JPS5887676A - Position detector - Google Patents

Abstract

PURPOSE:To detect position coordinate simply, accurately and highly stably, by forming a conductive film on one surface of a pressure sensing sheet and a resistive plate on the other surface, providing electrodes around the resistive plate and supplying a constant current from the conductive film side. CONSTITUTION:A tablet 11 has a laminating construction that a conductive film 13 is formed on one side of a pressure sensing sheet 12 consisting of pressure sensor and a resistive plate 14 is arranged on the other side. Electrodes 15a-15d having diodes in the current flowing direction are provided around the plate 14. The pair electrodes 15a, 15b are connected in common via resistors 16a, 16b and then to a switch 17b and the pair electrodes 15c, 15d are connected to a switch 17a via resistors 16c, 16d. The switches 17a, 17b are alternately conducted. A constant current flows to the resistive plate from a power supply 19 via the film 13 and the depressed position of the sheet 12 and flows out from each electrode with a current ratio in response to the position. The current value is detected at amplifiers 23a, 23b.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a position detection device that inputs position coordinates using a pressure-sensitive sheet made of a pressure-sensitive resistor.

Technical Background of the Invention A position detection device is constructed using a pressure-sensitive sheet made of a pressure-sensitive resistor whose resistance value changes depending on the applied pressure.
It has many advantages as a coordinate input device that can easily detect the position coordinates of the sensitive sheet to which pressure is applied. FIG. 1 is a block diagram showing a conventional example of this position detection device, and 1 is a tablet. This tablet 1 is
It has a laminated structure in which a conductive film 3 such as a metal sheet is disposed on the upper surface of the pressure sensitive sheet 2, and a resistive plate 4 is disposed on the other lower surface. Around the resistor plate 4, electrodes 1it, ah, 6., 66 consisting of a group of diodes are formed.

A constant voltage is selectively applied to the electrodes 5m, 8b, 5e, and 54 from the power source 1 via a switch circuit 6. For example, the voltage at electrodes Sa, jib
A voltage is applied between the electrodes 1 and 64 to form a potential gradient in the lateral (X) direction of the resistor plate 4, and a voltage is applied between the electrodes 1 and 64 to form a potential gradient in the lateral (X) direction of the resistor plate 4.
It forms a potential gradient in the MY) direction.

The switching is performed by the switch circuit. With respect to the resistor plate 4, which is given a predetermined potential distribution as shown in FIG. Functions as a switch. "The voltage of the resistor plate 4 at the pressure application position, which is guided to the conductive film 2 by this short circuit, is detected by the tank radiator a as data indicating the position coordinates. Therefore, it is possible to control the switching of the switch circuit. Therefore, the indicated position of the pressure-sensitive sheet 2 is detected as the X-direction coordinate and the Y-direction coordinate, respectively, and the position detection is performed immediately.

Problems with the Background Art However, pressure is not always applied to the pressure-sensitive sheet 2, and pressure is applied to the indicated position only when a coordinate position consisting of an instruction is specified.
Since pressure is applied only to 1 and 1 when the ion is turned on, in order to efficiently detect the position described above, it is necessary to detect the ion.
Although the pen-on is monitored by detecting whether or not a voltage is generated, the potential on the conductive M3 when the pen is not on is in a very unstable state due to its high impedance. Therefore, in order to accurately detect the on-on state, a resistor 10 is connected in parallel through switch 9 to lower the impedance. The resistance plate 4 via 10
A problem arose in that the detection position accuracy deteriorated because current flowed from the It has also been considered to reduce the impedance of the conductive film 3 by turning on the switch 9 only when pen-on is detected, but this poses problems such as complicating the timing control, which is not practical. The invention was made in consideration of these circumstances, and its purpose is to provide practicality that allows position coordinates to be detected easily, accurately, and with high stability without the need for complex control. The object of the present invention is to provide a position detection device with high performance.

Summary of the Invention The present invention comprises forming a conductive film on one side of a pressure-sensitive sheet made of a pressure-sensitive resistor, forming a resistive plate on the other side, and providing electrodes for current flow around each of the resistive plates. The tablet is designed to supply a constant current from the membrane side. When the conductive film and the resistive plate are short-circuited at the indicated position by applying pressure, the coordinates of the indicated position are detected by detecting the current flowing out from each electrode corresponding to the indicated position. This is what I did.

