Contact detection device

Abstract

A contact detection device (10) is provided with an electrostatic sensor (7), a first bridging capacitor (12), a charging / discharging switching element (13), a control device (14), and a measurer (15), and is characterized in that: the electrostatic sensor (7) is configured such that the electrostatic capacitance changes in accordance with at least one of the contact area of conductors (51, 52) and the distance from the conductors; the time constant (tau) changes according to the distance from the first measurement position (29). The measurer (15) detects the position of contact of the conductor (51, 52) with the electrostatic sensor (7) on the basis of a first potential first sampling value (V11), which is a first potential acquired at a first sampling time point (ST1), in the charging step, and a first potential second sampling value (V12), which is a first potential acquired at a second sampling time point (ST2) after a predetermined time elapses from the first sampling time point (ST1).

Description

Technical Field

[0001] The invention relates to a contact detection device. Background Art

[0002] Conventionally, for example, Patent Document 1 proposes a contact detection device that detects contact by a human body based on a change in electrostatic capacitance.

[0003] The contact detection device of Patent Document 1 includes a sheet-shaped flexible sensor body. The sensor body includes a plurality of rows of first electrodes and a plurality of columns of second electrodes. Each of the plurality of first electrodes is formed in a strip shape and arranged parallel to each other (see Patent Document 1). Fig.11 ). Each of the plurality of columns of second electrodes is formed into a strip shape and is arranged parallel to each other. The plurality of rows of first electrodes and the plurality of columns of second electrodes are arranged to cross each other.

[0004] The first electrodes in multiple rows and the second electrodes in multiple columns are arranged in a matrix. Thus, when a conductor such as a human hand or finger touches the sensor body, the position and area touched by the conductor can be detected by the first electrodes in multiple rows and the second electrodes in multiple columns arranged in a matrix.

[0005] Patent document 2 proposes a pressure-sensitive device capable of detecting both a pressed position and a pressed force. The pressure-sensitive device includes a pressure-sensitive portion 2, which includes: a dielectric; a first electrode having a predetermined volume resistivity; and a second electrode. In addition, the pressure-sensitive device includes: a first measuring device 30a connected to a first left terminal 21a located at the left end of the first electrode and a second left terminal 22a located at the left end of the second electrode; and a second measuring device 30b connected to a first right terminal 21b located at the right end of the first electrode and a second right terminal 22b located at the right end of the second electrode.

[0006] The pressure-sensitive portion 2 forms an RC circuit based on the electrostatic capacitance C between the electrodes and the resistance R of the main first electrode. The pressure-sensitive portion is deformed by applying a pressing force from the outside, so that the electrostatic capacitance C changes. In addition, since the first electrode has a predetermined volume resistivity, the resistance between the pressing position and the first left terminal 21a changes according to the distance between the pressing position and the first left terminal 21a applied from the outside to the pressure-sensitive portion, and similarly, the resistance between the pressing position and the first right terminal 21b changes. The pressing force and the pressing position can be obtained using the RC delay time in the measured value of the first measuring device 30a and the RC delay time in the measured value of the second measuring device 30b.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-55589

[0010] Patent Document 2: Japanese Patent Application Publication No. 2019-196904 Summary of the invention

[0011] Problems to be solved by the invention

[0012] However, the technology described in Patent Document 1 has the following problems: since a plurality of rows of first electrodes and a plurality of columns of second electrodes are arranged in a matrix, it is necessary to increase wiring and terminals for connecting the wiring, which increases the number of components and complicates the structure.

[0013] According to the technology described in Patent Document 2, in order to obtain the pressing force and the pressing position, it is necessary to use the measured value of the first measuring device and the measured value of the second measuring device connected to the terminals at different positions. That is, in order to obtain the pressing force and the pressing position, two measuring devices are required. Therefore, there is a problem that the number of parts increases and the structure becomes complicated.

[0014] The present invention has been made in view of the above background, and provides a contact detection device capable of detecting at least one of a contact position and a contact area with a simple configuration.

[0015] Means used to solve problems

[0016] One embodiment of the present invention is a contact detection device comprising:

[0017] An electrostatic sensor comprising an applying electrode to which an input voltage as a constant voltage is applied from a power supply, a measuring electrode arranged to face the applying electrode and to measure a potential, and a dielectric arranged between the applying electrode and the measuring electrode, the electrostatic sensor being used to detect contact with a conductor;

[0018] a first bridging capacitor connected in series between the first measuring position of the measuring electrode and the ground potential;

[0019] a charge-discharge switch element connected in series between the measuring electrode and the ground potential and connected in parallel with the first bridge capacitor, and discharging the potential of the measuring electrode to the ground potential when in a closed state;

[0020] a control device, which sets the input voltage to the applying electrode in a state where the input voltage is not applied and sets the charging and discharging switching element in a closed state, thereby executing a step of discharging the potential of the measuring electrode to a ground potential; and after the discharging step, sets the charging and discharging switching element in an open state and sets the input voltage to the applying electrode, thereby executing a step of charging the electrostatic sensor; and

[0021] a measuring device that acquires a first potential between the first measuring position of the measuring electrode and the first bridging capacitor in the charging step,

[0022] The electrostatic sensor is configured such that the electrostatic capacitance changes according to at least one of the area in contact with the conductor and the distance from the conductor, and the time constant changes due to the resistance corresponding to the distance from the first measurement position.

[0023] The measuring device detects the position where the conductor contacts the electrostatic sensor based on the first potential, i.e., the first potential first sampling value, obtained at a first sampling time point after a predetermined time has passed from the start of charging of the electrostatic sensor in the charging step, and the first potential, i.e., the first potential second sampling value, obtained at a second sampling time point after a predetermined time has passed from the first sampling time point.

[0024] Effects of the Invention

[0025] According to one aspect of the present invention, at least one of the contact position and the contact area of ​​the conductor with the electrostatic sensor can be detected by using a simple configuration of one measuring device.

[0026] In addition, the reference numerals in parentheses in the claims indicate the corresponding relationship with the specific means described in the embodiments described later, and do not limit the technical scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a front view showing a steering wheel to which the contact detection device according to the first embodiment is applied.

[0028] Figure 2 yes Figure 1 Sectional view along line II-II.

[0029] Figure 3 is a partially enlarged cross-sectional view of the electrostatic sensor of Embodiment 1, Figure 4 Cross-sectional view along line III-III.

[0030] Figure 4 This is a partially cutaway plan view showing the electrostatic sensor according to the first embodiment.

[0031] Figure 5 This is a block diagram showing the structure of the contact detection device according to the first embodiment.

[0032] Figure 6 This is a time series diagram of the operation of the charging and discharging switching element, the first input switching element, and the input potential and output potential of the electrostatic sensor in the first embodiment.

[0033] Figure 7 This is a graph showing the temporal change in the output voltage of the electrostatic sensor in the step of charging the electrostatic sensor according to the first embodiment.

[0034] Figure 8 This is a schematic diagram showing changes in electrostatic capacitance caused by the approach and contact of a conductor such as a finger in the electrostatic sensor of the first embodiment.

[0035] Fig. 9 This is a schematic cross-sectional view showing a state in which a finger comes into contact with the electrostatic sensor according to the first embodiment.

[0036] Fig.10 This is a schematic cross-sectional view showing a state in which a hand comes into contact with the electrostatic sensor according to the first embodiment.

[0037] Fig.11 This is a graph showing the time-dependent changes in the first voltage when a hand touches, the first voltage when a finger touches, and the first voltage in a state where neither touches, in the electrostatic sensor of Embodiment 1.

[0038] Fig.12 This is a schematic cross-sectional view showing the current flowing into the applying electrode and the measuring electrode when a finger touches the electrostatic sensor of the first embodiment.

[0039] Fig.13 is Fig.12 A graph showing a change over time of a first potential in the electrostatic sensor shown.

[0040] Fig.14 Is to touch the finger with Fig.12 The electrostatic sensor shown is a schematic cross-sectional view showing the current flowing into the application electrode and the measurement electrode at different positions.

[0041] Fig.15 It means in Fig.14 A graph showing a temporal change in the first potential in the electrostatic sensor shown.

[0042] Fig.16 This is a flowchart showing the operation of the contact detection device according to the first embodiment.

[0043] Fig.17 This is a block diagram showing the structure of a contact detection device according to the second embodiment.

[0044] Fig.18 This is a schematic cross-sectional view showing the current flowing into the applying electrode and the measuring electrode when a finger touches the electrostatic sensor according to the second embodiment.

[0045] Fig.19 Is to touch the finger with Fig.18 The electrostatic sensor shown is a schematic cross-sectional view showing the current flowing into the application electrode and the measurement electrode at different positions.

[0046] Fig. 20 This is a block diagram showing the structure of a contact detection device according to the third embodiment.

[0047] Fig.21 This is a schematic cross-sectional view showing the current flowing into the applying electrode and the measuring electrode when a finger touches the electrostatic sensor according to the third embodiment.

[0048] Fig. 22 It means in Fig.21 FIG. 4 is a graph showing the temporal changes of the first potential and the second voltage in the electrostatic sensor shown.

[0049] Fig.23 Is to touch the finger with Fig.21 The electrostatic sensor shown is a schematic cross-sectional view showing the current flowing into the application electrode and the measurement electrode at different positions.

[0050] Fig.24 It means in Fig.23 FIG. 4 is a graph showing the temporal changes of the first potential and the second voltage in the electrostatic sensor shown.

[0051] Fig.25 This is a block diagram showing the structure of a contact detection device according to a fourth embodiment.

[0052] Fig.26 This is a schematic cross-sectional view of current flowing into the applying electrode and the measuring electrode when the first cycle is executed in the contact detection device of the fourth embodiment and a finger contacts the electrostatic sensor.

[0053] Fig. 27 This is a schematic cross-sectional view showing the current flowing into the applying electrode and the measuring electrode when the second cycle is executed in the contact detection device of the fourth embodiment and a finger contacts the electrostatic sensor.

[0054] Fig.28This is a flowchart showing the operation of the contact detection device according to the fourth embodiment.

[0055] Fig.29 This is a flowchart showing the first cycle of the fourth embodiment.

[0056] Fig.30 This is a flowchart showing the second cycle of the fourth embodiment.

