JP2008277051A - Magnetic proximity switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a magnetic proximity switch capable of enlarging an off-area without arranging a magnet to be detected at a position away from the center of a lead switch and capable of obtaining a desired off-distance. <P>SOLUTION: For the magnetic proximity switch provided with a lead switch 1 putting on and off a contact in accordance with magnetic force changing according to a position of a permanent magnet 3, a magnetic shielding plate 4 is arranged for covering at least a part of the contact 2 of the lead switch 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic proximity switch having a reed switch that turns on and off a contact in accordance with a magnetic force that changes depending on the position of a detected magnet.

  The conventional magnetic proximity switch is, for example, “a proximity switch arranged on a substrate, including a case and a reed switch accommodated in the case, and the case holds a lead terminal of the reed switch. In the proximity switch having the press-fitting portion, the press-fitting portion has a holding force sufficient to maintain the height of the reed switch with respect to the substrate in the case, and only the press-fitting portion has the inside of the case. The proximity switch is characterized in that the reed switch is fixed (see, for example, Patent Document 1).

JP 2000-14741 A (Claim 1)

  In general, a conventional magnetic proximity switch is used, for example, as a sensor that detects opening / closing of a lid or the like, or as a sensor that measures the flow rate of gas or liquid. Basically, it operates with a combination of a detected magnet (for example, a permanent magnet) and a magnetic proximity switch, but this detected magnet is installed on the object to be detected or linked to the object to be detected. The detection is performed by operating the reed switch in the magnetic proximity switch by the magnetic attractive force when the detected magnet approaches. This type of magnetic proximity switch uses a reed switch in which reed pieces made of a ferromagnetic material are arranged opposite to each other and sealed in a glass tube.

  In the magnetic proximity switch configured as described above, there are an ON region and an OFF region of the magnetic proximity switch according to the movement of the detected magnet. For applications that incorporate magnetic proximity switches, if a certain length of off and on distances is required, move the sensed magnet away from the center of the reed switch to obtain the desired sensed magnet travel distance. There is a problem that the shape of the application product incorporating the magnetic proximity switch becomes large.

  In addition, by arranging the reed switch so that the axial direction of the reed switch is perpendicular to the magnetic pole direction of the permanent magnet, and utilizing the width of the off region existing near the reed switch contact point (hereinafter referred to as “off distance”), However, there is a problem that a sufficiently long off-distance cannot be obtained due to restrictions on characteristics of the reed switch.

  Therefore, there has been a demand for a magnetic proximity switch that can enlarge the off region without disposing the magnet to be detected at a position away from the center of the reed switch and can obtain a desired off distance.

  The magnetic proximity switch according to the present invention is a magnetic proximity switch having a reed switch that turns on and off the contact in accordance with the magnetic force that changes depending on the position of the magnet to be detected, and a magnetic shielding member that covers at least a part of the reed switch contact is disposed. It is set.

  Further, the magnetic shielding member reduces the magnetic force generated at the contact point of the reed switch, and expands an off region where the contact point is turned off with respect to the detected magnet.

  Moreover, the said magnetic shielding member expands the off area | region of the said contact vicinity among the said off area | regions.

  The magnetic shielding member expands an off area near the contact in the axial direction of the reed switch.

  Further, the reed switch is arranged so that its axial direction is orthogonal to the magnetic pole direction of the detected magnet.

  The magnetic shielding member is formed in a plate shape.

  The magnetic shielding member is formed in a cylindrical shape.

  The magnetic shielding member is formed in a U-shaped cross section.

  In addition, a case containing the reed switch is further provided, and the magnetic shielding member is disposed on an outer surface of the case.

  In addition, a case enclosing the reed switch is further provided, and the magnetic shielding member is disposed inside the case.

  Further, the apparatus further includes a detected magnet and a case containing the detected magnet, the magnetic shielding member, and the reed switch, and the magnetic shielding member is disposed between the contact of the reed switch and the detected magnet. It is arranged.

  In addition, the magnet to be detected is attached to a detection object or an object interlocked with the detection object, and moves inside the case in conjunction with the detection object.

  The detected magnet is made of a permanent magnet.

