JPH11136115A - Micro switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have long life without oxidation or abrasion of a contact, to prevent contact failure from occurring and to compeletely prevent a chattering phenomenon that takes place at the time of contact continuity by converting an output of a pressure sensor into a voltage signal and amplifying it and outputting an on signal when the electric signal exceeds prescribed reference voltage. SOLUTION: Relating to a distortion gauge 3, pressure is applied at its central pressure receiving part when a push button 2 is pushed and the resistance value of an internal resistance line is changed. When the resistance value of the resistance line of the gauge 3 changes, a voltage detecting part 6 detects it as voltage change and inputs it to an OP amplifier, and the OP amplifier amplifies voltage of the small detection voltage and adds it to a + input terminal. Because the OP amplifier has its - input terminal where reference voltage is applied, an on signal of a logical value 1 is outputted to an output when + input terminal voltage exceeds the reference voltage. A FET 5 is driven by the on signal and is turned from an off state to an on state, and an output terminal 11 and a ground terminal 12 are electrically conducted through a resistor for protection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microswitch, and more particularly, to a microswitch required for high reliability used in equipment mounted on a satellite.

[0002]

2. Description of the Related Art A micro switch of this type obtains an electrical open or close signal from a connection portion of the switch by pressing a push button. Particularly, it is used as a part of mechatronics with a very small size, and is used, for example, when it is attached to a hinge part such as a door to electrically detect opening and closing of the door.

FIG. 3 shows an example of a conventional microswitch described in Japanese Utility Model Laid-Open Publication No. 63-9715. FIG. 3 is a sectional view showing the structure of the conventional example.

In FIG. 3, a push button 17, a movable piece 15 movable by pressing the head of the push button 17, movable contacts 152 and 153 at the tip of the movable piece 15, The upper fixed contact 141 and the lower fixed contact 131 that come into contact with the movable contacts 152 and 153, the movable spring 16 that gives elasticity to the movable piece 15, and the terminals 12, 1
3 and 14 are housed and constitute the whole.

In this microswitch, the movable contact 152 and the upper fixed contact 141 are always in contact with each other, but when the head of the push button 15 is pressed, the movable piece 15 is pushed downward, and the movable contact 153 is placed on the lower surface. The electrical connection is switched by contacting the fixed contact 131 side.

In particular, in this microswitch, one contact portion of each connection point is formed at an acute angle to improve the contact stability of the contact.

[0007]

As described above, in the conventional microswitch, the contact portion for obtaining an electrical opening / closing signal is a mechanical contact. In particular, such a microswitch has the following problems. is there. First, if oxidation and abrasion of the connection portion progress with the passage of time, an increase in electrical contact resistance or poor contact occurs. Next, when the contact surface wears and becomes rough, chattering occurs in which the contact instantaneously repeats connection and disconnection before complete contact, which causes a problem that a subsequent circuit malfunctions due to generation of noise. In addition, since it is a mechanical contact, it may malfunction due to shock or vibration. Further, there is a problem that the use location is restricted because the pressing force of the push button is strong.

In particular, since the microswitch is used as a part of mechatronics, the above-mentioned phenomenon that the contact reliability is reduced is a particularly serious problem.

[0009]

A microswitch according to the present invention comprises a pressure sensor for outputting an electric signal proportional to the pressure applied through a push button, and an amplifier for converting and amplifying the output of the pressure sensor into a voltage signal. A voltage detection unit that outputs an ON signal (a signal that changes from a logical value of 0 to a logical value of 1) when the signal exceeds a predetermined reference voltage; and a semiconductor switch element that operates on the output signal of the voltage detection unit. ing.

In particular, the pressure sensor may use a strain gauge.

Further, the switching element may be an FET.

Further, the switch element may use an SCR.

The reference voltage may be variable.

A small outer box made of molded resin, the push button having a head protruding from the upper surface of the outer box and mounted inside thereof, and fixed at a position in contact with a tip end of the push button in the pressing direction. A structure in which the pressure sensor, the plurality of components constituting the voltage detection unit, and the semiconductor switch element are mounted on a small substrate, and the substrate is mounted at a position below the pressure sensor.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing the structure of the embodiment of the present invention. FIG. 2 is a circuit diagram showing a circuit configuration of the microswitch of FIG.

In FIG. 1, this microswitch comprises a small outer box 1 made of molded resin, and a push button 2 having a head protruding from the upper surface of the outer box 1 and mounted inside thereof.
And a strain cage 3 of the pressure sensor fixed so that the pressure receiving portion is located at the disk-shaped tip in the pushing direction of the push button 2.
And a substrate 4 on which components constituting the voltage detecting unit 6 and a switching element FET 5 are mounted below the strain cage 3.
And a spring 5 for applying a repulsive force to push the push button 2 back,
It comprises an output end 11, a ground terminal 12, and a power supply terminal 13 connected to the pattern surface of the substrate 4.

