JP5480563B2 - Anomaly detection method and anomaly detection apparatus for screw feeder - Google Patents

Description

  The present invention relates to a method and an abnormality detection device for detecting an abnormality in which a distance between a screw of a screw feeder and an inner surface of a screw case is narrowed.

  Conventionally, a screw feeder has been used to quantitatively supply powder particles. The screw feeder is provided with a screw inside a screw case, and the granular material put in from the inlet of the screw feeder is quantitatively discharged by the rotation of the screw.

  In order to increase the quantitative accuracy of the screw feeder, it is preferable to make the distance between the screw and the inner surface of the screw case as narrow as possible. The distance between the screw and the inner surface of the screw case is usually designed to be about 10 mm. However, for example, when powder particles are introduced to the screw feeder, the screw rotation axis is displaced or the screw vibrates due to the weight of the offset powder particles. If the inner surface of the screw approaches and eventually comes into contact with each other and gets scratched, the function of the screw feeder will be reduced. Furthermore, the metal powder produced by the contact between the screw and the screw case may be mixed into the quantified granular material (for example, product) to cause quality problems.

  Therefore, in order to prevent such a problem, an attempt has been made to detect an abnormality in which the distance between the screw and the screw case inner surface is narrowed. For example, Patent Document 1 discloses a method of detecting an abnormality in which the distance between the screw and the screw case inner surface is narrowed by providing an eddy current sensor on the outer peripheral surface of the screw case.

JP 2009-12917 A (published January 22, 2009)

  However, in the method disclosed in Patent Document 1, since the center axis of the coil of the eddy current sensor is attached so as to be perpendicular to the rotation axis of the screw, the signals obtained from the eddy current sensor have different amplitude values. Two peaks (signals) are detected. For this reason, it has the subject that it is difficult to judge which peak of the two peaks is detected and analyzed as an abnormality in which the interval between the screw and the screw case inner surface is narrowed.

  The present invention has been made in view of the above problems, and its object is to easily detect and analyze a signal and to reliably detect an abnormality in which the distance between the screw of the screw feeder and the inner surface of the screw case is narrowed. It is an object of the present invention to provide an abnormality detection method and an abnormality detection apparatus that can perform the above-described problem.

In order to solve the above problem, the abnormality detecting method according to the present invention is a method for detecting an abnormality distance between the screw and the screw casing of the inner surface of the scan clew feeder is narrowed, the vortex with respect to the rotation axis of the screw The eddy current sensor having a pair of coils is attached to the outer peripheral surface of the screw case so that the central axis of the coil of the current sensor is in a twisted or parallel position, and the first coil and the second coil The distance between the screw and the inner surface of the screw case is measured based on a change in eddy current induced by the eddy current sensor with different directions.

  According to the abnormality detection method of the present invention, the eddy current sensor is attached to the outer peripheral surface of the screw case so that the center axis of the coil of the eddy current sensor is twisted or parallel to the rotational axis of the screw. When the screw passes through the magnetic flux of the coil, only one eddy current is generated. That is, since the change (voltage change) of the eddy current induced by the eddy current sensor is obtained as one peak (signal), the detection and analysis of the signal becomes easy, and the screw of the screw feeder and the inner surface of the screw case It is possible to reliably detect an abnormality in which the interval is narrowed.

  In addition, by changing the direction of current between the first coil and the second coil, eddy current changes (voltage changes) induced from the respective eddy current sensors can be used as both positive and negative fluctuation signals. Can be detected. For this reason, detection and analysis of signals are easier.

  In the abnormality detection method according to the present invention, it is preferable that the eddy current sensor is arranged so that the central axes of the pair of coils are parallel to each other.

  The sensitivity of the eddy current sensor differs depending on the inclination of the central axis of the coil with respect to the inclination of the blade in the screw (inclination relative to the rotation axis). By arranging the eddy current sensor so that the central axes of the pair of coils are parallel to each other, the inclination of the central axis of the coil with respect to the inclination of the blade in the screw can be made uniform. For this reason, the sensitivity of the first coil and the sensitivity of the second coil are the same, and the reliability of abnormality detection is improved.

  In the abnormality detection method according to the present invention, it is preferable that the eddy current sensor is attached so that the blade inclination of the screw and the central axes of the pair of coils of the eddy current sensor are perpendicular to each other.

  By attaching the eddy current sensor so that the blade inclination of the screw and the central axis of the coil of the eddy current sensor are vertical, the blade inclination of the screw and the coil inclination of the eddy current sensor are made vertical. be able to. Thereby, the change (voltage change) of the eddy current induced by the eddy current sensor can be maximized. That is, the sensitivity of the eddy current sensor can be improved as compared with the case where the blades of the screw and the coil of the eddy current sensor are attached so as not to be perpendicular to each other.

