JP2018041399A - Self-capacitance type touch sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a touch sensor capable of detecting conductive foreign matter with a simple configuration detecting a self-capacitance.SOLUTION: A self-capacitance type touch sensor includes: an X electrode 102 which is a first electrode in which a plurality of electrodes are arranged; a Y electrode 104 which is a second electrode in which a plurality of electrodes are arranged in a direction crossing the X electrode 102; and a control part 200 which calculates a mutual capacitance between the X electrode 102 and the Y electrode 104 on the basis of the self-capacitance detected by electrostatic capacitance detection parts (an X electrostatic capacitance detection part and a Y electrostatic capacitance detection part) which detect the self-capacitance by the drive of the X electrode 102 and the Y electrode 104, an X switching part which is a first switching part for arbitrarily switching a connection state between the X electrode 102 and the X electrostatic capacitance detection part, and a Y switching part which is a second switching part for arbitrarily switching the connection state between the Y electrode 104 and the Y electrostatic capacitance detection part, to detect a touch state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a self-capacitance touch sensor.

  As a conventional technique, a touch panel device capable of preventing malfunction due to water droplets is known. The touch panel device includes an electrostatic capacitive touch panel having a plurality of transmission-side electrodes and a reception-side electrode, a detection unit that detects contact with the electrostatic touch panel and outputs contact information, and a plurality of transmissions based on the contact information. A detection signal change amount calculation unit that calculates and outputs a detection signal change amount of each of the side electrode and the reception side electrode, and a change amount distribution calculation unit that calculates and outputs a change distribution of the detection signal based on the detection signal change amount; And a determination unit that determines that the contact with the electrostatic touch panel is a water droplet when the peak value of the change amount distribution of the detection signal is equal to or less than a negative threshold (see, for example, Patent Document 1).

  According to this touch panel device, the variation distribution of the detection signal is stored at a predetermined sampling period, the peak value of the variation distribution of the detection signal is equal to or less than a negative threshold, and the peak value of the variation distribution of the detection signal When the peak value of the change distribution of the detection signal in the peripheral area of the area on the electrostatic touch panel where the threshold value is less than or equal to the negative threshold value is greater than or equal to the positive threshold value (first predetermined positive threshold value), contact with the electrostatic touch panel Finally, even if the peak value of the variation distribution of the detection signal is equal to or greater than a positive threshold value (a value exceeding the first predetermined positive threshold value) greater than the positive threshold value. Since the coordinate value to be output is determined to be invalid, it is possible to prevent erroneous determination as a finger / pen even if the finger / pen is placed in water in contact with the electrostatic touch panel. That is, when a finger / pen is put in the water, it may be determined that the finger is a large finger. Therefore, it is possible to prevent erroneous determination by examining whether water has been present in the past at the location. Even if the distribution of the change amount of the detection signal becomes one large peak of “+” and the positive peak value is equal to or larger than the second predetermined positive threshold value, the coordinate value to be finally output is Invalid. Thereby, it is supposed that the malfunctioning by a water droplet can be prevented.

JP 2012-88899 A

  However, since the conventional touch sensor described above has a configuration including a mutual capacitance type electrostatic detection circuit, there is a problem that the circuit becomes complicated.

  Accordingly, an object of the present invention is to provide a touch sensor capable of detecting conductive foreign substances with a simple configuration for detecting self-capacitance.

[1] In order to achieve the above object, the present invention provides a first electrode in which a plurality of electrodes are arranged, a second electrode in which a plurality of electrodes are arranged in a direction intersecting the first electrode, and the first electrode And a capacitance detection unit that detects self-capacitance by driving the second electrode, a first switching unit that arbitrarily switches a connection state between the first electrode and the capacitance detection unit, and the second electrode A second switching unit that arbitrarily switches the connection state with the capacitance detection unit, the capacitance detection unit, the first switching unit, and the second switching unit are controlled and detected by the capacitance detection unit A self-capacitance touch sensor comprising: a controller that calculates a mutual capacitance between the first electrode and the second electrode based on the measured self-capacitance and detects a touch state based on the calculated mutual capacitance. provide.

[2] The control unit controls the first switching unit to sequentially switch the connection state between the first electrode and the capacitance detection unit, and controls the second switching unit to control the second electrode. The self according to [1], wherein the touch position is detected by sequentially switching the connection state with the capacitance detection unit and detecting the self-capacitance of the first electrode and the second electrode. A capacitive touch sensor may be used.

