JP2014185986A - Proximity sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proximity sensor system capable of preventing false detection of a detected body.SOLUTION: A proximity sensor system 100 includes: a sensor unit 10 including an oscillation circuit which forms a magnetic field at a predetermined oscillatory frequency; and a detected unit 50 which is provided to a detected body A and which includes a resonance circuit generating a resonance frequency based on the predetermined oscillatory frequency. The sensor unit 10 also includes a detection circuit 30 which detects the proximity of the detected body A when the oscillation of the oscillation circuit is changed by the resonance circuit.

Description

  Some embodiments according to the present invention relate to, for example, a high-frequency oscillation type proximity sensor system.

  Conventionally, as a proximity sensor of this type, in a proximity switch including a detection signal processing printed circuit board housed along the longitudinal direction of the case, a display element for displaying the operation state of the switch is provided on one side of the printed circuit board. What was provided is known (for example, refer patent document 1). According to this proximity switch, the display element is not mounted in the substantially central portion in the width direction of the printed circuit board, but is mounted on one side in the width direction of the circuit board, so that the discrete LED is not mounted on the printed circuit board. The lighting of the display element can be easily confirmed from the outside of the switch.

JP 11-31446 A

  By the way, in the conventional proximity sensor, the detection coil is driven to oscillate to form a magnetic field. When the detected object approaches, an eddy current due to electromagnetic induction flows to the detected object that is a magnetic material. Based on the above, the proximity (presence / absence) of the detected object was detected.

  However, when a magnetic body other than the detection target exists, the magnetic flux formed by the detection coil may act on the magnetic body, resulting in eddy current loss. For this reason, the conventional proximity sensor may erroneously detect the magnetic body as the proximity of the detected body when eddy current loss occurs due to the magnetic body other than the detected body.

  Some aspects of the present invention have been made in view of the above-described problems, and an object thereof is to provide a proximity sensor system capable of preventing erroneous detection of a detection target.

  A proximity sensor system according to the present invention includes a sensor unit that includes an oscillation circuit unit that forms a magnetic field at a predetermined oscillation frequency, and a resonance circuit unit that is provided on the detection target and has a resonance frequency based on the predetermined oscillation frequency. The sensor unit further includes a detection circuit unit that detects the proximity of the detected object when the oscillation of the oscillation circuit unit is changed by the resonance circuit unit.

  According to this configuration, the sensor unit 10 including the oscillation circuit unit that forms a magnetic field at a predetermined oscillation frequency and the detected unit including the resonance circuit unit having a resonance frequency based on the predetermined oscillation frequency of the sensor unit are provided. Here, since the oscillation circuit unit forms a magnetic field at a predetermined oscillation frequency and the resonance circuit unit has a resonance frequency based on the predetermined oscillation frequency, the resonance circuit unit resonates. In the resonant circuit unit that resonates, a large voltage is generated due to a change in the magnetic field (or magnetic flux of the magnetic field) compared to a case where the resonance circuit unit does not resonate (non-resonant). The electric power (energy) consumed by the resonance circuit unit gives energy loss to the oscillation circuit unit. Therefore, when the sensor unit and the detected object are close to each other, a large energy loss is given to the oscillation circuit unit as compared with a magnetic body or the like due to a change in the magnetic field (or magnetic flux of the magnetic field). At this time, the oscillation circuit unit changes its oscillation (vibration state), for example, the oscillation is attenuated or the oscillation operation is stopped, so that the detection circuit unit can detect the proximity of the detected object.

  Further, in the proximity sensor system, the resonance circuit unit of the detection unit provided in the detection object gives energy loss to the oscillation circuit unit of the sensor unit, and uses the change in oscillation of the oscillation circuit unit due to the energy loss, Since the proximity of the detected object is detected, the vibration of the oscillation circuit unit can be changed even if the detected object is a non-magnetic material, and it is possible to detect the non-magnetic material. Also, the detection distance depends on the type of the detected object because the resonance circuit part of the detected unit provided on the detected object gives energy loss due to the change of the magnetic field (magnetic flux of the magnetic field). No (detection distance does not change depending on the type of detection object) Furthermore, by using the resonance circuit portion of the detected unit provided on the detected object, compared to the case of using electromagnetic induction action or eddy current loss due to electromagnetic induction action as in the case of a conventional proximity sensor, The advantage (merit) that it is difficult to be affected by the size of the detection body, the shape of the detection surface, and the like can be obtained.

  Furthermore, the detection circuit unit detects the proximity of the detected object when the oscillation of the oscillation circuit unit is changed by the resonance circuit unit. As a result, even if some magnetic material exists between the sensor unit and the detected object and eddy current loss occurs due to electromagnetic induction, the eddy current loss is compared with the energy loss given by the resonance circuit unit. Since it is very small, the detection circuit unit does not detect the magnetic body as the proximity of the detected body.

  Preferably, the detection circuit unit detects the proximity of the detection target based on a predetermined evaluation value of the oscillation circuit unit.

  According to this configuration, the detection circuit unit detects the proximity of the detection target based on the predetermined evaluation value of the oscillation circuit unit. Here, when the sensor unit and the object to be detected approach and the resonance circuit unit gives energy loss to the oscillation circuit unit, a predetermined evaluation value of the oscillation circuit unit, for example, Q value, oscillation frequency, oscillation amplitude, detection coil The values of the internal resistance, inductance, impedance, and the like greatly change compared to the case where eddy current loss occurs due to electromagnetic induction. Therefore, since the detection circuit unit that detects the proximity of the detection object is based on the predetermined evaluation value of the oscillation circuit unit, the oscillation change of the oscillation circuit unit by the resonance circuit unit can be easily detected. Therefore, when the oscillation of the oscillation circuit unit is changed by the resonance circuit unit, the detection circuit unit that detects the proximity of the detection target can be easily configured (realized).

  Preferably, the predetermined evaluation value is a Q value, and the detection circuit unit detects the proximity of the detected object when the Q value of the oscillation circuit unit is equal to or less than a threshold value, and The threshold value is a value smaller than the Q value of the oscillation circuit unit when the magnetic material contacts the sensor unit.

  According to this configuration, the predetermined evaluation value of the oscillation circuit unit is the Q value, and the detection circuit unit detects the proximity of the detected object when the Q value of the oscillation circuit unit is equal to or less than the threshold value. The threshold value is a value smaller than the value when the magnetic body contacts the sensor unit. As a result, the threshold value is set to a value smaller than the Q value (minimum value) that can be taken when eddy current loss occurs. Therefore, the eddy current loss due to electromagnetic induction and the energy provided by the resonance circuit section It is possible to clearly distinguish (identify) loss. Therefore, erroneous detection of the detection object due to the occurrence of eddy current loss can be reliably prevented.

  Preferably, the resonance circuit unit includes a resistor, a coil, and a capacitor.

