JP6351437B2 - Proximity switch - Google Patents

Description

  The present invention relates to a proximity switch.

  Patent Document 1 describes a magnetic proximity switch using a Hall element.

JP-A-60-162313

  However, since the Hall element is a semiconductor, it cannot be used in a high temperature atmosphere. For this reason, a proximity switch capable of stably detecting a target proximity state even at an environmental temperature exceeding 100 ° C. is desired.

  The present invention has been made in view of the above, and an object thereof is to provide a proximity switch that operates under a wide range of environmental temperatures.

  In order to solve the above-described problems and achieve the object, the proximity switch of the present invention includes a detection unit made of a magnetic material having conductivity, and a magnetic field corresponding to the relative distance, with a relative distance to the detection unit changing. And a detection circuit for detecting a proximity state of the detection unit based on an impedance component of the detection unit according to a change in a magnetic field applied to the detection unit. Features.

  In the present invention, the magnetic material is preferably a soft magnetic material.

  In the present invention, the soft magnetic material is preferably an alloy containing at least iron.

  In the present invention, the soft magnetic material is preferably an FeNi alloy further containing nickel.

  Moreover, in this invention, it is preferable that the said FeNi alloy contains 70 mass% or more of Ni.

  Moreover, in this invention, when the said detection part and the said to-be-detected part exist in the said proximity | contact state, it is preferable that the magnetic material of the said detection part is magnetically saturated with the magnetic field of the said to-be-detected part.

  Further, in the present invention, the detection circuit supplies the detection unit with an impedance component of the detection unit at a current applied to the detection unit at a first frequency and a second frequency that is higher than the first frequency. It is preferable that the proximity state of the detected member is detected in accordance with a change in the ratio of the applied current to the impedance component of the detection unit.

  According to the present invention, it is possible to provide a proximity switch that is not affected by the environmental temperature.

FIG. 1 is an explanatory diagram schematically illustrating the proximity switch according to the first embodiment. FIG. 2 is an explanatory diagram schematically illustrating an application example to which the proximity switch according to the first embodiment is applied. FIG. 3 is an explanatory diagram schematically illustrating the proximity switch according to the second embodiment. FIG. 4 is an explanatory diagram schematically illustrating the proximity switch according to the third embodiment. FIG. 5 is an explanatory diagram schematically illustrating the proximity switch according to the fourth embodiment. FIG. 6 is an explanatory diagram schematically illustrating the proximity switch according to the fifth embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a form for implementing a proximity switch according to the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings. In addition, this invention is not limited by the following embodiment. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be appropriately combined.

(Embodiment 1)
FIG. 1 is an explanatory diagram schematically illustrating the proximity switch according to the first embodiment. FIG. 2 is an explanatory diagram schematically illustrating an application example to which the proximity switch according to the first embodiment is applied. As shown in FIG. 1, the proximity switch includes a detection unit 1, a detected unit 2, a detection circuit 3, and an oscillation circuit 4.

  For example, as shown in FIG. 2, the detection unit 1 and the detected unit 2 are attached to the support member 11 and the support member 12 so as to face each other when they are close to each other. The support member 11 and the support member 12 are connected so as to be relatively rotatable around the rotating portion 13. 1 and FIG. 2, the direction in which the detected portion 2 together with the support member 11 relatively approaches the detection portion 1 of the support member 12 is the approach direction S-on, and the detected portion 2 together with the support member 11 detects the support member 12 A direction that is relatively separated from the portion 1 is defined as a separation direction S-off. The support member 11 may approach the support member 12, and the support member 12 may approach the support member 11.

  The detection unit 1 is a rod-shaped, linear, plate-shaped, spiral-shaped or indefinite-shaped member of a soft magnetic material.