[3] In addition, when there are a plurality of detected touch positions, the control unit simultaneously drives the first electrode and the second electrode corresponding to the plurality of touch positions, and the driven first electrode and The touch state is detected by detecting a self-capacitance of a node at which the second electrode intersects, and determining whether the mutual capacitance calculated based on the detected self-capacitance is a positive value or a negative value with respect to a reference value. The self-capacitance touch sensor according to the above [1] or [2], characterized in that it is determined whether it is caused by a finger or a conductive foreign matter.

[4] Further, according to any one of [1] to [3], the first electrode and the second electrode are connected to a ground when the driving is not performed by the control unit. The self-capacitance type touch sensor may be used.

  ADVANTAGE OF THE INVENTION According to this invention, the touch sensor which can detect a conductive foreign material with the simple structure which detects a self-capacitance can be provided.

FIG. 1 is a block diagram showing a schematic configuration and signal transmission of a self-capacitance touch sensor according to an embodiment of the present invention. 2A is a detailed diagram illustrating a configuration example of the X switching unit, and FIG. 2B is a detailed diagram illustrating a configuration example of the Y switching unit. FIG. 3 shows a state where water droplets are attached to the touch sensor, and is a diagram showing a self-capacitance distribution of each X and Y electrode. FIG. 4 is a table showing a difference in polarity of mutual capacitance values when a finger or a water droplet adheres to the touch sensor. FIG. 5 is a diagram specifically illustrating a connection state of the X electrode, the Y electrode, the X switching unit, and the Y switching unit when water droplets are attached to the touch sensor. FIG. 6 is a model diagram of a four-conductor system for explaining the principle of the self-capacitance touch sensor according to the present embodiment.

(Embodiment of the present invention)
FIG. 1 is a block diagram showing a schematic configuration and signal transmission of a self-capacitance touch sensor according to an embodiment of the present invention.

A self-capacitance touch sensor 1 according to an embodiment of the present invention includes an X electrode 102 (X ₁ , X ₂ ,..., X _m ) that is a first electrode on which a plurality of electrodes are arranged, A Y electrode 104 (Y ₁ , Y ₂ ,..., Y _n ) that is a second electrode in which a plurality of electrodes are arranged in the intersecting direction, and a static capacitance that detects self-capacitance by driving the X electrode 102 and the Y electrode 104. X switching which is a first switching unit that arbitrarily switches the connection state between the capacitance detection unit (X capacitance detection unit 152, Y capacitance detection unit 172) and the X electrode 102 and the X capacitance detection unit 152. Unit 154, a Y switching unit 174 that is a second switching unit that arbitrarily switches the connection state between the Y electrode 104 and the Y capacitance detection unit 172, and a capacitance detection unit (X capacitance detection unit 152, Y Capacitance detection unit 172), X switching 154 and the Y switching unit 174, and based on the self-capacitance detected by the capacitance detection unit (X capacitance detection unit 152, Y capacitance detection unit 172), And a control unit 200 that detects a touch state based on the calculated mutual capacitance.

(Configuration of touch electrode unit 100)
As shown in FIG. 1, the touch electrode unit 100 has an X electrode 102 (X ₁ , X ₂ ,..., X _m ) and a Y electrode 104 (Y ₁ , Y ₂ ,..., Y _n ) orthogonal to each other. Is formed. The operator can perform touch input by one-point touch (single touch) or multi-point touch (multi-touch) by touching the touch electrode unit 100. As shown in FIG. 1, the touch electrode unit 100 is set with operation input reference coordinates (X, Y) with the upper left as the origin, the X axis in the right direction and the Y axis in the lower direction. With this touch input, it is possible to operate a connected operation target device (for example, an in-vehicle device).

  The X electrode 102 and the Y electrode 104 are configured as electrodes using, for example, ITO (tin-doped indium oxide), copper, or the like. The X electrode 102 and the Y electrode 104 are arranged so as to cross each other while being insulated from each other. In the present embodiment, the X electrode 102 and the Y electrode 104 are arranged orthogonally.

(Configuration of X drive detection unit 150)
As shown in FIG. 1, an X drive detection unit 150 is connected to one end side of the X electrode 102. Here, FIG. 2A is a detailed diagram illustrating a configuration example of the X switching unit.

As illustrated in FIG. 2A, the X drive detection unit 150 includes an X capacitance detection unit 152 and an X switching unit 154. The X capacitance detection unit 152 is controlled by the X drive detection signal S _Xi output from the control unit 200 shown in FIG. 1 to supply electric charges to the X electrode 102, and is also self- _generated by the capacitance signal S _CXi. Capacitance detection is performed. The detected self-capacitance is output to the control unit 200 as a capacitance count value S _{DXi obtained} by _{subjecting the} capacitance signal S _CXi to analog / digital conversion processing or the like. The X switching unit 154 is controlled by the X switching signal _SWXi, and performs an operation of switching the connection between an arbitrary X electrode 102 and the X capacitance detecting unit 152.

