JP2011257882A - Touch sensor and touch detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a touch sensor and touch detection method which are capable of detecting change in the electrostatic capacitance caused by a human body approaching or contacting, and reducing high-frequency noise radiated to the outside.SOLUTION: The touch sensor includes: a detection electrode 2 to and with which a human body approaches or contacts; a capacitor 3 whose one electrode A is serially connected with the detection electrode 2 via a resistor; a first grounding circuit 4 for connecting or disconnecting between the electrode A and a ground potential; a second grounding circuit 5 for connecting or disconnecting between the other electrode B of the capacitor 3 and the ground potential; a voltage applying circuit 6 for connecting or disconnecting between the electrode B and a DC power source; a measuring circuit 7 for measuring a potential at the electrode B; and a controller for switching between the voltage applying circuit 6, the first grounding circuit 4, and the second grounding circuit 5, and determining the approach or contact of the human body by a measured value by the measuring circuit 7.

Description

  The present invention relates to a touch sensor and a touch detection method, and more particularly to a touch sensor and a touch detection method that can detect a change in capacitance or the like due to proximity or contact of a human body with a simple configuration and control.

  2. Description of the Related Art Conventionally, a touch sensor that includes a detection electrode that is close to or in contact with a human body and that detects the proximity or contact of the human body by measuring a change in capacitance between the human body and a stray capacitance or ground (ground) has been widely used. ing. In such a touch sensor, the change in capacitance is detected by charging or discharging the capacitance generated in the detection electrode to measure the voltage or charge amount, or by using the change in impedance of the detection circuit. Is done. However, since the change in capacitance caused by the proximity or contact of the human body is a minute value, a touch sensor that improves detection accuracy by repeating charge and discharge is known. For example, there is disclosed a charge transfer type capacitance measurement circuit that includes a known capacitor and switch means, repeatedly charges and discharges an unknown capacitor generated by a human body or the like, and accumulates charge in the known capacitor with high accuracy (see FIG. (See Patent Documents 1 and 2).

Japanese translation of PCT publication No. 2002-530680 JP 2006-78292 A

However, in a touch sensor using the charge transfer capacitance measurement circuit or the like, a charge or discharge or charge is repeatedly performed on a detection electrode that a human body or the like approaches or contacts, and the capacitance is measured by accumulating the charge and discharge characteristics. Therefore, high frequency noise due to the charge / discharge operation is radiated from the detection electrode to the surrounding environment. In general, in order to reduce high-frequency noise emitted from the device to the outside, there is a method in which the device is sealed with a case of metal or the like. However, in the case of a touch sensor, it is necessary to open a detection electrode to which the human body approaches or approaches, so that it is impossible to take a countermeasure for electromagnetically shielding the electrode portion.
In particular, in the case of a touch sensor mounted on a vehicle, electromagnetic interference (EMI, Electromagnetic Interference) that hinders the operation of surrounding electronic devices is a serious problem. For example, if the charging / discharging repetition time of the touch sensor is about 7 μs, high-frequency noise is radiated not only in a frequency region centered around 140 kHz but also in a wide frequency range. When such high-frequency noise is radiated, there has been a problem that obstructs the operation of in-vehicle devices such as radio broadcast reception and smart entry systems.

  Further, the conventional touch sensor as described above has a complicated configuration and processing, such as using a dedicated processor for controlling charging and charging / discharging at high speed. For this reason, in the case where a plurality of detection electrodes are provided so as to detect the proximity or contact of the human body with respect to each detection electrode, there is a problem that the touch sensor becomes complicated and large in size and high in cost.

  In view of the above problems, the present invention can detect a change in capacitance or the like due to the proximity or contact of a human body with a simple configuration and control, and can reduce high-frequency noise emitted to the outside. An object of the present invention is to provide a touch detection method.

  In order to solve the above problems, the invention described in claim 1 is a touch sensor that detects proximity or contact of a human body, and includes a detection electrode that is close to or in contact with a human body, the detection electrode, and a resistor. A capacitor connected in series with one electrode (A), a first ground circuit for connecting or disconnecting one electrode (A) of the capacitor and a ground potential, and the other electrode (B) of the capacitor A second grounding circuit for connecting or disconnecting to and ground potential, a voltage applying circuit for connecting or disconnecting the other electrode (B) of the capacitor and a DC power source, and one of the electrodes of the capacitor. The measurement circuit for measuring the potential of the electrode and the voltage application circuit, the first ground circuit, and the second ground circuit are respectively switched, and the proximity or contact of the human body is determined based on the potential measured by the measurement circuit. A control unit to And the control unit disconnects the voltage application circuit and connects the first ground circuit and the second ground circuit, and the first ground circuit and the second ground circuit. And a third step of connecting the voltage application circuit and a third step of measuring the potential by the measurement circuit.

According to a second aspect of the present invention, in the first aspect, the measurement circuit is connected to the one electrode (A) of the capacitor, and the control unit is in the state of the second step in the third step. And the measurement of the potential by the measurement circuit.
According to a third aspect of the present invention, in the first aspect, the measurement circuit is connected to the other electrode (B) of the capacitor, and the control unit includes the voltage application circuit and the The gist is to measure the potential by the measurement circuit after disconnecting the second ground circuit and connecting the first ground circuit.
A fourth aspect of the present invention is the first to third aspects, wherein the first ground circuit is configured by a first logic circuit element having an output connected to one electrode (A) of the capacitor. The gist of the voltage application circuit and the second ground circuit is a second logic circuit element whose output is connected to the other electrode (B) of the battery.

