Electrostatic input device

Abstract

Provided is an electrostatic input device capable of suppressing the situation that a reference value is updated to an erroneous value by erroneously determining that a proximity operation is not performed when a finger is held in contact with a sensor surface and stopped. The electrostatic sensor includes: a plurality of electrostatic sensor electrodes; a measurement circuit that outputs a measurement value based on the capacitance between each of the plurality of electrostatic sensor electrodes and the indicator; a control unit that determines, on the basis of a measurement value output by the measurement circuit, whether or not the indicator is in a proximity state in which the indicator approaches the plurality of electrostatic sensor electrodes; and a storage unit that stores, as a reference value, a measured value in a state in which the indicator does not approach the plurality of electrostatic sensor electrodes, and a control unit that determines whether or not the indicator is in an approaching state on the basis of a first difference value obtained by subtracting the reference value from the measured value, calculates a total difference value obtained by summing up the plurality of first difference values of the plurality of electrostatic sensor electrodes, and outputs the total difference value. In the approaching state, if a state in which the amount of variation of the total difference value is less than a predetermined value after the total difference value is reduced continues for a predetermined time or longer, the reference value is updated.

Description

Technical Field

[0001] The present disclosure relates to an electrostatic input device. Background Art

[0002] In the past, there was a touch detection device, characterized in that it includes: a sensor electrode that detects a detection capacitance corresponding to a touch operation; an operation determination unit that determines a touch operation based on a touch determination threshold and a non-touch determination threshold determined by the detection capacitance obtained based on a reference value as a measurement reference and the width of the detection capacitance relative to the reference value; and a threshold adjustment unit that adjusts the non-touch determination threshold if the difference between the detection capacitance and the reference value, i.e., the capacitance change value, takes a value within the range of the touch determination threshold and the non-touch determination threshold, and the vibration amplitude of the detection capacitance, i.e., the capacitance change amplitude, is less than the change amplitude threshold (for example, refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-116331 Summary of the Invention

[0006] -Problems to be solved by the invention-

[0007] In conventional touch detection devices, if a finger is brought into contact with the sensor surface by a touch operation and then stopped, the reference value is updated, and there is a possibility of erroneous determination that no touch operation has been performed.

[0008] Therefore, an object is to provide an electrostatic input device that can prevent a reference value from being updated to an erroneous value due to erroneous determination that no proximity operation has been performed when a finger is stopped while being kept in contact with a sensor surface.

[0009] -Methods for solving the problem-

[0010] The electrostatic input device of an embodiment of the present disclosure includes: a plurality of electrostatic sensor electrodes; a measuring circuit which outputs a measured value based on the electrostatic capacitance between each of the plurality of electrostatic sensor electrodes and an indicator; a control unit which determines whether the indicator is in a proximity state where the indicator is close to the plurality of electrostatic sensor electrodes based on the measured value output by the measuring circuit; and a storage unit which stores the measured value when the indicator is not close to the plurality of electrostatic sensor electrodes as a reference value, the control unit performing the following processing: determining whether the indicator is in the proximity state based on a first differential value obtained by subtracting the reference value from the measured value, calculating a total differential value which is the sum of the plurality of first differential values ​​of the plurality of electrostatic sensor electrodes, and updating the reference value in the proximity state if, after the total differential value decreases, the change in the total differential value is less than a given value for more than a given time.

[0011] -Effects of the Invention-

[0012] It is possible to provide an electrostatic input device that can prevent a reference value from being updated to an erroneous value due to an erroneous determination that no proximity operation has been performed when a finger is stopped while being kept in contact with a sensor surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a diagram showing an example of the structure of the electrostatic input device according to the embodiment.

[0014] Figure 2 This is a diagram showing an example of the structure of the electrostatic input device according to the embodiment.

[0015] Figure 3 This is a state transition diagram showing an example of the operation of the electrostatic input device according to the embodiment.

[0016] Figure 4A This is a flowchart showing an example of processing executed by the control unit of the electrostatic input device according to the embodiment.

[0017] Figure 4B This is a flowchart showing an example of processing executed by the control unit of the electrostatic input device according to the embodiment.

[0018] Figure 4C This is a flowchart showing an example of processing executed by the control unit of the electrostatic input device according to the embodiment.

[0019] Figure 4D This is a flowchart showing an example of processing executed by the control unit of the electrostatic input device according to the embodiment.

[0020] Figure 5 This is a diagram showing an example of the structure of an electrostatic input device according to a first modified example of the embodiment.

[0021] Figure 6 This is a diagram showing an example of the structure of an electrostatic input device according to a second modified example of the embodiment.

[0022] -Explanation of Symbols-

[0023] 100 Electrostatic input device

[0024] 101 housing

[0025] 105 Top Panel

[0026] 105A operating surface

[0027] 110 Display

[0028] 111 Slider

[0029] 111A Framework

[0030] 120 electrostatic sensor

[0031] 121 electrostatic sensor electrode

[0032] 125A measurement circuit

[0033] 125B image display circuit

[0034] 130 Control Device

[0035] 131 Control Department

[0036] 132 Memory

[0037] 140 Temperature sensor. DETAILED DESCRIPTION

[0038] Hereinafter, an embodiment of the electrostatic input device to which the present disclosure is applied will be described.

[0039] The following explanation defines an XYZ coordinate system. The direction parallel to the X-axis (X-direction), the direction parallel to the Y-axis (Y-direction), and the direction parallel to the Z-axis (Z-direction) are mutually orthogonal. Furthermore, "top view" refers to viewing the XY plane. Furthermore, the length, thickness, and other aspects of various components are sometimes exaggerated to facilitate understanding of the structure.

[0040] <Implementation Method>

[0041] Figure 1 as well as Figure 2 1 is a diagram showing an example of the configuration of the electrostatic input device 100 according to the embodiment.

[0042] The electrostatic input device 100 is installed, for example, in the center console of a vehicle and serves as an input unit for adjusting the volume of audio equipment, the temperature and air volume of an air conditioner, and the like. For example, the volume, temperature, or air volume can be adjusted by operating a slider 111, which functions as a GUI (Graphic User Interface) switch. Alternatively, the electrostatic input device 100 can be installed in stores, facilities, and the like, and can be a tablet-type input device used by a large number of users, or the input unit of an ATM (Automatic Teller Machine). Furthermore, the electrostatic input device 100 can be a tablet computer, smartphone, game console, or the like used by individuals.

[0043] <Overall Structure of Static Electricity Input Device 100>

[0044] The electrostatic input device 100 includes a housing 101 , a top panel 105 , a display 110 , an electrostatic sensor 120 , a measurement circuit 125A, an image display circuit 125B, a control device 130 , and a temperature sensor 140 .

[0045] exist Figure 1 In the embodiment, the electrostatic sensor 120 is provided on the back side (-Z direction side) of the top panel 105, and the display 110 is provided on the back side (-Z direction side) of the electrostatic sensor 120. Figure 1 Although the measurement circuit 125A, the image display circuit 125B, the control device 130 and the temperature sensor 140 are omitted (refer to Figure 2 ), but the measurement circuit 125A, the image display circuit 125B, the control device 130 and the temperature sensor 140 are provided inside the housing 101 on the back side (−Z direction side) of the display 110 as an example.

[0046] exist Figure 2 In FIG, the housing 101 and the top panel 105 are omitted, and the display 110 is shown larger than the electrostatic sensor 120. Figure 2 In FIG, the slider 111 displayed on the display 110 is omitted, and the electrostatic sensor electrode 121 of the electrostatic sensor 120 is shown transparently. Figure 2 , XYZ coordinates are shown for the display 110 and the electrostatic sensor 120 .

[0047] <Casing 101 and Top Panel 105>

[0048] The housing 101 is a case made of resin or metal, etc., and houses the display 110, the electrostatic sensor 120, the measurement circuit 125A, the image display circuit 125B, the control device 130, and the temperature sensor 140. As an example, the display 110 is disposed below the transparent electrostatic sensor 120 and can be viewed through an operation surface 105A, which is the upper surface of a transparent top panel 105 provided in an opening in the upper portion of the housing 101. The operation surface 105A is an example of a sensor surface.

