Inductive proximity sensor

Abstract

This invention provides an inductive proximity sensor. The detection surface of the inductive proximity sensor is protected. The inductive proximity sensor (100) includes, for example: a detection coil (20) that generates a magnetic field-based detection signal; a cylindrical housing (10) that houses the detection coil (20) with the detection surface (17) as its bottom surface; and a cover-like metal member (96) that is detachable from the housing (10) and covers the detection surface (17) when mounted on the housing (10). When the housing (10) is mounted to a mounting member (E) having a through hole, with the housing (10) positioned inside the through hole, the cover-like metal member (96) is mounted on the housing (10) from the side where the detection surface (17) is located relative to the mounting member (E).

Description

Technical Field

[0001] This invention relates to an inductive proximity sensor. Background Technology

[0002] Previously, there were known inductive proximity sensors that generated a magnetic field and detected the approach of a detection object (metal body) by changing the magnetic field (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 02 / 075763

[0006] Patent Document 2: Japanese Patent Application Publication No. 2018-205096 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] Furthermore, the detection results of inductive proximity sensors can sometimes be altered by metallic objects other than the object being detected, located near the detection surface. For example, the detection result may change due to sputtering material adhering to the detection surface. Additionally, inductive proximity sensors are often used to detect moving objects. In this case, the detection surface may be damaged due to contact between the object and the detection surface.

[0009] Furthermore, components used to cover the detection surface of proximity sensors have also existed in the past (e.g., housing 30 according to Patent Document 2). However, such components are merely for improving the installability of the proximity sensor. Therefore, no structure has been developed that takes into account the replacement of the component itself.

[0010] In view of the above problems, the main objective of the present invention is to provide an inductive proximity sensor that can protect the detection surface.

[0011] Solution for solving the problem

[0012] For example, the inductive proximity sensor according to the present invention includes:

[0013] A detection coil that generates a detection signal based on a magnetic field;

[0014] A cylindrical housing that houses the detection coil, with the detection surface as its bottom surface; and

[0015] A cap-shaped metal component, detachable from the housing, covers the detection surface when installed on the housing.

[0016] When the housing is installed onto a mounting member having a through hole, with the housing positioned inside the through hole, the cap-shaped metal member is installed onto the housing from the side where the detection surface is located relative to the mounting member.

[0017] Furthermore, other features, elements, steps, advantages, and characteristics become clearer through the following detailed description and the accompanying drawings.

[0018] The effects of the invention

[0019] According to the present invention, an inductive proximity sensor capable of protecting the detection surface can be provided. Attached Figure Description

[0020] Figure 1 This is a diagram showing the overall structure of the proximity sensor.

[0021] Figure 2 This is a diagram showing an example of a proximity sensor setup.

[0022] Figure 3 This is a diagram showing the shape of the proximity sensor.

[0023] Figure 4 This is a diagram showing the XZ cross-section of the proximity sensor.

[0024] Figure 5 This is a diagram showing the functional blocks of the sensor unit.

[0025] Figure 6 This is a diagram showing the YZ cross-section of the proximity sensor (particularly the periphery of the operating section).

[0026] Figure 7 It is a diagram showing the XY cross-section of the proximity sensor (especially the periphery of the operating part).

[0027] Figure 8 It is a graph showing the relationship between frequency and skin depth for various metallic materials.

[0028] Figure 9 This is a diagram illustrating the effect of the magnetic shielding component.

[0029] Figure 10 This is a diagram illustrating the detection principle of the inductive (pulse) type.

[0030] Figure 11 This is a diagram showing the received waveform of a dual-coil type.

[0031] Figure 12 This is a diagram showing the XZ section of a cap nut.

[0032] Figure 13This is a diagram showing the outline of teaching through metal.

[0033] Figure 14 This is a diagram showing the detector signal before and after teaching through the metal.

[0034] Figure 15 This is a diagram showing the display modes corresponding to the relative distance between the proximity sensor and the object being detected.

[0035] Figure 16 This is a diagram showing the state transitions of the proximity sensor.

[0036] Figure 17 This is a diagram showing an overview of the display modes in the display unit.

[0037] Figure 18 This is a timing diagram showing the display modes in the display unit.

[0038] Figure 19 This is a diagram showing the switching of operating modes corresponding to the location of the proximity sensor.

[0039] Figure 20 This is a diagram showing a first variant of the proximity sensor.

[0040] Figure 21 This is a diagram showing the shape of the proximity sensor in the first modified example.

[0041] Figure 22 This is a diagram showing a second variation of the proximity sensor. Detailed Implementation

[0042] <Proximity Sensor>

[0043] Figure 1 This is a diagram showing the overall structure of the proximity sensor 100. The proximity sensor 100 detects the presence and proximity of a detection object D in a non-contact manner. The proximity sensor 100 can also be a pulse-type inductive proximity sensor that uses an excitation current with a pulse waveform. In this case, the detection object D can be, for example, a metal body. As described in this figure, the proximity sensor 100 includes a sensing head 101. Furthermore, if the sensing head 101 is the only constituent element of the proximity sensor 100, the proximity sensor 100 can also be understood as the sensing head 101 itself.

[0044] The sensor head 101 generates a magnetic field at a predetermined period and acquires the change in current generated by the magnetic field as a detection signal. The sensor head 101 detects the presence or absence of the detection object D and the corresponding change in the detection signal, i.e., the change in the received waveform. The sensor head 101 outputs the binary (ON / OFF) detection result to the external device 200. The external device 200 may be, for example, a PLC (Programmable Logic Controller). The sensor head 101 and the external device 200 may also be physically separable through the installation and removal of connectors.

[0045] Next, refer to Figures 2-4 To illustrate the specific structure of the proximity sensor 100. Figure 2 This is a diagram showing an example of the installation of the proximity sensor 100. Figure 3 This is a diagram showing the shape of the proximity sensor 100, or in other words, the shape of the sensor head 101. Figure 4 This is the XZ cross-sectional view of proximity sensor 100. Figure 4 It can also be understood as Figure 2 PP cross-sectional view.

[0046] The proximity sensor 100 comprises a housing 10, a coil 20, a ferrite core 30, a core holder 40, a substrate 50, an electrical shield 80, a magnetic shield 90, a resin cover 95, and a cap-shaped nut 96 as its main components. Hereinafter, the coil 20, ferrite core 30, core holder 40, and substrate 50 are sometimes collectively referred to as the sensor unit 25.

[0047] In addition, such as Figure 4 As schematically shown by the dashed box, a detection unit 26 may also be mounted on the substrate 50. This detection unit 26 detects the detection body D based on a detection signal generated in the coil 20. This detection signal may also be a change in voltage or current generated in the coil 20 over time. The detection unit 26 may also include, for example, a receiving circuit 60 and a control circuit 76, described later.

[0048] The outer casing 10 can be understood as a housing that accommodates the coil 20. The outer casing 10 has a main body portion 11 with external threads 12. The main body portion 11 can be understood as a cylindrical member with its second end S2 opening in the Z-axis direction in the normal direction of the detection surface 17. Hereinafter, the first end S1 is sometimes referred to as the front end, and the second end S2 is sometimes referred to as the base end. In addition, the direction along the Z-axis direction from the second end S2 toward the first end S1 is sometimes referred to as the +Z direction, and the direction from the first end S1 toward the second end S2 is sometimes referred to as the -Z direction. The main body portion 11 completely covers the magnetic shield 90, the electrical shield 80, and the sensor unit 25 in its circumference. The external threads 12 may also be formed on a portion of the outer circumference of the main body portion 11 as shown in this figure. Alternatively, the external threads 12 may be formed on the entire circumference of the main body portion 11 from the first end S1 to the second end S2. Furthermore, the main body portion 11 may also be composed of a cylindrical member with openings at both the first end S1 and the second end S2.

[0049] A resin cap 95 is inserted and fitted at the first end S1 of the main body 11 of the housing. The bottom surface of the resin cap 95 can be understood as the detection surface 17 of the proximity sensor 100. That is, the outer surface of the detection surface 17 faces the detection body D through the cap-shaped nut 96, and the inner surface faces the coil 20. Thus, the housing 10, which corresponds to the housing of the proximity sensor 100, can be understood as a cylindrical member with the detection surface 17, located between the detection body D detected by the detection unit 26 and the coil 20, as its bottom surface. On the other hand, the housing base end 13 is inserted and fitted at the second end S2 of the main body 11 of the housing. In this embodiment, in order to make the main body 11 of the housing with metal and the detection surface 17 with resin, the resin cap 75 including the detection surface 17 is configured as a different component from the main body 11 of the housing. Furthermore, the component constituting the detection surface is configured as a different component from the main body 11 of the housing, thereby having advantages related to the processing of the housing 10. In this case, a cap component made of metal can also be inserted and fitted into the main body 11 of the housing instead of the resin cap 95. As an example of its advantages, the first end S1 of the outer casing body 11 can be machined to be thinner more easily, thus increasing the space available for arranging the coil 20. In addition, since the cover member itself can be machined with high precision at a relatively low cost, the influence of deviations in the coil arrangement position caused by machining deviations and the thickness of the detection surface on the coil detection results can be reduced.

[0050] An operation unit 15 is provided in the outer casing 10. The operation unit 15 accepts user operations for adjusting the detection method of the detection unit 26. For example, the operation unit 15 functions as a receiving unit, accepting the selection of any one of multiple modes that are different operating modes of the detection unit 26 and different detectable distances of the detection body D. In addition, the operation unit 15 can also accept user teaching operations. The teaching operation will be described in detail later.

[0051] Additionally, a display unit 16 is provided on the housing 10. The display unit 16 displays the current setting state of the detection method after changes based on the operation received by the operation unit 15. For example, the display unit 16 functions as a notification unit to inform the user of the operating mode of the detection unit 26. The display unit 16 can be installed, for example, by turning part or all of the housing base 13 on and off with any light emission color. In this case, the display unit 16 may also include a light-emitting element such as an LED (Light Emitting Diode).

[0052] Furthermore, the operation unit 15 and the display unit 16 may also be provided on the side opposite to the detection surface 17 with respect to the external thread 12, i.e., the base end side, in the normal direction of the detection surface 17, or the Z-axis direction in this figure. In terms of arrangement order, the components may be arranged from the front end side of the housing 10 toward the base end side in the order of detection surface 17, external thread 12, operation unit 15 and display unit 16.

