JP2009236676A - Speed detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect rotational speed, and to detect various kinds of abnormalities. <P>SOLUTION: The frequencies of detection pulses from first and second proximity sensors 9, 10 detecting the rotation of a rotating body 8 linked with a motor 2, respectively, are compared. When they do not agree with each other, it is determined that an abnormality occurs. According to at which side of a low frequency or a high frequency the disagreement in the frequencies is generated, the abnormality is classified to perform corresponding indication. Accordingly, it is grasped that the abnormalities such as the installation failure of the sensor or a wiring mistake are generated at the low frequency side or the abnormalities such as the abnormality of the sensor incapable of responding to high-speed rotation are generated at the high frequency side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a speed detection device that detects a rotational speed of a motor, and more specifically, a rotational speed of a motor that drives various machines in a production site where various machines and workers coexist or various plant facilities. The present invention relates to a speed detection device suitable for detecting

  Conventionally, various safety systems have been proposed to ensure safety in production sites where workers and machines such as machine tools and industrial robots coexist, such as machine tools and industrial robots. There has been proposed a system that monitors the stop of a motor that is a drive source of various machines, and can open the door of the entrance / exit of the work area of the various machines when the stop is confirmed (for example, Patent Documents) 1), in such a system, it is necessary to detect that the motor has stopped by detecting the rotational speed of the motor.

  Also, even when teaching teaching such as position teaching when approaching an industrial robot, it is necessary to detect the rotational speed of the motor that is the drive source and to monitor that the industrial robot is operating at low speed. is there.

  As a device for detecting the rotational speed of such a motor, for example, a rotating body having an uneven outer peripheral surface such as a gear or a doc is attached to a rotating shaft interlocking with the motor, and the unevenness of the outer peripheral surface of this rotating body is detected by a sensor. Thus, there is a device that monitors as a rotation pulse. However, when a failure occurs in the sensor, the rotation state of the rotating body cannot be detected.

In order to monitor the failure of the sensor, there is one in which a plurality of sensors are attached, a voltage supply source to the sensor is periodically cut off, and a potential difference in the output signal of the sensor is detected (for example, see Patent Document 2).
Japanese Patent No. 3344931 Japanese Patent Laid-Open No. 10-213291

  The monitoring device of Patent Document 2 monitors the opening / closing positions of protective covers such as doors and covers, and does not detect the rotational speed. In the safety system as described above, there is a sensor failure. However, it is desirable to detect various abnormalities.

  The present invention has been made in view of the above points, and an object of the present invention is to detect a rotational speed and detect various abnormalities.

  (1) The speed detection device of the present invention is a speed detection device that detects a rotation speed based on detection pulses from at least two sensors that respectively detect rotation of a rotating body, and the detection pulses from the two sensors. The frequency is compared, and abnormality diagnosis is performed.

  According to the speed detection device of the present invention, the rotational speed of the rotating body can be detected, and the presence or absence of an abnormality can be diagnosed by comparing the frequency of detection pulses from both sensors.

  (2) In one embodiment of the speed detection device of the present invention, when the frequencies of the two detection pulses do not coincide with each other, it is determined that there is an abnormality, and the frequency mismatch is detected on the low frequency side or the high frequency side. You may make it classify | categorize the said abnormality according to which side has arisen.

  Since the two sensors detect the rotation of the same rotating body, the frequency of the detection pulse of both sensors will match if it is normal, and if the frequency of the detection pulse does not match, it will be determined as abnormal can do.

  Also, if one of the two sensors has an abnormality during installation, for example, installation failure or wiring mistake, the detection pulses of both sensors will not match on the low frequency side. In addition, for example, when the rotating body of a rotating body that exceeds the detection performance of the sensor occurs and the response of the sensor cannot be followed or the sensor fails, the detection pulses of both sensors are used on the high frequency side. A discrepancy occurs.

  The boundary between the low frequency side and the high frequency side may be set in advance, or may be arbitrarily set by the user according to the application.