[0049] The user operates the electrostatic input device by bringing a pointer, such as a hand, close to the electrostatic sensor 120. By adjusting the sensitivity of the electrostatic sensor 120 and the thickness of the top panel 105, operations can be performed while the pointer is in contact with the operating surface 105A. In other words, the pointer can be considered close to the operating surface 105A. Furthermore, by adjusting the sensitivity of the electrostatic sensor 120 and the thickness of the top panel 105, operations can be performed without the pointer touching the operating surface 105A. If the temperature of the electrostatic sensor electrode 121 of the electrostatic sensor 120 changes, the capacitance (measured value) measured by the measurement circuit 125A changes. If the product temperature is low, the temperature of the electrostatic sensor 120 rises when the user's hand (pointing object) touches the operating surface 105A. Furthermore, in confined spaces such as vehicle interiors, the temperature of the electrostatic sensor 120 may fluctuate dramatically due to heating. The electrostatic input device 100 of the present invention can mitigate the effects of such temperature fluctuations.

[0050] For example, if a user's hand or other pointing object continuously touches a cold operating surface 105A for a relatively long period (e.g., 2 to 10 seconds), as in a sliding operation, the temperature of the electrostatic sensor electrode of electrostatic sensor 120 rises. Temperature increases can also occur in situations other than sliding operations. The following describes how a user performs a sliding operation on slider 111. Furthermore, heating can also cause a temperature increase even when a user's hand or other pointing object is not in contact with operating surface 105A. Hereinafter, the term "proximity" refers to the following states: a state in which a user's hand or other pointing object is in contact with operating surface 105A, and a state in which the pointing object is separated from but very close to operating surface 105A. In either case, the pointing object is in proximity to electrostatic sensor 120.

[0051] Hereinafter, as an example, a method in which the user operates with the fingertips FT of the hand, but the electrostatic input device 100 can also be operated with parts of the user's body other than the fingertips FT of the hand.

[0052] <Display 110>

[0053] As an example, display 110 is a liquid crystal display, an organic EL (electroluminescence) display, or the like. Display 110 is a display unit for implementing a graphical user interface (GUI). Display 110 displays a GUI image including a slider 111 and a frame 111A. Frame 111A indicates the range within which slider 111 can be moved. Display 110 may also display GUI buttons, a cursor, and other components besides slider 111.

[0054] <Electrostatic Sensor 120, Measurement Circuit 125A, Image Display Circuit 125B>

[0055] The electrostatic sensor 120 is overlapped and configured on the display 110, such as Figure 2 As shown, the device includes a plurality of electrostatic sensor electrodes 121 arranged along the X direction. Each electrostatic sensor electrode 121 extends in the Y direction. Furthermore, a measurement circuit 125A is connected to the electrostatic sensor 120. Furthermore, an image display circuit 125B is connected to the display 110. The measurement circuit 125A is provided between the electrostatic sensor 120 and the control device 130. The image display circuit 125B is provided between the display 110 and the control device 130.

[0056] The electrostatic sensor electrode 121 is connected to the control device 130 via the measurement circuit 125A. Such an electrostatic sensor 120 can be formed by forming a transparent conductive film such as ITO (Indium Tin Oxide) on the surface of transparent glass and patterning the electrostatic sensor electrode 121. The electrostatic capacitance of the electrostatic sensor 120 is input to the measurement circuit 125A. Figure 1 as well as Figure 2 In FIG. 5 , five electrostatic sensor electrodes 121 are shown as an example. Figure 1 As shown, the five electrostatic sensor electrodes 121 are arranged at positions overlapping with the slider 111 and the frame 111A.

[0057] Measurement circuit 125A is mounted on a wiring board. It is located between electrostatic sensor 120 and control device 130 and performs analog-to-digital (A / D) conversion on the capacitance of each electrostatic sensor electrode 121. Measurement circuit 125A outputs the capacitance (measured value) of each electrostatic sensor electrode 121 to control device 130.

[0058] Measurement circuit 125A scans each of the multiple electrostatic sensor electrodes 121, converts the capacitance of each electrostatic sensor electrode 121 into a digital value, and calculates a differential value ΔAD for each electrostatic sensor electrode 121 by subtracting a reference value. The differential value ΔAD is a count of the change in the output of measurement circuit 125A relative to the reference value. The reference value is proportional to the capacitance of the electrostatic sensor electrode 121 when there is no object such as a fingertip FT near the electrostatic sensor electrode 121. Measurement circuit 125A calculates the differential value ΔAD by subtracting the reference value from the measured capacitance value of each electrostatic sensor electrode 121.

[0059] The image display circuit 125B is provided between the display 110 and the control device 130 , and causes the display 110 to display a GUI image of the slider 111 and the frame 111A according to image data transmitted from the control device 130 .

[0060] <Control Device 130>

[0061] The control device 130 includes a control unit 131 and a memory 132. The control device 130 is implemented as a computer that includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input / output interfaces, and an internal bus. The control unit 131 represents the functions of the program executed by the control device 130 as functional blocks. Furthermore, the memory 132 functionally represents the memory of the control device 130 and is an example of a storage unit.

[0062] <Control Unit 131>

[0063] The control unit 131 controls the operation of the electrostatic input device 100. The control unit 131 receives the differential value ΔAD from the measurement circuit 125A and calculates the X coordinate of the fingertip FT. The X coordinate of the fingertip FT calculated by the control unit 131 is the X coordinate of any one of the multiple electrostatic sensor electrodes 121. For example, the X coordinate of the electrostatic sensor electrode 121 is the X coordinate of the center of the electrostatic sensor electrode 121. The control unit 131 controls the display of images on the display 110 via the image display circuit 125B. The control unit 131 outputs the amount of operation of the slider 111 operated by the fingertip FT to the ECU (Electronic Control Unit) that controls the vehicle's audio, air conditioning, and other components.

[0064] <Memory 132>

[0065] Memory 132 stores a reference value used by measurement circuit 125A to calculate differential value ΔAD. As described above, the reference value is proportional to the capacitance of electrostatic sensor electrode 121 when no object, such as a fingertip FT, is present near electrostatic sensor electrode 121. Therefore, the reference value fluctuates depending on the temperature of electrostatic sensor electrode 121.

[0066] If the reference value is not updated in response to temperature fluctuations in the electrostatic sensor electrode 121, the control unit 131 will be unable to accurately calculate the difference value ΔAD when the temperature of the electrostatic sensor electrode 121 fluctuates. For this reason, the electrostatic input device 100 updates the reference value in a predetermined state. This will be described in detail later using a flowchart and the like.

[0067] <Temperature Sensor 140>

[0068] As an example, the temperature sensor 140 detects the temperature inside a vehicle in which the electrostatic input device 100 is mounted. The temperature inside the vehicle is an example of the temperature surrounding the electrostatic sensor electrode 121. The temperature sensor 140 is connected to the control device 130, and the temperature detected by the temperature sensor 140 is input to the control unit 131 of the control device 130.

[0069] <State Transition Diagram Showing Operation of Electrostatic Input Device 100>

[0070] Figure 3 This is a state transition diagram illustrating an example of the operation of the electrostatic input device 100. Here, the states of the electrostatic input device 100 are described starting with the disabled (Off) state. Control processing by the control unit 131 causes the state of the electrostatic input device 100 to transition as follows. Hereinafter, the difference value ΔAD will be referred to as the difference value ΔCapacity. The difference value ΔAD and the difference value ΔCapacity are equivalent. The difference value ΔAD and the difference value ΔCapacity are examples of the first difference value.

[0071] <Off status>

[0072] The "off" state is a state in which the electrostatic input device 100 is powered on but the fingertip FT is not in contact with (touching) the operation surface 105A, and the electrostatic input device 100 does not detect the touch operation of the fingertip FT on the operation surface 105A.

