JPH0311775Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical field to which the invention pertains] The present invention relates to a switch for detecting minute displacements, which is composed of a reed switch, a permanent magnet, and an elastic body. [Prior Art] In a proximity switch using a reed switch, there is a difference between the magnetic flux when the contact closes and the magnetic flux when the contact opens in the reed switch itself, that is, there is an operating gap. In other words, when a permanent magnet is moved near or far from a reed switch to open or close the contacts, in commonly used reed switches, the difference between the position of the permanent magnet when it closes and the position when it opens (hereinafter referred to as the operating clearance dimension) ) is about 1 to 5 mm, making it impossible to create a proximity switch with an operating clearance of 1 mm or less. [Object of the invention] An object of the invention is to provide a displacement switch with a small operating clearance, that is, capable of detecting minute displacements of substantially 1 mm or less. [Structure of the invention] The invention consists of two cylindrical permanent magnets magnetized in the axial direction on the outer periphery of the reed switch, spaced apart from each other by a predetermined distance around the reed contact, with the magnetic poles in the same direction. One of the magnets is fixed, and the other magnet is held movably in a direction away from or toward the fixed magnet via an elastic body. [Example] The present invention will be explained with reference to the drawings. Fig. 1 is a diagram showing the basic configuration of the present invention. In the figure, 1 is the lead contact 2 in the center of the glass tube.
It is a reed switch with Reference numerals 3 and 4 indicate cylindrical permanent magnets magnetized in the axial direction, which are inserted into the outer periphery of the glass tube of the reed switch 1 at a required interval around the reed contact 2 so that the magnetization directions are in the same direction. ing. One magnet 3 is a fixed magnet fixed to the reed switch 1, and the other magnet 4
is movable in the direction approaching the fixed magnet 3 (provided that it is not displaced by magnetic attraction).
It is a moving magnet. The distance between the fixed magnet 3 and the movable magnet 4 is the minimum dimension at which the reed contact 2 changes from the closed state to the open state. When the movable magnet 4 moves by Δ in the direction toward the fixed magnet 3 due to an external force, the reed contact 2 changes from the open state to the closed state. This dimension Δ is the operating clearance dimension. With the configuration shown in FIG. 1, a small operating clearance can be achieved. For example, when using a reed switch with a glass tube outer diameter of 2.7 mmφ, a glass tube total length of approximately 17 mm, a reed diameter of 0.6 mmφ, and a total length of approximately 44 mm, a cylindrical magnet (outer diameter of 7.6 mm) is used.
mmφ, inner diameter 3.5mmφ) The operating clearance dimension Δ and the interval based on the length dimension L are as shown in Table 1 below. That is, the larger the length L of the cylindrical magnet, the smaller the operating clearance dimension Δ can be, and an operating clearance dimension of less than 1 mm can be obtained.