  In the present invention, by providing a magnetic shielding member that covers at least a part of the contact of the reed switch, an off region where the contact is turned off with respect to the magnet to be detected can be expanded, and a desired off-state can be obtained. The distance can be obtained.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a magnetic proximity switch according to Embodiment 1 of the present invention. In FIG. 1, the magnetic proximity switch includes a reed switch 1 and a magnetic shielding plate 4 which is a magnetic shielding member formed in a plate shape. In the reed switch 1, a contact point 2 is formed by lead pieces arranged opposite to each other in a glass tube, and a permanent magnet 3 which is a detected magnet attached to a detection object or an object interlocking with the detection object is connected to the reed switch 1. , The contact 2 of the reed switch 1 comes into contact by the action of the magnetic attraction force by the permanent magnet 3, and the contact 2 is turned on. On the other hand, when the permanent magnet 3 is separated from the reed switch 1, the action of the magnetic attractive force is reduced, so that the contact 2 is opened by the elastic force of the lead piece, and the contact 2 is turned off. The magnetic shielding plate 4 covers at least a part of the contact 2 of the reed switch 1, reduces the magnetic force generated at the contact 2 by the permanent magnet 3, and expands the off region where the contact 2 is turned off with respect to the permanent magnet 3. It is.

  Here, the reed switch 1 according to the present embodiment is arranged so that its axial direction is orthogonal to the magnetic pole direction of the permanent magnet 3, and uses the ON region and the OFF region existing in the vicinity of the contact 2 to make a permanent switch. A switch operation corresponding to the movement of the magnet 3 is performed. Next, an ON region where the contact 2 is turned on with respect to the position of the permanent magnet 3 and an OFF region where the contact 2 is turned off will be described with reference to FIG.

  FIG. 2 is a diagram for explaining an on / off region of the reed switch according to the first embodiment. 2A is a diagram showing an on / off region when the magnetic shielding plate 4 is not provided, and FIG. 2B is a diagram showing an on / off region when the magnetic shielding plate 4 is provided. In FIG. 2, in the coordinate system in which the origin is at the position of the contact 2, the x axis is in the axial direction of the reed switch 1, and the y axis is perpendicular to the x axis, that is, in the magnetic pole direction of the permanent magnet 3, The contact state of the contact 2 with respect to the position 3 is shown.

  First, in FIG. 2A, an on / off region when the magnetic shielding plate 4 is not provided will be described. When the position of the permanent magnet 3 is the origin position, on the y axis and in the vicinity thereof, the lead pieces of the reed switch 1 are magnetized to the same polarity by the magnetic field generated by the permanent magnet 3, and the contact 2 is turned off (off region). . On the other hand, when the position of the permanent magnet 3 moves in the x-axis direction and exceeds the boundary of the ON region (solid line in FIG. 2A) where the y-axis distance is a predetermined value or less, the magnetic field generated by the permanent magnet 3 The lead pieces of the reed switch 1 are magnetized to different polarities, and the contact 2 is turned on by the action of the magnetic attractive force. Furthermore, when the position of the permanent magnet 3 moves in the x-axis direction or exceeds the off-region boundary (dotted line in FIG. 2A) where the y-axis distance is a predetermined value or more, a lead piece generated by the permanent magnet 3 Thus, the contact 2 is turned off by the mechanical elastic force of the lead piece. When the permanent magnet 3 moves so as to return to the origin position, the boundary of the off region (dotted line in FIG. 2 (a)) is exceeded, and further, the boundary of the on region (solid line in FIG. 2 (a)) is exceeded. The contact 2 is turned on by the action of the magnetic attractive force. As a result, the magnetic proximity switch has a function of outputting an electrical signal on or off as the permanent magnet 3 moves.

  As described above, the on / off region depends on the magnetic field that changes depending on the position of the permanent magnet 3, and the boundary of the on / off region does not coincide with the hysteresis generated in the lead piece, as shown in FIG. The difference is more conspicuous toward both ends of the shaft of the reed switch 1. Using such characteristics of the reed switch 1, when obtaining the movement distance of the detection target to which the permanent magnet 3 is attached, the movement direction is taken on the x axis, the off region on the y axis, the + x direction, and the −x direction. The moving distance of the detection object can be obtained by switching the contact point 2 using the ON regions generated in the directions.