[0073] The "off" state is one of the proximity states of the electrostatic input device 100, determined by the control unit 131 to indicate that no touch operation is being performed on the operation surface 105A by the fingertip FT. The electrostatic input device 100 has two proximity states: "off" and "on." When the proximity state is "on," the operation surface 105A is being touched by the fingertip FT. When the proximity state is "off," the operation surface 105A is not being touched by the fingertip FT. In the "off" state, the reference value is updated using a known method.

[0074] <Transition from the disabled (Off) state to the enabled (On) state along 1) On>

[0075] In the Off state, if the difference value ΔCapacity exceeds the activation threshold ThOn, the electrostatic input device 100 transitions from 1) On to the Active state. The Active threshold ThOn is an example of a proximity threshold. The Active state occurs when the difference value ΔCapacity exceeds the activation threshold ThOn, causing the control unit 131 to determine that the fingertip FT is touching the operation surface 105A, and the proximity state of the electrostatic input device 100 is Active. The activation threshold ThOn is used to determine whether the proximity state is Active.

[0076] <From the On state, follow 2a) NormalTemperature to On_NormalTemperature>

[0077] In the On state, if the vehicle interior temperature detected by temperature sensor 140 exceeds a temperature threshold, electrostatic input device 100 transitions to the On_NormalTemperature state, following 2a) NormalTemperature. The temperature threshold, for example, is 15°C and is used to determine whether the temperature is low. The temperature threshold is the temperature limit at which changes in the sensitivity of electrostatic sensor electrode 121 cannot be ignored when the fingertip FT touches operation surface 105A and the temperature of sensor electrode 121 rises.

[0078] When the temperature of the electrostatic sensor electrode 121 is low and the slider 111 is operated for a relatively long period of several to ten seconds, the temperature of the electrostatic sensor electrode 121 rises due to the temperature of the fingertip FT, thereby increasing the measured value of the electrostatic capacitance of the electrostatic sensor electrode 121. To this end, the control unit 131 performs control processing based on the vehicle interior temperature detected by the temperature sensor 140.

[0079] When the vehicle interior temperature detected by the temperature sensor 140 is higher than the temperature threshold, the control unit 131 transitions to the On_NormalTemperature state to perform control processing in a normal state because there is no possibility of miscalculation of the difference value ΔCapacity.

[0080] <Transition from On_NormalTemperature state to Failure (Off) along 3a) Off>

[0081] In the On_NormalTemperature state, if the maximum value of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 falls below the failure threshold, the electrostatic input device 100 transitions to the failure state (Off) along the path 3a) Off. The failure threshold is used to determine whether the proximity state represents a failure.

[0082] <From the On state, follow 4) LowTemperature to On_LowTemperature>

[0083] In the On state, if the vehicle interior temperature detected by temperature sensor 140 is below the temperature threshold, electrostatic input device 100 transitions to the On_LowTemperature state, following 4) LowTemperature. In the On_LowTemperature state, control unit 131 performs control processing taking into account the effect of the temperature increase of electrostatic sensor electrode 121 associated with the operation of slider 111.

[0084] <From the On_LowTemperature state, follow 2b) NormalTemperature to On_NormalTemperature>

[0085] In the On_LowTemperature state, if the vehicle interior temperature detected by temperature sensor 140 exceeds a temperature threshold, electrostatic input device 100 transitions to the On_NormalTemperature state along 2b) NormalTemperature. This transition occurs from a low temperature state back to a high temperature state.

[0086] <Change the On_LowTemperature state to Monitoring along with 5) Decrease>

[0087] In the On_LowTemperature state, if the measured value of the electrostatic sensor electrode 121 drops significantly, the state of the electrostatic input device 100 transitions to the Monitoring state along the Decrease line 5). Monitoring is a state in which the proximity monitoring state is either enabled (On) or disabled (Off) when the measured value of the electrostatic sensor electrode 121 drops significantly. As described below, Monitoring consists of two states: Off_Monitoring and On_Monitoring. Both states transition from On_LowTemperature, which indicates a low temperature and is on. Therefore, there is a possibility that the reference value will vary significantly due to temperature fluctuations. Consequently, there is a risk that the control unit 131 will erroneously determine whether the device is on or off. In the present invention, in both Monitoring states, On / Off status and the need for updating the reference value are determined using criteria different from the known criteria (the relationship between the measured value and the threshold value). This allows for highly accurate On / Off determinations and a prompt and appropriate determination of the need for updating the reference value.

[0088] <Transition from Monitoring status to Off_Monitoring along 3) Off>

[0089] In the Monitoring state, if the maximum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 falls below the failure threshold, the electrostatic input device 100 transitions from state 3) Off to the Off_Monitoring state. The Off_Monitoring state is an example of a non-proximity monitoring state. In the Off_Monitoring state, even though the measured values ​​of the electrostatic sensor electrodes 121 have significantly decreased and the maximum differential value ΔCapacity has fallen below the failure threshold, the proximity monitoring state is still in effect (Off).

[0090] <Transition from Monitoring status to On_Monitoring along 6) NotOff>

[0091] In the Monitoring state, if the maximum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 exceeds the failure threshold, the electrostatic input device 100 transitions from the NotOff state (6) to the On_Monitoring state. The On_Monitoring state is a proximity monitoring state. In the On_Monitoring state, even though the measured values ​​of the electrostatic sensor electrodes 121 have significantly decreased, the maximum differential value ΔCapacity exceeds the failure threshold, confirming that the proximity monitoring state is truly active (On).

[0092] <Transition from Off_Monitoring to On_LowTemperature following 7) Increase>

[0093] In the Off_Monitoring state, if the total of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 increases significantly, it is considered that the fingertip FT that has left the operation surface 105A has reappeared. Therefore, the state of the electrostatic input device 100 transitions to the On_LowTemperature state along 7) Increase. This is to re-process in the On_LowTemperature state. In the Off_Monitoring state, there is a high probability that the fingertip FT has left the operation surface 105A. However, there is a slight possibility that the fingertip FT has not left the operation surface 105A. Therefore, if the control unit 131 updates the reference value, the reference value may be set to an incorrect value. If the reference value is incorrect, the control unit 131 cannot accurately determine the proximity state / non-proximity state (On / Off). By using the increase in the total of the five differential values ​​ΔCapacity, the proximity state (On) can be accurately determined regardless of the accuracy of the reference value.

[0094] <From the Off_Monitoring state, follow 9) Tiny to Off>

[0095] In the Off_Monitoring state, if the sum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 is extremely small, it is considered that the fingertip FT has left the operation surface 105A. Therefore, the state of the electrostatic input device 100 transitions to Off along the lines of 9) Tiny. When the control unit 131 confirms that the reference value has barely changed, it transitions from "Off_Monitoring," which performs monitoring unique to the present invention, to "Off," which performs processing similar to conventional techniques.

[0096] <From the Off_Monitoring state, follow 10) Calibrate1 to BaseReset>

[0097] In the Off_Monitoring state, if the sum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 fluctuates little, and if this state of small fluctuations in the sum of the differential values ​​ΔCapacity continues for a period exceeding the first update time for updating the reference value, it is considered that the fingertip FT has left the operation surface 105A. Since the conditions of 9) Tiny are not met, it is assumed that the reference value has fluctuated due to temperature and other factors. Therefore, the state of the electrostatic input device 100 transitions to BaseReset following 10) Calibrate1. The reference value stored in memory 132 is updated based on the values ​​measured by the electrostatic sensor electrodes 121. Once the reference value is updated, the state of the electrostatic input device 100 transitions to the Off state. Off_Monitoring is a state in which the differential values ​​decrease. If the differential values ​​decrease and the state of small fluctuations in the differential values ​​continues, there is a high probability that the fingertip FT has left the operation surface 105A. Conversely, if the fingertip FT is in contact with the operation surface 105A and does not move, the reference value is not updated. Since it is possible to accurately determine whether the fingertip FT has left the operation surface 105A, the first update time can be shortened, and the reference value can be quickly updated to a correct value.