The X switching unit 154 includes, for example, a switching element such as a transistor, and one X electrode 102 and the X capacitance detecting unit 152 can be switched through the switching element. As shown in FIG. 2 (a), for example, the i-th X electrode (X _i ) has an X capacitance detection unit during driving for performing the above-described charge supply and capacitance (self-capacitance) detection. 152 is connected. On the other hand, the i-th X electrode (X _i ) is connected to the ground GND when not driven. The connection switching between the X electrode 102 and the X capacitance detection unit 152 can be performed in any X electrode. Therefore, the connection between the X electrode 102 and the X capacitance detection unit 152 can be switched sequentially, or only an arbitrary X electrode 102 and the X capacitance detection unit 152 can be connected.

(Configuration of Y Drive Detection Unit 170)
As shown in FIG. 1, a Y drive detection unit 170 is connected to one end side of the Y electrode 104. Here, FIG. 2B is a detailed diagram illustrating a configuration example of the Y switching unit.

As shown in FIG. 2B, the Y drive detection unit 170 includes a Y capacitance detection unit 172 and a Y switching unit 174. The Y capacitance detection unit 172 is controlled by the Y drive detection signal S _Yi output from the control unit 200 shown in FIG. 1 to supply electric charge to the Y electrode 104, and is self- _generated by the capacitance signal S _CYi. Capacitance detection is performed. The detected self-capacitance is output to the control unit 200 as a capacitance count value S _{DYi obtained} by _{subjecting the} capacitance signal S _CYi to analog / digital conversion processing or the like. The Y switching unit 174 is controlled by the Y switching signal _SWYi, and performs an operation of switching the connection between the arbitrary Y electrode 104 and the Y capacitance detecting unit 172.

The Y switching unit 174 is constituted by, for example, a switching element such as a transistor, and one Y electrode 104 and the Y capacitance detecting unit 172 can be switched in connection via the switching element. As shown in FIG. 2B, for example, the j-th Y electrode (Y _i ) has a Y electrostatic capacity detection unit during driving for performing the above-described charge supply and electrostatic capacity (self-capacitance) detection. 172. On the other hand, the j-th Y electrode (Y _i ) is connected to the ground GND when not driven. The connection switching between the Y electrode 104 and the Y capacitance detection unit 172 can be performed in any Y electrode. Therefore, the connection between the Y electrode 104 and the Y capacitance detection unit 172 can be switched sequentially, or only the arbitrary Y electrode 104 and the Y capacitance detection unit 172 can be connected.

(Configuration of control unit 200)
The control unit 200 includes, for example, a CPU (Central Processing Unit) that performs calculation and processing on acquired data according to a stored program, a RAM (Random Access Memory) that is a semiconductor memory, a ROM (Read Only Memory), and the like. Microcomputer. In this ROM, for example, a program for operating the control unit 200 is stored. For example, the RAM is used as a storage area for temporarily storing calculation results and the like. The control unit 200 has a means for generating a clock signal therein, and operates based on the clock signal.

(Operation of the self-capacitance touch sensor 1 according to the present embodiment)
(Detection of normal operation (single touch))
In the self-capacitance touch sensor 1 according to the present embodiment, as a normal operation, the X electrodes 102 are sequentially switched by the X switching signal _SWXi and connected to the X capacitance detection unit 152, and each X electrode 102 is _subjected to the self-capacitance method. _Is obtained as a capacitance count value S _DXi . The X electrode 102 that is not connected to the X capacitance detection unit 152 is connected to the ground GND.

Similarly, the Y electrodes 104 are sequentially switched by the Y switching signal _SWYi and connected to the Y capacitance detection unit 172, and the capacitance value of each Y electrode 104 is acquired as the capacitance count value S _DYi by the self-capacitance method. To do. The Y electrode 104 that is not connected to the Y capacitance detection unit 172 is connected to the ground GND.

  The control unit 200 determines that a touch operation has been performed on each of the X electrode 102 and the Y electrode 104 when the capacitances of the X electrode 102 and the Y electrode 104 change beyond a predetermined reference value. When at least one of the X electrode 102 and the Y electrode 104 changes beyond a predetermined reference value, a single touch (one point touch) can be determined. In such a case, the control unit 200 determines that the touch is a single touch and can determine the touch position by the finger.

