second threshold value, the motor is stopped.

  According to the stop detection method of the present invention, the threshold value to be compared with the detection value of the back electromotive force detection unit is fixed, and there is no need to set the threshold value using an analog volume as in the conventional example. The threshold adjustment does not vary depending on the feeling of the setter or the setting person, and the setting time for adjusting the timing of motor stop determination is set digitally, which improves the reproducibility of the setting and The accuracy of stop detection can be increased.

According to the stop detection method according to claim 9 of the present invention , the user selects one of the determination modes of the first and second determination modes having different determination criteria according to the application, and stops the motor. Therefore, a wider range of applications can be handled. Further, when the user does not need a specific timing setting for the determination, the user can use it as it is without going through the adjustment process by selecting the second determination mode.

A stop detection method according to claim 9 of the present invention is a stop detection method for detecting stop of a motor, wherein a setting step for setting a set time as a digital value in advance and detecting a back electromotive force of the motor are detected. When the set time has elapsed since the value became equal to or smaller than the fixed first threshold value, or when the detected value became equal to or smaller than the fixed second threshold value that is smaller than the first threshold value. And a determination step for determining that the motor has stopped.

According to the detection stopping method according to claim 9 of the present invention , the first and second threshold values to be compared with the detection value of the back electromotive force detection unit are fixed, and the threshold value is set using an analog volume as in the conventional example. Since there is no need to set the threshold value, the threshold adjustment does not vary, and the setting time for adjusting the motor stop determination timing is set digitally. The accuracy of stop detection can be improved.

  Furthermore, it is determined that the motor is stopped when the detection value of the back electromotive force detection unit becomes equal to or lower than the first threshold and the setting time has elapsed by the selection of the setting time by the user, or the detection value is The user can select whether or not to determine that the motor is stopped when the threshold value is less than or equal to the threshold value of 2.

  Therefore, the user can select the timing for determining that the motor is stopped according to the application. For example, in the case where safety cannot be ensured unless the motor is stopped almost completely, the counter electromotive force detection is performed. When the detected value of the part becomes equal to or smaller than a fixed second threshold value smaller than the first threshold value, it can be determined that the motor is stopped and safety can be ensured, for example, the motor does not stop almost completely. However, when the machine driven by the motor via the speed reduction mechanism stops and safety can be ensured, the detection value of the back electromotive force detection unit is before the second threshold value or less, Eliminate unnecessary waiting time until the motor stops almost completely while ensuring safety by determining that the motor has stopped when the set time has elapsed since the time when it became below the first threshold. Can It is possible to improve productivity.

The stop detection method according to claim 10 of the present invention is the stop detection method according to claim 9, wherein the selection step selects one of the determination modes of the first and second determination modes for determining the stop of the motor. In the determination step, in the first determination mode, the determination time from the time point when the detection value of the back electromotive force detection unit becomes equal to or less than the first threshold according to the selection in the selection step. Or when the detected value falls below the second threshold value which is smaller than the first threshold value, it is determined that the motor has stopped, and in the second determination mode, When the detected value is equal to or less than a fixed third threshold value, it is determined that the motor has stopped.

According to the stop detection method according to claim 10 of the present invention , the user can determine whether the motor has stopped by selecting one of the first and second determination modes having different determination criteria according to the application. Therefore, it will be able to support a wider range of applications. Further, when the user does not need a specific timing setting for the determination, the user can use it as it is without going through the adjustment process by selecting the second determination mode.

A safety system according to an eleventh aspect of the present invention is driven by a motor, a switch for turning on and off the power to the motor, a stop detection device for detecting a stop of the motor and providing a detection output, and the motor. An electromagnetic lock type door switch provided on a door for entering and exiting a work area where the machine to be installed is installed, wherein the stop detection device detects a back electromotive force of the motor On the basis of the back electromotive force detection unit, the contact input unit to which a contact input corresponding to the contact state of the switch is applied, and the contact state from the contact input unit, the contact of the switch is in an off state. And a determination unit that determines that the motor has stopped when a set time has elapsed since the detection value of the back electromotive force detection unit is equal to or less than a fixed threshold, and the set time is a digital value. And a setting unit for setting a value, the judgment result that the motor by the determining unit is stopped, with use in unlocking of the electromagnetic lock type door switch, the stop detection device, the determination of stop of the motor Is selected in the determination mode of the first and second determination modes, and the determination unit sets the fixed threshold as the first threshold, and according to the selection by the selection unit In the first determination mode, the set time from the time when the contact of the switch is turned off and the detection value of the back electromotive force detection unit becomes equal to or less than the first threshold value. When the time has elapsed, it is determined that the motor has stopped. In the second determination mode, the contact of the switch is turned off, and the detection value of the back electromotive force detection unit is fixed. When it became below the second threshold In determines that the motor has stopped.