The gist of a fifth aspect of the present invention is that, in the first to fourth aspects, the control unit repeatedly performs the first step to the third step at a cycle of 1 ms to 7 ms.
A sixth aspect of the present invention is the vehicle according to any one of the first to fifth aspects, wherein the detection electrode is a substantially rectangular sheet-shaped conductor, or a long plate-shaped or rod-shaped conductor. Is the gist.

  The invention according to claim 7 is a touch detection method for detecting the proximity or contact of a human body, and a detection electrode with which the human body approaches or contacts, and one electrode (A) in series via the detection electrode and a resistor. ), A first ground circuit that connects or disconnects one electrode (A) of the capacitor and the ground potential, and a connection or disconnection of the other electrode (B) of the capacitor and the ground potential. A second grounding circuit, a voltage application circuit for connecting or disconnecting the other electrode (B) of the capacitor and a DC power source, and a potential of the electrode connected to any one electrode of the capacitor A first step of disconnecting the voltage application circuit and connecting the first ground circuit and the second ground circuit using a touch sensor including a measurement circuit; and the first ground circuit and the first ground circuit. When the ground circuit of 2 is disconnected The gist is to sequentially perform the second step of connecting the voltage application circuit and the third step of measuring the potential by the measurement circuit.

The invention according to claim 8 is that, in claim 7, the measurement circuit is connected to one of the electrodes (A) of the capacitor, and the third step continues the state of the second step. The gist is to measure the potential by the measurement circuit.
The invention according to claim 9 is the method according to claim 7, wherein the measurement circuit is connected to the other electrode (B) of the capacitor, and the third step includes the voltage application circuit and the second ground. The gist is to measure the potential by the measurement circuit after disconnecting the circuit and connecting the first ground circuit.

A tenth aspect of the present invention is that, in the seventh aspect, the first ground circuit is constituted by a first logic circuit element having an output connected to one electrode (A) of the capacitor, and the voltage The application circuit and the second ground circuit use a touch sensor configured by a second logic circuit element whose output is connected to the other electrode (B) of the capacitor, and the first step includes The output of the first logic circuit element and the output of the second logic circuit element are set to a low level, and the second step sets the output of the first logic circuit element to a high impedance and the second logic circuit. The gist is to set the output of the element to a high level.
The invention described in claim 11 is the measurement circuit according to claim 10, wherein the measurement circuit is connected to one of the electrodes (A) of the battery, and the third step continues the state of the second step. The gist is to measure the potential by the measurement circuit.
According to a twelfth aspect of the present invention, in the tenth aspect, the measurement circuit is connected to the other electrode (B) of the capacitor, and the third step is configured to output an output of the second logic circuit element. The gist is to measure the potential by the measurement circuit after setting the impedance to high and setting the output of the first logic circuit element to a low level.

  A gist of a thirteenth aspect of the present invention is that, in the seventh to twelfth aspects, the first step to the third step are repeatedly performed at a cycle of 1 ms to 7 ms.

  According to the touch sensor of the present invention, a detection electrode that is close to or in contact with a human body, a capacitor in which one electrode (A) is connected in series via the detection electrode and a resistor, the electrode (A) and a ground potential A first grounding circuit for connecting or disconnecting, a second grounding circuit for connecting or disconnecting the other electrode (B) of the capacitor and the ground potential, and a connection or disconnection of the electrode (B) and a DC power source. The touch sensor can be configured with a small number of components and a simple circuit configuration because it includes a voltage application circuit that performs measurement and a measurement circuit that is connected to any one electrode of the capacitor and measures the potential. The voltage application circuit, the first ground circuit, and the second ground circuit are each switched, and a control unit that determines the proximity or contact of the human body based on the potential measured by the measurement circuit is provided. A first step of disconnecting the voltage application circuit and connecting the first ground circuit and the second ground circuit; a second step of disconnecting the first ground circuit and the second ground circuit and connecting the voltage application circuit; Since the step and the third step of measuring the potential by the measurement circuit are sequentially performed, it is possible to detect a change in the capacitance generated in the detection electrode by extremely simple control and measurement processing, and the human body is in proximity or in contact It can be determined whether or not. Further, since it is not necessary to perform the first step to the third step at high speed, a change in potential caused by electrostatic induction of a finger or the like moving in proximity to or in contact with the detection electrode is detected and used for determination. It becomes possible. In addition, generation of high frequency noise can be suppressed, and electromagnetic interference to surrounding electronic devices can be greatly reduced.

The measurement circuit is connected to one of the electrodes (A) of the battery, and the control unit continues the state of the second step in the third step and measures the potential by the measurement circuit. Therefore, it is possible to measure a change in potential generated at the electrode of the battery by an extremely simple operation sequence.
The measurement circuit is connected to the other electrode (B) of the capacitor, and the control unit disconnects the voltage application circuit and the second ground circuit in the third step and also performs the first grounding. When the potential is measured by the measurement circuit after the circuit is connected, it is easy to measure a slight change in the potential generated in the electrode of the capacitor due to the proximity or contact of the human body.
The first ground circuit includes a first logic circuit element whose output is connected to one electrode (A) of the capacitor, and the voltage application circuit and the second ground circuit are connected to the capacitor. When the second logic circuit element whose output is connected to the other electrode (B) is configured, the touch sensor can be configured with an extremely small number of components. Accordingly, it is easy to configure a touch sensor including a plurality of detection electrodes.

