JPH06332598A - Membrane keyboard - Google Patents

Abstract

PURPOSE:To prevent a cross talk phenomenon and to strengthen the resistance to electrostatic noise regarding the membrane keyboard with a membrane switch formed by printing electrode patterns on an insulated film. CONSTITUTION:An upper sheet 21 having formed electrode pattern provided with plural electrode parts 25a-25d constituting a switch(SW), is made face all electrode parts 25a-25d. Further, a support member 23 having a common electrode part which is electrically connected with the electrode parts 25a-25d, resistances r1-r4 respectively provided on the plural electrode parts 25a-25d and for performing processing for identifying the switch for signals passing through the electrodes 25a-25d when the switch is controlled at the time of operation, and a spacer 22 separating the electrodes 25a-25d from the common electrodes 28 at the time of no operation are provided. the upper sheet 21 and the support member 23 are arranged in facing each other through the spacer 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane keyboard, and more particularly to a membrane keyboard formed by printing an electrode pattern on an insulating film.

Generally, a membrane keyboard is widely used as an input device of a computer. This membrane keyboard has a plurality of operation keys, and the input processing can be performed by pressing a single operation key or a plurality of operation keys at the same time. This keyboard is composed of a key top which is directly operated and a membrane switch which is arranged below the key top and which is electrically connected corresponding to the operation.

On the other hand, especially in recent years, computers have become complicated, and accordingly, commands and data to be input have also become complicated, and a plurality of operation keys are often operated at the same time. Also, if a defect occurs in the input process,
Even if the processing by the computer is normally performed, the output content will deviate greatly from the desired content. When operating multiple operation keys at the same time, so-called "wraparound"
It is known that a phenomenon referred to as "occurs" occurs, and the same phenomenon occurs when an operation key that is not operated is operated even if the operation key is operated properly.

Therefore, there is a demand for a membrane keyboard capable of performing accurate input processing without wraparound.

[0005]

2. Description of the Related Art FIG. 6 shows an example of a conventional membrane keyboard. As shown in the figure, a membrane switch 1 arranged in a conventional membrane keyboard is composed of an upper sheet 2, a lower sheet 3 and a spacer 4, and is arranged on a support panel 5.

In the upper sheet 2 and the lower sheet 3, electrode patterns 8 and 9 are formed on insulating films 6 and 7, respectively, and an upper electrode portion 10 and a lower electrode portion 11 which form a switch element are provided at predetermined positions. Are formed. The upper sheet 2 and the lower sheet 3 are laminated so as to face each other with a spacer 4 made of an insulating material interposed therebetween.

Further, holes 12 are formed in the spacers 4 at positions facing the respective electrode portions 10 and 11, so that when a predetermined position of the upper sheet 2 is pressed, the upper sheet 2 is pressed.
Is configured so that the upper electrode portion 10 which is flexible and is formed below the pressing position is brought into pressure contact with the lower electrode portion 11 which is formed at a position opposite to the upper electrode portion 10 to be electrically connected.

The support panel 5 is, for example, a metal plate made of iron, aluminum, or the like, and is disposed below the laminated lower sheet 3 and includes the upper sheet 2, the lower sheet 3, the spacer 4 and the like. It is something to support.

FIG. 7 is a circuit diagram of the membrane switch 1. As shown in the figure, the membrane switch 1 includes a drive line 14 connected to the drive circuit 13 (corresponding to, for example, the electrode pattern 8) and a detection line 16 connected to the detection circuit 15 (corresponding to, for example, the electrode pattern 9). ) And the lines 14 and 16 are arranged in a matrix. Upper electrode part 10 and lower electrode part 11
The switch 17 constituted by is formed at each intersection of the drive line 14 and the detection line 16 arranged in a matrix.

As a method for detecting the operated switch 17, a drive signal is supplied from the drive circuit 13 to each drive line 14, and when the switch 17 is closed, the drive circuit 13 drives the drive line 14. The drive signal supplied to the drive circuit 13 is supplied to the detection line 16.
The method of specifying the drive line 14 to which the drive signal is supplied from the above and the operated switch 17 by detecting the detection line 16 from which the drive signal is detected have been adopted.

[0011]

Membrane switch 1 provided in the above-described conventional membrane keyboard.
Then, when a plurality of operation keys are operated at the same time, so-called "wraparound" may occur. Hereinafter, this wraparound phenomenon will be described.

Now, let us say that among the plurality of switches (hereinafter abbreviated as SW) formed in FIG. 8, only SW1 is operated. Then, the SW operated according to the above-described detection method is detected. Specifically, when the drive circuit 13 outputs a drive signal to the output terminal a, this drive signal is (a
-j) → (ai) → (ah) → (ag) → (SW1) → (bf) → (c-
f) → (df) → (ef)
Input to the input terminal f. Therefore, when a drive signal is output to the output terminal a of the drive circuit 13 and this is detected by the input terminal f of the detection circuit 15, it can be detected that the SW1 has been operated.