[0057] Fig.31 This is a partially enlarged cross-sectional view showing the electrostatic sensor according to the fifth embodiment. DETAILED DESCRIPTION

[0058] (Implementation Method 1)

[0059] 1. Structure of steering wheel 1

[0060] Embodiment 1 in which the contact detection device 10 according to the present invention is applied to a steering wheel 1 of a vehicle (not shown) will be described. Figure 1-2 The structure of the steering wheel 1 is described. Figure 1 As shown, the steering wheel 1 includes a ring portion 2 formed in a circular ring shape, a core portion 3 formed smaller than the ring portion 2 and arranged radially inward of the ring portion 2, and a plurality of (three in this embodiment) connecting portions 4 connecting the core portion 3 and the ring portion 2. However, the number of the connecting portions 4 is not particularly limited, and may be one to two, or four or more.

[0061] like Figure 2 As shown, the ring portion 2 includes a core 5, a resin inner layer material 6, an electrostatic sensor 7, and a skin material 8. The core 5 constitutes the central portion of the ring portion 2 and is formed into a shape corresponding to the shape of the ring portion 2. That is, the core 5 is formed into a circular ring shape and has a circular cross-section at right angles to the axis. Here, the cross-sectional shape of the core 5 at right angles to the axis is not limited to a circle, and can be set to any shape such as an elliptical shape, an egg shape, a U shape, a C shape, a polygonal shape, etc. The core 5 of this embodiment is formed of metals such as aluminum and magnesium and has conductivity. The material of the core 5 can be applied to materials other than metals.

[0062] The resin inner layer material 6 covers the outer surface of the core 5 over the entire circumference of the annular shape of the core 5 and over the entire circumference of the circular cross-sectional shape of the core 5. In this embodiment, the cross section of the resin inner layer material 6 at right angles to the axis is formed into a circle. Assuming that the core 5 has a U-shaped cross section at right angles to the axis, the resin inner layer material 6 is filled in addition to the radial outer side of the cross section of the core 5 at right angles to the axis, and is also filled in the U-shaped recess of the core 5. The resin inner layer material 6 is molded into the outer surface side of the core 5 by injection molding and is directly bonded to the outer surface of the core 5. The cross-sectional shape of the resin inner layer material 6 at right angles to the axis is not limited to a circle, and can be set to any shape such as an egg shape, an elliptical shape, a polygonal shape, etc. The resin inner layer material 6 uses, for example, a foamed polyurethane resin. In addition, the resin inner layer material 6 can also use a non-foamed resin.

[0063] An electrostatic sensor 7 is disposed on the outer surface of the resin inner layer material 6. The electrostatic sensor 7 is configured so that when a conductor (not shown) such as a finger or a hand contacts or approaches the electrostatic sensor 7, the electrostatic capacitance equivalent value of the electrostatic sensor 7 changes. The electrostatic sensor 7 involved in this embodiment is a steering wheel sensor applied to the steering wheel 1 of a vehicle. The electrostatic sensor 7 will be described in detail later.

[0064] The skin material 8 covers the entire circumference of the electrostatic sensor 7 in the outer surface of the electrostatic sensor 7 (the surface on the side opposite to the resin inner layer material 6 in the electrostatic sensor 7). That is, as described later, when the measuring electrode 22 is exposed on the first surface 24 side of the dielectric 23, the skin material 8 also functions as a covering material for the measuring electrode 22. The skin material 8 is formed by injection molding, and is wound around the outer surface side of the electrostatic sensor 7 and bonded to the outer surface of the electrostatic sensor 7. The skin material 8 is formed, for example, of a polyurethane resin. The outer surface of the skin material 8 constitutes an appearance surface. Therefore, the skin material 8 preferably uses a non-foamed polyurethane resin or a slightly foamed polyurethane resin.

[0065] 2. Structure of electrostatic sensor

[0066] Next, refer to Figure 3 as well as Figure 4 The structure of the electrostatic sensor 7 is described. The electrostatic sensor 7 includes an application electrode 21, a measuring electrode 22, and a dielectric 23. The application electrode 21 applies an input voltage Vin as a constant voltage from a power supply 41 described later. The measuring electrode 22 is arranged to face the application electrode 21 and measures the potential. The dielectric 23 is arranged between the application electrode and the measuring electrode. The application electrode 21 and the measuring electrode 22 are conductive and are formed in a layered form.

[0067] The applying electrode 21 is disposed on the second surface 25 of the dielectric 23. The applying electrode 21 is formed in a shape similar to the dielectric 23 and slightly smaller than the dielectric 23. Thus, the edge of the second surface 25 of the dielectric 23 is exposed from the edge of the applying electrode 21.

[0068] The measuring electrode 22 is arranged on the first surface 24 of the dielectric 23. The measuring electrode 22 is formed in a similar shape that is slightly smaller than the dielectric 23. Thus, the edge of the first surface 24 of the dielectric 23 is exposed from the edge of the measuring electrode 22.

[0069] like Figure 3 as well as Figure 4 As shown, the measuring electrode 22 has a plurality of through holes 26 that penetrate in the thickness direction of the measuring electrode 22. The through holes 26 are arranged in parallel in the long side direction of the measuring electrode 22. In addition, the through holes 26 are arranged in parallel in the width direction orthogonal to the long side direction of the measuring electrode 22. The inner shape of the through hole 26 is formed into a circle. The plurality of through holes 26 are formed into the same shape and size. However, the through holes 26 may not be arranged in parallel in the long side direction, and may not be arranged in parallel in the width direction. In addition, the inner shape of the plurality of through holes 26 is not limited to a circle, and may be a polygonal shape such as a quadrilateral shape or an oblong shape, and any shape can be selected. In addition, the plurality of through holes 26 are not limited to the same shape and size, and may be appropriately formed into any shape or size.

[0070] like Figure 3 As shown, in this embodiment, the application electrode 21 is formed to be coplanar with the second surface 25 of the dielectric 23. In addition, the measurement electrode 22 is formed to be coplanar with the first surface 24 of the dielectric 23. In this embodiment, the dielectric 23 is filled inside the plurality of through holes 26. However, the application electrode 21 may protrude from the second surface 25 of the dielectric 23, and the measurement electrode 22 may protrude from the first surface 24 of the dielectric 23.

[0071] The dielectric 23 is formed to contain an elastomer as a main component, for example. Therefore, the dielectric 23 is soft. That is, the dielectric 23 has flexibility and is configured to be able to stretch in the plane direction. The dielectric 23 is formed to contain a thermoplastic material, particularly a thermoplastic elastomer, as a main component, for example. The dielectric 23 can be formed of the thermoplastic elastomer itself, or a cross-linked elastomer can be formed as a main component by heating the thermoplastic elastomer as a raw material.

[0072] In addition, the dielectric 23 may also include rubber, resin, and other materials other than the thermoplastic elastomer. For example, when the dielectric 23 includes rubber such as ethylene-propylene rubber (EPM, EPDM), the flexibility of the dielectric 23 is improved. From the viewpoint of improving the flexibility of the dielectric 23, the dielectric 23 may contain a flexibility-imparting component such as a plasticizer. Furthermore, the dielectric 23 may be configured to include a reaction-curable elastomer or a thermosetting elastomer as a main component.

[0073] Furthermore, the dielectric 23 is preferably made of a material having good thermal conductivity. Therefore, the dielectric 23 may be made of a thermoplastic elastomer having high thermal conductivity, or may contain a filler capable of improving thermal conductivity.

[0074] The applying electrode 21 is arranged on the second surface 25 side of the dielectric 23, and the measuring electrode 22 is arranged on the first surface 24 side of the dielectric 23. The applying electrode 21 and the measuring electrode 22 are conductive. Furthermore, the applying electrode 21 and the measuring electrode 22 are soft. That is, the applying electrode 21 and the measuring electrode 22 are flexible and are configured to be able to extend in the surface direction.

[0075] The application electrode 21 and the measuring electrode 22 may be formed of a conductive elastomer. When the application electrode 21 and the measuring electrode 22 are formed of a conductive elastomer, the application electrode 21 and the measuring electrode 22 are formed using the elastomer as a main material and containing a conductive filler. The main material of the application electrode 21 and the measuring electrode 22, i.e., the elastomer, may have a main component that is the same as that of the dielectric 23, or may use a different material. The application electrode 21 and the measuring electrode 22, and the dielectric 23 are joined by mutual welding (thermal welding).

[0076] The application electrode 21 and the measurement electrode 22 may be formed of a conductive cloth. The conductive cloth is a fabric or nonwoven fabric formed of conductive fibers. Here, the conductive fibers are formed by covering the surface of the flexible fibers with a conductive material. The conductive fibers are formed, for example, by electroplating copper, nickel, etc. on the surface of resin fibers such as polyethylene. In this case, the application electrode 21 and the measurement electrode 22 are joined to the dielectric 23 by welding (thermal welding) of the dielectric 23 itself.

[0077] The application electrode 21 and the measurement electrode 22 can be formed of metal foil. The metal foil can be a metal material that can conduct electricity, for example, copper foil, aluminum foil, etc. Further, as in the case of the conductive cloth, the application electrode 21 and the measurement electrode 22 are bonded to the sensor sheet by the fusion (thermal fusion) of the dielectric 23 itself.

[0078] The applying electrode 21 may have a through hole that penetrates the applying electrode 21 in the thickness direction, or may not have the through hole. In the case where the applying electrode 21 does not have a through hole, the measuring electrode 22 has a plurality of through holes 26, thereby enabling the resistance value of the measuring electrode 22 to be greater than the resistance value of the applying electrode 21. Specifically, the structure is formed as follows: in the long side direction, the resistance value per unit length of the measuring electrode 22 is formed to be greater than the resistance value per unit length of the applying electrode 21.

[0079] On the other hand, when applying electrode 21 has a through hole, the diameter of through hole 26 of measuring electrode 22 is formed larger than that of the through hole of applying electrode 21 , thereby making the resistance value of measuring electrode 22 larger than that of applying electrode 21 .

[0080] 3. Overall structure of the contact detection device 10

[0081] like Figure 5 As shown, the contact detection device 10 includes the electrostatic sensor 7 , a first input switching element 11 , a first bridge capacitor 12 , a charge and discharge switching element 13 , a control device 14 , and a measuring device 15 .

[0082] The first input switch element 11 is disposed between the power source 41 and the application electrode 21, and opens or closes the input voltage Vin applied from the power source 41 to the application electrode 21. The power source 41 involved in this embodiment is a power line connected to a DC power source not shown. The electrostatic sensor 7 is formed in a shape elongated in the longitudinal direction (see Figure 3 as well as Figure 4 The electrostatic sensor 7 has a first end portion 27 and a second end portion 28 at both ends in the longitudinal direction. The first end portion 27 in the longitudinal direction of the applying electrode 21 is connected to a power source 41 .

