Electrostatic input device and electrostatic detection device

Abstract

Provided are: an electrostatic input device with which the accuracy of determination in failure determination can be improved by reducing an output sensitivity of electrostatic capacitance when performing failure determination on a sensor electrode; and an electrostatic detection device.　The electrostatic input device comprises: a sensor electrode provided on a back side of an operation surface; a measurement circuit connected to the sensor electrode; a determination unit that, on the basis of an electrostatic capacitance of the sensor electrode obtained from an output of the measurement circuit, performs failure determination for determining the failure of the sensor electrode, and that performs an operation determination for determining the contact or the approach of an object with respect to the operation surface; and a sensitivity setting unit that sets a first output sensitivity of the measurement circuit when the determination unit is performing the failure determination to be lower than a second output sensitivity of the measurement circuit when the determination unit is performing the operation determination.

Description

Electrostatic input device and electrostatic detection device

[0001] The present disclosure relates to electrostatic input devices and electrostatic detection devices.

[0002] Conventionally, there has been a touch panel system that has a projected capacitive touch panel and a touch panel controller that receives signals from the touch panel and detects touch operations by a user based on the received signals, where the touch panel controller detects touch operations by integrating the received signals from the touch panel multiple times and comparing the integrated signal value with a touch operation detection threshold, and has a touch operation sensitivity change means that changes the sensitivity of the touch operations detected on the touch panel, and the touch operation sensitivity change means changes the sensitivity of the touch operations by increasing or decreasing the number of times the received signals are integrated (see, for example, Patent Document 1).

[0003] JP 2012-248035 A

[0004] Incidentally, in an electrostatic input device that uses electrostatic capacitance, such as a touch panel system, when determining whether a sensor electrode has failed, it may not be possible to determine whether the increase in capacitance is due to a failure such as a short circuit in the sensor electrode, or whether the increase in capacitance is due to contact with a part of the body larger than the fingertips, such as the palm or arm.

[0005] However, conventional touch panel systems do not change the sensitivity of touch operations to enable such a determination.

[0006] Therefore, the object is to provide an electrostatic input device and an electrostatic detection device that can improve the accuracy of fault determination by reducing the output sensitivity of the electrostatic capacitance when determining faults in the sensor electrodes.

[0007] An electrostatic input device according to an embodiment of the present disclosure includes a sensor electrode provided on the back side of an operation surface, a measurement circuit connected to the sensor electrode, a determination unit that performs a failure determination to determine a failure of the sensor electrode based on the capacitance of the sensor electrode obtained from the output of the measurement circuit, and also performs an operation determination to determine whether an object has contacted or approached the operation surface, and a sensitivity setting unit that sets a first output sensitivity of the measurement circuit when the determination unit is performing the failure determination to be lower than a second output sensitivity of the measurement circuit when the determination unit is performing the operation determination.

[0008] By reducing the output sensitivity of the capacitance when determining whether a sensor electrode has failed, an electrostatic input device and an electrostatic detection device can be provided that can improve the accuracy of determining whether a sensor electrode has failed.

[0009] FIG. 1 is a diagram showing an example of the configuration of a steering wheel provided with an operation unit of an electrostatic input device of an embodiment. FIG. 2 is a diagram showing an electrostatic input device 100 of an embodiment. FIG. 3 is a diagram explaining operation determination and failure determination in an electrostatic input device for comparison. FIG. 4 is a diagram explaining operation determination and failure determination in an electrostatic input device for comparison. FIG. 5 is a diagram explaining an example of operation determination and failure determination in an electrostatic input device of an embodiment. FIG. 6 is a diagram explaining an example of operation determination and failure determination in an electrostatic input device of an embodiment. FIG. 7 is a diagram showing an example of operation determination and failure determination in an electrostatic input device of an embodiment. FIG. 8 is a diagram showing an example of operation determination for a sensor electrode of an electrostatic input device of an embodiment. FIG. 9 is a flowchart showing an example of processing executed by an information processing unit of an electrostatic input device of an embodiment.

[0010] Hereinafter, an embodiment to which the electrostatic input device and electrostatic detection device of the present disclosure are applied will be described.

[0011] <Embodiment> Fig. 1 is a diagram showing an example of the configuration of a steering wheel 10 provided with an operation unit 110 of an electrostatic input device 100 according to an embodiment. The steering wheel 10 is disposed in the driver's seat of a vehicle, and the operation unit 110 is provided on a spoke. Fig. 1 shows, as an example, a state in which the operation unit 110 is operated with the fingertips FT of a user's right hand (the thumb in Fig. 1 is an example). The fingertips FT are an example of an object. Below, as an example, a form in which operation is performed with the fingertips FT will be described, but operation is also possible with other fingertips than the fingertips FT.

[0012] A vehicle is an automobile that can travel on roads using an engine and / or a motor as a power source. The vehicle may be equipped with various levels of automated driving functions defined by, for example, the Society of Automotive Engineers (SAE) International of the United States.

[0013] As shown in an enlarged view, the operation unit 110 has, as an example, six sensor electrodes 111 to 116. In the enlarged view showing the sensor electrodes 111 to 116, the covers that cover the sensor electrodes 111 to 116 are omitted. The sensor electrodes 111 to 116 are an example of a plurality of sensor electrodes. Here, the areas where the sensor electrodes 111 to 116 are arranged are marked with (1) to (6). Note that, as an example, a configuration in which the operation unit 110 has six sensor electrodes 111 to 116 will be described, but the operation unit 110 only needs to include at least one sensor electrode.

[0014] The operation unit 110 also includes a voltage output unit that applies AC power of a predetermined frequency to the sensor electrodes 111 to 116 when the determination unit 123 performs operation determination and fault determination, but this is not shown here. The drive control of the voltage output unit is performed by a main control unit 121 of the control device 120, which will be described later.

[0015] The sensor electrodes 111 to 116 are housed in a housing 110A, covered by a cover 110B, and provided on the spokes of the steering wheel 10. The surface of the cover 110B is an operation surface 110B1 that can be operated by the user with the fingertips FT, etc. The sensor electrodes 111 to 116 are located on the back side of the operation surface 110B1.

[0016] In this example, the surface of resin cover 110B that covers sensor electrodes 111 to 116 is operation surface 110B1, but if sensor electrodes 111 to 116 are covered with a protective film, a protective coating film, or the like, the surface of the protective film, the protective coating film, or the like is operation surface 110B1. "Sensor electrodes 111 to 116 are located on the back side of operation surface 110B1" means that sensor electrodes 111 to 116 are not exposed but are covered by cover 110B, a protective film, a coating film, or the like.

[0017] When the user operates one of the areas (1) to (6) on the operation surface 110B1 with the fingertip FT or the like, capacitance is detected through the sensor electrode (one of 111 to 116) corresponding to the operated area.

[0018] The sensor electrodes 111-116 are arranged in a matrix of two rows and three columns. The sensor electrodes 111-116 are, for example, electrodes made of metal foil, metal plate, or conductive film, and are connected to a control device (not shown) via wiring, cables, or the like. The capacitance between the sensor electrodes 111-116 and the fingertip FT (see FIG. 1) varies depending on the proximity (distance) of the fingertip FT to the sensor electrodes 111-116. Because the sensor electrodes 111-116 are actually covered by the cover 110B, the capacitance between the sensor electrodes 111-116 and the fingertip FT (see FIG. 1) varies depending on the distance between the operation surface 110B1 and the fingertip FT in contact with or in proximity to the operation surface 110B1.

[0019] The sensor electrodes 111 to 116 are used, for example, to operate various electrical devices in the vehicle. By touching the surface of any of the sensor electrodes 111 to 116 of the cover 110B with a fingertip or the like, the desired electrical device in the vehicle can be operated. Functions of electrical devices that can be operated with the sensor electrodes 111 to 116 include, for example, selecting a track or adjusting the volume of an audio system, selecting on-hook or end of a hands-free phone call, and setting the cruise control.