  However, since the off-distance for obtaining the moving distance of the detection object as described above is limited by the characteristics of the reed switch 1, the permanent magnet 3 is used as the lead for obtaining the off-distance of a certain length or more. The switch 1 must be disposed at a position away from the center of the switch 1 by a certain distance in the y-axis direction. Further, since the upper limit value of the off distance is restricted by the characteristics of the reed switch 1, a sufficiently long off distance cannot be obtained. In this case, it is conceivable to use the boundary between the ON region and the OFF region existing on both ends of the shaft of the reed switch 1, but as described above, the ON position is greatly different from the OFF position due to hysteresis generated in the lead piece. It is not possible to use both ends of the spider shaft.

  The operation of the magnetic proximity switch provided with the magnetic shielding plate 4 that can expand the off region and obtain a desired off distance without being restricted by the characteristics of the reed switch 1 will be described below. .

  As shown in FIG. 1, a magnetic shielding plate 4 for shielding a magnetic field generated by the permanent magnet 3 is disposed above the contact 2 of the reed switch 1. The on / off region when the magnetic shielding plate 4 is provided will be described with reference to FIG. As shown in the figure, when the permanent magnet 3 is on the origin position, on the y-axis and in the vicinity thereof, the magnetic shielding plate 4 is disposed above the contact 2 of the reed switch 1. 2 is reduced, and the off region is expanded according to the length of the magnetic shielding plate 4 as compared with the case where the above-described magnetic shielding plate is not provided. For example, the permanent magnet 3 moves in parallel with the x-axis direction and the y-axis distance is equal to or less than a predetermined value at the boundary position of the off region expanded by the magnetic shielding plate 4 (solid line in FIG. 2B). When it reaches, the contact point 2 of the reed switch 1 can obtain a sufficient magnetic pole direction and magnetic field strength of the permanent magnet 3, and the reed pieces of the reed switch 1 are magnetized to different polarities, and the action of magnetic attraction force. As a result, the contact 2 is turned on. Next, when the permanent magnet 3 moves back in the direction of the origin, the lead piece generated by the permanent magnet 3 at the boundary of the off-area enlarged by the magnetic shielding plate 4 (dotted line in FIG. 2B). The action of the magnetic attractive force is reduced, and the contact 2 is turned off by the mechanical elastic force of the lead piece.

  Thus, by providing the magnetic shielding plate 4, it is possible to enlarge the off-region near the contact 2 and extend the off-distance for obtaining the moving distance of the detection target. Further, since the off region can be adjusted by the length of the magnetic shielding plate 4 to be provided, a desired off region and on region can be easily obtained.

  FIG. 3 shows an example of actually measured values in the on / off region when the magnetic shielding plate 4 is provided and when it is not provided. As shown in FIG. 3B, the off region near the contact 2 when the magnetic shielding plate 4 is provided is the off region near the contact 2 when the magnetic shielding plate 4 is not provided as shown in FIG. It has been expanded.

  As described above, in the first embodiment, the magnetic shielding plate 4 that covers the contact 2 of the reed switch 1 is provided, and the magnetic shielding plate 4 reduces the magnetic force generated at the contact 2 of the reed switch 1 so that the contact 2 can be expanded without disposing the permanent magnet 3 at a position away from the contact 2 of the reed switch 1, and the length of the magnetic shielding plate 4 can be increased. By adjusting, a desired off-distance can be obtained.

Embodiment 2. FIG.
The magnetic proximity switch according to the second embodiment further includes a case 7 that encloses the reed switch 1, and the magnetic shielding plate 4 is disposed on the outer surface of the case 7. This case 7 may be a case 7 as a single magnetic proximity switch, or may be used as a case of a magnetic proximity switch application product incorporating the reed switch 1 (hereinafter referred to as “reed switch application product 5”). Hereinafter, the reed switch application product 5 will be described in the description of the second embodiment.

  FIG. 4 is a configuration diagram of the magnetic proximity switch according to the second embodiment. In FIG. 4, a reed switch application product 5 includes a reed switch 1 therein. Lead wires 6 are soldered to both terminals of the reed switch 1, and the lead wires 6 are drawn out of the case 7. A magnetic shielding plate 4 is attached to the outside of the case 7 of the reed switch application product 5 at a position corresponding to the position of the contact 2 of the reed switch 1 included. The on / off region of the reed switch 1 and the operation of the contact 2 with respect to the permanent magnet 3 are the same as those of the first embodiment.

