JP2018101281A - Touch detection device - Google Patents

Abstract

A touch detection device capable of ensuring detection accuracy of touch determination is provided. A controller (16) switches a measurement circuit to an additional circuit (14) by not applying a voltage to a sensor electrode (4) when adjusting a threshold CON-OFF. At this time, the controller 16 detects the electrostatic capacitance Cs(t) of the shield electrode 9 magnetically shielded from the sensor electrode 4 by the shield electrode measurement control unit 15, and based on the detected value, the threshold value CON for operation determination. - Adjust OFF (touch determination threshold CON and non-touch determination threshold COFF). [Selection drawing] Fig. 1

Description

  The present invention relates to a touch detection device that detects a touch operation.

As shown in FIGS. 6 and 7, the capacitive touch detection device (touch sensor) measures a capacitance C (t) that changes due to a touch operation, and the value is a predetermined touch determination threshold C _ON. When it becomes above, it determines with there being touch operation. However, the capacitance C (t) may increase or decrease due to factors other than the touch operation, which may cause malfunction. One cause of malfunction is, for example, temperature and humidity fluctuations in the surrounding environment.

As shown in FIG. 6, for example, when the temperature and humidity increase during determination of the touch operation state, when switching to the non-touch operation, the capacitance C (t) does not become the non-touch determination threshold C _OFF or less, and the touch operation A situation occurs in which the determination of the state is maintained. In addition, as shown in FIG. 7, for example, when the temperature and humidity decrease during determination of the touch operation state, the capacitance C (t) is not touched during the operation, even though the touch state is taken. There is a situation in which the state is switched to the non-touch determination state because it becomes less than _OFF .

Therefore, Patent Document 1 discloses a technique for dealing with the above problems. This patent document 1 estimates a temperature / humidity variation from the variation of the capacitance C (t) during the determination of the presence of a touch operation, and determines that the temperature / humidity variation has occurred, the non-touch determination threshold value C _OFF is set to a different value. By switching, it is a technique to ensure correct non-touch determination.

Japanese Patent Laying-Open No. 2015-11558

  Patent Document 1 is a technique for distinguishing between touch / non-touch operations and temperature / humidity fluctuations based on the increment per unit time of the capacitance C (t). For this reason, for example, when the touch state is continued for a long time by bringing a conductor (such as a finger) into contact with the touch operation unit, the pressed state of the conductor fluctuates (for example, the finger close to the sensor electrode swings). There is a problem that this fluctuation cannot be distinguished from temperature and humidity fluctuations.

  The objective of this invention is providing the touch detection apparatus which can ensure the detection precision of a touch determination.

  The touch detection device that solves the above problem includes a cancel mechanism that reduces the parasitic capacitance of the sensor electrode by applying the same voltage as the sensor electrode to a shield electrode that is disposed opposite to the sensor electrode. A shield electrode measurement control unit capable of detecting a capacitance of the shield electrode, and only the shield electrode is operated by not applying a voltage to the sensor electrode, and the capacitance of the shield electrode under this state is determined by the shield. And a controller that adjusts a threshold value for operation determination based on the capacitance by measuring with the electrode measurement control unit.

  According to this configuration, when no voltage is applied to the sensor electrode, the shield electrode is electromagnetically shielded from the sensor electrode. For this reason, the shield electrode is not affected by the touch operation on the sensor electrode side, and outputs a capacitance according to the surrounding environment. In this configuration, the capacitance of the shield electrode at this time is measured by the shield electrode measurement control unit, and the threshold value for the operation determination is adjusted based on the measured value. Changed to Therefore, it is possible to ensure the detection accuracy of touch determination.

  In the touch detection device, it is preferable that the controller executes a process of adjusting the threshold based on a capacitance of the shield electrode at regular intervals. According to this configuration, the threshold value is set to a suitable value each time, which contributes to ensuring the detection accuracy of touch determination.