  The material of the detection unit 1 of the present embodiment is a soft magnetic material, and is an FeNi alloy containing iron (Fe) and nickel (Ni). It is preferable that the material of the detection part 1 contains 70 mass% or more and 85 mass% or less of Ni, and the remainder is Fe. More preferably, the material of the detection unit 1 contains 78% by mass of Ni, and the balance is Fe. By including 70 mass% or more and 85 mass% or less of Ni, the detection unit 1 becomes excellent in high magnetic permeability and magnetization characteristics. The FeNi alloy may contain 0% by mass to 6% by mass of copper (Cu) and 0% by mass to 6% by mass of molybdenum (Mo). Moreover, the FeNi alloy may contain inevitable impurities, and may contain other elements as long as it exhibits soft magnetism. A soft magnetic material has a property that a magnetic dipole in a substance is more easily oriented in the direction of the magnetic field when a magnetic field is applied from the outside than a hard magnetic material. On the other hand, hard magnetic materials, that is, permanent magnets, are difficult to direct magnetic dipoles in a substance in the direction of the magnetic field when a magnetic field is applied from the outside, and the magnetic dipoles remain aligned in a specific direction. The material of the detection unit 1 of Embodiment 1 is preferably a soft magnetic material.

  The material of the detection part 1 of this embodiment is not restricted to this, The FeNi alloy which contains 42 mass% or more and 49 mass% or less of Ni, and the remainder is Fe may be sufficient. Further, the material of the detection unit 1 of the present embodiment may be a FeBSi alloy, a FeCoBSi alloy, or a FeSiAl alloy.

  The detected portion 2 is a hard magnetic material, that is, a permanent magnet, and a neodymium magnet, a samarium cobalt magnet, a ferrite magnet, or an alnico magnet can be used. When the relative distance between the detection unit 2 and the detection unit 1 becomes an operation distance described later, the detection unit 2 can apply a magnetic field that magnetically saturates the soft magnetic material of the detection unit 1.

  The support member 11 and the support member 12 are made of plastic, for example. The rotating unit 13 is, for example, a hinge mechanism in which a rotation shaft is inserted into the support member 11 and the support member 12 so as to be rotatably connected. As an explanation of the first embodiment, the structure in which the support member 11 and the support member 12 can be brought close to or separated from each other by the rotating unit 13 is illustrated. However, the present invention is not limited to this, and any support structure such as a slide mechanism or a spring mechanism can be used. It may be.

  The oscillation circuit 4 applies an alternating current having a frequency f to the detection unit 1. For example, the oscillation circuit 4 can be exemplified by an AC power source, and the AC power source includes a transformer, and supplies current through the transformer.

  The detection circuit 3 only needs to detect a change in impedance of the detection unit 1. The notification circuit 5 is configured such that, based on the output of the detection circuit 3 or the detected impedance change, the detected unit 2 detects the detection unit 2 by transmitting light, sound, radio waves, displaying a display medium, vibration, and combinations thereof. 1 is a circuit that can be relatively close to 1, and can be informed that a proximity state of a predetermined distance or more has been reached. The detection circuit 3 can be exemplified by an RF impedance analyzer.

  Here, the current that the oscillation circuit 4 passes through the detection unit 1 is affected by the skin effect. The electrical resistance of the soft magnetic material of the detection unit 1 decreases as the skin depth d increases. The skin depth when the electrical resistivity of the soft magnetic material of the detection unit 1 is ρ, the angular frequency of the current applied to the detection unit 1 by the oscillation circuit 4 is ω (= 2πf), and the absolute permeability of the detection unit 1 is μ. d can be calculated | required by following formula (1).

d = (2ρ / (ωμ)) ^1/2 (1)

  In a non-proximity state in which the detected portion 2 is separated beyond a predetermined distance (hereinafter referred to as an operating distance) in a separation direction S-off that is relatively away from the detecting portion 1, the soft magnetism of the detecting portion 1. The material is not magnetically saturated. Since the soft magnetic material of the detection unit 1 has a large absolute permeability μ, the above-described skin depth d becomes shallow. For this reason, the electric current of the alternating current which flows into the detection part 1 is small, and the impedance component of the detection part 1 becomes large. In this case, the detection circuit 3 does not output to the notification circuit 5 because the impedance component of the detection unit 1 exceeds a predetermined threshold value.

  In the proximity state where the detected unit 2 and the detection unit 1 are relatively close to each other in the approach direction S-on within the operating distance, the soft magnetic material of the detection unit 1 is magnetically saturated, and the detection unit 1 The absolute permeability μ is close to the air permeability (permeability = 1). For this reason, compared with the case where the to-be-detected part 2 and the detecting part 1 are relatively separated beyond the operating distance in the separation direction S-off, the distance between the to-be-detected part 2 and the detecting part 1 is the operating distance. In the following cases, the above-mentioned skin depth d becomes deep. For this reason, the electric current of the alternating current which flows into the detection part 1 increases, and the impedance component of the detection part 1 becomes small. In this case, the detection circuit 3 outputs the impedance component of the detection unit 1 to the notification circuit 5 because the impedance component is equal to or less than a predetermined threshold value. Based on the output of the detection circuit 3, the notification circuit 5 notifies that the detected unit 2 has approached the detection unit 1 relatively close to the operating distance by light, sound, radio wave transmission, or the like. .

