Compact magnetic induction switch

An extremely compact low cost magnetic induction switch which may be activated by an extremely small operation force (approximately 1 g) has a movable member (2) and a coil spring (3) arranged inside a switch case (1), the spring coil (3) supporting the movable member (2), and the movable member protruding from an opening (1D) of an upper surface portion of the switch case (1). A Hall IC (4) is arranged in a switch case (1). When the upper portion is pushed, a magnet (6) fixed to the movable member (2) moves downward so that an output signal of the Hall IC (4) is changed from OFF to ON.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a non-contact type compact magnetic induction switch capable of being switched ON and OFF by a slight operating force.

2. Description of the Related Art

As for a conventional compact switch, there are available a mechanical contact type switch and a proximity switch utilizing an oscillator. However, the contact type switch has its limit in making the operating force small, and further miniaturization thereof is difficult. While, the proximity switch is complicated in its structure, and has its limit in reducing the cost.

Further, a hole effect type position sensor which combines a permanent magnet and a hole element is used as position detection means for various types of equipment. This position sensor attaches the permanent magnet to a detected body whose position is desired to be detected so that magnetic field generating portions are constituted and, at the same time, a magnetic detection portion comprising the hole element is constituted so as to be relatively displaced against these magnetic field generating portions. When the magnetic field generating portions come close to the magnetic field detection portion, the hole element of the magnetic field detection portion detects the magnetic field from the magnetic generating portions by means of the hole effect and outputs an electrical signal, thereby detecting the position of the detected body. The hole effect type position sensor which constitutes such a hole element as the magnetic field detection portion does not have a mechanical contact such as a micro switch and the like, and has the advantages of being highly reliable in operating in non-contact on the detected body and, hence, is adopted in a wide range of applications.

Since the object of the sensor is to detect the position, though a measure for improving position detection accuracy is taken, using the sensor as a compact switch is not taken into consideration. Therefore, improving the function of the sensor as the compact switch is not taken into account.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an ultra compact magnetic induction switch, whose operating force is made as small as possible and whose size is made as compact as possible.

Additionally, the above described object is realized by the compact magnetic induction switch comprising: a switch case; a movable member provided on an opening of the switch case and being reciprocally movable; an elastic body which is installed inside the switch case and urges an end portion of the movable member so as to be protruded outside of the switch case; a magnet fixed to the movable member; and a hole IC for detecting change of magnetic field caused by movement of the movable member with its operating point, wherein if the magnet field applied to the operating point of the hole IC becomes above or below a threshold by movement of the movable member, output signal of the hole IC switches on/off.

In the compact magnetic induction switch of the present invention, the positioning portion which positions the hole IC at a predetermined position may be provided inside the switch case.

Alternatively, a guide portion which guides the movable member may be provided inside the switch case. A lid member which is fitted into the bottom of the switch case may be provided and an opening which derives the lead wire of the hole IC or an opening which injects a filling agent may be provided on the lid member.

DESCRIPTION OF THE PREFERRED EMBODIMENT

One embodiment of a compact magnetic induction switch of the present invention is shown inFIGS. 1 to 8. In the drawings, reference numeral1denotes a switch case, reference numeral2a movable member, reference numeral3a spring coil, reference numeral4a hole IC, reference numeral5an output lead wire thereof and reference numeral6a permanent magnet, for example, such as a rare earth magnet.

The switch case1, as shown inFIGS. 2 to 8, has a chamber1a, in the interior of which are stored the movable member2, the spring3and the Hall IC4. In the chamber1a, there are a positioning portion1band a guide portion1cintegrally provided with the switch case, and the positioning portion1bcomprises three pieces of positioning portions1b1to1b3. The guide portion1chas rail-shaped guide members1c,1c2which protrude inward longitudinally inside the interior. Further, on the upper surface portion of the switch case1is provided an opening1D, and on the bottom thereof is built-in a base1E, In the base1E is provided a storing concave portion1F of the spring3and a deriving hole1G of the output lead wire5.

The movable member2, as shown inFIGS. 2,3, has a concave portion2ato fix the magnet6and an upper storing chamber2bof the spring3. The magnet6is fixed to the concave portion2aby an adhesive agent and the like.

The movable member2, as shown inFIGS. 1 to 4, is stored inside the chamber1ainside the switch case1, and the upper portion of the spring3stored in the concave portion1F is inserted into the interior of the storing chamber2bso as to support the movable member2, and in this state, an upper end portion2cof the movable member2protrudes from an opening1D of the upper surface portion of the switch case1. A n upper portion of the movable member2contacts an upper area of chamber1aof switch case1to retain the movable member2in switch case1.