  The machine refers to various machines such as a machine tool such as a grinding machine, a printing machine, a transport machine, a robot, and a construction machine.

  The work area refers to an area where a machine is installed and work is performed.

  According to the safety system of the present invention, since the stop of the motor that drives the machine is detected by the stop detection device and the door switch is unlocked, until the motor stops and the machine stops, the door switch The lock is not released, and the worker cannot open the door and enter the work area where the machine is installed, so that the safety of the worker is ensured.

  In addition, the stop detection device does not need to set a threshold for determining motor stop using an analog volume as in the conventional example, so that the adjustment of the threshold varies depending on the variation of parts and the sense of the setter. In addition, since the set time for determining the stop of the motor is digitally set, the reproducibility of the setting is improved and the accuracy of detecting the stop of the motor can be improved.

According to the safety system of claim 11 of the present invention , the user selects one of the first and second determination modes having different determination criteria according to the application, and stops the motor. Since it can be determined, it can cope with a wider range of applications. Further, when the user does not need a specific timing setting for the determination, the user can use it as it is without going through the adjustment process by selecting the second determination mode.

A safety system according to a twelfth aspect of the present invention is driven by a motor, a switch for turning on / off the power to the motor, a stop detection device for detecting a stop of the motor and providing a detection output, and the motor. An electromagnetic lock type door switch provided on a door for entering and exiting a work area where the machine to be installed is installed, wherein the stop detection device detects a back electromotive force of the motor On the basis of the back electromotive force detection unit, the contact input unit to which a contact input corresponding to the contact state of the switch is applied, and the contact state from the contact input unit, the contact of the switch is in an off state. And when a set time has elapsed since the detection value of the back electromotive force detection unit is equal to or less than a fixed first threshold value, or the contact of the switch is turned off, And A determination unit that determines that the motor has stopped when the detected value is equal to or less than a fixed second threshold value that is smaller than the first threshold value; and a setting unit that sets the set time as a digital value; The determination result that the motor is stopped by the determination unit is used for unlocking the electromagnetic lock type door switch.

  According to the safety system of the present invention, the stop of the motor that drives the machine is detected by the stop detection device, and the door switch at the entrance / exit of the work area is unlocked, so that the motor stops and the machine stops. The door switch is not unlocked, and the worker cannot open the door and enter the work area where the machine is installed, thus ensuring the safety of the worker.

  In addition, the stop detection device does not need to set a threshold for determining motor stop using an analog volume as in the conventional example, so that the adjustment of the threshold varies depending on the variation of parts and the sense of the setter. In addition, since the set time for determining the stop of the motor is digitally set, the reproducibility of the setting is improved and the accuracy of detecting the stop of the motor can be improved.

  Furthermore, it is determined that the motor is stopped when the detection value of the back electromotive force detection unit becomes equal to or lower than the first threshold and the setting time has elapsed by the selection of the setting time by the user, or the detection value is The user can select whether or not to determine that the motor is stopped when the threshold value is less than or equal to the threshold value of 2.

  Therefore, the user can select the timing for determining that the motor is stopped according to the application. For example, in the case where safety cannot be ensured unless the motor is stopped almost completely, the counter electromotive force detection is performed. When the detected value of the part becomes equal to or smaller than a fixed second threshold value smaller than the first threshold value, it can be determined that the motor is stopped and safety can be ensured, for example, the motor does not stop almost completely. However, when the machine driven by the motor via the speed reduction mechanism stops and safety can be ensured, the detection value of the back electromotive force detection unit is before the second threshold value or less, Eliminate unnecessary waiting time until the motor stops almost completely while ensuring safety by determining that the motor has stopped when the set time has elapsed since the time when it became below the first threshold. Can It is possible to improve the productivity.