[0053] In other words, the detection surface 17 is provided at the first end S1 of the housing 10. On the other hand, the display unit 16 is provided at the second end S2 of the housing 10. In addition, the operation unit 15 is provided at a position closer to the second end S2 than the midpoint S3 between the first end S1 and the second end S2, that is, at the base end side.

[0054] The proximity sensor 100 also includes a cable 19. One end of the cable 19 is electrically connected to the substrate 50. The cable 19 extends outward from the substrate 50 through the cable mounting port 14 at the base end 13 of the housing 10. The other end of the cable 19 is disposed outside the housing 10 and connected to an external device 200.

[0055] Coil 20 functions as a detection coil that generates a magnetic field through an excitation current and produces a detection signal based on the magnetic field. Coil 20 can also be housed inside the main body 11, particularly near the first end S1. Coil 20 has a first coil 21 and a second coil 22. The first coil 21 corresponds to the main coil, and the second coil 22 corresponds to the auxiliary coil. Thus, in the proximity sensor 100, a dual-coil type with two coils can also be used as the detection coil 20.

[0056] The first coil 21 can also be wound around the shaft 31 of the ferrite core 30. The second coil 22 can also be wound around the outer peripheral wall 32 of the ferrite core 30. That is, the second coil 22 can also be arranged radially outside the first coil 21. The second coil 22 can also be arranged concentrically with respect to the first coil 21. In this specification, "arranged concentrically" means that it is not limited to the arrangement of circles lying on the same plane. Therefore, when the second coil 22 is arranged concentrically with respect to the first coil 21, it can also be arranged at a position closer to the detection body D (or the opposite side) than the first coil 21.

[0057] Furthermore, the length of the second coil 22 in the Z-axis direction can also be relatively short. Although details will be described later, it is possible that when the detectable distance of the proximity sensor 100 is extended, the detection accuracy of the proximity sensor 100 may decrease due to the signal components of the magnetic flux lines passing through both the detector D and the mounting member E in the magnetic flux lines based on the magnetic field generated by the coil 20. In the dual-coil type proximity sensor 100, the detection accuracy can be improved by correcting the detection signal, i.e., the detection signal in the first coil 21, which is dominated by the signal components of the magnetic flux lines passing through both the detector D and the mounting member E, based on the signal components of the magnetic flux lines passing through both the detector D and the mounting member E. For this purpose, it is necessary to ensure that the detection signal in the other coil, i.e., the second coil 22, includes the signal components of the magnetic flux lines passing through both the detector D and the mounting member E. If the structure has a shorter length in the Z-axis direction of the second coil 22, the magnetic flux lines passing through the detection body D and the mounting member E can easily bypass the -Z direction side of the second coil 22. In other words, the signal components based on the magnetic flux lines passing through the detection body D and the mounting member E are easily included in the detection signal of the second coil 22. Therefore, the detection accuracy of the proximity sensor 100 can be maintained while the detection distance of the proximity sensor 100 can be extended.

[0058] Alternatively, the second coil 22 can be positioned further from the detection body D than the first coil 21, i.e., at the front end. According to this structure, since the magnetic flux lines passing through both the detection body D and the mounting member E that do not affect the detection signal in the second coil 22 and do not affect the detection signal in the first coil 21 are reduced, the influence of the mounting member E can be suppressed and the detectable distance can be sufficiently extended.

[0059] The ferrite core 30 guides the magnetic field generated from the coil 20. The core holder 40 holds the ferrite core 30 and the substrate 50. In addition, the core holder 40 also functions as a support member for the second coil 22. The substrate 50 is electrically connected to the coil 20.

[0060] The electrical shield 80 is a bottomed cylindrical metal body that prevents external noise from intruding. The electrical shield 80 is disposed radially outside the second coil 22. The electrical shield 80 completely covers the coil 20, ferrite core 30, and core holder 40 in the sensor unit 25, and partially covers the substrate 50. To suppress noise in the received waveform, slits may also be formed on the bottom and sides of the electrical shield 80.

[0061] The magnetic shield 90 is a strongly magnetic material that induces magnetic flux lines received by both the first coil 21 and the second coil 22 in a manner that avoids the mounting member E described later. The magnetic shield 90 is disposed radially outward of the second coil 22, and more specifically, disposed outward of the electrical shield 80. The magnetic shield 90 may also be wound around the outer periphery of the resin cover 95, for example. The magnetic shield 90 completely covers the coil 20, the ferrite core 30, and the core holder 40 in the sensor unit 25, and partially covers the substrate 50 and the electrical shield 80.

[0062] The resin cap 95 is inserted into and fitted into the first end S1 of the main body portion 11 of the outer casing, protecting the components housed inside the outer casing 10. Alternatively, a cap made of a material other than resin may be used instead of the resin cap 95.

[0063] The cap nut 96 is an example of a cap-shaped metal component that can be attached and detached from the front end of the proximity sensor 100, i.e., the front end of the sensor head 101, by screwing it on. The cap nut 96 functions as a metal surface to protect the detection surface 17 from contamination and impacts from the detection object D, etc.

[0064] Furthermore, in the event of contamination or breakage of the cap nut 96, the user can easily replace only the cap nut 96. Therefore, the detection state of the proximity sensor 100 can be stabilized through extremely simple maintenance. However, the cap-shaped metal component does not necessarily have to be in the form of the cap nut 96, as long as it can protect the detection surface 17 from contamination and impact. That is, the cap-shaped metal component can also be coupled to the proximity sensor 100 by means other than screwing.

[0065] <Setup Example>

[0066] Next, an example of setting up the proximity sensor 100 will be described. For example... Figure 2 and Figure 4 As shown, the proximity sensor 100 is inserted into the through hole of the through mounting fitting E1 and secured by the nut E2 and cap nut 96 behind the mounting fitting E1. At this time, the external thread 12 formed on the outer circumferential surface of the proximity sensor 100 engages with the threaded holes (internal threads) of the nut E2 and cap nut 96. Furthermore, the mounting fitting E1 and the nut E2 can be understood as mounting members E for securing the proximity sensor 100.

[0067] In this way, the proximity sensor 100 is fixed by contact between the mounting member E and the external thread 12 provided on the outer periphery of the housing 10. That is, the external thread 12 can be understood as the mounting part that contacts the mounting member E when fixing the proximity sensor 100.

[0068] The specific installation sequence is as follows. First, remove the cap nut 96 from the proximity sensor 100. Second, install the proximity sensor 100 onto the mounting accessory E1. Third, clamp the mounting accessory E1 using the nut E2 installed from the base side of the proximity sensor 100 and the cap nut 96 reinstalled from the front side of the proximity sensor 100. Through this series of installation processes, the proximity sensor 100 is fixed to the mounting member E. Alternatively, washers can be placed between the nut E2 and the mounting accessory E1, and between the cap nut 96 and the mounting accessory E1, to fix the proximity sensor 100 to the mounting member E. Furthermore, while this application uses the cap nut 96 and nut E2 to clamp the mounting accessory E1, it is also possible to use a structure where a nut other than the cap nut 96 is placed between the cap nut 96 and the mounting accessory E1, and the proximity sensor 100 is fixed to the mounting member E by this nut and nut E2 clamping the mounting accessory E1.

[0069] Furthermore, the proximity sensor 100 can also be fastened to the detection surface 17 abutting against the cap nut 96. In this case, the coil 20 can also be positioned further forward than the mounting accessory E1 in the Z-axis direction. In other words, the coil 20 can also be positioned further forward than the opening surface at the base end of the cap nut 96 in the Z-axis direction. According to this structure, the influence of the mounting member E and the cap nut 96 can be suppressed.

[0070] In the above-described configuration, the proximity sensor 100 is surrounded by the mounting member E and the cap nut 96. In particular, pulse-type proximity sensors are mostly used in this configuration. However, the mounting member E and the cap nut 96 are generally metallic. Therefore, the proximity sensor 100, surrounded by the mounting member E and the cap nut 96, may detect not only the detection object D, but also the mounting member E and the cap nut 96, which should not be detected in the first place. Therefore, in order to sufficiently extend the detection range of the proximity sensor 100, it is desirable to suppress the influence of the mounting member E and the cap nut 96.

[0071] Furthermore, the user of the proximity sensor 100, such as the installer, can appropriately change the installation position of the mounting member E in contact with the external thread 12 by using cap nuts 96 of different sizes in the Z-axis direction. By appropriately changing the installation position of the mounting member E in contact with the external thread 12, the user can arbitrarily adjust the relative positional relationship between the detection surface 17 and the detection body D. In particular, during such installation operations, mode switching performed by the operation unit 15 and mode notification performed by the display unit 16 are effective. Based on these two functions, high efficiency can be achieved without compromising the freedom of installation operations. This will be described in detail later.

[0072] In particular, for user operability, the operation unit 15 and the display unit 16 are preferably located closer to the second end S2 than the aforementioned mounting position. According to this structure, even if the mounting position of the proximity sensor 100 relative to the mounting member E changes, the user can still operate the operation unit 15 and check the display unit 16 from the same side relative to the mounting member E, specifically from a position closer to the base end of the mounting member E. Therefore, the hassle of installation work can be significantly reduced.

[0073] <Sensor Unit>

[0074] Figure 5 This is a diagram showing the functional blocks of sensor unit 25. Sensor unit 25 includes a receiving circuit 60, a transmitting circuit 70, and a control circuit 76 as its main circuit structure.

[0075] The transmitting circuit 70 periodically flows a pulsed excitation current through the coil 20 based on a signal from the control circuit 76. The coil 20 generates a magnetic field by the periodic flow of the pulsed excitation current.

[0076] When the detection object D is within the detection range of the proximity sensor 100, eddy currents are induced in the detection object D by the magnetic field generated from the coil 20. These eddy currents in the detection object D generate a magnetic field. Here, the excitation current flowing through the coil 20 is pulsed, thus the magnetic field generated from the coil 20 weakens sharply. Therefore, the eddy currents in the detection object D also continuously weaken, and consequently, the magnetic field generated from the detection object D also weakens. To prevent the magnetic field generated from the detection object D from weakening, voltage and current are generated in the coil 20.