[0083] The first bridging capacitor 12 is connected in series between a first end 27 in the longitudinal direction of the measuring electrode 22 and the ground potential 42. The first end 27 in the longitudinal direction of the measuring electrode 22 is an example of a first measurement position 29 of the measuring electrode 22.

[0084] The charge / discharge switch element 13 is connected in series between the first measurement position 29 of the measurement electrode 22 and the ground potential 42, and is connected in parallel with the first bridge capacitor 12. The charge / discharge switch element 13 discharges the potential of the measurement electrode 22 to the ground potential 42 when closed.

[0085] The control device 14 is a microcomputer including a CPU (central processing unit, not shown), a RAM (random access memory, not shown), a ROM (read only memory, not shown), etc. The control device 14 controls the first input switch element 11 to be in an open state or a closed state. In addition, the control device 14 controls the charge and discharge switch element 13 to be in an open state or a closed state.

[0086] The control device 14 sets the first input switch element 11 to an open state and sets the charge and discharge switch element 13 to a closed state. Thus, the control device 14 performs a step of discharging the potential of the measurement electrode 22 to the ground potential 42. After the step of discharging the potential of the measurement electrode 22 to the ground potential 42, the control device 14 sets the charge and discharge switch element 13 to an open state and sets the first input switch element 11 to a closed state. Thus, the control device 14 performs a step of charging the electrostatic sensor 7.

[0087] In the step of charging the electrostatic sensor 7 , the measuring device 15 acquires the first potential V1 between the first measurement position 29 of the measuring electrode 22 and the first bridging capacitor 12 .

[0088] The storage device 16 stores the saturated first potential SV1. The saturated first potential SV1 is the first potential V1 when the potential of the measuring electrode 22 is saturated in a state where the conductor contacts the entire surface of the measuring electrode 22 of the electrostatic sensor 7 in the step of charging the electrostatic sensor 7.

[0089] 4. Electrostatic sensor 7

[0090] (1) Method for measuring electrostatic capacitance of electrostatic sensor 7

[0091] Next, refer to Figure 6 , the relationship between the timing of opening and closing of the charge and discharge switch element 13 executed by the control device 14 and the potential Vin and output voltage Vout of one end side of the electrostatic sensor 7 is described. During t1 to t2, the charge and discharge switch element 13 is set to ON (closed state). In addition, the first input switch element 11 is connected to the ground potential 42 side. Therefore, the potential Vin of one end side of the electrostatic sensor 7 becomes the ground potential 42.

[0092] Through the above operation, the charge of the electrostatic sensor 7 is discharged through the charge and discharge switch element 13. As a result, the potential (output voltage) Vout between the electrostatic sensor 7 and the first bridge capacitor 12 becomes the ground potential 42 as a reference state. That is, before the above operation, the output voltage Vout is not constant, but through the above operation, the output voltage Vout is set to the ground potential 42.

[0093] Next, during t2 to t4, the charge and discharge switch element 13 is turned OFF (disconnected state), and the first input switch element 11 is connected to the power supply 41. Therefore, the potential Vin at one end of the electrostatic sensor 7 becomes the input voltage Vin. Through the above operation, the electrostatic sensor 7 is charged. After the charging starts, at the time (ST1, ST2) after the predetermined time has passed, the measuring device 15 measures the output voltage Vout.

[0094] Next, from t4 to t5, the charge and discharge switch element 13 is turned on (closed), and the first input switch element 11 is connected to the ground potential 42. By this operation, the potential Vin of one end of the electrostatic sensor 7 becomes the ground potential 42, and the charge of the electrostatic sensor 7 is discharged. That is, the output voltage Vout becomes the ground potential 42. Next, from t5 to t9, the same operation as from t1 to t5 is repeated.

[0095] As described above, the first bridge capacitor 12 is connected in series with the electrostatic sensor 7, and the measuring device 15 obtains the electrostatic capacitance equivalent value based on the potential on the other end side of the electrostatic sensor 7, that is, the potential (output voltage) Vout between the electrostatic sensor 7 and the first bridge capacitor 12. Here, since only the intermediate potential of the two capacitors is not constant, the electrostatic capacitance measured using the intermediate potential is not highly accurate.

[0096] However, as described above, by setting the charge and discharge switch element 13 to a closed state, the charge of the electrostatic sensor 7 is discharged. That is, the output voltage (intermediate potential) Vout becomes the ground potential 42 as a reference state. That is, by setting the charge and discharge switch element 13 to a closed state, the output voltage Vout can be calibrated.

[0097] Furthermore, after the measuring device 15 is discharged, the charging and discharging switching element 13 is turned off, and when the input voltage Vin is applied to one end of the electrostatic sensor 7, the measuring device 15 measures the potential of the other end of the electrostatic sensor 7. That is, the potential measured by the measuring device 15 becomes a potential corresponding to the electrostatic sensor 7. Therefore, the contact detection device 10 can measure the electrostatic sensor 7 with high accuracy.

[0098] (2) Time constant τ of electrostatic sensor 7

[0099] Figure 7 The change with time of the output voltage Vout of the electrostatic sensor 7 during the above-mentioned period t2 to t3 is shown. When the output voltage Vout rises as the electrostatic sensor 7 is charged and sufficient time has passed, it converges to a saturation voltage.

[0100] Figure 7 The percentage of the output voltage Vout of the electrostatic sensor 7 to the saturation voltage when τ, 2τ (twice τ), 3τ (three times τ), 4τ (four times τ), and 5τ (five times τ) have passed since the start of charging the electrostatic sensor 7 is described, with respect to the time constant τ when the electrostatic sensor 7 is defined as an RC equivalent circuit. The percentage of the output voltage Vout of the electrostatic sensor 7 to the saturation voltage after τ from the start of charging the electrostatic sensor 7 is 63.2%, the percentage of the output voltage Vout of the electrostatic sensor 7 to the saturation voltage after 2τ is 86.5%, the percentage of the output voltage Vout of the electrostatic sensor 7 to the saturation voltage after 3τ is 95.0%, the percentage of the output voltage Vout of the electrostatic sensor 7 to the saturation voltage after 4τ is 98.2%, and the percentage of the output voltage Vout of the electrostatic sensor 7 to the saturation voltage after 5τ is 99.3%.

[0101] When measuring the output voltage Vout of the electrostatic sensor 7, if the measurement is performed from waiting until the output voltage Vout converges to the saturation voltage, the efficiency is reduced because the measurement takes time. Therefore, the time point for measuring the output voltage Vout of the electrostatic sensor 7 is set to be more than 5 times the time constant τ. As a result, the efficiency of measuring the output voltage Vout of the electrostatic sensor 7 can be improved.

[0102] (3) Change in electrostatic capacitance of electrostatic sensor 7 caused by contact or non-contact of conductors

[0103] Next, refer to Figure 8 , how the electrostatic capacitance of the electrostatic sensor 7 changes when a conductor such as a finger 51 contacts the electrostatic sensor 7 of this method or when the conductor such as the finger 51 does not contact the electrostatic sensor 7 of this method is described. In addition, for the sake of convenience of description, the size of the finger 51 is exaggerated. However, the state in which the conductor contacts the electrostatic sensor 7 includes the state in which the conductor contacts the electrostatic sensor 7 directly, and includes the state in which the conductor contacts the electrostatic sensor 7 indirectly via the surface material 8.

[0104] Figure 8 The upper layer shows the state of the electrostatic sensor 7 and the finger 51 as a conductor. Figure 8 In the middle layer, the state of the electric field lines 30 of the electrostatic sensor 7 in each state is recorded using an enlarged cross-sectional view of a part of the electrostatic sensor 7. Figure 8 The lower layer records the electrostatic capacitance of the electrostatic sensor 7 in each state.

[0105] exist Figure 8The upper layer on the left end of is recorded as a non-contact state. That is, it is recorded that the finger 51, an example of a conductor, is not in contact with the electrostatic sensor 7. Figure 8 The middle layer at the left end of describes the state of the electric field lines 30 in a state where the finger 51 is not in contact with the electrostatic sensor 7. In the area where the applying electrode 21 and the measuring electrode 22 are opposed to each other, the electric field lines 30 are described from the applying electrode 21 to the measuring electrode 22. The electric field lines 30 leak from the through-hole 26 of the measuring electrode 22 to the area on the opposite side of the applying electrode 21 with respect to the measuring electrode 22. Among the electric field lines 30 leaking from the through-hole 26, the electric field lines 30 located near the hole edge of the through-hole 26 flow toward the measuring electrode 22 from the area on the opposite side of the applying electrode 21 around the hole edge of the through-hole 26 of the measuring electrode 22.

[0106] exist Figure 8 The lower layer on the left end of describes the electrostatic capacitance of the electrostatic sensor 7 in the non-contact state. In the non-contact state, the electric field lines 30 leak out from the through-hole 26 of the measuring electrode 22, so the electrostatic capacitance of the electrostatic sensor 7 becomes smaller than when the measuring electrode 22 does not have the through-hole 26. On the other hand, the electric field lines 30 located near the edge of the through-hole 26 leak out from the through-hole 26 to the outside and then return to the measuring electrode 22. Therefore, the electrostatic capacitance of the electrostatic sensor 7 becomes slightly larger than when the electric field lines 30 leaking from the through-hole 26 do not return to the measuring electrode 22.

[0107] exist Figure 8 The middle of the upper layer of is recorded as a close state. That is, it indicates that the finger 51 and the electrostatic sensor 7 are in a non-contact state, and the finger 51 is close to the electrostatic sensor 7. Figure 8 The state of the electric field lines 30 in the proximity state is recorded in the center of the middle layer. The finger 51 is located on the measuring electrode 22 side relative to the electrostatic sensor 7. The electric field lines 30 leaking from the through hole 26 of the measuring electrode 22 are pulled toward the finger 51. As a result, a portion of the electric field lines 30 located near the edge of the through hole 26 is also pulled toward the finger 51. In this way, after leaking out from the through hole 26 to the outside, the electric field lines 30 returning to the measuring electrode 22 are reduced. As a result, Figure 8 As shown in the center of the lower layer, the electrostatic capacitance of the electrostatic sensor 7 in the proximity state is reduced compared to the electrostatic capacitance of the electrostatic sensor 7 in the non-contact state.

