Touch detection device

Abstract

A touch detection device according to the present invention includes: a steering body; a plurality of sensor units that each generate an electrostatic capacitance between a sensor electrode provided to an outer circumferential part of a base body of the steering body and a person in contact with the steering body; a detection unit that detects the electrostatic capacitance at each sensor electrode; a correction unit that uses difference values indicating the change in the electrostatic capacitance at each sensor electrode as detected by the detection unit to correct the electrostatic capacitance at each sensor electrode as detected by the detection unit; and a determination unit that determines the state of contact between the person and the steering body on the basis of the corrected electrostatic capacitances.

Description

Touch Detection Device

[0001] The present disclosure relates to a touch detection device that detects a touch by an occupant.

[0002] Japanese Patent Application Publication No. 2017-87883 discloses a contact determination processing device in which a shield layer is formed on the core wire (and heater layer) side to surround the core wire for a contact sensor whose output changes depending on whether the occupant is in contact with or not in contact with the steering wheel.

[0003] This contact determination processing device determines a contact state when the output of the contact sensor is equal to or greater than a predetermined threshold, and determines a non-contact state when the output is less than the predetermined threshold. In this case, the contact determination processing device detects or estimates the temperature of the steering wheel or the ambient temperature, and changes the threshold value according to the detected or estimated temperature. Furthermore, when a heater for heating the steering wheel is driven, the contact determination processing device lowers the threshold value by a predetermined value until a predetermined time has elapsed since the heater was driven or until the heater reaches a predetermined temperature.

[0004] In vehicles, there is a demand for cost reduction in the configuration for detecting when an occupant touches the steering wheel, and in the case of a steering wheel or touch sensor, the structure can be simplified and costs can be reduced by eliminating the shield layer (shield electrode).

[0005] Furthermore, the dielectric constant of the insulating material interposed between the sensor electrode and the core or heater changes depending on the temperature. Therefore, if the shield electrode arranged on the core side of the sensor electrode is removed, the parasitic capacitance generated in the sensor electrode changes due to temperature changes in the vehicle interior, which causes a problem of reduced detection accuracy of touch detection using the sensor electrode.

[0006] The present disclosure provides a touch detection device that can suppress a decrease in detection accuracy in touch detection that detects a touch of an occupant on a steering wheel.

[0007] The touch detection device of the first aspect includes a steering body in which a conductive core part grounded to the vehicle body is covered with an insulating base and is touched and operated by an occupant to steer the vehicle; a plurality of sensor parts, each of which generates capacitance between a sensor electrode arranged on the outer periphery of the base of the steering body and the occupant contacting the steering body; a detection part for detecting the capacitance of each of the sensor electrodes; a correction part for correcting the capacitance of each of the sensor electrodes detected by the detection part using a differential value indicating a change in the capacitance of each of the sensor electrodes detected by the detection part; and a determination part for determining the contact state of the occupant with the steering body based on the corrected capacitance.

[0008] In a touch detection device of a second aspect, in the first aspect, the sensor electrode is provided on one surface of a sheet-like insulating support and faces the core metal portion.

[0009] A touch detection device of a third aspect is the touch detection device of the first or second aspect, wherein the sensor electrodes are arranged in pairs on the left and right sides of the steering body in the vehicle width direction.

[0010] A fourth aspect of the touch detection device is any one of the first to third aspects, wherein the correction unit sets a correction value for correcting the capacitance of each of the sensor electrodes using the absolute value of the difference value for each of the sensor electrodes.

[0011] A fifth aspect of the touch detection device is the fourth aspect, and includes a temperature detection unit that detects changes in the environmental temperature around the steering body, and the correction unit sets the correction value from each of the difference values ​​and the change in the environmental temperature.

[0012] A sixth aspect of the touch detection device is the fourth or fifth aspect, wherein the correction unit sets an initial value of a reference value of the capacitance of each of the sensor electrodes from the capacitance of each of the sensor electrodes when the steering body is not in contact with an occupant, and includes a reference value setting unit that updates and sets each of the reference values ​​using the correction value, and the correction unit corrects the capacitance of each of the sensor electrodes using the updated reference value set for each of the sensor electrodes.