[0077] The receiving circuit 60 detects the voltage or current generated by the first coil 21 and the second coil 22, respectively. Because the first coil 21 and the second coil 22 have different configurations, the characteristics of the voltage or current generated are also different. By detecting voltages or currents with different characteristics, the operation of suppressing the influence of the mounting member E and the cap nut 96 becomes more efficient. Furthermore, the receiving circuit 60 may also be configured to detect the voltage or current generated by at least one of the first coil 21 and the second coil 22.

[0078] The control circuit 76 detects the detection object D based on changes in voltage or current detected by the receiving circuit 60. Preferably, the control circuit 76 detects the detection object D based on changes in voltage or current generated by the first coil 21 and the second coil 22, respectively. Therefore, the proximity sensor 100 can suppress the influence of the mounting member E and the cap nut 96, significantly extending the detectable distance. Furthermore, the control circuit 76 outputs the detection results to the outside via the aforementioned cable 19.

[0079] The first coil 21 generates a magnetic field by periodically flowing a pulsed excitation current from the transmitting circuit 70. In this embodiment, the coil 20 that generates the magnetic field by the excitation current is only the first coil 21.

[0080] Thus, the first coil 21 can also be a main coil that generates a magnetic field during the supply of excitation current and generates a first received waveform M, i.e., a first detection signal, based on the magnetic field during the cessation of the supply of excitation current. On the other hand, the second coil 22 can also be a secondary coil that does not generate a magnetic field itself but generates a second received waveform S, i.e., a second detection signal, based on the magnetic field during the cessation of the supply of excitation current.

[0081] When generating a magnetic field by circulating an excitation current through only one of the first coil 21 and the second coil 22, it is preferable to generate the magnetic field by circulating an excitation current through only the first coil 21. As described above, the first detection signal generated by the first coil 21 is different from the second detection signal generated by the second coil 22. In order to extend the detectable distance, it is preferable that the detection signal of at least one of them is easily affected by the detection body D. When the magnetic field generated from the coil 20 is directed towards the range where the detection body D may be located, i.e., the detection range, the detection signal generated by the coil 20 is easily affected by the detection body D. When the coil 20 through which the excitation current flows is a coil wound close to the shaft 31 of the ferrite core 30, the magnetic field generated is more likely to be directed towards the detection range. Therefore, it is preferable to generate a magnetic field by circulating an excitation current through the first coil 21.

[0082] However, the coil 20 that generates the magnetic field through the excitation current can be only the second coil 22, or it can be both the first coil 21 and the second coil 22. When generating the magnetic field by circulating the excitation current to both the first coil 21 and the second coil 22, for example, by directing the magnetic field of the first coil 21 towards the detector D and the magnetic field of the second coil 22 towards the mounting member E, the magnetic fields of the first coil 21 and the second coil 22 interfere with each other, thus achieving a detection result that mitigates the influence of the mounting member E. In this case, the transmitting circuit 70 can also have a first transmitting circuit that periodically circulates a pulsed excitation current to the first coil 21 and a second transmitting circuit that periodically circulates a pulsed excitation current to the second coil 22.

[0083] The transmitting circuit 70, receiving circuit 60, and control circuit 76 can also be disposed on the substrate 50, for example. With this structure, the circuits are less susceptible to noise interference, thus providing a stable circuit structure for the sensor unit 25. However, the transmitting circuit 70, receiving circuit 60, and control circuit 76 are not limited to being disposed on the substrate 50. For example, the transmitting circuit 70, receiving circuit 60, and control circuit 76 can be disposed on different components. Alternatively, one or two of the transmitting circuit 70, receiving circuit 60, and control circuit 76 can be disposed on the substrate 50, while the other circuits are disposed on other substrates or components. Furthermore, these other substrates or components can be disposed either inside or outside the housing 10.

[0084] The receiving circuit 60 includes a first receiving circuit 61 and a second receiving circuit 62. The first receiving circuit 61 detects the voltage or current generated in the first coil 21. The second receiving circuit 62 detects the voltage or current generated in the second coil 22. Hereinafter, the change in voltage or current over time detected by the receiving circuit 60 is sometimes referred to as the received waveform or the detection signal. Furthermore, the changes in voltage or current over time detected by the first receiving circuit 61 and the second receiving circuit 62 are sometimes referred to as the first received waveform and the second received waveform, or the first detection signal and the second detection signal, respectively.

[0085] The receiving circuit 60 has a first receiving circuit 61 and a second receiving circuit 62, so there is no need to switch the receiving circuit 60 when detecting the voltage or current generated in the first coil 21 and when detecting the voltage or current generated in the second coil 22. That is, by having the first receiving circuit 61 and the second receiving circuit 62, the receiving circuit 60 can simultaneously detect the voltage or current generated in the first coil 21 and the voltage or current generated in the second coil 22. Therefore, the detection object D can be detected using the voltage or current generated in the first coil 21 and the voltage or current generated in the second coil 22 at the same time. Therefore, the proximity sensor 100 can sufficiently extend the detectable distance by improving the detection accuracy.

[0086] <Operations Department>

[0087] Next, refer to Figure 6 as well as Figure 7 The peripheral structure of the operating section 15 is shown as an example. Figure 6 This is a diagram showing the YZ cross section of the proximity sensor 100, particularly the periphery of the operating section 15. Figure 6 Can be understood as Figure 2 The QQ cross-section diagram. Figure 7 This is a diagram showing the XY cross-section of the proximity sensor 100, particularly the periphery of the operating section 15. Figure 7 Can be understood as Figure 2 RR cross-sectional view.

[0088] The operating unit 15 includes a key member 151 with a button configuration that accepts user press operations. A through hole 111 is formed in the housing body 11, extending through its outer peripheral surface in the normal direction of the substrate 50, for example, the Y-axis direction. The key member 151 is inserted into the through hole 111. The key member 151 may also be configured such that its lower end contacts a switch 51 mounted on the substrate 50, and its upper end protrudes to the outside at a position closer to the innermost periphery of the housing body 11.

[0089] With this configuration, it is difficult for a user to press the operating part 15 with their own fingers. Therefore, it is difficult for undesirable misoperation by the user to occur. In particular, the housing body 11 is a component that the user is most likely to come into contact with during the installation of the proximity sensor 100. With the operating part 15 provided on such a component, this configuration can be said to be effective from the viewpoint of preventing misoperation of the operating part 15.

[0090] A key top 152 is formed at the upper end of the key member 151, protruding to the outside through a through hole 111. When the user presses the key, a tool with a pointed tip, such as a screwdriver or a ballpoint pen, comes into contact with the key top 152. Therefore, the key top 152 can also be formed in a shape that makes it difficult for the tool to slide, such as a mortar shape. According to this structure, pressing with a tool becomes easier.

[0091] A hook-shaped flash structure 153 is formed at the lower end of the key member 151. According to this structure, the key member 151 is not easily detached from the main body 11 of the outer casing before and after the filler 52 is filled.

[0092] The main body 11 of the outer casing is internally filled with a filler 52. The filler 52 may be a liquid or gel-like adhesive. The filler 52 may also be filled from an opening on the base end side of the main body 11, with all components except the base end 13 of the outer casing assembled to the main body 11. The filler 52 is primarily used for waterproofing purposes.

[0093] However, the proximity sensor 100 may collide with the detection object D. Therefore, the mechanical strength against collision with the detection object D can be improved for the front end side of the proximity sensor 100, such as the portion with external threads 12 formed on its outer periphery within the internal space of the housing body 11. Thus, the hardness of the filler 52 filling this portion can also be relatively high.

[0094] On the other hand, the base end of the proximity sensor 100 will not collide with the detection body D. Furthermore, a filler 52 is also filled around the key member 151 on the base end side of the proximity sensor 100. Therefore, for the portion of the base end side of the proximity sensor 100, such as the internal space of the housing body 11 where the external threads 12 are not formed on the outer periphery, it is important that it does not hinder the pressing operation of the key member 151. Therefore, the hardness of the filler 52 filling this portion can also be relatively low.

[0095] Thus, the filler 52 filling the interior of the main body 11 is not limited to one type. For example, the hardness, coefficient of thermal expansion, or color of the filler 52, or the filling method, can be arbitrarily adjusted for each filling part inside the main body 11.

[0096] Alternatively, a cushioning material 53 can be provided inside the main body 11 of the outer casing before the filler 52 is filled. The cushioning material 53 can also be a shrinkable sponge or the like. The cushioning material 53 is preferably disposed near the key member 151. According to this structure, even if the filler 52 thermally expands, its expansion can be offset by the shrinkage of the cushioning material 53. Therefore, the key member 151 is unlikely to protrude from the through hole 111 to the outside. In addition, the aforementioned burr structure 153 can also help prevent the key member 151 from protruding due to the thermal expansion of the filler 52.

[0097] Alternatively, a pair of substrate fixing grooves 112 extending along the Z-axis can be formed on the inner side of the main body 11 of the housing. The substrate fixing grooves 112 support the substrate 50 in a manner that clamps the substrate 50 from both sides in the X-axis direction. In this way, both the through hole 111 for inserting the key member 151 and the substrate fixing grooves 112 for supporting the substrate 50 can be integrally formed on the main body 11 of the housing.

[0098] According to this structure, the substrate 50 is supported in a state where it is pre-positioned perpendicular to the through hole 111. Therefore, the key member 151 inserted into the through hole 111 can reliably contact the switch 51 mounted on the substrate 50. Furthermore, from the viewpoint of preventing the substrate 50 from bending when the user performs a pressing operation, a support portion may be provided near the key member 151.

[0099] Thus, if an operation unit 15 is provided in the main body 11 of the housing, the installer of the proximity sensor 100 can, for example, adjust the position of the mounting member E and the proximity sensor 100 while simultaneously switching the operating mode of the proximity sensor 100. Therefore, the installation of the proximity sensor 100 can be made more efficient.