[0108] exist Figure 8 The upper layer on the right end of is recorded as a contact state. That is, it indicates that the finger 51 and the electrostatic sensor 7 are in contact. Figure 8The state of the electric field lines 30 in the contact state is recorded in the center of the right end of . The finger 51 contacts the surface of the epidermis material of the electrostatic sensor 7. In other words, the finger 51 contacts the measuring electrode 22 side in the electrostatic sensor 7. The finger 51 is located above the through hole 26 of the measuring electrode 22. In other words, the finger 51 indirectly blocks the through hole 26 of the measuring electrode 22 via the epidermis material. All the electric field lines 30 leaking from the through hole 26 are pulled toward the finger 51. As a result, there are no electric field lines 30 that leak out from the through hole 26 and then wind back to the measuring electrode 22.

[0109] On the other hand, the electric field lines 30 extend from the edge of the through hole 26 of the measuring electrode 22 toward the finger 51 contacting the surface of the skin material 8. Figure 8 As shown in the lower layer at the right end of , the finger 51 as a conductor simulates a part of the measuring electrode 22. Therefore, the electric field line 30 from the applying electrode 21 to the measuring electrode 22 is configured not to leak from the through hole 26, and thus the electrostatic capacitance of the electrostatic sensor 7 increases. As a result, the electrostatic capacitance of the electrostatic sensor 7 in the contact state becomes larger than the electrostatic capacitance of the electrostatic sensor 7 in the non-contact state and the proximity state in which the electric field line 30 leaks from the through hole 26.

[0110] In the electrostatic sensor 7 of this embodiment, the more through holes 26 are indirectly blocked by the conductor such as the finger 51, the greater the electrostatic capacitance of the electrostatic sensor 7. In addition, the electrostatic sensor 7 of this embodiment is configured so that the electrostatic capacitance per unit area corresponding to the position where the conductor such as the finger 51 contacts and the electrostatic capacitance per unit area corresponding to the position where the conductor such as the finger 51 does not contact become different values.

[0111] Next, refer to Figures 9 to 11 , the relationship between the contact area of ​​the conductor with the electrostatic sensor 7 and the electrostatic capacitance of the electrostatic sensor 7 will be described. In addition, for the convenience of description, the size of the finger 51 or the hand 52 is exaggerated.

[0112] Fig. 9 The electrostatic sensor 7 is shown in a state where the plurality of through holes 26 are indirectly blocked by the finger 51. Fig. 9 In the figure, five electric field lines 30 leaking from the five through holes 26 are pulled close to the finger 51. However, the number of electric field lines 30 pulled close to the finger 51 is not limited. Although not shown in detail, among the electric field lines 30 leaking from the other through holes 26, the electric field lines 30 located near the center of each through hole 26 leak to the outside of the electrostatic sensor 7, and the electric field lines 30 near the edge of each through hole 26 return to the measuring electrode 22.

[0113] Fig.10The electrostatic sensor 7 is shown in a state where the plurality of through holes 26 are indirectly blocked by the entire hand 52. Fig.10 In the embodiment, twenty electric field lines 30 are drawn to the entire hand 52. However, the number of electric field lines 30 drawn to the entire hand 52 is not limited to 20. The electric field lines 30 leaking from the other through holes 26 are the same as those of the finger 51.

[0114] Fig.11 The output voltage VHout when the hand 52 contacts the electrostatic sensor 7, the output voltage VFout when the finger 51 contacts the electrostatic sensor 7, and the output voltage VNout when the conductor such as the finger 51 or the hand 52 does not contact the electrostatic sensor 7 are indicated. Fig.11 , the output voltages VHout, VFout, and VNout of the electrostatic sensor 7 are compared with the output voltages VHout, VFout, and VNout at the saturation time Ts when the electrostatic capacitance of the electrostatic sensor 7 is saturated. When the conductor such as the finger 51 or the hand 52 does not contact the electrostatic sensor 7, the electric field lines 30 leak to the outside from the plurality of through holes 26, so that the electrostatic capacitance of the electrostatic sensor 7 becomes the lowest, and the output voltage VNout of the electrostatic sensor 7 is the lowest.

[0115] When the finger 51 contacts the electrostatic sensor 7 , the electric field lines 30 of the portion of the through holes 26 indirectly covered by the finger 51 are drawn toward the finger 51 , thereby increasing the electrostatic capacitance of the electrostatic sensor 7 and raising the output voltage VFout of the electrostatic sensor 7 .

[0116] When the entire hand 52 contacts the electrostatic sensor 7 , more through holes 26 can be indirectly covered than the finger 51 , so that the electrostatic capacitance of the electrostatic sensor 7 further increases, and the output voltage VHout of the electrostatic sensor 7 further increases.

[0117] The saturated first potential SV1 is, for example, a first potential V1 when the potential of the measuring electrode 22 is saturated in a state where the conductor contacts the entire surface of the measuring electrode 22 of the electrostatic sensor 7. Fig.11 Although not shown in detail, the saturated first potential SV1 is further larger than the output voltage Vout when the hand 52 contacts the electrostatic sensor 7 .

[0118] The measuring device 15 can detect the area where the conductor such as the finger 51 is in contact with the electrostatic sensor 7 based on the ratio of the first potential V1 to the saturated first potential SV1 when the conductor is in contact with the electrostatic sensor 7 .

[0119] (4) Method for detecting the contact position of the conductor

[0120] Next, refer to Figure 12 to Figure 15, a method for detecting a position where a conductor illustrated by the finger 51 contacts the electrostatic sensor 7 will be described. Fig.12 The state in which the finger 51 contacts the electrostatic sensor 7 at a position close to the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged by the above method, the current for charging the electrostatic sensor 7 flows in the applying electrode 21 as shown by the arrow A, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as shown by the arrow B.

[0121] As described above, the following structure is formed: the resistance value per unit length in the long side direction of the measuring electrode 22 is formed to be larger than the resistance value per unit length in the long side direction of the applying electrode 21. Therefore, if the distance between the first measuring position 29 of the measuring electrode 22 and the position where the finger 51 contacts the electrostatic sensor 7 changes, the resistance value R1 between the first measuring position 29 in the measuring electrode 22 and the position corresponding to the finger 51 changes to be larger than that of the applying electrode 21. Therefore, the following structure is formed: the time constant τ of the electrostatic sensor 7 changes according to the distance between the first measuring position 29 of the measuring electrode 22 and the position where the finger 51 contacts the electrostatic sensor 7.

[0122] Fig.13 The change over time of the output voltage Vout of the electrostatic sensor 7 in the step of charging the electrostatic sensor 7 is shown in a state where the finger 51 is in contact with a position close to the first measurement position 29 in the electrostatic sensor 7. The output voltage Vout of the electrostatic sensor 7 increases with time and is saturated. The output potential at the first sampling time point ST1 after a predetermined time has passed since the start of charging the electrostatic sensor 7 is set to the first potential first sampling value V11. In addition, the output potential at the second sampling time point ST2 after a predetermined time has passed since the first sampling time point ST1 is set to the first potential second sampling value V12.

[0123] The second sampling time point ST2 is a time point at which the potential of the measuring electrode 22 is saturated. The time point at which the potential of the measuring electrode 22 is saturated refers to a state in which the change in the potential of the measuring electrode 22 becomes smaller than a predetermined value since the start of charging of the electrostatic sensor 7. In this embodiment, the second sampling time point ST2 is a time point that is 5 times or more of the time constant τ.

[0124] The first sampling time point ST1 is a time point in a transition state before the electrostatic sensor 7 becomes saturated. In this embodiment, the first sampling time point ST1 is a time point of 1 to 4 times the time constant τ.

[0125] In this embodiment, the position where the conductor such as the finger 51 contacts the electrostatic sensor 7 is detected based on the ratio of the first potential first sampling value V11 to the first potential second sampling value V12. This is described in detail below. As described above, the electrostatic sensor 7 of this embodiment has the following structure: by measuring the distance between the first measurement position 29 of the electrode 22 and the position where the finger 51 contacts the electrostatic sensor 7, the time constant τ of the electrostatic sensor 7 changes. Therefore, by measuring the distance between the first measurement position 29 of the electrode 22 and the position where the finger 51 contacts the electrostatic sensor 7, the first potential first sampling value V11 at the first sampling time point ST1 is different. Therefore, by calculating the ratio (V11 / V12) of the first potential first sampling value V11 to the first potential second sampling value V12, it is possible to detect how far away from the first measurement point in the electrostatic sensor 7 the conductor such as the finger 51 contacts.

[0126] Fig.14 The state in which the finger 51 contacts the electrostatic sensor 7 at a position away from the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged by the above method, the current for charging the electrostatic sensor 7 flows in the applying electrode 21 as shown by the arrow C, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as shown by the arrow D.

[0127] If you compare Fig.12 and Fig.14 , then in Fig.14 In the embodiment, the distance between the first measuring point in the electrostatic sensor 7 and the portion contacted by the finger 51 becomes greater than Fig.12 Therefore, the portion of the finger 51 that contacts the first measurement position 29 is Fig.14 The resistance value R2 of the measurement electrode 22 described above becomes larger than the resistance value R2 of the portion where the finger 51 contacts the first measurement position 29. Fig.12 The resistance value R1 of the measurement electrode 22 is recorded (R2>R1). Fig.13 The time constant τ of the electrostatic sensor 7 is described as follows: Fig.15 The time constant τ of the electrostatic sensor 7 described above changes.

[0128] Fig.15The change over time of the output voltage Vout of the electrostatic sensor 7 in the step of charging the electrostatic sensor 7 is shown in a state where the finger 51 is in contact with a position away from the first measurement position 29 in the electrostatic sensor 7. The output voltage Vout of the electrostatic sensor 7 increases with time and is saturated. The output potential at the first sampling time point ST1 after a predetermined time has passed since the start of charging the electrostatic sensor 7 is set to the first potential first sampling value V11. In addition, the output potential at the second sampling time point ST2 after a predetermined time has passed since the first sampling time point ST1 is set to the first potential second sampling value V12.