[Table] FIG. 2 shows a sectional view of an embodiment of the present invention. The same parts as in FIG. 1 are given the same reference numerals. Reference numeral 5 denotes a cylindrical case with a bottom, a through hole 51 for a lead wire is provided on the bottom surface, and three stepped portions 52, 53, 54 on the inner circumferential surface that expand stepwise toward the opening.
55 is formed, and a female thread 56 is further threaded on the inner periphery of the open end. 6 is a compression coil spring and magnet 3,
It has a greater elasticity than the magnetic attraction between the two. Reference numeral 7 denotes a piston-shaped operating rod, and the large diameter portion 71 is sized to fit into the inner peripheral surface of the stepped portion 54 of the case 5, and a recessed portion 72 with a stepped portion 73 is formed in the center of the end surface. The step 54 acts as a stop for the operating rod 7. Reference numeral 8 denotes an adjustment nut having a male thread 81 threaded on its outer circumferential surface to be screwed into the female thread 56 of the case 5, and a central hole through which the small diameter portion 74 of the operating rod 7 can pass is formed in the center. To assemble, first, the fixed magnet 3 is fitted onto the stepped portion 52 of the case 5. Then, a lead wire is connected to the lead of the reed switch 1 and extended in the same direction, and the lead switch 1 is inserted into the center hole of the magnet 3 while the lead wire is inserted into the through hole 51 of the case 5. This reed switch 1 is fixed with an adhesive 9 or the like so that the reed contact 2 is in a predetermined position relative to the magnet 3. The movable magnet 4 is fixed to the step 73 of the operating rod 7 such that the magnetic pole opposite to the step 52 of the magnet 3 faces the step 73 of the operating rod 7. The operating rod 7 is fitted into the case 5 with the coil spring 6 interposed between the stepped portion 53 of the case 5 and the end face of the large diameter portion 71. Further, the adjusting nut 8 is screwed onto the female thread 56 and brought into contact with the back surface of the large diameter portion 71 of the operating rod 7. Figure 2a shows the state before operation. Adjustment nut 8
Due to the elasticity of the coil spring 6, the movable magnet 4
(integrated with the operating rod 7) is brought close to the fixed magnet 3 to close the reed contact 2. At this time, the large diameter portion 71 of the operating rod 7 and the stepped portion 54 are brought into contact with each other. Next, the movable magnet 4 is slowly moved in a direction away from the fixed magnet 3 using the adjusting screw 8, and stopped at a position where the reed contact 2 is in an open state. In this state, a required spacing between the magnets 3 and 4 is ensured, and a distance equal to the operating clearance exists between the large diameter portion 71 of the operating rod 7 and the stepped portion 54. In Fig. 2b, displacement is applied to the end face of the small diameter portion 74 of the operating rod 7 in the direction shown by arrow F with a strength that overcomes the elasticity of the coil spring 6, resulting in a small operating clearance Δ.
This is the state after the operation in which the lead contact 2 is closed.
When the external force F is removed, the elasticity of the coil spring 6 is greater than the magnetic attraction between the magnets 3 and 4, so
The movable magnet 4 returns to the position shown in FIG. 2a, and the reed contacts 2 become open. In this way, the operating rod 7
By bringing a detected part that causes a displacement into contact with the reed switch 1, a minute displacement of the detected part can be detected by the closing signal of the reed switch 1. In the above embodiment, when the operating rod 7 is displaced by the operating clearance dimension, the operating rod 7 is locked at the stepped portion 54, but this locking position may have some play. That is, the operating rod 7 is 0.5 to 1
When the reed switch 1 is closed after being displaced by the operating clearance within the range of mm, the large diameter portion 71 of the operating rod 7
There may be a gap of about 0.2 to 0.3 mm between the step portion 54 and the step portion 54. Further, although the magnets 3 and 4 are shown to have approximately the same length, they may have different lengths. This displacement switch is ideal for the following applications: That is, panel-type push button switches have recently been used in washing machines, refrigerators, and the like. The surface of the push button is covered with a thin resin film to provide a moisture-proof function.In order to prevent the thin resin film from being damaged by repeated use, the displacement of the push button is minimized and the surface of the push button has a flat shape. It is required to do so. The displacement switch according to the present invention has sufficient moisture resistance by using a reed switch whose contact part is sealed in a glass tube, and operates with a very small displacement, so the surface of the push button can be made flat. . In addition, in order to improve the moisture resistance function, the coil spring 6 must also have a movable displacement of 1 mm.
In consideration of the following and corrosion, other materials such as plastic, silicone resin, and other polymeric elastic materials may be used instead of metal. [Effects of the Invention] As explained above, according to the present invention, it is possible to provide a displacement switch that has a small operating gap and is therefore optimal for detecting minute displacements.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, and FIGS. 2A and 2B are sectional views showing the state of an embodiment of the present invention before and after operation, respectively. 1... Reed switch, 3... Fixed permanent magnet,
4... Movable permanent magnet, 5... Case, 6... Compression coil spring, 7... Operating rod, 8... Adjusting nut,
9...Adhesive.

Claims (1)

[Scope of utility model registration request] Two cylindrical permanent magnets magnetized in the axial direction are placed around the outer periphery of the glass tube of the reed switch at a predetermined interval around the reed contact portion of the reed switch so that the magnetic poles have the same direction. one of the magnets is fixed, and the other magnet is held movable in a direction away from or toward the fixed magnet via an elastic body that provides a restoring force to the magnet. Switch.