  In the touch detection device, the threshold value is a non-touch determination threshold value used to determine whether or not an operation on the sensor electrode is a non-touch operation, and the controller is configured to determine whether the operation is in a touch operation state. It is preferable that the determination is not switched to the non-touch determination during the touch determination by adjusting the non-touch determination threshold. According to this configuration, even when the capacitance of the sensor electrode changes under the influence of the surrounding environment, the determination is unintentionally switched to the non-touch determination during the user's touch operation. It is possible to make the situation difficult to occur.

  In the touch detection device, the controller outputs an output of the shield electrode without applying a voltage to the sensor electrode, both during the determination that the state is the non-touch operation state and the determination that the state is the touch operation state. It is preferable to adjust the touch determination threshold and the non-touch determination threshold by the same process of checking and adjusting the threshold. According to this configuration, there is no need to prepare different determination logics for the adjustment of the touch determination threshold and the adjustment of the non-touch determination threshold, which is advantageous for simplification of processing and configuration.

  In the touch detection device, it is preferable that the sensor electrode and the shield electrode are formed in the same area. According to this configuration, one of the parasitic capacitance that can occur in the sensor electrode at the time of the operation determination and the parasitic capacitance that can occur in the shield electrode at the time of the threshold adjustment processing may be generated with a large deviation from the other. Absent. Therefore, it is advantageous to satisfy both the determination accuracy of the operation determination and the accuracy of the threshold adjustment.

  According to the present invention, the detection accuracy of touch determination can be ensured.

The block diagram of the touch detection apparatus of one Embodiment. The operation | movement figure of the additional circuit of threshold value adjustment. (A) is an output waveform diagram of the sensor electrode when the temperature and humidity are increased, and (b) is an output waveform diagram of the shield electrode when the temperature and humidity are increased. (A) is an output waveform diagram of the sensor electrode when the temperature and humidity are lowered, and (b) is an output waveform diagram of the shield electrode when the temperature and humidity are lowered. The perspective view of the electrode group which shows the magnitude | size of a sensor electrode and a shield electrode. The output waveform figure of the sensor electrode in the conventional touch detection apparatus. Similarly, the output waveform figure of the sensor electrode in a touch detection apparatus.

Hereinafter, an embodiment of the touch detection device will be described with reference to FIGS.
As shown in FIG. 1, the capacitive touch detection device 1 includes a touch detection circuit 3 that detects a touch operation of a human body or the like on the touch operation unit 2. The touch detection circuit 3 of this example includes a sensor electrode 4 that detects a touch operation of the touch operation unit 2, and a sensor electrode measurement control unit 5 that determines the touch operation by measuring the capacitance C (t) of the sensor electrode 4. With. The touch operation unit 2 is, for example, a touch panel. The sensor electrode 4 includes an electrode group disposed in a dot shape over the entire back surface of the touch operation unit 2.

  When the touch operation unit 2 is touched, the capacitance C (t) of the sensor electrode 4 of the operation part changes. The sensor electrode measurement control unit 5 measures the change in the capacitance C (t) and executes touch determination, non-touch determination, and the like.

  The touch detection device 1 (touch detection circuit 3) includes a cancel mechanism 8 that reduces the parasitic capacitance generated in the sensor electrode 4 and ensures the accuracy of touch detection. The cancel mechanism 8 includes a shield electrode 9 disposed opposite to the sensor electrode 4, an insulator 10 disposed between the sensor electrode 4 and the shield electrode 9, and a shield electrode drive circuit 11 that drives the shield electrode 9. . The sensor electrode measurement control unit 5 applies the same voltage as the voltage applied to the sensor electrode 4 to the shield electrode 9 through the shield electrode drive circuit 11, whereby the sensor electrode 4 and the GND surface (for example, a casing) are connected. Parasitic capacitance generated between them is not included in the capacitance C (t) of the sensor electrode 4. Thereby, a high S / N ratio with a capacitance C (t) is ensured.