It is preferable that the control unit repeatedly performs the first step to the third step with a period of 1 ms to 7 ms. Accordingly, it is easy to detect a change in potential caused by electrostatic induction of a finger or the like that moves in proximity to or in contact with the detection electrode, and use it for determination. In addition, generation of high frequency noise can be suppressed, and electromagnetic interference to surrounding electronic devices can be greatly reduced.
When the detection electrode is mounted on a vehicle and is a substantially rectangular sheet-like conductor, or a long plate-like or rod-like conductor, a large area or a long detection electrode is used. However, it is possible to suppress radiation of high-frequency noise from the detection electrode and reduce electromagnetic interference to surrounding on-vehicle electronic devices.

  According to the touch detection method of the present invention, it is possible to realize a touch detection method suitable for exhibiting the effect of the touch sensor.

The present invention will be further described in the following detailed description with reference to the drawings referred to, with reference to non-limiting examples of exemplary embodiments according to the present invention. Similar parts are shown throughout the several figures.
It is a block diagram showing the structure of a touch sensor. It is a block diagram showing another structure of a touch sensor. It is a circuit diagram showing the example which comprises the 1st grounding circuit of a touch sensor, a 2nd grounding circuit, and a voltage application circuit by a logic circuit element. It is a figure which shows the operation | movement step performed by switching each the voltage application circuit of the touch sensor shown in FIG. 1, a 1st ground circuit, and a 2nd ground circuit. FIG. 3 is a diagram illustrating operation steps performed by switching a voltage application circuit, a first ground circuit, and a second ground circuit of the touch sensor illustrated in FIG. 2. 3 is a time chart for explaining the operation of the touch sensor shown in FIG. 1. 3 is a time chart for explaining the operation of the touch sensor shown in FIG. 2. It is a block diagram showing the Example of this touch sensor. It is a block diagram showing the Example of the touch sensor comprised including a some detection electrode. It is a time chart for demonstrating operation | movement of the Example shown in FIG. It is a schematic diagram showing operation | movement of a finger etc. which move in proximity to or in contact with a detection electrode. (A) represents the change of the electric potential of the electrode of a capacitor | condenser when a finger etc. are moved in proximity to or in contact with a detection electrode, (b) is the figure showing the operation | movement which repeats each step of this touch sensor. It is a time chart showing that a change in potential due to capacitance generated when a human body approaches or comes into contact with a touch sensor and a change in potential due to electrostatic induction are measured together. It is a table | surface showing the result of having measured the change (change by electrostatic capacitance and change by electrostatic induction) of the electric potential of the electrode which arises when a measurement period is changed and a human body approaches or contacts. It is a schematic diagram showing the example of a touch sensor provided with a long or substantially rectangular detection electrode. It is a flowchart which shows the example of the touch detection method.

  The items shown here are for illustrative purposes and exemplary embodiments of the present invention, and are the most effective and easy-to-understand explanations of the principles and conceptual features of the present invention. It is stated for the purpose of providing what seems to be. In this respect, it is not intended to illustrate the structural details of the present invention beyond what is necessary for a fundamental understanding of the present invention. It will be clear to those skilled in the art how it is actually implemented.

(Configuration of touch sensor)
As shown in FIGS. 1 and 2, the touch sensor of the present invention includes a detection electrode 2 that is close to or in contact with a human body. The electrostatic capacity Cx represents the sum of the electrostatic capacity generated between the detection electrode 2 and the ground (ground), and when a human body is close to or in contact with the detection electrode 2, the electrostatic capacity Cx is between the detection electrode 2 and the ground. The capacitance increases due to the intervening human body.
The touch sensor (1a, 1b) includes a capacitor 3 to which one electrode A is connected in series via the detection electrode 2 and the resistor R1, and an electrode A that connects or disconnects the electrode A of the capacitor 3 and the ground potential. Voltage application for connecting or disconnecting the first ground circuit 4, the second ground circuit 5 for connecting or disconnecting the other electrode B of the capacitor 3 and the ground potential, and the electrode B of the capacitor 3 and the DC power source (Vcc). A circuit 6, a measurement circuit 7 connected to any one of the electrode A and the electrode B of the battery 3 and measuring the potential of the electrode, and a control unit 8 are provided. In the touch sensor 1a, the measurement circuit 7 is connected to the electrode A of the battery 3, and in the touch sensor 1b, the measurement circuit 7 is connected to the electrode B of the battery 3. The control unit 8 controls the voltage application circuit 6, the first ground circuit 4, and the second ground circuit 5 to be connected or disconnected, and the potential of the electrode A or the electrode B by the measurement circuit 7 at a predetermined timing. And the presence or absence of a human body approaching or contacting the detection electrode 2 is determined based on the measured value.

  When the touch sensors (1a, 1b) are mounted on a vehicle, necessary power is supplied to each part of the touch sensor by a power source (not shown) that receives power from a battery of the vehicle. The connection to the ground (grounding) can be a vehicle body or an electrical connection to the vehicle body.

The detection electrode 2 is a conductor disposed so that a human body is close to or in contact with the surface thereof, and the shape, size, structure and the like are not particularly limited. For example, the conductor may be a size that can be touched with a finger, a planar conductor having a larger area than the palm, or a long plate-like or rod-like conductor. May be. The material of the conductor is not particularly limited, and a conductive cloth or the like may be used in addition to the metal.
The “proximity” of the human body to the detection electrode 2 includes not only a form in which a palm or a finger is brought close to the surface of the detection electrode but also a form in which the human body is in contact with an insulator covering the surface of the detection electrode. “Contact” refers to a form in which the human body directly contacts the surface of the detection electrode.