[0013] A seventh aspect of the touch detection device is any one of the fourth to sixth aspects, in which the correction unit evaluates whether the correction value is less than a predetermined threshold value, and if it is evaluated that the correction value is less than the threshold value, corrects the capacitance of each of the sensor electrodes using the correction value.

[0014] The touch detection device of an eighth aspect is the touch detection device of any one of the first to seventh aspects, further including a heating section that is provided in the base body of the steering body and operates to heat the steering body.

[0015] A touch detection device of a ninth aspect is the eighth aspect that references the seventh aspect, wherein the threshold value is changed depending on an operating state of the heating unit.

[0016] A tenth aspect of the touch detection device is the ninth aspect, wherein the threshold value is set higher when the heating unit is operating than when the heating unit is not operating.

[0017] In a touch detection device according to a first aspect of the present disclosure, a steering wheel that is touched and operated by an occupant to steer a vehicle has a core metal portion coated with an insulating base that is grounded to the vehicle body. The steering wheel has a plurality of sensor units disposed thereon. Each sensor unit has a sensor electrode disposed on the outer periphery of the base of the steering wheel, and the sensor electrode generates capacitance with the occupant in contact with the steering wheel. A detection unit detects the capacitance of each of the sensor electrodes, and a determination unit determines the state of contact of the occupant with the steering wheel based on the capacitance of each sensor electrode corrected by the correction unit.

[0018] On the other hand, parasitic capacitance occurs between the sensor electrode and the core metal portion, heater, etc., and this parasitic capacitance appears in the electrostatic capacitance of the sensor electrode. Temperature changes in the base, etc. cause the parasitic capacitance to change, which in turn causes the electrostatic capacitance appearing in the sensor electrode to change.

[0019] The correction unit corrects the capacitance of each sensor electrode detected by the detection unit using a difference value indicating a change in capacitance for each sensor electrode detected by the detection unit, thereby suppressing the change in capacitance even if the capacitance changes due to a change in parasitic capacitance or the like in the sensor electrode.

[0020] In the touch detection device of the second aspect, a sensor electrode is provided on one surface of a sheet-like insulating support and faces the metal core, and each sensor does not have a shield electrode that has a function of electrically insulating the sensor electrode from the metal core.

[0021] The correction unit corrects the capacitance of each sensor electrode detected by the detection unit using a difference value indicating the change in capacitance of each sensor electrode detected by the detection unit. This makes it possible to accurately determine the state of contact of the occupant with the steering body even if the capacitance of the sensor electrode changes due to changes in parasitic capacitance, etc., without providing a shield electrode between the sensor electrode and the core portion, etc.

[0022] In the touch detection device of the third aspect, the sensor electrodes are arranged in pairs on the left and right sides of the steering wheel in the vehicle width direction, thereby making it possible to accurately determine whether the occupant is gripping the steering wheel with both hands or one hand.

[0023] In the touch detection device of the fourth aspect, the correction unit sets a correction value for correcting the capacitance of each sensor electrode using the absolute value of the difference value for each sensor electrode. The change in capacitance due to a change in parasitic capacitance is different from the change in capacitance due to the state of contact of the occupant with the steering wheel and is smaller than the change in capacitance due to the state of contact of the occupant with the steering wheel. Therefore, for example, by using a difference value with a small absolute value among the multiple difference values, it is possible to prevent the capacitance from being corrected more than necessary.

[0024] In the touch detection device of the fifth aspect, the temperature detection unit detects changes in the ambient temperature of the steering body, and the correction unit sets a correction value based on each of the difference values ​​and the change in the ambient temperature. Because the parasitic capacitance of the sensor electrode changes depending on the temperature, using the change in the ambient temperature to set the correction value enables setting of a more appropriate correction value.

[0025] In the touch detection device of the sixth aspect, the reference value setting unit sets an initial value of the reference value of the capacitance of each sensor electrode from the capacitance of each sensor electrode when the occupant is not in contact with the steering body, and updates and sets each of the reference values ​​using the correction value. The correction unit corrects the capacitance of each sensor electrode using the updated reference value set for each sensor electrode.

