JP5115084B2 - Proximity sensor - Google Patents

Description

  The present invention relates to a proximity sensor, and more particularly to a proximity sensor including a detection coil and an auxiliary coil.

  The proximity sensor (switch) is a general term for sensors that detect the movement or presence of a detection target and output the detection result as an electrical signal. As a detection method for replacing the detection result with an electric signal, for example, there is a method using an eddy current generated on the surface of a metal body to be detected by electromagnetic induction.

  In order to generate an eddy current on the surface of the metal body, it is necessary to temporally change the magnetic flux linked to the metal body. Proximity sensors that employ the above-described detection method generally include a coil (hereinafter referred to as “detection coil”) for generating the magnetic field.

  In addition, a proximity sensor that includes not only a detection coil but also a coil that generates a magnetic field for adjusting the magnetic field of the detection coil (hereinafter, this coil is referred to as an “auxiliary coil”) has been proposed. For example, Japanese Patent No. 2603628 (Patent Document 1) discloses a high-frequency oscillation type proximity switch having a sensor portion in which an auxiliary coil is wound around the outer periphery of both ends of a detection core. In this proximity switch, the detection coil is inserted into a pot-shaped core, and the auxiliary coil is wound around an auxiliary coil case provided outside the E-shaped core. The auxiliary coil and the detection coil are connected in series so that the mutual inductance is negative, and the magnetic flux of the auxiliary coil and the leakage magnetic flux of the detection coil that leaks to the metal when a metal exists near the sensor mounting wall surface Interlink. Thereby, even if the mounting member for mounting the sensor portion having a large diameter is a metal body, the influence on the detection distance due to the leakage magnetic flux can be avoided.

In addition, in Japanese National Patent Publication No. 2002-519903 (Patent Document 2), in a proximity sensor including two windings, the mutual magnetic flux between the two windings is sufficiently weaker than the magnetic flux peculiar to each winding. It is disclosed that two windings are arranged. Thereby, the fluctuation | variation with the temperature of the sensitivity of a proximity sensor can be suppressed. One of the two windings is a coil placed in a ferrite pot and the other is placed in a cage of insulating material that functions as a coil frame.
Japanese Patent No. 2603628 Special table 2002-519903 gazette

  In the proximity sensor disclosed in the above document, the detection coil is attached to the core, and the auxiliary coil is attached to a member other than the core (such as a bobbin). However, the following problems occur in the proximity sensor employing such a configuration.

  For example, in a cylindrical screw-shaped proximity sensor, a screw is formed on the side surface of the case body, and the size of this screw is defined to be a certain size (see, for example, JIS C 8201-5-2). For this reason, in order to mount the bobbin on the outer periphery of the core without changing the diameter of the case body, the diameter of the core must be reduced. However, by reducing the core diameter, the detection coil diameter is also reduced. In this case, the problem that the detection sensitivity of a proximity sensor falls arises.

  In addition, variations in the relative positions of the bobbin and the core may cause variations in characteristics from product to product. Furthermore, in order to prevent this characteristic variation, the proximity sensor must be assembled so that the relative displacement between the bobbin and the core is reduced, which may increase the manufacturing cost.

  Furthermore, since the auxiliary coil is provided outside the core, it is not easy to suppress the spread of the magnetic flux distribution due to the auxiliary coil. When the spread of the magnetic flux produced by the auxiliary coil is suppressed, the leakage magnetic flux of the auxiliary coil to the side of the sensor, that is, the magnetic flux interlinking with the mounting metal (surrounding metal) is reduced, and a magnetic shielding effect is obtained. As a result, the magnetic flux from the detection coil can be concentrated toward the detection target, so that the detection sensitivity can be increased. However, when the spread of the magnetic flux distribution due to the auxiliary coil cannot be sufficiently suppressed, a sufficient magnetic shield effect cannot be obtained, so that the detection sensitivity cannot be further increased.

  As a method for suppressing the spread of the magnetic flux distribution by the auxiliary coil, for example, it is conceivable to add a member having a high magnetic permeability outside the auxiliary coil. However, in this case, there is a problem that the cost increases.

  The present invention has been made to solve these problems, and an object of the present invention is to enable improvement in detection sensitivity and cost reduction in a proximity sensor including a detection coil and an auxiliary coil.