[0020] 2 is a diagram showing an electrostatic input device 100 according to an embodiment. The electrostatic input device 100 includes an operation unit 110 and a control device 120. The operation unit 110 has sensor electrodes 111 to 116 (see FIG. 1), which are omitted from FIG. 2. The electrostatic input device 100 detects touch operations using a self-capacitance system, for example. A touch operation is an operation in which a fingertip FT or the like comes into contact with areas (1) to (6) on an operation surface 110B1 of a cover 110B that covers the sensor electrodes 111 to 116.

[0021] Here, as an example, a description will be given of a case where the electrostatic input device 100 detects touch operations on the areas (1) to (6) on the operation surface 110B1. However, the electrostatic input device 100 may also detect proximity operations in proximity to the areas (1) to (6) without touching the operation surface 110B1.

[0022] <Control device 120> The control device 120 has a measurement circuit 120A and an information processing unit 120B. As an example, the control device 120 is an IC (Integrated Circuit) chip. Here, as an example, a configuration will be described in which the control device 120 is configured as an IC chip and has the measurement circuit 120A and the information processing unit 120B. However, the measurement circuit 120A may be provided outside the control device 120 configured as an IC chip.

[0023] <Measurement Circuit 120A> The measurement circuit 120A is an analog front end and is connected to the sensor electrodes 111 to 116. The measurement circuit 120A has an amplifier and an A / D (Analog to Digital) converter. The amplifier amplifies the current of the sensor electrodes 111 to 116. This increases the capacitance of the sensor electrodes 111 to 116. The A / D converter converts the increased capacitance into a digital value and outputs it.

[0024] The amplification factor (gain) of the amplifier included in the measurement circuit 120A is configured to be adjustable by the sensitivity setting unit 124 of the information processing unit 120B. Changing the amplification factor (gain) of the amplifier changes the output sensitivity of the measurement circuit 120A. Changing the output sensitivity of the measurement circuit 120A changes the numerical level of the capacitance (count value) detected by the capacitance detection unit 122 based on the output of the measurement circuit 120A, which is equivalent to changing the output sensitivity of the capacitance.

[0025] The operation unit 110 and the measurement circuit 120A, and the measurement circuit 120A and the information processing unit 120B are connected via wiring, cables, etc. The control device 120 is provided in the steering wheel 10, as an example, and is configured integrally with the operation unit 110. Note that, although a configuration in which the control device 120 is provided in the operation unit 110 and configured integrally with the operation unit 110 will be described here, the control device 120 may be configured separately from the operation unit 110 and may be provided inside the vehicle, outside the steering wheel 10.

[0026] <Information Processing Unit 120B> The information processing unit 120B of the control device 120 is connected to an ECU (Electronic Control Unit) 50 that controls electrical equipment via an in-vehicle network such as a Controller Area Network (CAN) or a Local Interconnect Network (LIN) installed in the vehicle. The ECU 50 is an electronic control device that controls the vehicle's audio, hands-free phone, cruise control, and other electrical equipment. Although one ECU 50 is shown in FIG. 2, multiple ECUs 50 may be connected to the control device 120.

[0027] The information processing unit 120B is realized by a computer including a central processing unit (CPU), random access memory (RAM), read only memory (ROM), an input / output interface, an internal bus, and the like.

[0028] The information processing unit 120B has a main control unit 121, a capacitance detection unit 122, a determination unit 123, a sensitivity setting unit 124, and a memory 125. The main control unit 121, the capacitance detection unit 122, the determination unit 123, and the sensitivity setting unit 124 are functional blocks representing the functions of the program executed by the control device 120. The memory 125 is a functional representation of the memory of the control device 120.

[0029] <Main Control Unit 121> The main control unit 121 is a processing unit that oversees the control processing of the information processing unit 120B, and executes processing other than the processing performed by the capacitance detection unit 122, the determination unit 123, and the sensitivity setting unit 124. For example, the main control unit 121 performs control processing to cause the voltage output unit of the operation unit 110 to apply AC power of N (N is an integer of 2 or more) types of frequencies to the sensor electrodes 111 to 116 when the determination unit 123 performs operation determination, and to apply AC power of M (M is a natural number less than N) types of frequencies to the sensor electrodes 111 to 116 when the determination unit 123 performs fault determination. Such control processing is drive control of the voltage output unit of the operation unit 110 performed by the main control unit 121.

[0030] <Capacitance Detection Unit 122> The capacitance detection unit 122 detects the capacitance of the sensor electrodes 111 to 116 (see FIG. 1) by integrating the output of the measurement circuit 120A, and transmits data representing count values ​​of the capacitance of each of the sensor electrodes 111 to 116 to the determination unit 123. By integrating the output of the measurement circuit 120A, the capacitance detection unit 122 can detect the capacitance of the sensor electrodes 111 to 116 while reducing the influence of noise and other factors contained in the output of the measurement circuit 120A. The capacitance of the sensor electrodes 111 to 116 detected by the capacitance detection unit 122 is represented by a count value. The count value is a digital value. The capacitance detection unit 122 detects the capacitance (count value) for each of the sensor electrodes 111 to 116.

[0031] When the determination unit 123 detects the capacitance of the sensor electrodes 111 to 116 when making a fault determination, the capacitance detection unit 122 detects the capacitance of the sensor electrodes 111 to 116 by integrating the output of the measurement circuit 120A a first number of integrations. When the determination unit 123 detects the capacitance of the sensor electrodes 111 to 116 when making an operation determination, the capacitance detection unit 122 detects the capacitance of the sensor electrodes 111 to 116 by integrating the output of the measurement circuit 120A a second number of integrations. The first number of integrations is less than the second number of integrations. This will be described in more detail later.

[0032] When the determination unit 123 performs a fault determination, the capacitance detection unit 122 outputs the capacitance detected for each of the sensor electrodes 111 to 116 to the determination unit 123 .

[0033] In addition, when the judgment unit 123 judges the operation, the capacitance detection unit 122 outputs to the judgment unit 123 a difference value ΔAD obtained by subtracting the capacitance detected when no operation is being performed on the sensor electrodes 111 to 116 from the capacitance detected when operation is being performed on the sensor electrodes 111 to 116.

[0034] <Determination Unit 123> The determination unit 123 performs a failure determination to determine whether the sensor electrodes 111 to 116 have a failure based on the count value of the capacitance of each of the sensor electrodes 111 to 116 transmitted from the capacitance detection unit 122, and also performs an operation determination to determine whether the fingertip FT has contacted areas (1) to (6) of the operation surface 110B1 based on the capacitance difference value ΔAD. The determination unit 123 selects the multiple sensor electrodes 111 to 116 one by one in order, and performs a failure determination and an operation determination for each of the sensor electrodes 111 to 116. This will be described in detail later.

[0035] The fault determination is, for example, a determination process for determining whether a short circuit (short-circuit fault) has occurred in each of the sensor electrodes 111 to 116. The determination unit 123 performs the fault determination by comparing the capacitance of the sensor electrodes 111 to 116 detected by the capacitance detection unit 122 with a fault determination threshold.

[0036] The operation determination is a determination process that determines whether a touch operation has been performed on any one of the sensor electrodes 111 to 116. The determination unit 123 performs operation determination by comparing the difference value ΔAD of the capacitance of the sensor electrodes 111 to 116 output from the capacitance detection unit 122 with an operation determination threshold, thereby determining whether the fingertip FT has approached any of the areas (1) to (6) on the operation surface 110B1.

[0037] When the electrostatic input device 100 detects a proximity operation instead of a touch operation, the operation determination performed by the determination unit 123 is a process of determining the proximity of the fingertip FT to the areas (1) to (6) on the operation surface 110B1. When the electrostatic input device 100 can detect a proximity operation in addition to a touch operation, the operation determination performed by the determination unit 123 is a process of determining the contact or proximity of the fingertip FT to the areas (1) to (6) on the operation surface 110B1.

[0038] The determination result of the determination unit 123 indicates which one of the sensor electrodes 111 to 116 has been touched. The determination result of the determination unit 123 is a detection result obtained by the electrostatic input device 100 as to which sensor electrode has been touched. The determination process performed by the determination unit 123 will be described later.