[0129] In the case where the finger 51 contacts the electrostatic sensor 7 at a position away from the first measurement position 29 ( Fig.14 ) compared to the case where the finger 51 contacts the electrostatic sensor 7 at a position close to the first measurement position 29 ( Fig.12 ), the resistance value R2 of the measuring electrode 22 from the first measuring position 29 to the finger 51 increases, the time constant τ changes, and thus the first potential first sampling value V11 decreases. In this way, according to this method, in the electrostatic sensor 7, the first potential first sampling value V11 can be made different by the distance from the first measuring position 29 to which the finger 51 contacts. As a result, by calculating the ratio (V11 / V12) of the first potential first sampling value V11 to the first potential second sampling value V12, it is possible to detect whether the conductor such as the finger 51 has contacted and at what distance from the first measuring point in the electrostatic sensor 7.

[0130] 5. Action of the contact detection device

[0131] Fig.16 The flowchart involved in the operation of the contact detection device of this embodiment is shown. When the contact detection device is started, the step (S1) of discharging the potential of the measuring electrode 22 to the ground potential 42 is performed. In S1, the control device 14 sets the first input switch element 11 to the open state and sets the charge and discharge switch element 13 to the closed state. Thus, when the input voltage Vin is not applied to the application electrode 21, the potential of the measuring electrode 22 is discharged to the ground potential 42.

[0132] After a predetermined time has passed and the potential of the measuring electrode 22 is discharged 42 to the ground potential, a step (S2) of charging the electrostatic sensor 7 is performed. In S2, the control device 14 sets the charge and discharge switch element 13 to an open state and sets the first input switch element 11 to a closed state. Thus, the electrostatic sensor 7 is charged.

[0133] The step of charging the electrostatic sensor 7 (S2) is executed. During the period until the electrostatic sensor 7 is fully charged, the measuring device 15 measures a first potential sampling value (S3) at a first sampling time point ST1 after a predetermined time has passed since the start of charging of the electrostatic sensor 7, and measures a second sampling value (S4) of the first potential at a second sampling time point ST2 after a predetermined time has passed since the first sampling time point ST1.

[0134] The measuring device 15 detects the position where the conductor contacts the electrostatic sensor 7 based on the ratio of the first potential first sampling value V11 to the first potential second sampling value V12 ( S5 ).

[0135] The measuring device 15 detects the area where the conductor contacts the electrostatic sensor 7 based on the first potential second sampling value V12 ( S6 ).

[0136] Through the above, the operation of the contact detection device 10 is completed.

[0137] 6. Effects of this method

[0138] The contact detection device 10 of this embodiment includes an electrostatic sensor 7 , a first bridge capacitor 12 , a charge and discharge switch element 13 , a control device 14 , and a measuring device 15 .

[0139] The electrostatic sensor 7 includes an applying electrode 21 to which an input voltage Vin as a constant voltage is applied from a power supply 41, a measuring electrode 22 arranged to be opposite to the applying electrode 21 and to measure the potential, and a dielectric 23 arranged between the applying electrode 21 and the measuring electrode 22. The electrostatic sensor 7 detects when a conductor comes into contact.

[0140] The first bridge capacitor 12 is connected in series between the first measurement position 29 of the measurement electrode 22 and the ground potential 42. The charge-discharge switch element 13 is connected in series between the measurement electrode 22 and the ground potential 42, and is connected in parallel with the first bridge capacitor 12, and discharges the potential of the measurement electrode 22 to the ground potential 42 when in a closed state.

[0141] The control device 14 performs a step of discharging the potential of the measuring electrode 22 to the ground potential 42 by setting the state where the input voltage Vin is not applied to the applying electrode 21 and setting the charging and discharging switching element 13 to a closed state. After the discharging step, the control device 14 performs a step of charging the electrostatic sensor 7 by setting the charging and discharging switching element 13 to an open state and setting the state where the input voltage Vin is applied to the applying electrode 21.

[0142] The measuring device 15 acquires the first potential V1 between the first measurement position 29 of the measuring electrode 22 and the first bridging capacitor 12 in the step of charging the electrostatic sensor 7 .

[0143] The electrostatic sensor 7 is configured such that the electrostatic capacitance changes according to at least one of the area in contact with the conductor and the distance from the conductor, and the time constant changes due to the resistance corresponding to the distance from the first measurement position 29 .

[0144] The measuring device 15 detects the position where the conductor contacts the electrostatic sensor 7 based on the first potential first sampling value V11 and the first potential second sampling value V12. The first potential first sampling value V11 is the first potential V1 acquired at the first sampling time point ST1 after a predetermined time has passed from the start of charging the electrostatic sensor 7 in the step of charging the electrostatic sensor 7. The first potential second sampling value V12 is the first potential V1 acquired at the second sampling time point ST2 after a predetermined time has passed from the first sampling time point ST1.

[0145] According to this embodiment, the position where the conductor contacts the electrostatic sensor 7 can be detected by a simple structure of a single measuring device 15 .

[0146] In addition, according to the present embodiment, the first sampling time point ST1 is a time point in a transition state from a predetermined first time after the start of charging of the electrostatic sensor 7 until the change in the potential of the measuring electrode 22 becomes a saturated state. In addition, the second sampling time point ST2 is a time point after the first sampling time point ST1 and after a predetermined second time after the start of charging of the electrostatic sensor 7. Based on the first potential first sampling value V11 acquired at the transition state, i.e., the first sampling time point ST1, and the first potential second sampling value V12 acquired at the second sampling time point ST2 later than the first sampling time point ST1, the position touched by the conductive electrostatic sensor 7 can be detected with high accuracy.

[0147] According to this embodiment, the measuring device 15 detects the position where the conductor contacts the electrostatic sensor 7 based on the ratio of the first potential first sampling value V11 to the first potential second sampling value V12 .

[0148] According to this embodiment, the electrostatic sensor 7 is formed into a shape elongated in the long-side direction, and has a first end 27 and a second end 28 at both ends in the long-side direction. The first bridge capacitor 12 is connected between the first measurement position 29 of the measuring electrode 22, that is, the first end 27 in the long-side direction and the ground potential 42. The first end 27 in the long-side direction of the applying electrode 21 is connected to the power supply 41. The first bridge capacitor 12 and the power supply 41 are connected to the first end 27 of the electrostatic sensor 7, so a lead wire (not shown) connected to the first bridge capacitor 12 and the power supply 41 is led out from the first end 27 of the electrostatic sensor 7. As a result, when the electrostatic sensor 7 is mounted on the steering wheel 1, the lead wire can be easily wired.

[0149] According to this embodiment, the measuring electrode 22 and the applying electrode 21 are formed of a conductive elastic body. Thus, the electrostatic sensor 7 has flexibility, and thus can be easily mounted along the shape of the steering wheel 1 .

[0150] The measuring electrode 22 of this embodiment has a plurality of through holes 26. Thus, the electric field lines 30 can be leaked from the through holes 26 to the outside of the electrostatic sensor 7. As a result, the conductor contacts the electrostatic sensor 7 at a position blocking the through holes 26, thereby suppressing the leakage of the electric field lines 30 from the through holes 26. Thus, when the conductor contacts the electrostatic sensor 7, the electrostatic capacitance of the electrostatic sensor 7 can be increased, so that the contact of the conductor with the electrostatic sensor 7 can be easily detected.

[0151] The electrostatic sensor 7 of this embodiment includes the electrostatic sensor 7 , a first bridge capacitor 12 , a charge and discharge switching element 13 , a control device 14 , and a measuring device 15 .

[0152] The electrostatic sensor 7 includes an applying electrode 21 to which an input voltage Vin as a constant voltage is applied from a power supply 41, a measuring electrode 22 arranged to be opposite to the applying electrode 21 and to measure the potential, and a dielectric arranged between the applying electrode 21 and the measuring electrode 22. The electrostatic sensor 7 detects the situation in which the conductor contacts the measuring electrode 22 side.

[0153] The first bridge capacitor 12 is connected in series between the first measurement position 29 of the measurement electrode 22 and the ground potential 42. The charge-discharge switch element 13 is connected in series between the measurement electrode 22 and the ground potential 42 and is connected in parallel with the first bridge capacitor 12, and discharges the potential of the measurement electrode 22 to the ground potential 42 when in a closed state.

[0154] The control device 14 does not apply the input voltage Vin to the applying electrode 21 and sets the charge and discharge switching element 13 to a closed state, thereby executing a step of discharging the potential of the measuring electrode 22 to the ground potential 42. After the discharge step, the control device 14 sets the charge and discharge switching element 13 to an open state and sets the input voltage Vin to the applying electrode 21, and executes a step of charging the electrostatic sensor 7.

[0155] In the step of charging the electrostatic sensor 7 , the measuring device 15 acquires the first potential V1 between the first measurement position 29 of the measuring electrode 22 and the first bridging capacitor 12 .

[0156] The electrostatic sensor 7 is configured such that the electrostatic capacitance changes according to at least one of the area and the distance from the conductor, and the time constant changes due to the resistance according to the distance from the first measurement position 29 .

[0157] The measuring device 15 detects the area of ​​the conductor in contact with the electrostatic sensor 7 based on the first potential second sampling value V12. The first potential second sampling value V12 is the first potential V1 acquired at the second time point after a predetermined first time has passed since the start of charging the electrostatic sensor 7, and after a first time point in a transition state until the change in the potential of the measuring electrode 22 becomes a saturated state, and after a predetermined second time has passed since the start of charging the electrostatic sensor 7 in the step of charging the electrostatic sensor 7.

[0158] According to this embodiment, the area where the conductor contacts the electrostatic sensor 7 can be detected by a simple structure of one measuring device 15 .

[0159] (Implementation Method 2)

[0160] Next, refer to Fig.17 , the contact detection device 60 of the second embodiment is described. Fig.17 As shown, in the contact detection device 60 of this embodiment, the second end portion 28 in the longitudinal direction of the applying electrode 21 is connected to the power supply 41. The configuration other than the above is substantially the same as that of the first embodiment, and therefore the same reference numerals are used for the same components, and repeated descriptions are omitted.

[0161] Fig.18The state in which the finger 51 contacts the electrostatic sensor 7 at a position close to the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged by the above method, the current for charging the electrostatic sensor 7 flows in the applying electrode 21 as shown by the arrow E, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as shown by the arrow F.

[0162] The output potential of the measuring electrode 22 when the finger 51 is in contact with the electrostatic sensor 7 at a position close to the first measuring position 29 is similar to that of the first embodiment. Fig.13 The diagrams shown are the same, so duplicate descriptions are omitted.