  As described above, this boundary is set so that the frequency mismatch of detection pulses due to abnormalities at the time of installation of sensors, etc. can be distinguished from the frequency mismatch of detection pulses due to abnormalities during operation after installation. It is preferable to do this. Further, this boundary may be, for example, a frequency that the user considers a safe low-speed rotation speed.

  According to this embodiment, an abnormality can be determined and, for example, an abnormality that occurs on the low frequency side, such as a sensor installation failure or a wiring mistake, or occurs on the high frequency side, for example, the response of the sensor cannot be followed by high-speed rotation. It is possible to classify whether it is abnormal.

  (3) In the embodiment of the above (2), when it is determined that there is an abnormality, a reporting means for reporting the abnormality according to the classification may be provided.

  According to this embodiment, when an abnormality occurs, it is notified whether the abnormality occurs on the low frequency side or the abnormality that occurs on the high frequency side. It is possible to determine whether the abnormality occurs on the low frequency side, such as a wiring error, or on the high frequency side, for example, the sensor response cannot be followed by high-speed rotation, and the abnormality can be easily identified. it can.

  (4) In one embodiment of the speed detection device of the present invention, detection means for detecting an abnormality based on the current value of the power supply line to both sensors, and the frequency and allowable speed of the detection pulse are supported. It is also possible to provide at least one of detecting means for detecting an abnormality by comparing with a threshold value to be detected.

  According to this embodiment, an abnormality such as disconnection of the power supply line or disconnection of the sensor can be detected based on the current value of the power supply line to both sensors, and it corresponds to the frequency of the detection pulse and the allowable speed. An abnormality such as overspeed can be detected by comparison with the threshold value.

  (5) In another embodiment of the speed detection device of the present invention, the outer circumferential surface of the rotating body is formed with irregularities along the circumferential direction, and the length along the circumferential direction of the concave portion is It is formed shorter than the length along the circumferential direction of the convex part, and both the sensors turn off the output in the concave part, turn on the output in the convex part, and when the rotating body is stopped, At least one of the two sensors is installed on the outer peripheral side of the rotating body so that the output is turned on. When the rotating body is stopped and the outputs of the two sensors are on, Based on the output of the one sensor when the power supply to the sensor is interrupted, the detection means for detecting the abnormality, and based on the outputs of the two sensors when the rotating body is stopped, the abnormality is detected. Of detection means to detect It may be provided with one of the detecting means or even without.

  According to this embodiment, in a state where the outputs of both sensors are on, a short circuit between the two sensors can be detected based on the output of the one sensor when the power supply to one of the sensors is shut off. Further, when both the outputs of the sensors when the rotating body is stopped are turned off, it is possible to detect an abnormality such as sensor dropout or disconnection of the output line of the sensor.

  (6) In the embodiment of the above (4) or (5), a reporting unit for reporting an abnormality detected by any of the detection units may be provided.

  According to this embodiment, since various abnormalities detected by the detecting means are reported, it becomes easy for the user to specify the abnormalities.

  (7) In another embodiment of the present invention, the rotating body rotates in conjunction with the rotation of the motor, and when the rotation speed detected based on the detection pulse becomes a threshold value or less. Gives a safe speed detection output.

  According to this embodiment, based on the safe speed detection output when the rotation speed of the motor becomes lower than the threshold value, for example, the user operates the machine tool driven by the motor at a low speed in the vicinity. It is possible to know that the work has become possible.

  (8) In still another embodiment of the present invention, the safety speed detection output is an electromagnetic lock type door switch provided on a door for entering and exiting a work area where a machine driven by the motor is installed. Is an unlock signal.

  In this embodiment, when the motor rotation speed falls below the threshold value and the motor stop is detected, it is assumed that the motor is safe, and the lock release signal is output to the door switch to release the lock. It is possible to enter the work area where the machine driven by is installed.