  As described above, the proximity switch according to the first embodiment is a permanent switch that applies a magnetic field in accordance with the relative distance to the detection unit 1 and the detection unit 1 that is a member of a soft magnetic material. And a detection circuit that detects the proximity state of the detected portion 2 based on the impedance component of the detecting portion 1 according to a change in the magnetic field applied to the detecting portion 1. For example, the Curie point of a NiFe alloy is usually around 350 ° C., and a predetermined magnetic property can be maintained at an environmental temperature greatly exceeding 100 ° C. For this reason, the proximity switch according to the first embodiment can stably detect the presence or absence of the proximity state between the detection unit 1 and the detected unit 2 even at an environmental temperature exceeding 100 ° C.

  Since the soft magnetic material of the detection unit 1 is an FeNi alloy containing iron and nickel, the magnetization characteristics are high and the frequency response to the frequency f can be increased.

  The soft magnetic material of the detection unit 1 is an FeNi alloy and contains 70% by mass or more of Ni. As a result, the absolute permeability is high, and the difference in the change in the skin depth d between the non-proximity state and the proximity state can be increased.

  When the detection unit 1 and the detection unit 2 are in the above-described proximity state, the soft magnetic material of the detection unit 1 is magnetically saturated by the magnetic field of the detection unit 2. For this reason, the proximity switch of the first embodiment has a lower failure probability and higher reliability than the mechanical proximity switch.

  The oscillation circuit 4 alternately applies a frequency lower than the frequency f having a small skin effect and the frequency f described above to the detection unit 1, and the detection circuit 3 sets the ratio of impedance components in the proximity state. It may be detected. Thereby, for example, when the performance of the detection unit 1 deteriorates in a high temperature environment, the ratio of the impedance component changes, so that the detection circuit 3 can output to the notification circuit 5 so as to be replaced early. Moreover, if it detects by the ratio of an impedance component, the detection part 1 will not be influenced by deterioration, but can be used stably for a long period of time.

(Embodiment 2)
FIG. 3 is an explanatory diagram schematically illustrating the proximity switch according to the second embodiment. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The proximity switch according to the second embodiment includes a transmission circuit 7 and an antenna 6 instead of the oscillation circuit 4. The transmission circuit 7 transmits the signal RW having the transmission frequency f to the detection unit 1A located at the distance L via the antenna 6. The detection unit 1A is made of the same material as the detection unit 1 described above. The detection unit 1 </ b> A has a coil shape and can receive the signal RW from the antenna 6.

  When the detected portion 2 and the detecting portion 1A are separated from each other in the separation direction S-off direction beyond the operating distance, the soft magnetic material of the detecting portion 1A is not magnetically saturated. Since the soft magnetic material of the detection unit 1A has a large absolute permeability μ, the above-described skin depth d becomes shallow. For this reason, the impedance component of the detection unit 1 is large, and the induced current that has received the signal RW in the detection unit 1A is small. In this case, the detection circuit 3 does not output to the notification circuit 5 because the current based on the impedance component of the detection unit 1A is smaller than the threshold value.

  When the detected portion 2 and the detecting portion 1A are close to each other in the approaching direction S-on and not more than the operating distance, the soft magnetic material of the detecting portion 1 is magnetically saturated, and the absolute transparency of the detecting portion 1A is not detected. The magnetic permeability μ is close to the air permeability 1 of air. For this reason, when the distance between the detected part 2 and the detecting part 1A is equal to or smaller than the operating distance as compared with the case where the detected part 2 exceeds the operating distance relative to the detecting part 1A, the above-described skin The depth d becomes deeper. For this reason, the impedance component of the detector 1A is small, and the induced current that has received the signal RW in the detector 1A increases. In this case, the detection circuit 3 outputs the current based on the impedance component of the detection unit 1 </ b> A to the notification circuit 5 because the current is equal to or greater than the threshold. Based on the output of the detection circuit 3, the notification circuit 5 notifies that the detected unit 2 is relatively close to the detection unit 1 </ b> A and is close to the operating distance by transmission of light, sound, radio waves, or the like. .

