JPS6012729B2 - piezoelectric keyboard switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a keyboard switch using a piezoelectric element made of a polymeric piezoelectric material.

As shown in Fig. 1, this type of Shoden keyboard switch has a plurality of electrode parts 2 on the top surface and a plurality of electrodes extending from the electrode parts 2 on the bottom surface through conductive through holes 4. A piezoelectric element 5 made of a polymeric piezoelectric material in the form of a sheet or film is placed on the top surface of the printed wiring board 1 on which the signal extraction leads 3 are formed, and a common electrode layer 6 is further placed on top of the piezoelectric element 5. It is known that these are combined together. In such a keyboard switch, a sufficient compressive displacement (strain) cannot be applied to the piezoelectric element 5 by the force of a human finger alone, and it is not possible to generate a voltage. It is assembled in one piece.

Therefore, the structure as a switch becomes bulky, making it completely unsuitable for use in thin and small computer keyboards.Also, since multiple switch elements are constructed on a single piezoelectric element on the same substrate, arbitrary switch elements can be used. When a switch element is impacted, the impact force propagates to adjacent switch elements and generates unnecessary voltage, which is a troublesome and difficult problem that requires countermeasures. It had many drawbacks, such as being extremely uneconomical because the parts other than the elements were also made of expensive piezoelectric material. The present invention provides a piezoelectric keyboard switch that does not have the above-mentioned disadvantages, and will be described below with reference to the drawings.

In FIG. 2, reference numeral 11 indicates a plurality of electrode portions 12 arranged at appropriate intervals on the upper surface and a plurality of signal extraction lead portions 13 extending from the electrode portions 12 to the lower surface via conductive through holes 14.
. . ., each end portion of the lead portion 13 . . . is connected to a medium wide external terminal 1.
33... are assembled at one end of the substrate 11.

Furthermore, one external terminal 13b is simultaneously formed adjacent to the group of external terminals 13a, which is electrically connected to a conductive rubber sheet to be described later. 15 is a conductive rubber sheet attached to the upper surface of the printed wiring board 11 via an insulating spacer to be described later; 16 is an insulating spacer made of rubber, plastic, etc.; Part 15a facing part 12...
There is a space S between the electrode part 12 and the electrode part 12 so that the electrode part 12 can be elastically deformed by the pressing force of a human finger.
It has a plurality of noble holes 16a forming...

17...'' are a plurality of piezoelectric elements made of a polymeric piezoelectric material bonded to the lower surface of the movable portion 15a... of the dew conductive rubber sheet in the space S, and are normally connected to the electrodes of the wiring board. Part 1
2... They face each other with a certain gap in between, and when pressed against the movable portions 15a...' of the conductive rubber sheet, they are curved and deformed and come into contact with the electrode portions 12..., respectively.

Here, the polymeric piezoelectric materials are those that have piezoelectric properties themselves, such as polyvinylidene fluoride and polyvinyl chloride, and those that are made by mixing strong electromagnetic ceramic powder such as lead zirconate titanate in synthetic rubber or synthetic resin. refers to To explain the operation of the switch of the present invention having the above configuration, any movable part on the conductive rubber sheet 15, for example 15a', is pressed directly with a finger from above (
As shown by the arrow), the movable portion 15a' is easily curved and deformed due to the space S, but at the same time, the piezoelectric element 17 bonded to the lower surface of the movable portion is also deformed as a unit due to its own flexibility.

At this time, distortion occurs inside the piezoelectric element, and positive and negative charges are induced on the upper and lower surfaces of the piezoelectric element. Furthermore, when the movable part 15 of the conductive rubber sheet 15 is further pressed, the amount of electric charge on the piezoelectric element increases, and when the electric charge is sufficiently increased, the lower surface of the piezoelectric element comes into contact with the electrode part 12 of the printed circuit board, and the lower surface of the piezoelectric element The accumulated positive or negative charge moves to the electrode part 12, and the conductive rubber sheet 15 contacts the electrode part 12 and the top surface of the piezoelectric element.
A voltage is generated between the This voltage is extracted from the external terminal 13a of the lead section 13 extending from the electrode section 12 and the external terminal 13b electrically connected to the conductive rubber sheet, and is applied as a switch signal to a predetermined electronic circuit. . Next, when the pressing force of the conductive rubber sheet against the movable portion 15a' is relaxed, the movable portion 15a' and the piezoelectric element 17 return to the initial state shown in FIG.