  In the abnormality detection method according to the present invention, it is preferable to pass an alternating current having a frequency of 1 kHz to 5 kHz through the eddy current sensor.

  The sensitivity of the eddy current sensor can be improved by flowing an alternating current having a frequency in the above range to the eddy current sensor.

  In order to solve the above problems, an abnormality detection apparatus according to the present invention is an apparatus for detecting an abnormality in which the distance between the screw of the screw feeder and the inner surface of the screw case is narrowed, and is provided on the rotating shaft of the screw. The eddy current sensor includes a eddy current sensor having a pair of coils attached to the outer peripheral surface of the screw case so that the central axis of the coil of the eddy current sensor is in a twisted or parallel position, and the first coil and the second coil. Current supply means for supplying current so that current directions are different from each other, and measurement means for measuring a distance between the screw and the inner surface of the screw case from a change in eddy current induced by the eddy current sensor; It is characterized by having.

  Each of the pair of coils included in the eddy current sensor provided in the abnormality detection device according to the present invention induces eddy current. That is, in the abnormality detection device according to the present invention, since two eddy current changes are detected, the reliability of abnormality detection is high. Further, the current supply means supplies the current in the first coil and the second coil so that the directions of the currents are different from each other, so that the change in eddy current (voltage change) induced by each coil is detected. It can be detected as both plus and minus shake signals. For this reason, detection and analysis of signals are easy.

  In the abnormality detection apparatus according to the present invention, the current supply means preferably supplies an alternating current having a frequency of 1 kHz to 5 kHz.

  By passing an alternating current having a frequency in the above range to the eddy current sensor, the sensitivity of abnormality detection in the abnormality detection device can be improved.

  In the abnormality detection apparatus according to the present invention, it is preferable that the eddy current sensor is disposed on an outer peripheral surface of the screw case so that central axes of the pair of coils are parallel to each other.

  The sensitivity of the eddy current sensor differs depending on the inclination of the central axis of the coil with respect to the inclination of the blade in the screw (inclination relative to the rotation axis). By arranging the eddy current sensor so that the central axes of the pair of coils are parallel to each other, the inclination of the central axis of the coil with respect to the inclination of the blades of the screw can be made uniform. For this reason, the sensitivity of the first coil and the sensitivity of the second coil are the same, and the reliability of abnormality detection in the abnormality detection device is improved.

  The abnormality detection apparatus according to the present invention preferably further includes display means for displaying a result measured by the measurement means.

  The abnormality detection apparatus according to the present invention further includes the display unit, so that signal detection and analysis are facilitated.

  In the abnormality detection method according to the present invention, the eddy current sensor is attached to the outer peripheral surface of the screw case so that the center axis of the coil of the eddy current sensor is twisted or parallel to the rotational axis of the screw. The second coil and the second coil have different current directions.

  Moreover, the abnormality detection apparatus according to the present invention has a pair of coils attached to the outer peripheral surface of the screw case so that the central axis of the coil of the eddy current sensor is twisted or parallel to the rotational axis of the screw. The eddy current sensor includes a current supply means for supplying current so that the directions of the currents of the first coil and the second coil are different from each other, and a change in the eddy current induced by the eddy current sensor. The measuring device measures the distance between the screw and the inner surface of the screw case.

  According to the present invention, since the change (voltage change) of the eddy current induced by the eddy current sensor is obtained as one peak (signal), the signal can be easily detected and analyzed, and the screw and screw case of the screw feeder. It is possible to reliably detect an anomaly in which the distance from the inner surface of the substrate is reduced. As a result, the screw and the screw case come into contact with each other and get scratched, or metal powder formed by such contact is mixed into the quantified granular material (for example, product), causing quality problems. There is an effect that this can be avoided.

It is sectional drawing which shows roughly the attachment position of the eddy current sensor with respect to a vertical screw feeder. It is a figure which shows schematically the coil which an eddy current sensor has, (a) is sectional drawing of the thickness direction of a coil, (b) is a top view of a coil. In FIG. 2, “w” represents the width of the coil, and “t” represents the length of the coil. It is sectional drawing which shows schematically the positional relationship of an eddy current sensor and a screw. It is a figure which shows schematically the coil fixed to the jig, (a) is a front view, (b) is a side view. “T” in FIG. 4 represents the thickness of the jig. It is sectional drawing which shows schematically the structure of the mockup of the screw feeder used in the Example of this invention, and the attachment position of the eddy current sensor to the mockup of a screw feeder. “H” in FIG. 5 represents the distance from the upper end of the mockup of the screw feeder to the center of the coil. It is the graph which shows the voltage change of the eddy current sensor in the mock-up of the screw feeder obtained in the Example of this invention, (a) represents the result of the eddy current sensor which has a pair of 10 mm diameter square coils, (B) represents the result of an eddy current sensor having a pair of square coils with a diameter of 15 mm, and (c) represents the result of an eddy current sensor having a pair of square coils with a diameter of 20 mm. It is a front view which shows roughly arrangement | positioning of a pair of coil. It is a block diagram which shows arrangement | positioning of an eddy current sensor and an eddy current flaw detector.