  As described above, the proximity switch according to the second embodiment is a permanent switch that applies a magnetic field according to the relative distance to the detection unit 1A and the detection unit 1A that is a member of a soft magnetic material. And a detection circuit 3A that detects the proximity state of the detection unit 2 based on the impedance component of the detection unit 1A corresponding to a change in the magnetic field applied to the detection unit 1A. For example, the Curie point of a NiFe alloy is 460 ° C., and a predetermined magnetic property can be maintained at an environmental temperature greatly exceeding 100 ° C. For this reason, the proximity switch according to the second embodiment can stably detect the presence / absence of the proximity state between the detection unit 1A and the detection target unit 2 even at an environmental temperature exceeding 100 ° C.

(Embodiment 3)
FIG. 4 is an explanatory diagram schematically illustrating the proximity switch according to the third embodiment. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The detected part 2A of the third embodiment is a so-called electromagnet, and includes a coil 21 made of a conductor and a core 22 made of a soft magnetic material. The detected unit 2A can apply a magnetic field that magnetically saturates the soft magnetic material of the detecting unit 1 when the relative distance from the detecting unit 1 becomes a predetermined distance.

(Embodiment 4)
FIG. 5 is an explanatory diagram schematically illustrating the proximity switch according to the fourth embodiment. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the proximity switch of the fourth embodiment, the reference member 8 and the detection unit 1 are arranged in parallel, and a detection circuit is selected by selecting the contact 1a connected to the detection unit 1 side and the contact 8a connected to the reference member 8 side. 3 and a selection switch SW1 connected to 3.

The reference member 8 is a material having a predetermined impedance component that is not affected by a magnetic field, and is, for example, Mn ₂ Sb. The selection switch SW1 alternately obtains the contact point 1a connected to the detection unit 1 side and the contact point 8a connected to the reference member 8 side, whereby the detection circuit 3 obtains the ratio of impedance components in the proximity state. it can. Thereby, for example, when the performance of the detection unit 1 deteriorates in a high temperature environment, the ratio of the impedance component changes, so that the detection circuit 3 can output to the notification circuit 5 so as to be replaced early.

(Embodiment 5)
FIG. 6 is an explanatory diagram schematically illustrating the proximity switch according to the fifth embodiment. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the proximity switch of the fifth embodiment, the oscillation circuit 4 and the oscillation circuit 4 ′ are arranged in parallel instead of the oscillation circuit 4, and the contact 3a connected to the detection circuit 3 side, the contact 4a connected to the oscillation circuit 4 side, and There is provided a selection switch SW2 that is switchably connected to a contact 4′a that is connected to the oscillation circuit 4 ′ side.

  The oscillation circuit 4 oscillates at the first frequency f1. The oscillation circuit 4 'oscillates at the second frequency f2. The frequency f2 is higher than the frequency f1. As described above, in the proximity state, the soft magnetic material of the detector 1 is magnetically saturated, and the absolute permeability μ of the detector 1 is close to the air permeability (permeability = 1). Here, the current that the oscillation circuit 4 passes through the detection unit 1 is not easily affected by the skin effect. Compared to the case where the detected portion 2 and the detecting portion 1 are relatively separated from each other in the separation direction S-off beyond the operating distance, the distance between the detected portion 2 and the detecting portion 1 is equal to or less than the operating distance. The skin depth at the first frequency f1 and the second frequency f2 becomes deep.

  The skin depth at the first frequency f1 and the skin depth at the second frequency f2 have different skin depths because the angular frequency ω of the current applied to the detection unit 1 is different as shown in the above-described equation (1). . In the current of the first frequency f1 applied by the oscillation circuit 4, the skin effect of the detection unit 1 is small (in a state where the skin depth is deep), and the current easily flows through the detection unit 1.

  In the current of the second frequency f2 applied by the oscillation circuit 4 ′, the skin effect of the detection unit 1 is large (in a state where the skin depth is shallow), that is, the current flows in the detection unit 1 as compared with the current of the first frequency f1. Hateful.