A safety system according to a thirteenth aspect of the present invention is the safety system according to the twelfth aspect, wherein the stop detection device determines whether to stop the motor in any one of the first and second determination modes. A selection unit for selecting whether to perform, in accordance with the selection by the selection unit, in the first determination mode, the contact of the switch is turned off and the back electromotive force is detected. When the set time has elapsed since the detection value of the power detection unit is equal to or less than the first threshold, or the contact of the switch is turned off, and the detection value is It is determined that the motor has stopped when the second threshold value is smaller than the first threshold value, which is smaller than the first threshold value, and in the second determination mode, the contact of the switch is turned off, And the detected value is a fixed third value. When it is below the threshold, it is determined that the motor has stopped.

According to the safety system of the thirteenth aspect of the present invention , the user can determine whether to stop the motor by selecting one of the first and second determination modes having different determination criteria according to the application. Therefore, it will be able to support a wider range of applications. Further, when the user does not need a specific timing setting for the determination, the user can use it as it is without going through the adjustment process by selecting the second determination mode.

  According to the present invention, the threshold value to be compared with the detection value of the back electromotive force detection unit is fixed, and it is not necessary to set the threshold value using an analog volume as in the conventional example. The threshold adjustment does not vary depending on the sensation, and the set time for adjusting the motor stop determination timing is set digitally, improving the reproducibility of the setting and the accuracy of detecting the motor stop Can be increased.

  According to the present invention, when the detection value of the electromotive force detection unit becomes equal to or smaller than the fixed second threshold value smaller than the first threshold value by the user setting the set time according to the application. On the other hand, while it can be determined that the motor is stopped and safety can be ensured, the set time from the time when the detection value of the back electromotive force detection unit becomes equal to or less than the first threshold before the detection value becomes equal to or less than the second threshold. By determining that the motor has stopped when the time has elapsed, unnecessary standby time can be eliminated while ensuring safety, and productivity can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a safety system according to an embodiment of the present invention.

  This safety system detects a three-phase AC power source 1, a three-phase motor 2 connected to the power source 1 to drive a machine tool such as a grinding machine (not shown), and the stop of the motor 2 as described below. And a stop detection unit 3 as a stop detection device according to the present invention that provides detection output, and a stop detection unit 3 installed at the door of the work area where the motor 2 and the machine tool are arranged as described later. On and off of the magnetic contactor 7 for turning on and off the power based on the output of the electromagnetic lock type door switch 5 given as an unlock signal and the outputs of the door switch 5 and the emergency stop switch 6 And a safety unit 18 as a safety control device to be controlled.

  The main contact (NO contact) of the magnet contactor 7 as a switch is connected between the winding terminals U, V, W of the motor 2 and the terminals U, V, W of the power supply 1.

  As shown in FIG. 2, the work area where the motor 2 and the machine tool (not shown) are installed is surrounded by a safety fence, and this safety fence has a door serving as an entrance to the work area. 4 is installed, and the above-described electromagnetic lock type door switch 5 is attached to the door 4. As for this door switch 5, for example, the switch body is attached to the fixed frame side of the door 4, and the operation key inserted into and removed from the opening of the switch body is attached to the movable part side of the door 4 to close the door 4. When the operation key is inserted into the opening of the switch body, it is mechanically locked and prohibits the door 4 from being opened. Further, when the detection output that detects the stop of the motor 2 is given from the stop detection unit 3 to the door switch 5 as a lock release signal, the lock is released and the door 4 can be opened by operating the solenoid. Become.

  The door switch 5 provides a safety-side safety input that allows the machine tool to be driven when the door 4 is closed, while the door 4 is open, when the door 4 is closed. Then, the safety input of the dangerous side which prohibits the drive of a machine tool is given.

  The emergency stop switch 6 shown in FIG. 1 gives a safety input to the safety unit 18 on the dangerous side for prohibiting the driving of the machine tool by the operation of an emergency worker or the like. Gives a safety-side safety input that allows driving.