  As another embodiment of the present invention, it is possible to switch between a normal operation mode and a maintenance mode. In the normal operation mode, when a motor stop is detected as described above, a lock release signal is output, while maintenance is performed. In mode, when it detects that the rotation of the motor has become low speed, it outputs a lock release signal to unlock the door switch, and the worker enters the work area and performs maintenance work only at low speed. You may be able to do it. It is preferable to use an enable switch together during this maintenance work.

  According to the present invention, the rotational speed of the rotating body can be detected, and the presence or absence of abnormality can be diagnosed based on the comparison result of the frequency of the detection pulse from both sensors.

  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 including a speed detection unit as a speed detection device according to an embodiment of the present invention.

  This safety system detects a rotational speed of a three-phase AC power source 1, a three-phase motor 2 connected to the power source 1 and driving a machine tool (not shown), and the rotational speed of the motor 2 below a threshold value. When it becomes, it determines with the motor 2 having stopped, the speed detection unit 3 as a speed detection apparatus which outputs the lock release signal as a safe speed detection signal, and the work area | region where the motor 2 and the said machine tool are arrange | positioned An electromagnetic lock type door switch 4 that is installed at the door of the doorway and is given a lock release signal from the speed detection unit 3 is provided.

  Based on the output of the door switch 4, the speed detection unit 3 is duplexed to turn on / off the power to the motor 2 in response to an operation of a start / stop switch (not shown) on the condition that the door is closed. ON / OFF of the contacts of the magnetic contactors 5 and 6 thus controlled is controlled.

  The work area where the motor 2 and the machine tool are installed is surrounded by a safety fence or the like, and the above-mentioned door serving as an entrance to the work area is installed in the safety fence. A lock type door switch 4 is attached. The door switch 4 has, for example, a switch body that is attached to the fixed frame side of the door, and an operation key that is inserted into and removed from the opening of the switch body is attached to the movable part side of the door, and the door is closed and operated. When the key is inserted into the opening of the switch body, it is mechanically locked and prohibits the opening of the door. Further, when a lock release signal, which is a safe speed detection signal, is given from the speed detection unit 3 to the door switch 4, the solenoid is operated, so that the lock is released and the door can be opened. Entering the area is allowed.

  The door switch 4 gives a safety-side safety output that allows the machine tool to be driven when the door is closed, while the door 4 is open. Gives a dangerous safety output that prohibits the machine from driving.

  The speed detection unit 3 of this embodiment is equipped with a microcomputer, and controls on / off of the contacts of the magnetic contactors 5 and 6 according to a program based on a safety input from the door switch 4. On the condition that the safety input from is on the safe side, the contacts of the magnetic contactors 5 and 6 are turned on to supply power to the motor 2 according to the operation of a start switch (not shown), while the power from the door switch 4 When the safety input is on the dangerous side, the contacts of the magnet contactors 5 and 6 are turned off to cut off the power supply to the motor 2.

  The speed detection unit 3 of this embodiment is based on the detection pulses from the first and second proximity sensors 9 and 10 that detect the rotation of the rotating body 8 attached to the rotating shaft 7 of the motor 2. The rotation speed is detected, and an abnormality in speed detection is diagnosed as described later.

  As shown in FIG. 2, the rotator 8 has unevenness formed on the outer peripheral surface thereof along the circumferential direction. The unevenness is formed such that the length along the circumferential direction of the concave portion 8a is shorter than the length along the circumferential direction of the convex portion 8b.

  The proximity sensors 9 and 10 are respectively installed on the outer peripheral side of the rotating body 8, and when the projecting portion 8b of the rotating body 8 opposes, an on (high level) output is given, while the recessed portion 8a of the rotating body opposes. Sometimes it gives off (low level) output.

  In this way, if the convex portion 8b can be turned on and the concave portion 8a can be turned off, it is sufficient that the proximity sensors 9 and 10 are installed on the outer peripheral side of the rotating body 8. There are no restrictions such as the direction and inclination of 9,10.