  The selection switch SW2 can switch the frequency applied to the detection unit 1 to the first frequency f1 or the second frequency f2 by alternately selecting the contact 4a and the contact 4'a shown in FIG. Therefore, the detection circuit 3 can obtain the impedance component of the detection unit 1 when the oscillation circuit 4 and the oscillation circuit 4 ′ are connected. Thereby, the detection circuit 3 may detect the ratio of the impedance component of the second frequency f2 to the first frequency f1 in the proximity state.

  In the non-proximity state in which the detected portion 2 is separated beyond the operating distance in the separation direction S-off that is relatively separated from the detecting portion 1, the soft magnetic material of the detecting portion 1 is not magnetically saturated. Since the soft magnetic material of the detection unit 1 has a large absolute permeability μ, the above-described skin depth d becomes shallow. For this reason, the currents of the alternating currents flowing through the detection unit 1 at the first frequency f1 and the second frequency f2 are different. The detection circuit includes an impedance component of the detection unit 1 at a current applied to the detection unit 1 at the first frequency f1, and an impedance component of the detection unit 1 at a current applied to the detection unit 1 at the second frequency f2. The ratio is detected as a ratio different from 1: 1. In this case, the detection circuit 3 does not output to the notification circuit 5 because the ratio of the impedance component of the detection unit 1 of the second frequency f2 to the first frequency f1 exceeds a predetermined range.

  When the detected portion 2 and the detecting portion 1 are close to each other in the approaching direction S-on and not more than the operating distance, the soft magnetic material of the detecting portion 1 is magnetically saturated and The magnetic permeability μ is close to the air permeability 1 of air. For this reason, in the proximity state, the skin depth d of the alternating current flowing through the detection unit 1 at the first frequency f1 and the second frequency f2 is deeper than in the non-proximity state. As a result, the detection circuit has an impedance component of the detection unit 1 at a current applied to the detection unit 1 at the first frequency f1, and an impedance of the detection unit 1 at a current applied to the detection unit 1 at the second frequency f2. The ratio with the component is detected as a ratio close to 1: 1. In this case, the detection circuit 3 outputs to the notification circuit 5 when the ratio of the impedance component of the detection unit 1 of the second frequency f2 to the first frequency f1 is within a predetermined range. The detection circuit 3 may output the notification circuit 5 when the ratio of the impedance component of the detection unit 1 of the first frequency f1 to the second frequency f2 is within a predetermined range. Based on the output of the detection circuit 3, the notification circuit 5 notifies that the detected unit 2 has approached the detection unit 1 relatively close to the operating distance by light, sound, radio wave transmission, or the like. . As described above, if the detection is performed with the ratio of the impedance component of the second frequency f2 to the first frequency f1, the influence of deterioration of the detection unit 1 is reduced, and the proximity switch according to the fifth embodiment It can be used stably.

  Further, the detection circuit 3 can recognize the maintenance time of the proximity switch according to the fifth embodiment by detecting the ratio of the impedance component of the second frequency f2 to the first frequency f1 in the proximity state. For example, when the performance of the detection unit 1 deteriorates in a high temperature environment, the ratio of the impedance component of the second frequency f2 to the first frequency f1 changes. Therefore, when the ratio of the impedance component of the second frequency f2 to the first frequency f1 exceeds a predetermined threshold, the detection circuit 3 can output to the notification circuit 5 so as to replace the detection unit 1 at an early stage. .

(Embodiment 6)
The proximity switch according to the sixth embodiment includes a detection unit 1, a detected unit 2, a detection circuit 3, and an oscillation circuit 4, as in the first embodiment shown in FIG. Note that the same components as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the proximity switch according to the sixth embodiment, the oscillation circuit 4 can selectively oscillate a plurality of frequencies. For example, the oscillation circuit 4 can alternately oscillate the first frequency f1 and the second frequency f2. The frequency f1 is a frequency at which the skin effect is small and the impedance of the detection unit 1 is low and current flows. The frequency f2 is a frequency at which the skin effect is larger than the frequency f1, the impedance at the detection unit 1 is high, and no current flows. The frequency f2 is higher than the frequency f1.

  As described above, the proximity switch according to the sixth embodiment can obtain the impedance component of the detection unit 1 by the detection circuit 3 even if the oscillation circuit 4 ′ of the fifth embodiment described above is omitted.