  In summary, the present invention is a proximity sensor that detects the presence or position of a metal body using a magnetic field, and includes a detection coil, a core, and an auxiliary coil. The detection coil generates a magnetic field. The core includes a tubular portion, a bottom portion that closes one end of the tubular portion, and a flange provided on the outer surface of the tubular portion, and houses the detection coil in the tubular portion. The auxiliary coil is directly wound around a portion from the other end of the cylindrical portion to the flange portion on the outer surface of the cylindrical portion, and generates a magnetic field that adjusts the direction of the magnetic field generated from the detection coil.

  Preferably, when the outer surface of the cylindrical portion is used as a reference, the height of the collar portion is larger than the height of the auxiliary coil.

  More preferably, the detection coil is housed inside the cylindrical portion in a state of being hardened so as to maintain its own shape. The core further includes a central shaft portion connected to the bottom portion and through which the detection coil is passed.

More preferably, the cylindrical portion, the bottom portion, the flange portion, and the central shaft portion are integrally formed.
More preferably, the core includes a component in which the cylindrical portion and the flange portion are integrated, and a component in which the bottom portion and the central shaft portion are integrated.

  More preferably, the proximity sensor further includes a spool around which the detection coil is wound. The detection coil is housed inside the cylindrical portion together with the spool.

  More preferably, the proximity sensor periodically applies a pulsed excitation current to the detection coil, and compares a voltage induced in the detection coil by a magnetic field change around the metal body generated after the excitation current is cut off with a predetermined threshold value. By doing this, the presence or absence of a metal body is detected.

  According to the present invention, it is possible to improve the detection sensitivity of the proximity sensor and reduce the cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view showing the structure of the proximity sensor according to Embodiment 1 of the present invention. FIG. 2 is an exploded perspective view showing the assembly structure of the proximity sensor shown in FIG. First, the structure of the proximity sensor in the present embodiment will be described with reference to FIG. 1 and FIG.

  As shown in FIGS. 1 and 2, the proximity sensor 100 in the present embodiment has a substantially columnar outer shape, and has a cylindrical case body 110 and a front of the case body 110 inside the case body 110. The detection unit assembly 120 attached to the end and the output unit assembly 130 attached to the rear end of the case body 110 inside the case body 110 are mainly provided. The detection unit assembly 120 includes a detection coil 121, an auxiliary coil 122, a ferrite core 123A, a coil case 124, a detection circuit board 125, a primary casting resin layer 126, and the like. Here, the primary casting resin layer 126 includes a coil assembly including the detection coil 121, the auxiliary coil 122, and the ferrite core 123A, and a detection circuit board 125 connected to the coil assembly inside the coil case 124. It is a member for fixing, and is a layer formed by filling molten resin in the coil case 124 and curing it. The output unit assembly 130 includes an output circuit board 131.

  The detection circuit board 125 of the detection unit assembly 120 attached to the front end of the case body 110 and the output circuit board 131 of the output part assembly 130 attached to the rear end of the case body 110 are connected by the connection member 140. Has been. In the proximity sensor 100 according to the present embodiment, the detection circuit board 125 and the output circuit board 131 are both formed of a rigid wiring board, and the connection member 140 is formed of a flexible wiring board.

  Here, the rigid wiring board is a wiring board having high rigidity such as a glass-epoxy board, and is suitable for mounting electronic components. On the other hand, a flexible wiring board is a wiring board that is more flexible than a rigid wiring board. For example, a conductive pattern is bonded to the main surface of a base material made of polyimide resin with an adhesive or the like. It is a printed wiring board. Since this flexible wiring board is moderately flexible, it can be bent or folded back freely. As a wiring board that relays the connection between the conductive patterns of the rigid wiring boards that are spaced apart from each other. It is available.

  The case body 110 includes a metal case 111 and a resin case 112, and is configured by press-fitting the resin case 112 into the rear end of the metal case 111. A slit-like opening 113 is formed in the rear end surface of the resin case 112, and the rear end of the output circuit board 131 is inserted and disposed so as to penetrate the opening 113. That is, in the proximity sensor 100 according to the present embodiment, the case body 110 is configured by the metal case 111 and the resin case 112, and the opening 113 provided at the rear end portion of the case body 110 is included. An output circuit board 131 as a wiring member is inserted and arranged.