The touch detection device 1 includes a correction function (additional circuit 14) that suppresses the influence of the surrounding environment of the touch detection device 1 and ensures the detection accuracy of the touch operation. Correction function of the present embodiment is also a touch detecting device 1 of the surrounding environment (e.g., temperature and humidity) is varied, so as not switched unintentionally touch determination condition, the threshold C _ON-OFF operation determination (e.g. The touch determination threshold value C _ON and the non-touch determination threshold value C _OFF ) are adjusted according to the surrounding environment.

In this case, the touch detection device 1 (additional circuit 14) includes a shield electrode measurement control unit 15 that can detect the electrostatic capacitance Cs (t) of the shield electrode 9, and a controller 16 that controls the operation of threshold adjustment. The controller 16 is connected to the sensor electrode measurement control unit 5, the shield electrode drive circuit 11, and the shield electrode measurement control unit 15. The controller 16 operates only the shield electrode 9 by not applying a voltage to the sensor electrode 4, and the shield electrode measurement controller 15 measures the electrostatic capacitance Cs (t) of the shield electrode 9 under this state. The threshold value C _ON-OFF for operation determination is adjusted based on the electrostatic capacitance Cs (t). The controller 16 executes processing for adjusting the threshold value C _ON-OFF based on the electrostatic capacitance Cs (t) of the shield electrode 9 at regular intervals.

Next, operations and effects of the touch detection device 1 according to the embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the sensor electrode measurement controller 5 monitors the capacitance C (t) output from the sensor electrode 4 during the operation determination period, and the capacitance C (t) and the operation The touch operation is determined by comparing the predetermined threshold value C _ON-OFF (touch determination threshold value C _ON and non-touch determination threshold value C _OFF ). Specifically, when the capacitance C (t) is equal to or greater than the touch determination threshold value C _ON under the determination of the non-touch operation state, the touch determination state is established, and the capacitance C (t) is determined under the determination of the touch operation state. When the non-touch determination threshold value C _OFF or less, the non-touch determination state is entered.

When the touch operation is under determination, the determination state during the touch operation is maintained unless the capacitance C (t) is equal to or less than the non-touch determination threshold C _OFF . If the capacitance C (t) falls below the non-touch determination threshold value C _OFF even once under the determination during the touch operation, the touch operation is performed unless the capacitance C (t) exceeds the touch determination threshold value C _ON again. It does not shift to the middle judgment.

  The sensor electrode measurement control unit 5 applies the same voltage as the voltage applied to the sensor electrode 4 to the shield electrode 9 through the shield electrode drive circuit 11 during the operation determination period. Thereby, the parasitic capacitance generated between the sensor electrode 4 and the GND surface is canceled, and an S / N having a high electrostatic capacitance C (t) is secured.

  As shown in FIG. 2, the controller 16 confirms fluctuations in the surrounding environment (in this example, temperature and humidity) at regular intervals. In the case of this example, the controller 16 switches the measurement circuit that measures the electrodes from the touch detection circuit 3 that detects the presence or absence of a touch operation to the additional circuit 14 that performs threshold adjustment according to the surrounding environment at regular intervals. The fixed period is preferably set to a predetermined timing at which, for example, temperature and humidity are to be measured.

  In switching the measurement circuit for electrode measurement to the additional circuit 14, first, the controller 16 invalidates the touch detection circuit 3 by not applying a voltage to the sensor electrode 4 and the shield electrode drive circuit 11. At this time, the sensor electrode 4 is grounded, and the shield electrode drive circuit 11 stops functioning. When the measurement circuit for electrode measurement is switched to the additional circuit 14, the shield electrode 9 is electromagnetically shielded by the grounded sensor electrode 4, so that the capacitance Cs (t) of the shield electrode 9 is The touch operation is not affected. However, although it cannot actually be completely shielded, it can be shielded to such an extent that the influence of the touch operation can be ignored.