[0039] <Sensitivity Setting Unit 124> The sensitivity setting unit 124 sets the output sensitivity of the measurement circuit 120 A by outputting a sensitivity setting signal to the measurement circuit 120 A. More specifically, the sensitivity setting unit 124 sets the first output sensitivity of the measurement circuit 120 A when the determination unit 123 is performing a fault determination to be lower than the second output sensitivity of the measurement circuit 120 A when the determination unit 123 is performing an operation determination.

[0040] The first output sensitivity is an amplification factor at which the capacitance of the sensor electrodes 111 to 116 detected by the capacitance detection unit 122 is less than the failure determination threshold value even when the coupling between the sensor electrodes 111 to 116 and the object is maximized due to the object coming into contact with or approaching the operation surface 110B1 when the determination unit 123 performs a failure determination. Details of this will be described later.

[0041] <Memory 125> The memory 125 stores programs and data necessary for the information processing unit 120B to perform the determination process. The memory 125 stores data representing the count values ​​of the capacitance of each of the sensor electrodes 111 to 116, data generated by the determination unit 123 during the determination process, and the like.

[0042] The memory 125 also stores data representing the types M and N of frequencies of the AC power to be output to the voltage output unit of the operation unit 110, data representing the number of integrations (first number of integrations and second number of integrations) when detecting the capacitance of the sensor electrodes 111 to 116, and data representing the output sensitivity (first output sensitivity and second output sensitivity) of the measurement circuit 120A.

[0043] <Electrostatic Detection Device of the Embodiment> In this embodiment, an electrostatic input device 100 will be described, but by making the following changes to the device described as the electrostatic input device 100, it can be used as an electrostatic detection device.

[0044] In the electrostatic detection device of the embodiment, the sensor electrodes 111 to 116 do not need to be provided on the back side of the operation surface 110B1. The electrostatic detection device of the embodiment is a device that performs proximity determination to determine the proximity of an object to the sensor electrodes 111 to 116 instead of the operation determination of the electrostatic input device 100, and does not need to perform the operation determination performed by the electrostatic input device 100. Furthermore, the electrostatic detection device of the embodiment only needs to include at least one sensor electrode. As an example, the electrostatic detection device of the embodiment may be incorporated into any device that needs to determine the proximity of an object. For example, the electrostatic detection device may be incorporated into a tablet-type input device or ATM (Automatic Teller Machine) that is installed in a store, facility, etc. and used by an unspecified number of users.

[0045] <Operation Determination and Failure Determination in Comparative Electrostatic Input Device> Here, operation determination and failure determination in a comparative electrostatic input device will be described with reference to FIGS. 3A and 3B. FIG.

[0046] The comparative electrostatic input device does not include the sensitivity setting unit 124, and the output sensitivity of the measurement circuit 120A is set to the same value both when the judgment unit 123 is making a fault judgment and when the judgment unit 123 is making an operation judgment.

[0047] In addition, in the comparative electrostatic input device, the number of integrations for the capacitance detection unit 122 to detect the capacitance of the sensor electrodes 111 to 116 is set to the same number (a predetermined number) both when the judgment unit 123 makes a fault judgment and when it makes an operation judgment.

[0048] In addition, in the comparative electrostatic input device, the number of types of AC power frequencies to be applied to the sensor electrodes 111 to 116 in the voltage output section of the operation section 110 is set to the same number both when the judgment section 123 makes a fault judgment and when it makes an operation judgment.

[0049] 3A, the capacitance detected by the capacitance detection unit 122 when a touch operation is performed with the fingertip FT on the operation surface 110B1 in a case where there is no short circuit failure in any of the sensor electrodes 111 to 116 of the comparative electrostatic input device will be described. Also, as an example, the case where a touch operation is performed on the area (1) where the sensor electrode 111 is located will be described.

[0050] 3A, the horizontal axis represents the actual capacitance of the sensor electrode 111, and the vertical axis represents the capacitance (count value) of the sensor electrode 111 detected by the capacitance detection unit 122 by digitally converting the output of the measurement circuit 120A and integrating it a predetermined number of times when the actual capacitance of the sensor electrode 111 is the value shown on the horizontal axis. The predetermined number of times is, for example, 128 times.

[0051] The vertical axis indicates the short circuit fault determination threshold THs used to determine whether the sensor electrode 111 has a short circuit fault, and the measurement range upper limit RU of a comparative electrostatic input device. The measurement range upper limit RU is determined by the specifications of the IC chip used as the control device 120, and the difference between it and the capacitance C2 (described later) is small, and the difference between it and the short circuit fault determination threshold THs is even smaller. For example, the measurement range upper limit RU is 4095, and the short circuit fault determination threshold THs is 3800.

[0052] The comparative electrostatic input device cannot detect a capacitance greater than the upper limit RU of the measurement range. When the capacitance (count value) of the sensor electrode 111 detected by the capacitance detection unit 122 of the comparative electrostatic input device exceeds the upper limit RU of the measurement range, the capacitance (count value) output by the capacitance detection unit 122 becomes the value of the upper limit RU of the measurement range.

[0053] The capacitance Cp on the horizontal axis is the actual capacitance of the sensor electrode 111 when no touch operation is being performed with the fingertip FT, and represents the parasitic capacitance of the sensor electrode 111. The capacitance Cf on the horizontal axis represents the actual capacitance between the fingertip FT and the sensor electrode 111. The actual capacitance of the sensor electrode 111 when a touch operation is being performed with the fingertip FT is Cp+Cf.

[0054] In this case, as shown on the vertical axis of FIG. 3A , the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp is C1, and the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp+Cf is C2. The capacitance C1 is the capacitance detected by the capacitance detection unit 122 by integrating the capacitance Cp a predetermined number of times. The capacitance C2 is the capacitance detected by the capacitance detection unit 122 by integrating the capacitance Cp+Cf a predetermined number of times. In this case, the capacitance of the fingertip FT is the difference ΔAD between C1 and C2.

[0055] Here, the short-circuit failure determination threshold THs is set to a value greater than the capacitance C2 detected by the capacitance detection unit 122 when a touch operation is being performed with the fingertip FT, and is set to a value such that the capacitance C2 does not exceed the short-circuit failure determination threshold THs as long as a touch operation is being performed with the fingertip FT. Therefore, it is not determined that a short-circuit failure has occurred, and the determination unit 123 can perform operation determination based on the difference value ΔAD.

[0056] Next, using FIG. 3B , the capacitance detected by the capacitance detection unit 122 when a palm or part of an arm larger than the fingertip FT touches the operation surface 110B1 when there is no short-circuit failure in any of the sensor electrodes 111 to 116 of the comparative electrostatic input device will be described. Here, as an example, a case where a palm or part of an arm touches the region (1) where the sensor electrode 111 is located will be described. When a part of the human body larger than the fingertip FT, such as a palm or part of an arm, touches the operation surface 110B1, the capacitance of the sensor electrode 111 becomes larger than the capacitance when a touch operation is performed with the fingertip FT. The same applies to the sensor electrodes 112 to 116. Here, as an example, a case where a palm touches the operation surface 110B1 will be described.

[0057] The horizontal and vertical axes of Fig. 3B are the same as those of Fig. 3A, and the vertical axis represents the short-circuit failure determination threshold THs and the upper limit RU of the measurement range.

[0058] 3A, the capacitance Cp on the horizontal axis represents the parasitic capacitance of the sensor electrode 111. The capacitance Ch on the horizontal axis represents the actual capacitance between the palm and the sensor electrode 111. When the palm is in contact with area (1) of the operation surface 110B1, the actual capacitance of the sensor electrode 111 is Cp+Ch.

[0059] In this case, as shown on the vertical axis of Fig. 3B, the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp is C1, and the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp+Ch is C3. The capacitance C3 is larger than the capacitance C2 shown in Fig. 3A, larger than the short-circuit failure determination threshold THs, and larger than the measurement range upper limit RU. The capacitance C3 is the capacitance detected by the capacitance detection unit 122 by integrating the capacitance Cp+Ch a predetermined number of times.

