JP2007328993A - Proximity switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proximity switch capable of detecting movement of a detected body by a simple structure even when detection with high precision is required as the movement range of the detected body is small. <P>SOLUTION: One end of a detecting rod 5 is made to protrude outside from the case main body 11 as a knob 51, the detecting rod 5 is moved by making the detected body 8 contact the knob 51, and a magnet 3 moves like a pendulum around the rotation axis 6, and by making the tip part of the magnet 3 thin and oppositely arranging it at a contact part 41 of a reed switch 2, even when the movement range of the detected body 8 is small, the contact part 41 of the reed switch 2 is opened and closed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a proximity switch using a magnet and a reed switch.

  In general, a proximity switch using a reed switch is used as a sensor for detecting opening / closing of a door, a lid, or the like (for example, Patent Document 1), or as a flow sensor for gas. That is, a magnet is attached to an object to be detected or an object linked thereto, and a reed switch is operated by the magnetic force of the magnet to detect the position or flow rate of the object to be detected.

  Conventionally, this type of proximity switch requires a certain range of movement as a detection condition as a detection condition, and at this time, a design that takes into account variations in magnet magnetic force and reed switch sensitivity is required. In general, a proximity switch that detects a combination of a magnet and a reed switch requires a moving range of several mm or more of an object to be detected as a detection condition.

Japanese Patent Laid-Open No. 10-12109

  In such a proximity switch, if the movement range of the detected object is smaller than the range that can be detected only by the combination of the magnet and the reed switch, a complicated operation expansion mechanism is required, Problems such as the need for sensitivity selection arise.

  To solve this problem, the problem to be solved by the present invention is to detect the movement of the detected object with a simple structure even when the detected object has a small moving range and requires highly accurate detection. It is to provide a proximity switch.

  In the proximity switch of the present invention, in the two-point operation method of the reed switch, paying attention to the fact that the HOLD (holding) region is narrow near the center of the contact, the tip of the magnet magnetized in the longitudinal direction is connected to the contact part of the reed switch. By making the tip of the magnet narrower and making the tip of the magnet thinner, it is possible to easily detect with a reed switch even if the movement range of the detected object is small.

  That is, the proximity switch of the present invention has a detection rod whose one end protrudes in a knob shape from the case and moves by contact with the detection target, and a rotating shaft that contacts the other end of the detection rod and moves according to the movement of the detection rod. A magnet that rotates around is provided, and the tip of the magnet is rotated in the vicinity of a contact point of a reed switch so that the movement of the detected object is detected by opening and closing the contact point.

  The area of the tip portion that has become one of the magnetic pole end faces of the magnet may be smaller than the area of the end portion on the rotating shaft side that has become the other magnetic pole end face of the magnet.

  The size of the tip portion that becomes one of the magnetic pole end surfaces of the magnet may be equal to or less than the size of the overlapping portions of the contacts that contact each other.

  According to the present invention, even when the movement range of the detected object is about 1 mm, highly accurate detection can be performed without using a complicated operation enlarging mechanism.

  In the present invention, since the HOLD (retention) region in the vicinity of the contact center is narrow, highly accurate detection is possible even if the sensitivity of the reed switch used is wide.

  In the present invention, it is possible to select the normal open operation and the normal close operation by selecting whether the initial magnet position is set at the contact center of the reed switch or before the contact center.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is an external view of a proximity switch according to an embodiment of the present invention, in which 1 is a case lid, 4 is a lead terminal, 51 is a knob, and 8 is an object to be detected. Further, the left-pointing arrow indicates the moving direction of the detected object 8.

  FIG. 1 is a partial cross-sectional view showing the internal structure with the case lid removed from FIG. 3, and the case body 11 and the container of the reed switch 2 are shown in cross section. FIG. 1 is a diagram showing the inside of the proximity switch before the detection object is detected.

  On the other hand, FIG. 2 is a partial cross-sectional view showing the inside of the proximity switch when an object to be detected is detected.

  As shown in FIG. 1, the detection target 8 is brought into contact with and moved by a knob 51 that protrudes outward from the case body 11. At the left end of the detection rod 5 provided with the knob 51 at the right end, a magnet 3 that rotates around the rotating shaft 6 (moves like a pendulum) is provided. The magnet 3 has a shape that becomes thinner as it approaches the tip, and is magnetized in the longitudinal direction, and the tip becomes one magnetic pole end face and faces the contact portion 41 of the reed switch 2. Thus, the area of the tip of the magnet 3 is smaller than the area of the end that is the other magnetic pole end face on the rotating shaft 6 side, and the magnetic flux emitted from the tip of the reed switch 2 The contact portions 41 are magnetized to the same polarity and opened by their repulsive force.