  The shield electrode measurement control unit 15 measures the capacitance Cs (t) of the shield electrode 9 when the measurement circuit becomes the additional circuit 14 and outputs the measured value to the controller 16. The controller 16 determines the fluctuation of the surrounding environment (temperature and humidity) based on the electrostatic capacitance Cs (t) of the shield electrode 9.

Here, FIGS. 3 (a) and 3 (b) show respective waveform change diagrams of the capacitances C (t) and Cs (t) when the temperature and humidity rise during the determination of the touch operation state. Show. As can be seen from the figure, when the temperature and humidity increase during determination of the touch operation state, both the capacitances C (t) and Cs (t) increase. Controller 16, when processing of the threshold adjustment, the correction amount α corresponding to the change amount of the electrostatic capacitance Cs (t) of the shield electrode 9 is added to the non-touch determination threshold C _OFF, adjust the non-touch determination threshold C _OFF To do. Thereby, when the user's operation is in a non-touch state, the capacitance C (t) of the sensor electrode 4 falls below the non-touch determination threshold C _OFF without any problem.

Also, FIGS. 4A and 4B show respective waveform change diagrams of the capacitances C (t) and Cs (t) when the temperature and humidity are lowered during the determination that the touch operation state is established. . As can be seen from the figure, when the temperature and humidity decrease during determination of the touch operation state, both the capacitances C (t) and Cs (t) decrease. Controller 16, when processing of the threshold adjustment, the correction amount β in accordance with the change amount of the electrostatic capacitance Cs (t) of the shield electrode 9 is added to the non-touch determination threshold C _OFF, adjust the non-touch determination threshold C _OFF To do. As a result, the capacitance C (t) of the sensor electrode 4 does not fall below the non-touch determination threshold value C _OFF even though the user's operation is in the touch operation.

In the case of this example, when the voltage of the sensor electrode 4 is not applied, the shield electrode 9 is electromagnetically shielded from the sensor electrode 4. For this reason, the shield electrode 9 is not affected by the touch operation on the sensor electrode 4 side, and outputs the capacitance Cs (t) corresponding to the surrounding environment (temperature / humidity fluctuation). In this example, the capacitance Cs (t) of the shield electrode 9 at this time is measured by the shield electrode measurement control unit 15 and the operation determination threshold value C _ON-OFF is adjusted based on the measured value. The threshold value C _ON-OFF is changed to a suitable value according to the surrounding environment. Therefore, the detection accuracy of touch determination can be ensured.

The controller 16 executes processing for adjusting the threshold value C _ON-OFF based on the electrostatic capacitance Cs (t) of the shield electrode 9 at regular intervals. Therefore, the threshold value C _ON-OFF is set to a suitable value each time, which contributes to ensuring detection accuracy of touch determination.

The controller 16 adjusts the non-touch determination threshold value C _OFF during the determination that the touch operation state is set, so that the determination does not switch to the non-touch determination during the touch determination. Therefore, even when the capacitance C (t) of the sensor electrode 4 is affected and changed by the surrounding environment, the determination is unintentionally switched to the non-touch determination during the user's touch operation. It can be made difficult to occur.

The controller 16 confirms the output of the shield electrode 9 without applying a voltage to the sensor electrode 4 during both the determination of the non-touch operation state and the determination of the touch operation state. The touch determination threshold C _ON and the non-touch determination threshold C _OFF are adjusted by the same process of adjusting C _ON-OFF . Therefore, it is not necessary to prepare different determination logics for the adjustment of the touch determination threshold value C _{ON and} the adjustment of the non-touch determination threshold value C _OFF , which is advantageous for simplification of processing and configuration.