  According to such a configuration, the resonance circuit unit includes a resistor, a coil, and a capacitor. Thereby, the resonance frequency of the resonance circuit unit can be calculated using the inductance of the coil and the capacitance of the capacitor. Therefore, by setting the inductance of the coil and the capacitance of the capacitor based on the predetermined oscillation frequency of the oscillation circuit unit, a resonance circuit unit having a resonance frequency based on the predetermined oscillation frequency can be easily configured (realized). Can do.

  Further, while the resistance of the resistor does not affect the resonance frequency, the frequency characteristic of the Q value of the resonance circuit section can be changed by changing the resistance of the resistor. Therefore, by setting the resistance of the resistor in accordance with the usage mode (purpose of use), the frequency characteristic of the Q value of the resonance circuit unit can be set to a desired characteristic without changing the resonance frequency.

  Preferably, the aforementioned resistor is a variable resistor.

  According to this configuration, the resonance circuit unit includes the variable resistor. As a result, when the error of the predetermined oscillation frequency is large, the Q value of the resonance circuit section is widened with a large Q value in a wide frequency band by changing the resistance of the variable resistor to a relatively large value. Therefore, the resonance circuit unit can absorb an error of a predetermined oscillation frequency. Therefore, even when the error of the predetermined oscillation frequency is large, the Q value of the resonance circuit portion of the detected unit can be increased, and the proximity of the detected object can be detected. On the other hand, when the error of the predetermined oscillation frequency is small, by changing the resistance of the variable resistor to a relatively small value, the Q value of the resonant circuit section is narrowed to a large Q value in a narrow frequency band. Frequency characteristics and a large maximum value in the vicinity of the resonance frequency. Therefore, when the oscillation of the oscillation circuit unit is changed by the resonance circuit unit, for example, the Q value of the oscillation circuit unit changes greatly, so that erroneous detection of the detection target can be reliably prevented.

  Preferably, the aforementioned capacitor is a variable capacitor.

  According to this configuration, the resonance circuit unit includes the variable capacitor. Here, since the capacitance of the variable capacitor changes the resonance frequency, changing the capacitance of the variable capacitor shifts the resonance frequency that is the center line (center axis) in the frequency characteristic of the Q value of the resonance circuit ( Move). Therefore, when the error of the predetermined oscillation frequency is positive, the frequency characteristic of the Q value of the resonance circuit unit can be shifted in the positive direction by changing the capacitance of the variable capacitor to a small value. When the error of is negative, the frequency characteristic of the Q value of the resonance circuit unit can be shifted in the negative direction by changing the capacitance of the variable capacitor to a small value. Therefore, when the error of the predetermined oscillation frequency or the actual predetermined oscillation frequency itself is known, the resonance circuit unit of the detected unit can be resonated, and the proximity of the detected object can be easily detected. .

  Preferably, the detected unit includes a non-magnetic housing that houses the resonance circuit unit.

  According to this configuration, the detected unit includes the nonmagnetic housing that houses the resonance circuit unit. Thus, the magnetic flux generated by the oscillation circuit unit can be applied to the resonance circuit unit, and the resonance circuit unit can be protected from the external environment. Therefore, the detected unit can improve the environmental resistance performance such as water resistance, oil resistance, dirt resistance, vibration resistance, shock resistance, heat resistance, cold resistance, etc., and the proximity sensor system is required to be environmental resistance. It can be suitably applied to the use.

  Preferably, the oscillation circuit unit includes a coil and a capacitor.

  According to this configuration, the oscillation circuit unit includes the coil and the capacitor. Here, when a current flows through the coil at a predetermined oscillation frequency, the coil generates a magnetic flux, and forms a magnetic field (magnetic field) between the sensor unit and the detection target. Thus, an oscillation circuit unit that forms a magnetic field at a predetermined oscillation frequency can be easily configured (realized).

  Further, the resonance frequency of the LC oscillation circuit composed of a coil and a capacitor can be calculated using the inductance of the coil and the capacitance of the capacitor. Therefore, by setting the predetermined oscillation frequency of the oscillation circuit unit to be the same as the calculated resonance frequency, the impedance of the LC oscillation circuit can be maximized, and the power consumption of the oscillation circuit unit can be reduced.

  According to the proximity sensor system of the present invention, it is possible to prevent erroneous detection of an object to be detected. In addition, the proximity sensor system can use the sensor unit and the detected unit like a key and a lock (lock), for example, in the security field, because it does not detect even if something other than the detected object comes close. It can be suitably applied.

It is a block diagram explaining schematic structure of a proximity sensor system. It is a circuit diagram explaining an example of the equivalent circuit of an oscillation circuit part. It is a circuit diagram explaining an example of the to-be-detected unit shown in FIG. It is a graph which shows the relationship between the frequency and Q value for every detection distance in the proximity sensor system shown in FIG. It is a graph which shows the relationship between the detection distance and Q value in the proximity sensor system shown in FIG. It is a graph which shows the relationship between the frequency and Q value in the resonant circuit part shown in FIG. It is a circuit diagram explaining the other example of the to-be-detected unit shown in FIG. FIG. 6 is a circuit diagram for explaining still another example of the detected unit shown in FIG. 1. FIG. 6 is a circuit diagram for explaining still another example of the detected unit shown in FIG. 1.

  Embodiments of the present invention will be described below. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions and the like should be determined in light of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings. In the following description, the upper side of the drawing is referred to as “upper”, the lower side as “lower”, the left side as “left”, and the right side as “right”.

  1 to 9 show an embodiment of a proximity sensor system according to the present invention. FIG. 1 is a configuration diagram illustrating a schematic configuration of the proximity sensor system 100. As shown in FIG. 1, the proximity sensor system 100 is for detecting the proximity or presence of the detection target A without contacting the detection target A that is a detection target. The proximity sensor system 100 includes a sensor unit 10 and a detected unit 50.

  The sensor unit 10 is a non-contact detection means. The sensor unit 10 has a detection surface (left end surface in FIG. 1) having a diameter M (hereinafter simply referred to as a diameter) M. The detected unit 50 is formed in a plate shape (plate shape), for example, and is provided on the surface of the detected object A (the right end surface in FIG. 1). The proximity sensor system 100 determines the proximity (presence / absence) of the detection target A when the distance between the detection surface of the sensor unit 10 and the surface of the detection unit provided on the detection target A is equal to or less than the detection distance D. It becomes possible to detect.