The battery 3 has a known capacitance between both electrodes (A, B). One electrode A of the battery 3 is connected to the detection electrode 2 through a resistor R1 in series. The capacitance of the capacitor 3 and the resistance value of the resistor R1 may be appropriately designed according to conditions such as the size of the detection electrode, measurement time, and accuracy. For example, the capacitance of the capacitor 3 can be several tens of pF to several thousand pF, and the resistance value of the resistor R1 can be several hundred Ω to several tens of kΩ.
In addition, the electrode A of the battery 3 is connected to the first ground circuit 4. The first ground circuit 4 is grounded from the electrode A through a resistor R2 and a switch SW1a in series. The resistance value of the resistor R2 can be set to an appropriate value (for example, 0Ω to several kΩ). When the switch SW1a is connected (turned on), the electrode A of the capacitor 3 is connected to the ground potential (Gnd) via the resistor R2, and when the switch SW1a is disconnected (off and The electrode A and the ground potential are disconnected.

The other electrode B of the battery 3 is connected to the second ground circuit 5 and the voltage application circuit 6.
The second ground circuit 5 is a circuit that connects the electrode B of the battery 3 and the ground potential (Gnd) via the switch SW2a. When the switch SW2a is in the connected state (on), the electrode B is electrically connected to the ground potential, and when the switch SW2a is in the disconnected state (off), the electrode B is disconnected from the ground potential.
The voltage application circuit 6 is a circuit that connects the electrode B of the battery 3 and the DC power supply (Vcc) via the switch SW2b. When the switch SW2b is in the connected state (on), the DC power source Vcc is applied to the electrode B, and when the switch SW2b is in the disconnected state (off), the electrode B and the DC power source Vcc are disconnected. It is assumed that the switches SW2a and SW2b are not turned on at the same time.

  The measurement circuit 7 is connected to the electrode A of the battery 3 in the touch sensor 1a shown in FIG. 1, and is connected to the electrode B of the battery 3 in the touch sensor 1b shown in FIG. The measurement circuit 7 is a circuit that converts the potential of the electrode of the connected capacitor 3 into a digital value. An AD converter (ADC) can be used as the measurement circuit 7. In that case, the reference voltage Vref can be applied in order to optimize the conversion range of the AD converter corresponding to the potential range to be measured. Further, the measurement circuit 7 may be configured by a comparator or the like that compares the potential of the electrode with a predetermined reference potential. The measurement circuit 7 sends the measurement value (or comparison result) to the control unit 8.

The control unit 8 controls the switches provided in the first ground circuit 4, the second ground circuit 5, and the voltage application circuit 6, respectively, and performs measurement by the measurement circuit 7 at a predetermined timing. The measurement value (or comparison result) is input. Since the measured value is a value corresponding to the electrostatic capacitance Cx generated in the detection electrode 2, the control unit 8 performs processing such as calculation and comparison based on the measured value, whereby the human body to the detection electrode 2 is processed. It is configured to determine whether there is proximity or contact.
The processing of the control unit 8 may be realized by either hardware or software, and preferably a microcontroller (microcomputer) including a CPU, a memory (ROM, RAM, etc.), an input / output circuit, etc., not shown. Further, it can be configured by providing peripheral circuits such as an input / output interface. Alternatively, a programmable logic circuit, a gate array, or other logic circuit may be used. The microcontroller or the like may incorporate the measurement circuit, the first ground circuit, the second ground circuit, a voltage application circuit, and the like.
In addition, the control unit 8 is electrically connected to various devices (in the example of the in-vehicle device, an interior light, an interior illumination, an automatic opening / closing window, a radio, an air conditioner, etc.), and has determined that the human body is in proximity or in contact. In such a case, it can be configured to output a proximity detection signal for performing the determination or an operation based on the determination to the devices.

  The switches SW1a, SW2a, SW2b may be configured using semiconductor logic circuit elements. The first ground circuit 4 is composed of a first logic circuit element whose output is connected to the electrode A of the capacitor 3, and the voltage application circuit 6 and the second ground circuit 5 are the other of the capacitor 3. The second logic circuit element having the output connected to the electrode B of the second electrode can be configured. An example of this configuration is shown in FIG. In this touch sensor 11a, the measurement circuit 7 is connected to the electrode A of the capacitor 3. However, as described above, the touch sensor (11b) may be configured by connecting the measurement circuit 7 to the electrode B side of the capacitor 3. Good.

  In the touch sensor 11a shown in FIG. 3, the first ground circuit 41 is configured by connecting the output of the first logic circuit element 411 to the electrode A of the battery 3 via the resistor R2. The logic circuit element 411 includes a three-state output circuit. For example, the logic circuit element 411 can output when the control signal en4 is “1”. When the input signal d4 is “1”, the logic circuit element 411 has a high level (Vcc level) voltage and input signal. When d4 is “0”, a low level (0 V) voltage can be output. In this case, when the control signal en4 is “0”, the output circuit of the logic circuit element 411 is in a high impedance state (High-impedance). That is, the output of the logic circuit element 411 is at a low level when the control signal en4 = 1 and the input signal d4 = 0, and corresponds to a state in which the switch SW1a is turned on. On the other hand, when the control signal en4 = 0, the output becomes high impedance, which corresponds to the state where the switch SW1a is turned off. The signals en4 and d4 can be output by the control unit 81.

