JPH0562409B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a keyboard switch comprising a key matrix used for data input, etc.

Configuration of the conventional example and its problems As shown in FIG. 4, the conventional keyboard switch has, for example, three row lines _L1 to _L3 , three column lines _L4 to _L6 , and a row line _L1. Nine switch elements SW ₁ ~ connected between each of ~L ₃ and each of the column lines L ₄ ~ _{L 6}
The switch elements SW ₁ to _{SW 9 are} turned on and off in response to key operations, and the row lines L ₁ to _{L 3} are provided with key matrix drivers DR.
The terminals O ₁ ~ O ₃ of are connected respectively, and the column wires L ₄ ~ _{L 6}
Terminals I 1 to I 3 of the key matrix receiver RC are connected to the terminals I ₁ to _{I 3} of the key matrix receiver RC.

In this case, the key matrix driver DR is designed to sequentially and periodically set the levels of the terminals O ₁ to _{O 3} to a low level (scanning), and the key matrix receiver RC is configured to determine which of the terminals I ₁ to I ₃ is low. Which key was pressed, that is, which switch element SW ₁ to _{SW 9} was turned on, is determined based on the low level and the timing at which the low level was reached.

However, with such a conventional keyboard switch, for example, when a scan output is being generated from terminal _O1 of the key matrix driver DR, three keys can be pressed at the same time to switch the switch element.
When SW ₁ to _{SW 9} are turned on at the same time, the conduction path of terminal I ₁ → switch element SW ₁ → terminal O ₂ and terminal I ₂ → switch element SW ₃ → switch element SW ₂ → switch element
A conduction path from SW ₁ to terminal O ₂ is formed.

The former conduction path connects the output of terminal O ₂ to terminal I ₁
This is an input, and it is detected that the switch element SW ₁ is turned on by the key operation corresponding to the switch element SW ₁ . In addition, the latter conduction path is the terminal
The output of O ₂ becomes the input of terminal I ₂ , and it is falsely detected that the key corresponding to switch element SW ₄ , which is not actually pressed, is pressed (ghost key detection).
In other words, it is falsely detected that the switch element _SW4 , which is not turned on, is turned on.

In order to prevent erroneous detection (ghost key detection) that a key that was not actually pressed due to simultaneous pressing of multiple keys is as shown in Fig. 5 as an example. A keyboard switch is proposed. This keyboard switch has three row lines L ₁ to L ₃ and three column lines L ₄ to
L ₆ and a series circuit of nine sets of switch elements and diodes SW ₁ , D ₁ ; SW ₂ , D ₂ connected between each of the row lines L ₁ to _{L 3} and each of the column lines L ₄ to _{L 6} ;……;
The terminals _O1 to _O3 of the key matrix driver DR are connected to the row lines _{L1 to L3 ,} respectively, and the key matrix receiver RC is connected to the column lines _L4 to _L6 . The terminals I ₁ to I ₃ of are connected and the diode
D ₁ to _{D 9} are connected so that the forward direction is from the key matrix receiver RC to the key matrix driver DR, and the terminals I ₁ to _{I 3} of the key matrix receiver RC are pulled up by resistors R ₁ to _{R 3} . has been done.

In this case as well, the key matrix driver DR and key matrix receiver RC are
Accordingly, it is determined which key has been pressed, that is, which of the switch elements SW ₁ to _{SW 9} has been turned on. For example, using FIG. 4 and explaining the same key operations as described above, in a state where the scan output is being generated from the terminal _O2 of the key matrix driver DR, pressing three keys at the same time will cause the switch elements SW ₁ to SW to be activated. ₃ are turned on at the same time, terminal I ₁ → switch element SW ₁ → diode D ₁
→ Conduction path of terminal O ₂ and terminal I ₂ → Switch element
SW ₃ → Diode D ₃ → Diode D ₂ → Switch element SW ₂ → Switch element SW ₁ → Diode D ₁ →
A conductive path for terminal _O2 is formed.

The former conduction path is in the forward direction with respect to the diode _D1 , so it is conductive, and as in the case of FIG. 4, the output of the terminal _O2 is the input of the terminal _I1 , so the switch element _SW1 Detects when the is turned on. The latter conduction path is reverse biased by the diode _D2 , so that the conduction path is blocked and ghost key detection, ie false detection of switch element _SW4 being turned on, does not occur.

However, in this configuration, each switch element
Diodes D ₁ to _{D 9} in series with SW ₁ to SW ₉ , respectively.
, a large board on which components can be mounted is required, and it can only be used with a limited number of keyboards that have space for mounting components, and it cannot be used with a full keyboard for data input. Keyboards in which a large number of key matrices are formed have a problem in that material and mounting costs (production costs) are high.

