JP2011119114A - Proximity sensor oscillated in high frequency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proximity sensor oscillated in high frequency with high sealing property, long detecting distance, wide measuring range, and hardly-influenced detecting capability by a mounting surface. <P>SOLUTION: The proximity sensor 1 oscillated in high frequency oscillates a coil 6 stored in a metal housing 3 shaped in a bottomed cylinder by an oscillation circuit 8 at a high frequency, applies an alternating magnetic field to a detection object 2 through a housing detection surface 7 crossing the central line of the coil 6, and by an eddy current generated in the detection object 2, detects the presence of the detection object 2 in a noncontact mode through variation in magnetic flux crossing the coil 6. Each of a magnetic-material region 13 and a nonmagnetic-material region 14 is formed in the housing 3 at least on the housing detection surface 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high-frequency oscillation type proximity sensor, and more particularly to an improvement in detection distance and detection sensitivity of an inductive proximity sensor or an eddy current displacement sensor.

High-frequency oscillation type proximity sensors are used in all industrial fields such as machine tools, conveyance machines, and food machines. When the proximity sensor is mounted, the distance to the target (detection body, detection target, detection object), parallelism, etc. will greatly affect the detection sensitivity and accuracy. If the target touches the detection surface of the proximity sensor in the automobile, transportation industry, etc. Therefore, it is likely to cause breakage and failure, so that it is required to increase the detection distance. Further, in order to protect the proximity sensor from fine particles scattered during gas welding and arc welding, a proximity sensor having a stainless steel housing has been developed. However, the proximity sensor whose detection surface is made of stainless steel has a strong detection distance because of the short detection distance.
Furthermore, eddy current type displacement sensors having a stainless steel housing are also widely used in machine tools and the like, and it is strongly desired to expand the measurement range for the same reason as described above.

  As an example of a high-frequency oscillation type proximity sensor, a core in which an annular groove is formed is accommodated in a cylindrical nonmagnetic metal housing, and a coil is formed in the core groove toward the detection surface of the detected object. Is wrapped around. The detection surface of the metal case is covered with a synthetic resin protective cap.

When excitation current flows from the oscillation circuit to the coil, magnetic flux F is generated. When this magnetic flux F acts on a metal target, an eddy current I _e flows through the target according to the law of electromagnetic induction. Since the amount of magnetic flux changes according to the displacement x between the target and the detection surface, the eddy current I _e flowing through the target changes, and as a result, the coil impedance (coil resistance R, inductance L, and Q value) changes. As a result, the output voltage of the oscillation circuit changes.

In the case of an inductive proximity sensor, the output voltage of the oscillation circuit is compared with the reference voltage in the comparison circuit, thereby generating a binary ON or OFF signal based on the change in the impedance of the coil, and the signal is transmitted through the output circuit. _Is output as an output voltage V _s corresponding to. The displacement at which the level of the output voltage V _s is switched ON or OFF is the detection distance S.

In the case of an eddy current displacement sensor, the output signal from the oscillation circuit is converted by the linearizer so as to be proportional to the displacement x, and is output as the output voltage V _s through the output circuit. The range in which the output voltage V _s is proportional to the displacement x is the measurement range X.

JP 2007-74519 A JP 2004-119370 A

However, in the above-described high-frequency oscillation type proximity sensor, the detection surface of the metal housing is covered with a protective cover made of resin, which may be difficult to use depending on the usage environment of the sensor, for example.
For example, when it is provided on a production site line involving welding or the like, a spark may fly and the protective cover may be damaged. Moreover, in the food processing field, water, fruit juice, etc. easily enter the gaps between different members, and there is anxiety in the management of hygiene such as the sealing property of the sensor detection surface and the propagation of bacteria.
Further, since eddy current flows also in the metal housing, the impedance of the coil changes and the detection distance S and the measurement range X are shortened. Therefore, in order to lengthen the detection distance S and the measurement range X, a large core outer diameter, that is, a large proximity sensor is required.

