JP2014110013A - Touch position detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a touch position detection device for more accurately detecting a touch position even if the thickness of a design panel is not uniform.SOLUTION: A detection part 17 of a control device 11 detects respective electrostatic capacitance of each electrode. An electrostatic capacitance correction part 13 of the control device 11 corrects the electrostatic capacitance on the basis of a correction coefficient of each electrode stored in a memory 12. A touch position calculation part 14 calculates a position (touch position) touched by a finger of a user on the basis of the corrected electrostatic capacitance.

Description

  The present invention relates to a touch position detection device.

  Conventionally, capacitive touch sensors shown in Non-Patent Documents 1 and 2 are known. As shown in FIG. 3, the touch sensor 100 includes five sensors (electrodes) 101a to 101e arranged in parallel, an overlay (for example, a design panel) 102 covering the sensors 101a to 101e, and electrostatics of the sensors 101a to 101e. And a device 103 that converts the capacitance Cx into a digital code. As shown in the figure, the capacitance Cx when the finger is in contact with the sensor 101c, for example, is the addition of the capacitance Cf affected by the finger in contact with the overlay 102 to its own stray capacitance Cp. It is a thing. The device 103 generates a digital code proportional to the capacitance Cx. The device 103 determines the state of the sensor 101c based on the digital code. That is, the device 103 determines whether or not the corresponding sensor 101c is touched by comparing the digital code with a preset threshold value. In addition, the touch sensor 100 specifies the position of the finger on the overlay 102 by executing a determination logic incorporated in its own firmware.

Cypress Semiconductor Corporation, “CapSense® Design Guide”, pages 11-13, Internet <URL: http: // www. cypress. com /? docID = 36161> Cypress Semiconductor Corporation, “CapSense® Delta Sigma Data Sheet CSD V1.50”, pages 3-6, Internet <URL: http: // www. cypress. com /? docID = 27359>

  Incidentally, in recent years, it has been studied to apply the touch sensor 100 as shown in FIG. 3 to a switch provided, for example, in an instrument panel for a vehicle. In this case, the touch switch is required to have various appearances for reasons such as design or installation location. For example, it is conceivable that a curved appearance is required according to the instrument panel. At this time, the surface of the overlay 102 is curved. That is, the thicknesses of the portions corresponding to the sensors 101a to 101e in the overlay 102 are different. For this reason, the capacitance Cf affected by the finger in contact with the overlay 102 is small where the thickness of the overlay 102 is thick, and is large where the thickness of the overlay 102 is thin. Thus, when a finger is brought close to a sensor located in a thick area of the overlay 102, the digital code generated by the device 103 is smaller than when the thickness of the overlay 102 is uniform. Therefore, the touch sensor 100 may not be able to accurately detect the state of the sensor or the position of the finger on the overlay 102.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a touch position detection device capable of accurately determining a touch position even if the thickness of the design panel is not uniform. .

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
In the touch position detection device that solves the above problems, a plurality of electrodes are laid on the back surface of the design panel, and the touch position detection device detects the touch position on the design panel based on the capacitance generated from the electrodes. Based on the detection unit for detecting the capacitance of the electrode, a memory in which a correction coefficient for eliminating variation in capacitance due to a difference in thickness of the design panel is stored in advance, and the correction coefficient. A correction unit that corrects the detection value; and a touch position calculation unit that calculates a touch position based on the corrected detection value.

  According to this configuration, the detection value detected by the detection unit is corrected using the correction coefficient for eliminating the variation in the capacitance caused by the difference in the thickness of the design panel. As a result, the corrected detection value is one in which the influence of the variation in capacitance caused by the difference in the thickness of the design panel is eliminated. By using this corrected detection value, it is possible to reduce the deviation between the touch position calculated by the touch position calculation unit and the touch position when the thickness of the design panel is uniform. That is, even if the thickness of the design panel is not uniform, the touch position can be accurately detected.