Purpose of the Invention The present invention is capable of significantly reducing production costs, and also prevents false detection that a key that is not actually pressed is pressed due to simultaneous pressing of multiple keys. The purpose is to provide a keyboard switch that can.

Structure of the Invention The keyboard switch of the present invention includes a row line and a column line, and a series circuit of a switch element and a resistance element connected between the row line and the column line at the intersection of these lines and responsive to key operations, The switch element and the resistance element are printed and formed, and the voltage input to the key matrix receiver is made different depending on when a key is actually pressed and when a ghost key is pressed due to simultaneous pressing of multiple keys. By discriminating the voltage level in
It is possible to prevent erroneous detection that a different key, which is not actually pressed, is pressed due to simultaneous pressing of a plurality of keys. Moreover, since the resistor is printed, it does not need to be mounted on a board etc. like a diode, eliminating the need for mounting space and mounting work, and greatly reducing material and mounting costs (production costs). Further miniaturization becomes possible.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 to 3. In addition, the key matrix driver
The operation of the DR is the same as that of the prior art, so a description thereof will be omitted. As shown in FIGS. 1A and 1B, this keyboard switch has a row line pattern 5 and lower contact patterns 2, 2' formed on the top surface of a substrate 7,
Column lines 8 are formed on the lower surface of the substrate 7, and resistor patterns 1 are formed on the upper surface of the substrate 7 by carbon printing to connect the row line pattern 5 and the lower contact pattern 2. It is connected to the column line pattern 8 by through-hole plating. On the other hand, the contact pattern 3 is formed on the lower surface of the film 4 so as to face the lower contact patterns 2 and 2', and the substrate 7 and the film 4 face each other with a separator 6 in between. That is, a plurality of row line patterns 5 and a plurality of column line patterns 8 constitute a matrix, and switch elements and resistance elements are formed by printing between the row line patterns 5 and column line patterns 8 at the intersections thereof. Although FIG. 1 shows only nine series circuits of switch elements and resistor elements, the number of series circuits of switch elements and resistance elements is not limited to this. The number of row lines and column lines increases accordingly.

This keyboard switch is activated by pressing down on the part of the film 4 that corresponds to the upper contact pattern 3.
The film 4 is bent and the lower contact patterns 2, 2'
is short-circuited by the upper contact 3,
The switch element consisting of the lower contact pattern 2, 2' and the upper contact pattern 3 is turned on.

Figure 2 shows the keyboard switch 4 shown in Figure 1.
, where r ₁ to r ₉ are resistors connected in series to the switch elements SW ₁ to SW ₉ , respectively, in place of the diodes D ₁ to D ₉ in FIG.
The other configurations are the same as in FIG. 5.

Next, let's change the operation of this keyboard switch to the third
This will be explained with reference to Figures A to D.

Figure 3A is the equivalent circuit of Figure 2 when one key is pressed (switch element SW ₁ is on), and the input voltage to terminal I ₁ of the key matrix receiver RC is
V _I1 becomes V _I1 = r ₁ /R ₁ + r ₁ V, and assuming R ₁ = 2r ₁ , V _I1 = 1/3 V.

Since pressing two keys at the same time is exactly the same as pressing one key, detailed explanation will be omitted.

Figure 3B is the equivalent circuit of Figure 2 when three keys are pressed simultaneously (switch elements SW ₁ , SW ₂ , SW ₃ are on), and the input voltage to terminal I ₁ of the key matrix receiver RC is V _I1 becomes V _I1 = r ₁ / r ₁ + 1/1 / r ₂ + r ₃ + R ₂ + 1 / R ₁ V, and assuming that R ₁ = R ₂ = 2r ₁ = 2r ₂ = 2r ₃ , V _I1 = 3 /7V. On the other hand, the input voltage (ghost key input voltage) V _I2 of the terminal I ₂ of the key matrix receiver RC is V _I2 = r ₂ + r ₃ / R ₂ + r ₃ + r ₂ (V - V _I1 ) + V _I1 , and R ₁ = Assuming that R ₂ =2r ₁ =2r ₂ =2r ₃ , V _I2 =5/7V.

Therefore, in the key matrix receiver RC, the input voltage can be set to 4/4 by setting the threshold appropriately.
If the switch element is determined to be on when the voltage is 7 V or less, and the switch element is determined to be off when the voltage exceeds 4/7 V, it will be determined that if the key is actually pressed (3/7 V) and other multiple It is possible to distinguish between ghosts caused by simultaneous key presses (5/7V), and ghost key detection can be prevented.