  Further, the proximity sensor has a spiral threaded portion formed on the outer peripheral surface of the metal housing, and is assembled by screwing into a screw hole provided on an attachment surface made of a metal plate. Since the magnetic flux F of the sensor also acts on this metal plate and an eddy current is generated, the detection distance S and the measurement range X vary depending on the material properties (magnetic permeability and resistivity) and thickness of the metal plate. For this reason, it has also been desired that the detection distance S and the measurement range X do not depend on the characteristics of the mounting surface.

  An object of the present invention is to provide a high-frequency oscillation type proximity sensor that solves the above-described problems, has high sealing performance, has a long detection distance and measurement range, and is less susceptible to detection performance due to the mounting surface.

In order to solve the above problems, the present invention provides the following means.
A coil housed in a bottomed cylindrical metal housing is driven to oscillate at a high frequency by an oscillation circuit, and an alternating magnetic field is applied to the object to be detected through a housing detection surface that intersects the center line of the coil. A high-frequency oscillation type proximity sensor that detects the presence of an object to be detected in a non-contact manner through a change in magnetic flux interlinked with the coil by an eddy current that is generated, wherein the housing has at least a magnetic region and a non-magnetic region on the housing detection surface. Each of the magnetic regions is formed.

  Further, a magnetic body region is formed in at least a region facing the inner diameter region of the coil in the housing detection surface.

  In addition, a housing side surface in which a screw portion that is screw-fitted to the mounting surface is formed on the outer peripheral surface is formed in the magnetic region.

  Further, the metal housing is formed by plastically deforming a predetermined portion of an austenitic stainless steel plate that has been demagnetized by heat treatment into a bottomed cylindrical shape to develop a ferromagnetic martensite phase by processing-induced transformation, thereby detecting the housing. A magnetic material region is formed on the substrate.

  Further, the metal housing is formed by plastically deforming a ferromagnetic martensitic stainless steel plate into a bottomed cylindrical shape, and heating a predetermined portion to cause a heat transformation to develop a nonmagnetic austenite phase. A magnetic region is formed.

  The metal housing is characterized in that a ferromagnetic stainless steel forming a magnetic region and a nonmagnetic stainless steel forming a nonmagnetic region are joined in a bottomed cylindrical shape.

  An oscillation circuit that generates an alternating magnetic field through the housing detection surface by energizing the coil, a comparison circuit that generates an ON or OFF signal based on an output voltage of the oscillation circuit, and an output of the comparison circuit are amplified. And an inductive proximity sensor including an output circuit.

  Further, an oscillation circuit that generates an alternating magnetic field through a housing detection surface by energizing the coil, a linearizer that linearly corrects the output of the oscillation circuit, and an output circuit that amplifies the linear output of the linearizer are provided. It is used as an eddy current type displacement sensor.

If the above-described high-frequency oscillation type proximity sensor is used, at least the magnetic substance region and the non-magnetic material region are formed on the housing detection surface, so that more magnetic flux generated by energizing the coil is generated in the magnetic material region. It becomes possible to act on the target further through. Therefore, without increasing the size of the proximity sensor, it is possible to increase the detection distance and the measurement range by increasing the sensitivity even if the proximity sensor is small.
In addition, the coil housed in a bottomed cylindrical metal housing is driven to oscillate at a high frequency by an oscillation circuit, and an alternating magnetic field is applied to the object to be detected via the housing detection surface that intersects the center line of the coil. And is not easily affected by the environment in which the sensor is used, and can improve versatility.

  In addition, when the housing side surface in which the screw portion that is screw-fitted to the mounting surface is formed on the outer peripheral surface is formed in the magnetic body region, the housing side surface that is the magnetic body region magnetically shields the magnetic flux generated by the coil. A stable detection distance and measurement range can be obtained without depending on the material characteristics (permeability and resistivity) and thickness of the metal plate to which the screw portion is attached.