  An embodiment of the present invention will be described as follows, but the present invention is not limited to this embodiment.

  In the present specification, “A to B” indicating a numerical range indicates “A or more and B or less”.

[1. (Abnormality detection method)
Abnormality detecting method of this invention, the scan spacing between the screw and the screw casing of the inner surface of the clew feeder A method for detecting a narrowing abnormal, the screw and the screw from a change in the eddy currents induced by the eddy current sensor It is a method characterized by measuring the distance from the inner surface of the case . Specifically, the eddy current sensor having a pair of coils is attached to the outer peripheral surface of the screw case so that the center axis of the coil of the eddy current sensor is twisted or parallel to the rotational axis of the screw. By measuring the distance between the screw and the inner surface of the screw case from the change in eddy current induced by the eddy current sensor, an abnormality in which the distance between the screw of the screw feeder and the inner surface of the screw case is narrowed is detected.

  In the present specification, the “interval between the screw and the inner surface of the screw case” is intended to be ½ of the difference between the diameter of the cylinder in which the screw is inscribed and the inner diameter of the screw case. The “abnormality” is intended to mean that the “interval between the screw and the inner surface of the screw case” is equal to or less than a predetermined range (safety reference value). The “detection” is used synonymously with detection, measurement, measurement, and the like.

  Here, the screw feeder will be described with reference to the cross-sectional view shown in FIG. FIG. 1 is a cross-sectional view schematically showing a mounting position of the eddy current sensor 30 with respect to the vertical screw feeder 200. The screw feeder 200 is provided with a hopper 21 on an upper portion of a cylindrical screw case 22. A screw 23 is disposed at the center of the screw case, and its rotating shaft passes through the center of the hopper 21 and is rotatably supported by a bearing 25. A rake 24 is provided at a portion of the rotating shaft of the screw located at the hopper 21. And the rotational force of the motor which is not shown in figure is transmitted to a rotating shaft via a reduction gear, and the screw 23 rotates. Powder particles (not shown) are supplied from the inlet 26, and the powder particles around the hopper 21 are collected at the center by the rake 24, moved downward by the rotation of the screw 23, and quantitatively discharged from the outlet 27. Discharged. Known vertical screw feeders include a cantilever screw feeder in which one end of a rotating shaft of the screw is supported by a bearing, and a double-ended screw feeder in which both ends of the rotating shaft of the screw are supported by a bearing.

  The screw feeder targeted by the abnormality detection method according to the present invention is not limited to the vertical screw feeder as shown in FIG. For example, a horizontal screw feeder in which the rotational axis of the screw is provided horizontally (parallel to the installation surface) is also included in the screw feeder targeted by the abnormality detection method according to the present invention.

  Here, an embodiment of the coil 10 included in the eddy current sensor 30 used in the abnormality detection method according to the present invention will be described with reference to FIG. 2A and 2B are diagrams schematically showing the coil 10 included in the eddy current sensor 30, wherein FIG. 2A is a sectional view in the thickness direction of the coil 10, and FIG. 2B is a plan view of the coil 10. FIG. “W” in FIG. 2 represents the width of the coil 10, and “t” represents the length of the coil 10. As shown in FIG. 2A, the coil 10 is formed by winding the wire 1 around the axis of the bobbin 2 a predetermined number of times.

  The coil 10 is usually manufactured by winding the wire 1 having a diameter of 0.05 to 0.5 mm around the axis of the bobbin 2 200 to 350 times. As the strand 1, for example, an enameled wire that is usually used for manufacturing a coil can be used, but the present invention is not limited to this. As the bobbin 2, for example, a magnet, ferrite, a high permeability metal, or the like can be used, but the present invention is not limited to these. Examples of the high magnetic permeability metal include S15C, 4-79Mo permalloy, 86Ni electrodeposited permalloy, and 49Co-2V-Fe permender. In the examples described later, the bobbin 2 used was annealed S15C. The magnetic permeability of carbon steel can be improved by annealing carbon steel such as S15C. In the present embodiment, the coil 10 is a square coil, but may be a round coil. Since a square coil can be brought into contact with the screw case without any gap, the coil 10 is preferably a square coil from the viewpoint of improving the sensitivity of the eddy current sensor.