[0060] Because capacitance C3 exceeds short-circuit failure determination threshold THs, when the palm of the hand touches area (1) of operation surface 110B1, determination unit 123 erroneously determines that a short-circuit failure has occurred in sensor electrode 111, and, as an example, control device 120 transitions from normal mode to safe mode. When control device 120 transitions to safe mode, the comparative electrostatic input device is placed in a state in which it is unable to perform operation determination. This also applies when the palm of the hand touches any of areas (2) to (6) of operation surface 110B1 corresponding to sensor electrodes 112 to 116.

[0061] Furthermore, if a short circuit actually occurs in sensor electrode 111, a larger current continues to flow through sensor electrode 111 than when the palm of the hand is touching operation surface 110B1, and the capacitance detected by capacitance detection unit 122 becomes larger than capacitance C3 and exceeds short circuit determination threshold THs. As a result, determination unit 123 determines that a short circuit has occurred in sensor electrode 111. Note that this also applies when a short circuit occurs in any of sensor electrodes 112 to 116.

[0062] For this reason, with the comparative electrostatic input device, it was not possible to distinguish whether a short circuit had actually occurred in any of the sensor electrodes 111 to 116, or whether a palm or part of the arm was touching any of the sensor electrodes 111 to 116, resulting in a false determination that a short circuit had occurred.

[0063] Furthermore, in the comparative electrostatic input device, such erroneous determinations could also occur when EMC (Electromagnetic Compatibility) noise is generated and detected by any of the sensor electrodes 111 to 116.

[0064] <Operation Determination and Failure Determination in Electrostatic Input Device 100 of the Embodiment> Here, operation determination and failure determination in the electrostatic input device 100 of the embodiment will be described with reference to FIGS. 4A and 4B. FIG.

[0065] 4A , the electrostatic capacitance detected by the electrostatic capacitance detection unit 122 when the determination unit 123 performs an operation determination in a state where no short-circuit fault occurs in any of the sensor electrodes 111 to 116 of the electrostatic input device 100 of the embodiment will be described. Also, as an example, the case where a touch operation is performed on the area (1) where the sensor electrode 111 is located will be described.

[0066] For example, the electrostatic input device 100 selects the sensor electrodes 111 to 116 one by one, performs a fault determination, and if no short-circuit fault has occurred, performs an operation determination for the selected sensor electrode. Therefore, when the electrostatic input device 100 selects one of the sensor electrodes 111 to 116 and performs an operation determination, it means that no short-circuit fault has occurred in the selected sensor electrode (one of 111 to 116).

[0067] The sensitivity setting unit 124 of the electrostatic input device 100 sets the output sensitivity of the measurement circuit 120A to a second output sensitivity when the determination unit 123 is performing an operation determination. The second output sensitivity is, for example, equal to the output sensitivity of the measurement circuit 120A of a comparative electrostatic input device and is greater than the first output sensitivity, which is the output sensitivity of the measurement circuit 120A when the determination unit 123 is performing a fault determination. By setting the output sensitivity of the measurement circuit 120A to the second output sensitivity, the gain of the amplifier of the measurement circuit 120A is set to a second gain (second amplification factor). The second gain is greater than the first gain (first amplification factor) set in the amplifier of the measurement circuit 120A when the determination unit 123 is performing a fault determination. The first gain is the gain set in the amplifier of the measurement circuit 120A when the output sensitivity of the measurement circuit 120A is the first output sensitivity. Setting the output sensitivity of the measurement circuit 120A to the first output sensitivity or the second output sensitivity is performed by the sensitivity setting unit 124.

[0068] The horizontal axis in Fig. 4A is the same as the horizontal axis in Fig. 3A and Fig. 3B. The vertical axis in Fig. 4A, like the vertical axis in Fig. 3A and Fig. 3B, indicates the capacitance (count value) detected by the capacitance detection unit 122. However, when the determination unit 123 performs an operation determination, the capacitance detection unit 122 of the electrostatic input device 100 integrates the output of the measurement circuit 120A over a second number of integrations when detecting the capacitance of the sensor electrodes 111 to 116. As an example, the second number of integrations is equal to the number of integrations in the measurement circuit 120A of the comparative electrostatic input device and is greater than the first number of integrations, which is the number of integrations when the determination unit 123 performs a fault determination. As an example, the second number of integrations is 128, and the first number of integrations is 4.

[0069] The vertical axis indicates the measurement range upper limit RU of the electrostatic input device 100, but does not indicate the short circuit failure determination threshold THs. The measurement range upper limit RU is, for example, the same as the measurement range upper limit RU shown in Figures 3A and 3B, and is determined by the specifications of the IC chip used as the control device 120. For example, the measurement range upper limit RU is 4095. The short circuit failure determination threshold THs will be described using Figure 4B.

[0070] The electrostatic input device 100 cannot detect a capacitance greater than the upper limit RU of the measurement range. When the capacitance (count value) of the sensor electrode 111 detected by the capacitance detection unit 122 of the electrostatic input device 100 exceeds the upper limit RU of the measurement range, the capacitance (count value) output by the capacitance detection unit 122 becomes the value of the upper limit RU of the measurement range. In this respect, it is similar to the comparative electrostatic input device.

[0071] The capacitance Cp on the horizontal axis is the actual capacitance of the sensor electrode 111 when no touch operation is being performed with the fingertip FT, and represents the parasitic capacitance of the sensor electrode 111. The capacitance Cf on the horizontal axis represents the actual capacitance between the fingertip FT and the sensor electrode 111. The actual capacitance of the sensor electrode 111 when a touch operation is being performed with the fingertip FT is Cp+Cf. This is the same as in FIG. 3A .

[0072] In this case, as shown on the vertical axis of Fig. 4A, the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp is C1, and the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp + Cf is C2. The capacitance C1 is the capacitance detected by the capacitance detection unit 122 by integrating the capacitance Cp over the second number of integrations. The capacitance C2 is the capacitance detected by the capacitance detection unit 122 by integrating the capacitance Cp + Cf over the second number of integrations.

[0073] The output sensitivity of the measurement circuit 120A is set so that the capacitance C2 does not exceed the upper limit RU of the measurement range as long as a touch operation is being performed with the fingertip FT. Therefore, the capacitance detection unit 122 of the electrostatic input device 100 can detect a capacitance C2 that is equal to or less than the upper limit RU of the measurement range in the operation determination, and can output a difference value ΔAD between the capacitances C1 and C2 to the determination unit 123. As a result, the determination unit 123 can perform the operation determination by comparing the difference value ΔAD with a touch operation threshold for determining the touch operation.

[0074] Next, using Fig. 4B , a description will be given of the capacitance detected by the capacitance detection unit 122 when a part of the palm or arm larger than the fingertip FT touches the operation surface 110B1 in a state where the determination unit 123 of the electrostatic input device 100 has performed a fault determination and no short-circuit fault has occurred in any of the sensor electrodes 111 to 116. Here, as an example, a case will be described where the palm touches region (1) of the operation surface 110B1 of the sensor electrode 111, as in Fig. 3B .

[0075] The horizontal axis of Fig. 4B is the same as the horizontal axis of Fig. 4A and represents the actual capacitance of the sensor electrode 111. The vertical axis of Fig. 4B represents the capacitance (count value) detected by the capacitance detection unit 122 of the electrostatic input device 100, similar to the vertical axis of Fig. 4A, but the scale is different.

[0076] When the electrostatic input device 100 performs a fault determination, in order to distinguish between an increase in capacitance caused by a palm touching the operation surface 110B1 and an increase in capacitance caused by a large current flowing through the sensor electrode 111 due to a short-circuit fault and to suppress erroneous determination, the sensitivity setting unit 124 sets the output sensitivity of the measurement circuit 120A to a first output sensitivity that is smaller than the second output sensitivity when the determination unit 123 performs a fault determination. As a result, in the electrostatic input device 100, when the determination unit 123 performs a fault determination, the gain of the amplifier of the measurement circuit 120A is set to the first gain that is smaller than the second gain.