In the touch position detection device, it is preferable that the correction coefficient is obtained by a ratio between a thickness serving as a reference of the design panel and a thickness of a portion corresponding to each electrode.
According to this structure, a correction | amendment part calculates a correction coefficient by ratio of the thickness used as the reference | standard of a design panel, and the thickness of the site | part corresponding to each electrode. Thereby, the deviation of the calculated finger position and the actual touch position can be eliminated by minimizing the variation in capacitance due to the thickness of the design panel.

About the said touch position detection apparatus, it is preferable that the said touch position calculating part detects a touch position by taking the load average of the electrostatic capacitance change amount of each said electrode.
According to this configuration, the touch position calculation unit calculates the touch position by taking a load average of the capacitance change amount of each electrode. Even in this case, the deviation between the calculated finger position and the touch position when the thickness of the design panel is uniform is eliminated by eliminating the variation in the capacitance due to the difference in the thickness of the design panel 15. Can be reduced.

  According to the present invention, the touch position can be accurately determined even if the thickness of the design panel is not uniform.

The block diagram which shows the structure of the touch position detection apparatus in one Embodiment. Schematic which shows the relationship of the touch coordinate before correction | amendment of the touch position detection apparatus in the embodiment, and after correction | amendment. Schematic which shows the structure of the conventional electrostatic capacitance type touch sensor.

Hereinafter, an embodiment in which the touch position detection device is embodied as a capacitive touch switch provided in an instrument panel for a vehicle will be described.
<Configuration>
As shown in FIG. 1, the touch switch 10 includes a design panel 15, a substrate 16, five electrodes 0 to 4, and a control device 11.

On the upper surface of the substrate 16, thin plate-like electrodes 0 to 4 are provided in a line at intervals in the left-right direction in the drawing. The electrodes 0 to 4 are connected to the control device 11 via the substrate 16.
A design panel 15 that covers the electrodes 0 to 4 is provided on the upper surface of the substrate 16. The surface of the design panel 15 has a curved surface that is convex upward, and functions as an operation surface that is touch-operated with a finger or the like. Further, the back surface of the design panel 15 is fixed to the upper surfaces of the electrodes 0 to 4. The magnitude relationship between the thicknesses D0, D1, D2, D3, and D4 of the portions corresponding to the electrodes of the design panel 15 is as follows.

The control device 11 includes a memory 12, a capacitance correction unit 13, a touch position calculation unit 14, and a detection unit 17.

The detection part 17 can each detect the electrostatic capacitance C0-C4 (detection value) of each electrode 0-4 shown by FIG.
The memory 12 is a non-working memory, and a capacitance correction coefficient for the electrodes 0 to 4 is stored in advance.

The electrostatic capacity correction unit 13 corrects the electrostatic capacity of each of the electrodes 0 to 4 using a correction coefficient corresponding to each of the electrodes 0 to 4.
The touch position calculation unit 14 calculates touch coordinates (touch position) based on the capacitances C0 to C4 corrected by the capacitance correction unit 13. A specific correction coefficient, a correction method for the capacitances C0 to C4 of the electrodes 0 to 4 and a calculation method for touch coordinates will be described later.
<Touch coordinate calculation process>
Next, processing for calculating touch coordinates by the touch switch 10 will be described.

  The capacitance Ck detected by the detection unit 17 of the control device 11 is expressed by the following equation (2).

Where ε is the dielectric constant (in this example, the dielectric constant of the design panel 15), S is the area (in this example, the contact area between the finger and the electrode), and Dk is the interval (in this example, the thickness of the design panel 15). That is). K is the number of the electrode, that is, 0 to 4, and Dk indicates the thickness D0 to D4 of the design panel 15 with respect to the electrodes 0 to 4. Accordingly, the capacitances C0 to C4 of the electrodes 0 to 4 can be calculated based on (Equation (2)).

  Further, if the user is required to touch different positions on the surface of the design panel 15 with the same finger, it can be considered that the dielectric constant ε and the area S of the formula (2) are the same. Therefore, the smaller the thickness of the design panel 15, the larger the detected capacitance, and the larger the thickness, the smaller the detected capacitance. Therefore, the magnitude relationship between the capacitances C0 to C4 is as follows.