  The proximity sensors 9 and 10 are installed such that the output of at least one of the proximity sensors 9 and 10 is turned on when the rotating body 8 is stopped. That is, when the rotating body 8 is stopped in a normal state, the output of at least one of the proximity sensors 9 and 10 is turned on, and the outputs of the proximity sensors 9 and 10 are both turned off. There is no.

  When the rotating body 8 interlocked with the motor 2 rotates at a low speed in a normal state, the first and second proximity sensors 9 and 10 detect low-frequency detection pulses shown in FIGS. 3 (a) and 3 (b). When the rotator 8 rotates at a high speed, the first and second proximity sensors 9 and 10 output high-frequency detection pulses shown in FIGS.

  FIG. 5 is a block diagram of the main part of the speed detection unit 3, and the same reference numerals are given to the parts corresponding to FIG. The speed detection unit 3 of this embodiment includes a door switch input unit 11 to which an input of the door switch 4 is given, a rotation detection input unit 12 to which outputs of the first and second proximity sensors 9 and 10 are given, and a door Based on the input from the switch input unit 11, on the condition that the door is closed, a safety instantaneous output for turning on the contacts of the magnetic contactors 5 and 6 is supplied via the safety instantaneous output units 13 and 14 according to the program. On the other hand, based on the detection pulse from the rotation detection input unit 12, an abnormality diagnosis is performed as will be described later, and when the rotation speed of the motor 2 is below a threshold value, it is determined that the motor 2 has stopped. The control unit 16 outputs a lock release signal as a safe speed detection signal to the door switch 4 via the safe speed detection output unit 15.

  As shown in FIG. 6, the control unit 16 includes first and second CPUs 17 and 18. The outputs of the first and second proximity sensors 9 and 10 are input to the CPUs 17 and 18, respectively. The signals are given through the terminals 20 and 21 and the rotation detection input unit 12 described above, and are duplicated by executing the same processing in the CPUs 17 and 18, respectively. A power output unit 19 supplies power to the sensors 9 and 10 through power output terminals 22 and 23.

  FIG. 7 is a flowchart for explaining the operation of this embodiment.

  Based on the inputs of the first and second proximity sensors 9 and 10, a rotation detection input determination process is executed (step n1). In this process, first, the input level is read (step n2), the frequency of the detection pulse from each proximity sensor 9, 10 is calculated (step n3), and it is determined whether or not the frequencies match (step n4). ), Perform abnormality diagnosis. If the frequencies match in step n4, it is determined that the frequency is normal, and the process proceeds to an output determination process described later (step n5).

  In the normal state, as shown in FIG. 3 and FIG. 4 described above, the frequency of the detection pulse from the first and second proximity sensors 9 and 10 is high at both low speed rotation and high speed rotation. Match.

  In the output determination process, as shown in FIG. 8, it is determined whether or not the rotation speed of the motor 2 is equal to or less than a threshold value (step n5-1). Then, the lock release signal, which is a safety speed detection signal, is turned on (step n5-2), and if it is not less than the threshold value, the safety detection signal is turned off and the process ends (step n5-3).

  Referring to FIG. 7 again, in step n4, if the frequencies do not match, it is determined that there is an abnormality, and the frequency band in which the frequency mismatch occurs is on the high frequency side or on the low frequency side. If it is on the low frequency side, it is determined that there is an abnormality on the low frequency side, and as shown in FIG. 9A, for example, a display (not shown) provided in the speed detection unit 3 The lamp blinks once to notify that a low frequency abnormality has occurred. Further, when the frequency band in which the frequency mismatch occurs is on the high frequency side, as shown in FIG. 9B, for example, the indicator lamp blinks twice as shown in FIG. Notify that an abnormality has occurred on the high frequency side.

  Here, the abnormality on the low frequency side and the high frequency side will be described.

  For example, if the output of one proximity sensor is not connected to the stop detection unit 3 at the time of installation, or if one of the proximity sensors has caused an installation failure, for example, as shown in FIG. The frequency of the detection pulse from both proximity sensors does not match on the low frequency side.