[0026] Here, the reference value is a capacitance that mainly corresponds to the parasitic capacitance, and by correcting and updating this reference value from its initial value with a correction value, the capacitance of each sensor electrode is corrected using the corrected (updated) reference value for each sensor electrode. This allows the corrected capacitance to be used to accurately determine the contact state (touch detection).

[0027] In the touch detection device of the seventh aspect, it is evaluated whether the correction value is less than a preset threshold value, and if it is evaluated that the correction value is less than the threshold value, the capacitance of each sensor electrode is corrected using the correction value, thereby preventing the capacitance of each sensor electrode from being corrected more than necessary.

[0028] In the touch detection device of the eighth aspect, a heating unit is provided in the base of the steering body, which is activated to heat the steering body. As a result, when the heating unit is activated, the parasitic capacitance of each sensor electrode increases, resulting in a large change in capacitance. However, since the detected capacitance can be corrected in accordance with the change in capacitance, a decrease in the accuracy of the determination of the contact state (touch detection) can be suppressed.

[0029] In the touch detection device of the ninth aspect, the threshold value is changed depending on the operating state of the heating unit. In the touch detection device of the tenth aspect, the threshold value when the heating unit is operating is set higher than the threshold value when the heating unit is not operating. This allows the correction value to be large when the heating unit is operating, so that the capacitance of each sensor electrode can be appropriately corrected.

[0030] 1 is a block diagram showing a schematic configuration of a touch detection device according to an embodiment of the present invention; FIG. 2 is a front view showing an outline of a steering wheel; FIG. 3 is a cross-sectional view showing an outline of a main part of the steering wheel as viewed in a radial direction; BASE 5A and 5B are diagrams illustrating an example of setting of a reference value according to a change in temperature (ambient temperature) over time; FIG. 5B is a diagram illustrating an example of a change in capacitance over time based on FIGS. 5A and 5B;

[0031] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. A touch detection device 10 according to the present embodiment is provided in a steering device 12 of a vehicle and detects whether an occupant is gripping a steering wheel 14 of the steering device 12.

[0032] Fig. 1 shows a block diagram of the schematic configuration of the touch detection device 10. Fig. 2 shows a schematic front view of the steering wheel 14 of the steering device 12 as seen from the driver's side, and Fig. 3 shows a schematic cross-sectional view of the main parts of the steering wheel 14 as seen from the radial direction. In the drawings, the right side in the vehicle width direction is indicated by an arrow HR, and the upward direction is indicated by an arrow UP.

[0033] The steering device 12 functions as an operating device operated by a vehicle occupant (driver). The steering wheel 14 is provided on the steering device 12. The steering wheel 14 is disposed in front of a seat (driver's seat, not shown) in which the occupant (driver) who drives the vehicle sits, and the steering wheel 14 functions as an operating body and a steering body operated by the occupant.

[0034] 2, the steering wheel 14 includes a substantially annular rim portion 16 as a grip portion, a boss portion 18 provided at the center of the rim portion 16, and a stay portion 20 connecting the rim portion 16 and the boss portion 18. In the drawing, the radial direction of the steering wheel 14 is indicated by an arrow R.

[0035] The steering wheel 14 has a metal core that serves as the core that forms the framework. The core is made up of a substantially annular rim core 24 (see FIG. 3 ) of the rim 16, a boss core (not shown) of the boss 18, and a stay core (not shown) of the stay 20. The boss core and the rim core 24 are connected by the stay core, so that the rim 16, boss 18, and stay 20 are integrated into one body.

[0036] The steering device 12 includes a steering shaft (not shown), which is rotatably supported by the vehicle body in front of the driver's seat with its axis aligned approximately in the longitudinal direction of the vehicle. The steering wheel 14 has a boss core portion of a boss portion 18 fixed to the rear end of the steering shaft, and the steering wheel 14 is supported by the vehicle body so as to be rotatable together with the steering shaft, and the core portion is grounded to the vehicle body via the steering shaft.