  In the proximity switch according to the sixth embodiment, the soft magnetic material of the detection unit 1 is not magnetically saturated when the detected unit 2 and the detection unit 1 are not in proximity. Since the soft magnetic material of the detection unit 1 has a large absolute permeability μ, the above-described skin depth d becomes shallow. For this reason, the currents of the alternating currents flowing through the detection unit 1 at the first frequency f1 and the second frequency f2 are different. The detection circuit 3 includes an impedance component of the detection unit 1 at a current applied to the detection unit 1 at the first frequency f1, and an impedance component of the detection unit 1 at a current applied to the detection unit 1 at the second frequency f2. Is detected as a ratio different from 1: 1. In this case, the detection circuit 3 does not output to the notification circuit 5 because the ratio of the impedance component of the detection unit 1 of the second frequency f2 to the first frequency f1 exceeds a predetermined range.

  When the detected portion 2 and the detecting portion 1 are in the proximity state, the soft magnetic material of the detecting portion 1 is magnetically saturated, and the absolute permeability μ of the detecting portion 1 is close to the air permeability 1 of air. For this reason, in the proximity state, the skin depth d of the alternating current flowing through the detection unit 1 at the first frequency f1 and the second frequency f2 is deeper than in the non-proximity state. As a result, the detection circuit has an impedance component of the detection unit 1 at a current applied to the detection unit 1 at the first frequency f1, and an impedance of the detection unit 1 at a current applied to the detection unit 1 at the second frequency f2. The ratio with the component is detected as a ratio close to 1: 1. In this case, the detection circuit 3 outputs to the notification circuit 5 when the ratio of the impedance component of the detection unit 1 of the second frequency f2 to the first frequency f1 is within a predetermined range. The detection circuit 3 may output the notification circuit 5 when the ratio of the impedance component of the detection unit 1 of the first frequency f1 to the second frequency f2 is within a predetermined range. Based on the output of the detection circuit 3, the notification circuit 5 notifies that the detected unit 2 has approached the detection unit 1 relatively close to the operating distance by light, sound, radio wave transmission, or the like. . As described above, if the detection is performed with the ratio of the impedance component of the second frequency f2 to the first frequency f1, the influence of deterioration of the detection unit 1 is reduced, and the proximity switch according to the sixth embodiment It can be used stably.

  Further, the detection circuit 3 can recognize the maintenance time of the proximity switch according to the sixth embodiment by detecting the ratio of the impedance component of the second frequency f2 to the first frequency f1 in the proximity state. For example, when the performance of the detection unit 1 deteriorates in a high temperature environment, the ratio of the impedance component of the second frequency f2 to the first frequency f1 changes. Therefore, when the ratio of the impedance component of the second frequency f2 to the first frequency f1 exceeds a predetermined threshold, the detection circuit 3 can output to the notification circuit 5 so as to replace the detection unit 1 at an early stage. .

(Evaluation example)
Next, the evaluation example of Embodiment 1 described above will be specifically described with reference to Examples 1 to 5. However, the present invention is not limited to these examples. The absolute magnetic permeability can be obtained by the product of the relative magnetic permeability and the vacuum magnetic permeability (4π × 10 ⁻⁷ H / m).

As a material for the detection part of Example 1, a wire-like Fe ₇₉ B ₁₆ Si ₅ having a diameter of 90 μm wound in a coil shape was prepared, and a magnet as a detection part was brought closer. In a non-proximity state (noted as “no magnet” in Table 1) before bringing the magnet closer, the impedance component Z for an alternating current with a frequency of 13.54 MHz was 3.96Ω. In the proximity state in which the magnets were brought close to each other (indicated as having a magnet in Table 1), the impedance component Z for alternating current at 13.54 MHz was 3.16Ω. The change rate of the impedance component was 20% in the non-proximity state (indicated as “no magnet” in Table 1) and the proximity state (indicated in Table 1 as having a magnet).

As a material for the detection unit of Example 2, a wire-shaped Fe ₆₇ Co ₁₈ B ₁₄ Si ₁ having a diameter of 90 μm wound in a coil shape was prepared, and a magnet was brought close thereto. In a non-proximity state before the magnet was brought close (indicated as “no magnet” in Table 1), the impedance component Z for an alternating current having a frequency of 13.54 MHz was 3.46Ω. In the proximity state in which the magnets were brought close to each other (indicated as having a magnet in Table 1), the impedance component Z with respect to the alternating current having a frequency of 13.54 MHz was 2.88Ω. In the non-proximity state (indicated as “no magnet” in Table 1) and the proximity state (indicated as “with magnet” in Table 1), the change rate of the impedance component was 17%.