  The safety unit 18 of this embodiment is equipped with a microcomputer, and controls on / off of the main contact of the magnetic contactor 7 according to a program based on safety inputs from the emergency stop switch 6 and the door switch 5. On the condition that the safety inputs from the emergency stop switch 6 and the door switch 5 are both safe, the main contact of the magnetic contactor 7 is turned on to supply power to the motor 2, while the emergency stop switch 6 or door When any one of the safety inputs from the switch 5 is on the dangerous side, the main contact of the magnet contactor 7 is turned off to cut off the power to the motor 2.

  As another embodiment, the safety unit may control the on / off of the magnetic contactor 7 based on the safety input from the emergency stop switch 6 and the door switch 5 by sequence control without mounting a microcomputer. .

  The stop detection unit 3 of this embodiment detects the stop of the motor 2 based on the back electromotive force (BEMF) of the motor 2 and the contact state of the magnet contactor 7.

  As shown in FIG. 3, the stop detection unit 3 includes first and second counter electromotive force detectors 11 and 12 and detects three-phase interphase voltages as counter electromotive forces. The stop detection unit 3 also includes a contact input unit 13 to which an auxiliary contact (NC contact) for monitoring indicating the contact state of the magnet contactor 7 is input and two CPUs 8 and 9 for duplicating the processing. .

  Each of the CPUs 8 and 9 having a function as a determination unit for determining whether or not the motor 2 is stopped is in a state where the main contact (NO contact) of the magnet contactor 7 is turned off, that is, the auxiliary contact of the magnet contactor 7. The motor 2 is stopped when the (NC contact) is on and both detection values of the first and second counter electromotive force detection units 11 and 12 satisfy a determination criterion described later. Judgment is made respectively.

  When both the CPUs 8 and 9 determine that the motor 2 has stopped, it is finally determined that the motor 2 has stopped, and the stop detection output of the motor 2 is given to the door switch 5 as an unlock signal. It is.

  FIG. 4 is a block diagram of the stop detection unit 3 of this embodiment, and parts corresponding to those in FIG.

  The stop detection unit 3 is supplied with contact inputs of the first and second counter electromotive force detectors 11 and 12 for detecting the counter electromotive force of the motor 2 and auxiliary contacts corresponding to the contact state of the magnet contactor 7. The above-described contact input unit 13, the user setting unit 10 for setting the setting time and the like by the user and the selection of the determination mode described later, the outputs and contacts of the first and second back electromotive force detection units 11 and 12 Based on the settings of the input unit 13 and the user, a stop determination unit 14 that determines whether or not the motor 2 is stopped, and when it is determined that the motor 2 is stopped, the stop detection output is output to the door described above. The switch 5 includes an output unit 15 that outputs a lock release signal.

  In this embodiment, the determination of the stop of the motor 2 based on the back electromotive force can be performed using two determination modes having different determination criteria, and the user selects which determination mode to use as the selection unit. It can be selected from the user setting unit 10. Hereinafter, each determination criterion in each determination mode will be described. Note that the contact input from the magnet contactor 7 will be described assuming that the main contact is in an off state, that is, a state in which the power supply is shut off.

  FIG. 5 is a diagram for explaining motor stop determination based on the first determination criterion in the first determination mode. FIG. 5 (a) shows the change in the back electromotive force (BEMF). , (C) show stop determination outputs, respectively.

  According to this first criterion, the main contact of the magnet contactor 7 is turned off, the supply of power to the motor 2 is cut off, the back electromotive force shown in FIG. It is determined that the motor 2 has stopped when the set time T by the user shown in FIG. 5B has elapsed (t2) from the time t1 when L1 or less, or a high-level stop determination output is given, or When the back electromotive force decreases as shown in FIG. 6A and becomes equal to or smaller than the fixed second threshold L2 smaller than the first threshold L1, as shown in FIG. It is determined that the motor 2 has stopped and gives a high level stop determination output.

  In the example of the user setting time T shown in FIG. 5, the time t2 when the user setting time T elapses from the time t1 when the back electromotive force decreases and becomes equal to or less than the first threshold L1 is the second threshold. Since it is earlier than the time point t3 when it becomes less than or equal to L2, the determination output in FIG. 5B becomes an effective motor stop determination output. Further, when the set time T by the user is lengthened and the time t2 when the set time T elapses is later than the time t3 when the back electromotive force becomes equal to or less than the second threshold L2, the determination output of FIG. This is an effective motor stop determination output.

