JP2009054517A - Long-distance operation proximity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a guided proximity sensor capable of performing a long-distance operation in a conventional shape, and a proximity sensor with high detection accuracy capable of performing a longer-distance operation. <P>SOLUTION: In the proximity sensor, a magnetic plated wire coil 5 is adopted on a sensor head section 3, an arithmetic and processing section 11 where at least smoothing and deduction logic software of detection data is installed is formed as a structural element. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a long-distance operation proximity sensor having a long operation distance, and more particularly to an improvement of the excitation and detection sensor head. This sensor head excites the detected object at high frequency without contact, and detects the impedance change and resonance status due to the eddy current generated in the detected object, thereby detecting the position, distance, speed, vibration of the detected object. And detecting the material. Note that the proximity sensor in this specification can also be referred to as a proximity switch.

There is an increasing demand for an inductive / long-distance operating proximity sensor for the purpose of increasing the operating distance, improving the flexibility of proximity sensor installation, and preventing contact and damage during detection operations. The operating distance or stable detection distance of the proximity sensor is standardized by JIS, and the long distance is specified by JIS standard (JIS C 8201-5-2 (IEC 60497). Coil housing and detection circuit A technique for increasing the distance by the above method is disclosed in Patent Document 1 and Patent Document 2.
US 4509023 JP 2006-156360 A

  Techniques for increasing the detection distance of the inductive proximity sensor include increasing the Q (quality factor) of the excitation and detection coils, increasing the inductance, reducing the proximity effect, and expanding the working distance of the magnetic flux. Coil shape, coil housing, magnetic flux enhancement by using magnetic flux induction film, improvement of signal-to-noise ratio of detection unit, temperature compensation of detection coil, etc. have been extended, but the detection distance to coil diameter ratio is reliable and stable However, it is difficult to maintain the ratio to 0.5 or more without increasing the shape.

  The problem to be solved by the present invention is to make the detection distance to coil diameter ratio 0.5 to 1.0 longer while maintaining reliability and stability.

  (1) The proximity sensor according to the first aspect of the present invention is characterized in that a magnetic plated wire coil is used as the excitation / detection coil or the dedicated excitation coil of the sensor head.

  By using a magnetic plated wire coil for the excitation / detection coil or dedicated excitation coil for long-distance operation proximity sensors, the reliability and stability of the detection distance to coil diameter ratio are maintained, and the shape is not increased. In addition, it is possible to increase the distance by 0.5 or more.

  (2) In the proximity sensor according to the second aspect of the present invention, the excitation / detection coil or the excitation coil of the sensor head is composed of a magnetically plated single wire or a litz wire and an air core or a multilayer wound solenoid coil on the core. It is characterized by this.

  If the detection signal-to-noise ratio is to be improved, a reference coil unit is provided, and if the coil is empty, an amplifier unit is provided with a magnetic shield unit that prevents magnetic flux leakage from the sensor head and, if necessary, an operating light communication unit. Is preferred.

  (3) In the proximity sensor according to the present invention according to claim 3, the excitation coil and the detection coil of the sensor head are composed of independent multi-layer wound solenoid coils on the air core or on the core with magnetically plated single wires or litz wires. It is characterized by being.

  This magnetic plated wire is preferably a single wire or a litz wire, and the multi-layer wound solenoid coil has a single dedicated coil configuration wound around a core or air core with good high-frequency characteristics, and forms a dedicated coil for excitation and a dedicated detection coil, respectively. .

  (4) The proximity sensor according to the present invention according to claim 4 is a high-frequency temperature coefficient of the coil depending on the winding shape such as the Q improvement effect by the magnetic plating of the excitation / detection coil or the dedicated excitation coil of the sensor head and the coil diameter versus pitch interval. This is characterized in that the detection accuracy is improved by reducing. In other words, in the present invention, excitation and detection are formed by separate magnetic plated wire coils to improve detection accuracy and sensitivity.

  A preferred form in this case is a configuration in which three detection coils are arranged in an equilateral triangle shape to form a two-dimensional proximity sensor that detects a planar distribution of eddy currents.