(Detection of conductive foreign matter (water droplets))
FIG. 3 is a diagram illustrating a state in which water droplets are attached to the touch sensor and a distribution of capacitance detected by the mutual capacitance formula in the X and Y coordinates. FIG. 4 is a table showing the difference in polarity of the mutual capacitance value when a finger or a water droplet adheres to the touch sensor.

  Here, referring to FIG. 4, when the capacitance is detected by the mutual capacitance, the mutual capacitance value becomes a mass when a finger is detected, and the mutual capacitance value becomes a positive when a water droplet is detected. Note that the plus and mimas values are changes relative to the mutual capacitance reference value (value at the time of non-touch).

  Therefore, as shown in FIG. 3, when the region for detecting the capacitance extends over a plurality of electrodes, if the mutual capacitance value between each X electrode and Y electrode is detected and its polarity is examined, detection of the touch state, that is, It is possible to determine whether the touched object is a finger or a water droplet (conductive foreign matter).

As shown in Figure _3, it will be described operation of detecting if _{X i-1 ~X i ~X i} + 1, Y j-1 ~Y j ~Y j + water droplets 350 to _first region is attached.

Control unit 200, in the _{X i-1 to X} shown _{i ~X i + 1, Y j} -1 ~Y j ~Y j + 1 of each coordinate of the combination (9 points), the self-capacitance by simultaneous driving The mutual capacitance value is calculated based on the detected self-capacitance.

Here, a case where the self-capacitance is detected for (X _i , Y _j ) will be described as a representative example of nine points. First, in order to detect the self-capacitance for (X _i , Y _j ), the X electrode (X _i ) and the X capacitance detection unit 152 are connected by the X switching unit 154 as shown in FIG. The X electrode is connected to the ground GND. Further, all Y electrodes are connected to the ground GND by the Y switching unit 174. In this state, the self-capacitance C _i ^Self is detected when only the X electrode (X _i ) is driven.

Further, the Y switching unit 174 connects the Y electrode (Y _j ) and the Y electrostatic capacitance detection unit 172, and the other Y electrode is connected to the ground GND. Further, all X electrodes are connected to the ground GND by the X switching unit 154. In this state, the self-capacitance C _j ^Self when only the Y electrode (Y _j ) is driven is detected.

を検出する。なお、Ｘ_ｉ、Ｙ_ｊ以外の電極はすべてグランドＧＮＤに接続する。 Further, the X electrode (X _i ) and the X capacitance detection unit 152 are connected, and the Y electrode (Y _j ) and the Y capacitance detection unit 172 are connected. In this state, that is, the X electrode (X _i ) And the Y electrode (Y _j ) in combination, the X capacitance detection unit 152 and the Y capacitance detection unit 172 simultaneously drive the self capacitance at the time of simultaneous drive.

Is detected. All electrodes other than X _i and Y _j are connected to the ground GND.

Thereby, the mutual capacitance C _{i, j at} (X _i , Y _j ) can be calculated. The calculation method is shown below.

(Method of acquiring mutual capacitance with a self-capacitance sensor)
(When other conductor (electrode) is dropped to ground GND during detection)
FIG. 6 is a four-conductor analysis model diagram for explaining the principle of the self-capacitance touch sensor according to the present embodiment. As an example, consider a four-conductor system as shown in FIG. One of the four conductors was GND. C _i represents the capacitance of the conductor i to infinity, and C _ij represents the capacitance of the conductor i and the conductor j.

Here, conductors are GND is sufficiently large capacitance C _G of the normal infinity, it may be considered that C _G are short-circuited.

  In general, in a capacitive sensor having a plurality of detection channels and sequentially acquiring the capacity of each channel, in order to avoid the influence of conductors connected to channels that are not being driven (detecting), control is performed to drop these conductors to GND. To do.

同様に、

また、導体１と導体２を同時に駆動する場合、これらの導体の（合成）自己容量は、

となる。
したがって、以下の式により、自己容量を求めることにより、導体１と導体２の間の容量（相互容量）が算出、取得できる。

この結果は、導体数が増加しても同様に成り立つ。 Under this control, the self-capacitance (capacitance with GND) of the conductor 1 detected by this sensor is expressed by the following equation.

Similarly,

Also, when the conductor 1 and the conductor 2 are driven simultaneously, the (composite) self-capacitance of these conductors is

It becomes.
Therefore, the capacitance (mutual capacitance) between the conductor 1 and the conductor 2 can be calculated and obtained by obtaining the self-capacitance by the following equation.

This result holds true even if the number of conductors increases.