  The size of the coil 10 can be appropriately selected in consideration of the size of the screw feeder to which the eddy current sensor is attached, the shape of the screw provided in the screw feeder, and the like. The diameter of the coil 10 is usually 10 to 40 mm, preferably 15 to 20 mm. Here, the “diameter of the coil 10” refers to the diameter of the round coil when the coil 10 is a round coil, and when the coil 10 is a square coil, (b) of FIG. ) Indicates the diameter of a circle inscribed by the rectangular coil as viewed from the direction indicated by (). The length of the coil 10 (represented by “t” in FIG. 2) is usually 1 to 10 mm, preferably 2 to 5 mm. In this specification, “the size of the coil 10” refers to the diameter of the coil 10 unless otherwise specified.

  As shown in FIG. 1, the eddy current sensor 30 is attached to the screw feeder 200 such that the central axis of the coil 10 of the eddy current sensor 30 is twisted or parallel to the axis of the screw 23. It is preferably attached so as to be in a twisted position.

  FIG. 3 is a cross-sectional view schematically showing the positional relationship between the eddy current sensor 30 and the screw 23. A one-dot chain line shown in FIG. 3 represents the central axis of the coil 10 of the eddy current sensor 30. As shown in FIG. 3, a magnetic flux 6 is generated from the coil 10. When the screw 23 passes through the magnetic flux 6, the eddy current 7 flows through the screw 23 and a voltage change occurs in the coil 10. In the abnormality detection method according to the present invention, the coil 10 is attached to the outer peripheral surface of the screw case 22 so that the central axis 8 of the coil 10 of the eddy current sensor is twisted or parallel to the rotational axis of the screw 23. One eddy current 7 is induced from the coil 10. Therefore, the detection signal when the blades of the screw 23 pass can be detected as one peak.

  Further, from the viewpoint of improving the sensitivity of the eddy current sensor 30, the blade inclination of the screw 23 of the screw feeder 200 (inclination with respect to the rotation axis) and the central axis 8 of the coil 10 of the eddy current sensor 30 are perpendicular to each other. The coil 10 is preferably attached. Thereby, the inclination of the blade | wing in a screw and the inclination of the coil 10 in the eddy current sensor 30 can be made perpendicular | vertical. Thereby, the change (voltage change) of the eddy current induced by the eddy current sensor 30 can be maximized. That is, the sensitivity of the eddy current sensor 30 can be improved as compared with the case where the blades of the screw and the coil 10 of the eddy current sensor 30 are attached so that the inclination of the coil 10 is not perpendicular.

  Further, the direction of the current is made different between one coil (first coil) and the other coil (second coil) of the eddy current sensor 30. As a result, the reliability of abnormality detection can be improved. The above-mentioned “different current directions” means that, for example, when a positive current is applied to the first coil, a negative current is applied to the second coil. With such a configuration, a change in eddy current (voltage change) induced by each coil can be detected as both a plus and minus shake signal, so that signal detection and analysis are facilitated.

  In addition, as long as each coil does not mutually interfere, the attachment position of a 1st coil and a 2nd coil is not specifically limited. For example, a pair of coils may be mounted close to each other. However, if one coil is attached to the other coil by a distance corresponding to the distance (pitch) between the blades of the screw 23, the pair of coils generate eddy currents at the same time, and the voltage between the coils. Therefore, the first coil and the second coil are preferably attached at intervals that do not match the interval (pitch) between the blades of the screw 23.

  Further, from the viewpoint of improving the reliability of abnormality detection, it is preferable to arrange the pair of coils so that the central axes of the coils are parallel to each other. The sensitivity of the eddy current sensor differs depending on the inclination of the central axis of the coil with respect to the inclination of the blade in the screw 23 (inclination with respect to the rotation axis). By arranging the pair of coils so that the central axes of the coils are parallel to each other, the inclination of the central axis of the coil with respect to the inclination of the blades in the screw 23 can be made uniform. For this reason, the sensitivity of the first coil and the sensitivity of the second coil are the same, and the reliability of abnormality detection is improved.

  As shown in the examples described later, the first coil and the second coil are connected to the eddy current flaw detector 11 (FIG. 1) using a bridge circuit (current supply means).

