JPH0419688Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of a piezoelectric switch that uses an electromotive force generated by applying strain to a piezoelectric plate as a switching signal.

BACKGROUND ART Electronic volumes and electronic tuning devices used in radio receivers, television receivers, and the like are configured so that the voltage begins to change with the first input signal and stops changing with the second signal. The present invention seeks to provide a piezoelectric switch suitable for signal input to such devices.

[Conventional technology and its problems]

FIG. 7 is a sectional view showing an example of a conventional piezoelectric switch. In this piezoelectric switch, a dome-shaped spring 9 is inverted by pushing down a plunger 10, and the piezoelectric plate 6 is distorted by the impact of the inverted dome-shaped spring 9. Between the conductive plate 7 fixed to the top surface of the piezoelectric plate 6 and the dome-shaped spring 9,
As shown in FIG. 8, a substantially arc-shaped spacer 8 is interposed, and a large gap is formed for smooth air circulation when the spring 9 is reversed and returned to its original shape. There is. However, the output waveform of a piezoelectric switch with such a configuration is as shown in FIG.
When the switch is turned on by pressing down, an electrical pulse signal is generated, but when the force applied to the plunger is released, that is, the switch is turned on.
When it is OFF, almost no pulse signal is generated. Therefore, in order to apply the piezoelectric switch to an electronic volume or the like and output two pulse signals, there was a problem in that the switch had to be pressed twice.

The present invention enables a piezoelectric switch to be applied to electronic volumes, etc. by stably generating a switching signal of sufficient magnitude twice, once when the plunger is pressed and once when it is released. .

[Means for Solving the Problems and Their Effects] FIG. 4 shows the load curve of the dome-shaped spring, and the horizontal axis is the stroke of the plunger. When you press the plunger from state A,
The dome-shaped spring reverses at position B, where the load is maximum, and after striking the piezoelectric plate at position C, the load increases again and reaches position D. On the other hand, when the released plunger returns to its original state due to the elasticity of the dome-shaped spring, it returns from D to the initial state of A via E and F.

In the present invention, instead of the conventional arc-shaped spacer 8,
It is characterized by a configuration using a substantially ring-shaped spacer having an extremely small notch for air circulation. Because of this configuration, during the process from E to F in Figure 4 in which the pressed plunger returns to its original position, a negative pressure is momentarily created between the dome-shaped spring and the piezoelectric plate, and the piezoelectric plate A force acts on it that distorts it into an upwardly convex shape. Immediately after this, the movement of the piezoelectric plate returning to its original shape is a distortion in the same direction as when the piezoelectric plate is struck by a dome-shaped spring and produces a pulse signal, so when pressing and returning the plunger, i.e. As shown in Figure 3A, a pulse signal of the same polarity is generated twice: when the switch is turned on and when the switch is turned off. FIG. 3B shows a rectangular voltage waveform obtained by passing only the positive polarity of the pulse signal A through an amplification waveform shaping circuit.

〔Example〕

In FIGS. 1 and 2, numeral 1 denotes a housing whose upper and lower surfaces are open and terminals 2 are implanted at the four corners. The housing 1 includes a partition plate 1b having a through hole 1a and a vertical groove 1c that passes through the partition plate 1b provided on the inner side, and has hook-shaped projections 1 on the two sides.
d is provided. 3 is a nearly rectangular flexible printed circuit board with printed wiring 3a on the bottom surface, and after inserting the terminals 2 into the through holes 3b at the four corners,
It is attached and fixed to the four terminals 2 by soldering. A protrusion 3c having a free end covered with a printed wiring 3a is formed in the center of the printed circuit board 3 by punching out its periphery. A chip-shaped resistor 4 and a capacitor 5 are soldered. 6 is a disk-shaped piezoelectric plate polarized in the thickness direction and provided with electrodes (not shown) on both sides;
b without being fixed, and its upper surface is adhered to a conductive plate 7 made of brass or the like. The conductive plate 7 has a disk portion 7a to which the piezoelectric plate 6 is fixed, and a lead portion 7b that is integrally drawn out from the disk portion 7a. It is fixed to the printed circuit board 3 together with the piezoelectric plate 6 by inserting it into the through hole 3d and soldering. A flexible protrusion 3c provided on the printed circuit board 3 is bent upward and soldered to the lower electrode of the piezoelectric plate 6. On the conductive plate 7, a substantially ring-shaped spacer 18 made of metal or rubber material having a notch 18a made of a narrow slit, and a dome-shaped metal spring 9 are placed in sequence. A plunger 10 is further placed on top of the spring 9. plunger 10
It has a flange 10a and a hemispherical protrusion 10b at its lower part, and is movable up and down. A cover 11 provided with a hole 11a for inserting the plunger 10 is fixed to the housing 1 by engaging two locking pieces 10b formed on the side surface with a protrusion 1d.