[0100] Furthermore, the display unit 16 may also be located at a position further away from the detection surface 17 than the key tip 152 in the normal direction of the detection surface 17, such as the Z-axis direction, i.e., the base end side. According to this structure, even when an operator close to the sensor 100 operates the operation unit 15 from the base end side, the operator's visual confirmation of the display unit 16 is not easily obstructed.

[0101] Thus, the operation unit 15 can also be operated during fine-tuning as the position of the mounting member E and the proximity sensor 100 is adjusted, and further as the position of the mounting member E and the sensor head 101 is adjusted. Additionally, the operation unit 15 can also be operated when the detection surface 17 is surrounded by the mounting member E. Alternatively, the operation unit 15 can also be operated when the cap nut 96 is positioned between the detection surface 17 and the detection body D. The cap nut 96 will be described later.

[0102] <An Examination of Inductive (Pulse) Types>

[0103] Figure 8 This is a graph showing the relationship between the oscillation frequency f and the skin depth δ of various metallic materials. Solid lines represent stainless steel (SUS304), small dashed lines represent carbon steel, large dashed lines represent aluminum (A5052), and single-dot dashed lines represent copper.

[0104] In the case where the proximity sensor 100 is a pulse-type inductive proximity sensor, the degree of attenuation of the magnetic flux line used for detection when it passes through the metal at the front end is determined by the skin depth δ. The skin depth δ is defined by the thickness of the metal at which the magnetic flux line attenuates by 1 / e (≈1 / 2.718) times, and is calculated by the following equation (1).

[0105]

Number 1

[0106]

[0107] In equation (1), f represents the oscillation frequency, μ r σ represents relative permeability, μ0 represents the permeability of vacuum, and σ represents electrical conductivity.

[0108] To suppress the influence of the metal of the cap nut 96 on the detection, the metal plate portion 96a covering the detection surface 17 in the cap nut 96 is preferably designed in a region below the skin depth δ. Furthermore, the effective frequency of pulse-type proximity sensors is generally in the low-frequency region below 100kHz to 200kHz. Compared to stainless steel, carbon steel, aluminum, and copper have shorter skin depths δ. Therefore, it is difficult to design them while maintaining mechanical strength. In view of this, the thickness of the front end is preferably stainless steel and designed to be 1.0mm or less.

[0109] Furthermore, by combining the inductive (pulse-type) sensor with the cap nut 96, it is possible to balance, for example, the thickness of the cap nut 96 and the extension of the detection distance. Therefore, the design freedom of the proximity sensor 100 can be increased.

[0110] <Magnetic shielding components>

[0111] Figure 9 This diagram illustrates the effect of the magnetic shielding 90. The upper and lower portions show XZ cross-sectional views of the proximity sensor 100, particularly around the coil 20. The upper portion corresponds to the state without the magnetic shielding 90. The lower portion corresponds to the state with the magnetic shielding 90 installed.

[0112] Furthermore, to explain the difference between the first detection signal, which is the detection signal of the first coil 21, and the second detection signal, which is the detection signal of the second coil 22, Figure 9 The magnetic field generated by the excitation current flowing through the first coil 21 is modeled using representative magnetic flux lines. Figure 9 The upper and lower parts of the magnetic flux lines received only by the first coil 21 are represented by thick lines (A) in the attached drawing; the magnetic flux lines received by both the first coil 21 and the second coil 22 are represented by dotted lines (B) in the attached drawing; and the magnetic flux lines received only by the second coil 22 are represented by dashed lines (C). Furthermore, in Figure 9 In order to illustrate the effect of the magnetic flux path on the detection signal, Figure 9 The “cap nut 96” in the description refers to the side part of the cap nut 96 that may affect the detection signal.

[0113] The detectable distance of the proximity sensor 100 can be extended by configuring the magnetic field generated by the first coil 21 to reach a greater distance in the +Z direction. However, since the magnetic field extends centered on the first coil 21, if its range extends in the +Z direction, the range also expands in the X-axis direction. That is, the path of the magnetic flux lines constituting the magnetic field expands not only in the +Z direction but also in the X-axis direction, so some magnetic flux lines may pass through a metal body different from the detection body D. If the proximity sensor 100 is surrounded by the mounting member E and the cap nut 96 as in this example, a large number of magnetic flux lines may pass through the mounting member E and the cap nut 96. The detection signal varies depending on the presence or absence of a metal body within the range of the magnetic field extension, making it difficult to distinguish whether the metal body within the range of the magnetic field extension, i.e., the metal body through which the magnetic flux lines pass, is the detection body D, the mounting member E, or the cap nut 96. Therefore, the detection accuracy of the proximity sensor 100 may be reduced because the magnetic flux lines pass through the mounting member E and the cap nut 96. Figure 9As shown in the upper part, the magnetic flux line (thick line: reference numeral A) received only by the first coil 21 passes only through the detector D, and the detector D in the mounting member E and the cap nut 96. That is, the magnetic flux line shown by reference numeral A is affected by the detector D. Assuming that the first detection signal is based only on the magnetic flux line shown by reference numeral A, the first detection signal changes based on the detector D. In other words, the signal component based on the magnetic flux line shown by reference numeral A changes depending on the presence or absence and position of the detector D. On the other hand, the magnetic flux line (dashed line: reference numeral C) received only by the second coil 22 passes only through the detector D, and the mounting member E and the cap nut 96 in the mounting member E and the cap nut 96. That is, the magnetic flux line shown by reference numeral C is affected by the mounting member E and the cap nut 96. Assuming that the second detection signal is based only on the magnetic flux line shown by reference numeral C, the second detection signal changes based on the mounting member E and the cap nut 96. Furthermore, the magnetic flux lines (dashed line: reference numeral B) received by both the first coil 21 and the second coil 22 pass through both the detection body D and the mounting member E and the cap nut 96. That is, the magnetic flux lines shown in reference numeral B are affected by the detection body D, the mounting member E, and the cap nut 96. Therefore, the first detection signal of the first coil 21, which receives the magnetic flux lines shown in reference numeral A and reference numeral B, varies based on both the detection body D and the mounting member E and the cap nut 96. In addition, the second detection signal of the second coil 22, which receives the magnetic flux lines shown in reference numeral C and reference numeral B, varies based on both the detection body D and the mounting member E and the cap nut 96. Moreover, in this figure, for convenience, both the magnetic flux lines represented by reference numeral B and reference numeral C pass only through the cap nut 96, but from the viewpoint of reducing the detection accuracy of the proximity sensor 100, the cap nut 96 and the mounting member E can be considered the same.

[0114] In this embodiment, the first detection signal has a larger proportion of signal components affected by the detected object D compared to the second detection signal. Therefore, the proximity sensor 100 uses the first detection signal to detect the detected object D. Therefore, by further reducing the signal components of the first detection signal affected by the mounting member E and the cap nut 96, the detection accuracy of the proximity sensor 100 can be improved. Since the signal components of the first detection signal affected by the mounting member E and the cap nut 96 originate from the magnetic flux lines shown by reference numeral B, the magnetic flux lines (dotted lines: reference numeral B) configured to be received by both the first coil 21 and the second coil 22 are less likely to pass through the mounting member E and the cap nut 96. Therefore, the signal components of the first detection signal affected by the mounting member E and the cap nut 96 are relatively reduced, thus improving the detection accuracy of the proximity sensor 100.

[0115] Compared to the upper part without magnetic shielding, the lower part with magnetic shielding ensures that the magnetic flux lines (dotted lines: reference numeral B) received by both the first coil 21 and the second coil 22 avoid the path of the mounting member E and the cap nut 96. Therefore, compared to the upper part, in the lower part, the number of magnetic flux lines (dotted lines: reference numeral B) received by both the first coil 21 and the second coil 22 that pass through the mounting member E and the cap nut 96 is reduced. To achieve the state shown in the lower part, the magnetic shielding member 90 and the ferrite core 30 are appropriately provided.

[0116] Furthermore, as shown below, by appropriately configuring the magnetic shield 90, the magnetic flux lines (dotted line: reference numeral B) received by both the first coil 21 and the second coil 22 further avoid paths such as the mounting member E and the cap nut 96. This is because the magnetic shield 90 guides the magnetic flux lines with a relative permeability of a certain degree or higher.

[0117] Furthermore, by forming the ferrite core 30 into a suitable shape, it becomes part of the magnetic flux lines received by both the first coil 21 and the second coil 22 (dotted line: reference numeral B), further avoiding paths such as the mounting member E and the cap nut 96. This is because the shape of the ferrite core 30 causes the magnetic flux lines to further extend towards the front end side (+Z direction side).

[0118] Furthermore, as shown below, the magnetic shield 90 is disposed radially outside the second coil 22. With this configuration, the magnetic flux lines (dotted lines: reference numeral B) received by both the first coil 21 and the second coil 22 are guided along the magnetic shield 90, thus creating a path that further avoids the mounting member E and the cap nut 96. Therefore, the proximity sensor 100 can sufficiently extend the detectable distance by suppressing the influence of the mounting member E and the cap nut 96 on the first detection signal of the first coil 21.

[0119] Furthermore, the magnetic shielding component 90 is required to be positioned as close as possible to the mounting component E and the cap nut 96, possess high relative permeability, and be low-cost. Additionally, the magnetic shielding component 90 itself cannot be detected as a metallic object. Therefore, the magnetic shielding component 90 is also required to have high resistance, small thickness, and not form loops for circumferentially flowing eddy currents.

[0120] <Detection Principle>

[0121] Figure 10 This diagram illustrates the detection principle of the inductive (pulse) type. The upper part shows the change of the excitation current flowing through coil 20 over time. The lower part shows the received waveform obtained from coil 20, i.e., the change of the voltage across coil 20 over time. In this diagram, for convenience, coil 20 is described as a single (single-coil type) coil.

[0122] During the supply period T1 of the excitation current, an excitation current is supplied to coil 20. As a result, coil 20 generates a magnetic field. In addition, the excitation current can also be controlled as a constant current.

[0123] Subsequently, during the periods T2 and T3 when the excitation current supply ceases, the supply of excitation current is stopped. Therefore, the magnetic field generated from coil 20 weakens. Consequently, voltage and current are generated in coil 20 to counteract the weakening of the magnetic field.