  The terminal of the external connection cord 150 is joined to the output circuit board 131 at a portion located outside the case body 110 by soldering. A cord protector 160 as an outer resin sealing layer is provided at the rear end of the case body 110 by insert molding so as to cover the solder joint between the output circuit board 131 and the external connection cord 150. The space inside the case body 110 is filled with a secondary casting resin layer 180 as an inner resin sealing layer.

  The detection circuit board 125 is provided with a detection circuit having the detection coil 121 and the auxiliary coil 122 as circuit elements. The detection coil 121 generates a magnetic field for detecting a metal body that is a detection target. The auxiliary coil 122 generates a magnetic field that adjusts the direction of the magnetic field generated from the detection coil 121. The auxiliary coil 122 is connected in series with the detection coil 121, and the winding direction is opposite to the winding direction of the detection coil 121.

  A pulsed excitation current periodically flows through the detection coil 121. The frequency of this exciting current is several kHz, for example. Thereby, the detection coil 121 and the auxiliary coil 122 are excited. A resistor (not shown) is connected to both ends of the detection coil 121.

  When the detection target does not exist within the detectable range of the proximity sensor 100, the current flowing through the detection coil 121 itself after the supply of the excitation current to the detection coil 121 is cut off is connected to both ends of the detection coil 121. Decreases rapidly by resistance. Therefore, when there is no detection target, the voltage between both ends of the detection coil increases due to the back electromotive force of the detection coil itself immediately after the supply of the excitation current is cut off, but then decays rapidly thereafter.

  On the other hand, when the metal object to be detected is approaching, when the supply of the excitation current to the detection coil is interrupted, the magnetic field around the metal object (the magnetic field by the detection coil 121) changes. Therefore, an eddy current is generated in the metal body. An induced voltage is generated in the detection coil 121 by the magnetic flux generated by the eddy current passing through the detection coil 121. As a result, when a certain time (for example, several tens of microseconds) elapses after the supply of the excitation current to the detection coil 121 is interrupted, the induced voltage becomes dominant as the voltage across the detection coil 121. . Therefore, the presence / absence or position of the detection target can be detected by comparing the voltage across the detection coil 121 at this time with a threshold value.

  When the detection coil 121 is excited by the above-described method, the induced voltage reflects the time change of the eddy current flowing in the metal body. The detection coil 121 plays a role of converting the temporal change of the eddy current into a voltage. This voltage is not easily affected by components having temperature dependency such as loss of the detection coil and parasitic capacitance. Therefore, it is possible to make it less susceptible to temperature changes during detection.

  The detection circuit may include an oscillation circuit having the detection coil 121 as a resonance circuit element, and a discrimination circuit that binarizes the oscillation amplitude of the oscillation circuit with a threshold value. In this case, the proximity sensor 100 detects the presence or absence of the detection target or the detection target by detecting the decrease in the oscillation amplitude of the oscillation circuit or the stop of the oscillation that occurs when the detection target (metal body) approaches the detection coil 121. Detect position. In such a system, an excitation current having a frequency of, for example, several hundred kHz and continuously changing (for example, the waveform is a sine wave) is applied to the detection coil 121.

  The output circuit board 131 is provided with an output circuit for converting the output of the detection circuit into a voltage output or a current output of a predetermined specification, and the output is led to the outside through the external connection cord 150. . The output circuit board 131 is also provided with a power supply circuit that converts the power introduced from the outside via the external connection cord 150 into a predetermined power supply specification and outputs it to the detection circuit board 125.

  FIG. 3 is a schematic cross-sectional view for explaining the structure of the coil assembly included in the proximity sensor shown in FIG. FIG. 4 is an external view of the ferrite core 123A shown in FIG.

  Referring to FIGS. 3 and 4, ferrite core 123 </ b> A includes cylindrical portion 171, bottom portion 172 that closes one end of cylindrical portion 171, flange portion 173 provided on the outer surface of the cylindrical portion, and bottom portion 172. And a central shaft portion 174 connected to the surface of the main body. As shown in FIGS. 3 and 4, the cylindrical portion 171, the bottom portion 172, the flange portion 173, and the middle shaft portion 174 are integrally formed.