However, as described above, in the membrane switch 1, a plurality of operation keys may be operated simultaneously. Now, a case where SW2 to SW4 shown in FIG. 8 are simultaneously operated will be described as an example.

The fact that SW2 has been operated means that a drive signal is output to the output terminal b of the drive circuit 13 by the same detection method as described above, and when this is detected by the input terminal f of the detection circuit 15, SW1 is operated. It can be detected that it has been done. Further, when SW3 is operated, a drive signal is output to the output terminal b of the drive circuit 13, and the input terminal g of the detection circuit 15 detects the signal. It is possible to detect by outputting a drive signal to the output terminal a of and detecting this at the input terminal g of the detection circuit 15.

When SW2 to SW4 are operated as described above, by closing SW4, the drive signal output from the output terminal a of the drive circuit 13 passes through the closed SW4 (bg ) And then enters the drive line connected to the output terminal b of the drive circuit 13 through the closed SW3. In this case, the drive signal entering the drive line connected to the output terminal b is closed S
It advances through W2 to the detection line connected to the input terminal f of the detection circuit 15 and is supplied to the input terminal f (the path of the drive signal is shown by an arrow in the figure).

That is, when the drive signal is taken through this signal path, the drive signal output from the output terminal a of the drive circuit 13 is detected by the input terminal f of the detection circuit 15. As described above, in the normal case, the drive signal output from the output terminal a of the drive circuit 13 is detected by the input terminal f of the detection circuit 15 when the SW1 is closed.
However, by operating SW2 to SW4 at the same time, a state equivalent to that when SW1 is closed may occur, resulting in erroneous input (this phenomenon is referred to as "wraparound"). This wraparound phenomenon is, as is clear from the above description, the drive line 14 and the detection line 1.
6 is arranged in a matrix.

As means for preventing this "wraparound", the following methods have been conventionally adopted.

(1) Software method (for example, 3
(If more than one SW is operated at the same time, the input operation is locked by software.) (2) Method of mounting a diode on each switch (in the above example, drive in the direction indicated by the arrow in SW3) (3) A method of forming a resistor or capacitor in each switch section (when the drive signal passes through the switch, the current value or voltage value changes due to the resistor or capacitor,
However, among the means to prevent "wraparound", (1) The method using software may limit the maximum number of operation keys that can be operated simultaneously to two, which is complicated. There is a problem that it is not possible to deal with a computer having a different command.

Further, (2) the method of mounting a diode in each switch section requires as many diodes as the number of switches, which leads to a significant cost increase.

(3) In the method of forming a resistor or a capacitor in each switch section, it is not possible to prevent "wraparound" against the pressing of an arbitrary number of keys. For example, SW2, SW3 in FIG. SW5, S in addition to SW4
When W9 and SW10 are operated simultaneously, there is a problem that as the number of pressed keys increases, a phenomenon equivalent to that when SW1 is operated may occur.

Further, in the conventional membrane switch 1,
Since the area of each electrode 10, 11 is small, electrostatic noise (E
The resistance to SD (Electro Stafic Discharge) is weak, and a discharge occurs when a charged operator operates a key or the like, and an erroneous signal occurs due to this, and each electrode 10, 1
1 and the circuit parts connected to the membrane sheet may be damaged.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a membrane keyboard capable of preventing a wraparound phenomenon and enhancing resistance to electrostatic noise.

[0023]

In order to solve the above-mentioned problems, in a membrane keyboard according to the present invention, an electrode sheet having an electrode pattern having a plurality of electrode portions constituting a switch is formed on an insulating film. A support member having a common electrode portion electrically connected to the plurality of electrode portions at the time of operation, and each of the plurality of electrode portions are provided, An identification unit that performs a process for identifying the switch with respect to a signal that passes through the electrode section when the switch is operated, and a spacer that separates the electrode section and the common electrode from each other when the switch is not operated. It is characterized in that it has a membrane switch having a structure in which an electrode sheet and a support member are arranged to face each other.

[0024]

With the above structure of the membrane keyboard, the operated switch can be detected without forming the electrode pattern of the membrane switch in a matrix structure. Therefore, the wraparound phenomenon does not occur, and accurate input processing can be performed.

Since the common electrode can have a large area, the influence of electrostatic noise can be eliminated.

[0026]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is an exploded perspective view of a membrane switch 20 provided in a membrane keyboard which is an embodiment of the present invention. As shown in the figure, the membrane switch 20 according to the present invention is roughly composed of an upper sheet 21, a spacer 22, a support panel 23 and the like.