[0124] At this time, the received waveform obtained by coil 20 varies depending on whether a detection object D is present within the detection range of proximity sensor 100. As described in the figure, when there is no detection object D, as shown by the solid line, the voltage across coil 20 decreases sharply within a relatively short time. On the other hand, when there is a detection object D, as shown by the small dashed line, the voltage across coil 20 decreases slowly over a relatively long period. The presence or absence of a detection object D can be determined based on this difference in the received waveform, for example, the difference in the integral value obtained by integrating the change in the received waveform.

[0125] Furthermore, the integration processing of the received waveform is preferably performed after the reduction of the received waveform has stabilized to a certain extent. In other words, preferably, if there is no detector D, the integration processing of the received waveform begins when it is estimated that the voltage across coil 20 has completely dropped to its minimum value. As described in this figure, it is preferable to perform the integration processing of the received waveform during the standby period until the excitation current supply stops (T2, non-integration period), and during the excitation current supply stops (T3, integration period).

[0126] Based on the above detection principle, the following describes the receiving waveform of the dual-coil type using the first coil 21 and the second coil 22.

[0127] Figure 11 This is a diagram showing the received waveforms of a dual-coil type. In this diagram, the first received waveform is indicated by reference numeral M, and the second received waveform is indicated by reference numeral S.

[0128] (a) is a graph showing the received waveform when component E and cap nut 96 are not installed and detector D is not within the detection range. (b) is a graph showing the received waveform when component E and cap nut 96 are not installed and detector D is within the detection range. (c) is a graph showing the received waveform when component E and cap nut 96 are installed and detector D is not within the detection range. (d) is a graph showing the received waveform when component E and cap nut 96 are installed and detector D is within the detection range. In each graph, the horizontal axis represents time, and the vertical axis represents the signal strength of the received waveform.

[0129] Columns (a) and (b) are graphs showing the results without the installation of component E and cap nut 96. As shown in column (a), when the detection body D is not within the detection range, only the metal component forming the proximity sensor 100 is detected, resulting in a first received waveform M and a second received waveform S reflecting the detection result.

[0130] On the other hand, as shown in column (b), when the detector D is within the detection range, since the detector D is detected, the changes in both the first received waveform M and the second received waveform S are larger compared to column (a). In particular, the first received waveform M obtained by the first coil 21 is more susceptible to the influence of the detector D than the second received waveform S obtained by the second coil 22; therefore, the change in the first received waveform M in column (b) is larger than the change in the second received waveform S in column (b).

[0131] Columns (c) and (d) are graphs showing the results with mounting member E and cap nut 96 present. As shown in column (c), even when the detector D is not within the detection range, the changes in both the first received waveform M and the second received waveform S are larger than in column (a) because mounting member E and cap nut 96 are detected. In particular, the second received waveform S obtained by the second coil 22 is more susceptible to the influence of mounting member E and cap nut 96 than the first received waveform M obtained by the first coil 21; therefore, the change in the second received waveform S in column (c) is larger than the change in the first received waveform M in column (c).

[0132] On the other hand, as shown in column (d), when the mounting member E and the cap nut 96 are present and the detector D is within the detection range, the detector D is detected in addition to the mounting member E and the cap nut 96. Therefore, compared to column (a), the changes in both the first received waveform M and the second received waveform S are larger. In particular, when the detector D is within the detection range, the received waveform obtained by the coil 20 is more susceptible to the influence of the detector D. Therefore, the change in the first received waveform M, which is more susceptible to the influence of the detector D than the second received waveform S in column (d), is larger than the change in the second received waveform S in column (d). That is, as can be seen from the comparison between column (c) and column (d), the difference in the change in the first received waveform M caused by the presence or absence of the detector D is greater than the difference in the change in the second received waveform S caused by the presence or absence of the detector D.

[0133] As shown in columns (a) and (b), and as shown in columns (c) and (d), the first received waveform M is more susceptible to the influence of the detector D than the second received waveform S. However, if only the first received waveform M is considered, it can be seen that the difference in the amount of change between columns (a) and (c) is also significant, and the first received waveform M is also affected by the mounting member E and the cap nut 96. When the amount of change of the first received waveform M in column (b) is as large as the amount of change of the first received waveform M in column (c), it is difficult to set a threshold to distinguish the first detection signal in these two states, and false detection is possible. In particular, the longer the distance between the detector D and the coil 20, the smaller the difference between the amount of change caused by the presence or absence of the detector D and the amount of change caused by the presence or absence of the mounting member E and the cap nut 96. Therefore, when the mounting member E and the cap nut 96 are present, it is difficult to correctly detect the presence or absence of the detector D, especially the state where the detector D is absent, solely based on the first received waveform M.

[0134] On the other hand, as shown in columns (a) to (d), when comparing the first received waveform M and the second received waveform S, the first received waveform M is more susceptible to the influence of the detector D than the second received waveform S, while the second received waveform S is more susceptible to the influence of the mounting member E and the cap nut 96 than the first received waveform M. That is, the second received waveform S exhibits a different tendency in terms of the amount of change compared to the first received waveform M. More specifically, compared to the first received waveform M, the difference in the amount of waveform change caused by the presence or absence of the detector D within the detection range in the second received waveform S (e.g., the difference between columns (a) and (b), and between columns (c) and (d)) is smaller, while the difference in the amount of waveform change caused by the presence or absence of the mounting member E and the cap nut 96 in the second received waveform S (e.g., the difference between columns (a) and (c), and between columns (b) and (d)) is larger than the difference between columns (a) and (c), and between columns (b) and (d). Therefore, by performing calculations based on the first received waveform M and the second received waveform S, the presence or absence of the detection body D can be detected efficiently by suppressing the influence of the mounting component E and the cap nut 96.

[0135] For example, the control circuit 76 can also calculate the difference between the first received waveform M and the second received waveform S as a detection signal W (=MS). Based on this calculation, a detection signal W with different values ​​depending on the presence or absence of the detection body D is generated. Therefore, the presence or absence of the detection body D can be accurately detected based on the detection signal W.

[0136] In this way, by employing a dual-coil type, the proximity sensor 100 can detect objects that exclude the influence of surrounding metal, including the mounting member E and the cap nut 96. Therefore, the detection range of the proximity sensor 100 is essentially increased. For example, in the dual-coil type proximity sensor 100, its detection range can be set to be longer than 10 mm.

[0137] Furthermore, the longer the detection distance of the proximity sensor 100, the greater the need for fine-tuning the mounting position of the proximity sensor 100. Therefore, mode switching performed by the operation unit 15 and mode notification performed by the display unit 16 are more useful. This will be explained in detail later.

[0138] Furthermore, based on the combination of the dual-coil type and the cap nut 96, the first received waveform M and the second received waveform S can be arbitrarily subtracted. Therefore, the design freedom of the proximity sensor 100 can be increased.

[0139] <Demonstration (Zeroing)>

[0140] like Figure 11 As shown in columns (a) and (c), even when the detected object D is not within the detection range, the first received waveform M and the second received waveform S are not essentially zero. Therefore, the detected object signal W (=MS) calculated by the difference between the first received waveform M and the second received waveform S may also have some offset values. This is because the proximity sensor 100 may erroneously detect a metal object that is not actually being detected, such as a metal component forming the proximity sensor 100, or a mounting component E and a cap nut 96 that are in contact with the proximity sensor 100.

[0141] Therefore, it is preferable that the detection unit 26, which generates the detection signal W, and especially the control circuit 76, which is the main processor of the detection signal W, receive a teaching instruction from the installation environment where the proximity sensor 100 is installed. Upon receiving this teaching instruction, the detection unit 26 can perform a calibration process, known as zeroing, in this installation environment to bring the detection signal W obtained when the detection object D is not within the detection range close to zero. Therefore, the influence of metal objects that are not the target of detection can be reduced.

[0142] Furthermore, the teaching of the proximity sensor 100 can also be triggered by a user's pressing operation received by the aforementioned operation unit 15. Thus, it is preferable that the user's teaching operation is received by the operation unit 15 located on the main body 11 of the housing. According to this structure, the user can teach the installation environment without much effort simply by pressing the operation unit 15 while installing the proximity sensor 100. Therefore, the installation operation can be made more efficient. Moreover, the above teaching is effective even when the type, shape, or material of the cap nut 96 installed on the proximity sensor 100 differs.

[0143] Cap nut

[0144] Figure 12 This is a diagram showing the XZ section of the cap nut 96. The XZ section of the cap nut 96 is depicted in the left column. This left column can be understood as a representation of the aforementioned... Figure 4 The image shows an enlarged view of the front end of the proximity sensor 100. Additionally, in the right column, a typical nut with a dome-shaped portion is depicted for comparison. Furthermore, the dome-shaped nut illustrated in this figure is achieved by machining the outer shape into a dome shape, but it can also be achieved by machining the inner side of the dome-shaped portion along the outer shape.

[0145] Furthermore, for ease of illustration, the housing 10 with the cap nut 96 mounted and the mounting member E are not depicted. Regarding the case where the cap nut 96 is mounted on the proximity sensor 100, the aforementioned description may also be appropriately referenced. Figures 2-4 .

[0146] The cap nut 96 may also be made of stainless steel, for example. The cap nut 96 includes a metal plate portion 96a and a non-through hole 96b. The front end side of the metal plate portion 96a in the Z-axis direction closes the non-through hole 96b, covering the detection surface 17. That is, the inner surface of the metal plate portion 96a faces the detection surface 17 (not shown). On the other hand, the outer surface of the metal plate portion 96a faces the detection body D (not shown).

[0147] Unlike ordinary nuts, the cap-shaped nut 96 has a flat outer surface of the metal plate portion 96a. Therefore, the distance between the detection surface 17 in the Z-axis direction and the +Z side end of the nut mounted on the housing 10 can be shortened. When the nut is mounted on the housing 10, the detectable distance of the proximity sensor 100 is the length obtained by subtracting the distance between the detection surface 17 and the +Z side end of the nut mounted on the housing 10 from the detectable distance based on the detection surface 17. By shortening the distance between the detection surface 17 and the +Z side end of the nut mounted on the housing 10, the shortening of the detectable distance of the proximity sensor 100 can be prevented.