Figure 3C is the equivalent circuit of Figure 2 when four keys are pressed simultaneously (switch elements SW ₁ , SW ₂ , SW ₃ and SW ₅ are on), and the key matrix receiver
The input voltage V ₁₁ to terminal I ₁ of RC is VI1=r ₁ r ₁ +11/R ₁ +1/r ₂ +1/1/R ₂ +r ₃ +1/R
₃ + r ₅ V, and assuming that R ₁ = R ₂ = R ₃ = 2r ₁ = 2r ₂ = 2r ₃ = 2r ₅ , V _I1 = 9/19V. In addition, the input voltage to terminals I ₂ and I ₃ of the key matrix receiver RC (ghost key input voltage
V _I2 and V _I3 are, when R ₂ = R ₃ = R and r ₃ = r ₅ = r, V _I2 = V _I3 = r + r/2/r + r/2 + R/2 × (V-
V _I1 ) + V _I1 , and assuming R=2r, V _I2 = V _I3 = 15/19V.

Therefore, in the key matrix receiver RC, for example, when the threshold value is set appropriately and the input voltage is 12/19V or less, the switch element is turned on.
By determining that the switch element is off when the voltage exceeds 12/19V, it will be possible to detect only when a key is actually pressed, and ghost key detection can be prevented.

Figure 3D is an equivalent circuit when N keys are pressed simultaneously to create the worst condition for key detection, and the input voltage V _I1 to terminal I ₁ is R ₁ , ..., R _o = R r ₁ , ..., r _o = r, then V _I1 = rr+1/1/R+1/r+R+r/n-2V, and assuming R=2r, V _I1 =3n-3/5n-1V. Become.

Also, the ghost key input voltage V _IN is V _IN =r+r/(n-2)/r+(r+R)/(n-2
)(V-V _I1 )+V _I1 , and assuming R=2r, V _I1 =5(n-1)/5n-1V. If the number of pressed keys is infinite, then V _I1 = n→∽3/5V V _IN = n→∽1V, and if the resistance ratio is R=2r, it is 5/7V (0.714V).
Ghost key detection when the N key is pressed can be easily prevented by setting the threshold of the key matrix receiver RC so that the following is determined to be off and 3/5V (0.6V) or less is determined to be on. I can do it.

In this embodiment, as described above, detection of a ghost key can be prevented (N-key rollover is possible) by level-discriminating the input voltage of the key matrix receiver RC using a predetermined threshold voltage. In addition, since the resistor for this purpose is formed on the board 1 by carbon printing, there is no need for space for mounting components, no mounting work is required, and it can be easily mounted on the printed board 1 or film 4. A resistor can be installed, resulting in a significant cost reduction compared to a diode.
Moreover, miniaturization can be achieved.

Effects of the Invention The keyboard switch of the present invention connects a series circuit of a switch element and a resistor element between the row line and column line at the intersection of the row line and column line constituting the matrix, and connects the resistor element. Because it is printed, the voltage input to the key matrix receiver will differ depending on whether a key is actually pressed or when a ghost occurs due to simultaneous pressing of multiple keys. Ghost key detection can be prevented by performing discrimination. However, since resistors are printed, they do not need to be mounted on a board like diodes, and mounting space and mounting work are no longer required. Materials and mounting costs (production costs) can be significantly reduced. It becomes possible to downsize.

[Brief explanation of drawings]

1A and 1B are respectively a plan view and a side view of an embodiment of the present invention, and FIG. 2 is an electric circuit diagram thereof.
3A to 3D are equivalent circuit diagrams of FIG. 2, and FIGS. 4 and 5 are circuits of conventional keyboard switches, respectively. 1...Resistance pattern (resistance element), 2, 2'...
Lower contact pattern (switch element), 3... Upper contact pattern (switch element), 4... film,
5...Row line pattern, 8...Column line pattern.

Claims (1)

[Claims] 1. Responds to a plurality of row lines, a plurality of column lines that constitute a matrix of the plurality of row lines, and key operations provided in series by printing between the row lines and column lines at the respective intersections of this matrix. a switch element, a resistor element, a key matrix driver connected to one of the plurality of row lines or the plurality of column lines and scanning the plurality of row lines or the column lines; a key matrix receiver that is connected to the other column line of the keyboard and that discriminates the voltage level of each of the connected row lines or column lines to prevent ghost key detection.