  The sensor unit 10 includes a case 11, a cover 12, a detection coil 21, a printed circuit board 13, and a cable 14. The case 11 is, for example, a metal cylindrical or substantially cylindrical cylinder. Inside the case 11, the detection coil 21, the printed circuit board 13, and one end of the cable 14 (left end in FIG. 1) are accommodated. A cover 12 is attached to the opening end of the case 11 (left end in FIG. 1). The cover 12 is a nonconductive member made of resin, for example, and covers the open end side (left side in FIG. 1) of the detection coil 12. The detection coil 21 is, for example, a core coil type inductor, and includes a core 21a made of a magnetic material and an electromagnetic coil 21b wound around the core 21a. Various electronic components and electronic circuits are mounted on the printed circuit board 13, and one end of the cable 14 is electrically connected. The printed circuit board 13 includes, for example, an oscillation circuit 25 and a detection circuit unit 30. The oscillation circuit 25 is electrically connected to the detection coil 21 and electrically connected to the detection circuit unit 30. The detection coil 21 and the oscillation circuit 25 constitute an oscillation circuit unit 20 described later. The detection circuit unit 30 is for detecting the proximity (presence / absence) of the detected object A.

  In the present embodiment, an example in which the printed circuit board 13 includes the oscillation circuit 25 and the detection circuit unit 30 has been described, but the present invention is not limited to this. The printed circuit board 13 may further include a display circuit, an output circuit, a signal amplifier circuit, and the like.

  In the present embodiment, as shown in FIG. 1, an example of the sensor unit 10 having a so-called shield structure in which the detection coil 21 is covered by the case 11 and the cover 12 is shown, but the present invention is not limited to this. The sensor unit 10 may have a so-called unshielded structure in which the detection coil 21 is exposed by protruding from the case 11 to the detected object A side (left side in FIG. 1).

FIG. 2 is a circuit diagram illustrating an example of an equivalent circuit of the oscillation circuit unit 20. As shown in FIG. 2, the oscillation circuit unit 20 includes a detection coil 21 and an oscillation circuit 25. The oscillation circuit 25 is for driving the detection coil 21 to oscillate at a predetermined oscillation frequency f ₀ . The oscillation circuit 25 includes, for example, an oscillation capacitor (capacitor) 26, a bias circuit 27, a current mirror circuit 28, and a voltage-current conversion circuit 29. The oscillation circuit 25 includes an output terminal 25a and an output terminal 25b connected to the detection circuit unit 30 shown in FIG.

The detection coil 21 and the oscillation capacitor 26 of the oscillation circuit 25 constitute an LC oscillation circuit 20A, and the detection coil 21 and the oscillation capacitor 26 are connected in parallel. On the other hand, the bias circuit 27 is configured to include a current source 27a, and a transistor Tr _1. When a predetermined bias current I _b is supplied from the bias circuit 27, the LC oscillation circuit 20A generates a voltage V _T indicated by a double arrow in FIG. The voltage V _T generated in the LC oscillation circuit 20A is applied to the base of the transistor Tr ₂ of the voltage / current conversion circuit 29 via the transistor Tr ₁ of the bias circuit 27.

Voltage-current converting circuit 29, in addition to the transistor Tr _2, configured to include a resistor 29a. Resistor 29a has its emitter of the transistor Tr _2, a line of a reference potential of the oscillation circuit 25 (ground), i.e., between the lines to be connected to the output terminal 25b in FIG. 2, are connected in series. The resistor 29a functions as a resistor that sets a feedback current described later (plays a role of a feedback current setting resistor).

The collector current of the transistor Tr ₂ of the voltage / current conversion circuit 29 flows to the transistor Tr ₃ of the current mirror circuit 28. The transistor Tr ₃ and the transistor Tr ₄ constitute a current mirror circuit 28. Collector current I _fb of the transistor Tr ₄ is fed back (Ford back) to the LC oscillator circuit 20A as a feedback current mentioned above.

The output terminal 25a and the output terminal 25b are connected to both ends of the resistor 29a of the voltage-current conversion circuit 29, respectively. Thereby, the voltage V _Re applied to the resistor 29a indicated by the double arrow in FIG. 2 is output to the detection circuit unit 30 as a signal (output signal) of the oscillation circuit unit 20.

In the oscillation circuit unit 20 configured as described above, the LC oscillation circuit 20A oscillates at a predetermined oscillation frequency f ₀ . Here, when a current flows through the detection coil 21 at a predetermined oscillation frequency f ₀ , the detection coil 21 generates a magnetic flux and forms a magnetic field (magnetic field) between the sensor unit 10 and the detection target A. . In this way, a magnetic field is formed at a predetermined oscillation frequency f ₀ by the oscillation circuit unit 20 of the sensor unit 10.

When the detection coil 21 has an internal resistance R ₁ and an inductance L ₁ and the oscillation capacitor 26 has a capacitance (capacitance) C ₁ , the resonance frequency f ₁ of the LC oscillation circuit 20A is expressed by the following equation (1). Can be represented.

但し、共振周波数ｆ₁の単位は［Ｈｚ］である。

However, the unit of the resonance frequency f ₁ is [Hz].

Thus, since the oscillation circuit unit 20 includes the detection coil 21 and the oscillation capacitor 26, the resonance frequency f ₁ of the LC oscillation circuit 20A configured by the detection coil 21 and the oscillation capacitor 26 is Using the inductance L ₁ of the detection coil 21 and the capacitance C ₁ of the oscillation capacitor 26, it can be calculated by the equation (1).

In the present embodiment, the predetermined oscillation frequency f ₀ of the oscillation circuit unit 20 is set to the same value as the resonance frequency f ₁ calculated by Expression (1). However, the predetermined oscillation frequency f ₀ of the oscillation circuit unit 20 may be a predetermined frequency, and is not limited to the same value as the resonance frequency f ₁ .

Further, in the present embodiment, for the sake of simplification of description, the example of the oscillation circuit unit 20 illustrated in FIG. 2 is shown, but the present invention is not limited to this. The oscillation circuit unit 20 may form a magnetic field at a predetermined oscillation frequency f _0. For example, a known Colpitts oscillation circuit or the like may be used as the oscillation circuit unit 20. Furthermore, the oscillation circuit unit 20 is not limited to a self-excited oscillation circuit, and may be a separately-excited oscillation circuit.

  FIG. 3 is a circuit diagram illustrating an example of the detected unit 50 shown in FIG. As shown in FIG. 3, the detected unit 50 includes a housing 51 and a resonance circuit unit 60 accommodated in the housing 51.

  The resonance circuit unit 60 includes a resonance resistor 61, a resonance coil (inductor) 62, and a resonance capacitor (capacitor) 63. In the resonance circuit unit 60, the resonance resistor 61, the resonance coil 62, and the resonance capacitor 63 are connected to each other in series.