[0148] In particular, the metal plate portion 96 includes a thin plate portion 96a1 and a thick plate portion 96a2. The thin plate portion 96a1 may also be provided in the central portion of the metal plate portion 96. The thickness d1 of the thin plate portion 96a1 may be, for example, about 0.35 mm to 1.0 mm. The thick plate portion 96a2 may also be provided in the outer edge portion of the thin plate portion 96a1, and more specifically, in the portion abutting against the outer casing 10 (not shown). The thickness d3 of the thick plate portion 96a2 may be, for example, about d1+0.1 mm to d1+0.6 mm.

[0149] According to this structure, the metal plate portion 96 between the detection surface 17 and the detection body D can be made as thin as possible to extend the detection distance, and the thickness can be maintained at the part abutting the housing 10 to ensure the durability of the cap nut 96. In particular, in a proximity sensor 100 with a detection distance of about 10 mm, even a small difference in thickness can become very important.

[0150] The non-through hole 96b has an internal thread 96b1 and a large-diameter region 96b2. This non-through hole 96b can be formed by a so-called boring process. The internal thread 96b1 engages with an external thread 12 (not shown). The internal thread 96b1 can also be formed in a portion of the non-through hole 96b, specifically on the base end side in the Z-axis direction.

[0151] The major diameter region 96b2 can also be formed as part of the non-through hole 96b, specifically, on the front end side in the Z-axis direction. The inner surface of the major diameter region 96b2 can also be a smooth surface without thread cutting. The inner diameter of the major diameter region 96b2 can also be designed to be larger than the inner diameter of the thread groove formed in the internal thread 96b1.

[0152] That is, the cap nut 96 has a recess 96b3 on its inner circumferential surface of the non-through hole 96b. Furthermore, when the cap nut 96 is installed onto the housing 10, a gap is created in the circumferential direction at the front end of the housing 10, which includes the detection surface 17. In other words, the distance between the cap nut 96 and the second coil 22 increases. Therefore, the change in the second received waveform obtained by the second coil 22 decreases.

[0153] Thus, in the proximity sensor 100 with the cap-shaped nut 96 installed, the metal plate portion 96a is located between the detection surface 17 and the detection body D. Therefore, the aforementioned teaching can be particularly useful.

[0154] <Through Metal>

[0155] Figure 13This diagram illustrates the general outline of the teaching process using a metal plate. The metal plate can be understood as the state where the metal plate F is positioned between the detection surface 17 and the detection body D. For example, the metal plate 96a of a cap nut 96 can be cited as the metal plate F. Furthermore, the upper part of this diagram shows the detection results before and after teaching without the detection body D. Conversely, the lower part of this diagram shows the detection results before and after teaching with the detection body D present. Additionally, reference numeral M indicates the integral value of the first received waveform, and reference numeral S indicates the integral value of the second received waveform. Furthermore, reference numerals W and ΔW indicate the detection body signal before and after teaching.

[0156] As mentioned above Figure 8 As explained, if the metal plate portion F is thin, magnetic flux can pass through, thus allowing the detection object D to be detected using a proximity sensor 100 with a cap-shaped nut 96 mounted on it. However, the first received waveform M and the detection object signal W are affected by the metal plate portion F, i.e., by the cap-shaped nut 96. As described in this figure, the detection object signal W before teaching becomes a large value, as if the detection object D were present, even in the absence of the detection object D. Furthermore, in the state before teaching, it is less likely that a difference will arise between the change in the integral value of the first received waveform M caused by the presence or absence of the detection object D and the change in the integral value of the second received waveform S.

[0157] Of course, when there is a detector D, compared to the case without detector D, the integral values ​​of the first received waveform M and the second received waveform S increase, and there is a difference in the amount of increase. Therefore, this difference can be used to set a threshold. However, the threshold of the detector signal W is mostly set so that the detection result becomes ON when there is a detector D but no metal plate F. At this time, the state with detector D but no metal plate F and the state with detector D and Figure 13 In the upper part of the waveform, the integrated values ​​of the first received waveform M and the second received waveform S, as well as the detector signal W, become similar values. Therefore, it is difficult to set a value that can distinguish between them. Figure 13 The upper and lower states should be compared with the threshold value of the detection signal W.

[0158] Therefore, teaching corresponding to the type of cap nut 96, such as the thickness of the metal plate portion 96a, is useful. Based on this teaching, the detection signal W obtained when the detection body D is not within the detection range is adjusted to zero. In this figure, the detection signal ΔW after teaching is shown relative to the detection signal W before teaching. As shown in this figure, the detection signal ΔW after teaching becomes zero when there is no detection body D, and becomes a signal value (≠0) corresponding to the relative distance between the proximity sensor 100 and the detection body D when there is a detection body D.

[0159] Figure 14This is a diagram showing the detector signal before and after teaching through the metal. Furthermore, in this diagram, the integral value of the first received waveform is indicated by reference numeral M, and the integral value of the second received waveform is indicated by reference numeral S. Additionally, the detector signal before and after teaching is indicated by reference numerals W and ΔW.

[0160] Column (a)' represents the detection result when component E is not installed and the detection body D is not within the detection range. In this case, the taught detection body signal ΔW becomes zero. On the other hand, column (b)' represents the detection result when component E is not installed and the detection body D is within the detection range. In this case, the taught detection body signal ΔW becomes a positive signal value (>0) corresponding to the relative distance between the proximity sensor 100 and the detection body D.

[0161] Additionally, column (c)' indicates the detection result when the mounting component E is present and the detection object D is not within the detection range. In this case, since the teaching instruction is received in the state indicated in column (c), the taught detection object signal ΔW becomes zero. On the other hand, column (d)' indicates the detection result when the mounting component E is present and the detection object D is within the detection range. In this case, the taught detection object signal ΔW becomes a positive signal value (>0) corresponding to the relative distance between the proximity sensor 100 and the detection object D.

[0162] Given the above actions, the detected object signal ΔW after teaching can also be compared with a positive threshold ΔWth (>0) after performing the prescribed amplification process. For example, when the detected object signal ΔW is higher than the threshold ΔWth, it can be determined that a detected object D is present. On the other hand, when the detected object signal ΔW is lower than the threshold ΔWth, it can be determined that a detected object D is not present. Based on this comparison process, the influence of the metal plate portion F, which is not the object to be detected, can be reduced, and the presence or absence of the detected object D can be detected accurately.

[0163] That is, the control circuit 76 that performs the above comparison processing can be understood as changing the detection method of the detection body D based on the positional relationship between the detection surface 17 and the metal plate part F when the operation unit 15 receives the teaching operation. By changing the detection method in this way, the control circuit 76 that executes the changed detection method can detect the detection body D without detecting the metal plate part F which is in the above positional relationship.

[0164] In particular, when considering the proximity sensor 100 with the cap nut 96 installed, the control circuit 76 can also change the detection method based on the first received waveform M and the second received waveform S, depending on the type of cap nut 96 when the operation unit 15 receives the teaching operation, such as the thickness of the metal plate portion 96a. By changing the detection method in this way, the control circuit 76 executing the changed detection method can detect the detection body D without detecting the cap nut 96.

[0165] <Display Section>

[0166] Figure 15 This is a diagram showing the display mode in the display unit 16 corresponding to the relative distance d between the proximity sensor 100 and the detection body D.

[0167] First, referring to the right-pointing arrow at the bottom, let's explain the case where the detector D continuously moves away from the proximity sensor 100, i.e., the relative distance d continuously increases. In this case, when d0 ≤ d < d1, the display unit 16 is in the ON state, for example, an orange illuminated state. Alternatively, d0 = 0. When d1 ≤ d < d3, the display unit 16 is in a boundary ON state, indicating an ON state near the boundary between ON and OFF, for example, an orange flashing state. When d3 ≤ d, the display unit 16 is in the OFF state, for example, a green illuminated state.

[0168] Next, the case where the detection object D continuously approaches the proximity sensor 100, i.e., the relative distance d continuously decreases, will be explained. In this case, when d2 ≤ d, the display unit 16 becomes OFF. Alternatively, d2 < d3. That is, a lag can be imposed on the relative distance d for the transition between the boundary ON and OFF states. When d1 ≤ d < d2, the display unit 16 becomes boundary ON. When d0 (= 0) ≤ d < d1, the display unit 16 becomes ON.

[0169] Furthermore, as shown in this figure, the detectable distance of the proximity sensor 100 can also be defined as the relative distance d from the display unit 16 switching from the OFF state to the boundary ON state, i.e., the threshold distance d2. However, the definition of the detectable distance is not limited to this. For example, the relative distance d from the display unit 16 switching from the ON state to the boundary ON state, i.e., the threshold distance d1, can also be defined as the detectable distance. Alternatively, the relative distance d from the display unit 16 switching from the boundary ON state to the OFF state, i.e., the threshold distance d3, can also be defined as the detectable distance. Alternatively, the detectable distance of the proximity sensor 100 can also be understood as the relative distance d from the output (ON / OFF) switching of the proximity sensor 100. In addition, the threshold distances d1, d2, and d3 can each be understood as the threshold ΔWth compared with the detected body signal ΔW after teaching.

[0170] Figure 16 This diagram illustrates the state transitions of the proximity sensor 100. The proximity sensor 100 is activated by power-on. When the proximity sensor 100 reaches a state where it can operate normally, the operating mode of the detection unit 26 is set to either a first mode (MODE1) or a second mode (MODE2). The first mode could be, for example, a long-range mode where the proximity sensor 100 has a relatively long detection distance. The second mode could be, for example, a short-range mode where the proximity sensor 100 has a relatively short detection distance, or a metal-passing mode.

[0171] When the proximity sensor 100 is operating normally, the display unit 16 illuminates with a light color corresponding to the ON / OFF output of the proximity sensor 100. Therefore, the user can visually recognize that the proximity sensor 100 has been correctly activated by power-on.

[0172] The operation unit 15 handles mode switching operations. For example, the first mode and the second mode can be switched alternately whenever the operation unit 15 is pressed and held for 3 seconds. In this case, multiple thresholds ΔWth can be prepared for each operation mode and switched according to the mode switching operation. For example, in the first mode, the threshold ΔWth can be lowered to extend the detectable distance. On the other hand, in the second mode, the threshold ΔWth can be increased to shorten the detectable distance.