[0163] Fig.19 The state in which the finger 51 contacts the electrostatic sensor 7 at a position away from the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged by the above method, the current for charging the electrostatic sensor 7 flows in the applying electrode 21 as indicated by the arrow G, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as indicated by the arrow H.

[0164] The output potential of the measuring electrode 22 when the finger 51 contacts the electrostatic sensor 7 at a position away from the first measuring position 29 is similar to that of the first embodiment. Fig.15 The diagrams shown are the same, so duplicate descriptions are omitted.

[0165] According to this embodiment, the electrostatic sensor 7 is formed into a shape elongated in the longitudinal direction, and has a first end 27 and a second end 28 at both ends in the longitudinal direction. The first bridge capacitor 12 is connected between the first measurement position 29 of the measuring electrode 22, that is, the first end 27 in the longitudinal direction, and the ground potential 42. The second end 28 in the longitudinal direction of the applying electrode 21 is connected to the power supply 41.

[0166] According to this aspect, the power source 41 and the first bridge capacitor 12 can be connected to different ends of the electrostatic sensor 7. Therefore, even when it is difficult to lead out lead wires from the same end of the electrostatic sensor 7, the present invention can be applied.

[0167] (Implementation method 3)

[0168] Next, refer to Fig. 20 , the contact detection device 70 of the third embodiment is described. Fig. 20As shown, in the contact detection device 70 of the present embodiment, the second end 28 of the electrostatic sensor 7 is connected in series with the second bridge capacitor 17 between the ground potential 42. The measuring device 15 is configured to obtain the second potential Vout2 between the second end 28 of the measuring electrode 22 and the second bridge capacitor 17 in the step of charging the electrostatic sensor 7. In the present embodiment, the second end 28 of the measuring electrode 22 is set to the second measurement position 31. The measuring electrode 22 is configured so that the resistance changes according to the distance from the second measurement position 31.

[0169] In the step of charging the electrostatic sensor 7, the measuring device 15 detects the position where the conductor contacts the electrostatic sensor 7 based on the first potential first sampling value V11, the second potential first sampling value V21, the first potential second sampling value V12, and the second potential second sampling value V22. The second potential first sampling value V21 is the second potential Vout2 obtained at the first sampling time point ST1. The second potential second sampling value V22 is the second potential V2 obtained at the second sampling time point ST2.

[0170] Fig.21 The state in which the finger 51 contacts the electrostatic sensor 7 at a position close to the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged by the above method, the current for charging the electrostatic sensor 7 flows through the applying electrode 21 as indicated by the arrow I, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as indicated by the arrow J. In addition, the current for charging the electrostatic sensor 7 flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the second measurement position 31 as indicated by the arrow K.

[0171] like Fig.21 As shown, the distance between the first measurement position 29 and the position where the finger 51 contacts the electrostatic sensor 7 is shorter than the distance between the second measurement position 31 and the position where the finger 51 contacts the electrostatic sensor 7. Therefore, the resistance value R3 of the measurement electrode 22 between the first measurement position 29 and the finger 51 is smaller than the resistance value R4 of the measurement electrode 22 between the second measurement position 31 and the finger 51 (R3<R4). Therefore, in the electrostatic sensor 7, the time constant τ involved in the first potential V1 is different from the time constant τ involved in the second potential V2.

[0172] Fig. 22The time variation of the first potential Vout1 and the second potential Vout2 is shown. The first potential Vout1 is shown by a solid line, and the second potential Vout2 is shown by a single-point dashed line. The time constant τ involved in the second potential Vout2 is different from the time constant τ involved in the first potential Vout1, so the time variation of the second potential Vout2 is slower than the time variation of the first potential Vout1.

[0173] The measuring device 15 obtains the first potential first sampling value V11 and the first potential second sampling value V12, and calculates the ratio (V11 / V12) of the first potential first sampling value V11 to the first potential second sampling value V12. Based on this ratio, the measuring device 15 calculates the distance between the first measurement position 29 and the position where the finger 51 contacts the electrostatic sensor 7.

[0174] The measuring device 15 obtains the second potential first sampling value V21 and the second potential second sampling value V22, and calculates the ratio of the second potential first sampling value V21 to the second potential second sampling value V22 (V21 / V22). Based on this ratio, the measuring device 15 calculates the distance between the second measurement position 31 and the position where the finger 51 contacts the electrostatic sensor 7.

[0175] The measuring device 15 detects the position where the finger 51 contacts the electrostatic sensor 7 based on the first measuring position 29, the distance from the position where the finger 51 contacts the electrostatic sensor 7, and the second measuring position 31, the distance from the position where the finger 51 contacts the electrostatic sensor 7. According to this embodiment, the measuring device 15 can detect the position where the finger 51 contacts the electrostatic sensor 7 based on the first potential first sampling value V11 and the first potential second sampling value V12 involved in the first potential Vout1, and the second potential first sampling value V21 and the second potential second sampling value V22 involved in the second potential Vout2, thereby improving the accuracy of the contact detection device 70.

[0176] Fig.23 The state in which the finger 51 contacts the electrostatic sensor 7 at a position away from the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged by the above method, the current for charging the electrostatic sensor 7 flows in the applying electrode 21 as indicated by the arrow L, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as indicated by the arrow M. In addition, the current for charging the electrostatic sensor 7 flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the second measurement position 31 as indicated by the arrow N.

[0177] like Fig.23As shown, the distance between the first measurement position 29 and the position where the finger 51 contacts the electrostatic sensor 7 is longer than the distance between the second measurement position 31 and the position where the finger 51 contacts the electrostatic sensor 7. Therefore, the resistance value R2 of the measurement electrode 22 between the first measurement position 29 and the finger 51 is greater than the resistance value R4 of the measurement electrode 22 between the second measurement position 31 and the finger 51 (R2>R4). Therefore, in the electrostatic sensor 7, the time constant τ involved in the first potential V1 is different from the time constant τ involved in the second potential V2.

[0178] Fig.24 The temporal changes of the first potential V1 and the second potential V2 are shown. The first potential V1 is shown by a solid line, and the second potential V2 is shown by a dashed line. The time constant τ involved in the second potential V2 is different from the time constant τ involved in the first potential V1, so the temporal change of the first potential V1 is slower than the temporal change of the second potential V2.

[0179] Similar to the case where the finger 51 contacts the position close to the first measurement position 29 in the electrostatic sensor 7, the measuring device 15 can detect the position where the finger 51 contacts the electrostatic sensor 7 based on the first potential first sampling value V11 and the first potential second sampling value V12 related to the first potential V1, and the second potential first sampling value V21 and the second potential second sampling value V22 related to the second potential V2. Thus, the accuracy of the contact detection device 70 can be improved.

[0180] The configuration other than that described above is substantially the same as that of the first embodiment, and the same components are denoted by the same reference numerals to avoid redundant description.

[0181] According to this embodiment, the resistance per unit length of the applying electrode 21 and the measuring electrode 22 is different. In addition, the resistance per unit length of the measuring electrode 22 is greater than the resistance per unit length of the applying electrode 21. As a result, the first potential V1 obtained from the first end 27 of the measuring electrode 22 and the second potential V2 obtained from the second end 28 can be made different, so the accuracy of detecting the contact position of the conductor can be improved.

[0182] (Implementation 4)

[0183] Next, refer to Fig.25 Implementation method 4 is described below. Fig.25 As shown, in the contact detection device 80 of this embodiment, a second input switch element 18 is connected between the second end 28 of the applying electrode 21 and the power supply 41. The second input switch element 18 disconnects or closes the input voltage Vin applied from the power supply 41 to the second end 28 of the applying electrode 21. The second input switch element 18 is connected in parallel with the first input switch element 11.

[0184] The control device 14 controls the second input switch element 18 to be in a closed state or an open state. The control device 14 sets the first input switch element 11 and the second input switch element 18 to an open state, and sets the charge-discharge switch element 13 to a closed state, thereby executing the step of discharging the potential of the measuring electrode 22 to the ground potential 42. After the step of discharging the potential of the measuring electrode 22 to the ground potential 42, the control device 14 sets the charge-discharge switch element 13 to an open state, sets the first input switch element 11 to a closed state, and sets the second input switch element 18 to an open state, thereby executing the step of charging the electrostatic sensor 7 from the first end 27 of the electrostatic sensor 7. In addition, after the step of discharging the potential of the measuring electrode 22 to the ground potential 42, the control device 14 sets the charge-discharge switch element 13 to an open state, sets the first input switch element 11 to an open state, and sets the second input switch element 18 to a closed state, thereby executing the step of charging the electrostatic sensor 7 from the second end 28 of the electrostatic sensor 7.

[0185] Fig.26 The state in which the finger 51 contacts the electrostatic sensor 7 at a position close to the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged from the first end 27, the current charging the electrostatic sensor 7 flows in the applying electrode 21 as indicated by the arrow O, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as indicated by the arrow P. In addition, the current charging the electrostatic sensor 7 flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the second measurement position 31 as indicated by the arrow Q.

[0186] Fig. 27 The state in which the finger 51 contacts the electrostatic sensor 7 at a position close to the first measurement position 29 is shown. In this state, if the electrostatic sensor 7 is charged from the second end 28, the current for charging the electrostatic sensor 7 flows through the applying electrode 21 as indicated by the arrow R, and the charge is charged to the applying electrode 21 and the measuring electrode 22, and flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the first measurement position 29 as indicated by the arrow S. In addition, the current for charging the electrostatic sensor 7 flows from the portion of the measuring electrode 22 that overlaps with the finger 51 in the thickness direction to the second measurement position 31 as indicated by the arrow T.

[0187] Next, refer to Fig.28 , the operation of the contact detection device 80 of this embodiment will be described. Fig.28The flowchart involved in the main process of the contact detection device 80 of this embodiment is shown. When the contact detection device 80 is started, the first loop is executed (S10). Next, the second loop is executed (S20). Next, based on the results obtained in the first loop and the results obtained in the second loop, the position where the conductor such as the finger 51 contacts the electrostatic sensor 7 and the area where the conductor such as the finger 51 contacts the electrostatic sensor 7 are detected (S30). Through the above, the operation of the contact detection device 80 is completed.

[0188] Fig.29 Flowchart showing the first cycle. When the first cycle is executed (S10), the control device 14 sets the second input switch element 18 to an open state. The control device 14 sets the first input switch element 11 to an open state, and sets the charge and discharge switch element 13 to a closed state. Thus, in a state where the input voltage Vin is not applied to the application electrode 21, the potential of the measurement electrode 22 is discharged to the ground potential 42 (S11).