  As shown in FIG. 3, the detection coil 121 is housed inside the cylindrical portion 171 while being passed through the middle shaft portion 174. As will be described later, the detection coil 121 is housed inside the cylindrical portion 171 in a state of being hardened so as to maintain its own shape. The auxiliary coil 122 is located on the outer surface of the tubular portion 171 and is located at the opening end of the tubular portion 171 (that is, the end of the two ends of the tubular portion 171 opposite to the end connected to the bottom portion 172). Part) to the flange part 173.

  The height h1 of the flange portion 173 with respect to the outer surface of the cylindrical portion 171 is designed to be higher than the height h2 of the auxiliary coil 122 with respect to the outer surface of the cylindrical portion 171. In addition, when viewed from a direction perpendicular to the outer surface of the cylindrical portion 171, at least a part of the auxiliary coil 122 overlaps the detection coil 121.

  FIG. 5 is a diagram showing a manufacturing process of the coil assembly. Referring to FIG. 5, first, in step S <b> 1, the winding process of detection coil 121 is performed. The conducting wire used for the detection coil 121 is, for example, a self-bonding wire. As a winding method, for example, laminated winding is used. By heating after the self-bonding wire has been wound, the fusion layers of the self-bonding wire are fixed to each other. Thereby, the detection coil 121 is hardened so as to maintain its own shape, and becomes an air-core coil.

  On the other hand, in step S2, the auxiliary coil 122 is produced. In step S2, the self-bonding wire is wound around the ferrite core 123A. Further, the fused layer is fixed by heating the self-bonding wire.

  It should be noted that other methods can be used as methods for fixing the shapes of the detection coil 121 and the auxiliary coil 122. For example, the shape of the winding may be fixed using enamel or resin adhesive. That is, the conducting wire for forming the detection coil 121 and the auxiliary coil 122 is not limited to the self-bonding wire.

In step S3 following step S2, a characteristic inspection of the auxiliary coil 122 is performed.
When the processes of step S1 and step S3 are completed, the process of step S4 is executed. In step S4, the detection coil 121 is housed in the cylindrical portion 171 and the detection coil 121 is fixed with a resin adhesive.

  Subsequently, in step S5, the characteristic inspection of the detection coil 121 is performed. When the process of step S5 ends, the coil assembly manufacturing process ends. Note that as shown in FIG. 5, the order of the manufacturing processes does not have to be limited, and the order of the processes can be appropriately changed.

  The proximity sensor of this embodiment can be suitably used as a “shield type” proximity sensor. This is because proximity sensors are generally classified into either “shield type” or “non-shield type”, but the auxiliary coil is mounted on a “shield type” proximity sensor. In this regard, first, a “shield type” proximity sensor and a “non-shield type” proximity sensor will be described.

  FIG. 6 is a diagram illustrating a shield type proximity sensor and a non-shield type proximity sensor. 6A is a diagram illustrating a shield type proximity sensor, and FIG. 6B is a diagram illustrating a non-shield type proximity sensor. Note that the proximity sensor shown in FIG. 6A does not include an auxiliary coil. The reason for this will be described later.

  As shown in FIG. 6A, in the case of a shield-type proximity sensor, the metal case 111 is formed so that the tip of the metal case 111 is positioned in the vicinity of the detection surface A (the surface of the coil case 124). Thereby, when attaching a proximity sensor to the surrounding metal (surrounding metal 190), a level difference can be prevented from being generated between the detection surface A and the surface of the surrounding metal 190. That is, the shield type proximity sensor can be embedded in the surrounding metal 190.

  In the coil case 124, a ferrite core 123 (for example, a pot-shaped core) and a detection coil 121 are provided. It is assumed that the detection circuit having the detection coil 121 and the ferrite core 123 as circuit elements is a high-frequency oscillation circuit. The reason is that a certain degree of magnetic shielding effect can be obtained without an auxiliary coil.

  A continuously changing excitation current (for example, an excitation current having a sine wave waveform) flows through the detection coil 121. The frequency of the excitation current is determined to be about several hundred kHz, for example.

  The depth at which the magnetic flux F generated by the detection coil 121 penetrates into the metal case 111 (that is, the skin depth) decreases as the frequency of the excitation current increases, but the magnetic flux F does not pass through the metal case 111. Further, the magnetic flux F generated by the detection coil 121 penetrates into the metal case 111, so that an eddy current flows through the metal case 111. The direction of the magnetic flux generated by the eddy current is a direction that cancels the magnetic flux F generated by the detection coil 121. As a result, the shape of the magnetic flux distribution from the detection coil 121 is deformed so that the magnetic flux F is concentrated on the tip of the open magnetic path, that is, the detection surface A. That is, on the side of the proximity sensor (direction parallel to the surface of the surrounding metal 190), an effect (magnetic shielding effect) in which the magnetic flux F generated by the detection coil 121 is shielded by the surrounding metal 190 is obtained.