  The mounting position of the eddy current sensor 30 in the screw feeder 200 is not particularly limited as long as it is the outer peripheral surface of the screw case 22. For example, when the eddy current sensor 30 is attached to a cantilever screw feeder in which only one end of the rotating shaft of the screw 23 is supported by the bearing 25, the outer peripheral surface of the screw case 22 corresponding to the position on the free end side of the rotating shaft. In addition, it is preferable to attach the eddy current sensor 30. Further, when the eddy current sensor 30 is attached to a both-end screw feeder in which both ends of the rotating shaft of the screw 23 are supported by the bearing 25, an eddy current is formed on the outer peripheral surface of the screw case 22 corresponding to the center position of the rotating shaft. It is preferable to attach the sensor 30. Since such a position is away from the bearing 25, the amount of displacement of the rotating shaft is larger than that of other positions on the rotating shaft of the screw 23. Therefore, the sensitivity of the eddy current sensor 30 can be further improved by attaching the eddy current sensor 30 to such a position. As a result, an abnormality in which the distance between the screw 23 and the inner surface of the screw case 22 is narrowed can be detected efficiently.

  Further, in the present embodiment, the eddy current sensor 30 is attached to the outer peripheral surface of the screw case 22, but a recess may be provided in the screw case 22 so that the eddy current sensor 30 can be attached closer to the screw 23.

  The means for attaching the eddy current sensor 30 to the outer peripheral surface of the screw case 22 is not particularly limited. For example, the eddy current sensor 30 may be directly attached to the screw case 22 using a screw, an adhesive, or the like. Further, the coil 10 may be fixed to the jig 3 shown in FIG. 4 described later, and the eddy current sensor 30 may be attached to the screw case 22 via the jig 3.

  4A and 4B are diagrams schematically showing the coil 10 fixed to a jig, where FIG. 4A is a front view and FIG. 4B is a side view. “T” in FIG. 4 represents the thickness of the jig. As shown to (a) of FIG. 4, it becomes easy to fix the eddy current sensor 30 to the outer peripheral surface of the screw case 22 by setting it as the structure which fixed the coil 10 to the jig 3. As shown in FIG.

  The size of the jig 3 is not particularly limited, but the thickness T of the jig 3 preferably matches that of the coil 10. In the present embodiment, a square prismatic coil as shown in FIG. 2B is used as the coil 10, and the thickness T of the jig 3 is made to coincide with the width w of the coil 10 (FIG. 2). ing.

  As described above, from the viewpoint of improving the sensitivity of the eddy current sensor 30, the eddy current sensor 30 is preferably in contact (adhered) to the screw case 22 without a gap. For this reason, it is preferable that the shape of the surface which contacts the outer peripheral surface of the screw case 22 in the jig 3 is a curved surface matching the shape of the outer peripheral surface of the screw case 22. In the examples described later, Araldite (trade name), which is a two-component mixed epoxy adhesive, is used as a material for forming the jig 3, but the present invention is not limited to this.

  In addition, as described above, from the viewpoint of improving the sensitivity of the eddy current sensor 30, the blade inclination (inclination with respect to the rotation axis) of the screw 23 (FIG. 1) and the central axes of the pair of coils 10 included in the eddy current sensor 30. It is preferable to attach the coil 10 so that and are perpendicular to each other. In this case, for example, if the angle as the blade inclination in the screw 23 is “r”, the inclination of the coil 10 with respect to the lower side of the jig 3 becomes the angle r as shown in FIG. The coil 10 may be fixed to the jig 3. The “angle r as the blade inclination of the screw” can be obtained by the following equation (1).

r = 90 ° − (angle formed by the rotating shaft of the screw and the blade) (1)
With the above configuration, the eddy current sensor 30 is fixed at a predetermined angle (by fixing the screw 3 to the screw case 22 (FIG. 1) so that the lower side of the jig 3 is horizontal (parallel to the installation surface). It can be easily mounted at an angle r). In the present specification, as shown in FIG. 4, the coil 10 fixed to the jig 3 may be simply referred to as “coil”.

  The frequency of the alternating current flowing through the coil 10 of the eddy current sensor 30 is usually 1 to 5 kHz, but preferably 2 to 3 kHz. If the frequency of the alternating current flowing through the coil 10 is within the above range, a change in eddy current can be detected with high sensitivity.

  Usually, a change in eddy current is taken out from the eddy current sensor 30 as a change in voltage. As shown in FIG. 1, a signal (voltage change) taken out from the eddy current sensor 30 attached to the outer peripheral surface of the screw case 22 is transmitted by an eddy current flaw detector (measuring means) 11 connected to the eddy current sensor 30. The distance between the screw 23 and the inner surface of the screw case 22 is measured. This result is displayed by an oscilloscope (display means) 12 connected to the eddy current flaw detector 11. The eddy current flaw detector 11 and the oscilloscope 12 are not particularly limited, and those usually used can be used.