[0098] <Change the status from On_Monitoring to On_LowTemperature according to 7) Increase>

[0099] In the On_Monitoring state, even if the sum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 fluctuates slightly, if the sum of ΔCapacity increases due to an operation such as bringing the finger closer again, the state transitions to the On_LowTemperature state according to 7) Increase. In other words, the process returns to a state where the fingertip FT is securely touching the operation surface 105A.

[0100] <Change from On_Monitoring to On_LowTemperature in 8)>

[0101] In the On_Monitoring state, if the sum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 fluctuates significantly, it is considered that the fingertip FT is moving on the operation surface 105A. When the fingertip FT moves on the operation surface 105A, the area of ​​contact between the electrostatic sensor electrodes 121 and the fingertip FT changes, causing the sum of the five differential values ​​ΔCapacity to fluctuate. Consequently, the electrostatic input device 100 transitions to the On_LowTemperature state according to 8) Change. In other words, the process returns to a state where the fingertip FT is reliably touching the operation surface 105A.

[0102] <Transition from On_Monitoring to Off_Monitoring along 3c) Off>

[0103] In the On_Monitoring state, if the maximum value MaxΔCapacity(i) among the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 is less than the failure threshold ThOff, the proximity state is considered to be Off. Therefore, the state of the electrostatic input device 100 transitions from 3c) Off to Off_Monitoring.

[0104] <From On_Monitoring state to BaseReset along with 11) Calibrate2>

[0105] In the On_Monitoring state, if the sum of the five differential values ​​ΔCapacity obtained from the five electrostatic sensor electrodes 121 fluctuates little, and if this state of small fluctuations in the sum of the differential values ​​ΔCapacity lasts longer than the second update time for updating the reference value, the reference value fluctuates regardless of the fingertip FT's position away from the operation surface 105A, indicating that the proximity state is in effect. Therefore, after the reference value is updated, the proximity state is set to off. That is, the state of the electrostatic input device 100 transitions to off following 11) Calibrate2 and BaseReset. The measured values ​​of the electrostatic sensor electrodes 121 are obtained, and the reference value stored in memory 132 is updated. Even if the fingertip FT is brought to rest while in contact with the operation surface 105A, the sum of the differential values ​​ΔCapacity remains small. Therefore, the second update time is set long to prevent the reference value from being updated to an erroneous value. However, the On_Monitoring state also indicates a decreasing differential value. If the difference value decreases and the fluctuation in the difference value continues to be small, the possibility that the fingertip FT has left the operation surface 105A is high. In other words, it can be determined with high accuracy that the fingertip FT has left the operation surface 105A.

[0106] <Flowchart>

[0107] Figures 4A to 4D This is a flowchart showing an example of processing executed by the control unit 131 of the electrostatic input device 100 .

[0108] When the process starts (Start), the control unit 131 stores the default value in each variable (step S1). Specifically, it means that Off is substituted for the proximity status Status and 0 is substituted for the MonitoringTime. The "=" in the flowchart means that the variable on the left is substituted for the value on the right. That is, it means the operation of assigning values ​​to variables. The proximity status Status is a variable indicating whether it is effective (On) or ineffective (Off). That is, if the indicator FT is close to the electrostatic sensor electrode 121, the control unit 131 substitutes On for the proximity status Status. On the other hand, if the indicator FT is not close to the electrostatic sensor electrode 121, the control unit 131 substitutes Off for the proximity status Status. MonitoringTime is a variable indicating the duration Figure 3 The time variable of the Off_Monitoring state is shown.

[0109] The control unit 131 determines whether the maximum value MaxΔCapacity(i) among the plurality of differential values ​​ΔCapacity(i) is greater than the activation threshold ThOn (step S2). i represents the i-th differential value ΔCapacity. If there are five electrostatic sensor electrodes 121, i can take values ​​from 1 to 5. The activation threshold ThOn is an example of a proximity threshold.

[0110] If it is determined that the maximum value MaxΔCapacity(i) is greater than the activation threshold value ThOn ( S2 : Yes), the control unit 131 sets the proximity status Status to On (step S3 ).

[0111] In step S2 , when the control unit 131 determines that the maximum value MaxΔCapacity(i) is not greater than the activation threshold value ThOn ( S2 : No), the process of step S2 is performed again.

[0112] The control unit 131 determines whether the vehicle interior temperature (Temperature) detected by the temperature sensor 140 is lower than the temperature threshold (ThTemp) (step S4). This is to determine whether the temperature of the electrostatic sensor electrode 121 has decreased. In the absence of the temperature sensor 140, the temperature can be determined using a reference value. As the temperature decreases, the sensitivity of the electrostatic sensor decreases, and the reference value decreases. Therefore, if the reference value is lower than a given value, the process branches to S4: Yes; if the reference value is higher than the given value, the process branches to S4: No.

[0113] If the vehicle interior temperature (Temperature) detected by temperature sensor 140 is determined to be no less than the temperature threshold (ThTemp) ( S4 : No), control unit 131 determines whether maximum value MaxΔCapacity(i) is less than failure threshold ThOff (step S5 ). This is to determine whether fingertip FT has left operation surface 105A while the vehicle interior temperature is still high. Failure threshold ThOff is a non-approach threshold.

[0114] If the maximum value MaxΔCapacity(i) is determined to be not less than the failure threshold ThOff ( S5 : No), the control unit 131 repeats the process of step S5. If the maximum value MaxΔCapacity(i) is determined to be less than the failure threshold ThOff ( S5 : Yes), the proximity status Status is set to Off (step S6). In other words, Status = Off is processed. The control unit 131 updates the reference value using a well-known method (not shown).

[0115] After the processing of step S6 is completed, the control unit 131 returns the flow to step S2 to prepare for the next operation.

[0116] If, in step S4, it is determined that the vehicle interior temperature (Temperature) detected by temperature sensor 140 is lower than the temperature threshold (ThTemp) (S4: YES), control unit 131 stores the total difference value ΣΔCapacity(i), which is the sum of the five most recent difference values ​​ΔCapacity(i), in memory 132 as the low-temperature total difference value (EnterLowTemperatureSum) when the vehicle interior temperature decreases (step S7). In other words, EnterLowTemperatureSum = ΣΔCapacity(i).

[0117] The control unit 131 determines whether the total difference value ΣΔCapacity(i) is greater than the maximum value (MaxCapacitySum) of the total difference values ​​ΣΔCapacity(i) up to that point in time (step S8 ). In other words, the control unit 131 determines whether MaxCapacitySum<ΣΔCapacity(i).

[0118] If the total difference value ΣΔCapacity(i) is determined to be greater than the maximum value (MaxCapacitySum) ( S8 : Yes), the control unit 131 substitutes the maximum value (MaxCapacitySum) of the total difference values ​​ΣΔCapacity(i) up to that point into the total difference value ΣΔCapacity(i) (step S9 ). In other words, MaxCapacitySum = ΣΔCapacity(i) is processed. The control unit 131 completes step S9 and proceeds to step S10 .

[0119] When the control unit 131 determines in step S8 that the total difference value ΣΔCapacity(i) is not greater than the maximum value (MaxCapacitySum) ( S8 : No), the process of step S9 is skipped and the flow proceeds to step S10 .

[0120] Alternatively, in step S8, instead of determining whether the total difference value ΣΔCapacity(i) is greater than the maximum value (MaxCapacitySum) of the total difference values ​​ΣΔCapacity(i) up to that point in time, the control unit 131 may determine whether each of the five difference values ​​ΔCapacity(i) is greater than the maximum value (MaxCapacitySum). If at least one of the five difference values ​​ΔCapacity(i) is greater than the maximum value (MaxCapacitySum), the control unit 131 may simply proceed to step S9. If all five difference values ​​ΔCapacity(i) are less than the maximum value (MaxCapacitySum), the control unit 131 may skip step S9 and proceed to step S10.

[0121] Thus, instead of the total difference value ΣΔCapacity(i), comparing each of the five difference values ΔCapacity(i) with a comparison object value is the same in the process using the total difference value ΣΔCapacity(i) described later.