  Further, the voltage application circuit 61 and the second ground circuit 51 of the touch sensor 11 a are configured by connecting the output circuit of one three-state output element (second logic circuit element) 611 to the electrode B of the battery 3. be able to. Similarly to the above, the logic circuit element 611 can output, for example, when the control signal en6 is “1”, and when the input signal d6 is “1”, the high-level (Vcc level) voltage and the input signal d6 are In the case of “0”, a low level (0 V) voltage can be output. When the control signal en6 is “0”, the output circuit of the logic circuit element 611 is in a high impedance state. As a result, the output of the logic circuit element 611 is low when the control signal en6 = 1 and the input signal d6 = 0, and this corresponds to a state in which the switch SW2a is on and the switch SW2b is off. On the other hand, when the control signal en6 = 1 and the input signal d6 = 1, the output is at a high level, corresponding to a state in which the switch SW2a is turned off and the switch SW2b is turned on. Further, when the control signal en6 = 0, the output becomes high impedance, which corresponds to a state where both the switches SW2a and SW2b are turned off. The signals en6 and d6 can be output by the control unit 81.

(Touch sensor operation)
The first ground circuit (4, 41), the second ground circuit (5, 51), and the voltage application circuit (6, 61) included in the touch sensor (1a, 1b, 11a, 11b) are connected to the control unit (8 81), the control can be performed as shown in FIG. 4 or FIG. Here, on (connection) and off (disconnection) of the switches SW1a, SW2a, and SW2b are controlled to the states corresponding to the first logic circuit element 411 and the second logic circuit element 611 as described above. be able to.

FIG. 4 shows control in the touch sensor 1a or 11a. First, in the first step, the voltage application circuit is disconnected by turning off the switch SW2b, and the first ground circuit and the second ground circuit are connected by turning on the switch SW1a and the switch SW2a. That is, the electrode A and the electrode B of the battery 3 are connected to the ground potential.
Next, in the second step, the switch SW1a and the switch SW2a are turned off to disconnect the first ground circuit and the second ground circuit, and the switch SW2b is turned on to connect the voltage application circuit. . That is, the electrode A of the capacitor 3 is disconnected from the ground, and the electrode B is connected to the power supply (Vcc) level.
In the subsequent third step, the state of the second step is continued as it is. In the state of the third step, the control unit (8, 81) measures the potential of the electrode A of the battery 3 using the measurement circuit 7.

FIG. 5 shows control in the touch sensor 1b or 11b. The first step and the second step are the same as in the case of the touch sensor 1a or 11a.
In the subsequent third step, the voltage application circuit and the second ground circuit are disconnected by turning off the switches SW2a and SW2b, and the first ground circuit is connected by turning on the switch SW1a. That is, the electrode A of the battery 3 is connected to the ground potential, and the electrode B is disconnected from both the power supply (Vcc) and the ground potential.
In the state of the third step, the control unit (8, 81) measures the potential of the electrode B of the battery 3 using the measurement circuit 7.

  Examples of the operation sequence of the touch sensor are shown in FIGS. In these figures, the voltage V1 applied to the electrode A portion of the capacitor 3 by the first ground circuit, the voltage V2 applied to the electrode B portion of the capacitor 3 by the second ground circuit and the voltage applying circuit, This represents changes in the potential VA and the potential VB of the electrode B part. Periods T1, T2, and T3 represent the states of the first step, the second step, and the third step, respectively. Each time of the periods T1, T2, and T3 may be set as appropriate, and may be, for example, about several μs to several ms. The period T1 may be a period for discharging at least the capacitor 3 and the unknown capacitance Cx, but the state of the first step may be continued while the measurement operation (second step, third step) is not performed. it can. Further, the period T3 may be a time sufficient to measure at least the potential of the electrode.

FIG. 6 shows operations of the touch sensors 1a and 11a. In the period T1 (first step), the voltage V1 and the voltage V2 are set to 0V, so that the electric charges of the capacitor 3 and the unknown capacitance Cx are discharged, and the potential VA of the electrode A portion of the capacitor 3 becomes 0V.
Next, in period T2 (second step), since the electrode A part is cut off from the ground, the electrode A part (V1) is brought into a high impedance state, and Vcc is applied to the electrode B part (V2). Thereby, each electrostatic capacity is charged with time by a circuit in which the capacitor 3, the resistor R1, and the capacitance Cx are connected in series. The potential VA of the electrode A portion approaches the next value determined by the capacitor 3 (capacitance Cs) and the unknown capacitance Cx (capacitance Cx) with time.
VA = Vcc−ΔVa, ΔVa = (Cx / (Cs + Cx)) Vcc
Since the period T2 can be sufficiently longer than the time constant of charging determined by Cs, Cx, and the resistor R1, the charging voltage of the capacitor 3 at the end of the period T2 (the voltage between the electrode A and the electrode B) is as described above. ΔVa can be set.

  In the period T3 (third step), the above-described state can be continued and the potential VA of the electrode A portion can be input to the measurement circuit 7. Therefore, if the value of the potential VA is measured at the timing M within the period T3, the value of ΔVa can be known, and the capacitance of the unknown capacitance Cx can be obtained.