  In addition, the housing can be formed integrally with the magnetic region and the non-magnetic region at a low cost on the housing detection surface regardless of whether non-magnetic or ferromagnetic stainless steel is used. In addition, since the magnetic material region is formed at a predetermined portion of the housing detection surface and the magnetic flux is induced in the magnetic material region, the thickness of the housing can be increased, so that high reliability is achieved. It is possible to provide an inductive proximity sensor and an eddy current type displacement sensor having the characteristics.

FIG. 3 is a structural diagram of an inductive proximity sensor according to the present invention. FIG. 3 is a structural diagram of an inductive proximity sensor head according to the present invention to which a finite element method is applied and an inductive proximity sensor head according to a comparative example. It is the figure which showed the resistance R-displacement x characteristic, the inductance L-displacement x characteristic, and the Q value-displacement x characteristic of the coil 6 of the proximity sensor which concerns on this invention, and the proximity sensor which concerns on a comparative example. It is the figure which showed resistance _Rt (x) -displacement characteristic resulting from the eddy current loss which arises in the target of the proximity sensor which concerns on this invention, and the proximity sensor which concerns on a comparative example. It is the figure which showed the Colpitts oscillation circuit set to the electronic circuit simulator of the proximity sensor which concerns on this invention, and the proximity sensor which concerns on a comparative example. Output voltage V _o of the proximity sensor according to a comparative example with the present invention - is a graph showing the displacement x characteristic. The sensitivity dV o _/ DX displacement x characteristic of the proximity sensor according to a comparative example with the present invention is a graph showing. It is the figure which showed the other Example of the inductive proximity sensor concerning embodiment of this invention. It is the figure which showed the other Example of the inductive proximity sensor concerning embodiment of this invention. It is the figure which showed the structure of the eddy current type displacement sensor concerning embodiment of this invention. It is the figure which showed the other Example of the eddy current type displacement sensor concerning embodiment of this invention. It is the figure which showed the other Example of the eddy current type displacement sensor concerning embodiment of this invention. It is the schematic which shows an example of the manufacturing method of a housing. It is the schematic which shows the other example of the manufacturing method of a housing.

[Example 1]
Hereinafter, an inductive proximity sensor will be described in detail as an example of a high-frequency oscillation type proximity sensor according to the present invention with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the structure of the inductive proximity sensor 1.

  The inductive proximity sensor 1 drives a coil 6 housed in a bottomed cylindrical metal housing 3 with high frequency oscillation by an oscillation circuit 8 and is detected via a housing detection surface 7 intersecting the center line M of the coil 6. An alternating magnetic field is applied to the object (target) 2 and the presence of the object (target) 2 is detected in a non-contact manner through a change in magnetic flux linked to the coil 6 due to an eddy current generated in the object (target) 2. This is a high-frequency oscillation type proximity sensor.

  The housing 3 has at least a magnetic region 13 and a nonmagnetic region 14 formed on the housing detection surface 7. Specifically, the magnetic body region 13 is formed in a region of the housing detection surface 7 facing at least the inner diameter region of the coil 3. In addition, the side surface of the housing 3 in which the screw portion 4 that is screw-fitted to the mounting surface is formed on the outer peripheral surface is formed in the magnetic region 13. The coil 6 is wound around the groove 5 a of the core 5 provided with the groove 5 a facing the housing detection surface 7.

When the excitation current I flows from the oscillation circuit 8 to the coil 6, a magnetic flux F is generated. When this magnetic flux F acts on the metal target 2, an eddy current _Ie flows through the target 2 according to the law of electromagnetic induction. Since the amount of magnetic flux changes according to the displacement x between the target 2 and the housing detection surface 7, the eddy current _Ie flowing through the target 2 changes, and as a result, the impedance of the coil 6 (resistance R and inductance of the coil 6). (L and Q values) change, and the output voltage of the oscillation circuit 8 changes. By comparing this change with the reference voltage in the comparison circuit 9, a binary ON or OFF signal is generated and output as the output voltage V _s through the output circuit 10. The displacement x at which the level of the output voltage V _s is switched ON or OFF is the detection distance S. The presence of the magnetic region 13 provided in a part of the housing detection surface 7 increases the detection distance S because more magnetic flux F acts on the target 2 farther.