[0077] The capacitance when a large current flows through the sensor electrode 111 due to a short circuit is much larger than the capacitance when the palm is touching the operation surface 110B1. Therefore, if the output sensitivity of the measurement circuit 120A is significantly reduced during fault detection, the two can be distinguished within the upper measurement range limit RU. Specifically, the fault detection threshold THs can be set to a value greater than the capacitance increase caused by the palm touching the operation surface 110B1 but smaller than the capacitance increase caused by the short circuit. As an example, in FIG. 4B , the fault detection threshold THs is 100 (count value), which is much smaller than the fault detection threshold THs (3800) shown in FIGS. 3A and 3B .

[0078] That is, when the determination unit 123 performs a fault determination, the sensitivity setting unit 124 sets the output sensitivity of the measurement circuit 120A to the very low first output sensitivity and sets the fault determination threshold value THs to the value described above, thereby making it possible to distinguish, within a range equal to or less than the upper measurement range limit RU, between an increase in capacitance caused by a palm touching the operation surface 110B1 and an increase in capacitance caused by a large current flowing through the sensor electrode 111 due to a short-circuit fault. In this way, it is possible to suppress erroneous determinations in the fault determination and improve the determination accuracy of the fault determination.

[0079] 4B, the capacitance Cp on the horizontal axis represents the parasitic capacitance of the sensor electrode 111. The capacitance Ch on the horizontal axis represents the actual capacitance between the palm and the sensor electrode 111. When the palm is in contact with area (1) of the operation surface 110B1, the actual capacitance of the sensor electrode 111 is Cp+Ch.

[0080] In this case, as shown on the vertical axis of Fig. 4B, the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp is C11, and the capacitance detected by the capacitance detection unit 122 based on the capacitance Cp+Ch is C13. The capacitances C11 and C13 are smaller than the capacitances C1 and C3 shown in Fig. 3B because the output sensitivity of the measurement circuit 120A is set to the first output sensitivity (low value).

[0081] The capacitance C13 has a small value because the output sensitivity of the measurement circuit 120A is set to the first output sensitivity (low value), and is below the fault determination threshold THs (100) and below the measurement range upper limit RU (4095).

[0082] In this way, the first output sensitivity is a gain that makes the capacitance of the sensor electrode 111 detected by the capacitance detection unit 122 less than the fault determination threshold THs (100) even when the coupling between the sensor electrode 111 and the palm is maximized by the object touching the operation surface 110B1 when the determination unit 123 performs a fault determination.

[0083] Furthermore, when a short circuit occurs in the sensor electrode 111, the capacitance detected by the capacitance detection unit 122 only needs to exceed the failure determination threshold THs (100), and may be a value equal to or less than the measurement range upper limit RU (4095) or a value exceeding the measurement range upper limit RU (4095). This is because the output of the capacitance detection unit 122 when the measurement range upper limit RU (4095) is exceeded becomes the measurement range upper limit RU (4095).

[0084] As described above, in the electrostatic input device 100, when the determination unit 123 performs a fault determination, the sensitivity setting unit 124 sets the output sensitivity of the measurement circuit 120A to the first output sensitivity which is lower than the second output sensitivity, thereby making it possible to distinguish between an increase in capacitance of the sensor electrode 111 caused by the palm of the hand touching the operation surface 110B1 and an increase in capacitance caused by a short circuit fault of the sensor electrode 111. This also applies to the sensor electrodes 112 to 116.

[0085] Furthermore, as with the increase in capacitance of sensor electrode 111 due to EMC noise caused by touching operation surface 110B1 with the palm of the hand, by setting the first output sensitivity so that the capacitance is equal to or less than fault determination threshold value THs (100) and equal to or less than upper limit RU (4095) of the measurement range, it is possible to distinguish this from a short-circuit fault of sensor electrode 111. This also applies to sensor electrodes 112 to 116.

[0086] In this way, the electrostatic input device 100 can suppress erroneous determinations in the failure determination and improve the determination accuracy of the failure determination.

[0087] <Operation in Scan Cycle T> Fig. 5A is a diagram showing an example of the operation of the electrostatic input device 100 in the scan cycle T. In Fig. 5A, the horizontal axis represents time t. Fig. 5A shows the scan cycle T during which the determination unit 123 of the electrostatic input device 100 performs fault determination and operation determination for the sensor electrodes 111 to 116. The scan cycle T is, for example, 10 ms (milliseconds). In Fig. 5A, the sensor electrodes 111 to 116 are shown as electrodes 1 to 6.

[0088] 5B will be used in addition to FIG. 5A. FIG. 5B is a diagram showing an example of details of the operation determination for the sensor electrode 111.

[0089] 5A, when one scan period T starts, the determination unit 123 first performs a short-circuit fault determination of the common capacitor (common cap) connected to the sensor electrodes 111 to 116, and then sequentially performs a fault determination and an operation determination of the sensor electrodes 111 to 116. Here, a description will be given of a processing procedure when no short-circuit fault has occurred in the short-circuit fault determination of the common capacitor (common cap) and the fault determination of the sensor electrodes 111 to 116.

[0090] If no short circuit fault occurs in the short circuit fault determination of the common capacitor (common cap) and the fault determination of the sensor electrodes 111 to 116, as shown in Figure 5A, the total time required for the short circuit fault determination of the common capacitor (common cap) and the fault determination and operation determination of the sensor electrodes 111 to 116 is shorter than the scan period T.

[0091] After completing the short-circuit fault determination of the common capacitor (common Cap), the determination unit 123 selects the sensor electrode 111, performs a fault determination on the sensor electrode 111, and then performs an operation determination on the sensor electrode 111. After completing the fault determination and operation determination on the sensor electrode 111, the determination unit 123 selects the sensor electrode 112, performs a fault determination on the sensor electrode 112, and then performs an operation determination on the sensor electrode 112. Thereafter, the determination unit 123 selects the sensor electrodes 113 to 116 in order, and performs fault determination and operation determination on the sensor electrode 112.

[0092] Here, the time required for determining a malfunction of each of the sensor electrodes 111 to 116 is shorter than the time required for determining an operation.

[0093] In the electrostatic input device 100, when a failure is detected, the output sensitivity of the measurement circuit 120A is reduced to the first output sensitivity. When the output sensitivity of the measurement circuit 120A is low, the resistance to noise increases, and therefore the number of integrations performed by the capacitance detection unit 122 to detect the capacitance can be reduced.

[0094] Furthermore, in the electrostatic input device 100, in order to increase the resistance to noise when determining an operation, AC power of multiple frequencies is sequentially applied to each of the sensor electrodes 111 to 116 to detect the capacitance, but since the resistance to noise increases when determining a failure, the number of frequencies (number of types) of AC power applied to each of the sensor electrodes 111 to 116 can be reduced.

[0095] The time required for fault determination can be shortened by reducing the number of integrations performed during fault determination. Also, the time required for fault determination can be shortened by reducing the number of frequencies (number of types) of AC power applied to each of the sensor electrodes 111 to 116.

[0096] The scan period T is a period set when no fault determination is performed on each of the sensor electrodes 111 to 116, but because the time required for fault determination is short, fault determination on each of the sensor electrodes 111 to 116 can be performed without extending the scan period T. As shown in FIG. 5A , the end point of the operation determination for the sensor electrode 116 is earlier than the end point of the scan period T, and there is still some time left in the scan period T.

[0097] As shown in Fig. 5B , in one example of determining whether the sensor electrode 111 is being operated, AC power of three different frequencies, 1 to 3, is sequentially applied to the sensor electrode 111. Fig. 5B shows separate periods during which AC power of each frequency, 1 to 3, is applied and operation determination is performed. In addition, the number of times (second integration number) that the capacitance detection unit 122 integrates to determine operation while applying AC power of each frequency is, for example, 128 times.