  As a preferred form in this case, the temperature coefficient of the high-frequency excitation coil is a function of the coil DC resistance and the skin effect loss and the proximity effect loss, and the magnetic plated wire coil has the skin effect loss and the proximity effect loss as a copper wire without magnetic plating. The temperature coefficient is reduced by the plating wire diameter of the magnetic plating wire coil and the overall length, shape, pitch, etc. of the magnetic plating wire coil.

  (5) A proximity sensor according to the present invention according to claim 5 is a magnetic sensor that receives a magnetic plated wire or a copper wire having an inductance equivalent to that of an excitation / detection coil using a magnetic plated wire of a sensor head from a detected object as a reference coil. It is a sensor head configuration that enables differential detection of the induced current and impedance of both coils by exciting both coils under the same excitation conditions by additionally arranging them at locations where influence is low It is what.

  In this aspect, the eddy current generated in the conductor detection object has little influence on the detection coil of the magnetic field and heat generation, and other high-temperature environments have the same value of inductance and DC resistance as the magnetic plated wire coil in the same environment. It is possible to improve the detection accuracy by installing a reference coil, causing the same exciting current to flow, detecting the induced current and the impedance, and calculating the difference with those of the detection coil of the proximity sensor.

  (6) The proximity sensor according to the present invention according to claim 6 has a sensor head configuration including an excitation unit using a magnetic plated wire coil and a detection unit made of GMR (Giant Magneto Resistive Sensor). It is what.

  In this aspect, it is possible to detect magnetic flux with high accuracy by using one or a plurality of giant magnetoresistive sensors as compared with impedance change detection by a detection coil using the eddy current of a high-frequency excited detection object. In this case, the high-frequency excitation current is not a continuous rectangular wave or sine wave, but a pulse current with a no-current period, and the magnetic flux change during this no-current period is detected by a giant magnetoresistive sensor to further improve the detection accuracy Is also included.

  (7) A proximity sensor according to a seventh aspect of the present invention includes a circuit that estimates a detection output of a magnetic plated wire coil based on smoothing control and FUMI (Function of Mutual Information) theory. In this aspect of the present invention, mathematical means is used to reduce detection noise caused by fluctuations in the speed of detected objects, fluctuations in heat generation, and fluctuations in the excitation coil and detection environment using inference and statistical theory. White noise with a high frequency of excitation high frequency or higher is a smoothing software such as moving average and smoothing, noise due to Markov process gradual fluctuations such as the speed, vibration, heat generation etc. of the detected object is detected as standard deviation of fluctuation noise The standard deviation can be reduced.

  According to the first aspect of the present invention, the detection distance to coil diameter ratio can be increased by 0.5 to 1.0 while maintaining reliability and stability.

  According to the second and third aspects of the present invention, the distance is longer than the proximity sensor according to the first aspect of the present invention using the copper wire coil due to the increase in the inductance of the coil by Fe (iron) thin film plating, the reduction of the proximity effect, and the long-range effect of the magnetic flux. Operation becomes possible. This long-distance operation can be further extended by using a core or air-core coil with good high-frequency characteristics.

  In the present invention according to claim 4, the proximity effect is adjusted by the coil winding shape and the single wire or litz wire of the wire, the temperature coefficient of the entire excitation / detection coil is reduced, and the distance can be increased and the detection accuracy can be improved. .

  In the present invention according to claim 5, a reference coil having the same inductance and DC resistance is placed outside the excitation / detection coil in a place where the effect of the eddy current of the detected object is not present, thereby improving detection accuracy and enabling a long distance. Can do.

  In the present invention according to claim 6, it is possible to increase the detection sensitivity and improve the detection accuracy by using a high-sensitivity detection sensor using a giant magnetoresistance (GMR) or the like of the spintronics magnetic sensor element, thereby enabling a long distance. .

  In the present invention according to claim 7, smoothing of the detection output and inference logic such as the FUMI theory can be realized by the software of the CPU of the proximity sensor configuration, so that the detection accuracy can be improved and a long distance is possible.

  Hereinafter, a proximity sensor according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a block configuration example of a proximity sensor using a magnetic plated wire coil according to an embodiment of the present invention. Referring to FIG. 1, reference numeral 1 denotes a conductive detection object that moves up and down or in the left-right direction.