  On the other hand, as shown in FIG. 6B, in the case of a non-shielded proximity sensor, the detection surface A is located in front of the tip of the metal case 111, so that it cannot be embedded in surrounding metal. In the case of a non-shielded proximity sensor, for example, a T-type core is used as the ferrite core 123, and the detection surface A is projected forward from the tip of the metal case 111. As a result, since the magnetic flux F can be greatly spread in front of the detection surface A, the presence / absence or position of the detection target can be detected even if the distance between the detection target and the detection surface A is increased. In the non-shield type, the magnetic flux on the side of the proximity sensor is not shielded.

  In the case of a shield type proximity sensor, in order to concentrate the magnetic flux F in front of the detection surface A, it is required to suppress the spread of the magnetic flux of the detection coil to the side of the sensor. Here, in the case of a system in which the detection coil is excited by applying a pulse current to the detection coil, the frequency of the current is set to about several kHz, for example. In this case, when the magnetic flux of the detection coil 121 passes through the metal case 111, the magnetic shield effect may not be sufficiently obtained. However, this problem can be avoided by providing an auxiliary coil.

  FIG. 7 is a diagram illustrating the direction of magnetic flux from the detection coil and the direction of magnetic flux from the auxiliary coil. Referring to FIG. 7, auxiliary coil 122 is arranged outside detection coil 121. That is, the diameter of the auxiliary coil 122 is larger than the diameter of the detection coil 121. The detection coil 121 and the auxiliary coil 122 are connected in series. The winding direction of the detection coil 121 and the auxiliary coil 122 is opposite.

  When an excitation current flows through the detection coil 121 and the auxiliary coil 122, magnetic fluxes F and Fc are generated by the detection coil 121 and the auxiliary coil 122, respectively. Since the winding directions of the detection coil 121 and the auxiliary coil 122 are opposite, the direction of the magnetic flux Fc and the direction of the magnetic flux F are opposite to each other. That is, the direction of the magnetic flux Fc is a direction in which the magnetic flux F is canceled. Thereby, since the spread of the magnetic flux F to the side of the proximity sensor can be suppressed, a magnetic shield effect can be obtained. That is, since the magnetic flux F can be concentrated in front of the detection surface A, the detection sensitivity can be increased.

  Thus, when the frequency of the excitation current is low, an auxiliary coil is provided to obtain a magnetic shield effect. However, even when a continuously changing current is applied to the detection coil, an auxiliary coil may be required depending on the frequency of the current. Therefore, an auxiliary coil may be used to obtain a magnetic shielding effect even when a continuously changing current is applied to the detection coil.

  Since the auxiliary coil 122 is a thin coil, it is not easy to make it as an air-core coil in advance like the detection coil 121. Therefore, in order to produce an auxiliary coil, it is necessary to wind a conducting wire around some member. In the present embodiment, auxiliary coil 122 is wound directly on the outer surface of ferrite core 123A. This eliminates the need for a member (bobbin) for winding the auxiliary coil 122.

  By eliminating the need for the bobbin, the following effects can be obtained. First, since the bobbin is unnecessary, the cost can be reduced.

  Furthermore, since the diameter of the ferrite core 123A can be increased, the diameter of the detection coil 121 can also be increased. Thereby, detection sensitivity can be improved.

  Furthermore, since the height of the auxiliary coil 122 is smaller than the height of the collar portion, the width of the magnetic flux leaking from the auxiliary coil 122 to the outside of the ferrite core 123A is reduced. That is, the width of the magnetic flux of the auxiliary coil 122 that leaks to the side of the sensor can be reduced. This means that the spread of the magnetic flux of the auxiliary coil 122 toward the sensor side is suppressed. As a result, the magnetic flux of the detection coil 121 is also prevented from spreading to the side of the sensor. That is, an excellent magnetic shielding effect can be obtained. Therefore, the detection sensitivity of the proximity sensor can be improved. Furthermore, since a magnetic shielding effect can be obtained without providing a high permeability member outside the auxiliary coil 122, the cost of the proximity sensor can be reduced.