[0098] In contrast, the number of frequencies (number of types) of AC power applied to each of the sensor electrodes 111 to 116 when the electrostatic input device 100 performs a fault determination is, for example, 1. Also, when the electrostatic input device 100 performs a fault determination, the number of times (first integration times) that the capacitance detection unit 122 performs integration is, for example, 4 times.

[0099] In this way, by reducing the number of integrations (second integrations) of the capacitance detection unit 122 when determining a fault and by reducing the number of frequencies (number of types) of AC power applied to each of the sensor electrodes 111 to 116, the time required for fault determination can be made shorter than the time required for operation determination.

[0100] The number of frequencies (number of types) of AC power applied to each of the sensor electrodes 111 to 116 when the electrostatic input device 100 performs operation determination may be 2 or more. The number of frequencies (number of types) of AC power applied to each of the sensor electrodes 111 to 116 when the electrostatic input device 100 performs failure determination may be 2 or more as long as it is less than the number of frequencies of AC power applied when performing operation determination.

[0101] Although the processing procedure when no short circuit fault occurs has been described above, if a short circuit fault of the common capacitor (common cap) is found in the short circuit fault determination of the common capacitor (common cap), the electrostatic input device 100 transitions to the safe mode at that time. Also, if a short circuit fault is found in the fault determination of any of the sensor electrodes 111 to 116, the electrostatic input device 100 transitions to the safe mode at that time.

[0102] <Flowchart> FIG. 6 is a flowchart showing an example of processing executed by the information processing unit 120B of the electrostatic input device 100.

[0103] The main control unit 121 sets parameters for failure determination of the sensor electrodes 111 to 116 (step S1). The parameters for failure determination include a first output sensitivity, a first number of integrations, and the number (number of types) of frequencies of AC power applied to the sensor electrodes when detecting capacitance, as well as the frequency values.

[0104] The main control unit 121 sets parameters for determining operation of the sensor electrodes 111 to 116 (step S2). The parameters for determining operation include a second output sensitivity, a second number of integrations, and the number (number of types) of frequencies of AC power to be applied to the sensor electrodes when detecting capacitance, as well as the frequency values.

[0105] The determination unit 123 selects one of the sensor electrodes 111 to 116 and performs a failure determination (step S3). With the main control unit 121 setting the frequency of the AC power applied to the sensor electrodes to the number of types for failure determination (one type as an example), setting the output sensitivity of the measurement circuit 120A to the first output sensitivity, and setting the number of integration times of the capacitance detection unit 122 to the first number of integration times, the determination unit 123 selects one of the sensor electrodes 111 to 116 and compares the capacitance detected by the capacitance detection unit 122 with the failure determination threshold value THs to perform a failure determination. By repeatedly performing the process of step S3, the determination unit 123 sequentially selects the sensor electrodes 111 to 116 one by one.

[0106] The determination unit 123 determines whether the capacitance detected by the capacitance detection unit 122 for the selected sensor electrode exceeds the failure determination threshold value THs (step S4).

[0107] If the determination unit 123 determines in step S4 that the capacitance exceeds the failure determination threshold value THs (S4: YES), it increments the count value FailCount of the failure counter (step S5). The determination unit 123 has a failure counter that counts the count value FailCount. Incrementing the count value FailCount of the failure counter means calculating FailCount = FailCount + 1.

[0108] The determination unit 123 determines whether the count value FailCount of the failure counter exceeds the determination count threshold value FailJudge for determining a failure (step S6). The determination unit 123 determines whether FailJudge < FailCount holds.

[0109] If the determination unit 123 determines in step S6 that the count value FailCount of the failure counter exceeds the determination number threshold FailJudge (S6: YES), it determines that a short-circuit failure has occurred in the sensor electrode selected in step S3 (step S7). As a result, the determination unit 123 notifies the ECU 50 that a short-circuit failure has occurred in the sensor electrode selected in step S3. This causes the electrostatic input device 100 to transition to the safe mode. Furthermore, upon completing the process of step S7 and transitioning to the safe mode, the electrostatic input device 100 stops operating (end). The state of the electrostatic input device 100 in the safe mode can be set to various states, such as a state in which the operation of the electrostatic input device 100 is temporarily stopped (for a predetermined time) or a state in which operation is stopped until a recovery command is received from a higher-level device such as the ECU 50.

[0110] Note that if the judgment count threshold FailJudge in step S6 is 10, for example, a NO judgment is made in step S6, the flow returns to step S3, and the process of proceeding to step S6 again is repeated 10 times, resulting in a YES judgment in step S6. As an example, if the count value FailCount of the failure counter exceeds the judgment count threshold FailJudge within 20 consecutive scan periods T shown in FIG. 5A, a YES judgment may be made in step S6. In this case, if the count value FailCount does not exceed the judgment count threshold FailJudge within 20 consecutive scan periods T shown in FIG. 5A, the count value FailCount may be reset. This is to determine whether a short-circuit fault has actually occurred within a certain period of time, such as 20 consecutive scan periods T.

[0111] Furthermore, if the determination unit 123 determines in step S4 that the capacitance does not exceed the failure determination threshold THs (S4: NO), it resets the count value FailCount of the failure counter (step S8). That is, FailCount = 0. After completing the process of step S8, the determination unit 123 advances the flow to step S9.

[0112] Furthermore, if the determining unit 123 determines in step S6 that the count value of the failure counter does not exceed the determination number threshold (S6: NO), the flow proceeds to step S9.

[0113] In the process of Fig. 6, the period during which the processes of steps S1 to S4 or steps S1 to S6 are performed corresponds to the period during which the failure determination of the selected sensor electrode is performed in Fig. 5A. Furthermore, the processes of steps S8 to S14 correspond to the period during which the operation determination of the selected sensor electrode is performed in Fig. 5A.

[0114] The determination unit 123 performs an operation determination for the currently selected sensor electrode selected in step S3 (step S9). The currently selected sensor electrode is the sensor electrode selected in step S3. The main control unit 121 sets the frequency of the AC power applied to the sensor electrode to the number of types for operation determination (for example, three types), sets the output sensitivity of the measurement circuit 120A to the second output sensitivity, and sets the number of integrations of the capacitance detection unit 122 to the second number of integrations. In this state, the determination unit 123 performs an operation determination by comparing the capacitance difference value ΔAD output from the capacitance detection unit 122 for the sensor electrode selected in step S3 with an operation determination threshold. Note that by repeatedly performing the process from step S3 to step S9, the determination unit 123 sequentially selects the sensor electrodes 111 to 116 one by one and performs an operation determination.

[0115] The determination unit 123 determines whether the capacitance difference value ΔAD output from the capacitance detection unit 122 for the selected sensor electrode exceeds the operation determination threshold (step S10).

[0116] When the determination unit 123 determines in step S10 that the capacitance difference value ΔAD exceeds the operation determination threshold (S10: YES), it increments the count value TouchCount of the touch counter (step S11). The determination unit 123 has a touch counter that counts the count value TouchCount. Incrementing the count value TouchCount of the touch counter is equivalent to calculating TouchCount = TouchCount + 1.

[0117] The determination unit 123 determines whether the count value TouchCount of the touch counter exceeds a determination count threshold value TouchJudge for determining that a touch operation has occurred (step S12). The determination unit 123 determines whether TouchJudge < TouchCount holds.

[0118] When the determination unit 123 determines in step S12 that the count value TouchCount of the touch counter exceeds the determination count threshold value TouchJudge (S12: YES), it determines that a touch operation has been performed on the sensor electrode selected in step S3 (step S13). As a result, the determination unit 123 notifies the ECU 50 that a touch operation has been performed on the sensor electrode selected in step S3.

[0119] When the determination unit 123 determines in step S10 that the capacitance difference value ΔAD does not exceed the operation determination threshold value (S10: NO), it resets the count value TouchCount of the touch counter (step S14). That is, TouchCount = 0. After finishing the process of step S14, the determination unit 123 returns the flow to step S3. As a result, in step S3, the next one of the sensor electrodes 111 to 116 is selected, and a series of processes is continuously performed.