  FIG. 6 is a diagram for explaining motor stop determination based on the second determination criterion in the second determination mode. FIG. 6A shows the change in the back electromotive force (BEMF) and FIG. Indicates stop determination outputs.

  This second determination criterion corresponds to the determination of FIG. 5C described above, and as shown in FIG. 5A, the back electromotive force is reduced to be equal to or lower than the threshold value L as the third threshold value. When this happens (t4), it is determined that the motor 2 has stopped as shown in FIG. 4B, and a high-level stop determination output is given.

  According to the second determination criterion, by setting a small threshold L, it is determined that the motor 2 is stopped when the back electromotive force is reduced below the small threshold L. For example, a grinding machine, a milling machine, etc. In the application that drives the motor 2, when the rotation of the motor 2 is almost completely stopped and the grinding machine or the like is almost completely stopped, it is determined that the motor 2 is stopped, and sufficient safety can be secured. Become.

  When the user does not need to use the first determination criterion and selects the second determination criterion, the user can use the second determination criterion without performing the setting operation for the set time T as in the first determination criterion. it can.

  On the other hand, depending on the application, there is a case where the power of the motor is transmitted to the machine tool via a reduction mechanism such as a gear. In such a case, the above-described operation can be performed without waiting until the rotation of the motor stops substantially completely. The machine tool is almost stopped and is in a safe state. Therefore, in such a case, if the stop of the motor is detected according to the second determination criterion shown in FIG. 6, an unnecessary waiting time is generated until the motor is stopped, and the productivity is lowered.

  Therefore, in such an application, it is preferable to use the first determination criterion, and the user may set the set time T described above so that unnecessary waiting time is eliminated while ensuring safety. This setting is performed, for example, in units of seconds by a digital setting switch of the user setting unit 10 in FIG. 4 described above, for example, a rotary dip switch, an up key, or a down key.

  In a machine driven by the motor 2, such as a grinding machine, when the load such as a grindstone to be rotated is ground and lightens as the service period elapses, the motor after the power supply 1 is shut off The inertial rotation time of 2 is shortened, and the back electromotive force is rapidly lowered.

  When the above-described first determination criterion of FIG. 5 is used, the timing of the stop determination in FIGS. 5B and 5C may be switched due to the rapid decrease in the back electromotive force.

  FIG. 7 shows the motor stop determination in such a case. FIG. 7A shows the change in the back electromotive force (BEMF), and FIGS. 7B and 7C show the stop determination output. Yes.

  In the initial use of a grinder or the like, when the power source 1 of the motor 2 is turned off, the back electromotive force gradually decreases as shown by the solid line in FIG. Compared with the time t5 when the threshold L2 or less is reached, the time t6 when the set time T by the user elapses from the time when the back electromotive force becomes equal to or less than the first threshold L1, as shown in FIG. Thus, it becomes an effective motor stop determination output.

  On the other hand, when the load such as a grindstone to be rotated becomes light with the passage of the service period and nears the end of its service life, as shown by the phantom line in FIG. Becomes shorter and the back electromotive force rapidly decreases.

  At this time, compared with the time t6 when the set time T by the user elapses from the time when the back electromotive force becomes equal to or less than the first threshold L1, the back electromotive force is the second The time point t7 when the value becomes equal to or less than the threshold value L2 becomes earlier, and an effective motor stop determination output is obtained.

  As described above, with the passage of the use period, the motor stop determination at the beginning of the set time T shown in FIG. 5B is less than the second threshold L2 shown in FIG. It will be replaced with the stop determination of the motor due to lowering, and therefore it is possible to identify which stop determination output is, for example, to grasp the life of the load such as a grindstone of a grinder it can.

  Next, the operation of this embodiment will be described based on the flowcharts of FIGS. FIG. 8 shows the entire stop determination process, and FIG. 9 shows the stop determination process based on the back electromotive force as a part thereof.

  As shown in FIG. 8, in the motor stop determination process, it is determined that the motor is stopped by the back electromotive force, and the input of the auxiliary contact (NC contact) is the OFF state of the main contact (NO contact) of the magnet contactor 7 (Step n1), it is determined that the motor is stopped by the back electromotive force, and the contact input corresponds to the OFF state of the main contact of the magnet contactor 7, the final Then, it is determined that the motor has stopped, and the motor stop detection output is output to the door switch 5 described above as a lock release signal, and the process ends (step n2).