The resonance circuit unit 60 has a resonance frequency f ₂ based on a predetermined oscillation frequency f ₀ of the oscillation circuit unit 20. That is, the resonant circuit 60, based on a predetermined oscillation frequency f ₀ of the oscillator circuit unit 20, the resonance frequency f ₂ is set. Specifically, the resonance frequency f ₂ of the resonance circuit 60 is set to be the same as or substantially the same as the predetermined oscillation frequency f ₀ . Here, since the oscillation circuit unit 20 forms a magnetic field at a predetermined oscillation frequency f ₀ and the resonance circuit unit 60 has a resonance frequency f ₂ based on the predetermined oscillation frequency f ₀ , the resonance circuit unit 60 resonates. In the resonant circuit unit 60 that resonates, a large voltage is generated due to a change in the magnetic field (or magnetic flux of the magnetic field) compared to a case where the resonant circuit unit 60 does not resonate (non-resonant). The power (energy) consumed by the resonance circuit unit 60 gives energy loss to the oscillation circuit unit 20. Therefore, when the sensor unit 10 and the detection target A are close to each other, a large energy loss is given to the oscillation circuit unit 20 as compared with a magnetic body or the like due to a change in the magnetic field (or magnetic flux of the magnetic field). At this time, the oscillation circuit unit 20 changes its oscillation (vibration state), for example, the oscillation is attenuated or the oscillation operation is stopped.

  The detection circuit unit 30 illustrated in FIG. 1 detects the proximity of the detection target A when the oscillation of the oscillation circuit unit 20 is changed by the resonance circuit unit 60.

  On the other hand, a conventional proximity sensor of high frequency oscillation type has, for example, a detection surface with a diameter m, and detects the proximity (presence / absence) of a detection object separated by a detection distance d. In the conventional proximity sensor, similarly to the sensor unit, the detection coil forms a magnetic field by the oscillation circuit unit. When a conventional proximity sensor and a detection object approach each other and the detection object receives the action of a magnetic flux, an eddy current flows through the detection object due to electromagnetic induction. As a result of energy loss (eddy current loss) caused by this eddy current, the value of the oscillation circuit of the conventional proximity sensor, for example, the Q value of the oscillation circuit changes. For this reason, the conventional proximity sensor detects the proximity (presence / absence) of the detection target by detecting a change in the Q value. However, in the conventional proximity sensor, when the object to be detected is a non-magnetic material, an eddy current does not flow or hardly flows even when subjected to the action of magnetic flux, so that the object to be detected is limited to a magnetic material.

  Further, in the conventional proximity sensor, even if the detected object is a magnetic material, the detection distance d differs depending on the type of the detected object. For example, when the diameter m of the detection surface is 18 [mm] and iron is detected as the detection target, eddy current loss is likely to occur in iron, and the change in the Q value is large, so that the detection distance d is 7-8. It is possible to detect when [mm]. On the other hand, when the diameter m of the detection surface is 18 [mm] and aluminum is detected as the detection target, aluminum is less susceptible to eddy current loss and the change in the Q value is small. It becomes possible to detect when it is ˜4 [mm].

  Furthermore, in the conventional proximity sensor, the flowing eddy current varies depending on the size (size or dimension) of the detection object, the shape of the detection surface, and the like, and as a result, the detection distance d also changes.

  On the other hand, in the proximity sensor system 100 of the present embodiment, the resonance circuit unit 60 of the detected unit 50 provided in the detected object A gives energy loss to the oscillation circuit unit 20 of the sensor unit 10, and the energy loss Since the proximity of the detected object A is detected by using the change in the oscillation of the oscillation circuit section 20 due to the above, the oscillation of the oscillation circuit section 20 can be changed even if the detected object A is a non-magnetic material. It is possible to detect the detection target A that is a non-magnetic material. In addition, due to a change in the magnetic field (magnetic flux of the magnetic field), not the detected object A itself but the resonance circuit unit 60 of the detected unit 50 provided in the detected object A gives energy loss, so that the detection distance D is detected. It does not depend on the type of the body A (the detection distance D does not change depending on the type of the detected body A). Further, by using the resonance circuit unit 60 of the detected unit 50 provided on the detected object A, compared with the case of using the electromagnetic induction action or the eddy current loss due to the electromagnetic induction action as in the conventional proximity sensor. Further, it is possible to obtain an advantage (merit) that the detection target A is not easily affected by the size of the detection target A and the shape of the detection surface.

  Here, for example, when some magnetic material exists between the sensor unit 10 and the detection target A, the magnetic flux generated by the oscillation circuit unit 20 acts on the magnetic material, resulting in eddy current loss. obtain. For this reason, the conventional proximity sensor described above is configured to detect the proximity of the detection target when electromagnetic induction or eddy current loss due to the electromagnetic induction action occurs. There was a risk of erroneous detection.

  On the other hand, in the proximity sensor system 100 of the present embodiment, the detection circuit unit 30 detects the proximity of the detection target A when the oscillation of the oscillation circuit unit 20 is changed by the resonance circuit unit 60. As a result, even if some magnetic material exists between the sensor unit 10 and the detection target A and eddy current loss occurs due to electromagnetic induction, the eddy current loss is considered to be energy loss caused by the resonance circuit unit 60. Since it is very small in comparison, the detection circuit unit 30 does not detect the magnetic body as the proximity of the detection target A.

Specifically, the detection circuit unit 30 detects the proximity of the detection target A based on a predetermined evaluation value of the oscillation circuit unit 20. Here, when the sensor unit 10 and the detected object A come close to each other and the resonance circuit unit 60 gives energy loss to the oscillation circuit unit 20, a predetermined evaluation value of the oscillation circuit unit 20, for example, Q value, oscillation frequency, oscillation Values such as the amplitude, the internal resistance R ₁ , the inductance L ₁ , and the impedance of the detection coil 21 vary greatly compared to the case where eddy current loss occurs due to electromagnetic induction. Therefore, the detection circuit unit 30 that detects the proximity of the detection target A easily detects the oscillation change of the oscillation circuit unit 20 by the resonance circuit unit 60 based on the predetermined evaluation value of the oscillation circuit unit 20. be able to.

More specifically, as a predetermined evaluation value of the oscillation circuit unit 20, for example, using the Q value, the detection circuit 30, the Q value of the oscillation circuit 20, becomes equal to or lower than the threshold Q ₀ to be described later Sometimes, the proximity of the detection object A is detected.