  Furthermore, the screw part 4 which is the side surface of the housing 3 is composed of the magnetic body region 13, and a metal plate to which the screw part 4 is attached so that the magnetic body region 13 magnetically shields the magnetic flux F generated by the coil 6 (see FIG. A stable detection distance S can be obtained without depending on the material properties (magnetic permeability and resistivity) and thickness of the material (not shown).

  Here, an example of the structure of the housing 3 will be described together with its manufacturing method. In FIG. 13, the housing 3 is made of an austenitic stainless steel plate (eg, SUS303, SUS304, etc.) that has been rendered non-magnetic by heat treatment. A magnetic region 13 is formed by plastically deforming a predetermined portion of the housing 3 to develop a ferromagnetic martensite phase by processing-induced transformation.

Specifically, as shown in FIG. 13, an austenitic stainless steel plate demagnetized by heat treatment is drawn into a bottomed cylindrical shape, and threaded on the side of the housing to form the threaded portion 4. Form. After that, while the housing 3 is held by the holding jig 15, pressing is performed while rotating the pressing tool 16 to a predetermined portion of the housing detection surface 7 (in a region facing the inner diameter region of the coil 3), and strong by processing-induced transformation. A magnetic martensite phase is developed to form a magnetic region 13 on a part of the housing detection surface 7.
The threaded portion 4 may be formed by performing threading after the magnetic body region 13 is formed.

  Next, FIG. 14 explains a structure according to another example of the housing 3 together with its manufacturing method. The housing 3 of the present embodiment uses a ferromagnetic martensitic stainless steel plate (for example, SUS403, SUS410, etc.), heats a predetermined portion to cause a heat transformation, and develops a nonmagnetic austenite phase. A nonmagnetic region 13 is formed.

Specifically, as shown in FIG. 14, the threaded portion 4 is threaded after a ferromagnetic martensitic stainless steel plate is drawn into a bottomed cylindrical shape by press working.
Thereafter, the housing 3 is rotated while being held by the holding jig 15, and a predetermined portion (outside the magnetic region) of the housing detection surface 7 is irradiated with laser light 18 from the laser generator 17 while scanning in the radial direction. A non-magnetic austenite phase is developed by thermal modification of ferromagnetic martensitic stainless steel, so that a non-magnetic region 14 is formed on the housing detection surface 7. The threaded portion 4 may be formed by performing threading after the non-magnetic region 14 is formed.

  Furthermore, as another example of the housing 3, it is possible to join a ferromagnetic stainless steel forming the magnetic region 13 and a nonmagnetic stainless steel forming the nonmagnetic region 14. is there.

  Next, the analysis results of the detection distance of the sensor head unit according to the present invention by applying numerical electromagnetic field analysis software (finite element method) and the sensor head unit according to the comparative example will be described in comparison.

  FIG. 2A shows a housing 3 according to a comparative example, and the housing detection surface 7 is made of a nonmagnetic material. FIG. 2B shows the housing 3 according to the present invention, in which a magnetic region 13 and a nonmagnetic region 14 are formed on the housing detection surface 7. The dimensions of the metal housing 3 are M12 size (19 × 10), the thickness of the housing 3 is 1 mm, and the target 2 is a cold rolled steel plate SPCC having a diameter of 25 mm and a thickness of 1 mm. The copper wire of the coil 6 has a conductor diameter of 0.08 mm and the number of coil turns of 100, and the structure was input for each copper wire.

Table 1 shows the analysis conditions of the finite element method. Magnetic region relative permeability m _r = 100 in the housing 3, the resistivity r = 0.72mWm, relative permeability m _r = 1 in the non-magnetic region, and a resistivity r = 0.72mWm. Further, assuming that the cold rolled steel plate SPCC was used as the target 2, the relative permeability m _r = 289 and the resistivity r = 0.14 mWm were set. Further, the complex permeability m ′ and m ″ of the core were input. The impedance of the coil 6 in the frequency range of the excitation current from 10 kHz to 100 kHz was determined.