During this return process, charges opposite to those before are induced on the upper and lower surfaces of the piezoelectric element, but since the lower surface of the piezoelectric element is separated from the electrode portion 12, unnecessary voltage is reliably removed. FIG. 3 shows another embodiment of the present invention, in which a conductive rubber sheet 15 is directly adhered to the upper surface of a printed wiring board 11, and a portion facing a plurality of electrode parts 12 on the board. The convex shape 15b...
The conductive rubber sheet is bulged to form a space S between the electrode part 12 so that the bulge part 15b of the conductive rubber sheet can freely curve and deform. A plurality of piezoelectric elements 17 are provided on the inner surface of the movable bulging portion 15b, respectively.
... are integrally joined, and the switch operation is as explained in FIG. 2.

In addition, in FIGS. 2 and 3 above, the electrode section 12 formed on the top surface of the printed circuit board in order to code the switch operation circuit.
may be one or more divided electrodes. As described above, in the piezoelectric keyboard switch of the present invention, a conductive rubber sheet is adhered to the upper surface of a printed wiring board having a plurality of electrode sections on the upper surface and a plurality of lead sections extending from the upper surface. A space is formed between the wiring board and the electrode part so that the part facing the electrode part is elastically curved and deformed by the pressing force of a finger, and a plurality of spaces are formed in the movable part of the conductive rubber sheet within the space. piezoelectric elements are assembled together, and the piezoelectric element is always opposed to the electrode part with a certain gap therebetween, and is configured so that when the movable part of the conductive rubber sheet is pressed, it comes into contact with the electrode part and generates a voltage. Since the switch can be operated reliably even with weak finger force, there is no need for any conventional parts such as push buttons, and the structure of the switch can be made extremely thin. It is possible to apply it to a desktop calculator, and since according to the configuration of the present invention a piezoelectric element is used for each unit of switch element, it is possible to configure a plurality of switch elements on one piezoelectric sheet. Various problems such as unavoidable crosstalk can be solved at the same time.Furthermore, according to the present invention, the piezoelectric element is curved and deformed to accumulate enough charge before it contacts the electrode part of the printed circuit board. When the piezoelectric element comes into contact with the electrode part, it instantly releases a charge and generates a voltage, which is the clever switch mechanism.The switch can operate reliably not only with rapid pressing force but also with relatively slow pressing force. It can bring great benefits as a keyboard switch for electronic desk calculators.

[Brief explanation of drawings]

Figure 1 shows a conventional piezoelectric keyboard switch.
A is a front view, B is a back view, C is a sectional view taken along the line E in Figure A, and Figure 2 shows a piezoelectric keyboard switch according to an embodiment of the present invention, A is a front view, B is a back view, and C is a view in A. 3 is a cross-sectional view taken along the Rollo line, and D is a cross-sectional view showing a state in which the movable part of the switch is pressed. FIG. 3 shows another embodiment of the present invention, A is a front view, B is a back view, and C is a It is a sectional view along the Haha line in Figure A.11.
...Printed wiring board, 12...Electrode section, 1
3... Lead part, 15... Conductive rubber sheet, 15a, 15b... Movable part, S... Blank space, 1
7...Piezoelectric element. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A conductive rubber sheet is attached to the upper surface of a printed wiring board having a plurality of electrode parts on the upper surface and a plurality of lead parts extending from the upper surface, and the part of the conductive rubber sheet that faces the electrode parts of the wiring board is shaped like a finger. A space is formed between the electrode part so as to be elastically curved and deformed by a pressing force, and a plurality of piezoelectric elements are bonded to the movable part of the conductive rubber sheet within the space, and the piezoelectric element is always on. A piezoelectric keyboard switch that faces an electrode part with a certain gap in between and is configured so that when a movable part of a conductive rubber sheet is pressed, it comes into contact with the electrode part and generates a voltage.