[0122] The control unit 131 determines whether the in-vehicle temperature (Temperature) detected by the temperature sensor 140 is lower than the temperature threshold (ThTemp) (step S10). This is to determine whether the temperature of the electrostatic sensor electrode 121 has decreased. Additionally, when the temperature sensor 140 is not used, the determination in step S10 is omitted.

[0123] [[ID=X]]If it is determined that the in-vehicle temperature (Temperature) detected by the temperature sensor 140 is not lower than the temperature threshold (ThTemp) (S10: No), the control unit 131 advances the process to step S5. This is to determine whether the fingertip FT has left the operation surface 105A in a state where the in-vehicle temperature is not low.

[0124] If it is determined that the in-vehicle temperature (Temperature) detected by the temperature sensor 140 is lower than the temperature threshold (ThTemp) (S10: Yes), the control unit 131 determines whether the value obtained by subtracting the latest total difference value ΣΔCapacity(i) from the maximum value (MaxCapacitySum) of the total difference values ΣΔCapacity(i) up to that time point is greater than half of the low-temperature total difference value (EnterLowTemperatureSum) (step S11). That is, the control unit 131 determines whether EnterLowTemperatureSum / 2 < MaxCapacitySum - ΣΔCapacity(i) holds. Step S11 is a process for determining whether the latest total difference value ΣΔCapacity(i) has decreased. MaxCapacitySum - ΣΔCapacity(i) is an example of the second difference value. Half of the low-temperature total difference value (EnterLowTemperatureSum / 2) is an example of the reduction threshold. The constant (1 / 2) multiplied by the low-temperature total difference value is an example of the first constant. The first constant is not limited to 1 / 2 and can be a suitable value.

[0125] If the latest total difference value ΣΔCapacity(i) decreases, there may be a situation where the fingertip FT has left the operation surface 105A. Therefore, the process of step S11 is performed to monitor whether the reference value needs to be updated.

[0126] Note: In the translation of line [8], the variable "FT" is not defined in the original text, so I assume it is an abbreviation and keep it as "FT" in the translation. If there is more context to clarify its meaning, a more accurate translation can be provided.If it is determined that EnterLowTemperatureSum / 2 < MaxCapacitySum - ΣΔCapacity(i) does not hold (S11: No), the control unit 131 returns the process to step S8. This is because, since the latest total difference value ΣΔCapacity(i) is not low, it is compared with the maximum value (MaxCapacitySum).

[0127] If the control unit 131 determines in step S11 that EnterLowTemperatureSum / 2 < MaxCapacitySum - ΣΔCapacity(i) holds (S11: Yes), it stores the latest ΣΔCapacity(i) as the total difference value (EnterMonitoringSum) at the start of monitoring in the memory 132 (step S12). That is, the control unit 131 substitutes ΣΔCapacity(i) into EnterMonitoringSum.

[0128] The control unit 131 determines whether the maximum value MaxΔCapacity(i) among the five latest ΣΔCapacity(i) is less than the failure threshold ThOff (step S13). That is, the control unit 131 determines whether MaxΔCapacity(i) < ThOff holds. This is to confirm the approaching state.

[0129] If the control unit 131 determines that the maximum value MaxΔCapacity(i) is less than the failure threshold ThOff (S13: Yes), it sets the approaching state to failure (step S14). That is, the process of Status = Off is performed.

[0130] In addition, if the control unit 131 determines in step S13 that the maximum value MaxΔCapacity(i) is not less than the failure threshold ThOff (S13: No), the process proceeds to step S23. This is because, since the approaching state is effective and the maximum value MaxΔCapacity(i) is relatively large, the process enters the process of determining whether to update the reference value (after step S23). The processing after step S23 will be described later.

[0131] If the control unit 131 finishes the processing of step S14, it determines whether the value obtained by subtracting the latest total difference value ΣΔCapacity(i) from the maximum value (MaxCapacitySum) of the total difference values ΣΔCapacity(i) up to that time point is less than 2 / 5 of the low-temperature total difference value (EnterLowTemperatureSum) (step S15). That is, the control unit 131 determines whether EnterLowTemperatureSum×2 / 5 > MaxCapacitySum - ΣΔCapacity(i) holds. Step S15 is a process for determining whether the latest total difference value ΣΔCapacity(i) has increased significantly. If the total difference value ΣΔCapacity(i) has increased significantly, the control unit 131 determines that the fingertip FT has touched the operation surface 105A. The constant (2 / 5) multiplied by the low-temperature total difference value is an example of the second constant. The second constant is not limited to 2 / 5 and can be a suitable value.

[0132] If the control unit 131 determines that EnterLowTemperatureSum×2 / 5 > MaxCapacitySum - ΣΔCapacity(i) does not hold (S15: No), it determines whether the latest total difference value ΣΔCapacity(i) is less than the minimum change threshold ThTiny (step S16). That is, the control unit 131 determines whether ΣΔCapacity(i) < ThTiny holds.

[0133] If the control unit 131 determines that the latest total difference value ΣΔCapacity(i) is less than the minimum change threshold ThTiny (S16: Yes), it performs the process of MonitoringTime = 0 (step S17). That is, the control unit 131 substitutes 0 into MonitoringTime. Since MonitoringTime represents the time in the state of continuously Off_Monitoring (reference Figure 3 ), therefore, MonitoringTime becoming zero is equivalent to ending the state of Off_Monitoring (reference Figure 3 ).

[0134] If the processing of step S17 is finished, the control unit 131 returns the flow to step S2. Returning to step S2 is equivalent to the state where 9) Tiny migrates to off. Step S2 determines whether the approach state takes effect.

[0135] When the process advances from step S16 to step S17, the proximity state is invalid, and the latest change in the total difference value ΣΔCapacity(i) is extremely small, so it is assumed that no touch has actually occurred. In this state, the reference value stored in memory 132 is considered appropriate, so the reference value is not updated and the proximity state is set to invalid.

[0136] If it is determined in step S16 that the latest total difference value ΣΔCapacity(i) is not less than the minimum change threshold value ThTiny ( S16 : NO), the control unit 131 increments MonitoringTime (step S18 ).

[0137] Control unit 131 determines whether MonitoringTime has exceeded first update time ThCalibrateTime1 (step S19). In other words, control unit 131 determines whether MonitoringTime > ThCalibrateTime1. Because step S19 assumes that fingertip FT is not touching operation surface 105A, first update time ThCalibrateTime1 is shorter than second update time ThCalibrateTime2 (described later). First update time ThCalibrateTime1 and second update time ThCalibrateTime2 are examples of predetermined times.

[0138] If it is determined that MonitoringTime has not passed the first update time ThCalibrateTime1 ( S19 : No), the control unit 131 returns the flow to step S15 . By repeating the loop of steps S15 , S16 , S18 , and S19 and returning to step S15 , the value of MonitoringTime increases.

[0139] If the control unit 131 determines in step S19 that MonitoringTime has exceeded the first update time ThCalibrateTime1 ( S19 : YES), the control unit 131 sets MonitoringTime to zero (step S20 ). That is, the control unit 131 performs the process of MonitoringTime=0 and ends the Off_Monitoring state.

[0140] The control unit 131 updates the reference value (step S21). The control unit 131 sets the value (ΣΔCapacity(i) / i) obtained by dividing the total difference value ΣΔCapacity(i), the sum of the five most recent difference values ​​ΔCapacity(i), by the number of electrostatic sensor electrodes 121 (5) as the reference value (Base). In other words, the process of Base = (ΣΔCapacity(i)) / i is performed, and ΣΔCapacity(i) / i is stored in the memory 132 as the new reference value. This process corresponds to the transition to the BaseReset state in step 10) Calibrate1.

[0141] In this manner, when the vehicle interior temperature detected by the temperature sensor 140 is lower than the temperature threshold ThTemp and no touch operation is performed, the reference value is updated to correspond to the vehicle interior temperature.

[0142] After the processing of step S20 is completed, the control unit 131 returns to step S2. Returning to step S2 is equivalent to transitioning to the Off state. After returning to step S2, the control unit 131 determines whether the proximity state is valid. The updated reference value is used to determine the proximity state.