  As shown in FIG. 2, when the detection rod 5 having the knob 51 in contact with the detected object 8 moves, the magnet 3 in contact with the left end of the detection rod 5 rotates around the rotation shaft 6, and the tip of the magnet 3 By moving away from the contact part 41 of the reed switch 2, the contact parts 41 are magnetized in different polarities and attracted and contacted. At this time, the magnet 3 is pressed against the left end of the detection rod 5 from the opposite side by the spring 7, and the magnet 3 can perform a stable operation according to the movement of the detection rod 5.

  By the way, by disposing the tip portion of the magnet 3 in advance from the contact portion 41 of the reed switch 2, the contact portion 41 is kept in contact, and the tip portion of the magnet 3 is brought into contact with the contact portion of the reed switch 2 by the movement of the knob 51. If it comes to 41, it is also possible to open the contact part 41 by the movement of the knob 51.

  In order to describe the opening / closing operation of the reed switch in the above embodiment in detail, the operation of the two-point operation method when a bar magnet is arranged perpendicular to the reed switch will be described. FIG. 4 is an explanatory view showing the relationship between the position of the magnet arranged perpendicular to the longitudinal direction of the reed switch and the operation of the reed switch. FIG. 4 (a) is the first magnet position, and FIG. 4 (b). Is a second magnet position, and FIG. 4C is a diagram showing an operation region.

  As shown in FIG. 4A, when the magnet 3 is arranged perpendicular to the reed switch 2 and the magnetic pole end surface of the magnet 3 is near the center of the reed switch 2 (near the contact portion), the two reed contact points of the reed switch Are magnetized to the same polarity, and an OFF operation is performed by the repulsive force. This state corresponds to the OFF operation region slightly above the intersection (origin) of the x axis and the y axis in the operation region diagram of FIG.

  Next, as shown in FIG. 4B, when the end surface of the magnet 3 reaches the end in the longitudinal direction (axial direction) of the reed switch 2 while keeping the magnet 3 perpendicular to the reed switch 2, Is turned on by the attractive force. This state corresponds to the ON operation region slightly to the right of the intersection (origin) of the x axis and the y axis in the operation region diagram of FIG. A white area between the OFF operation area and the ON operation area is a HOLD (holding) area. In general, the operation of a reed switch using a magnet arranged perpendicular to the longitudinal direction (axial direction) of the reed switch is as described above.

  As can be seen from the operation region of FIG. 4C, in the shape of the magnet 3 having a thin tip as shown in FIGS. 1 and 2, the tip (N magnetic pole end face) facing the reed switch 2 is formed. The area is smaller than the area of the end portion (S magnetic pole surface) on the rotating shaft 6 side, and a thin magnetic flux is generated from the N magnetic pole end surface, so that the tip portion (N magnetic pole end surface) is slightly rotated. The contact part 41 opens and closes. As a result, detection is possible even when the movement of the detection rod 5 is minute. At the same time, despite the simple structure as shown in FIG. 1 and FIG. 2, the pivoting distance of the tip (N magnetic pole end face) is larger than the moving distance of the detection rod 5 due to the lever principle. This is also useful for detecting minute movements of about 1 mm.

  Further, it is more effective if the dimension of the tip part (N magnetic pole end face) of the magnet 3 is set to be equal to or smaller than the overlap dimension of the contact part 41 of the reed switch 2 (the dimension of the part where the two contact parts 41 contact). In addition, a minute movement of the detection rod 5 can be detected.

The fragmentary sectional view which shows the internal structure of the proximity switch in one embodiment of this invention. The fragmentary sectional view which shows the inside of a proximity switch when the to-be-detected object in one embodiment of this invention is detected. The external view of the proximity switch in one embodiment of this invention. FIGS. 4A and 4B are explanatory diagrams showing the relationship between the position of a magnet arranged perpendicular to the longitudinal direction of the reed switch and the operation of the reed switch. FIG. 4A is a first magnet position, and FIG. Magnet position, FIG. 4C is a diagram showing an operation region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case cover 2 Reed switch 3 Magnet 4 Lead terminal 5 Detection rod 6 Rotating shaft 7 Spring 8 Detected object 11 Case main body 41 Contact part 51 Knob

Claims (3)

  A detection rod having one end protruding from the case in the form of a knob and moving by contact with the detection object, and a magnet that contacts the other end of the detection rod and rotates around the rotation axis according to the movement of the detection rod are provided. A proximity switch that detects the movement of the detected object by opening and closing the contact by rotating the tip of the magnet in the vicinity of the contact of the reed switch.   2. The area of the tip portion which becomes one magnetic pole end face of the magnet is smaller than the area of the end portion on the rotating shaft side which becomes the other magnetic pole end face of the magnet. Proximity switch.   3. The proximity switch according to claim 1, wherein a size of the tip portion which is one magnetic pole end surface of the magnet is equal to or less than a size of an overlapping portion of the contacts which are in contact with each other.

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