FIG. 4 is a graph showing the relationship between the frequency and the Q value for each detection distance D in the proximity sensor system 100 shown in FIG. In FIG. 4, the horizontal axis represents the frequency f [Hz] of the oscillation circuit unit 20, and the vertical axis represents the Q value of the oscillation circuit unit 20. A graph G ₄ shows a threshold value Q ₀ of the Q value of the oscillation circuit unit 20 serving as a reference for detecting resonance, and a graph G ₄₀ does not include the detection target A, that is, the detection distance D is infinite. In this case, the graph _G44 shows the case where the detection distance D is 20 [mm]. Further, for comparison, in a conventional proximity sensor having the same detection surface diameter m (m = M) as the diameter M of the proximity sensor system 100, iron is detected as a detected object, and the detection distance When d is 20 [mm], the threshold value q ₀ of the Q value of the oscillation circuit serving as a reference for detecting eddy current loss is shown by a graph H ₄ . As shown in FIG. 4, in the graph G ₄₀ , the Q value of the oscillation circuit unit 20 is a relatively high (large) value and substantially constant. That is, it means that the oscillation (vibration) of the oscillation circuit unit 20 is stable. On the other hand, the threshold value Q ₀ of the Q value of the oscillation circuit unit 20 shown by the graph G ₄ is a very low (small) value isolated from the graphs G ₄₀ and H ₄ and is almost constant. That is, the threshold value Q ₀ is a value that can be distinguished from a state in which the detection target A is not present or a state in which eddy current loss occurs, and oscillation (vibration) of the oscillation circuit unit 20 is not stable. It can be said that it represents an oscillation state (which is unstable). The graph G ₄₃ is below the threshold value Q ₀ indicated by the graph G ₄ in the vicinity (near the predetermined oscillation frequency f ₀ ).

FIG. 5 is a graph showing the relationship between the detection distance D and the Q value in the proximity sensor system 100 shown in FIG. In FIG. 5, the horizontal axis represents the detection distance D, and the vertical axis represents the Q value of the oscillation circuit unit 20. Graph G ₅ shows a case where the frequency of the oscillation circuit unit 20 is a predetermined oscillation frequency f ₀ . For comparison, as in the case of FIG. 4, in a conventional proximity sensor having a straight m (m = M) of the detection surface that is the same as the diameter M of the proximity sensor system 100, iron is used as the object to be detected. A case where detection is performed and the frequency of the oscillation circuit is also the predetermined oscillation frequency f ₀ is shown by a graph H ₅ . As shown in FIG. 5, in the conventional proximity sensor shown by the graph H ₅ , when the detection distance D is 20 [mm], the QQ value of the oscillation circuit becomes equal to or less than the threshold value q ₀ described above, It becomes possible to detect the proximity of the detection body. On the other hand, in the proximity sensor system 100 shown by the graph G ₅ , when the detection distance D is 20 [mm], the value of the Q value of the oscillation circuit unit 20 is lower than the threshold value Q ₀ described above. Here, in the graph H ₅ , the threshold value Q ₀ is small (low) with respect to the value q when the detection distance D is 0 [mm], that is, when the iron to be detected contacts the proximity sensor. ) You can see that the value is set. Note that the value q when iron, which is the detected body, comes into contact with the proximity sensor is the value of the Q value of the oscillation circuit unit 20 when a magnetic body that is not the detected body A, for example, iron, contacts the sensor unit 10. Are the same or substantially the same.

As described above, the predetermined evaluation value of the oscillation circuit unit 20 is the Q value, and the detection circuit unit 30 determines that the detected circuit A has a Q value equal to or lower than the threshold value Q ₀ . The proximity Q is detected, and the threshold Q ₀ is smaller than the value when the magnetic body contacts the sensor unit 10, so that the threshold Q ₀ is a vortex as shown in FIGS. Since it is set to a value smaller than the Q value (minimum value) that can be taken when current loss occurs, eddy current loss due to electromagnetic induction and energy loss given by the resonance circuit section 60 are clearly distinguished (identified) )can do.

  The housing 51 shown in FIG. 3 is preferably a nonmagnetic housing made of a nonmagnetic material. Examples of the material having nonmagnetic properties include aluminum (AL), stainless steel such as SUS304, copper (Cu), and the like. Accordingly, the magnetic flux generated by the oscillation circuit unit 20 can be applied to the resonance circuit unit 60, and the resonance circuit unit 60 can be protected from the external environment.

The resonance frequency f ₂ in the resonance circuit section 60 shown in FIG. 3 is that the resonance resistor 61 is the resistor R ₂ , the resonance coil 62 is the inductance L ₂ , and the resonance capacitor 63 is the capacitance (electrostatic capacitance) C ₂ . In some cases, it can be expressed by the following formula (2).

但し、共振周波数ｆ₂の単位は［Ｈｚ］である。

However, the unit of the resonance frequency f ₂ is [Hz].

Accordingly, the resonance frequency f ₂ of the resonance circuit unit 60 can be calculated by the equation (2) using the inductance L ₂ of the resonance coil 62 and the capacitance C ₂ of the resonance capacitor 63.

FIG. 6 is a graph showing the relationship between the frequency and the Q value in the resonance circuit unit 60 shown in FIG. In FIG. 6, the horizontal axis represents the frequency f [Hz] of the resonant circuit unit 60, and the vertical axis represents the Q value of the resonant circuit unit 60. A graph G ₆₁ shows a case when the resistance R ₂ of the resonant resistor 61 is relatively large, the graph G ₆₂ is the resonance resistance R ₂ of the resistor 61 is relatively small. As shown in FIG. 6, when the frequency of the resonance circuit unit 60 is the resonance frequency f ₂ , the graph G ₆₁ has the maximum Q value Q ₆₁ and the graph G ₆₂ has the maximum Q value Q ₆₂ . . The graph G ₆₁ and the graph G ₆₂ are symmetric or substantially symmetric curves with the resonance frequency f ₂ as the center line (center axis). The graph G ₆₁ has a maximum value Q ₆₁ smaller than the maximum value Q ₆₂ of the graph G ₆₂ , while the Q value is larger than that of the graph G _{62 in the} frequency band excluding the vicinity (near the resonance frequency f ₂ ). A graph G _61, the frequency band Delta] f ₆₁ having a larger Q value than the predetermined value Q ₆₀ is wider than the frequency band Delta] f ₆₂ of the graph G _62. In other words, the graph G ₆₁ is a wide band curve that reduces the maximum Q value Q ₆₁ while increasing the Q value in a wide frequency band. On the other hand, the graph G ₆₂ has a smaller Q value than the graph G _{61 in the} frequency band excluding the vicinity of the resonance frequency f _{2, and} a maximum value Q ₆₂ larger than the maximum value Q ₆₁ of the graph G _61. Have. A graph G _62, the frequency band Delta] f ₆₂ having a larger Q value than the predetermined value Q ₆₀ is narrower than the frequency band Delta] f ₆₁ of the graph G _61. That is, the graph G _62, while increasing the maximum value Q ₆₂ Q-value, large Q value in a narrow frequency band, which is being narrowed curve. Here, the resistance R ₂ of the resonance resistor 61 does not affect the resonance frequency f ₂ as shown in the above-described equation (2). On the other hand, as shown in FIG. By changing the resistance R ₂ , the frequency characteristic of the Q value of the resonance circuit unit 60 can be changed.