  However, the magnitude of the signal (the amount of change in voltage) taken out from the eddy current sensor 30 differs depending on the thickness of the blades of the screw 23 crossing the magnetic flux 6 (FIG. 3) generated from the coil 10. Specifically, the greater the thickness of the blade of the screw 23, the greater the amount of change in the voltage extracted from the eddy current sensor 30. For this reason, for the screw 23 having a predetermined blade thickness, the relationship between the distance between the screw 23 and the inner surface of the screw case 22 and the voltage taken out from the eddy current sensor 30 needs to be measured (obtained) in advance. There is.

  Thus, for the screw 23 having a predetermined blade thickness, by knowing in advance the relationship between the interval and the voltage, the amount of change in voltage can be corrected based on the relationship. The distance between the screw 23 and the inner surface of the screw case 22 can be accurately measured. Therefore, it is possible to more reliably detect an abnormality in which the distance between the screw 23 of the screw feeder 200 and the inner surface of the screw case 22 is narrowed.

  Thus, by monitoring the change in voltage corresponding to the distance between the inner surfaces of the screw 23 and the screw case 22 using the eddy current sensor 30, the distance between the screw 23 and the inner surface of the screw case 22 in the screw feeder 200 can be reduced. A narrowing abnormality can be easily detected, and the abnormality can be dealt with early.

[2. Abnormality detection device)
The abnormality detection apparatus according to the present invention is an apparatus for detecting an abnormality in which the distance between the screw of the screw feeder and the inner surface of the screw case is narrowed. Specifically, the abnormality detection device according to the present invention is a pair of screws attached to the outer peripheral surface of the screw case such that the central axis of the coil of the eddy current sensor is twisted or parallel to the rotation axis of the screw. Current supply means for supplying current so that current directions of the first coil and the second coil are different from each other, and an eddy current induced by the eddy current sensor From this change, a measuring means for measuring the distance between the screw and the inner surface of the screw case is provided.

  Here, an example of the arrangement of the “eddy current sensor having a pair of coils” will be described with reference to FIG. FIG. 7 is a front view schematically showing the arrangement of the eddy current sensor 30 having the pair of coils 10. As shown in FIG. 7, an eddy current sensor 30 having a pair of coils 10 is configured by the first coil 10 a and the second coil 10 b. Each coil 10 may be fixed to the jig 3. From the viewpoint of improving the sensitivity of the eddy current sensor 30, the eddy current sensor 30 having the pair of coils 10 is preferably disposed on the outer peripheral surface of the screw case 22 so that the central axes of the coils 10 are parallel to each other. . The coil 10 and the jig 3 are the same as those described in the section “1. Abnormality detection method” above, and are omitted here.

  The current supply means in the abnormality detection device according to the present invention is not particularly limited as long as the first coil 10a and the second coil 10b can supply currents in different directions. Since the current is supplied by the current supply means so that the directions of the currents are different between the first coil 10a and the second coil 10b, a change in eddy current induced by a pair of eddy current sensors (voltage change) ) Can be detected as both plus and minus shake signals.

  From the viewpoint of improving the sensitivity of the eddy current sensor having the pair of coils, the current supply means preferably supplies an alternating current having a frequency of 1 kHz to 5 kHz. The current supply means is usually provided in an eddy current flaw detector.

  As the measuring means in the abnormality detecting apparatus according to the present invention, any means can be used as long as the distance between the screw 23 and the inner surface of the screw case 22 can be measured from a change in eddy current induced by the eddy current sensor. It is not limited. For example, a normal eddy current flaw detector or the like can be used. The specific method for measuring the distance between the screw 23 and the inner surface of the screw case 22 from the change in eddy current is as described in the section “1.

  The abnormality detection apparatus according to the present invention may further include display means for displaying the result measured by the measurement means.

  The display means is not particularly limited as long as it displays the results measured by the measurement means. For example, an oscilloscope (recorder), a monitor of an eddy current flaw detector, or the like can be used.

  The abnormality detection apparatus according to the present invention includes, in addition to the above-described means, an amplification means for amplifying the signal output from the eddy current sensor, an alarm means for issuing an alarm when an abnormality is detected, and stopping the operation of the screw feeder when an abnormality is detected. There may be provided stop means or the like. The amplification means can be provided, for example, between the eddy current sensor and the measurement means.