FIG. 7 shows operations of the touch sensors 1b and 11b. The operations in the period T1 (first step) and the period T2 (second step) are the same as those of the touch sensors 1a and 11a.
In period T3 (third step), when the electrode B part (V2) is cut off from Vcc to be in a high impedance state and the electrode A part (V1) is connected to 0 V, the charge accumulated in the capacitance Cx is the first charge. It is discharged by the ground circuit. Since the capacitance of the capacitance Cx is small, the time constant of discharge is small, and the potential VA of the electrode A portion of the battery 3 is quickly brought to 0V by the discharge. Further, since the electrode B portion of the battery 3 is in a high impedance state, the charge accumulated in the battery 3 is retained. That is, since the charging voltage ΔVa of the battery 3 is held, the potential VB of the electrode B portion becomes the value of ΔVa.
In this state, the potential VB of the electrode B part can be input to the measurement circuit 7. Therefore, if the potential VB is measured at the timing M within the period T3, the value of ΔVa can be known, and the capacitance of the unknown capacitance Cx can be obtained.

  As an example, the capacitance of the capacitor 3 is 500 pF, the resistance value of the resistor R1 is 10 kΩ, and the power supply voltage Vcc is 5V. Capacitance Cx is about 30 pF when the human body is in proximity or contact, and about 10 pF when not in proximity. In this case, the potential ΔVa of the electrode B portion measured at the timing M is about 0.10 V when the human body is not in proximity, and is about 0.28 V when the human body is in proximity or contact. Therefore, the proximity or contact of the human body can be determined by a method such as comparing this measured value with a predetermined reference value (for example, 0.2 V).

(Touch detection method)
The touch detection method of the touch sensor is shown in the flowchart of FIG. This process may be executed by the control unit. FIG. 16 shows a detection method in the touch sensors 1b and 11b. In this figure, SW1a, SW2a, and SW2b represent switches provided in the first ground circuit, the second ground circuit, and the voltage application circuit, respectively.

First, the switch SW2b is turned off (disconnected), and the switches SW1a and SW2a are turned on (connected) (S10). As a result, the state of the first step is established, and the electrodes A and B of the capacitor 3 are connected to the ground potential, so that the charges of the capacitor 3 and the capacitance Cx are discharged. Then, it waits for a predetermined time, that is, the elapse of the period T1 (S11).
Next, in the second step, the switch SW1a and the switch SW2a are turned off, and the switch SW2b is turned on (S20). Thereby, the electrode A of the capacitor 3 is disconnected from the ground, and the electrode B is set to the power supply (Vcc) level, so that the capacitor 3 and the capacitance Cx are charged with time. And it waits for progress of the predetermined time, ie, the said period T2, (S21).

  Subsequently, the switches SW2a and SW2b are turned off, and the switch SW1a is turned on (S30). As a result, the state of the third step is established, and the electrode A of the battery 3 is connected to the ground potential, and the electrode B is disconnected from both the power supply (Vcc) and the ground, so that the potential of the electrode B portion becomes the ΔVa. . Then, after the third step is started, the elapse of a predetermined time t3 is waited (S31). The time t3 can be an appropriate time after the start of the third step. After the elapse of time t3, the measurement circuit measures the potential ΔVa of the electrode B (S40).

  When the touch sensor 1a or 11a is used, the control (S30) for setting the third step is not necessary. Instead of measuring the potential of the electrode B (S40), the potential of the electrode A (Vcc−ΔVa) may be measured by a measurement circuit.

  The proximity or contact of the human body to the detection electrode is determined from the potential ΔVa obtained from the measured value (S50). By periodically repeating the above processing, a change in the capacitance of the capacitance Cx can also be detected. Further, when a plurality of detection electrodes are provided, the above processing can be performed for each detection electrode. The proximity or contact of the human body with the detection electrode can be determined, for example, by comparing the measured value with a predetermined reference value. Further, the reference value may be corrected by the result of measurement repeated periodically.

(Example)
The touch sensor and the touch detection method can be implemented in various forms. For example, as with the touch sensor 12 shown in FIG. 8, if a microcontroller or the like 82 in which the output port 1 (42), the output port 2 (62 (52)), and the AD converter 72 are incorporated is used, very few parts are used. Thus, a touch sensor can be configured easily. In this example, output port 1 (42) is used as the first logic circuit element, and output port 2 (62 (52)) is used as the second logic circuit element. With this configuration, the same operation as that of the touch sensor 1b described in FIG. 2 can be performed.
Further, the AD converter 72 may be connected to the terminal 91 part or the electrode A part of the battery 3. In that case, the same operation as the touch sensor 1a described in FIG. 1 can be performed.

It is also easy to configure a touch sensor having a plurality of detection electrodes. For example, the touch sensor 121 shown in FIG. 9 includes six detection electrodes 2a to 2f. For each detection electrode, the output ports 1a to 1f (42a to 42f) and the output ports 2a to 2f (62a to 62f) are provided. And the potentials of the electrodes B of the capacitors 3a to 3f, that is, the terminals 92a to 92f can be measured using the AD converters a to f (72a to 72f).
FIG. 10 shows an operation of measuring the potential sequentially for the detection electrodes 2a to 2f with the above configuration. In FIG. 10, VAa to VAf represent the potentials of the electrodes A of the capacitors 3a to 3f, and VBa to VBf represent the potentials of the electrodes B of the capacitors 3a to 3f.
First, with respect to the detection electrode 2a, the output port 1a (42a) and the output port 2a (62a) are controlled in the same manner as V1 and V2 shown in FIG. 7, and the potential of the terminal 92a portion using the AD converter ADCa (72a). Can be measured. By measuring the potential VBa at the predetermined timing Ma in the third step, it is possible to determine the proximity or contact of the human body to the detection electrode 2a. Similarly, the proximity or contact of the human body to each detection electrode can be determined by sequentially measuring the potentials VBb to VBf at the timings Mb to Mf for the detection electrodes 2b to 2f.
Further, the AD converters 72a to 72f shown in FIG. 9 may be connected to the terminals 91a to 91f or the electrodes A of the capacitors 3a to 3f, respectively. In that case, the operation similar to the operation of the touch sensor 1a described in FIG. 6 can be performed for each of the detection electrodes 2a to 2f.