[0120] Also, when the determination unit 123 determines in step S12 that the count value TouchCount of the touch counter does not exceed the determination count threshold value TouchJudge (S12: NO), or when the process of step S13 is finished, it returns the flow to step S3. As a result, in step S3, the next one of the sensor electrodes 111 to 116 is selected, and a series of processes is continuously performed. When the determination count threshold value TouchJudge in step S12 is 3 as an example, the process of returning the flow to step S3 after being determined as NO in step S12 and then proceeding to step S12 again is repeated 3 times, and thus it is determined as YES in step S12.

[0121] <Effects> The electrostatic input device 100 includes a sensor electrode (any one of 111 to 116) provided on the back side of the operation surface 110B1, a measurement circuit 120A connected to the sensor electrode (any one of 111 to 116), a determination unit 123 that performs a failure determination to determine a failure of the sensor electrode (any one of 111 to 116) based on the electrostatic capacitance of the sensor electrode (any one of 111 to 116) obtained from the output of the measurement circuit 120A, and also performs an operation determination to determine whether an object has contacted or approached the operation surface 110B1, and a sensitivity setting unit 124 that sets a first output sensitivity of the measurement circuit 120A when the determination unit 123 is performing the failure determination to be lower than a second output sensitivity of the measurement circuit 120A when the determination unit 123 is performing the operation determination. In this way, by reducing the output sensitivity of the measurement circuit 120A when a fault is determined, it is possible to distinguish between an increase in capacitance of the sensor electrode 111 caused by a large part of the human body, such as a palm, touching the operation surface 110B1 and an increase in capacitance caused by a short-circuit fault in the sensor electrode 111.

[0122] Therefore, by reducing the output sensitivity of the capacitance when determining whether the sensor electrode has a malfunction, it is possible to provide the electrostatic input device 100 that can improve the accuracy of the malfunction determination.

[0123] The device further includes a capacitance detection unit 122 that detects the capacitance of the sensor electrode (any one of 111 to 116) based on the output of the measurement circuit 120A, and a failure of the sensor electrode (any one of 111 to 116) is a short-circuit failure of the sensor electrode (any one of 111 to 116), and the determination unit 123 performs failure determination by comparing the capacitance of the sensor electrode (any one of 111 to 116) detected by the capacitance detection unit 122 with a failure determination threshold, and the first output sensitivity may be an amplification factor that makes the capacitance of the sensor electrode (any one of 111 to 116) detected by the capacitance detection unit 122 less than the failure determination threshold when the determination unit 123 performs failure determination, even when the coupling between the sensor electrode (any one of 111 to 116) and the object is maximized by the object contacting or approaching the operation surface 110B1. It is possible to provide an electrostatic input device 100 that can more reliably distinguish between a large part of the human body, such as a palm, touching the operation surface 110B1 and an increase in capacitance due to a short circuit failure of the sensor electrode 111, thereby further improving the accuracy of failure determination.

[0124] The electrostatic input device 100 further includes a capacitance detection unit 122 that detects the capacitance of one of the sensor electrodes (111 to 116) by integrating the output of the measurement circuit 120A. The determination unit 123 performs fault determination and operation determination using the capacitance of one of the sensor electrodes (111 to 116) detected by the capacitance detection unit 122. The first number of integrations for detecting the capacitance of one of the sensor electrodes (111 to 116) when the determination unit 123 performs fault determination may be less than the second number of integrations for detecting the capacitance of one of the sensor electrodes (111 to 116) when the determination unit 123 performs operation determination. Reducing the output sensitivity of the measurement circuit 120A during fault determination increases resistance to noise, thereby reducing the number of integrations performed by the capacitance detection unit 122 to detect the capacitance. Reducing the number of integrations enables fault determination to be performed in a shorter time, thereby enabling fault determination to be achieved without extending the scan period T of the electrostatic input device 100.

[0125] Alternatively, when the determination unit 123 performs a manipulation determination, AC power of N (N is an integer equal to or greater than 2) different frequencies may be applied to the sensor electrodes (111 to 116), and when the determination unit 123 performs a fault determination, AC power of M (M is a natural number less than N) different frequencies may be applied to the sensor electrodes (111 to 116). To reduce the influence of noise during manipulation determination, the capacitance detection unit 122 applies multiple frequencies of AC power to the sensor electrodes (111 to 116) when detecting capacitance. This is because if the noise frequency is equal to the AC power frequency, the detected capacitance will be affected by the noise. In contrast, when a fault determination is performed, reducing the output sensitivity of the measurement circuit 120A increases noise resistance, and therefore the capacitance detection unit 122 is less susceptible to noise even if it applies fewer frequencies to the sensor electrodes (111 to 116) when detecting capacitance than when performing manipulation determination. Furthermore, by reducing the frequency of the AC power, it becomes possible to perform failure determination in a short time, and failure determination can be realized without extending the scan period T of the electrostatic input device 100 .

[0126] Furthermore, the determination unit 123 may perform a fault determination for the sensor electrodes (any one of 111 to 116), and perform an operation determination if it is determined that no fault has occurred in the sensor electrodes (any one of 111 to 116). By performing a fault determination before the operation determination, the operation determination can be performed in a state in which no fault has occurred in the sensor electrodes, thereby improving the accuracy of the operation determination.

[0127] Alternatively, the electrostatic input device 100 may include a plurality of sensor electrodes 111 to 116, and the determination unit 123 may select the sensor electrodes 111 to 116 one by one from the plurality of sensor electrodes 111 to 116 and perform a fault determination and an operation determination in that order. In this way, it is possible to reliably determine whether a fault has occurred in each sensor electrode, thereby improving the reliability of use of the electrostatic input device 100.

[0128] The electrostatic detection device includes a sensor electrode (one of 111 to 116), a measurement circuit 120A connected to the sensor electrode (one of 111 to 116), a determination unit 123 that performs a fault determination to determine a fault in the sensor electrode (one of 111 to 116) based on the capacitance of the sensor electrode (one of 111 to 116) obtained from the output of the measurement circuit 120A, and a proximity determination to determine the proximity of an object to the sensor electrode (one of 111 to 116), and a sensitivity setting unit 124 that sets a first output sensitivity of the measurement circuit 120A when the determination unit 123 is performing the fault determination lower than a second output sensitivity of the measurement circuit 120A when the determination unit 123 is performing the proximity determination. In this way, by reducing the output sensitivity of the measurement circuit 120A during fault determination, it is possible to distinguish between an increase in capacitance of the sensor electrode 111 caused by a large part of the human body, such as a palm, touching the operation surface 110B1 and an increase in capacitance caused by a short-circuit fault in the sensor electrode 111.

[0129] Therefore, by reducing the output sensitivity of the capacitance when determining whether a sensor electrode has a malfunction, it is possible to provide an electrostatic detection device that can improve the accuracy of determining whether a sensor electrode has a malfunction.

[0130] The device further includes a capacitance detection unit 122 that detects the capacitance of the sensor electrode (any one of 111 to 116) based on the output of the measurement circuit 120A, and a failure of the sensor electrode (any one of 111 to 116) is a short-circuit failure of the sensor electrode (any one of 111 to 116), and the determination unit 123 performs failure determination by comparing the capacitance of the sensor electrode (any one of 111 to 116) detected by the capacitance detection unit 122 with a failure determination threshold, and the first output sensitivity may be an amplification factor that makes the capacitance of the sensor electrode (any one of 111 to 116) detected by the capacitance detection unit 122 less than the failure determination threshold when the determination unit 123 performs failure determination, even if the coupling between the sensor electrode (any one of 111 to 116) and the object is maximized due to the object approaching the sensor electrode (any one of 111 to 116). It is possible to provide an electrostatic detection device that can more reliably distinguish between a large part of the human body, such as a palm, touching the operation surface 110B1 and an increase in capacitance due to a short circuit failure of the sensor electrode 111, thereby further improving the accuracy of fault detection.