  Further, by providing the flange portion 173 on the outer surface of the cylindrical portion 171, the accuracy of the relative position between the detection coil 121 and the auxiliary coil 122 can be stabilized when the coil assembly is assembled. As a result, it is possible to avoid that the spread of the magnetic flux of the detection coil 121 and the spread of the magnetic flux of the auxiliary coil 122 are greatly different between individuals, so that the variation in the detection performance of the proximity sensor can be reduced. .

[Embodiment 2]
The overall configuration of the proximity sensor according to the second embodiment is substantially the same as that of the first embodiment, but the structure of the ferrite core is different from that of the first embodiment. Therefore, the ferrite core of the proximity sensor according to the second embodiment will be mainly described below. Since other parts of the proximity sensor according to the second embodiment are the same as the corresponding parts of the proximity sensor according to the first embodiment, the following description will not be repeated.

  FIG. 8 is a schematic cross-sectional view for explaining the structure of the coil assembly included in the proximity sensor according to the second embodiment. Referring to FIG. 8, ferrite core 123B includes a cylindrical portion 171A, a bottom portion 172A that closes one end of cylindrical portion 171A, a flange portion 173A provided on the outer surface of cylindrical portion 171A, and the surface of bottom portion 172A. And a middle shaft portion 174 connected to. The detection coil 121 is housed inside the cylindrical portion 171A while being passed through the central shaft portion 174. The auxiliary coil 122 is wound directly on the outer surface of the cylindrical portion 171 around a portion from the open end of the cylindrical portion 171A to the flange portion 173A.

  The cylindrical portion 171A and the flange portion 173A are integrally formed and are components that constitute the ferrite core 123B. Further, the bottom portion 172A and the middle shaft portion 174 are integrally formed as parts different from the cylindrical portion 171A and the flange portion 173A. The cylindrical portion 171A (and the flange portion 173A) is fixed in a state of being in contact with the bottom portion 172A by, for example, a resin-related adhesive.

  The bottom portion 172A and the middle shaft portion 174 constitute a T-type core. As shown in FIG. 6, the T-type core is used for a non-shielded proximity sensor. According to the second embodiment, the T-core can be used not only as a non-shield type proximity sensor but also as a part of the ferrite core 123. According to the second embodiment, since the T-type core can be shared by the non-shielded type and the shield type, the manufacturing cost of the proximity sensor can be reduced.

  If the ferrite core includes a part in which the cylindrical part and the flange part are integrally formed and a part in which the bottom part and the central shaft part are integrally formed, the shape of the cylindrical part, the flange part and the bottom part Is not limited as shown in FIG. For example, a ferrite core configured as shown below may be used for the proximity sensor.

(Modification example of ferrite core)
FIG. 9 is a diagram illustrating a modification of the ferrite core included in the proximity sensor according to the second embodiment. Referring to FIG. 9, ferrite core 123C includes a cylindrical portion 171B, a bottom portion 172B that closes one end of cylindrical portion 171B, and a flange portion 173B provided on the outer surface of cylindrical portion 171B. The cylindrical portion 171B and the flange portion 173B are integrally formed. Similarly, the bottom portion 172B and the middle shaft portion 174 are integrally formed. As can be seen by comparing FIG. 9 and FIG. 3, the cylindrical portion 171B, the flange portion 173B, and the bottom portion 172B correspond to the cylindrical portion 171, the flange portion 173, and the bottom portion 172 shown in FIG.

[Embodiment 3]
The overall configuration of the proximity sensor according to the third embodiment is substantially the same as that of the first embodiment, but the configuration of the detection coil housed in the ferrite core is different from that of the first embodiment. Therefore, the detection coil will be mainly described below in the proximity sensor according to the third embodiment. Since other parts of the proximity sensor according to the third embodiment are the same as the corresponding parts of the proximity sensor according to the first embodiment, the following description will not be repeated.

  FIG. 10 is a schematic cross-sectional view for explaining the structure of the coil assembly included in the proximity sensor according to the third embodiment. Referring to FIG. 10, the coil assembly is different from the coil assembly shown in FIG. 3 in that it further includes a spool 175 around which detection coil 121 is wound. However, the structure of the other part of the coil assembly shown in FIG. 10 is the same as the structure of the corresponding part of the coil assembly shown in FIG. A through hole is formed at the center of the spool 175. The detection coil 121 is housed inside the cylindrical portion 171 by passing the central shaft portion 174 through the through hole.