  The touch sensor detects a change in capacitance generated in the detection electrode by periodically repeating the first step to the third step (see FIGS. 4 to 7), Can be determined whether or not they are close or in contact. Since the touch sensor does not need to repeatedly charge and discharge and accumulate its charge / discharge characteristics, it is not necessary to execute the first step to the third step at high speed, and the repetition cycle is also appropriate. be able to. As a result, this touch sensor not only can suppress the generation of high-frequency noise, but also detects a change in potential caused by electrostatic induction of a finger or the like that moves in proximity to or in contact with the detection electrode. It can be used.

Usually, the human body is in a charged state. Therefore, as shown in FIG. 11, when a finger or the like is moved close to the detection electrode 21 of the present touch sensor 14 or a finger or the like is slid on the insulating film covering the detection electrode 21, etc. Electrostatic induction occurs in the detection electrode 21. For example, in the touch sensor 14, when the output circuit of the port 1 (42) is set to high impedance and the output voltage of the port 2 (62) is set to Vcc (that is, a state corresponding to the T2), the electrostatic induction is performed. When it occurs, the potential VA of the electrode A of the battery 3 changes as shown in FIG. If the period during which the potential VA changes due to the electrostatic induction is T _X , Tx is actually about 100 ms (several tens of ms to 1 s).
FIG. 12 (b), in the from first step (T1) to the third step (T3) and a series of operations, view showing the operation of the touch sensor performing it repeatedly without interruption at a constant cycle T _C is there. That is, the T _C is the period to perform measurement of the potential VB. Therefore, by setting the longer and and the period T _C of the period of the second step (T2) appropriately, it is possible to detect the potential VA varying as shown in FIG. 12 (a) by electrostatic induction.

FIG. 13 is a diagram illustrating the potential of each part of the touch sensor 14 when the potential VA varies due to the electrostatic induction. Control of the output V1 of the port 1 and the output V2 of the port 2 from the first step T1 to the third step T3 is the same as the operation shown in FIG. In the period T2 of the second step, the potential VA of the electrode A of the battery 3 includes a change ΔVa due to charging of the capacitance (Cx) generated in the detection electrode 21 and a change ΔVi due to electrostatic induction. Will be added. As a result, the potential VB of the electrode B of the battery 3 in the third step T3 becomes (ΔVa + ΔVi), and fluctuation due to electrostatic induction can be detected.
Note that in the period T2 shown in FIG. 13, the potential VA of the electrode A is lower by ΔVi than the potential (Vcc−ΔVa) due to charging of the electrostatic capacitance indicated by the broken line due to electrostatic induction. As is apparent from FIG. 12A, the potential VA may rise above the potential (Vcc−ΔVa) due to electrostatic induction.

FIG. 14 is a table showing an example of measuring the potential VB, that is, (ΔVa + ΔVi) when the finger is moved close to the detection electrode using the touch sensor 14 (see FIG. 11). In the circuit of the touch sensor 14, the capacitance of the capacitor 3 was 500 pF, the resistor R1 was 10 kΩ, and the resistor R2 was 1 kΩ. Wherein by changing the repetition period _{T C} in the range of 0.1ms~10ms (ΔVa + ΔVi) value results of measurement of were as shown in Table.
Since the human body has a capacitance of 20 to 30 pF, a potential change (ΔVa) caused by the capacitance is about 0.2 to 0.3 V. As shown in Table, when the period _{T C} of 0.1ms for (.DELTA.Va + [Delta] Vi) measured value becomes 0.25 V, those not able to capture variations due to electrostatic induction component of ([Delta] Vi) it is conceivable that. When the period T _C was 1ms, it is clear that to include (.DELTA.Va + [Delta] Vi) measured value of 0.4V, and the variation due to electrostatic induction on the measurement value. Furthermore, if the period _{T C} is more than 7 ms, measurements of (.DELTA.Va + [Delta] Vi) it is no longer change significantly from 2.2V. For Longer periods T _C and thus impair the responsiveness of the touch sensor, from the measurement result, that the above repeating 1ms~7ms the period T _C is be preferred (more preferably 1 ms).
As described above, since large fluctuations appear in the electrode part of the battery 3 due to electrostatic induction of a finger or the like that moves in proximity to or in contact with the detection electrode, the control part performs measurement at each cycle Tc to thereby determine the electrode part. Can be used to determine whether the human body is in proximity or in contact.

  In addition, the touch sensor can be effectively applied to a case where the touch sensor is mounted on a vehicle and the size of the detection electrode is large. When the detection electrode is a sheet-like or plate-like conductor having a large area (regardless of shape, for example, a substantially rectangular or elliptical shape), or a long plate-like, sheet-like or rod-like conductor This is the case. As shown in FIG. 15, for example, the detection electrode 22 can be composed of a long conductor having a length (L) of 20 to 500 mm and a width (W) of 2 to 50 mm. Moreover, the detection electrode 22 can be comprised with the conductor of a wide area whose length (L) and width (W) are about 20-500 mm, respectively. Even when such a long detection electrode or a detection electrode with a large area is used, this touch sensor supplies a high-frequency signal to the detection electrode or increases the capacitance generated in the detection electrode at high speed. Therefore, it is not necessary to charge / discharge, etc., so that it is possible to suppress unnecessary high-frequency noise emission.