(Effect of the embodiment of the present invention)
The present embodiment has the following effects.
(1) The self-capacitance touch sensor 1 according to the present embodiment includes an X electrode 102 (X ₁ , X ₂ ,..., X _m ) that is a first electrode on which a plurality of electrodes are arranged, and an X electrode 102. The self-capacitance is detected by driving the Y electrode 104 (Y ₁ , Y ₂ ,..., Y _n ), which is a second electrode in which a plurality of electrodes are arranged in a direction intersecting with the X electrode 102, and the X electrode 102 and the Y electrode 104. X, which is a first switching unit that arbitrarily switches the connection state between the X capacitance 102 and the X capacitance detection unit 152 (X capacitance detection unit 152, Y capacitance detection unit 172). The switching unit 154, a Y switching unit 174 that is a second switching unit that arbitrarily switches the connection state between the Y electrode 104 and the Y capacitance detection unit 172, and a capacitance detection unit (X capacitance detection unit 152, Y capacitance detector 172), X switching 154 and the Y switching unit 174, and based on the self-capacitance detected by the capacitance detection unit (X capacitance detection unit 152, Y capacitance detection unit 172), And a control unit 200 that detects a touch state based on the calculated mutual capacitance. Therefore, it is possible to detect the self-capacitance by simultaneously driving the arbitrary X electrode 102 and the arbitrary Y electrode 104. Thereby, it is possible to detect a conductive foreign substance with a simple configuration for detecting self-capacitance, and for example, it is possible to determine whether a finger touch or a water droplet adheres.
(2) The self-capacitance touch sensor 1 according to the present embodiment has only a self-capacitance detection unit as a capacitance detection unit. Therefore, since it is not necessary to provide mutual capacitance type detection means as in the prior art, it is possible to cope with multi-touch with a simple configuration.
(3) Since the conductive foreign matter is detected by detecting the self-capacitance, it is possible to perform detection while maintaining the high sensitivity and high speed, which are the advantages of the self-capacitance sensor.

  Although the embodiment of the present invention has been described above, this embodiment is merely an example, and does not limit the invention according to the claims. In addition, the novel embodiment can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the gist of the present invention. In addition, not all the combinations of features described in this embodiment are essential to the means for solving the problems of the invention. Further, this embodiment is included in the scope and gist of the invention, and is included in the invention described in the claims and the equivalent scope thereof.

DESCRIPTION OF SYMBOLS 1 ... Self-capacitance type touch sensor 100 ... Touch electrode part 102 ... X electrode 104 ... Y electrode 150 ... X drive detection part 152 ... X electrostatic capacitance detection part 154 ... X switching part 170 ... Y drive detection part 172 ... Y electric capacity Detection unit 174 ... Y switching unit 200 ... Control unit 350 ... Water drop GND ... Ground S _CXi , S _CYi ... Capacitance signal S _DXi , S _DYi ... Capacitance count value S _WXi ... X switching signal S _WYi ... Y switching signal S _Xi ... X drive detection signal S _Yi ... Y drive detection signal

Claims (4)

A first electrode having a plurality of electrodes disposed thereon;
A second electrode having a plurality of electrodes arranged in a direction intersecting the first electrode;
A capacitance detector that detects self-capacitance by driving the first electrode and the second electrode;
A first switching unit that arbitrarily switches a connection state between the first electrode and the capacitance detection unit;
A second switching unit that arbitrarily switches a connection state between the second electrode and the capacitance detection unit;
The mutual capacitance between the first electrode and the second electrode is controlled based on the self-capacitance detected by the capacitance detection unit by controlling the capacitance detection unit, the first switching unit, and the second switching unit. And a control unit that detects a touch state based on the
A self-capacitance touch sensor characterized by comprising:   The control unit controls the first switching unit to sequentially switch the connection state between the first electrode and the capacitance detection unit, and controls the second switching unit to control the second electrode and the electrostatic capacitance. 2. The self-capacitive touch sensor according to claim 1, wherein the touch position is detected by sequentially switching the connection state with the capacitance detection unit and detecting the self-capacitance of the first electrode and the second electrode. .   The control unit simultaneously drives the first electrode and the second electrode corresponding to the plurality of touch positions when there are a plurality of detected touch positions, and the driven first electrode and the second electrode intersect with each other. Detecting the self-capacitance of the node to be detected, and determining whether the mutual capacitance calculated based on the detected self-capacitance is a positive value or a negative value with respect to a reference value. The self-capacitance touch sensor according to claim 1, wherein it is determined whether it is due to a sexual foreign matter.   4. The self-capacitive touch sensor according to claim 1, wherein the first electrode and the second electrode are connected to a ground when the driving is not performed by the control unit. 5.

Images