  In the abnormality detection apparatus according to the present invention, for example, for a screw having a predetermined blade thickness, the relationship between the distance between the screw and the inner surface of the screw case and the voltage extracted from the eddy current sensor is measured (understood) in advance. A predetermined voltage (safety reference value) set in advance is set as a threshold, and when a voltage exceeding this threshold is detected, the distance between the screw and the inner surface of the screw case is closer than the predetermined distance. It is also possible to design the system so as to issue an alarm based on the judgment, or to stop the operation of the screw feeder by interlocking the measuring means and the screw feeder. Thereby, it is possible to respond early to an abnormality in which the distance between the screw and the inner surface of the screw case in the screw feeder is narrowed.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[Experimental Example 1]
(1. Screw feeder mock-up equipment)
In the example, the performance test of the eddy current sensor was performed using the following screw feeder mockup.
・ Screw feeder mockup body (manufactured by Nice):
(Screw case)
Material: SUS304
Outer diameter: 114.3mm
Thickness: 4mm
(screw)
Material: SUS304
Outer diameter: 96mm
Blade thickness: 3mm
Spacing between blades (pitch): 90 mm
The distance between the screw and the inner surface of the screw case: 6mm (± 5mm slide adjustment is possible)
Photoelectric sensor: FS-V31 FU-67V (manufactured by Keyence Corporation)
・ Rotation speedometer: RX-22 (manufactured by Keyence Corporation)
・ Inverter: FE100 (made by Oriental Motor)
Eddy current flaw detector: MiniPhase (manufactured by GE Inspection Technologies)
・ Recorder: HIOKI 8846 MEMORY HICORDER (manufactured by Hioki)
The current supply means is not particularly described here because it is built in the eddy current flaw detector. As the display means, a recorder (manufactured by Hioki Co., Ltd.) was used because recording and display display are possible. The photoelectric sensor was attached to optically measure the rotational speed of the screw.

(2. Production of eddy current sensor)
A method for manufacturing the eddy current sensor used in the examples will be described below. As a coil of the eddy current sensor, an element wire made of enameled wire having a diameter of 0.12 mm was wound around the shaft of the bobbin 320 times to produce three types of square coils having a coil diameter of 10 mm, 15 mm, and 20 mm. The lengths t of the three types of prepared square coils were all 5 mm. As the bobbin, S15C was processed into a bobbin shape and then annealed (900 ° C., maintained for 0.5 h, furnace cooled).

  For the three types of square coils that were produced, the angle r shown in FIG. 4 was set to 24 ° so that the blade inclination (24 °) and the central axis of the coil in the screw feeder mockup screw were perpendicular to each other. And fixed to the jig 3. The contact surface of the jig 3 with the screw case was R57.15. Thus, an eddy current sensor having a pair of square coils fixed to the jig was produced.

(3. Performance test of eddy current sensor)
The mounting position of the eddy current sensor will be described with reference to FIG. FIG. 5 shows a configuration of a mock-up 300 of a screw feeder (hereinafter simply referred to as “mock-up 300”) used in the embodiment of the present invention, and a position where the eddy current sensor 30 is attached to the screw feeder of the mock-up 300. FIG. “H” in FIG. 5 represents the distance from the upper end of the mockup 300 to the center of the coil 10 of the eddy current sensor 30.

  In this embodiment, an eddy current sensor having a pair of coils is attached to the outer peripheral surface of the screw case of the mockup 300 so that the central axis of the coil of the eddy current sensor is in a twisted position with respect to the rotation axis of the screw. It was. In addition, the first coil and the second coil were supplied with currents so that the directions of the currents were different from each other. Furthermore, the first coil and the second coil were attached so that the central axes of the coils were parallel to each other and close to each other. The attachment position of the eddy current sensor having the pair of coils was set to a position where the distance H from the upper end of the mockup 300 to the center of each coil of the eddy current sensor was about 125 mm.

  And the eddy current sensor which has the said pair of coil was connected to the eddy current flaw detector. FIG. 8 is a block diagram showing the arrangement of the eddy current sensor 30 having a pair of coils and the eddy current flaw detector 11. As shown in FIG. 8, the eddy current flaw detector 11 has a built-in bridge circuit, and the eddy current sensor 30 having the first coil 10a and the second coil 10b is connected using the bridge circuit. Internal resistances 41 a and 41 b are connected to the bridge circuit built in the eddy current flaw detector 11. When the impedance of either the first coil 10a or the second coil 10b changes and the balance of the bridge is lost, a signal is output to the detector 43. Further, an amplifier 42 that is an amplifying unit for amplifying the signal and an oscillator 40 that is a current supplying unit for supplying an alternating current to the eddy current sensor 30 are connected to the bridge circuit.

  In this embodiment, the eddy current detection method is a self-induction type, and the usage method is a self-comparison method. Specifically, the self-induction type is a method in which excitation and detection are performed by the same coil, and the self-comparison method is a method in which changes in voltage are compared at different parts of the object to be inspected.

  The sensitivity of the eddy current flaw detector was 60 dB, and the phase angle in the detection signal of the screw blade was 90 °. Further, a low-pass filter 25 Hz of an eddy current flaw detector was used to cut high frequency noise such as electromagnetic noise. The low-pass filter is built in the eddy current flaw detector.

