JP2008041484A - Switch device with touch detection function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a touch detector capable of providing stable capacitance in touch of a finger to a touch detecting electrode, and of surely detecting a touch operation to an operation member. <P>SOLUTION: The thin-film-shaped touch detecting electrode 4 is formed on a surface of an operation button 3, a coupling electrode 5 is embedded in the operation button 3 to be faced and capacitively coupled to the touch detecting electrode 4, and a printed wiring board 6 having a wiring part 8 electrically connected to the coupling electrode 5 is arranged. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a switch device with a touch detection function having a touch detection electrode for detecting when a finger touches an operation member.

  For example, a switch device for selecting a display device that displays a plurality of selection units on a screen includes operation buttons as a plurality of operation members corresponding to the plurality of selection units, and an operation button selected by a user. A configuration is considered in which when a pressing operation is performed with a finger, a switch element disposed below the operation button operates to select and determine a corresponding selection unit in a display state.

  In addition, a publicly known document corresponding to the problem to be solved by the present invention could not be found.

By the way, in the above-mentioned thing, the user needs to operate after seeing and selecting the operation button of the switch device. For this reason, the user needs to see both the operation button of the switch device and the screen of the display device, and there is a problem that the operability is not good.
Therefore, in order to deal with such a problem, the inventors considered the following. That is, when a finger touches the operation button of the switch device, this is detected, and the display state of the selection unit corresponding to the operation button is changed. According to such a configuration, since the position of the operation button in contact with the finger can be known by looking at the display screen, it is possible to operate by looking only at the display screen without looking at the operation button of the switch device. It becomes possible.

  As a switch device with a touch detection function for realizing this, the inventors considered a configuration (comparative example) shown in FIG. 5, for example. FIG. 5 is a longitudinal sectional view of the switch device with a touch detection function. The operation button 101 constituting the operation member is formed of a synthetic resin so as to have an inverted U shape with an opening on the lower surface side, and a touch detection electrode 102 is provided on the lower surface of the operation surface portion 101a. A body 103 is arranged around the operation button 101 with a space for movement of the operation button 101 interposed therebetween.

A printed wiring board 104 is disposed below the operation button 101, and printed wiring is provided on the printed wiring board 104. In addition, an LED 105 for illumination of the operation button 101 is mounted near the center of the component mounting surface (upper surface) of the printed wiring board 104.
The touch detection electrode 102 is electrically connected to a wiring portion (not shown) of the printed wiring board 104 via a flexible printed wiring board (hereinafter referred to as FPC) 106 that can be elastically deformed. The FPC 106 has a structure in which a copper wiring portion (not shown) is sandwiched between plastic sheets, and the upper surface portion on one end side disposed on the operation surface portion 101a of the operation button 101 is used for touch detection. The electrode 102 is used.

  The FPC 106 is arranged to bend along the inner surface of one side surface portion 101 b of the operation button 101, the component mounting surface on the left side of the printed wiring board 104 in FIG. 5 and the lower surface, and an inner case 101 c is disposed inside the operation button 101. It is fixed by press-fitting. The other end side of the FPC 106 is connected to the wiring portion via a connector 107 mounted on the lower surface of the printed wiring board 104, and is fixed to the printed wiring board 104 by a fixing member 108 at the front portion of the connector 107. .

In the printed wiring board 104, a switch 109 as a switch element is disposed at a position corresponding to the lower side of the other side surface portion 101d of the operation button 101. In this case, a gap is set between the side surface portion 101b of the operation button 101 and the component mounting surface of the printed wiring board 104 that allows the operation button 101 to move downward.
In the illustrated configuration, only one operation button 101 is provided, but actually, a plurality of units including the operation buttons 101 are provided corresponding to a plurality of selection units of the display device. Each switch 109 is connected to a control device (not shown) composed of, for example, a microcomputer.

  In the above configuration, when the user's finger comes into contact with the operation surface portion 101a on the upper surface of the operation button 101, the finger becomes the ground side and a capacitor is formed by the finger and the touch detection electrode 102, which connects the FPC 106 and the connector 107. And the signal level of the detection circuit of the printed wiring board 104 changes. The control device detects the contact of the finger with the operation button 101 based on the change in the signal level, and puts the selection unit corresponding to the operation button 101 in the display state on the screen of the display device (not shown). When the operation button 101 is pressed downward and the switch 109 is pressed by the side surface portion 101d of the operation button 101, the switch 109 operates to output a selection signal to be given to the control device. Sets the selection portion corresponding to the switch 109 to a fixed display state and determines the selection of the selection portion.