[0173] Furthermore, during mode switching, a mode check is performed, and the check result is displayed on the display unit 16. For example, when the operation unit 15 is pressed and held for 3 seconds in the first mode, the system switches to the second mode, and a mode check is immediately performed. At this time, the display unit 16 flashes twice to indicate that it is in the second mode. On the other hand, when the operation unit 15 is pressed and held for 3 seconds in the second mode, the system switches to the first mode, and a mode check is immediately performed. At this time, the display unit 16 flashes once to indicate that it is in the first mode.

[0174] Furthermore, during mode notification, the color of the light emitted by the display unit 16 can also depend on the output (ON / OFF) of the proximity sensor 100. That is, a structure can be adopted in which the operating mode is indicated by the number of flashes and the output (ON / OFF) of the proximity sensor 100 is indicated by the color of the light emitted. According to this structure, the user can switch the operating mode without changing the setting position of the proximity sensor 100 and confirm whether the output (ON / OFF) of the proximity sensor 100 has changed. However, this is not the case for automatic teaching performed simultaneously with mode switching, as described later.

[0175] Furthermore, this mode notification can be performed only once. Afterwards, the display unit 16 can also return to the normal display state for each operation mode. In addition, the above-mentioned series of mode checks and mode notifications can also be performed when the operation unit 15 is briefly pressed.

[0176] Furthermore, the display unit 16 can be turned off when the operation unit 15 is pressed to a degree that allows for operation. Therefore, if the operation unit 15 is pressed briefly, the display unit 16 is turned off; conversely, the display unit 16 remains off during a long press of the operation unit 15. According to this structure, the user can visually recognize that the operation unit 15 has been pressed. Thus, the display unit 16 can also function as a notification unit that informs the user when the key member 151 of the operation unit 15 is pressed. In particular, this structure becomes useful when the key member 151 of the operation unit 15 is designed to be difficult to press in order to prevent accidental operation. Furthermore, this notification unit can also be provided independently of the display unit 16.

[0177] Furthermore, when the operation unit 15 receives a mode switching operation, the aforementioned teaching can also be executed automatically at the same time. That is, the detection unit 26 can also receive teaching of the setting environment each time the operation mode is switched. In other words, the teaching operation can also be triggered by a mode selection operation that selects any one of multiple modes with different detectable distances of the detector body D as the operation mode of the detection unit 26.

[0178] The mode switching in the operation unit 15 is mostly performed during the installation of the proximity sensor 100 to verify whether the current operating mode is appropriate in a certain setting environment. According to this structure, mode switching and teaching required to obtain optimal detection results based on the setting environment of the proximity sensor 100 can be performed with a single operation. Therefore, the installation of the proximity sensor 100 can be made more efficient. Furthermore, with this structure, it is preferable to perform mode switching when there is no detection object D within the detection range.

[0179] Furthermore, if the proximity sensor 100 detects an anomaly, the display unit 16 is controlled to turn on and off in a display mode corresponding to the erroneous content. Additionally, if the anomaly is eliminated, the display unit 16 can be restored to its normal display state in each operating mode.

[0180] Figure 17 This diagram shows an overview of the display modes in the display unit 16. As shown in this diagram, the display unit 16 functions as a notification unit that informs the user of the detection status of the detector D, the selection status of the operation mode, and the occurrence status of an error in their respective display modes.

[0181] In the absence of a detection object D, the display unit 16 can be kept constantly lit in green, regardless of the operating mode. In this case, the output of the proximity sensor 100 can also be OFF. When a detection object D is present, the display unit 16 can be kept constantly lit in orange, regardless of the operating mode. In this case, the output of the proximity sensor 100 can also be ON. In the boundary ON state, the display unit 16 can also flash orange, regardless of the operating mode. In this case, the output of the proximity sensor 100 can also be ON.

[0182] In the event of an error, the display unit 16 can be controlled to turn on and off in a display mode corresponding to the content of the error, regardless of the operating mode. This display mode will be described later.

[0183] When a mode check is performed, the display unit 16 can also be controlled to turn on and off in a display mode corresponding to the output and operation mode of the proximity sensor 100. For example, when the output is OFF in the first mode, the display unit 16 may flash green once. When the output is ON in the first mode, the display unit 16 may flash orange once. When the output is OFF in the second mode, the display unit 16 may flash green twice. When the output is ON in the second mode, the display unit 16 may flash orange twice.

[0184] Figure 18 This is a timing diagram showing the display modes in display unit 16. Blank areas represent the orange illumination period. Shaded areas represent the green illumination period. Blackened areas represent the off period. The minimum illumination period and minimum off period of display unit 16 can be, for example, 0.25 seconds.

[0185] First, the normal display at the top will be explained. In the ON state, display unit 16 is always illuminated in orange. In the boundary ON state, display unit 16 flashes orange. For example, a minimum off period of two cycles may be included within the orange illumination period. In the OFF state, display unit 16 is always illuminated in green.

[0186] Next, the display mode in the middle will be explained. In the first mode, the display unit 16 flashes once. For example, a minimum illumination period of one flash may be included during the off period. In the second mode, the display unit 16 flashes twice. For example, a minimum illumination period of two flashes may be included during the off period. Furthermore, the color of the light emitted by the display unit 16 may also depend on the output (ON / OFF) of the proximity sensor 100. In this figure, the display unit 16 flashes green, which corresponds to the OFF state.

[0187] Finally, the error displays at the bottom will be explained. In the event of a system error, display unit 16 lights up and turns off in the order of off → green → orange → off… In the event of a ROM [Read Only Memory] error, display unit 16 lights up and turns off in the order of off → orange → green → off… In the event of an overcurrent error, display unit 16 lights up and turns off in the order of off → green → off → orange → off…

[0188] However, the above display modes are merely examples, and of course, any display mode can be used.

[0189] <Mode Switching and Mode Notification>

[0190] Figure 19 This diagram illustrates the switching of operating modes corresponding to the installation position of the proximity sensor 100. Furthermore, the upper part of column (A) depicts the case where the proximity sensor 100 is installed in an ideal installation position relative to the detector D. The upper part of column (B) depicts the case where the proximity sensor 100 is installed away from the detector D. The upper part of column (C) depicts the case where the proximity sensor 100 is installed close to the detector D. Additionally, the lower part of each column depicts the taught detector signal ΔW and the threshold ΔWth, respectively.

[0191] In the installation of proximity sensor 100, it is very difficult to install it to the ideal setting position in column (A) in one go. In practice, the sensor is often installed in column (B) or (C). Therefore, in previous installations, it was often a tedious process requiring repeated fine-tuning of the setting position to approximate the ideal setting position in column (A).

[0192] On the other hand, as described above, if it is a proximity sensor 100, then mode switching in the operation unit 15 and mode notification in the display unit 16 are possible. If these functions are effectively utilized, the user does not need to fine-tune the setting position of the proximity sensor 100, but only needs to switch to the optimal operating mode, or more specifically, switch the threshold ΔWth, based on the setting position of the proximity sensor 100. That is, there is no need to fine-tune the setting position of the proximity sensor 100.

[0193] First, consider the case where the proximity sensor 100 is installed in column (A). In this case, it is preferable to set a first threshold ΔWth1 as the threshold ΔWth. According to this setting, when the detector D is at the ON distance, the detector signal ΔW exceeds the threshold ΔWth, and when the detector D is at the OFF distance, the detector signal ΔW is below the threshold Wth. As a result, the presence or absence of the detector D can be accurately detected.

[0194] Next, consider the case where the proximity sensor 100 is installed at the position in column (B). In this case, it is preferable to set a second threshold ΔWth2, which is lower than the first threshold ΔWth1, as the threshold ΔWth. That is, it is preferable to extend the detectable distance of the proximity sensor 100. If the first threshold ΔWth1 is directly set as the threshold ΔWth, even if the detector D is at the ON distance, the detector signal ΔW will be lower than the threshold ΔWth1, and the output may be mistakenly OFF. On the other hand, according to this setting, when the detector D is at the ON distance, the detector signal ΔW exceeds the threshold ΔWth, and when the detector D is at the OFF distance, the detector signal ΔW is lower than the threshold ΔWth. As a result, the presence or absence of the detector D can be detected correctly.

[0195] Finally, consider the case where the proximity sensor 100 is installed in column (C). In this case, it is preferable to set a third threshold ΔWth3, which is higher than the first threshold ΔWth1, as the threshold ΔWth. That is, it is preferable to shorten the detectable distance of the proximity sensor 100. If the first threshold ΔWth1 is directly set as the threshold ΔWth, even if the detector D is at the OFF distance, the detector signal ΔW will exceed the threshold ΔWth1, and the output may mistakenly become ON. On the other hand, according to this setting, when the detector D is at the ON distance, the detector signal ΔW exceeds the threshold ΔWth, and when the detector D is at the OFF distance, the detector signal ΔW is lower than the threshold ΔWth. As a result, the presence or absence of the detector D can be detected correctly.

[0196] In this way, by switching modes in the operation unit 15, there is no need for complicated fine-tuning of the setting position. Therefore, the installation of the proximity sensor 100 can be made more efficient.

[0197] Furthermore, based on the mode notification on the display unit 16, it is easy to determine whether the selected operation mode is appropriate. For example, before fine-tuning the setting position, the user can sequentially switch between multiple pre-prepared operation modes and confirm each time whether the detector D is correctly detected in the current operation mode. At this time, based on the mode notification on the display unit 16, the user can easily determine whether the verification has been completed in all operation modes. Therefore, the installation operation of the proximity sensor 100 can be made more efficient.

[0198] Furthermore, according to the mode notification in the display unit 16, even when the setting position of the proximity sensor 100 needs to be adjusted, the user can know whether it is better to move the proximity sensor 100 away from the detection object D, or conversely, to move the proximity sensor 100 closer to the detection object D. For example, if the detection object D is not detected correctly even in the operating mode with the shortest detection distance of the proximity sensor 100, it is necessary to move the proximity sensor 100 away from the detection object D. Conversely, if the detection object D is not detected correctly even in the operating mode with the longest detection distance of the proximity sensor 100, it is necessary to move the proximity sensor 100 closer to the detection object D. If such insight is obtained, the installation operation of the proximity sensor 100 can be made more efficient.