As shown in FIG. 5, the sensor electrode 4 and the shield electrode 9 are formed in the same area. By the way, when the touch detection circuit 1 is set to the touch detection circuit 3 and the touch determination is performed from the electrostatic capacitance C (t) of the sensor electrode 4, parasitic capacitance is generated in the sensor electrode 4, and measurement is similarly performed. When the circuit is switched to the additional circuit 14 and the threshold value C _ON-OFF is adjusted, a parasitic capacitance is generated in the shield electrode 9. Here, for example, the area of the shield electrode 9 can be made larger than that of the sensor electrode 4 to suppress the parasitic capacitance of the sensor electrode 4 during the determination operation. However, as a contradiction, the measurement circuit is switched to the additional circuit 14. At this time, a large parasitic capacitance is generated in the shield electrode 9, which hinders accurate adjustment of the threshold value C _ON-OFF .

  Therefore, in the case of this example, since the sensor electrode 4 and the shield electrode 9 are formed in the same area, the parasitic capacitance that can be generated in the sensor electrode 4 at the time of operation determination and the shield electrode 9 can be generated in the process of threshold adjustment. One of the parasitic capacitances is not greatly biased with respect to the other. Therefore, it is advantageous to satisfy both the determination accuracy of the operation determination and the accuracy of the threshold adjustment.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
And adjustment method of the threshold value C _ON-OFF is not limited to the method of the correction amount of one-to-one relationship in accordance with the variation of temperature and humidity as described in Example alpha, beta is added to or subtracted threshold C _ON-OFF. For example, an adjustment method may be used in which the correction amount of the threshold C _ON-OFF is added / subtracted for each temperature / humidity change amount range.

_-The adjustment method of the threshold value C _ON-OFF is not limited to the method in which the correction amounts α, β are added to or subtracted from the threshold value C _ON-OFF . For example, the current threshold value C _ON-OFF is multiplied by a constant. You may change to this method.

The cancel mechanism 8 is not limited to the configuration described in the embodiment, and can be changed to another structure as long as it has a shield electrode.
-It is good also as the touch detection apparatus 1 which adjusts only one of the touch determination threshold value _CON and the non-touch determination threshold value _COFF .

  The touch detection device 1 can be applied to various devices and devices such as a palm rest.

DESCRIPTION OF SYMBOLS 1 ... Touch detection apparatus, 4 ... Sensor electrode, 8 ... Cancel mechanism, 9 ... Shield electrode, 15 ... Shield electrode measurement control part, 16 ... Controller, C (t) ... Electrostatic capacity, Cs (t) ... Electrostatic capacity , C _ON-OFF ... threshold, C _ON ... touch determination threshold, C _OFF ... non-touch determination threshold.

Claims (5)

In the touch detection device including a cancel mechanism that reduces the parasitic capacitance of the sensor electrode by applying the same voltage as the sensor electrode to the shield electrode disposed to face the sensor electrode.
A shield electrode measurement control unit capable of detecting the capacitance of the shield electrode;
Only the shield electrode is operated by not applying a voltage to the sensor electrode, and the electrostatic capacity of the shield electrode under this state is measured by the shield electrode measurement control unit, and based on the electrostatic capacity. A touch detection apparatus comprising: a controller for adjusting a threshold value for operation determination. The touch detection device according to claim 1, wherein the controller executes a process of adjusting the threshold value based on a capacitance of the shield electrode at regular intervals. The threshold value is a non-touch determination threshold value used to determine whether or not the operation on the sensor electrode is a non-touch operation.
The touch detection according to claim 1, wherein the controller is configured to adjust the non-touch determination threshold value during determination that the touch operation state is set, so that the determination is not switched to non-touch determination during touch determination. apparatus. The controller adjusts the threshold value by checking the output of the shield electrode without applying a voltage to the sensor electrode, both during the determination of the non-touch operation state and the determination of the touch operation state. The touch detection device according to claim 1, wherein the touch determination threshold value and the non-touch determination threshold value are adjusted by the same process of performing. The touch detection device according to claim 1, wherein the sensor electrode and the shield electrode are formed in the same area.

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