  However, in the switch device with a touch detection function having the above-described configuration, when the user touches the operation button 101 with a finger, the operation button 101 depends on the contact state (the size of the finger, the contact location, the contact pressure, etc.). Since the contact area with respect to the electrode changes, the capacitance of the capacitor composed of the fingers and the touch detection electrode 102 also changes, and the capacitance varies, and the touch detection is performed reliably. There is a risk that it will not be possible.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably detect a touch operation on an operation member by obtaining a stable capacitance when a finger touches a touch detection electrode. Another object is to provide a switch device with a touch detection function.

  In order to achieve the above-described object, the switch device with a touch detection function according to the present invention detects an operation member, a switch element that operates based on the operation of the operation member, and a finger touching the operation member. A touch detection electrode formed in a thin film on the surface of the operation member, a coupling electrode provided on the operation member so as to be electrostatically coupled to the touch detection electrode, and the coupling electrode And a printed wiring board having a wiring portion electrically connected to the wiring board.

  According to the present invention, when the user's finger contacts the operation member, the touch detection electrode is connected to the ground via the finger, and the touch detection electrode and the coupling electrode have a stable capacitance. A capacitor is configured, and the stable electrostatic capacity can be detected on the wiring portion side of the printed wiring board, and a touch operation on the operation member can be reliably detected.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a longitudinal sectional view of a switch device with a touch detection function. In FIG. 1, a button housing hole 2 is formed in a plastic body 1, and the button housing hole 2 has an upper portion made smaller than other parts, and a step 2a is formed between the two. Is formed. An operation button 3 as an operation member is stored in the button storage hole 2 of the body 1. The operation button 3 is formed of a light-transmitting plastic and is formed in a rectangular container shape whose lower surface is opened, and the upper part is made smaller than other parts, and a step part 3c is formed between the small part 3a and the large part 3b. Is formed.

  On the entire surface except the lower surface of the operation button 3, a thin film-like touch detection electrode 4 is formed by sputtering or plating with a conductive material. In this case, the touch detection electrode 4 has translucency because of its thin film shape, but may be formed in advance as a transparent conductive film using ITO (indium + tin oxide film). In the large portion 3 b of the operation button 3, a coupling electrode 5 made of metal such as copper is embedded. The coupling electrode 5 is embedded at the same time as the operation button 3 is molded with plastic. As shown in FIG. 2, the coupling electrode 5 has a substantially U-shape located on the three sides of the large portion 3b. A connecting piece 5a protruding downward from the lower end of the large portion 3b is formed. The coupling electrode 5 is opposed to the touch detection electrode 4 with a predetermined gap. As will be described later, the coupling electrode 5 is electrostatically coupled to the touch detection electrode 4 and is connected to a capacitor C1 (see FIG. 3). ).

  As shown in FIG. 1, a printed wiring board 6 is disposed below the operation button 3, and printed wiring is provided on the printed wiring board 6. Further, an LED 7 for illumination of the operation button 3 is mounted near the center of the component mounting surface (upper surface) of the printed wiring board 6. Furthermore, a wiring part 8 is provided on the component mounting surface of the printed wiring board 6, and one end of a flexible connection line 9 is connected to the wiring part 8 by soldering. The other end is connected to the connection piece 5a of the 9 coupling electrode 5 by soldering.

  As shown in FIG. 1, a cover 10 made of transparent rubber such as silicon rubber is attached to the printed wiring board 6, thereby covering the component mounting surface. This cover 10 is integrally formed with a flexible portion 11 having a conical shape (a state in which the cup is turned down), and a pressure receiving portion 11 a on the upper side thereof comes into contact with a pressing portion 3 d on the lower surface of the operation button 3 from below. It is designed to bias upward. Thereby, the operation button 3 is urged upward, the step portion 3 c abuts on the step portion 2 a of the body 1, and the upper portion of the small portion 3 a is held in a state of slightly protruding from the upper surface of the body 1. A movable contact 12a is provided on the lower surface of the pressure receiving portion 11a of the flexible portion 11, and fixed contacts 12b and 12b are provided on the component mounting surface of the printed wiring board 6 so as to face the movable contact 12a. 12 is configured.

  In the illustrated configuration, only one operation button 3 is provided, but actually, a plurality of units including the operation buttons 3 are provided corresponding to a plurality of selection units of a display device (not illustrated). Each switch 12 is connected to a control device (not shown) composed of, for example, a microcomputer.