  The spool 175 includes two pin terminals 176. Each of the two pin terminals 176 is passed through a hole formed in the bottom 172. The lead wire from the detection coil 121 is wound around the pin terminal 176 and is electrically connected.

  In the third embodiment, ferrite core 123B shown in FIG. 8 or ferrite core 123C shown in FIG. 9 may be used instead of ferrite core 123A.

  Generally, a conductive wire having a thin wire diameter is used for the detection coil. When soldering both ends of the detection coil to the circuit board, if the lead wire is directly connected to the circuit board, disconnection is likely to occur, and it may be necessary to perform connection work. However, since the pin terminal 176 can be soldered to the circuit board in the third embodiment, such a problem can be avoided.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

It is a schematic cross section which shows the structure of the proximity sensor in Embodiment 1 of this invention. It is a disassembled perspective view which shows the assembly | attachment structure of the proximity sensor shown in FIG. It is a cross-sectional schematic diagram for demonstrating the structure of the coil assembly contained in the proximity sensor shown in FIG. It is an external view of the ferrite core 123A shown in FIG. It is a figure which shows the manufacturing process of a coil assembly. It is a figure which shows a shield type proximity sensor and a non-shield type proximity sensor. It is a figure explaining the direction of the magnetic flux from a detection coil, and the direction of the magnetic flux from an auxiliary coil. 6 is a schematic cross-sectional view for explaining the structure of a coil assembly included in a proximity sensor according to Embodiment 2. FIG. It is a figure which shows the modification of the ferrite core with which the proximity sensor which concerns on Embodiment 2 is provided. 10 is a schematic cross-sectional view for explaining the structure of a coil assembly included in a proximity sensor according to Embodiment 3. FIG.

Explanation of symbols

  100 proximity sensor, 110 case body, 111 metal case, 112 resin case, 113 opening, 120 detector assembly, 121 detection coil, 122 auxiliary coil, 123, 123A, 123B, 123C ferrite core, 124 coil case, 125 detection Circuit board, 126 Primary casting resin layer, 130 Output assembly, 131 Output circuit board, 140 Connection member, 150 External connection cord, 160 Code protector, 171, 171A, 171B Cylindrical part, 172, 172A, 172B Bottom , 173, 173A, 173B collar part, 174 middle shaft part, 175 spool, 176 pin terminal, 180 secondary cast resin layer, 190 surrounding metal, A detection surface, F, Fc magnetic flux.

Claims (7)

A proximity sensor that detects the presence or position of a metal body using a magnetic field,
A detection coil for generating the magnetic field;
A core that includes a tubular portion, a bottom portion that closes one end of the tubular portion, and a flange provided on an outer surface of the tubular portion, and that houses the detection coil in the tubular portion; ,
A magnetic field that is directly wound around a portion of the outer surface of the cylindrical portion from the other end of the cylindrical portion to the flange and adjusts the direction of the magnetic field generated from the detection coil is generated. A proximity sensor comprising an auxiliary coil.   2. The proximity sensor according to claim 1, wherein a height of the flange portion is larger than a height of the auxiliary coil when the outer surface of the cylindrical portion is used as a reference. The detection coil is housed inside the cylindrical portion in a state of being hardened so as to maintain its own shape,
The proximity sensor according to claim 1, wherein the core further includes a middle shaft portion that is connected to the bottom portion and through which a detection coil is passed.   The proximity sensor according to claim 3, wherein the cylindrical portion, the bottom portion, the flange portion, and the middle shaft portion are integrally formed. The core is
A component in which the tubular portion and the flange portion are integrated;
The proximity sensor according to claim 3, comprising a part in which the bottom part and the middle shaft part are integrated. The proximity sensor is
A spool around which the detection coil is wound;
The proximity sensor according to claim 1, wherein the detection coil is housed in the cylindrical portion together with the spool.   The proximity sensor periodically applies a pulsed excitation current to the detection coil, and compares a voltage induced in the detection coil by a magnetic field change around the metal body generated after the excitation current is cut off with a predetermined threshold value. The proximity sensor of any one of Claim 1 to 6 which detects the presence or absence of a metal body by doing.

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