The size of the outer box 1 is about 12 × 10 × 7 m.
m. Each component to be mounted on the substrate 4 is an MCM.
(Multiple Chip Module).

The strain gauge 3 has a very fine resistance wire (diameter: 20 to 30 μm) made of platinum having a large specific resistance, for example, constantan, running meandering on the surface of the gauge base and fixed with a plastic adhesive or the like. Is made by meandering the constantan foil to the meandering surface of the gauge base by etching, etc., and is proportional to the amount of strain generated by externally applied stress on the central pressure receiving part of the cage surface. The resistance value of the resistance wire (or foil) changes.

Referring to FIG. 2, the circuit configuration of the present microswitch will be described. When the push button 2 is depressed, pressure is applied to the central pressure receiving portion of the strain cage 3 so that the resistance value of the internal resistance wire changes. Resistor 61 of voltage detector 6
Since the bridge circuit is configured to include the resistance wire of the strain gauge 3 as one of the constituent elements, when the resistance value of the resistance wire of the strain cage 3 changes, this is detected as a change in voltage, and the OP amplifier 68 To enter. The OP amplifier 68 amplifies this minute detection voltage and applies it to the + input terminal of the OP amplifier 69.

The OP amplifier 69 has a reference voltage 6
5 is added, so that if the + input terminal voltage is equal to or lower than the reference voltage, an OFF signal having a logical value of 0 is output to the output, but if the voltage exceeds the reference voltage, an ON signal having a logical value of 1 is output to the output. Is output. The FET 5 is driven by the ON signal and changes from the OFF state to the ON state, and the output terminal 11 and the ground terminal 12 are electrically connected via the protection resistor 51.

When the push button 2 is not pressed, no pressure is applied to the strain gauge 3, so that the detection voltage of the bridge circuit is not generated, and the FET 5 is turned off and the output terminal 11 and the ground terminal 12 are disconnected. It is.

The resistors 66 and 67 divide the output voltage when the OP amplifier 69 outputs an ON signal and add the divided voltage to a reference voltage to further determine the ON state. This provides hysteresis to prevent such phenomena.

Furthermore, the reference voltage 65 is obtained by dividing the internal power supplied from the power supply terminal 13, but this voltage can be varied so that the operation due to the variation in the characteristics of the strain gauge 3 and the variation in the points are made uniform. You may do it.

As can be seen from the structure and circuit configuration described above, the operation of the present microswitch is as follows. That is, since the FET 5 of the switch element is normally off, the connection between the output terminal 11 and the ground terminal 12 is in a non-conductive state. Next, when the push button 2 is pressed, the tip of the push button 2 pushes the pressure receiving portion 6 at the center of the strain gauge 3 to change the resistance value of the resistance wire of the strain gauge 3. The voltage detector 6 detects the change in the resistance value as a voltage change, amplifies the voltage, and outputs an ON signal to the FET 5. FE
T5 is turned on, and the output terminal 11 and the ground terminal 12 are electrically connected.

The above-described microswitch is a non-latch type in which the output contact is conductive only while the push button is pressed.
By changing to R, the continuity state may be maintained only by pressing the push button once, and the latch type may be changed.

[0026]

As described above, since the microswitch of the present invention is digitized using FETs for the pressure sensor and the switching element, the microswitch does not oxidize or wear as compared with the one using mechanical contacts. Long life, no poor contact, etc., and the electrical hysteresis characteristic gives complete prevention of the chattering phenomenon that occurs when the contacts are turned on, and malfunctions due to environmental shock or vibration Further, since the pressure sensor has high sensitivity, the pressing force of the push button can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing the circuit of FIG. 1;

FIG. 3 is a sectional view showing the structure of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 outer box 2 push button 3 strain gauge 4 FET 5 spring 6 voltage detector 11 output terminal 12 ground terminal 13 power supply terminal 61-67 resistor 68, 69 OP amplifier 51 resistor

Claims (6)

[Claims] 1. A pressure sensor for outputting an electric signal proportional to a pressure applied via a push button, and an output of the pressure sensor is converted to a voltage signal and amplified when the electric signal exceeds a predetermined reference voltage. A microswitch, comprising: a voltage detection unit that outputs an ON signal (a signal that changes from a logical value 0 to a logical value 1); and a semiconductor switch element that operates with an output signal of the voltage detection unit. 2. The microswitch according to claim 1, wherein the pressure sensor uses a strain gauge. 3. The microswitch according to claim 1, wherein the switch element uses an FET. 4. The microswitch according to claim 1, wherein said switch element uses an SCR. 5. The microswitch according to claim 1, wherein said reference voltage is variable. 6. A small outer box made of a molded resin, a head protruding from an upper surface of the outer box, the push button mounted inside the outer box, and a position in contact with a front end of the push button in a pressing direction. A pressure sensor fixed to the pressure sensor, a plurality of components constituting the voltage detection unit, and the semiconductor switch element are mounted on a small-sized board, and the board is mounted below the pressure sensor. Item 1, 2, 3, 4 or 5. The microswitch according to item 5.