  In the present embodiment, the example of the resonance circuit unit 60 including the resonance resistor 61, the resonance coil 62, and the resonance capacitor 63 is shown in FIG. 3, but the present invention is not limited to this. Hereinafter, a resonance circuit unit different from the resonator circuit unit 60 will be described.

  FIG. 7 is a circuit diagram for explaining another example of the detected unit 50 shown in FIG. As shown in FIG. 7, the detected unit 50 includes a housing 51 and a resonance circuit unit 60 </ b> A housed inside the housing 51.

  The resonance circuit unit 60 </ b> A includes a resonance resistor 61, a resonance coil 62, and a resonance capacitor 63. In the resonance circuit unit 60A, the resistor 61, the resonance coil 62, and the resonance capacitor 63 are connected in parallel to each other. That is, the resonance circuit unit 60A shown in FIG. 7 is not a series resonance circuit like the resonance circuit unit 60 shown in FIG. 3, but a parallel resonance circuit.

In resonance resistor 61 resistor R _2, the resonant coil 62 is an inductance L _2, if the resonant capacitor 63 is the capacitance (electrostatic capacitance) C _2, the resonance frequency f of the resonance circuit section 60A shown in FIG. 7 ₂ can be expressed by the above-described equation (2), similarly to the resonance circuit unit 60 shown in FIG.

  FIG. 8 is a circuit diagram for explaining still another example of the detected unit 50 shown in FIG. As shown in FIG. 7, the detected unit 50 includes a housing 51 and a resonance circuit unit 60 </ b> B housed in the housing 51.

  The resonance circuit unit 60B includes a variable resistor 61B, a resonance coil 62, and a resonance capacitor 63. In the resonance circuit unit 60B, the variable resistor 61B, the resonance coil 62, and the resonance capacitor 63 are connected to each other in series. That is, the resonance circuit unit 60B shown in FIG. 8 includes a variable resistor 61B instead of the resonance resistor 61 of the resonance circuit unit 60 shown in FIG.

Here, in the oscillation circuit unit 20 shown in FIG. 2, the detection coil 21 and the oscillation capacitor 26 are caused by variations in the product of the element itself, variation due to mounting (assembly) of the sensor unit 10 in the case 11, and the like. , At least _one of the inductance L ₁ and the capacitance C ₁ may change. As a result, an error occurs in the resonance frequency of the LC oscillation circuit 20A. When the predetermined oscillation frequency f ₀ of the oscillation circuit unit 20 is set to be the same as the resonance frequency of the LC oscillation circuit 20A including the error, the predetermined oscillation frequency An error ± Δf ₀ can occur at the frequency f ₀ . In this case, even if the resonance circuit 60 tries to set the resonance frequency f ₂ based on the predetermined oscillation frequency f ₀ and sets the resonance frequency f ₂ to be the same as the resonance frequency f ₁ calculated by the equation (1), Since there is an error ± Δf _{0 at} the predetermined oscillation frequency f ₀ of the actual oscillation circuit unit 20, the Q value of the resonance circuit unit 60 is not sufficiently increased at the resonance frequency f ₂ , and the proximity of the detected object A is increased. May not be detected.

In contrast, the resonance circuit section 60B shown in FIG. 8 includes a variable resistor 61B, when the error ± Delta] f ₀ of a predetermined oscillation frequency f ₀ is large, a relatively large resistance R ₂ of the variable resistor 61B By changing the value, the Q value of the resonance circuit unit 60B can be changed to a wide frequency characteristic having a large Q value in a wide frequency band, as in the graph G ₆₁ shown in FIG. The unit 60B can absorb the error ± Δf ₀ of the predetermined oscillation frequency f ₀ . On the other hand, when the error ± Δf _{0 of} the predetermined oscillation frequency f ₀ is small, the resistance R ₂ of the variable resistor 61B is changed to a relatively small value, as shown in the graph G ₆₂ shown in FIG. Q value of the resonance circuit portion 60B may be a large narrow banded frequency characteristics of Q values in a narrow frequency band, it is possible to have a large maximum value Q ₆₂ in the vicinity of the resonance frequency f _2.

  FIG. 9 is a circuit diagram for explaining still another example of the detected unit 50 shown in FIG. As shown in FIG. 7, the detected unit 50 includes a housing 51 and a resonance circuit unit 60 </ b> C housed in the housing 51.

  The resonance circuit unit 60C includes a resonance resistor 61, a resonance coil 62, and a variable capacitor 63C. In the resonance circuit unit 60C, the resonance resistor 61, the resonance coil 62, and the variable capacitor 63C are connected to each other in series. That is, the resonance circuit unit 60C shown in FIG. 9 includes a variable capacitor 63C instead of the resonance capacitor 63 of the resonance circuit unit 60 shown in FIG.

Here, in the actual oscillator circuit unit 20, by a method of actually measuring the resonant frequency f ₁ and a predetermined oscillation frequency f _0, an error ± Delta] f ₀ and a predetermined oscillation frequency f ₀ itself predetermined oscillation frequency f ₀ If known, it may be preferable to change the capacitance C ₂ of the variable capacitor 63C rather than changing the resistance R ₂ of the resonance resistor 61. That is, since the capacitance C ₂ of the variable capacitor 63C changes the resonance frequency f ₂ as shown in the above-described equation (2), the capacitance C ₂ of the variable capacitor 63C is changed as shown in FIG. In the graph G ₆₁ and the graph G ₆₂ , the resonance frequency f ₂ that is the center line (center axis) can be shifted (moved). Therefore, when the error of the predetermined oscillation frequency f ₀ is positive, the capacitance C ₂ of the variable capacitor 63C is changed to a small value, so that the graph G ₆₁ and the graph G ₆₂ are positive (to the right in FIG. 6). When the error can be shifted and the error of the predetermined oscillation frequency f ₀ is negative, by changing the capacitance C ₂ of the variable capacitor 63C to a small value, the graph G ₆₁ and the graph G ₆₂ are in the negative direction (in FIG. 6). Shift to the left).

In the present embodiment, the example in which the detection circuit unit 30 detects the proximity of the detection target A based on the Q value of the oscillation circuit unit 20 has been described, but the present invention is not limited to this. The detection circuit unit 30 may determine the proximity of the detection target A when the oscillation of the oscillation circuit unit 20 is changed by the resonance circuit units 60, 60A, 60B, and 60C. For example, even if the proximity of the detection target A is determined based on the oscillation frequency, oscillation amplitude, or impedance of the oscillation circuit unit 20 or the value of the internal resistance R ₁ or inductance L _{1 of} the detection coil 21, etc. Good.