  The number of rotations of the screw in the mock-up 300 was 150 rpm, and an alternating current having a frequency in the range of 1 kHz to 5 kHz was supplied to each of the produced eddy current sensors, and data was collected every 1 kHz. The results are shown in FIG.

  FIG. 6 is a graph showing the voltage change of the eddy current sensor in the mock-up 300 of the screw feeder obtained in the embodiment of the present invention, and (a) is an eddy current sensor having a pair of square coils with a diameter of 10 mm. (B) shows the result of the eddy current sensor having a pair of square coils with a diameter of 15 mm, and (c) shows the result of the eddy current sensor having a pair of square coils with a diameter of 20 mm. As shown in FIG. 6, in all eddy current sensors, it was confirmed that the voltage change (Y amplitude value (V)) with respect to time (s) was obtained as a double shake signal.

  The eddy current sensor having a pair of 10 mm diameter square coils and the pair of eddy current sensors having a 15 mm diameter square coils can obtain the maximum amplitude value at 3 kHz, and the eddy current having a pair of 20 mm diameter square coils. In the current sensor, the maximum amplitude value was obtained at 2 kHz.

  When comparing the amplitude value of each eddy current sensor at the frequency at which the maximum amplitude value was obtained, the sensitivity of the eddy current sensor having a pair of square coils with a diameter of 20 mm was relatively high, but the difference was about 2 dB. There was no significant difference in sensitivity. The influence of the size of the coil hardly appears on the sensitivity because the coil and screw case of the eddy current sensor are in contact with each other on a curved surface, and the range that can be detected by the eddy current sensor is limited. It is done.

  According to this study, the eddy current sensor is mounted on the screw case so that the central axis of the coil of the eddy current sensor is in a twisted or parallel position with respect to the rotational axis of the screw, and more preferably in a twisted position. It was found that the detection signal of the screw blade can be detected as one peak by attaching to the outer peripheral surface. In addition, by attaching an eddy current sensor having a pair of coils in which the directions of currents are different from each other, the detection signal can be easily detected as a double shake signal. And even if the size of the square coil is different, there is no significant difference in sensitivity. Therefore, if an eddy current sensor having a pair of coils with a diameter of about 10 mm is used, the distance between the screw and the inner surface of the screw case is reduced. It was found that the abnormality can be detected sufficiently.

  According to the method of the present invention, the abnormality of the screw feeder can be detected easily and reliably. Therefore, the abnormality detection method according to the present invention can be suitably used in various industries using a screw feeder.

7 Eddy current 10 Coil 10a First coil 10b Second coil 11 Eddy current flaw detector (measuring means)
22 Screw case 23 Screw 30 Eddy current sensor 200 Screw feeder

Claims (8)

A method for detecting an abnormality distance between the screw and the screw casing of the inner surface of the scan clew feeder is narrowed,
The eddy current sensor having a pair of coils is attached to the outer peripheral surface of the screw case so that the central axis of the coil of the eddy current sensor is twisted or parallel to the rotational axis of the screw,
The first coil and the second coil have different current directions ,
An abnormality detection method, comprising: measuring a distance between the screw and an inner surface of the screw case from a change in eddy current induced by the eddy current sensor .   The abnormality detection method according to claim 1, wherein the eddy current sensor is arranged so that central axes of the pair of coils are parallel to each other.   3. The abnormality detection method according to claim 1, wherein the eddy current sensor is attached so that a blade inclination in the screw is perpendicular to a central axis of the pair of coils of the eddy current sensor.   The abnormality detection method according to any one of claims 1 to 3, wherein an alternating current having a frequency of 1 kHz to 5 kHz is passed through the eddy current sensor. An apparatus for detecting an abnormality in which the distance between the screw of the screw feeder and the inner surface of the screw case is narrowed,
An eddy current sensor having a pair of coils attached to the outer peripheral surface of the screw case so that the central axis of the coil of the eddy current sensor is twisted or parallel to the rotational axis of the screw;
Current supply means for supplying current so that current directions of the first coil and the second coil are different from each other;
An abnormality detection device comprising: a measuring means for measuring a distance between the screw and the inner surface of the screw case from a change in eddy current induced by the eddy current sensor.   6. The abnormality detection device according to claim 5, wherein the current supply means supplies an alternating current having a frequency of 1 kHz to 5 kHz.   The abnormality detection device according to claim 5, wherein the eddy current sensor is disposed on an outer peripheral surface of the screw case so that central axes of the pair of coils are parallel to each other. The abnormality detection device according to claim 5, further comprising display means for displaying a result measured by the measurement means.

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