The touch position calculation unit 14 calculates touch coordinates Zk based on the capacitances C0 to C4. The touch coordinate Zk is expressed as the following equation (4).

However, T in Equation (4) is a constant. In this example, the constant T is 100.

  Here, as shown in FIG. 2, for example, when a portion corresponding to the electrode 2 on the surface of the design panel 15 is touched, the touch coordinates Z2 calculated by the touch position calculation unit 14 is the value before correction indicated by the dotted arrow. Touch coordinates. That is, the touch coordinates calculated in the case where the calculated touch coordinates Zk and the thickness of the design panel 15 are uniform due to variations in the capacitances C0 to C4 shown in the above-described formula (3) (in this example, 200). For this reason, in this example, C0 to C4 are corrected.

  Next, a correction method for eliminating variations in the capacitances C0 to C4 that occur because the thickness of the design panel 15 is different will be described. In this example, the correction coefficients M0 to M4 are calculated based on the thickness D0 where the thickness of the design panel 15 is the thinnest.

  As described above, the correction coefficients M1 to M4 can be calculated based on the fact that the dielectric constant ε and the contact area S are the same. As shown in the following equation (5), the correction coefficient Mk is determined based on the thickness Dk (k = 0 to 4) of the part corresponding to the electrode k (k = 0 to 4) in the design panel 15 and the design of the electrode 0. 15 is the ratio of the thickness D0 of the part to the electrode 0 in FIG.

The capacitance correction unit 13 corrects the correction coefficients M0 to M4 corresponding to the electrodes 0 to 4 stored in the memory 12 with respect to the capacitances C0 to C4 of the electrodes 0 to 4 detected by the detection unit 17. Is applied to correct the capacitances C0 to C4. Specifically, as shown in the following equation (6), the detected capacitances C0 to C4 of the electrodes 0 to 4 are multiplied by correction coefficients M0 to M4 corresponding to the electrodes 0 to 4, respectively. Make corrections.

The touch position calculation unit 14 calculates the touch coordinates Zk based on the capacitances C0 to C4 corrected by the capacitance correction unit 13.

  Therefore, as shown in FIG. 2, when a portion corresponding to the electrode 2 on the surface of the design panel 15 is touched, the touch coordinates Z2 calculated by the touch position calculation unit 14 is corrected after indicated by a solid arrow in the drawing. The touch coordinates. In other words, the touch coordinates Z2 calculated by the touch position calculation unit 14 and the touch coordinates (200 in this example) when the thickness of the design panel 15 is uniform coincide with each other.

  Thus, even if the thickness of the design panel 15 is not uniform, the touch position calculation unit 14 accurately detects the touch coordinates Z0 to Z4 based on the corrected capacitances C1 to C4 of the electrodes 1 to 4. Can be calculated. Further, if the thickness of the design panel 15 is uniform, the contact area (S) of the finger is the same and the capacitances C0 to C4 of the electrodes 0 to 4 are the same, so the correction coefficient M1 of each of the electrodes 1 to 4 -M4 is all 1 (formula (4)). Therefore, even when the thickness of the design panel 15 is uniform by the touch position calculation method described above, the touch coordinates Z0 to Z4 can be accurately calculated.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) The detection unit 17 of the control device 11 detects the capacitances C0 to C4 of the electrodes 0 to 4. The electrostatic capacity correction unit 13 of the control device 11 corrects the electrostatic capacity C0 to C4 based on the correction coefficients M0 to M4 stored in the memory 12. The touch position calculation unit 14 calculates the touch coordinates Z0 to Z4 based on the corrected capacitances C0 to C4. Thereby, the displacement of the touch position caused by the thickness of the design panel 15, that is, the displacement between the position where the curved surface of the design panel 15 is touched with a finger and the touch position when the thickness of the design panel 15 is uniform. Can be eliminated.