As described above, according to the proximity sensor system 100 of the present embodiment, the sensor unit 10 includes the oscillation circuit unit 20 that forms a magnetic field at the predetermined oscillation frequency f ₀ , and the sensor unit 10 is based on the predetermined oscillation frequency f ₀ . comprising resonance circuit 60,60A having the resonance frequency f _2, 60B, and the detection unit 50 comprising the 60C, the. Here, since the oscillation circuit unit 20 forms a magnetic field at the predetermined oscillation frequency f ₀ and the resonance circuit units 60, 60A, 60B, and 60C have the resonance frequency f ₂ based on the predetermined oscillation frequency f ₀ , the resonance circuit The parts 60, 60A, 60B, 60C resonate. In the resonant circuit unit 60 that resonates, a large voltage is generated due to a change in the magnetic field (or magnetic flux of the magnetic field) compared to a case where the resonant circuit unit 60 does not resonate (non-resonant). The power (energy) consumed by the resonance circuit units 60, 60 </ b> A, 60 </ b> B, and 60 </ b> C causes energy loss to the oscillation circuit unit 20. Therefore, when the sensor unit 10 and the detection target A are close to each other, a large energy loss is given to the oscillation circuit unit 20 as compared with a magnetic body or the like due to a change in the magnetic field (or magnetic flux of the magnetic field). At this time, since the oscillation circuit unit 20 changes its oscillation (vibration state), for example, the oscillation is attenuated or the oscillation operation is stopped, the detection circuit unit 30 can detect the proximity of the detection target A. It becomes.

  Further, in the proximity sensor system 100, the resonance circuit unit 60 of the detection unit 50 provided in the detection target A gives energy loss to the oscillation circuit unit 20 of the sensor unit 10, and the oscillation circuit unit 20 due to the energy loss causes the energy loss. Since the proximity of the detected object A is detected using the change in oscillation, the vibration of the oscillation circuit unit 20 can be changed even if the detected object A is a non-magnetic substance, and the non-magnetic substance. It is possible to detect the detection target A. Further, due to the change in the magnetic field (magnetic flux of the magnetic field), not the detected object A itself, but the resonance circuit units 60, 60A, 60B, 60C of the detected unit 50 provided in the detected object A give energy loss. The detection distance D does not depend on the type of the detection target A (the detection distance D does not change depending on the type of the detection target A). Further, by using the resonance circuit unit 60 of the detected unit 50 provided on the detected object A, compared with the case of using the electromagnetic induction action or the eddy current loss due to the electromagnetic induction action as in the conventional proximity sensor. Further, it is possible to obtain an advantage (merit) that the detection target A is not easily affected by the size of the detection target A and the shape of the detection surface.

  Further, the detection circuit unit 30 detects the proximity of the detection target A when the oscillation of the oscillation circuit unit 20 is changed by the resonance circuit units 60, 60A, 60B, and 60C. As a result, even if some magnetic material exists between the sensor unit 10 and the detection target A and eddy current loss occurs due to electromagnetic induction, the eddy current loss is detected by the resonance circuit units 60, 60A, 60B, Since the energy loss given by 60C is very small, the detection circuit unit 30 does not detect the magnetic body as the proximity of the detection target A. Therefore, erroneous detection of the detection target A can be prevented. Further, the proximity sensor system 100 can use the sensor unit 10 and the detected unit 50 like a key and a lock (lock), for example, because it does not detect even if a thing other than the detected object A comes close. It can be suitably applied to the security field.

Further, according to the proximity sensor system 100 in the present embodiment, the detection circuit unit 30 detects the proximity of the detection target A based on a predetermined evaluation value of the oscillation circuit unit 20. Here, when the sensor unit 10 and the detection target A come close to each other and the resonance circuit units 60, 60A, 60B, and 60C give energy loss to the oscillation circuit unit 20, a predetermined evaluation value of the oscillation circuit unit 20, for example, Q Values, oscillation frequency, oscillation amplitude, values such as the internal resistance R ₁ , inductance L ₁ , and impedance of the detection coil 21 vary greatly compared to the case where eddy current loss occurs due to electromagnetic induction. Therefore, the detection circuit unit 30 that detects the proximity of the detection target A is based on the predetermined evaluation value of the oscillation circuit unit 20, thereby changing the oscillation of the oscillation circuit unit 20 by the resonance circuit units 60, 60 A, 60 B, and 60 C. Can be easily detected. Therefore, when the oscillation of the oscillation circuit unit 20 is changed by the resonance circuit units 60, 60A, 60B, and 60C, the detection circuit unit 30 that detects the proximity of the detection target A can be easily configured (realized). it can.

Further, according to the proximity sensor system 100 in the present embodiment, the predetermined evaluation value of the oscillation circuit unit 20 is a Q value, and the detection circuit unit 30 has a Q value of the oscillation circuit unit 20 equal to or less than a threshold value Q ₀ . When this happens, the proximity of the detection object A is detected, and the threshold value Q ₀ is smaller than the value when the magnetic material contacts the sensor unit 10. Accordingly, as shown in FIGS. 4 and 5, the threshold value Q ₀ is set to a value smaller than the Q value (minimum value) that can be taken when eddy current loss occurs. It is possible to clearly distinguish (identify) the eddy current loss due to the action and the energy loss caused by the oscillation circuit unit 20 and the resonance circuit units 60, 60A, 60B, and 60C. Therefore, it is possible to reliably prevent erroneous detection of the detection target A due to the occurrence of eddy current loss.

Further, according to the proximity sensor system 100 in the present embodiment, the resonance circuit units 60, 60A, 60B, and 60C include the resonance resistor 61 or the variable resistor 61B, the resonance coil 62, the resonance capacitor 63, or the variable. And a capacitor 63C. Accordingly, the resonance frequency f ₂ of the resonance circuit units 60, 60A, 60B, and 60C is expressed by the equation (2) using the inductance L ₂ of the resonance coil 62 and the capacitance C _{2 of} the resonance capacitor 63 or the variable capacitor 63C. It becomes possible to calculate by. Therefore, by setting the capacitance C ₂ of the inductance L ₂ and the resonance capacitor 63 or the variable capacitor 63C of the resonance coils 62 based on a predetermined oscillation frequency f ₀ of the oscillator circuit unit 20, a predetermined oscillation frequency f ₀ The resonance circuit units 60, 60A, 60B, and 60C having the resonance frequency f ₂ based on the above can be easily configured (realized).

Further, the resistance R ₂ of the resonance resistor 61 or the variable resistor 61B does not affect the resonance frequency f ₂ as shown in the equation (2), while the resonance resistor 61 or the resistance R ₂ as shown in FIG. by varying the resistance R ₂ of the variable resistor 61B, the resonance circuit section 60, 60A, 60B, it is possible to change the frequency characteristic of the Q value of 60C. Therefore, by setting in accordance with the embodiment using the resonant resistor 61 or resistor R ₂ of the variable resistor 61B (purpose), without changing the resonance frequency f _2, the resonance circuit section 60, 60A, 60B, The frequency characteristic of the Q value of 60C can be changed to a desired characteristic.