The upper sheet 21 has a structure in which a plurality of upper electrode portions 25a to 25d are formed by printing on an insulating film 24 made of resin, for example. FIG. 2 is an enlarged view of the upper sheet 21. As shown in FIG. 2, four electrode patterns 26 are formed on the insulating film 24 in this embodiment.
a-26d are formed, and each electrode pattern 26a-
Five upper electrode portions 25a to 25d are connected to the 26d, respectively.

Further, a resistance r1 is provided at a position where the upper electrode portions 25a to 25d are connected to the respective electrode patterns 26a to 26d.
.About.r5 (corresponding to the identification means of the switch) is formed by, for example, thick film printing, and the resistance values of the resistors r1 to r5 are different from each other. The resistors r1 to r5 are connected to the upper electrode portions 25a to 25d.
Is connected to the electrode patterns 26a to 26d, so that the upper electrode portions 25a to 25d are connected to the electrode patterns 26a to 26d via the resistors r1 to r5.

Returning to FIG. 1 again, the spacer 2 will be described.
2 is formed of a resin insulating material, and has holes 27 formed at positions corresponding to the formation positions of the respective upper electrode portions 25a to 25d. The support panel 23 is made of, for example, a conductive material such as iron or aluminum, or a common electrode portion 28 (indicated by a satin finish) made of a conductive material is formed on the upper part of the panel body 23a made of an insulating material by a printing method, a vapor deposition method, or the like. Has been formed. The common electrode portion 28 is formed as a film over the entire upper surface of the panel body 23a.

Further, in this embodiment, since the common electrode 28 is integrated with the support panel 23, the lower sheet 3 (see FIG. 6) which is conventionally arranged can be dispensed with. Therefore, the number of parts can be reduced, and the membrane keyboard 20 can be thinned to some extent.

The above-mentioned upper sheet 21 is joined to the upper part of the support panel 23 with a spacer 22 interposed therebetween. Therefore, in the assembled state, the support panel 23
A spacer 22 and an upper sheet 21 are sequentially stacked on the upper part of the. In the assembled state, the upper electrode portions 25 a to 25 d formed on the upper sheet 21 are connected to the common electrode portion 28 via the holes 27 formed in the spacer 22.
It is configured to face. Reference numeral 29 is a ground electrode to which a lead wire for connecting the common electrode portion 28 to a signal ground of an operation switch detection circuit 30 described later is connected.

The membrane switch 20 having the above structure
When one or a plurality of upper electrode portions 25a to 25d are pressed, the operated upper electrode portions 25a to 25d move downward as the insulating film 24 flexibly deforms, and are formed on the spacer 22. Common electrode portion 28 through the hole 27
And is electrically connected. At this time, the common electrode portion 2
Since 8 is integrated with the entire upper surface of the support panel 23, all of the upper electrode portions 25a to 25d are connected to the common electrode portion 28 during operation.

Further, the common electrode portion 28 is the support panel 2
Since it is integrated with the entire upper surface of 3, the installation area is large, and therefore electrostatic noise (ESD: Electro Stafic Disch)
It is highly resistant to arge), and it is possible to effectively prevent generation of erroneous signals due to discharge, and damage to the electrodes 25a to 25d, 28 and circuit components connected to the membrane sheet.

Here, FIG. 3 shows a circuit diagram in a state where the membrane switch 20 is connected to the operation switch detection circuit 30. As shown in the figure, the membrane switch 20 according to the present embodiment is different from the conventional structure in which the drive lines 14 and the detection lines 16 are arranged in a matrix (see FIG. 7), and the upper part of each electrode pattern 26a to 26d is provided. Electrode part 25
It has a structure in which switches SW _{a1 to} SW _d5 configured by a to 25 _d and the common electrode portion 28 are connected in parallel. The resistor r1~r5 are provided with different resistance values above the respective switches SW _a1 to SW _d5.

The operation switch detection circuit 31 includes an 8-bit analog / digital converter 32 (hereinafter, referred to as an A / D converter) of each of the resistors r1 to r4, 8-channel analog input full-scale transition 5V, and a microminiature arithmetic unit. 33 (hereinafter referred to as MPU) and the like.

The electrode patterns 26a to 26d are A / D
It is connected to the analog input terminals a to d of the converter 31 and is also connected to the power supply V _CC via the pull-up resistor r. The common electrode portion 28 is grounded.

In the above structure, the switches SW _{a1 to} SW a
_When one or more _d5 are selectively closed, the potential applied to the analog input terminals a to _d of the A / D converter 32 changes. The A / D converter 31 generates a switch identification signal by performing analog / digital conversion based on the potential applied to each of the analog input terminals a to d. A /
The switch identification signal generated by the D converter 32 is MP
The switch SW transmitted to the U33 determines the operated switch SW based on the switch identification signal, and executes the command associated with the switch SW.
In the present embodiment, the operation switch detection circuit 31 is constituted by the A / D converter 32 and the MPU 33 which are independent of each other, but the MP having the built-in A / D converter is shown.
It is also possible to use U.