[0143] When the process proceeds from step S16 to step S17, the proximity status is set to "invalid" and the latest total difference value ΣΔCapacity(i) is extremely small, so it is assumed that the hand is not approaching electrostatic sensor 120. This indicates that the difference between each difference value ΔCapacity(i) and the reference value (base value) is minimal. Since the reference value stored in memory 132 is an appropriate value, the reference value is not updated, and the proximity status is set to "invalid".

[0144] If it is determined in step S15 that EnterLowTemperatureSum × 2 / 5 > MaxCapacitySum - ΣΔCapacity(i) ( S15 : YES), the control unit 131 sets MonitoringTime to zero (step S22 ). In other words, the control unit 131 sets MonitoringTime = 0. A YES determination in step S15 indicates that the value of MaxCapacitySum - ΣΔCapacity(i) decreases as ΣΔCapacity(i) increases.

[0145] "End the process of step S22 and return the process to step S8" is equivalent to migrating from the state of Off_Monitoring to the state of On_LowTemperature along 7) Increase. Since it is not the state of Off_Monitoring, the control unit 131 sets MonitoringTime to zero (step S22). If the process of step S22 is ended, the control unit 131 returns the process to step S8 and determines whether the latest total difference value ΣΔCapacity(i) is greater than the maximum value (MaxCapacitySum) of the total difference value ΣΔCapacity(i) up to that point in time.

[0146] If it is determined in step S13 that the maximum value MaxΔCapacity(i) is not less than the failure threshold ThOff (S13: No), the control unit 131 determines whether the value obtained by subtracting the latest total difference value ΣΔCapacity(i) from the maximum value (MaxCapacitySum) of the total difference value ΣΔCapacity(i) up to that point in time is less than 2 / 5 of the low-temperature total difference value (EnterLowTemperatureSum) (step S23). The process of step S23 is the same as the process of step S15, and the control unit 131 determines whether EnterLowTemperatureSum×2 / 5 > MaxCapacitySum - ΣΔCapacity(i) holds. Step S23 is a process for determining whether the latest total difference value ΣΔCapacity(i) has increased significantly. If the total difference value ΣΔCapacity(i) has increased significantly, the control unit 131 determines whether the fingertip FT has reliably touched the operation surface 105A.

[0147] If it is determined that EnterLowTemperatureSum×2 / 5 > MaxCapacitySum - ΣΔCapacity(i) does not hold (S23: No), the control unit 131 determines whether ΣΔCapacity(i) - EnterMonitoringSum > ThChange1 or ΣΔCapacity(i) - EnterMonitoringSum < ThChange2 holds (step S24).

[0148] ΣΔCapacity(i) - EnterMonitoringSum > ThChange1 is a process of determining whether the value obtained by subtracting the cumulative difference value EnterMonitoringSum at the start of Monitoring from the cumulative difference value ΣΔCapacity(i) is greater than the positive first change constant ThChange1 when the cumulative difference value ΣΔCapacity(i) increases. If the fingertip FT is moved on the operation surface 105A, the opposed area between the fingertip FT and the electrostatic sensor electrode 121 changes, and the cumulative difference value ΣΔCapacity(i) changes. If the cumulative difference value ΣΔCapacity(i) changes, the control unit 131 determines that the fingertip FT reliably touches the operation surface 105A.

[0149] ΣΔCapacity(i) - EnterMonitoringSum < ThChange2 is a process of determining whether the value obtained by subtracting the cumulative difference value EnterMonitoringSum at the start of Monitoring from the cumulative difference value ΣΔCapacity(i) is less than the negative second change constant ThChange2 when the cumulative difference value ΣΔCapacity(i) decreases. If the fingertip FT is moved on the operation surface 105A, the opposed area between the fingertip FT and the electrostatic sensor electrode 121 changes, and the cumulative difference value ΣΔCapacity(i) changes. In the On_Monitoring state, if the cumulative difference value ΣΔCapacity(i) changes, the control unit 131 determines that the fingertip FT reliably touches the operation surface 105A.

[0150] If it is determined that neither ΣΔCapacity(i) - EnterMonitoringSum > ThChange1 nor ΣΔCapacity(i) - EnterMonitoringSum < ThChange2 holds (S24: No), the control unit 131 determines whether the maximum value MaxΔCapacity(i) among the five latest ΣΔCapacity(i) is less than the failure threshold ThOff (step S25). That is, the control unit 131 determines whether MaxΔCapacity(i) < ThOff holds. This is to confirm the proximity state.

[0151] If it is determined that the maximum value MaxΔCapacity(i) is not less than the failure threshold ThOff (S25: No), the control unit 131 increments MonitoringTime (step S26). That is, the process of MonitoringTime = MonitoringTime + 1 is performed.

[0152] Control unit 131 determines whether MonitoringTime has exceeded second update time ThCalibrateTime2 (step S27). In other words, control unit 131 determines whether MonitoringTime > ThCalibrateTime2. Because step S27 is performed while fingertip FT is in contact with operation surface 105A, second update time ThCalibrateTime2 is longer than first update time ThCalibrateTime1 used in step S19.

[0153] If it is determined that MonitoringTime has not passed the second update time ThCalibrateTime2 ( S27 : No), the control unit 131 returns the flow to step S23 .

[0154] If it is determined in step S27 that MonitoringTime has passed the second update time ThCalibrateTime2 (S27: YES), the control unit 131 updates the reference value (step S28). The control unit 131 sets the value (ΣΔCapacity(i) / i) obtained by dividing the total difference value ΣΔCapacity(i), the sum of the five most recent difference values ​​ΔCapacity(i), by the number of electrostatic sensor electrodes 121 (5), as the reference value (Base). In other words, the calculation Base = (ΣΔCapacity(i)) / i is performed. ΣΔCapacity(i) / i is stored in the memory 132 as the new reference value.

[0155] The control unit 131 sets the proximity status to disabled (step S29 ). That is, it substitutes Off into Status.

[0156] In this manner, when the vehicle interior temperature detected by the temperature sensor 140 is lower than the temperature threshold ThTemp and no touch operation is performed, the reference value is updated to correspond to the vehicle interior temperature.

[0157] The flow proceeding from step S28 to step S29 corresponds to a case where the state transitions from the Off state to the BaseReset state.

[0158] The control unit 131 sets MonitoringTime to zero (step S30). That is, the control unit 131 sets MonitoringTime = 0. When the process goes from step S28 to step S29 and then to step S30, it is equivalent to Figure 3 11) Calibrate2 turns Off via BaseReset.

[0159] In addition, if it is determined in step S5 that the maximum value MaxΔCapacity(i) is less than the failure threshold ThOff (S25: Yes), the control unit 131 sets MonitoringTime to zero (step S30). That is, the control unit 131 sets MonitoringTime = 0.

[0160] In addition, if it is determined in step S23 that EnterLowTemperatureSum×2 / 5 > MaxCapacitySum - ΣΔCapacity(i) holds (S23: Yes), the control unit 131 substitutes zero into MonitoringTime (step S32). That is, the control unit 131 performs the process of MonitoringTime = 0.

[0161] In addition, if it is determined in step S24 that ΣΔCapacity(i) - EnterMonitoringSum > ThChange1 or ΣΔCapacity(i) - EnterMonitoringSum < ThChange2 holds (S24: Yes), the control unit 131 substitutes zero into MonitoringTime (step S32). That is, the control unit 131 performs the process of MonitoringTime = 0.

[0162] When the process of step S32 is completed, the flow returns to step S8. That is, if the sum ΣΔCapacity(i) of the difference values fluctuates or increases significantly, it migrates to the On_LowTemperature state. If it returns to step S8, it is determined whether the latest sum difference value ΣΔCapacity(i) is greater than the maximum value (MaxCapacitySum) of the sum difference value ΣΔCapacity(i) up to that time point.