As a material for the detection unit of Example 3, a wire-like Fe ₂₂ Ni ₇₈ having a diameter of 90 μm wound in a coil shape was prepared, and a magnet was brought close thereto. In a non-proximity state (noted as “no magnet” in Table 1) before bringing the magnet closer, the impedance component Z for an alternating current with a frequency of 13.54 MHz was 100Ω. In the proximity state in which magnets were brought close to each other (shown as having a magnet in Table 1), the impedance component Z with respect to an alternating current having a frequency of 13.54 MHz was 72Ω. In the non-proximity state (indicated as “no magnet” in Table 1) and the proximity state (indicated as “with magnet” in Table 1), the change rate of the impedance component was 28%. The above Example 1 to Example 3 are shown in Table 1.

As a material for the detection unit of Example 4, a wire-shaped Fe ₇₉ B ₁₆ Si ₅ having a diameter of 90 μm wound in a coil shape was prepared, and a magnet was brought close thereto. In a non-proximity state (noted as “no magnet” in Table 2) before bringing the magnet closer, the impedance component Z for AC at 208 kHz was 1.5Ω. In the proximity state in which the magnets are close (indicated in Table 2 as having magnets), the impedance component Z for AC at 208 kHz was 1.4Ω. The change rate was 7% in the non-proximity state (indicated as “no magnet” in Table 1) and in the close state (indicated as “with magnet” in Table 2). In Example 5, Fe ₂₂ Ni ₇₈ was prepared, and impedance was reduced between a state where no magnet was brought close to the magnet (indicated as “no magnet” in Table 1) and a state where the magnet was brought close (indicated in Table 1 as having a magnet). The rate of change of components was 0%.

As a material for the detection unit of Example 5, a wire-shaped Fe ₂₂ Ni ₇₈ having a diameter of 90 μm wound in a coil shape was prepared, and a magnet was brought close thereto. In a non-proximity state (noted as “no magnet” in Table 2) before bringing the magnet closer, the impedance component Z for AC at 208 kHz was 27Ω. In the proximity state in which the magnets were brought close to each other (shown as having a magnet in Table 2), the impedance component Z for AC at 208 kHz was 13Ω. In the non-proximity state (indicated as “no magnet” in Table 2) and the proximity state (indicated as “with magnet” in Table 2), the change rate of the impedance component was 52%. The above Examples 4 to 5 are shown in Table 2.

  As described above, it has been found that the FeNi alloy is suitable as the detection unit 1.

DESCRIPTION OF SYMBOLS 1, 1A Detection part 2, 2A Detected part 3, 3A Detection circuit 4, 4 'Oscillation circuit 5 Notification circuit 6 Antenna 7 Transmission circuit 8 Reference member 11 Support member 12 Support member 13 Turning part 21 Coil 22 Core S-off Separation direction S-on Approaching direction SW1, SW2 selection switch

Claims (6)

A detection unit made of a magnetic material having conductivity;
A relative distance to the detection unit changes, and a detected unit that applies a magnetic field according to the relative distance to the detection unit;
A detection circuit for detecting a proximity state of the detected portion based on an impedance component of the detection portion according to a change in a magnetic field applied to the detection portion;
Only including,
The detection circuit includes an impedance component of the detection unit at a current applied to the detection unit at a first frequency, and a current applied to the detection unit at a second frequency that is higher than the first frequency. A proximity switch that detects a proximity state of a member to be detected according to a change in a ratio with an impedance component of the detection unit .   The proximity switch according to claim 1, wherein the magnetic material is a soft magnetic material.   The proximity switch according to claim 2, wherein the soft magnetic material is an alloy containing at least iron.   4. The proximity switch according to claim 3, wherein the soft magnetic material is an FeNi alloy further containing nickel.   The proximity switch according to claim 4, wherein the FeNi alloy contains 70 mass% or more of Ni.   The magnetic material of the detection unit is magnetically saturated by the magnetic field of the detection unit when the detection unit and the detection unit are in the proximity state. The proximity switch according to claim 1.

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