  Reference numeral 3 denotes a sensor head unit. The sensor head unit 3 includes a core disposed in a non-contact manner on the detected object 1 or a magnetic plated wire coil 5 wound around the air core, a resistor, a diode, and other temperature correction circuit units (not shown). Consists of.

  Reference numeral 9 denotes a detection operation circuit unit. The detection operation circuit unit 9 oscillates or supplies an excitation high-frequency current to the magnetic plating wire coil 5, and simultaneously detects an impedance variation of the magnetic plating wire coil 5. A circuit unit, a circuit unit for correction, and the like are included.

  Reference numeral 11 denotes an arithmetic / processing unit. The arithmetic / processing unit 11 includes a circuit including a CPU, and is responsible for software control such as oscillation control, high-precision detection algorithm, and operation display.

  13 is an operation display unit composed of a circuit for displaying the operation state of the proximity sensor, 15 is an operation light communication unit composed of a modulation circuit for optically communicating the operation state of the proximity sensor, and 17 is a detection output of the proximity sensor. A detection output unit 19 for output, a serial communication unit 19 including a USB connector connected to an external personal computer or PLC (programmable controller) 21 for serial communication, and 23 driven by the operation display unit 13 to emit light in a manner indicating an operation state. The operation display light emitting diode 25 is a light emitting diode for operation light communication that is driven by the operation light communication unit 15 to emit light.

  Detection data is output from each of the detection output unit 17 and the operating light communication unit 15. The detection output unit 17 and the operating light communication unit 15 can be made bidirectional communication to perform feedback control for detection data reliability and safety control.

  Reference numeral 27 denotes a magnetic shield made of a magnetic thin film or the like that reduces the magnetic flux in the direction opposite to the detected object in the case of an air-core coil. The magnetic shield 17 has a magnetic flux generated when the magnetic-plated wire coil 5 is air-core. Do not affect the circuit.

  Reference numeral 28 denotes a coaxial cable for connecting the sensor head unit 3 and the amplifier unit on the rear stage side in the case of the amplifier separation type.

  Reference numeral 29 is a reference coil, and this reference coil 29 has an inductance equivalent to that of the magnetic plated wire coil 5 in order to reduce the influence of eddy current generated in the detected object 1 and vibration of the detected object 1 as indicated by []. And has direct current resistance. The reference coil 29 is additionally installed at a place where the magnetic influence of the detected object 1 is small, and the detection accuracy of the proximity sensor is increased to enable a long distance operation.

  The reference coil 29 can be composed of a magnetic plated wire or a copper wire. The reference coil 29 is excited under the same excitation conditions as the magnetic plating wire coil 5, thereby detecting a difference between the induced currents and impedances of the coils 5 and 29, and using this difference detection to improve detection accuracy and to operate over a long distance. Can be made possible.

  FIGS. 2A and 2B show a configuration example of the magnetic plated wire coil 5.

  The magnetic plated wire coil 5 shown in FIG. 2A is configured by forming a ferromagnetic layer 5b on the surface of a copper wire 5a that is a coil material. The ferromagnetic layer 5b is a plating layer such as an Fe thin film having a thickness of about 1 μm.

  The magnetic plated wire coil 5 shown in FIG. 2 (b) is formed with a ferromagnetic layer 5b on the surface of the copper wire 5a as in FIG. 2 (a), and with rust prevention and soldering on the surface of the ferromagnetic layer 5b. After forming a thin film additional layer 5c such as Ni (nickel) having a minimum necessary thickness for facilitating the process, an insulating layer 5d using polyamide or polyurethane resin is further formed on the surface of the thin film additional layer 5c. Composed.

  In the magnetic plated wire coil 5 of FIGS. 2 (a) and 2 (b), magnetic energy can be stored by the ferromagnetic layer 5b, and the inductance can be increased, the proximity effect can be reduced, and the magnetic shield effect can be actively utilized for the long distance operation. .

  3A and 3B show a configuration example of the sensor head unit 3. FIG.