[0163] <First Modified Example>

[0164] Figure 5 FIG. is an example showing the structure of the electrostatic input device 100M1 according to the first modified example of the embodiment. The electrostatic input device 100M1 includes an electrostatic sensor 120M1 in place of Figure 2 the electrostatic sensor 120 of the shown electrostatic input device 100. The electrostatic sensor 120M1 has: a plurality of electrostatic sensor electrodes 121X extending in the X direction; and a plurality of electrostatic sensor electrodes 121Y extending in the Y direction. The measurement circuit 125A sequentially selects the plurality of electrostatic sensor electrodes 121X and the plurality of electrostatic sensor electrodes 121Y, and measures the electrostatic capacitance at the intersection. In such an electrostatic sensor 120M1, the contact position of the finger can be detected.

[0165] <Second Modified Example>

[0166] Figure 6 100M2 is a diagram showing an example of the structure of an electrostatic input device 100M2 according to a second modified example of the embodiment. The electrostatic input device 100M2 includes an electrostatic sensor 120M2 in place of Figure 2 The electrostatic sensor 120 of the electrostatic input device 100 shown does not include the display 110. The electrostatic sensor 120M2 has only one electrostatic sensor electrode 121. The measurement circuit 125A measures the electrostatic capacitance of the electrostatic sensor electrode 121. This can also be applied to such a single electrostatic sensor 120M2.

[0167] <Effect>

[0168] The electrostatic input device 100 includes: a plurality of electrostatic sensor electrodes 121; a measurement circuit 125A that outputs a measurement value based on the electrostatic capacitance between each of the plurality of electrostatic sensor electrodes 121 and a pointer; a control unit 131 that determines whether the pointer is in a proximity state, in which the pointer is approaching the plurality of electrostatic sensor electrodes 121, based on the measurement value output by the measurement circuit 125A; and a memory 132 that stores the measurement value when the pointer is not approaching the plurality of electrostatic sensor electrodes 121 as a reference value (Base). The control unit 131 determines whether the pointer is in a proximity state based on a difference value ΔCapacity obtained by subtracting the reference value from the measurement value, calculates a total difference value ΣΔCapacity(i) that is the sum of the plurality of difference values ​​ΔCapacity of the plurality of electrostatic sensor electrodes 121, and updates the reference value (S21, S28) if, in the proximity state, the change in the total difference value ΣΔCapacity(i) remains less than a given value after the total difference value ΣΔCapacity(i) decreases and the state continues for a given time or longer (S27: YES). To this end, even when the fingertip FT is separated from the operation surface 105A, the reference value is rapidly updated if the temperature change of the electrostatic sensor electrode 121 erroneously determines that the fingertip is in proximity. Conventionally, the reference value is updated when the fluctuation in the total differential value ΣΔCapacity(i) remains small for a long period of time. However, if the reference value is updated only when the fluctuation in ΣΔCapacity(i) is small, there is a possibility that the reference value will be updated while the finger remains in contact with the sensor surface and is not moving. The present invention combines the two conditions of "the total differential value ΣΔCapacity(i) decreases" and "the fluctuation in the total differential value ΣΔCapacity(i) remains less than a given value for a given period of time or longer." This prevents the reference value from being updated while the finger remains in contact with the sensor surface and is not moving. This allows for rapid updating of the reference value while preventing erroneous operation.

[0169] Therefore, there is provided an electrostatic input device 100 that can suppress updating of a reference value to a measurement value in a state where the finger is in contact with the sensor surface even when the finger is stopped while the finger is in contact with the sensor surface.

[0170] Alternatively, control unit 131 may store the total difference value ΣΔCapacity(i) at the time when total difference value ΣΔCapacity(i) reached its maximum value as maximum total difference value MaxCapacitySum in memory 132 ( S8 , S9 ). If a second difference value MaxCapacitySum - ΣΔCapacity(i), obtained by subtracting the most recent total difference value ΣΔCapacity(i) from the maximum total difference value MaxCapacitySum, is greater than a decrease threshold value EnterLowTemperatureSum / 2, control unit 131 may determine that total difference value ΣΔCapacity(i) has decreased ( S11 : Yes). Even if temperature fluctuations in electrostatic sensor 120 prevent accurate determination of proximity / non-proximity, the possibility of a finger being removed from operation surface 105A can be detected.

[0171] Furthermore, when the ambient temperature of the plurality of electrostatic sensor electrodes 121 falls below the temperature threshold (ThTemp) ( S4 ), the control unit 131 stores the total difference value ΣΔCapacity(i) determined to be in the proximity state ( S2 ) as the low-temperature total difference value EnterLowTemperatureSum in the memory 132 ( S7 ). The reduction threshold EnterLowTemperatureSum / 2 may be the first constant (1 / 2) times the low-temperature total difference value ΣΔCapacity(i). By using a relative value such as the low-temperature total difference value EnterLowTemperatureSum, the latest reduction in the total difference value ΣΔCapacity(i) can be appropriately determined regardless of the temperature.

[0172] Furthermore, control unit 131 determines a proximity state (S2) when any of the plurality of difference values ​​ΔCapacity exceeds a proximity threshold (ThOn), and determines a non-proximity state (S13) when any of the plurality of difference values ​​ΔCapacity is less than a non-proximity threshold (ThOff). In the proximity state, if any of the plurality of difference values ​​ΔCapacity exceeds the non-proximity threshold (S13: No) after the total difference value ΣΔCapacity(i) is determined to have decreased (S11: Yes), the control unit 131 transitions to a proximity monitoring state (On_Monitoring: S23). In the proximity state, if the increase in the total difference value ΣΔCapacity(i) exceeds a predetermined value, a proximity state is determined (activated) (S15: Yes). If the total difference value ΣΔCapacity(i) increases, it indicates that the fingertip FT is clearly touching operation surface 105A, and by determining a proximity state, the proximity state can be accurately determined.

[0173] Alternatively, control unit 131 may determine that total difference value ΣΔCapacity(i) has increased if second difference value MaxCapacitySum-ΣΔCapacity(i) falls below an increase threshold. By using the second difference value MaxCapacitySum-ΣΔCapacity(i) between the maximum total difference value MaxCapacitySum when fingertip FT is in contact with operation surface 105A with the largest area and the most recent total difference value ΣΔCapacity(i), the increase in the most recent total difference value ΣΔCapacity(i) can be accurately detected.

[0174] Alternatively, the increase threshold may be the second constant multiple (2 / 5) of the low-temperature total difference value ΣΔCapacity(i). By using a relative value such as the low-temperature total difference value ΣΔCapacity(i), the approach of the fingertip FT to the operation surface 105A can be appropriately determined regardless of the temperature.

[0175] Furthermore, control unit 131 determines that a proximity state exists (S2) when any of the plurality of difference values ​​ΔCapacity exceeds a proximity threshold value (ThOn). In the proximity state, if it is determined that the total difference value ΣΔCapacity(i) is decreasing (S11: YES), then if the plurality of difference values ​​ΔCapacity are less than the non-proximity threshold value (S13: YES), the controller 131 transitions to a non-proximity monitoring state (Off Monitoring). Alternatively, control unit 131 may transition to a proximity state if the total difference value ΣΔCapacity(i) changes in either the proximity monitoring state or the non-proximity monitoring state. By determining that the fingertip FT is approaching electrostatic sensor 120 when the total difference value ΣΔCapacity(i) changes, it is possible to appropriately determine that the fingertip FT has contacted operation surface 105A.

[0176] Furthermore, control unit 131 may transition to the approach state when the difference value obtained by subtracting the low-temperature total difference value ΣΔCapacity(i) from the total difference value ΣΔCapacity(i) is greater than a positive first variation constant, or when the difference value obtained by subtracting the low-temperature total difference value ΣΔCapacity(i) from the total difference value ΣΔCapacity(i) is less than a negative second variation constant. By comparing a relative value such as the low-temperature total difference value ΣΔCapacity(i) with the constant, it is possible to appropriately determine the approach of fingertip FT to operation surface 105A.