  Therefore, when the frequency band in which the frequency mismatch of the detection pulses occurs is on the low frequency side, it can be seen that there is an abnormality in installation such as a wiring mistake.

  Also, for example, if the proximity sensor fails during operation, the proximity sensor malfunctions due to excessive noise, or the rotation of the proximity sensor exceeds the detection performance of the proximity sensor due to motor runaway, the proximity sensor response can not catch up, Since the detection pulses from the proximity sensors do not normally indicate an on / off state, for example, as shown in FIG. 11, the frequencies of the detection pulses from both proximity sensors do not match on the high frequency side.

  In particular, on the danger side (state) where the proximity sensor fails or the response of the proximity sensor cannot catch up at all due to high-speed rotation, the outputs of both proximity sensors are both fixed to the on (high level) state. Thus, it cannot be distinguished from the state where the rotating body is stopped and the outputs of both proximity sensors are both on, that is, the stopped state of the motor on the safe side (state). In this embodiment, before the outputs of both proximity sensors are fixed to the ON state, an abnormality is detected from the frequency mismatch on the high frequency side, so that the above-mentioned inherently dangerous side (state) can be used. This eliminates the possibility of misidentifying a certain state as a safe side (state).

  As described above, when the frequency band in which the frequency mismatch of the detection pulses occurs is on the high frequency side, it can be understood that there is an abnormality after installation such as an abnormality in the response of the proximity sensor.

  As described above, depending on whether the frequency mismatch occurred on the low frequency side or the high frequency side, it may be an installation / wiring mistake on the speed detection unit side, or the life of the proximity sensor after operation or the proximity sensor periphery Thus, it is possible to distinguish whether there is an abnormality on the proximity sensor side such as the influence of the external environment, and since a report is made according to the distinction, the user can easily identify the cause of the abnormality.

(Other embodiments)
In the above-described embodiment, the abnormality is classified and reported as an abnormality on the low frequency side and an abnormality on the high frequency side. However, as another embodiment of the present invention, You may add the function as a following detection means which detects various abnormalities, respectively.

  You may provide the detection means which detects the short circuit failure between the 1st, 2nd proximity sensors 9 and 10. FIG. In this detection means, the rotation of the rotating body 8 is stopped, and the outputs of the first and second proximity sensors 9 and 10 are both on, as shown in FIGS. 12 (a) and 12 (b). When power supply to one proximity sensor, for example, the first proximity sensor 9 is cut off as shown in FIG. 12C, the first proximity sensor is shown as shown by a solid line in FIG. When the output of the first proximity sensor 9 remains on, as shown by the broken line in FIG. 12A, the first and second proximity sensors 9 are determined to be normal. , 10 is determined to be a short-circuit failure.

  Moreover, you may provide the detection means which detects the abnormality of the connection between the 1st, 2nd proximity sensors 9 and 10 and the speed detection unit 3. FIG. As shown in FIG. 13, the detection means is provided with a diode D, a resistor R, and a current monitoring circuit 24 in a power supply line from a power output unit 19 to a proximity sensor, for example, the first proximity sensor 9, When a current of a certain value or more flows to the proximity sensor 9 of the first proximity sensor 9 and the current of a certain value or more is not flowing, the 24 V power input line or ground line of the first proximity sensor 9 is disconnected or the speed Abnormalities such as disconnection of the first proximity sensor 9 to the detection unit 3 can be detected.

  Moreover, you may provide the detection means which detects abnormality, such as the installation defect of a proximity sensor. In the state where the rotation of the rotating body 8 is stopped, this detection means turns on the output of at least one of the proximity sensors 9 and 10 as shown in FIG. Both outputs are not turned off. Therefore, in a state where the rotation of the rotating body 8 is stopped, it is monitored that the outputs of both the proximity sensors 9 and 10 are not turned off, and when both are turned off, one of the proximity sensors falls off. It is possible to detect an installation failure such as being present, or an abnormality such as the output line of the proximity sensor being disconnected.