Effects of the Invention According to the device of the present invention configured as described above, the impedance of the conductive film does not become higher than necessary, and the position coordinates are directly detected from the value of the current flowing from each electrode, so it is stable. In addition, highly accurate position detection is possible. Moreover, unlike conventional devices, complicated switch control is not required, and the on/off signal from ink and chi can be easily detected, so the device structure can be simplified and has practical advantages. is enormous.

Embodiment of the Invention Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic configuration diagram of the embodiment device, and 11 in the figure is a doublet. This doublet 11 has a pressure-sensitive sheet 1 made of a pressure-sensitive resistor, similar to the conventional device shown in FIG.
It has a laminated structure in which a conductive film 13 made of a metal sheet is disposed on one surface of 2 by vapor deposition, sintering, taring, etc., and a resistive plate 14 is disposed on the other surface. Above pressure sensitive sea
When the position where the doublet 11 is to be formed is specified by pressing the button or the like, the resistance value at the specified position is changed according to the pressure, and the conductive film 13 and the resistance plate 14 are short-circuited at the specified position. Therefore, the resistance plate 14
Around the electrode 16a, the opposing sides form a pair of diodes through which current flows.

15b, 15e, and lad are provided. Further, electrodes 15a are arranged in pairs to face each other.

J5b is connected in common through resistors 16h and 16b, and then connected to switch lrb, and the other pair of electrodes 15er and 156 are connected in common through resistor 16C2J6d, and then switch lrb.

11a. These switches 11th
, lrb are alternately driven to conduct at a predetermined period, and the other terminals of the switches 11m and llb are commonly connected and grounded via a resistor 18.

The power supply unit 19 is realized by configuring a constant current source by an amplifier 22 which divides the reference voltage 20 by a resistor 21 and uses it as one input, and uses the terminal voltage of the resistor 18 as the other input. This constant current output is then supplied to the conductive film 13 of the tablet 11. A constant current supplied from this electric part 19 is applied to the conductive film 7.
3 flows into the resistance plate 14 via the short-circuit point, which is the pressing position of the pressure-sensitive sheet 12 degrees, and is divided at a current ratio according to the position to each of the electrodes 15a.

They flow out from J5b, J5c, and J5d, respectively.

Note that when the switch 11a is turned on, the current flows out from the electrodes 75&, J5b, and flows through the resistors 36a, Ja
After passing through the resistor 18 from the switch JF&, the current flows through the resistor 18. Further, when the switch 11b is turned on, the current supplied from the conductive film 13 is divided at the required current ratio corresponding to the indicated position, and is then passed through the resistors 16e and 16d, respectively, and then from the switch 1yb to the resistor 1s. It forms a looper through which it flows. The values of the currents flowing in this way are detected as voltages generated across the resistors J#m and J6d' by the amplifiers 23a and 23b, respectively.

Further, the potential generated in the resistor 18 due to the current flowing through such a router is applied to the amplifier 22 of the power supply section 19.
has been returned to. As a result, the amplifier 22 outputs a constant current while changing the output voltage by the voltage rating effect. The comparator 25 inputs a predetermined voltage obtained by dividing the reference voltage 26 by a resistor 27 as a threshold value, and compares this threshold value with the output voltage level of the power supply section 19. , when the output voltage level of the power supply section 19 becomes higher than the dark value, taple with the indicator pen.

It is detected that there is a suppression of the position specification of the point 11, that is, a pen-on.
f resistance plate 14 is short-circuited. As a result, a current change corresponding to the resistance change of the pressure-sensitive sheet 12 occurs in the current ruler, and the output voltage increases. Therefore, when the output voltage of the power supply section 19 becomes higher than the above-mentioned dark value, the position is correctly designated by the instruction input, and the pressure-sensitive sheet 12
It becomes possible to detect that a predetermined pressure is being applied to. Therefore, detecting pen-on from the output of the comparator 25 and detecting the coordinates of the indicated position from the outputs of the amplifiers 33h and 21b at this time results in a large force.

Note that the coordinates of this designated position are given as a horizontal (X) direction coordinate position and a Wt (Y) direction coordinate position with respect to the surface of the resistance plate 14, respectively.

FIG. 3 shows an electrical equivalent circuit of the position detection system of this device, and shows an example in which the switch 17m is turned on to detect the Y-direction coordinate position. Similarly, the variable resistor 12a in the figure corresponds to the pressure sensitive seat 1211C, and its resistance value is variably set depending on the applied pressure. Applying the pressure described above corresponds to lowering the resistance value of the variable resistor 12a. Further, the variable resistor 14a corresponds to the resistance plate 14, and its sliding contact corresponds to the pressure impression position of the tablet 11, that is, the indicated position.