Here, the operation of the membrane keyboard having the membrane switch 20 configured as described above will be described with reference to FIGS. 4 and 5. For convenience of explanation, 4
The case where the individual switches SW1 to SW4 are formed will be described as an example. Further, the resistance value of the resistance r provided in each of the switches SW1 to SW4 is such that SW1 is r1, SW
2 is set to 2 × r1, SW3 is set to 3 × r1, and SW4 is set to 4 × r1.

Therefore, by selectively operating the switches SW1 to SW4, the potential (voltage) applied to the analog input terminal a of the A / D converter 31 becomes different. FIG. 5 shows the relationship between the operated switch and the detection potential φ applied to the analog input terminal a. As shown in the figure, when all the switches SW1 to SW4 are not operated, V _CC is applied to the analog input terminal a.
Is applied to all the switches SW1 to SW1.
When SW4 is operated, the analog input terminal a
A voltage of 1.62V will be applied. Similarly, a voltage corresponding to the operated switch is applied to the analog input terminal a depending on the type or combination of the operated switches SW1 to SW4.

In the configuration example shown in FIGS. 4 and 5, the resolution is 5 (V) / 2 ⁸ = 0.02 (V),
The operated SW can be specified with a sufficient margin.

Further, as described above, the membrane switch 20 according to the present embodiment is different from the conventional one in which the drive line 14 and the detection line 16 have a matrix structure, and therefore the "wraparound" that occurs due to the matrix structure occurs. Can be reliably prevented, and accurate input processing without erroneous input can be performed.

In the above-mentioned embodiment, the spacer 22 which is a member independent of the upper sheet 21 is used. However, like the membrane switch 31 shown in FIG. The sheet 21 may be provided with the print spacer 30 formed by printing using an insulating material.

[0043]

As described above, according to the present invention, it is possible to detect an operated switch without forming the electrode pattern in a matrix structure. Therefore, the wraparound phenomenon does not occur, and accurate input processing can be performed.

Further, since the common electrode can have a large area W, the influence of electrostatic noise can be eliminated.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a membrane switch that is an embodiment of the present invention.

FIG. 2 is an enlarged view of an upper sheet.

FIG. 3 is a circuit diagram of a membrane switch that is an embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the membrane keyboard according to the embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between an operated switch and a detection potential φ applied to an analog input terminal.

FIG. 6 is an exploded perspective view of a membrane switch which is a modified example of the membrane switch shown in FIG.

FIG. 7 is an exploded perspective view of a conventional membrane keyboard.

FIG. 8 is a circuit diagram of a conventional membrane keyboard.

FIG. 9 is a diagram for explaining a wraparound phenomenon.

[Explanation of symbols]

 20, 31 Membrane switch 21 Upper sheet 22 Spacer 23 Support panel 23a Panel body 24 Insulating film 25a-25d Upper electrode 26a-26d Feeding electrode part 27 Hole 29 Ground electrode 30 Printing spacer 31 Operation switch detection circuit 32 A / D reconverter 33 MPU

Claims (6)

[Claims] 1. An electrode sheet (21) comprising an insulating film (24) and electrode patterns (26a-26b) each having a plurality of electrode portions (25a-25d) forming a switch (SW). , Is configured to face all of the plurality of electrode portions (25a to 25d), and the electrode portions (25a to 25d) are operated during operation.
A support member (23) having a common electrode portion electrically connected to the electrode member and a plurality of electrode portions (25a to 25d), which are provided respectively, pass through the electrode portions (25a to 25d) when the switch is operated. Identification means (r1 to r4) for performing processing for identifying the switch with respect to a signal, the electrode portions (25a to 25d) and the common electrode (2) when not operated.
8) and a spacer (22) for separating it from each other, and a membrane having a membrane switch having a structure in which the electrode sheet (21) and the support member (23) are arranged to face each other with the spacer (22) interposed therebetween. keyboard. 2. The membrane keyboard according to claim 1, wherein the support member (23) is made of a conductive material, and the common electrode portion (28) is integrated with the support member (23). . 3. The support member (23) is characterized in that a common electrode portion (28) made of a conductive thin film is formed on a support member book (23a) body made of an insulating material. The membrane keyboard according to 1. 4. The membrane keyboard according to claim 3, wherein the support member (23) is formed by using a part of a housing forming a keyboard case. 5. The identification means is a resistance element (r1 to r5) having a different resistance value, which is provided in each of the plurality of electrode portions, and is different in resistance value from each other. Membrane keyboard. 6. The plurality of electrode portions (25a-25d) are
The membrane keyboard according to any one of claims 1 to 5, wherein the membrane keyboard is connected to an analog input side of an analog-digital exchange (32) which constitutes the operation switch detection means (31).