  Furthermore, an upper limit of a frequency band that can be detected may be provided to monitor overspeed, and the rotation of the motor that reaches the upper limit may be detected as a runaway.

  Each detection means as described above may be added to report an abnormality detected by each detection means.

  That is, as shown in the flowchart of FIG. 14, frequency mismatch on the low frequency side, short circuit between inputs, sensor current monitoring, both inputs off, frequency mismatch on the high frequency side, and overspeed are detected. The corresponding display, for example, the corresponding indicator lamp may be blinked individually.

  In each of the above-described embodiments, description has been made by applying to a proximity sensor. However, the present invention is not limited to a proximity sensor, and can be applied to other sensors such as a photoelectric sensor.

  The present invention is useful for ensuring safety by detecting the rotational speed of a drive source of a machine in a production site where the machine and an operator coexist.

It is a schematic block diagram of a safety system provided with the speed detection unit which concerns on embodiment of this invention. It is a figure which shows arrangement | positioning of a rotary body and a proximity sensor. It is a figure which shows the detection pulse at the time of low speed rotation. It is a figure which shows the detection pulse at the time of high speed rotation. It is a block diagram of a speed detection unit. It is a figure which shows the structure of the control part of FIG. It is a flowchart with which operation | movement description is provided. It is a flowchart of an output determination process. It is a figure which shows the example of a display of abnormality. It is a figure which shows the mismatch of the frequency in the low frequency side. It is a figure which shows the mismatch of the frequency in the high frequency side. It is a figure for demonstrating the short circuit abnormality of a proximity sensor. It is a figure which shows the structure of the monitoring of the electric current to a proximity sensor. It is a flowchart of the abnormality detection process of other embodiment of this invention.

Explanation of symbols

1 power supply 2 motor 3 speed detection unit (speed detection device)
4 Door switch 8 Rotating body 9, 10 First and second proximity sensors

Claims (8)

A speed detection device that detects a rotation speed based on detection pulses from at least two sensors that respectively detect the rotation of the rotating body,
An abnormality diagnosis is performed by comparing frequencies of detection pulses from the two sensors.   When the frequency of the two detection pulses does not match, it is determined that there is an abnormality, and the abnormality is classified according to whether the frequency mismatch occurs on the low frequency side or the high frequency side. Item 2. The speed detection device according to Item 1.   The speed detection apparatus according to claim 2, further comprising reporting means for reporting the abnormality according to the classification when it is determined as abnormal.   At least one of detection means for detecting an abnormality based on the current value of the power supply line to both sensors, and detection means for detecting an abnormality by comparing the frequency of the detection pulse and a threshold value corresponding to an allowable speed The speed detection device according to any one of claims 1 to 3, further comprising either one of the detection means. On the outer peripheral surface of the rotating body, irregularities are formed along the circumferential direction, and the length along the circumferential direction of the concave portion is formed shorter than the length along the circumferential direction of the convex portion, The two sensors turn off the output at the concave portion and turn on the output at the convex portion, and the rotation so that the output of at least one of the two sensors is turned on when the rotating body is stopped. Are installed on the outer circumference of the body,
Detecting means for detecting an abnormality based on the output of one of the sensors when the rotation of the rotating body is stopped and the outputs of the two sensors are turned on; The speed detection as described in any one of Claims 1-4 provided with at least any one detection means of the detection means which detects abnormality based on the output of both said sensors when the said rotary body has stopped. apparatus.   The speed detection apparatus according to claim 4, further comprising a reporting unit that reports an abnormality detected by any of the detection units.   The rotating body rotates in conjunction with the rotation of a motor, and provides a safe speed detection output when a rotation speed detected based on the detection pulse becomes a threshold value or less. The speed detection apparatus as described in any one of.   The said safe speed detection output is a lock release signal to the electromagnetic lock type door switch provided in the door for entering and exiting into the work area where the machine driven by the motor is installed. Speed detection device.

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