  In the motor stop determination based on the counter electromotive force, as shown in FIG. 9, it is determined which one of the first determination criterion and the second determination criterion is selected (step n1-1). When the determination criterion is selected, it is determined whether or not the back electromotive force is equal to or less than the first threshold value L1 (step n1-3), and when it is equal to or less than the first threshold value L1, it is set by the user. It is determined whether or not the set time T has elapsed (step n1-4). When the set time T has elapsed, it is determined that the motor has stopped (step n1-6) and the process ends.

  In step n1-4, when the set time T has not elapsed, it is determined whether or not the back electromotive force is less than or equal to the second threshold L2 (step n1-5), and is less than or equal to the second threshold L2. If it is detected, the process proceeds to step n1-6 to determine that the motor has stopped. On the other hand, when it is not less than or equal to the second threshold L2, the process returns to step n1-4.

  On the other hand, when the second determination criterion is selected in step n1-1, it is determined whether or not the back electromotive force is less than or equal to the threshold value L (step n1-2). In Step n1-6, it is determined that the motor has stopped.

  FIGS. 10 and 11 respectively show examples of time charts when the first determination criterion is adopted. FIG. 10 shows the time from when the back electromotive force (BEMF) becomes equal to or lower than the first threshold L1. FIG. 11 shows the case where the back electromotive force (BEMF) is less than the second threshold value L2 when the first threshold value L2 or less is earlier than the time set by the user elapses. Each of the cases where the set time T by the user elapses from the time when the threshold value L1 becomes equal to or less than the threshold L1 is shown.

  In each figure, (a) is the change in the back electromotive force (BEMF), (b) is the main contact (NO contact) of the magnet contactor 7, (c) the auxiliary contact (NC contact) of the magnet contactor 7, (d) is Each of the stop determination outputs is shown.

  As shown in FIGS. 10B and 10C, when the main contact of the magnet contactor 7 is turned off and the auxiliary contact is turned on to cut off the power to the motor, as shown in FIG. When the counter electromotive force decreases and becomes equal to or less than the second threshold L2 earlier than the time when the set time T by the user has elapsed since the time when the counter electromotive force decreases to the first threshold L1 or less, Then, it is determined that the motor has stopped, and an ON motor stop determination output is given.

  Further, as shown in FIGS. 11B and 11C, when the main contact of the magnet contactor 7 is turned off and the auxiliary contact is turned on to cut off the power to the motor, it is shown in FIG. 11A. Thus, when the set time T by the user elapses from when the counter electromotive force decreases and becomes equal to or lower than the first threshold value L1 earlier than the second threshold value L2 or less, as shown in FIG. In addition, it is determined that the motor has stopped, and an ON motor stop determination output is provided.

  As described above, since the user can select either the first determination criterion or the second determination criterion according to the application, the user can deal with a wider range of applications.

  Note that the second threshold value L2 in the first determination criterion may be the same as or different from the threshold value L in the second determination criterion.

  In the above-described embodiment, the threshold values L, L1, and L2 are fixed, but the user may be able to make variable settings, preferably digital settings.

  In this case, the back electromotive force is as small as several tens of mV to several hundred mV, and in a normal 5V system circuit, for example, 10 mV is 0.2% with respect to 5V. It is difficult to determine the magnitude of the back electromotive force by changing the threshold value. For this reason, the threshold value is fixed, and the amplification factor of the operational amplifier that amplifies the counter electromotive force may be varied to substantially set the threshold value variably.

  In the above-described embodiment, the user can select the first determination criterion and the second determination criterion. However, as another embodiment of the present invention, only the first determination criterion may be configured.

  Further, according to the first criterion, it is determined that the motor 2 has stopped when the time set by the user has elapsed since the time when the back electromotive force has decreased to be equal to or less than the first threshold L1, or the back electromotive force is determined. Although it is determined that the motor 2 has stopped when the electric power decreases to the second threshold value L2 or less, as another embodiment of the present invention, the threshold voltage is set to one, and the back electromotive force is reduced to You may make it determine with the motor having stopped when the setting time by a user passes from the time of becoming the threshold value L or less.