  Due to the above features, the touch sensor can be suitably used as a vehicle-mounted touch sensor. The present invention can be applied as a touch sensor for operating various in-vehicle electronic devices / devices such as lighting in automobiles, decorative panels, display panels, air conditioners, and seating determination devices. For example, by arranging the long detection electrode 22 in a console box or a glove box, the inside of the box can be illuminated when the palm or finger of an occupant approaches the detection electrode 22. In addition, for example, by arranging a detection electrode having a large area on the ceiling, a room lamp can be turned on when a palm or a finger approaches the detection electrode.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention depending on the purpose and application.

  1a, 1b, 11a, 11b, 12, 121, 14, 15; touch sensor, 2, 21, 22; detection electrode, 3; capacitor, 4, 41; first ground circuit, 411; first logic circuit element 5, 51; second ground circuit, 6, 61; voltage application circuit, 611; second logic circuit element, 7, 72; measurement circuit (AD converter), 8, 81; control unit, Cx; unknown Capacitance.

Claims (13)

A touch sensor for detecting proximity or contact of a human body,
A sensing electrode that is close to or in contact with the human body;
A capacitor in which one electrode (A) is connected in series via the detection electrode and a resistor;
A first ground circuit for connecting or disconnecting one electrode (A) of the capacitor and a ground potential;
A second ground circuit for connecting or disconnecting the other electrode (B) of the capacitor and the ground potential;
A voltage application circuit for connecting or disconnecting the other electrode (B) of the capacitor and a DC power source;
A measurement circuit connected to any one electrode of the capacitor and measuring the potential of the electrode;
A controller that switches between the voltage application circuit, the first ground circuit, and the second ground circuit, respectively, and determines proximity or contact of a human body based on a potential measured by the measurement circuit;
With
The control unit disconnects the voltage application circuit and connects the first ground circuit and the second ground circuit, and disconnects the first ground circuit and the second ground circuit. And a second step of connecting the voltage application circuit and a third step of measuring a potential by the measurement circuit in order. The measurement circuit is connected to one of the electrodes (A) of the battery,
The touch sensor according to claim 1, wherein the control unit continues the state of the second step in the third step and measures the potential by the measurement circuit. The measurement circuit is connected to the other electrode (B) of the capacitor,
2. The control unit according to claim 1, wherein, in the third step, the voltage application circuit and the second ground circuit are disconnected and the first ground circuit is connected, and then the potential is measured by the measurement circuit. Touch sensor. The first ground circuit is constituted by a first logic circuit element having an output connected to one electrode (A) of the capacitor,
The said voltage application circuit and said 2nd ground circuit are comprised by the 2nd logic circuit element by which the output was connected to the other electrode (B) of the said electrical storage device. Touch sensor.   The touch sensor according to claim 1, wherein the control unit repeatedly performs the first step to the third step at a cycle of 1 ms to 7 ms.   The touch sensor according to claim 1, wherein the touch sensor is mounted on a vehicle and the detection electrode is a substantially rectangular sheet-like conductor, or a long plate-like or rod-like conductor. A touch detection method for detecting proximity or contact of a human body,
A sensing electrode that is close to or in contact with the human body;
A capacitor in which one electrode (A) is connected in series via the detection electrode and a resistor;
A first ground circuit for connecting or disconnecting one electrode (A) of the capacitor and a ground potential;
A second ground circuit for connecting or disconnecting the other electrode (B) of the capacitor and the ground potential;
A voltage application circuit for connecting or disconnecting the other electrode (B) of the capacitor and a DC power source;
A measurement circuit connected to any one electrode of the capacitor and measuring the potential of the electrode;
Using a touch sensor comprising
Disconnecting the voltage application circuit and connecting the first ground circuit and the second ground circuit;
A second step of disconnecting the first ground circuit and the second ground circuit and connecting the voltage application circuit;
A third step of measuring a potential by the measurement circuit;
The touch detection method characterized by performing sequentially. The measurement circuit is connected to one of the electrodes (A) of the battery,
The touch detection method according to claim 7, wherein in the third step, the state of the second step is continued and a potential is measured by the measurement circuit. The measurement circuit is connected to the other electrode (B) of the capacitor,
The touch detection method according to claim 7, wherein in the third step, the voltage is measured by the measurement circuit after the voltage application circuit and the second ground circuit are disconnected and the first ground circuit is connected. The first ground circuit includes a first logic circuit element whose output is connected to one electrode (A) of the capacitor, and the voltage application circuit and the second ground circuit are connected to the capacitor. Using a touch sensor composed of a second logic circuit element whose output is connected to the other electrode (B),
The first step sets the output of the first logic circuit element and the output of the second logic circuit element to a low level,
The touch detection method according to claim 7, wherein the second step sets the output of the first logic circuit element to a high impedance and sets the output of the second logic circuit element to a high level. The measurement circuit is connected to one of the electrodes (A) of the battery,
The touch detection method according to claim 10, wherein in the third step, the state of the second step is continued and the potential is measured by the measurement circuit. The measurement circuit is connected to the other electrode (B) of the capacitor,
11. The third step comprises measuring the potential by the measurement circuit after setting the output of the second logic circuit element to high impedance and setting the output of the first logic circuit element to low level. Touch detection method.   The touch detection method according to claim 7, wherein the first step to the third step are repeatedly performed at a cycle of 1 ms to 7 ms.

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