In the piezoelectric switch configured in this way, when the plunger 10 is pushed down, the dome-shaped spring 9 pressed by the protrusion 10b suddenly reverses and strikes the conductive plate 7, causing the piezoelectric plate 6 to form a downwardly convex shape. Since distortion is applied, an electromotive force is extracted to the terminal 2 through the lead portion 7b and the protruding piece 3c. Even when the force pushing down the plunger 10 is released and the plunger 10 returns to its original position due to the restoring force of the dome-shaped spring 9, the notch 18a is so small that the dome-shaped spring 9 and the conductive plate 7 There is a momentary negative pressure between the two, distorting the piezoelectric plate 6 into an upwardly convex shape, and when the piezoelectric plate 6 returns to its original shape due to this reaction,
An electromotive force of the same polarity as when the plunger 10 is pushed down is taken out to the terminal 2. In other words, two times: immediately after pushing down the plunger 10 and at the moment when it is released.
It generates voltages of the same polarity twice.

Using a spacer 18 with an outer diameter of 10 mm and a plate thickness of 0.08 mm,
When the plunger load was 200 grams, the relationship between the slit width of the notch 18a and the output voltage at switch-off was as shown in FIG. in this case,
0.1mm to generate large output when off
It can be seen that a slit width of approximately 0.5 mm is suitable. Also, when the width of the notch 18a at this time is converted into an angle from the center of the spacer 18, it is 1° to 7°.
It is sufficient that the width is within the range of . Notch 18
Even if the width of a is smaller than 1° or larger than 7°, a sufficient output voltage cannot be obtained when the switch is turned off.

Note that the notch 18a may be provided in the form of a groove as shown in FIGS. 6A and 6B instead of being formed as a slit.

[Effect of idea]

In this invention, by attaching a roughly ring-shaped spacer with a minute notch under the dome-shaped spring, we ensure that the piezoelectric plate is distorted even when the plunger returns, so that one Two pulse signals can be efficiently extracted by pressing the button. Moreover, when a pulse signal is generated, a click sensation caused by the sudden movement of the dome-shaped spring is transmitted to the fingertip through the plunger, making it easy to confirm the operation. Therefore, according to the present invention, it is possible to construct an electronic volume or an electronic tuning device with good operability by using a piezoelectric switch having excellent durability and stability.

In addition, the switch according to the present invention can be connected to an integrated circuit or the like by reversing the polarity, so that the switch outputs an output only when it is off, so it is suitable for use as a hold switch for telephones, etc.

[Brief explanation of drawings]

Figure 1 is a front cross-sectional view showing an embodiment of the piezoelectric switch of the present invention, Figure 2 is an exploded perspective view of the same, Figure 3A is an output waveform diagram of the switch, and Figure 3B is a diagram after waveform shaping. Output waveform diagram, Figure 4 is a load curve diagram of the dome-shaped spring, Figure 5 is a characteristic diagram showing the relationship between the output voltage of the switch and the slit width of the spacer, and Figure 6 is a diagram showing the relationship between the output voltage of the switch and the slit width of the spacer.
The figures show other embodiments of the spacer, in which A is a plan view and B is a sectional view taken along line A--A in A. 7th
9 to 9 show conventional examples. FIG. 7 is a front sectional view of a piezoelectric switch, FIG. 8 is a perspective view of a spacer, and FIG. 9 is an output waveform diagram. DESCRIPTION OF SYMBOLS 1... Housing, 6... Piezoelectric plate, 7... Conductive plate, 8, 18... Spacer, 9... Dome-shaped spring, 18a... Notch, 10... Plunger.

Claims (1)

[Scope of utility model registration request] A housing in which a plurality of terminals are implanted, a plunger movably attached to the housing, a piezoelectric plate polarized in the thickness direction and having electrodes on both sides and attached to the housing via an elastic member, comprising a conductive plate fixed to the upper surface, a substantially ring-shaped spacer placed on the conductive plate, and a dome-shaped spring placed on the spacer,
In a piezoelectric switch in which a dome-shaped spring is reversed by pressing down on a plunger to strike a conductive plate, a minute notch with a width ranging from 1° to 7° from the center of the spacer is formed in the spacer. A piezoelectric switch characterized in that it is configured to output a voltage of the same polarity twice: when the plunger is pushed down and when the plunger is released.