  Next, the touch detection circuit 13 of the switch device with a touch detection function will be described with reference to FIG. The touch detection circuit 13 is a general capacitance detection circuit, and an oscillation unit 14 (one terminal is connected to the ground) that outputs a high-frequency signal, a load resistor 15, and detection and smoothing of the high-frequency signal. A detection unit 16 and an operational amplifier 17 are provided.

  The coupling electrode 5 is connected to the output terminal (the other terminal) of the oscillating unit 14 via the load resistor 15, the wiring unit 8, and the connection line 9. The detection unit 16 includes a diode and a capacitor, and a high frequency signal from the oscillation unit 14 is input via the load resistor 15. The output of the detection unit 16 is input to the control device as an amplified and offset signal Vout through the operational amplifier 17. The oscillation unit 14, the load resistor 15, the detection unit 16, and the operational amplifier 17 are configured as a packaged capacitance detection IC 18.

Next, the operation of this embodiment will be described.
When the user's finger approaches the upper surface of the small portion 3 a of the operation button 3, the user's finger is connected to the ground. Therefore, a variable capacitor can be used between the user's finger and the touch detection electrode 4. C2 is formed, and the touch detection electrode 4 and the coupling electrode 5 form a parallel plate-shaped fixed capacitor C1, which are connected in series. In this case, the capacitance of the combined capacitor C3 of the capacitors C1 and C2 can be expressed as follows.

C3 = (C1 × C2) / (C1 + C2) [F]
In the above configuration, when the user's finger contacts the upper surface of the operation button 3, that is, the touch detection electrode 4, the touch detection electrode 4 is connected to the ground via the finger, and the capacitance of the capacitor C2 Will grow. On the other hand, the capacitance of the parallel plate capacitor C1 is constant smaller than the capacitance of the capacitor C2 by adjusting the size of the touch detection electrode 4 and the coupling electrode 5 and the distance between the electrodes. From the above equation, the capacitance of the composite capacitor C3 can be regarded as substantially the same as that of the capacitor C1 (C3≈C1).

  As a result, the wiring portion 8 of the printed wiring board 6 is connected to the ground via the connection line 9, the composite capacitor C3 (C3≈C1), and fingers. Therefore, the high-frequency signal output from the oscillating unit 14 is divided by the resistance value of the load resistor 15 and the impedance of the composite capacitor C3 and input to the detection unit 16. As a result, since the level of the high-frequency signal input to the detection unit 16 is smaller than in a state where the finger is not touching the touch detection electrode 4, the signal Vout output via the detection unit 16 and the operational amplifier 17 is reduced. The level is also reduced. The control device detects the touch of the finger on the operation button 3 based on the change in the level of the signal Vout, and puts the selection unit corresponding to the operation button 3 in a temporary display state on the screen of the display device (not shown).

  Thereafter, when the operation button 3 is pressed downward by the user and the switch 12 is pressed by the pressing portion 3d of the operation button 3, the switch 12 operates (turns on) and the on signal is used as a selection signal to the control device. The control device changes the selection unit corresponding to the operation button 3 to a fixed display state, and determines the selection of the selection unit.

  As described above, according to the present embodiment, the thin-film touch detection electrode 4 is formed on the surface of the operation button 3, and the coupling electrode is electrostatically coupled to the operation button 3 so as to face the touch detection electrode 4. 5 is embedded so that the coupling electrode 5 is electrically connected to the wiring portion 8 of the printed wiring board 6. Therefore, when the user touches the upper surface of the operation button 3, that is, the touch detection electrode 4 with a finger, the touch detection electrode 4 is connected to the ground via the finger, so that the finger and the touch detection electrode 4 are connected. The capacitor C1 is formed by the touch detection electrode 4 and the coupling electrode 5 as the capacitor C2 is formed, and the capacitance of the combined capacitor C3 is substantially equal to that of the capacitor C1. Since the capacitor C1 has a stable capacitance regardless of the contact state of the finger with respect to the touch detection electrode 4 (the size of the finger, the contact location, the contact pressure, etc.), the touch detection circuit 13 is controlled by the finger to the operation button 3. A touch operation can be reliably detected.

Further, as described above, the coupling electrode 5 is electrostatically coupled to the touch detection electrode 4, and the coupling electrode 5 is electrically connected to the wiring portion 8 of the printed wiring board 6 by the connection line 9. Therefore, connection of the connection line to the thin film-like touch detection electrode 4 is not necessary, and wiring is facilitated accordingly.
Since the operation button 3 and the touch detection electrode 4 have translucency, and the coupling electrode 5 has a substantially U shape in which the upper and lower surfaces are open, the illumination effect of the LED 7 can be sufficiently obtained.