[0189] After a predetermined time has passed and the potential of the measuring electrode 22 is discharged to the ground potential 42, a step (S12) of charging the electrostatic sensor 7 is performed. In S12, the control device 14 sets the charging and discharging switch element 13 to an open state and sets the first input switch element 11 to a closed state. Thus, the electrostatic sensor 7 is charged from the first end 27 of the electrostatic sensor 7.

[0190] The step of charging the electrostatic sensor 7 (S12) is executed. During the period until the electrostatic sensor 7 is fully charged, the measuring device 15 measures and obtains the first potential first sampling value V11 at the first sampling time point ST1 after a predetermined time has passed since the start of charging of the electrostatic sensor 7, and measures and obtains the first potential second sampling value V12 at the second sampling time point ST2 after a predetermined time has passed since the first sampling time point ST1 (S13).

[0191] The measuring device 15 detects the position where the conductor contacts the electrostatic sensor 7 based on the ratio of the first potential first sampling value V11 to the first potential second sampling value V12 (S14). However, the measuring device 15 may also detect the position where the conductor contacts the electrostatic sensor 7 based on the ratio of the second potential first sampling value V21 to the second potential second sampling value V22.

[0192] The measuring device 15 detects the area of ​​the conductor in contact with the electrostatic sensor 7 based on the first potential second sampling value V12 (S15). However, the measuring device 15 may detect the area of ​​the conductor in contact with the electrostatic sensor 7 based on the second potential second sampling value V22.

[0193] Through the above, the first cycle (S10) ends.

[0194] Next, Fig.30 Flowchart showing the second cycle. When the second cycle is executed (S20), the control device 14 sets the first input switch element 11 to an open state. The control device 14 sets the second input switch element 18 to an open state, and sets the charge and discharge switch element 13 to a closed state. Thus, in a state where the input voltage Vin is not applied to the application electrode 21, the potential of the measurement electrode 22 is discharged to the ground potential 42 (S21).

[0195] After a predetermined time has passed and the potential of the measuring electrode 22 is discharged to the ground potential 42, a step (S21) of charging the electrostatic sensor 7 is performed. In S21, the control device 14 sets the charge and discharge switch element 13 to an open state and sets the second input switch element 18 to a closed state. As a result, the electrostatic sensor 7 is charged from the second end 28 of the electrostatic sensor 7.

[0196] The step of charging the electrostatic sensor 7 is executed (S21). During the period until the electrostatic sensor 7 is fully charged, the measuring device 15 measures and obtains the first sampling value V21 of the second potential at the first sampling time point ST1 after a predetermined time has passed since the start of charging of the electrostatic sensor 7, and measures and obtains the second sampling value V22 of the second potential at the second sampling time point ST2 after a predetermined time has passed since the first sampling time point ST1 (S23).

[0197] The measuring device 15 detects the position where the conductor contacts the electrostatic sensor 7 based on the ratio of the second potential first sampling value V21 to the second potential second sampling value V22 (S24). However, the measuring device 15 may also detect the position where the conductor contacts the electrostatic sensor 7 based on the ratio of the first potential first sampling value V11 to the first potential second sampling value V12.

[0198] The measuring device 15 detects the area of ​​the conductor in contact with the electrostatic sensor 7 based on the second potential second sampling value V22 (S25). However, the measuring device 15 may detect the area of ​​the conductor in contact with the electrostatic sensor 7 based on the first potential second sampling value V12.

[0199] Through the above, the second cycle (S20) ends.

[0200] The structure other than the above is substantially the same as that of the third embodiment, and the same components are denoted by the same reference numerals, and repeated descriptions are omitted.

[0201] According to this method, in order for the measuring device 15 to obtain the first potential V1, the control device 14 executes a first cycle (S10) including a discharge step and a charging step subsequent to the discharge step. After the first cycle, in order for the measuring device 15 to obtain the second potential V2, the control device 14 executes a second cycle (S20) including a discharge step and a charging step subsequent to the discharge step.

[0202] Thus, based on the result obtained in the first cycle (S10) and the result obtained in the second cycle (S20), the position where the conductor contacts the electrostatic sensor 7 can be detected, thereby improving the accuracy of the contact detection device 80. In addition, based on the result obtained in the first cycle (S10) and the result obtained in the second cycle (S20), the area where the conductor contacts the electrostatic sensor 7 can be detected, thereby improving the accuracy of the contact detection device 80.

[0203] (Implementation 5)

[0204] Next, refer to Fig.31 Embodiment 5 is described. The measuring electrode 22A of the electrostatic sensor 7A according to Embodiment 5 has the same shape and size as the applying electrode 21. The measuring electrode 22A of this embodiment is different from Embodiment 1 in that it does not have the through hole 26. The structure other than the above is substantially the same as that of Embodiment 1, and the same reference numerals are given to the same components, and repeated descriptions are omitted.

[0205] When a conductor such as a finger 51 contacts the measuring electrode 22A side of the electrostatic sensor 7A, a capacitor having the skin material 8 interposed therebetween is formed between the measuring electrode 22A and the conductor such as the finger 51. As a result, the electrostatic capacitance of the electrostatic sensor 7A changes. As the electrostatic capacitance changes, the electrostatic sensor 7A is charged, so that, as in the first embodiment described above, the position where the finger 51 contacts the electrostatic sensor 7A and the area where the finger 51 contacts the electrostatic sensor 7A can be detected.

[0206] The present invention is not limited to the above-described embodiments, and includes the following aspects within the scope not departing from the gist of the invention.

[0207] (1) A contact detection device comprising:

[0208] An electrostatic sensor comprising an applying electrode to which an input voltage as a constant voltage is applied from a power supply, a measuring electrode arranged to face the applying electrode and to measure a potential, and a dielectric arranged between the applying electrode and the measuring electrode, the electrostatic sensor being used to detect that a conductor has come into contact with the measuring electrode side;

[0209] a first bridging capacitor connected in series between the first measuring position of the measuring electrode and the ground potential;

[0210] a charge-discharge switch element connected in series between the measuring electrode and the ground potential and connected in parallel with the first bridge capacitor, and discharging the potential of the measuring electrode to the ground potential when in a closed state;

[0211] a control device, which sets the input voltage to the applying electrode in a state where the input voltage is not applied and sets the charging and discharging switching element in a closed state, thereby discharging the potential of the measuring electrode to the ground potential; and after the discharging step, sets the charging and discharging switching element in an open state and sets the input voltage to the applying electrode, thereby performing a step of charging the electrostatic sensor; and

[0212] a measuring device that acquires a first potential between the first measuring position of the measuring electrode and the first bridging capacitor in the charging step,

[0213] The electrostatic sensor is configured such that an electrostatic capacitance per unit area corresponding to a position in contact with the conductor and an electrostatic capacitance per unit area corresponding to a position in contact with the conductor have different values.

[0214] The measuring electrode is configured such that the resistance thereof changes according to the distance from the first measuring position.

[0215] The measuring device detects the position where the conductor contacts the electrostatic sensor based on the first potential, i.e., the first potential first sampling value, obtained at a first sampling time point after a predetermined time has passed from the start of charging of the electrostatic sensor in the charging step, and the first potential, i.e., the first potential second sampling value, obtained at a second sampling time point after a predetermined time has passed from the first sampling time point.

[0216] (2) The contact detection device according to (1) above, wherein:

[0217] The first sampling time point is a time point in a transition state from the start of charging of the electrostatic sensor until a change in the potential of the measuring electrode becomes smaller than a predetermined value before a saturation state.

[0218] The second sampling time point is a time point later than the first sampling time point, at which the potential of the measuring electrode is saturated.

[0219] (3) The contact detection device according to (2) above, wherein:

[0220] The measuring device detects a position where the conductor contacts the electrostatic sensor based on a ratio of a first sampling value of the first potential to a second sampling value of the first potential.

[0221] (4) The contact detection device according to (2) above, wherein:

[0222] The first sampling time point is a time point of 1 to 4 times a time constant τ when the electrostatic sensor is defined as an RC equivalent circuit, and the second sampling time point is a time point of 5 times or more the time constant τ.

[0223] (5) The contact detection device according to (2) above, wherein:

[0224] The measuring device further detects an area where the conductor contacts the electrostatic sensor based on a second sampled value of the first potential in the charging step.

[0225] (6) The contact detection device according to (5) above, wherein:

[0226] The contact detection device further includes a storage device, which stores the first potential when the potential of the measuring electrode is saturated, that is, the saturated first potential, in a state where the conductor contacts the entire surface of the measuring electrode side of the electrostatic sensor in the charging step.

[0227] The measuring device detects an area where the conductor contacts the electrostatic sensor based on the second sampling value of the first potential in the charging step and the saturated first potential.

[0228] (7) The contact detection device according to any one of (1) to (6) above, wherein:

[0229] The electrostatic sensor is formed into a shape elongated in the longitudinal direction and has a first end and a second end at both ends in the longitudinal direction.

[0230] The first bridging capacitor is connected between the first measurement position of the measuring electrode, that is, the first end in the longitudinal direction, and the ground potential.

[0231] The first end portion of the applying electrode in the longitudinal direction is connected to the power source.

[0232] (8) The contact detection device according to any one of (1) to (6) above, wherein:

[0233] The electrostatic sensor is formed into a shape elongated in the longitudinal direction and has a first end and a second end at both ends in the longitudinal direction.

[0234] The first bridging capacitor is connected between the first measurement position of the measuring electrode, that is, the first end in the longitudinal direction, and the ground potential.

[0235] The second end portion of the applying electrode in the longitudinal direction is connected to the power source.

[0236] (9) The contact detection device according to any one of (1) to (6) above, wherein:

[0237] The electrostatic sensor is formed into a shape elongated in the longitudinal direction and has a first end and a second end at both ends in the longitudinal direction.

[0238] The first bridging capacitor is connected between the first measurement position of the measuring electrode, that is, the first end in the longitudinal direction, and the ground potential.

[0239] The contact detection device further includes a second bridge capacitor connected in series between a second measurement position of the measurement electrode, that is, the second end portion in the longitudinal direction and the ground potential.

[0240] The measuring electrode is configured such that the resistance thereof changes according to the distance from the first measuring position, and is configured such that the resistance thereof changes according to the distance from the second measuring position.