Further, according to the proximity sensor system 100 in the present embodiment, the resonance circuit unit 60B includes the variable resistor 61B. Thereby, when the error ± Δf ₀ of the predetermined oscillation frequency f ₀ is large, the resistance R ₂ of the variable resistor 61B is changed to a relatively large value, as shown in the graph G ₆₁ shown in FIG. The Q value of the resonance circuit unit 60B can have a wide frequency characteristic with a large Q value in a wide frequency band, and the resonance circuit unit 60B can absorb an error ± Δf ₀ of a predetermined oscillation frequency f _0. Is possible. Therefore, even when the error ± Δf _{0 of} the predetermined oscillation frequency f ₀ is large, the Q value of the resonance circuit unit 60B of the detected unit 50 can be increased, and the proximity of the detected object A can be detected. On the other hand, when the error ± Δf _{0 of} the predetermined oscillation frequency f ₀ is small, the resistance R ₂ of the variable resistor 61B is changed to a relatively small value, thereby resonating as shown in the graph G ₆₂ shown in FIG. Q value of the circuit section 60B may be a large narrow banded frequency characteristics of Q values in a narrow frequency band, it is possible to have a large maximum value Q ₆₂ in the vicinity of the resonance frequency f _2. Therefore, when the oscillation of the oscillation circuit unit 20 is changed by the resonance circuit unit 60B, for example, the Q value of the oscillation circuit unit 20 is greatly changed (decreased), so that erroneous detection of the detection target A can be reliably prevented. Can do.

Further, according to the proximity sensor system 100 in the present embodiment, the resonance circuit unit 60C includes the variable capacitor 61C. Here, the capacitance C ₂ of the variable capacitor 63C changes the resonance frequency f ₂ as shown in the equation (2). Therefore, by changing the capacitance C ₂ of the variable capacitor 63C, the graph G ₆₁ shown in FIG. and in the graph G _62, thereby the resonance frequency f ₂ is the central line (central axis) is shifted (moved). Therefore, when the error of the predetermined oscillation frequency f ₀ is positive, the capacitance C ₂ of the variable capacitor 63C is changed to a small value, so that the graph G ₆₁ and the graph G ₆₂ are positive (to the right in FIG. 6). When the error can be shifted and the error of the predetermined oscillation frequency f ₀ is negative, by changing the capacitance C ₂ of the variable capacitor 63C to a small value, the graph G ₆₁ and the graph G ₆₂ are in the negative direction (in FIG. 6). Shift to the left). Therefore, when the error ± Delta] f ₀ and the actual predetermined oscillation frequency f ₀ itself predetermined oscillation frequency f ₀ is known, can be to resonate the resonance circuit 60C of the detection unit 50, the object to be detected A Proximity can be easily detected.

  Further, according to the proximity sensor system 100 in the present embodiment, the detected unit 50 includes the nonmagnetic casing 51 that houses the resonance circuit units 60, 60A, 60B, and 60C. Accordingly, the magnetic flux generated by the oscillation circuit unit 20 can be applied to the resonance circuit units 60, 60A, 60B, and 60C, and the resonance circuit units 60, 60A, 60B, and 60C can be protected from the external environment. it can. Accordingly, the detected unit 50 can improve environmental resistance performance such as water resistance, oil resistance, dirt resistance, vibration resistance, shock resistance, heat resistance, cold resistance, and the proximity sensor system 100 has environmental resistance. It can be suitably applied to the required use.

Further, according to the proximity sensor system 100 in the present embodiment, the oscillation circuit unit 20 includes the detection coil 21 and the oscillation capacitor 26. Here, when a current flows through the detection coil 21 at a predetermined oscillation frequency f ₀ , the detection coil 21 generates a magnetic flux and forms a magnetic field (magnetic field) between the sensor unit 10 and the detection target A. . Thus, the oscillation circuit unit 20 that forms a magnetic field at the predetermined oscillation frequency f ₀ can be easily configured (realized).

Further, the resonance frequency f ₁ of the LC oscillation circuit 20A composed of the detection coil 21 and the oscillation capacitor 26 is expressed by the equation (1) using the inductance L ₁ of the detection coil 21 and the capacitance C ₁ of the oscillation capacitor 26. ). Therefore, the impedance of the LC oscillation circuit 20A can be maximized by setting the predetermined oscillation frequency f ₀ of the oscillation circuit unit 20 to be the same as the resonance frequency f ₁ calculated by the equation (1). The power consumption of the unit 20 can be reduced.

  Note that the configurations of the above-described embodiments may be combined, or some components may be replaced. The configuration of the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Sensor unit 11 ... Case 12 ... Cover 13 ... Printed circuit board 14 ... Cable 20 ... Oscillation circuit part 20A ... LC oscillation circuit 21 ... Detection coil 21a ... Core 21b ... Electromagnetic coil 25 ... Oscillation circuit 25a, 25b ... Output terminal 26 ... Oscillator capacitor 27 ... Bias circuit 28 ... Current mirror circuit 29 ... Voltage current converter circuit 30 ... Detection circuit unit 50 ... Detected unit 51 ... Case 60, 60A, 60B, 60C ... Resonance circuit unit 61 ... Resonance resistor 61B ... variable resistor 62 ... resonance coil 63 ... resonant capacitor 63C ... variable capacitor 100 ... proximity sensor system A ... detection object D ... detected distance M ... diameter Q ₀ ... threshold

Claims (8)

A sensor unit including an oscillation circuit unit that forms a magnetic field at a predetermined oscillation frequency;
A to-be-detected unit, and a to-be-detected unit comprising a resonance circuit unit having a resonance frequency based on the predetermined oscillation frequency,
The sensor unit is
When the oscillation of the oscillation circuit unit is changed by the resonance circuit unit, further comprising a detection circuit unit for detecting the proximity of the detected object,
Proximity sensor system. The detection circuit unit detects the proximity of the detected object based on a predetermined evaluation value of the oscillation circuit unit;
The proximity sensor system according to claim 1. The predetermined evaluation value is a Q value,
The detection circuit unit detects the proximity of the detected object when a Q value of the oscillation circuit unit is a threshold value or less,
The threshold value is a value smaller than the Q value of the oscillation circuit unit when the magnetic body contacts the sensor unit.
The proximity sensor system according to claim 2. The resonant circuit unit includes a resistor, a coil, and a capacitor.
The proximity sensor system according to any one of claims 1 to 3. The resistor is a variable resistor,
The proximity sensor system according to claim 4. The capacitor is a variable capacitor,
The proximity sensor system according to claim 4 or 5. The proximity sensor system according to any one of claims 1 to 6, wherein the detected unit further includes a nonmagnetic housing that houses the resonant circuit unit. The oscillation circuit unit includes a coil and a capacitor.
The proximity sensor system according to any one of claims 1 to 7.

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