FIG. 4 shows a second embodiment of the present invention, in which the same parts as those in the above-described embodiment (particularly FIG. 1) are denoted by the same reference numerals.
As with the operation button 3, the operation button 19 as an operation member is stored in the button storage hole 2 of the body 1. The operation button 19 is formed of a light-transmitting plastic and is formed in a rectangular container shape whose lower surface is opened, and the upper part is made smaller than other parts, and a step portion 19c is formed between the small portion 19a and the large portion 19b. Is formed. On the surface excluding the lower surface of the operation button 19, as in the case of the operation button 3, a thin-film touch detection electrode 4 is formed over the entire surface by sputtering or plating with a conductive material. The pressing portion 19 d on the lower surface of the operation button 19 comes into contact with the pressure receiving portion 11 a of the flexible portion 11 of the cover 10 from above. As a result, the operation button 19 is urged upward by the flexible portion 11, the step portion 19 c comes into contact with the step portion 2 a of the body 1, and the upper portion of the small portion 19 a slightly protrudes from the upper surface of the body 1. Retained.

  A coupling electrode 20 is arranged on the inner surface of the upper portion and one side portion of the small portion 19a of the operation button 19 and the inner surface of one side portion of the large portion 19b. The operation button 19 is held by press-fitting. In this case, the coupling electrode 20 faces a part of the touch detection electrode 4 with a predetermined gap, and is electrostatically coupled to the touch detection electrode 4 to provide a capacitor (for convenience of explanation). 3 (see C1). The electrode portion 20a located in the small portion 19a of the coupling electrode 20 is formed with a light transmitting through hole 20b. The upper portion of the inner case 21 has a through hole 21a facing the through hole 20b. Is formed.

The coupling electrode 20 is electrically connected to the wiring portion 8 of the printed wiring board 6 through an elastically deformable flexible printed wiring board (hereinafter referred to as FPC) 22 as described later. The FPC 22 has a structure in which a copper wiring portion (not shown) is sandwiched between plastic sheets, and one end portion located in the operation button 19 is used as a coupling electrode 20. The other end portion side of the FPC 22 is connected to the wiring portion 8 via a connector 23 attached to the lower surface of the printed wiring board 6, and is fixed to the printed wiring board 6 by a fixing member 24 at a front portion of the connector 23. ing.
Thus, in this second embodiment, the coupling electrode 20 functions as the coupling electrode 5 of the above-described embodiment. Therefore, the second embodiment is the same as the first embodiment. The effect of this can be obtained.

In the second embodiment, the coupling electrode 20 is formed by the FPC 22, but instead, for example, it may be formed of an elastically deformable film made of a conductive member, or a thin film on the surface. You may form by the elastically deformable insulating film which gave the shape-shaped electrically-conductive member.
In the second embodiment, the thin touch detection electrode 4 is provided on the entire surface of the operation button 19. However, for example, the touch detection electrode is provided only on the portion facing the coupling electrode 20. Alternatively, conversely, instead of the coupling electrode 20, a coupling electrode facing the entire touch detection electrode 4 may be provided.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications and expansions are possible.
In the above embodiment, a display device having a plurality of selection units is provided, and the selection of the selection unit is determined by the operation of the switch 12. However, for example, the display unit simply has a plurality of display units corresponding to a plurality of operation buttons. A display device may be provided.
Moreover, in the said Example, although LED7 was provided, this should just be provided as needed.

1 is a longitudinal sectional view of a switch device with a touch detection function according to a first embodiment of the present invention. Perspective view of coupling electrode The figure which shows the equivalent circuit of the touch detection circuit FIG. 1 equivalent view showing a second embodiment of the present invention. FIG. 1 equivalent diagram showing a comparative example

Explanation of symbols

  In the drawing, 3 is an operation button (operation member), 4 is a touch detection electrode, 5 is a coupling electrode, 6 is a printed wiring board, 8 is a wiring portion, 12 is a switch (switch element), 13 is a touch detection circuit, Reference numeral 19 denotes an operation button (operation member), 20 denotes a coupling electrode, 21 denotes an inner case, and 22 denotes a flexible printed wiring board.

Claims (1)

An operation member;
A switch element that operates based on the operation of the operation member;
A touch detection electrode formed in a thin film on the surface of the operation member in order to detect contact with a finger;
A coupling electrode provided on the operation member so as to be electrostatically coupled to the touch detection electrode;
A switch device with a touch detection function, comprising: a printed wiring board having a wiring portion electrically connected to the coupling electrode.

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