  3A and 3B show the characteristics of the comparative example obtained by the finite element method and the proximity sensor according to the present invention. FIG. 3A shows the resistance R-displacement x characteristics of the coil 6, and FIG. 3B shows the inductance L-displacement. FIG. 3C shows the x characteristic and the Q value-displacement x characteristic. In the analysis result of the finite element method, in both the comparative example and the present invention, the frequency of the excitation current that maximizes the Q value of the coil 6 is 40 kHz, and FIG. 3 shows the characteristics at the frequency of 40 kHz. As shown in FIG. 3A, the resistance R of the coil 6 monotonously decreased with respect to the displacement x. Further, as shown in FIG. 3B, the inductance L was constant with respect to the displacement x. Therefore, as shown in FIG. 3C, the Q value of the coil 6 monotonously increased with respect to the displacement x. Note that the Q value of the coil is expressed by Equation 1, and the resistance R (x) of the coil depending on the displacement x is expressed by Equation 2.

Here, f: frequency of excitation current (Hz), L: inductance of coil 6 (H), R _dc : DC resistance of coil 6 (Ω), R _s : resistance caused by skin effect of coil 6 conductor ( Ω), R _p : resistance due to proximity effect of the coil 6 (Ω), R _c : resistance due to iron loss of the core 5 (Ω), R _h : resistance due to eddy current loss generated in the housing 3 (Ω) Ω), R _t (x): resistance (Ω) due to eddy current loss generated in the target 2 depending on the displacement x.

As shown in FIG. 3B, the inductance L of the coil 6 is constant regardless of the displacement x. Further, the DC resistance R _{dc of} the coil 6, the resistance R _s due to the skin effect of the coil 6, the resistance R _p due to the proximity effect of the coil 6, the resistance R _c due to the iron loss of the core 5, and the housing 3 are generated. The resistance R _h caused by the eddy current loss is also constant regardless of the displacement x, and only the resistance R _t (x) caused by the eddy current loss of the target 2 depends on the displacement x. Therefore, increasing the resistance R _t (x) due to the eddy current loss generated in the target 2 with respect to the displacement x leads to an increase in the detection distance S.

The resistance R _t (x) due to the eddy current loss generated in the target 2 is given by the following _equation (3). The resistance R _t (x) caused by the eddy current loss generated in the target 2 is the AC resistance of the coil 6 when the displacement x is infinite from the AC resistance R (x) of the coil 6 when the displacement x is at an arbitrary position. The value is obtained by subtracting R (∞).

FIG. 4 shows the resistance R _t (x) -displacement x characteristics resulting from the eddy current loss of the target 2 of the proximity sensor 1 according to the present invention and the comparative example. The resistance R _t (x) due to the eddy current loss of the target 2 decreased monotonously with the displacement x. This monotonic decrease is caused by a decrease in the magnetic flux F acting on the target 2 as the displacement x increases. Comparing the resistance R _t (x) due to the eddy current loss of the target 2 of the present invention and comparative example, is larger than the comparative example towards the resistance R _t (x) due to the eddy current loss of the target 2 of the present invention . This is because more magnetic flux F acts on the target 2 farther due to the presence of the magnetic region 13 (magnetic flux path) provided in a part of the housing detection surface 7.

FIG. 5 shows a Colpitts oscillation circuit 19 used for the oscillation circuit 8. The value of the resistor R and the inductance L of the coil 6 of the structure and the present invention of the comparative example obtained by the finite element method to input to the circuit simulator to obtain the output voltage V _o corresponding to the displacement x of the target 2.

Table 2 shows circuit parameters of the Colpitts oscillation circuit 19 shown in FIG. The structure of the comparative example and each circuit parameter of the proximity sensor of the present invention were set so that the output voltage V _o = 500 mV was constant when the oscillation frequency of the Colpitts oscillation circuit 19 was 40 kHz and the displacement x → ∞.

FIG. 6 shows the output voltage V _o -displacement x characteristics in the comparative example and the proximity sensor of the present invention. Output voltage V _o is monotonously increased with respect to the displacement x.