Therefore, the amplifier 22 of the power supply section 19 compares the terminal voltage Vt of the #Me resistor 18 with the reference voltage, and calculates the voltage v11.
The output voltage main v1 is controlled so that the voltage is constant. This output voltage v1 changes depending on the pressure i applied to the pressure sensitive sheet 12. However, if the amount of pressure applied to the pressure-sensitive sheet 12 is small, the amplifier 22 will be saturated, so that it is impossible for the output voltage vll to rise above the power supply voltage of the linewidth amplifier 2. Therefore, when the pressure-sensitive sheet 12 is pressed, the output voltage v1 changes with respect to the pressure as shown in FIG. 4. Further, in response to such a change in the output voltage, the terminal voltage vs of the resistor 18 also changes as shown in FIG. 4, and is controlled by -electrification. Therefore, by detecting the change in the voltage v1 and comparing it with, for example, a predetermined darkness value Pon, it is possible to accurately detect pen-on.

Furthermore, in a state where the voltages vl and vl are made constant in this way, the voltage is 11Kt! 1=41+<1+
A constant current of 4 is supplied. Then, this constant current is shunted into a current 41 and iH corresponding to the resistance ratio rlerl at the indicated points that divide the resistor plate 14, and then flows through the resistor 16b.

After passing through 16m, they are reunited again. Therefore, the above current i
1 or i from the voltages generated across the resistors 16m and 16b, the resistance values rl' and rl are determined from the correspondence relationship, and furthermore, this resistance value r1*rl
It becomes possible to obtain the indicated position coordinates from

To obtain the coordinate position in the X direction, press the switch J7.
It is sufficient to turn on the switch Irb instead of m and perform step 1. In this case as well, the equivalent circuit is shown in exactly the same way.

As described above, according to the present device, the value of the current flowing out from each electrode provided around the resistive plate 140 of the tablet 11 supplied with a constant xi at a diversion ratio corresponding to the indicated position is directly detected. Since the coordinates of the indicated position are determined, the measurement accuracy is very high.Moreover, the resistor 18 (used for detecting on-on) serves to lower the impedance of the conductive film 13 of the tablet 1. However, since the tablet 11 exhibits a position detection function by being supplied with a constant current, the resistor 18 does not adversely affect the accuracy of the control. Therefore, unlike the conventional device, there is no problem such as 0N10FF control of the connection of the resistor 18, and the control system can be simplified. Therefore, it is possible to simplify the scale of the device configuration, and it has great effects such as being able to perform highly reliable and highly accurate position detection, and has many practical advantages. Moreover, the pen-on signal can also be accurately detected without adversely affecting the position detection accuracy.

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, the device may be constructed with the current flowing in the opposite direction. Further, the size of the resistance plate 14, etc. may be determined according to the specifications of the device. In short, the present invention can be implemented with various modifications without departing from its gist.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional device, FIG. 2 is a schematic block diagram showing an embodiment of the present invention, FIG. 3 is an electrical equivalent circuit diagram of the position detection system of the embodiment device, and FIG. The figure is a diagram showing the change in the voltage 1 e vl with respect to the pressing force. 11...Tablet, 12...Pressure sensitive sheet, 13.
... Conductive film, 14... Resistance plate, 15a to 15d...
Electrode, 16a to J6d...Resistance, IF
m, 17 b - switch, IIJ, 24...
Resistor, 19... Power supply section, 23 a, j3 b-
...Amplifier, j 5-...Comparator. Applicant's agent Patent attorney Takeshi Suzue Hikosai Figure 1 Figure 41F2

Claims (1)

[Claims] A pressure-sensitive sheet made of a pressure-sensitive resistor whose resistance value changes depending on applied pressure, a conductive film disposed on one surface of the pressure-sensitive sheet, and a conductive film disposed on the other surface of the pressure-sensitive sheet. a resistive film provided on the resistive film, a number of electrodes provided on the periphery of the resistive film, and a constant current source that supplies a constant current to the conductive film;
A position characterized by comprising: means for determining the position on the pressure-sensitive sheet where pressure is applied from the value of current flowing from the pressure-sensitive sheet of the constant current from each of the electrodes through the resistive film. Detection device.