Further, in the left and right sides of the movable member2are formed protruding portions2D1to2D4, and these protruding portions are fitted to the guide members1c1,1c2of the guide portion1cwith a little clearance.

The Hall IC4is positioned by the positioning members1b1to1b3of the positioning portion1bin the chamber1ainside the switch case1, and is mounted on the base1E. The output lead wire5from the Hall IC4is derived to the outside via the deriving hole1G.

Due to the above-described constitution, the movable member2in a state of not pressing the upper end portion2cis supported by a repelling force of the spring3, and the upper end portion2cprotrudes from the opening1D. At this time, a magnetic neutral point6aof the magnet6is slightly above an operating point4aof the hole IC4. An output signal obtained in this state from the output lead wire5of the hole IC4is in an OFF state.

Next, when the upper end portion2cis pressed, the movable member2moves downward, and the neutral point6aof the magnet6passes through the operating point4aof the Hall IC4, and at tat point in time, the output signal is turned ON. By pressing or non-pressing the upper end portion2cin this way, the output signal of the Hall IC4can be turned ON or OFF (or OFF or ON).

Referring toFIG. 9, the switch of the invention can be activated by an operating force of only one (1) gram. The movable member2is in the upper position where the upper end portion2cis not pushed. In this configuration, the operating point4aof the hole IC4is just under the N-pole side isomagnetic field plane +V20of 20 Gauss, while the magnetic neutral point6aof the magnet6is located above the plane +V20. Isomagnetic field plane V0in which the magnetic field is zero (0) is orthogonal against the surface of the magnet6at the neutral point6a

The upper end portion2cis then pushed, and the magnet6moves downward in the direction shown by an arrow A. When the S-pole isomagnetic field plane −V20of 20 Gauss passes through the operating point4a, the hole IC4outputs an ON signal because its threshold from OFF state to ON state is set to magnetic field corresponding to the plane −V20. The magnetic field is higher than 20 Gauss while the upper end portion2cis pushed, so that the ON signal is sustained.

When the upper end portion2cgoes back to the original position, the magnetic neutral point6amoves upward. At the moment the S-pole isomagnetic field plane −V17of 17 Gauss passes through the operating point4a, the ON state of the hole IC4changes to OFF state because its threshold from ON state to OFF state is set to the magnetic field corresponding to the plane −V17. Setting two kinds of thresholds like −V20and −V17prohibits self-oscillation of the hole IC.

As described above, in order to activate the switch of the invention, it is only necessary to apply a magnetic field corresponding to the threshold of the hole IC4to the operating point4a, which needs little operating force, only one (1) g, because the hole IC is not attracted by the magnet. In contrast, in the case of a conventional switch employing the combination of a reed switch and a magnet, the reed switch is attracted by the magnet so that it can not be switched by such a small force. Furthermore, in the switch of the invention, the distance necessary for switching on is only several μm, but in the conventional switch employing the combination of the reed switch and the magnet, such a distance is several mm.

FIGS. 10 to 12show one example of a mounting bracket to mount the switch of the invention on a desired member as occasion demands. In the drawings, reference numeral10denotes a mounting bracket, reference numeral10a, an engaging portion, reference numeral10b, a case mounting opening portion, and reference numeral10c, a mounting portion.

As shown inFIGS. 2 and 3, the engaging portion10aof the mounting bracket10is engaged with an engaging hole1H of the switch case1, and the opening portion10bis fitted to the opening1D of the switch case1. Mounting holes10c1,10c2of the mounting portion10care used for screw clamping to the desired member.

FIGS. 13 to 15show a lid member11to be fitted to the bottom of the switch case1as occasion demands and to seal the bottom of the switch. In the drawings, reference numeral11adenotes a take out hole of the output lead wire5and reference numeral11bdenotes a hole to inject a filling agent such as silicon resin and the like. The lid member11is fitted to the bottom of the switch case1, and after taking out the output lead wire5from the take out hole11a, silicon resin is injected into the take out hole from the hole11bwhich seals the hole.

As described above, according to the invention, an ultra compact magnetic induction switch can be constituted operable with a small operating force of about one gram level. Further, since members other than the hole IC, the magnet, and the spring can be formed by synthetic resin, a sharp reduction in costs can be achieved. Further, as an output of the hole IC, a switch output of OFF-ON or ON-OFF can be easily obtained.