FIG. 7 shows the detection sensitivity dV _o / dx-displacement x characteristics of the comparative example and the proximity sensor according to the present invention. This figure was obtained by approximating the output voltage V _o -displacement x characteristic data of the comparative example shown in FIG. 6 and the proximity sensor according to the present invention with a 6th order polynomial and differentiating with the displacement x. In order to improve the detection distance S, it is necessary to generate stable ON and OFF signals in the comparison circuit 9. In other words, it is essential to improve the detection sensitivity dV _o / dx. Based on the sensitivity dV _o / dx = 28 V / mm at the detection distance S = 2.0 mm in the comparative example, the detection distance in the present invention was S = 2.5 mm. That is, in the proximity sensor of the present invention, the detection distance S is increased by 1.25 times compared to the comparative example. This is because a larger amount of magnetic flux F acts on the target 2 farther due to the presence of the magnetic region 13 (magnetic flux path) provided in a part of the housing detection surface 7.

  Further, the screw part 4 is composed of the magnetic body region 13, and the material of the metal plate (not shown) to which the screw part 4 is attached so that the magnetic body region 13 magnetically shields the magnetic flux F generated by the coil 6. A stable detection distance S can be obtained without depending on characteristics (magnetic permeability and resistivity) and thickness.

[Example 2]
FIG. 8 shows another example of the inductive proximity sensor 1 according to the embodiment of the present invention. Only the screw portion 4 which is the outer peripheral edge portion of the housing detection surface 7 is used as the magnetic region 13. Since the magnetic region 13 magnetically shields the magnetic flux F generated by the coil 6, it does not depend on the material properties (permeability and resistivity) and thickness of the metal plate (not shown) to which the screw portion 4 is attached. A stable detection distance S is obtained.

[Example 3]
FIG. 9 shows another embodiment of the inductive proximity sensor 1. In this embodiment, only a part of the housing detection surface 7 (a region facing the core 5) is used as the magnetic region 13, and the other part is a non-magnetic region 14. As in the first embodiment, the presence of the magnetic region 13 provided in a part of the housing detection surface 7 causes more magnetic flux F to act on the target 2 further, and the detection distance S is improved.

[Example 4]
FIG. 10 shows an embodiment of the eddy current displacement sensor 11 which is an example of a high frequency oscillation type proximity sensor.
A coil 6 is built in a stainless steel housing 3. When the excitation current I flows from the oscillation circuit 8 to the coil 6, a magnetic flux F is generated. When this magnetic flux F acts on the metal target 2, an eddy current _Ie flows through the target 2 according to the law of electromagnetic induction. Since the amount of magnetic flux changes according to the displacement x between the target 2 and the housing detection surface 7, the eddy current _Ie flowing through the target 2 changes, and as a result, the resistance R, inductance L, and Q value of the coil 6 change. Change. The output signal from the oscillation circuit 8 is converted by the linearizer 12 so as to be proportional to the displacement x, and is output as the output voltage V _s through the output circuit 10. The range in which the output voltage V _s is proportional to the displacement x is the measurement range X.
Even when the coil 6 is an oscillating element, the eddy current I _e flowing through the target 2 changes, and as a result, the resistance R, inductance L, and Q value of the coil 6 change, and the output voltage V _s is proportional to the displacement x. The range is the measurement range X.

  Similar to the inductive proximity sensor 1 shown in the first embodiment, the presence of the magnetic region 13 provided in a part of the housing detection surface 7 causes more magnetic flux F to act on the target 2 farther. The measurement range X is improved. Further, the screw part 4 is composed of the magnetic body region 13, and the material of the metal plate (not shown) to which the screw part 4 is attached so that the magnetic body region 13 magnetically shields the magnetic flux F generated by the coil 6. A stable measurement range X can be obtained without depending on characteristics (permeability and resistivity) and thickness.