  FIG. 3A shows a sensor head unit 3 formed of a single coil that is used for both excitation and detection. In FIG. 3A, (a-1) shows a front configuration of the sensor head unit 3, and (a-2) shows a side sectional configuration. FIG. 3A also shows the detected object 1.

  FIG. 3B shows a sensor head unit 3 including one excitation coil 3a located at the center and three detection coils 3b arranged in the surrounding filling resin 3c. The detection coil 3a is also filled with resin. In FIG.3 (b), the front structure of the sensor head part 3 is shown to (b-1), and a side surface cross-section structure is shown to (b-2). In the sensor head unit 3 of FIG. 3B, the excitation coil 3a and the three detection coils 3b are all magnetic plated wire coils, and the detection coil 3b is arranged in an equilateral triangle with respect to the excitation coil 3a. Thus, it is a form that enables two-dimensional detection with high sensitivity and high reliability. In this case, there is a form in which the detection coil 3b does not use a magnetic plating wire.

  FIG. 4A shows an equivalent circuit at a high frequency of the magnetic plated wire coil 5 which is also used for excitation and detection, and FIG. 4B shows a winding shape of the multilayer solenoid coil. In FIG. 4A, R (X) is copper loss + proximity effect loss, and L (X) is inductance. In FIG. 4B, p is the coil pitch, d is the diameter of the coil material, r is the coil diameter, and L is the coil length.

  The temperature coefficient of the magnetic plated wire coil 5 is greatly influenced by the copper loss and the proximity effect loss which are R (X) in FIG. The copper loss, that is, the direct current resistance is the resistance of the copper wire forming the coil, and is independent of the geometric shape of the magnetic plated wire coil 5. Proximity effect loss can be reduced by increasing the coil pitch or reducing the copper wire diameter relative to the coil pitch. That is, because of the winding shape, the high frequency temperature coefficient of the entire coil can be reduced and the detection accuracy can be increased by the excitation frequency, the thickness of the magnetic plated wire coil 5, and the winding shape of the coil.

  The multilayer wound solenoid coil shown in FIG. 4 (b) constitutes an excitation / detection coil or excitation coil of the sensor head unit 3, and is a dedicated multilayer winding individually independent on the air core or core with a magnetically plated single wire or litz wire. It has a solenoid coil configuration. The high frequency temperature coefficient can be reduced and the detection accuracy can be increased by the effect of improving the Q value by the magnetic plating wire of the multilayer wound solenoid coil and the winding shape such as the coil diameter r and the pitch interval p.

  FIG. 5 shows a configuration of a sensor head unit 3 including one or a plurality of spintronics magnetic sensor elements 31 such as a high-sensitivity giant magnetoresistive element as a detection unit. In the sensor head unit 3, the magnetic plated wire coil 5 is specialized for excitation of the detection object 1, thereby increasing detection sensitivity and enabling long-distance operation. The spintronics magnetic sensor element 31 can constitute a high-function detector 33 as indicated by an arrow a1.

  The oscillation circuit unit 35 is intermittently oscillated with a pulse waveform or the like, and as shown by an arrow a2, the sensor head unit 3 can detect a magnetic flux in the absence of an excitation current, thereby enabling detection with higher sensitivity and reliability. The synchronization signal from the oscillation circuit unit 35 is used for detection by the high function detection unit 33 as indicated by an arrow a3. The oscillation circuit unit 35 is connected to the CPU bus a7 as indicated by the arrow a4, and is connected to the CPU that is the arithmetic / processing unit 11 through the bus a6, while the high function detection unit 33 is connected to the CPU bus a7 as indicated by the arrow a5. Connect to the arithmetic / processing unit 11 through the bus a6.

  6 (a) and 6 (b) show a correction image of the long-distance motion detection software (firmware) of the arithmetic / processing unit 11 of FIG. 1 for carrying out the present invention, and FIG. 7 shows a detection accuracy improvement flowchart. .

  In FIG. 6A, when the horizontal axis is the distance and the vertical axis is the detection value, and the material of the detection object 1 is iron, aluminum, and stainless steel, the generation of eddy currents and the temperature on the detection object 1 due to each material. It is an image of the difference of the detection value by a raise. When the material is iron, the detection characteristics are as indicated by the alternate long and short dash line b1, when aluminum is indicated by the dotted line b2, and when stainless steel is indicated by the solid line b3. Correct for characteristics. FIG. 6A shows detection characteristics after correction with a double line.