[0241] The measuring device acquires a second potential between the second measuring position of the measuring electrode and the second bridging capacitor in the charging step,

[0242] The measuring device detects the position where the conductor contacts the electrostatic sensor based on the first potential first sampling value in the charging step, the second potential, i.e., the second potential first sampling value, obtained at the first sampling time point, the first potential second sampling value, and the second potential, i.e., the second potential second sampling value, obtained at the second sampling time point.

[0243] (10) The contact detection device according to (9) above, wherein:

[0244] The first sampling time point is a time point in a transition state from the start of charging of the electrostatic sensor until a change in the potential of the measuring electrode becomes smaller than a predetermined value before a saturation state.

[0245] The second sampling time point is later than the first sampling time point and is a time point at which the potential of the measuring electrode is saturated.

[0246] In the charging step, the measuring device further detects an area where the conductor contacts the electrostatic sensor based on the first potential second sampling value and the second potential second sampling value.

[0247] (11) The contact detection device according to (9) above, wherein:

[0248] The control device executes a first cycle including the step of discharging and the step of charging subsequent to the step of discharging in order to allow the measuring device to obtain the first potential.

[0249] After the first cycle, the control device executes a second cycle including the step of discharging and the step of charging following the step of discharging in order to allow the measuring device to acquire the second potential.

[0250] (12) The contact detection device according to any one of (1) to (6) above, wherein:

[0251] The measuring electrode and the applying electrode are formed of a conductive elastic body.

[0252] (13) The contact detection device according to (12) above, wherein:

[0253] The applying electrode and the measuring electrode have different resistances per unit length.

[0254] (14) The contact detection device according to (13) above, wherein:

[0255] The resistance per unit length of the measuring electrode is greater than the resistance per unit length of the applying electrode.

[0256] (15) The contact detection device according to (14) above, wherein:

[0257] The measuring electrode has a plurality of through holes.

[0258] (16) A contact detection device comprising:

[0259] An electrostatic sensor comprising an applying electrode to which an input voltage as a constant voltage is applied from a power supply, a measuring electrode arranged to face the applying electrode and to measure a potential, and a dielectric arranged between the applying electrode and the measuring electrode, the electrostatic sensor being used to detect that a conductor has come into contact with the measuring electrode side;

[0260] a first bridging capacitor connected in series between the first measuring position of the measuring electrode and the ground potential;

[0261] a charge-discharge switch element connected in series between the measuring electrode and the ground potential and connected in parallel with the first bridge capacitor, and discharging the potential of the measuring electrode to the ground potential when in a closed state;

[0262] a control device, which sets the input voltage to the applying electrode in a state where the input voltage is not applied and sets the charging and discharging switching element in a closed state, thereby executing a step of discharging the potential of the measuring electrode to a ground potential; and after the discharging step, sets the charging and discharging switching element in an open state and sets the input voltage to the applying electrode, thereby executing a step of charging the electrostatic sensor; and

[0263] a measuring device that acquires a first potential between the first measuring position of the measuring electrode and the first bridging capacitor in the charging step,

[0264] The electrostatic sensor is configured such that an electrostatic capacitance per unit area corresponding to a position in contact with the conductor and an electrostatic capacitance per unit area corresponding to a position in contact with the conductor have different values.

[0265] The measuring electrode is configured such that the resistance thereof changes according to the distance from the first measuring position.

[0266] The measuring device detects the area where the conductor contacts the electrostatic sensor based on the first potential, ie, the first potential saturation sampling value, acquired at a time point when the potential of the measuring electrode in the charging step becomes saturated below a predetermined value.

Claims

1. A contact detection device (10, 60, 70, 80), comprising: An electrostatic sensor (7, 7A) comprising an application electrode (21) for applying an input voltage (Vin) as a constant voltage from a power supply (41), a measuring electrode (22, 22A) arranged to face the application electrode and measure the potential, and a dielectric (23) arranged between the application electrode and the measuring electrode, the electrostatic sensor (7, 7A) being used to detect a contact with a conductor (51, 52); a first bridging capacitor (12) connected in series between a first measuring position (29) of the measuring electrode and a ground potential (42); a charge-discharge switch element (13) connected in series between the measuring electrode and the ground potential and connected in parallel with the first bridge capacitor, and discharging the potential of the measuring electrode to the ground potential when in a closed state; a control device (14) configured to set the input voltage not to be applied to the applying electrode and to set the charging and discharging switching element to a closed state, thereby executing a step (S1) of discharging the potential of the measuring electrode to a ground potential; and, after the discharging step, to set the charging and discharging switching element to an open state and to set the input voltage to be applied to the applying electrode, thereby executing a step (S2) of charging the electrostatic sensor; as well as A measuring device (15) which, in the charging step, obtains a first potential (V1) between the first measuring position of the measuring electrode and the first bridging capacitor, wherein: The electrostatic sensor is configured such that the electrostatic capacitance changes according to at least one of the area in contact with the conductor and the distance from the conductor, and the time constant (τ) changes through the resistance corresponding to the distance from the first measurement position. The measuring device detects the position where the conductor contacts the electrostatic sensor based on the first potential, i.e., the first potential first sampling value (V11), obtained at a first sampling time point (ST1) after a predetermined time has passed since the start of charging of the electrostatic sensor in the charging step, and the first potential, i.e., the first potential second sampling value (V12), obtained at a second sampling time point (ST2) after a predetermined time has passed since the first sampling time point.

2. The contact detection device according to claim 1, wherein: The first sampling time point is a time point in a transition state from a predetermined first time after the start of charging of the electrostatic sensor until the change in the potential of the measuring electrode reaches a saturated state. The second sampling time point is a time point later than the first sampling time point and after a predetermined second time has elapsed since charging of the electrostatic sensor was started.

3. The contact detection device according to claim 2, wherein: The measuring device detects a position where the conductor contacts the electrostatic sensor based on a ratio of a first sampling value of the first potential to a second sampling value of the first potential.

4. The contact detection device according to any one of claims 1 to 3, wherein: The electrostatic sensor is formed into a shape elongated in the longitudinal direction and has a first end (27) and a second end (28) at both ends in the longitudinal direction. The first bridging capacitor is connected between the first measurement position of the measuring electrode, that is, the first end in the longitudinal direction, and the ground potential. The first end portion of the applying electrode in the longitudinal direction is connected to the power source.

5. The contact detection device according to any one of claims 1 to 3, wherein: The electrostatic sensor is formed into a shape elongated in the longitudinal direction and has a first end and a second end at both ends in the longitudinal direction. The first bridging capacitor is connected between the first measurement position of the measuring electrode, that is, the first end in the longitudinal direction, and the ground potential. The second end portion of the applying electrode in the longitudinal direction is connected to the power source.

6. The contact detection device according to any one of claims 1 to 3, wherein: The electrostatic sensor is formed into a shape elongated in the longitudinal direction and has a first end and a second end at both ends in the longitudinal direction. The first bridging capacitor is connected between the first measurement position of the measuring electrode, that is, the first end in the longitudinal direction, and the ground potential. The contact detection device further comprises a second bridge capacitor (17) connected in series between a second measurement position of the measurement electrode, that is, the second end in the longitudinal direction and the ground potential. The measuring electrode is configured such that the resistance thereof changes according to the distance from the first measuring position, and is configured such that the resistance thereof changes according to the distance from the second measuring position. The measuring device acquires a second potential (V2) between the second measuring position of the measuring electrode and the second bridging capacitor in the charging step, The measuring device detects the position where the conductor contacts the electrostatic sensor based on the first potential first sampling value in the charging step, the second potential obtained at the first sampling time point, i.e., the second potential first sampling value (V21), the first potential second sampling value, and the second potential obtained at the second sampling time point, i.e., the second potential second sampling value (V22).

7. The contact detection device according to claim 6, wherein: In order for the measuring device to acquire the first potential, the control device executes a first cycle including the step of discharging and the step of charging subsequent to the step of discharging. After the first cycle, the control device executes a second cycle including the step of discharging and the step of charging following the step of discharging in order to allow the measuring device to acquire the second potential.

8. The contact detection device according to any one of claims 1 to 3, wherein: The measuring electrode and the applying electrode are formed of a conductive elastic body.

9. The contact detection device according to claim 8, wherein: The resistance per unit length of the measuring electrode is different from the resistance per unit length of the applying electrode.

10. The contact detection device according to claim 9, wherein: The resistance per unit length of the measuring electrode is greater than the resistance per unit length of the applying electrode.

11. The contact detection device according to claim 10, wherein: The measuring electrode has a plurality of through holes (26).

12. A contact detection device comprising: An electrostatic sensor comprising an applying electrode to which an input voltage as a constant voltage is applied from a power supply, a measuring electrode arranged to face the applying electrode and to measure a potential, and a dielectric arranged between the applying electrode and the measuring electrode, the electrostatic sensor being used to detect that a conductor has come into contact with the measuring electrode side; a first bridging capacitor connected in series between the first measuring position of the measuring electrode and the ground potential; a charge-discharge switch element connected in series between the measuring electrode and the ground potential and connected in parallel with the first bridge capacitor, and discharging the potential of the measuring electrode to the ground potential when in a closed state; a control device configured to discharge the potential of the measuring electrode to a ground potential by setting the input voltage not to be applied to the applying electrode and setting the charging and discharging switching element to a closed state; and after the step of discharging, setting the charge and discharge switching element to an OFF state and setting the input voltage to a state where the application electrode is applied, thereby performing a step of charging the electrostatic sensor; as well as a measuring device, which, in the charging step, obtains a first potential between the first measuring position of the measuring electrode and the first bridging capacitor, wherein: The electrostatic sensor is configured such that electrostatic capacitance changes according to at least one of an area and a distance from the conductor, and a time constant changes due to resistance corresponding to a distance from the first measurement position. In the charging step, the measuring device detects the area where the conductor contacts the electrostatic sensor based on the first potential, i.e., the second sampling value of the first potential, obtained at a second time point after a predetermined second time has passed since the start of charging of the electrostatic sensor and later than a first time point in a transitional state until the change in the potential of the measuring electrode becomes a saturated state, and after a predetermined first time has passed since the start of charging of the electrostatic sensor.

13. The contact detection device according to claim 12, wherein: In the charging step, the measuring device obtains the first potential at the first time point, that is, the first potential first sampling value, and detects the position where the conductor contacts the electrostatic sensor based on the first potential first sampling value and the first potential second sampling value.

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