  As described above, in the second embodiment, even in the case of the configuration of the reed switch application product 5 in which the reed switch 1 is included in the case 7 in order to make it easy to attach the magnetic proximity switch to various applications, The magnetic shielding plate 4 can be attached after the reed switch application product 5 is manufactured. For this reason, similarly to the above-described first embodiment, it is possible to obtain a long off distance, and it is possible to obtain a desired on region and off region even in the configuration of the reed switch application product 5.

  In the description of the first and second embodiments, the case of the magnetic shielding member formed in a plate shape has been described. However, the present invention is not limited to this, and the cross-sectional shape as shown in FIG. A magnetic shielding member formed in a letter shape (FIG. 5A) or a cylindrical magnetic shielding member (FIG. 5B) may be used. The shape may be applicable to various application products.

  In the second embodiment, the configuration in which the magnetic shielding plate 4 is attached to the outside of the case 7 of the reed switch application product 5 has been described. However, the present invention is not limited to this, and the magnetic shielding is provided between the reed switch and the permanent magnet. Since it is sufficient if the plate 4 exists, the same effect can be obtained even if the magnetic shielding plate 4 is disposed inside the case 7 of the reed switch application product 5.

  Furthermore, in the second embodiment, the case where the permanent magnet 3 is installed outside the case 7 has been described. However, the present invention is not limited to this, and the permanent magnet 3 is provided inside the case 7. It is attached to the detection object or an object interlocked with the detection object, and may be moved inside the case 7 in conjunction with the detection object.

1 is a configuration diagram of a magnetic proximity switch according to a first embodiment. 5 is a diagram for explaining an on / off region according to the first embodiment. FIG. 6 is a diagram illustrating an example of actual measurement values of an on / off region according to Embodiment 1. FIG. 6 is a configuration diagram of a magnetic proximity switch according to Embodiment 2. FIG. It is a figure which shows the other shape of a magnetic shielding member.

Explanation of symbols

  1 reed switch, 2 contacts, 3 permanent magnets, 4 magnetic shielding plate, 5 reed switch application product, 6 lead wire, 7 case.

Claims (13)

In a magnetic proximity switch having a reed switch that turns a contact on and off according to the magnetic force that changes depending on the position of a detected magnet,
A magnetic proximity switch comprising a magnetic shielding member that covers at least a part of the contact of the reed switch.   The magnetic proximity switch according to claim 1, wherein the magnetic shielding member reduces a magnetic force generated at a contact of the reed switch, and expands an off region where the contact is turned off with respect to the detected magnet.   The magnetic proximity switch according to claim 2, wherein the magnetic shielding member enlarges an off region near the contact in the off region.   The magnetic proximity switch according to claim 3, wherein the magnetic shielding member expands an off region near the contact in an axial direction of the reed switch.   The magnetic proximity switch according to any one of claims 1 to 4, wherein the reed switch is disposed so that an axial direction thereof is orthogonal to a magnetic pole direction of the detected magnet.   The magnetic proximity switch according to claim 1, wherein the magnetic shielding member is formed in a plate shape.   The magnetic proximity switch according to claim 1, wherein the magnetic shielding member is formed in a cylindrical shape.   The magnetic proximity switch according to claim 1, wherein the magnetic shielding member has a U-shaped cross section. A case containing the reed switch;
The magnetic proximity switch according to claim 1, wherein the magnetic shielding member is disposed on an outer surface of the case. A case containing the reed switch;
The magnetic proximity switch according to claim 1, wherein the magnetic shielding member is disposed inside the case. A detected magnet;
A case that includes the magnet to be detected, the magnetic shielding member, and the reed switch;
The magnetic proximity switch according to claim 1, wherein the magnetic shielding member is disposed between a contact of the reed switch and the detected magnet.   The magnetic proximity switch according to claim 11, wherein the detected magnet is attached to a detection object or an object interlocked with the detection object, and moves in the case in association with the detection object. .   The magnetic proximity switch according to claim 11, wherein the detected magnet is a permanent magnet.

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