  (2) The correction coefficient was calculated by the ratio between the thickness D0 to D4 of the design panel 15 and the thickness D0 at the thinnest position, as represented by Expression (5). Therefore, the capacitances C1 to C4 generated from the electrodes 1 to 4 with the thicknesses D1 to D4 in the design panel 15 and the capacitance C0 of the electrode 0 corresponding to the thinnest part of the design panel 15 The difference can be as close to 0 as possible.

  (3) The touch position calculation unit 14 calculates the same as when the thickness of the design panel 15 is not uniform even when the design panel 15 is uniform. Accordingly, the touch switch 10 can accurately calculate the touch position regardless of the shape of the design panel 15.

<Other embodiments>
In addition, the said embodiment can be implemented with the following forms which changed this suitably.
-The touch position calculation part 14 of this example may calculate a touch position by taking the load average of the electrostatic capacitance change amount of each electrode. Specifically, the touch position calculation unit 14 calculates touch coordinates based on the corrected load average of the electrodes. That is, the touch coordinate Zk is calculated by the following equation (7). The same effects as (1) to (3) of this example are obtained.

The touch position calculation method of the touch position calculation unit 14 of this example and the above modification may be as follows. For example, you may calculate a touch coordinate based on the voltage value of each electrode 0-4 instead of the electrostatic capacitance of each electrode 0-4. Specifically, a C / V converter is newly provided. The C / V converter converts the capacitance corrected by the capacitance correction unit 13 into a voltage and outputs the voltage to the touch position calculation unit 14. The touch switch 10 calculates a touch position based on the voltage value of the C / V converter. Thereby, the effect similar to (1)-(3) of this example is acquired.

  The voltage applied to the electrodes 0 to 4 may be a DC voltage, an AC voltage, or a clock signal voltage. Even in this case, since the touch position can be calculated based on the capacitance of the electrodes 0 to 4, the same effects as (1) to (3) of the present embodiment can be obtained.

The surface shape of the design panel 15 may be, for example, a semicircular shape or a concave shape (a curved surface that protrudes downward). Moreover, it does not need to be curved.
-Touch switch 10 of this example is not provided in the instrument of a car, and may be used for other products. For example, you may utilize for electrostatic touch switches, such as a car navigation system, a car audio, or household appliances.

-The number and arrangement of electrodes may be changed as appropriate. For example, the electrodes may be arranged in a circular shape.
Next, a technical idea that can be grasped from the embodiment will be added together with the effect.

(A) A C / V converter that converts the detected value into a voltage value is provided, and the touch position calculation unit calculates a touch position based on the voltage value converted by the C / V converter.
According to this configuration, the touch position calculation unit 14 calculates a touch position (touch coordinates) based on the voltage value converted by the C / V converter. Thereby, even if the thickness of the design panel is not uniform, the touch position can be accurately calculated based on the voltage value.

  DESCRIPTION OF SYMBOLS 0-4 ... Electrode, C0-C4 ... Capacitance, M0-M4 ... Correction coefficient, Z0-Z4 ... Touch coordinate, 10 ... Touch switch, 11 ... Control apparatus, 12 ... Memory, 13 ... Capacitance correction | amendment part, DESCRIPTION OF SYMBOLS 14 ... Touch position calculating part, 15 ... Design panel, 16 ... Board | substrate, 17 ... Detection part.

Claims (3)

In the touch position detection device in which a plurality of electrodes are laid on the back surface of the design panel and the touch position on the design panel is detected based on the capacitance generated from the electrodes.
Based on the detection unit for detecting the capacitance of the electrode, a memory in which a correction coefficient for eliminating variation in capacitance due to a difference in thickness of the design panel is stored in advance, and the correction coefficient. A touch position detection apparatus comprising: a correction unit that corrects a detection value; and a touch position calculation unit that calculates a touch position based on the corrected detection value. The touch position detecting device according to claim 1,
The touch position detection device is obtained by calculating the correction coefficient based on a ratio between a thickness serving as a reference of the design panel and a thickness of a portion corresponding to each electrode. In the touch position detection apparatus according to claim 1 or 2,
The touch position calculation unit is a touch position detection device that detects a touch position by taking a load average of capacitance change amounts of the electrodes.