[0199] Furthermore, the aforementioned cap nut 96 can also be used when the probability of collision between the detection body D and the detection surface 17 is high, i.e., when the detection body D is in a relatively close position relative to the detection surface 17. Therefore, when using the cap nut 96, the operating mode of the proximity sensor 100 can be switched to a short-distance mode or a metal-based mode. However, the shorter the detection distance of the proximity sensor 100, the higher the probability of collision between the detection body D and the detection surface 17. Therefore, the operating mode of the proximity sensor 100, and consequently the detection distance of the proximity sensor 100, can be appropriately set within a range that balances reducing the probability of collision with improving detection accuracy.

[0200] <First Variation>

[0201] Figure 20 This is a diagram showing a first modified example of the proximity sensor 100. Figure 21 This is a diagram showing the external shape of the proximity sensor 100 in the first modified example. In addition to the aforementioned sensing head 101, the proximity sensor 100 of this modified example also includes a repeater amplifier 102 and a cable 103.

[0202] The repeater amplifier 102 is separately disposed from the sensor head 101 and is connected to the sensor head 101 via a cable 103. The repeater amplifier 102 receives detection signals, such as the aforementioned first detection signal and second detection signal, from the sensor head 101 via the cable 103. The repeater amplifier 102 has the aforementioned detection unit 26. The repeater amplifier 102 outputs the detection result (ON / OFF) obtained by the detection unit 26 to the external device 200. The repeater amplifier 102 and the external device 200 can also be physically separated by the installation and removal of connectors, etc.

[0203] On the other hand, the sensor head 101, repeater amplifier 102, and cable 103 are provided to the user in a non-separable manner. The distance between the sensor head 101 and the repeater amplifier 102 can be, for example, about 30 cm. The repeater amplifier 102 can be understood as housing components that cannot be housed in the sensor head 101, such as the aforementioned detection unit 26, as a separate unit. Therefore, the structure of the repeater amplifier 102 can be relatively simple. Such a repeater amplifier 102 can be understood as a non-separable part connected to the sensor head 101 and, consequently, to the aforementioned housing body 11.

[0204] Furthermore, in the proximity sensor 100 of this modified example, at least one of the aforementioned operation unit 15 and display unit 16 may be disposed in the relay amplifier 102.

[0205] <Second Variation>

[0206] Figure 22 This is a diagram illustrating a second modified example of the proximity sensor 100. This modified example can be understood as being similar to the aforementioned second modified example ( Figure 20 Comparative example for comparison. Described according to this figure, the proximity sensor 100 of this modified example has a discrete amplifier 104 instead of a relay amplifier 102.

[0207] The separate amplifier 104 is separately configured from the sensor head 101, receiving detection signals from the sensor head 101 and outputting detection results (ON / OFF) to the external device 200. The separate amplifier 104 and the external device 200 can also be physically separated via connector installation or removal. In these respects, there is no particular difference between the repeater amplifier 102 and the separate amplifier 104.

[0208] However, unlike the repeater amplifier 102, the separate amplifier 104 is provided to the user in a state that allows it to be separated from the sensor head 101. That is, the sensor head 101 and the separate amplifier 104 can also be physically separated by means of connector installation or removal. The distance between the sensor head 101 and the separate amplifier 104 can be, for example, about 2 meters. The separate amplifier 104 can be understood as a component that adds various additional functions to the proximity sensor 100. Therefore, the structure of the separate amplifier 104 may be relatively complex. At first glance, such a separate amplifier 104 may seem the same as the repeater amplifier 102, but it is not equivalent to the aforementioned non-separable part.

[0209] <Other variations>

[0210] Furthermore, in addition to the embodiments described above, various modifications can be made to this invention without departing from the spirit of its technical creation.

[0211] For example, in the above embodiment, an external thread 12 is shown as the mounting part of the proximity sensor 100. However, the mounting part of the proximity sensor 100 is not limited to this, and may also be a headless screw, a fixing screw, or a split clamp.

[0212] Alternatively, the operating unit 15 can be a fine-tuning structure that can be rotated using a flathead screwdriver or the like. Or, the operating unit 15 can be a dial structure that rotates along the circumference of the housing 10. In these cases, the operating unit 15 also serves as the display unit 16. That is, the notification unit for the operating mode is not limited to the display unit 16; the operating mode can be mechanically indicated by rotating a gauge or dial, or it can be notified by sound or a buzzer.

[0213] Therefore, the above embodiments should be considered illustrative rather than restrictive in all respects. Furthermore, it should be understood that the scope of protection of this invention is defined by the claims, including all modifications falling within the meaning and scope equivalent to the claims.

[0214] Explanation of reference numerals in the attached figures

[0215] 10. Outer shell (casing)

[0216] 11. Main body of the outer shell

[0217] 111 Through hole

[0218] 112 Substrate fixing groove

[0219] 12 External thread (mounted part)

[0220] 13. Base of outer casing (notification section)

[0221] 14 Cable mounting ports

[0222] 15. Operations Department (Reception Department)

[0223] 151 key components

[0224] 152 key top

[0225] 153 Flanged Construction

[0226] 16. Display Department (Notification Department)

[0227] 17 Inspection Surfaces

[0228] 19 Cables

[0229] 20 coils

[0230] 21 First coil

[0231] 22 Second coil

[0232] 25 sensor units

[0233] 26. Testing Department

[0234] 30 Ferrite Core

[0235] 31 shafts

[0236] 32. Peripheral wall

[0237] 40-core retainer

[0238] 50 substrate

[0239] 51 Switch

[0240] 52 Filler

[0241] 53. Cushioning material

[0242] 60 Receiver Circuit

[0243] 61 First Receiving Circuit

[0244] 62 Second Receiving Circuit

[0245] 70 Transmitting Circuit

[0246] 76 Control Circuit

[0247] 80 Electrical shielding components

[0248] 90 Magnetic shielding components

[0249] 95 Resin Cap

[0250] 96. Cap nut (cap-shaped metal component)

[0251] 96a Metal Sheet Department

[0252] 96a1 Thin Plate Section

[0253] 96a2 thick plate part

[0254] 96b Non-through hole

[0255] 96b1 internal thread

[0256] 96b2 large diameter area

[0257] 96b3 concave part

[0258] 100 Proximity Sensor (Inductive Proximity Sensor)

[0259] 101 sensor head

[0260] 102 Repeater Amplifier

[0261] 103 cable

[0262] 104 Discrete Amplifier

[0263] 200 external devices

[0264] A magnetic flux line received only by the first coil

[0265] B. Magnetic flux lines received by both the first and second coils.

[0266] C. Magnetic flux lines received only by the second coil

[0267] D. Detector (metallic object)

[0268] E. Mounting components (metallic bodies)

[0269] E1 Installation Accessories

[0270] E2 Nut

[0271] F Metal Plate Section

[0272] M First received waveform (first detection signal)

[0273] S Second received waveform (second detection signal)

[0274] S1 First End

[0275] S2 Second End

[0276] S3 midpoint

[0277] T1 Excitation current supply period

[0278] T2 is the period during which the excitation current supply stops (non-integral period).

[0279] During the T3 excitation current supply stoppage period (integration period)

Claims

1. An inductive proximity sensor, comprising: A detection coil that generates a detection signal based on a magnetic field; A cylindrical housing that houses the detection coil, with the detection surface as its bottom surface; and A cap-shaped metal component, detachable from the housing, covers the detection surface when installed on the housing. in, When the housing is installed onto a mounting member having a through hole, with the housing positioned inside the through hole, the cap-shaped metal member is installed onto the housing from the side where the detection surface is located relative to the mounting member.

2. The inductive proximity sensor according to claim 1, wherein, The outer circumferential surface of the housing is provided with external threads, and the cap-shaped metal component is a cap-shaped nut that can be screwed into the external threads.

3. The inductive proximity sensor according to claim 2, wherein, A recess is provided on the inner circumferential surface of the cap nut, and when the cap nut is installed on the housing, a gap is generated in the circumferential direction at the front end of the housing containing the detection surface.

4. The inductive proximity sensor according to claim 2, wherein, The cap-shaped nut has a metal plate portion that covers the detection surface. The metal plate portion includes a thin plate portion disposed in the central portion of the metal plate portion and a thick plate portion disposed in the outer edge portion of the thin plate portion.

5. The inductive proximity sensor according to claim 4, wherein, The thickness of the thin plate portion is 0.35mm to 1.0mm, and the thickness of the thick plate portion is 0.1mm to 0.6mm thicker than the thickness of the thin plate portion.

6. The inductive proximity sensor according to claim 1, wherein, The detection coil is located on the front end side of the detection surface in the normal direction of the detection surface, which is closer to the front end than the opening surface of the cover-shaped metal member.

7. The inductive proximity sensor according to claim 1, comprising: The detection unit detects the detection object based on the detection signal generated by the detection coil; and The receiving department accepts the selection of any one of multiple modes, which are the operating modes of the detection department and have different detectable distances of the detection body.

8. The inductive proximity sensor according to claim 1, comprising: The detection unit detects the detection object based on the detection signal generated by the detection coil; and The operations department accepts user instruction commands. in, The detection unit changes the detection method of the detection body based on the detection signal according to the type of the cover-shaped metal component when the operation unit accepts the teaching operation. The detection unit performing the modified detection method does not detect the cap-shaped metal component, but detects the detection body.

9. The inductive proximity sensor according to claim 1, wherein, It has a transmitting circuit that periodically supplies pulsed excitation current to the detection coil. The detection coil generates a magnetic field during the supply of excitation current and generates the detection signal based on the magnetic field during the cessation of the supply of excitation current.

10. The inductive proximity sensor according to claim 1, wherein, The device includes a detection unit that detects a detection object based on the detection signal generated by the detection coil. The detection coil includes: a first coil that generates the magnetic field during the supply of excitation current and generates a first detection signal based on the magnetic field during the cessation of the supply of excitation current; and a second coil that generates a second detection signal based on the magnetic field during the cessation of the supply of excitation current. The detection unit detects the detection object based on the first detection signal and the second detection signal.

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