[Example 5]
FIG. 11 shows another embodiment of the eddy current type displacement sensor 11. Similar to the inductive proximity sensor 1 shown in the second embodiment, only the screw portion 4 (outer peripheral edge portion of the housing detection surface 7) is configured by the magnetic region 13, and the magnetic flux F generated by the coil 6 is used as the magnetic region. Since 13 is magnetically shielded, a stable measurement range X can be obtained without depending on the material properties (permeability and resistivity) and thickness of the metal plate (not shown) to which the screw portion 4 is attached.

[Example 6]
FIG. 12 shows another embodiment of the eddy current type displacement sensor 11. Similar to the inductive proximity sensor 1 shown in the third embodiment, the presence of the magnetic region 13 provided in a part of the housing detection surface 7 causes more magnetic flux F to act on the target 2 farther. The measurement range X is improved.

  In the embodiment of the inductive proximity sensor, the housing 3 coil 6 is built in the core 5. However, the present invention is not limited to this. The core 5 may be omitted and only the coil 6 may be used.

  In the embodiment of the eddy current displacement sensor, only the coil 6 is provided in the housing 3 and the coil core 5 is omitted. However, the present invention is not limited to this, and the coil 6 is built in the core 5. Also good.

DESCRIPTION OF SYMBOLS 1 Proximity sensor 2 Target 3 Housing 4 Screw part 5 Core 6 Coil 7 Housing detection surface 8 Oscillation circuit 9 Comparison circuit 10 Output circuit 11 Eddy current type displacement sensor 12 Linear riser 13 Magnetic body area | region 14 Nonmagnetic body area | region 15 Holding jig 16 Pressing tool 17 Laser generator 18 Laser light 19 Colpitts oscillation circuit

Claims (8)

A coil housed in a bottomed cylindrical metal housing is driven to oscillate at a high frequency by an oscillation circuit, and an alternating magnetic field is applied to the object to be detected through a housing detection surface that intersects the center line of the coil. A high-frequency oscillation type proximity sensor that detects the presence of an object to be detected in a non-contact manner through a magnetic flux change linked to the coil by an eddy current generated,
The housing is a high-frequency oscillation type proximity sensor in which at least a magnetic material region and a non-magnetic material region are formed on the housing detection surface.   The high-frequency oscillation proximity sensor according to claim 1, wherein a magnetic material region is formed in at least a region of the housing detection surface facing an inner diameter region of the coil.   The high-frequency oscillation type proximity sensor according to claim 1 or 2, wherein a housing side surface in which a screw portion to be screwed to the mounting surface is formed on the outer peripheral surface is formed in the magnetic body region.   The metal housing is formed on the detection surface of the housing by plastically deforming a predetermined portion of an austenitic stainless steel plate demagnetized by heat treatment into a bottomed cylindrical shape and developing a ferromagnetic martensite phase by processing-induced transformation. The high frequency oscillation type proximity sensor according to any one of claims 1 to 3, wherein a magnetic body region is formed.   The metal housing is made of a non-magnetic material by plastically deforming a ferromagnetic martensitic stainless steel plate into a bottomed cylindrical shape and heating a predetermined portion to cause a heat transformation to develop a non-magnetic austenite phase. The high-frequency oscillation type proximity sensor according to any one of claims 1 to 3, wherein a region is formed.   4. The metal housing is formed by joining a ferromagnetic stainless steel forming a magnetic region and a nonmagnetic stainless steel forming a non-magnetic region in a bottomed cylindrical shape. 5. The high-frequency oscillation type proximity sensor described.   An oscillation circuit that generates an alternating magnetic field through the housing detection surface by energizing the coil, a comparison circuit that generates an ON or OFF signal based on an output voltage of the oscillation circuit, and an output that amplifies the output of the comparison circuit A high-frequency oscillation type proximity sensor according to any one of claims 1 to 6, which is used as an inductive proximity sensor including a circuit.   An eddy circuit comprising: an oscillation circuit that generates an alternating magnetic field through the housing detection surface by energizing the coil; a linearizer that linearly corrects the output of the oscillation circuit; and an output circuit that amplifies the linear output of the linearizer The high-frequency oscillation type proximity sensor according to any one of claims 1 to 6, which is used as a current source displacement sensor.

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