[0131] The device further includes a capacitance detection unit 122 that detects the capacitance of one of the sensor electrodes (111-116) by integrating the output of the measurement circuit 120A. The determination unit 123 performs fault and proximity determinations using the capacitance of one of the sensor electrodes (111-116) detected by the capacitance detection unit 122. The first number of integrations used by the determination unit 123 to detect the capacitance of one of the sensor electrodes (111-116) when performing fault determination may be less than the second number of integrations used by the determination unit 123 to detect the capacitance of one of the sensor electrodes (111-116) when performing proximity determination. Reducing the output sensitivity of the measurement circuit 120A during fault determination increases resistance to noise, allowing the number of integrations performed by the capacitance detection unit 122 to detect capacitance to be reduced. Reducing the number of integrations enables fault determination to be performed in a shorter time, thereby enabling fault determination to be achieved without extending the scan period T of the electrostatic detection device.

[0132] Alternatively, when the determination unit 123 performs proximity determination, AC power of N (N is an integer equal to or greater than 2) different frequencies may be applied to the sensor electrodes (111 to 116), and when the determination unit 123 performs fault determination, AC power of M (M is a natural number less than N) different frequencies may be applied to the sensor electrodes (111 to 116). In order to reduce the influence of noise during operation determination, AC power of multiple frequencies is applied to the sensor electrodes (111 to 116) when the capacitance detection unit 122 detects capacitance. This is because if the noise frequency is equal to the AC power frequency, the detected capacitance will be affected by the noise. In contrast, during fault determination, reducing the output sensitivity of the measurement circuit 120A increases noise resistance, and therefore the capacitance detection unit 122 is less susceptible to noise even if it applies fewer frequencies to the sensor electrodes (111 to 116) when detecting capacitance than during operation determination. Furthermore, by reducing the frequency of the AC power, it becomes possible to perform failure determination in a short time, and failure determination can be realized without extending the scan period T of the electrostatic detection device.

[0133] Furthermore, the determination unit 123 may perform a fault determination for the sensor electrodes (any one of 111 to 116), and perform an operation determination if it is determined that no fault has occurred in the sensor electrodes (any one of 111 to 116). By performing a fault determination before the operation determination, the operation determination can be performed in a state in which no fault has occurred in the sensor electrodes, thereby improving the accuracy of the operation determination.

[0134] Alternatively, the electrostatic input device 100 may include a plurality of sensor electrodes 111 to 116, and the determination unit 123 may select the sensor electrodes 111 to 116 one by one from the plurality of sensor electrodes 111 to 116 and perform a fault determination and a proximity determination in that order. In this manner, it is possible to reliably determine whether a fault has occurred in each sensor electrode, thereby improving the reliability of use of the electrostatic input device 100.

[0135] The above describes exemplary embodiments of the electrostatic input device and electrostatic detection device of the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

[0136] This international application claims priority based on Japanese Patent Application No. 2023-220862, filed on December 27, 2023, the entire contents of which are incorporated herein by reference.

[0137] REFERENCE SIGNS LIST 10 Steering wheel 100 Electrostatic input device 110 Operation unit 110B1 Operation surface 111 to 116 Sensor electrodes 120 Control device 120A Measuring circuit 120B Information processing unit 121 Main control unit 122 Capacitance detection unit 123 Determination unit 124 Sensitivity setting unit 125 Memory

Claims

1. A capacitive input device including: a sensor electrode provided on the back side of an operation surface; a measurement circuit connected to the sensor electrode; a determination unit that performs a failure determination for determining a failure of the sensor electrode based on the capacitance of the sensor electrode obtained from the output of the measurement circuit, and performs an operation determination for determining contact or proximity of an object to the operation surface; and a sensitivity setting unit that sets a first output sensitivity of the measurement circuit when the determination unit is performing the failure determination to be lower than a second output sensitivity of the measurement circuit when the determination unit is performing the operation determination.

2. The capacitive input device according to claim 1, further including a capacitance detection unit that detects the capacitance of the sensor electrode based on the output of the measurement circuit, wherein the failure of the sensor electrode is a short-circuit failure of the sensor electrode, and the determination unit performs the failure determination by comparing the capacitance of the sensor electrode detected by the capacitance detection unit with a failure determination threshold value, and the first output sensitivity is an amplification factor such that the capacitance of the sensor electrode detected by the capacitance detection unit is less than the failure determination threshold value even when the coupling between the sensor electrode and the object is maximized by contact or proximity of the object to the operation surface when the determination unit performs the failure determination.

3. The capacitive input device according to claim 1, further including a capacitance detection unit that detects the capacitance of the sensor electrode by integrating the output of the measurement circuit, wherein the determination unit performs the failure determination and the operation determination using the capacitance of the sensor electrode detected by the capacitance detection unit, and a first integration number for detecting the capacitance of the sensor electrode when the determination unit performs the failure determination is less than a second integration number for detecting the capacitance of the sensor electrode when the determination unit performs the operation determination.

4. The capacitive input device according to claim 3, wherein the determination unit applies AC power of N (N is an integer of 2 or more) types of frequencies to the sensor electrode when performing the operation determination, and applies AC power of M (M is a natural number less than N) types of frequencies to the sensor electrode when performing the failure determination.

5. The capacitive input device according to any one of claims 1 to 4, wherein the determination unit performs the failure determination for the sensor electrode, and performs the operation determination when it is determined that no failure has occurred in the sensor electrode.

6. The electrostatic input device according to any one of claims 1 to 4, comprising a plurality of said sensor electrodes, wherein the determination unit sequentially selects one of the sensor electrodes from the plurality of sensor electrodes, performs the failure determination, and performs the operation determination.

7. An electrostatic detection device, comprising: a sensor electrode; a measurement circuit connected to the sensor electrode; a determination unit that performs a failure determination for determining a failure of the sensor electrode based on the capacitance of the sensor electrode obtained from the output of the measurement circuit, and performs a proximity determination for determining proximity of an object to the sensor electrode; and a sensitivity setting unit that sets a first output sensitivity of the measurement circuit when the determination unit is performing the failure determination to be lower than a second output sensitivity of the measurement circuit when the determination unit is performing the proximity determination.

8. The electrostatic detection device according to claim 7, further comprising a capacitance detection unit that detects the capacitance of the sensor electrode based on the output of the measurement circuit, wherein the failure of the sensor electrode is a short-circuit failure of the sensor electrode, the determination unit performs the failure determination by comparing the capacitance of the sensor electrode detected by the capacitance detection unit with a failure determination threshold value, and the first output sensitivity is an amplification factor such that the capacitance of the sensor electrode detected by the capacitance detection unit is less than the failure determination threshold value even when the coupling between the sensor electrode and the object is maximized due to the proximity of the object to the sensor electrode when the determination unit performs the failure determination.

9. The electrostatic detection device according to claim 7, further comprising a capacitance detection unit that detects the capacitance of the sensor electrode by integrating the output of the measurement circuit, wherein the determination unit performs the failure determination and the proximity determination using the capacitance of the sensor electrode detected by the capacitance detection unit, and a first integration number for detecting the capacitance of the sensor electrode when the determination unit performs the failure determination is less than a second integration number for detecting the capacitance of the sensor electrode when the determination unit performs the proximity determination.

10. The electrostatic detection device according to claim 9, wherein N (N is an integer of 2 or more) types of AC power of frequencies are applied to the sensor electrode when the determination unit performs the proximity determination, and M (M is a natural number less than N) types of AC power of frequencies are applied to the sensor electrode when the determination unit performs the failure determination.

11. The determination unit performs the failure determination on the sensor electrode, and when it is determined that no failure has occurred in the sensor electrode, performs the proximity determination. The electrostatic detection device according to any one of claims 7 to 10.

12. Including a plurality of the sensor electrodes, the determination unit sequentially selects one sensor electrode from the plurality of sensor electrodes, performs the failure determination, and performs the proximity determination. The electrostatic detection device according to any one of claims 7 to 10.

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