  In the embodiment described above, the back electromotive force of the motor is targeted as a target for detecting the stop of the machine driven by the motor. However, this target may be an input indicating the detection of the stop of the machine, and outputs from various sensors. The value may be, for example, voltage, current, load cell signal, temperature, rotation speed, flow rate, or the like, or may be information from a controller or network that controls the machine.

  The present invention is useful for detecting a stop of a motor that drives a machine in a production site where the machine and an operator coexist.

1 is a schematic configuration diagram of a safety system according to an embodiment of the present invention. It is a figure which shows the structure of the connection state of the power supply of FIG. 1, a motor, and a stop detection unit. It is a figure which shows the structure of a stop detection unit. It is a block diagram of a stop detection unit. It is a time chart for demonstrating a 1st criterion. It is a time chart for demonstrating a 2nd criteria. It is a time chart which shows the influence of the change of load. It is a flowchart with which operation | movement description is provided. It is a flowchart with which operation | movement description is provided. It is a time chart which shows stop determination by the 1st criteria. It is a time chart which shows stop determination by the 1st criteria.

Explanation of symbols

1 Power supply 2 Motor 3 Stop detection unit 4 Door 5 Door switch 7 Main magnet contactor

Claims (13)

A stop detection device for detecting a motor stop,
A counter electromotive force detection unit for detecting a counter electromotive force of the motor;
A determination unit that determines that the motor has stopped when a set time has elapsed since a detection value of the back electromotive force detection unit is equal to or less than a fixed threshold;
A setting unit for setting the set time as a digital value ;
A selection unit that selects whether to determine whether to stop the motor in any of the first and second determination modes;
The determination unit sets the fixed threshold value as a first threshold value, and the detection value of the back electromotive force detection unit is equal to or less than the first threshold value in the first determination mode according to the selection by the selection unit. It is determined that the motor has stopped when the determination time has elapsed from the point in time, and in the second determination mode, the detection value of the back electromotive force detection unit is less than or equal to a fixed second threshold value. When it becomes, it determines with the said motor having stopped, The stop detection apparatus characterized by the above-mentioned . A stop detection device for detecting a motor stop,
A counter electromotive force detection unit for detecting a counter electromotive force of the motor;
When a set time has elapsed since the detection value of the back electromotive force detection unit is equal to or less than a fixed first threshold value, or when the detection value is a fixed second value that is smaller than the first threshold value. A determination unit that determines that the motor has stopped when the threshold value is equal to or less than
And a setting unit configured to set the set time as a digital value. A selection unit that selects whether to determine whether to stop the motor in any of the first and second determination modes;
In response to the selection by the selection unit, the determination unit, in the first determination mode, the set time has elapsed since the detection value of the back electromotive force detection unit became equal to or less than the first threshold value. Or when the detected value becomes equal to or smaller than the second threshold value which is smaller than the first threshold value, it is determined that the motor has stopped, and in the second determination mode, the detected value value is determined. The stop detection device according to claim 2 , wherein the motor is determined to have stopped when the value becomes equal to or less than a fixed third threshold value. An output unit that outputs a determination result of the determination unit;
The output unit is configured to determine whether to stop the motor when the set time has elapsed from the time when the detected value is less than or equal to the first threshold, and the detected value is less than or equal to the second threshold. the determination result of the stop motor when the said detected value, and a determination result of the stop of the motor when it becomes less than the second threshold value, stop according to claim 2 or 3 outputs distinguishably Detection device. A contact input unit provided between a terminal of the motor and a power source, to which a contact input corresponding to a contact state of a switch for turning on / off the power to the motor is provided;
The determination unit is a precondition for determining that the motor has stopped based on the contact state from the contact input unit, that the contact of the switch is in an off state. The stop detection device according to any one of 4 . The stop detection device according to any one of claims 1 to 5 , wherein a determination result that the motor is stopped by the determination unit is used for unlocking an electromagnetic lock type door switch. The setting unit, the stop detection device as claimed in any one of claims 1 to 6 which is a digital setting switch. A stop detection method for detecting a motor stop,
A setting step for setting the set time as a digital value in advance;
A step of detecting the back electromotive force of the motor, and determining that the motor has stopped when the set time has elapsed from the time when the detected value becomes a fixed threshold value or less ;
A selection step of selecting one of the first and second determination modes for determining stop of the motor;