  FIG. 6B is a diagram showing correction for reducing the hysteresis (hysteresis) due to the approach and retreat (up / down / left / right) between the detected object and the sensor head by a prior parameter or correction software. In FIG. 6B, the horizontal axis represents the approach distance between the detected object and the sensor head, and the vertical axis represents the detected magnetic flux. c1 is a hysteresis curve, c2 and c3 are hysteresis before correction, and c4 and c5 are hysteresis after correction. c2 is corrected from left to right in the drawing at c4, and c3 is corrected from right to left in the drawing at c5. Magnetic flux change due to approach and retreat (up / down / left / right) due to the hysteresis characteristic of the detected object 1 is reduced to the corrected hysteresis shown by c4 and c5 by the correction software.

  FIG. 7 is a schematic flowchart of software using the FUMI (Function of Mutual Information) theory. As shown in this flowchart, the standard deviation of the detection value S of the detection signal of the impedance displacement of the coil due to the eddy current is SD / S. Next, white noise due to oscillation and eddy current heat generation is processed by smoothing software. Next, the noise due to the movement of the detected object is a moderate noise (Markov process noise) compared to the excitation frequency, and the standard deviation SD / T of the Markov process noise is calculated by the calculation software. Finally, software that improves the detection accuracy by correcting the detection value S with the function SD / T as SD / S in the FUMI theoretical formula is implemented. That is, the detection value S is corrected by using the standard deviation SD / T of Marcos process noise (variation) such as speed fluctuation, vibration fluctuation, temperature fluctuation, etc. of the detected object much slower than the high frequency excitation cycle as the standard deviation SD / S of the detection signal. Is implemented with software using FUMI theory. The above software is installed in the calculation / processing unit 11.

FIG. 1 is a configuration diagram of a magnetic plated wire coil proximity sensor. FIG. 2 is a magnetic plating wire configuration diagram. FIG. 3 is a diagram showing a coil configuration in which the excitation coil and the detection coil are independent. FIG. 4 is a diagram showing an excitation / detection coil (inductance) and R (loss). FIG. 5 is a configuration diagram in which a spintronic magnetic sensor element is used as a detection unit. FIG. 6 is a diagram showing detection characteristics and correction examples. FIG. 7 is a schematic flowchart of a detection accuracy improvement algorithm (FUMI theory).

Explanation of symbols

1 Detected object 3 Sensor head 5 Magnetic plated wire coil

Claims (7)

  A proximity sensor characterized in that a magnetic plated wire coil is used for the excitation / detection coil or the excitation coil of the sensor head.   A proximity sensor, wherein the excitation / detection coil or the dedicated excitation coil of the sensor head is composed of a magnetically plated single wire or litz wire, or an air core or a multilayer wound solenoid coil on a core.   A proximity sensor, wherein an excitation coil and a detection coil of a sensor head are each composed of a magnetic multilayer-plated single coil or a litz wire, each of which is an independent multi-layer wound solenoid coil on an air core or a core. A proximity sensor characterized in that the detection accuracy is improved by reducing the high-frequency temperature coefficient of the coil by the effect of magnetic plating of the excitation / detection coil of the sensor head or the dedicated excitation coil and the winding shape such as the coil diameter versus pitch interval.   Both of the above coils can be obtained by arranging a magnetic plated wire or copper wire having the same inductance as the excitation / detection coil using the magnetic plated wire of the sensor head as a reference coil at a location where the magnetic influence from the detected object is low. A proximity sensor having a sensor head configuration capable of detecting a difference between induced currents and impedances of the two coils by exciting them under the same excitation conditions.   A proximity sensor having a sensor head configuration including an excitation unit using a magnetic plated wire coil and a detection unit made of GMR (Giant Magneto Resistive Sensor).   The proximity sensor according to any one of claims 1 to 6, further comprising software for inferring a detection output by a magnetic plated wire coil or GMR by FUMI (Function of Mutual Information) theory and smoothing control. .

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