[0177] Furthermore, if the non-proximity monitoring state continues for longer than the first update time, or the proximity monitoring state continues for longer than the second update time, control unit 131 updates the reference value, and the first update time may be shorter than the second update time. By using separate thresholds (the first update time and the second update time) for determination in the non-proximity monitoring state and the proximity monitoring state, the timing for updating the reference value can be accurately and quickly determined.

[0178] Furthermore, if the total difference value ΣΔCapacity(i) is smaller than a predetermined minimum threshold value (ThTiny) in the non-approach monitoring state, the control unit 131 may transition to the non-approach state without updating the reference value.

[0179] Furthermore, the system includes a temperature sensor for measuring the ambient temperature of the multiple electrostatic sensor electrodes 121. When the ambient temperature of the multiple electrostatic sensor electrodes 121 is below a temperature threshold (ThTemp) (S4), the control unit 131 can determine whether a proximity state exists, calculate the total difference value ΣΔCapacity(i), and update the reference value. If a fingertip begins to touch the operation surface 105A at low temperatures, there is a possibility that the temperature of the electrostatic sensor 120 will rise rapidly due to heating during operation. Furthermore, if fingertip operation is continued at low temperatures, there is a possibility that the temperature of the electrostatic sensor 120 will rise rapidly due to body heat. By limiting this operation to cases where a fingertip begins to touch the operation surface 105A at low temperatures, the timing of updating the reference value can be optimized.

[0180] Furthermore, the control unit 131 may perform the aforementioned processing only when the temperature at the time of the approach state is lower than a predetermined value (S4). This provides an electrostatic input device 100 that, when the temperature inside the vehicle is low at the time of the approach state, can prevent the incorrect reference value from being updated by mistakenly determining that no approach operation has been performed, even when the finger is stopped while in contact with the sensor surface, by performing the aforementioned processing.

[0181] The electrostatic input device 100 includes an electrostatic sensor electrode 121; a measurement circuit 125A that outputs a measurement value based on the electrostatic capacitance between the electrostatic sensor electrode 121 and the pointer; a control unit 131 that determines whether the pointer is approaching the electrostatic sensor electrode 121 based on the measurement value output by the measurement circuit 125A; and a memory 132 that stores the measurement value when the pointer is not approaching the electrostatic sensor electrode 121 as a reference value (Base). The control unit 131 determines whether the pointer is in the proximity state based on a difference value ΔCapacity obtained by subtracting the reference value from the measurement value. In the proximity state, if the difference value ΔCapacity decreases and the change in the difference value ΔCapacity is less than a predetermined value for a predetermined period of time or longer (S27: YES), the reference value is updated. Therefore, if the fingertip FT is separated from the operation surface 105A but the pointer is mistakenly determined to be in the proximity state due to a temperature change in the electrostatic sensor electrode 121, the reference value is quickly updated.

[0182] Therefore, even if the sensitivity of the electrostatic sensor electrode 121 changes due to temperature changes, etc., the reference value can be quickly updated. Furthermore, it is possible to provide an electrostatic input device 100 that can prevent the reference value from being updated to an incorrect value by mistakenly determining that the finger has been removed from the operation surface even when the finger is stopped while the finger is in contact with the operation surface.

[0183] As mentioned above, the electrostatic input device according to the exemplary embodiment of the present disclosure has been described. However, the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and changes can be made without departing from the scope of the claims.

Claims

1. An electrostatic input device, characterized in that: Include: a plurality of electrostatic sensor electrodes; a measurement circuit that outputs a measurement value based on the electrostatic capacitance between each of the plurality of electrostatic sensor electrodes and the indicator; a control unit that determines whether the pointer is in a proximity state with respect to the plurality of electrostatic sensor electrodes based on the measurement value output by the measurement circuit; and a storage unit that stores the measurement value in a state where the indicator is not close to the plurality of electrostatic sensor electrodes as a reference value, The control unit performs the following processing: determining whether the proximity state is present based on a first difference value obtained by subtracting the reference value from the measured value, calculating a total difference value obtained by summing the plurality of first difference values ​​of the plurality of electrostatic sensor electrodes; In the approaching state, if a state in which a change amount of the total difference value is smaller than a predetermined value continues for a predetermined time or longer after the total difference value decreases, the reference value is updated.

2. The electrostatic input device according to claim 1, wherein: The control unit performs the following processing: The total difference value when the total difference value is the highest is stored in the storage unit as the maximum total difference value, When a second difference value obtained by subtracting the latest total difference value from the maximum total difference value is larger than a decrease threshold value, it is determined that the total difference value has decreased.

3. The electrostatic input device according to claim 2, wherein: The control unit stores the total difference value determined to be in the proximity state as a low-temperature total difference value in the storage unit when the ambient temperature of the plurality of electrostatic sensor electrodes is lower than a temperature threshold value. The reduction threshold is a first constant multiple of the low temperature total difference value.

4. The electrostatic input device according to claim 3, wherein: The control unit performs the following processing: When any one of the plurality of first difference values ​​is larger than the proximity threshold, it is determined that the state is the proximity state. When the plurality of first difference values ​​are smaller than the non-proximity threshold, it is determined to be a non-proximity state. In the proximity state, if it is determined that any one of the plurality of first difference values ​​exceeds the non-proximity threshold value after the total difference value decreases, the state transitions to the proximity monitoring state. In the proximity state, if it is determined that the plurality of first difference values ​​are less than the non-proximity threshold value after the total difference value decreases, the state transitions to the non-proximity monitoring state. In the proximity monitoring state or the non-proximity monitoring state, if the increase in the total difference value is larger than a predetermined value, it is determined that the proximity state has been established.

5. The electrostatic input device according to claim 4, wherein: If the second difference value becomes smaller than an increase threshold value, the control unit determines that the total difference value has increased.

6. The electrostatic input device according to claim 5, wherein: The increase threshold is a second constant times the low temperature total difference value.

7. The electrostatic input device according to claim 5, wherein: In the proximity monitoring state, if the total difference value changes, the control unit transitions to the proximity state.

8. The electrostatic input device according to claim 7, wherein: When the difference value obtained by subtracting the low-temperature total differential value from the total differential value is greater than the positive first change constant, or when the difference value obtained by subtracting the low-temperature total differential value from the total differential value is less than the negative second change constant, the control unit transitions to the approach state.

9. The electrostatic input device according to claim 8, wherein: If the non-approach monitoring state continues for longer than a first update time, or if the approach monitoring state continues for longer than a second update time, the control unit updates the reference value. The first update time is shorter than the second update time.

10. The electrostatic input device according to claim 8, wherein: In the non-approach monitoring state, if the total difference value is smaller than a predetermined minimum threshold value, the control unit transitions to the non-approach state without updating the reference value.

11. The electrostatic input device according to any one of claims 1 to 10, wherein: The electrostatic input device further includes a temperature sensor for measuring the ambient temperature of the plurality of electrostatic sensor electrodes. When the ambient temperature of the plurality of electrostatic sensor electrodes is lower than a temperature threshold and it is determined that the state is in the proximity state, the control unit performs the process according to any one of claims 1 to 10.

12. The electrostatic input device according to any one of claims 1 to 10, wherein: When the reference value is lower than a value corresponding to the reference value in a predetermined low-temperature state, and it is determined that the state is close to the reference value, the control unit performs the processing according to any one of claims 1 to 10.

13. An electrostatic input device, characterized in that: Include: electrostatic sensor electrodes; a measurement circuit whose output is based on a measurement value of the electrostatic capacitance between the electrostatic sensor electrode and the indicator; a control unit that determines, based on the measurement value output by the measurement circuit, whether the pointer is in a proximity state with respect to the electrostatic sensor electrode; and a storage unit that stores the measurement value in a state where the indicator is not close to the electrostatic sensor electrode as a reference value, The control unit performs the following processing: determining whether the proximity state is present based on a first difference value obtained by subtracting the reference value from the measured value, In the approaching state, if a state in which a change amount of the first difference value is smaller than a predetermined value continues for a predetermined time or longer after the first difference value decreases, the reference value is updated.

Images