In the determination step, the fixed threshold value is set as a first threshold value, and the detection value of the back electromotive force detection unit is equal to or less than the first threshold value in the first determination mode according to the selection in the selection step. When the set time elapses from the time when the motor becomes, it is determined that the motor has stopped, and in the second determination mode, when the detected value is equal to or less than a fixed second threshold, A stop detection method characterized by determining that the motor has stopped . A stop detection method for detecting a motor stop,
A setting step for setting the set time as a digital value in advance;
The counter electromotive force of the motor is detected, and when the set time elapses from the time when the detected value becomes a fixed first threshold value or less, or the detected value is smaller than the first threshold value. A stop detection method comprising: a determination step of determining that the motor has stopped when it becomes equal to or less than a fixed second threshold value. A selection step of selecting one of the first and second determination modes for determining stop of the motor;
In the determination step, in accordance with the selection in the selection step, in the first determination mode, the determination time has elapsed since the detection value of the back electromotive force detection unit is equal to or less than the first threshold value. Or when the detected value becomes equal to or smaller than the second threshold value which is smaller than the first threshold value, it is determined that the motor has stopped, and in the second determination mode, the detected value value is determined. The stop detection method according to claim 9 , wherein the motor is determined to have stopped when the value becomes equal to or less than a fixed third threshold value. A motor, a switch for turning on / off the power to the motor, a stop detection device for detecting a stop of the motor and providing a detection output, and a work area where a machine driven by the motor is installed A safety system including an electromagnetic lock type door switch provided on a door for performing,
The stop detection device includes a back electromotive force detection unit that detects a back electromotive force of the motor, a contact input unit to which a contact input corresponding to a contact state of the switch is provided, and the contact state from the contact input unit When the contact of the switch is turned off and the set time has elapsed since the detection value of the back electromotive force detection unit becomes a fixed threshold value or less, the motor A determination unit that determines that the operation has stopped, and a setting unit that sets the set time as a digital value,
The determination result that the motor is stopped by the determination unit is used for unlocking the electromagnetic lock type door switch ,
The stop detection device includes a selection unit that selects whether to determine whether to stop the motor in one of the first and second determination modes.
The determination unit sets the fixed threshold as a first threshold, and according to the selection by the selection unit, in the first determination mode, the contact of the switch is in the off state, and the reverse When the set time has elapsed since the detection value of the electromotive force detection unit becomes equal to or less than the first threshold value, it is determined that the motor has stopped, and in the second determination mode, the switch A safety system that determines that the motor has stopped when the contact is turned off and the detection value of the back electromotive force detection unit is equal to or less than a fixed second threshold value. . A motor, a switch for turning on / off the power to the motor, a stop detection device for detecting a stop of the motor and providing a detection output, and a work area where a machine driven by the motor is installed A safety system including an electromagnetic lock type door switch provided on a door for performing,
The stop detection device includes a back electromotive force detection unit that detects a back electromotive force of the motor, a contact input unit to which a contact input corresponding to a contact state of the switch is provided, and the contact state from the contact input unit And when the set time has elapsed since the contact point of the switch is off and the detection value of the back electromotive force detection unit is equal to or lower than a fixed first threshold value, Alternatively, it is determined that the motor has stopped when the contact of the switch is turned off and the detection value is equal to or smaller than a fixed second threshold value that is smaller than the first threshold value. And a determination unit that sets the set time as a digital value,
A safety system, wherein the determination result by the determination unit that the motor is stopped is used for unlocking the electromagnetic lock type door switch. The stop detection device includes a selection unit that selects whether to determine whether to stop the motor in one of the first and second determination modes.
According to the selection by the selection unit, the determination unit is in a state where the contact of the switch is turned off in the first determination mode, and the detection value of the back electromotive force detection unit is the first value. When the set time has elapsed from the time when the threshold value becomes 1 or less, or when the contact of the switch is turned off, and the detection value is smaller than the first threshold value. When the threshold value is less than or equal to 2, it is determined that the motor has stopped. In the second determination mode, the contact of the switch is turned off, and the detection value is a fixed first value. The safety system according to claim 12 , wherein the motor is determined to have stopped when a threshold value of 3 or less is reached.

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