[0037] In a vehicle, when the steering wheel 14 of the steering device 12 is rotated, the steering shaft is rotated, and the steered wheels (front wheels) are steered to steer the vehicle. Note that Fig. 2 shows the steering wheel 14 when the vehicle is traveling straight ahead.

[0038] As shown in Figure 3, a base body 22 made of an insulating resin material such as urethane is disposed on the rim portion 16 of the steering wheel 14. The base body 22 covers a rim core metal portion 24 of the rim portion 16, and the rim core metal portion 24 is housed within the base body 22 by insert molding. Figure 3 shows a schematic view of the main portion of the rim portion 16 in a developed cross section along the circumferential direction of the rim portion 16.

[0039] The steering wheel 14 has a decorative portion 26 as a contact portion (skin) disposed radially outside the base body 22, and the decorative portion 26 is made of leather or resin (part of which may be made of wood) and has insulating properties. The rim portion 16 of the steering wheel 14 is covered with the decorative portion 26 over the entire circumference of the base body 22 in a radial cross section of the steering wheel 14 and over the entire circumference (entire area) of the steering wheel 14.

[0040] The steering device 12 may also be provided with a heater (electric heater) 30 as a heating section (warming section) in the steering wheel 14. Note that only a portion of the heater 30 is shown in Figures 1 and 2 .

[0041] The heater 30 uses an electric heating wire or the like, surrounds almost the entire outer periphery of the outer periphery of the base 22 within the rim portion 16, and is installed in a required range (e.g., almost the entire circumference) around the outer periphery of the base 22 in the circumferential direction of the steering wheel 14. The heater 30 is attached to a support sheet 32 ​​that functions as a base and uses an insulating material and urethane foam or the like as a support member, and the support sheet 32 ​​is attached to the outer periphery of the base 22 radially outward of the rim portion 16.

[0042] On the other hand, the touch detection device 10 is of a capacitance type (self-capacitance type), and includes a sensor unit (sensor) 40 for detecting the approach of an occupant, and a controller 42. The touch detection device 10 also includes a temperature sensor 44 as a temperature detector for detecting the ambient temperature.

[0043] The sensor unit 40 includes a sensor electrode 46 and a sensor sheet 48 serving as a support. The sensor electrode 46 and the sensor sheet 48 are each in the form of a long sheet (film), and the sensor unit 40 uses a conductive material for the sensor electrode 46 and a resin material serving as an insulating material (dielectric) for the sensor sheet 48.

[0044] The sensor unit 40 has a layered structure in which a sensor electrode 46 is disposed on one surface of a sensor sheet 48, and no shield electrode is provided. The sensor unit 40 is disposed on the outside of the base 22 in the rim portion 16, with the sensor electrode 46 facing the decorative portion 26 (the sensor sheet 48 facing the base 22). The sensor unit 40 is disposed over substantially the entire periphery of the base 22 (substantially the entire area in the cross-sectional circumferential direction of the rim portion 16) within a predetermined range in the circumferential direction of the steering wheel 14.

[0045] As a result, when an occupant grips the rim portion 16 of the steering wheel 14 and comes into contact with the rim portion 16 (decorative portion 26), the occupant's hand is brought into proximity with the sensor electrode 46 of the sensor unit 40. When the heater 30 is disposed on the rim portion 16, the sensor unit 40 is disposed outside the support sheet 32 ​​of the heater 30 (between the support sheet 32 ​​and the decorative portion 26). When the heater 30 is installed on the steering wheel 14, the base 22 is made thinner (the radial dimension is reduced) by the thickness of the heater 30 and the support sheet 32.

[0046] 1 and 2, the touch detection device 10 uses two sensor units 40 (40L, 40R), with the sensor unit 40L arranged in a range covering approximately half the circumference on the left side in the vehicle width direction in the circumferential direction of the steering wheel 14, and the sensor unit 40R arranged in a range covering approximately half the circumference on the right side in the vehicle width direction. As a result, when an occupant grips the steering wheel 14 (rim portion 16), the occupant's left hand is brought close to the sensor unit 40L, and the occupant's right hand is brought close to the sensor unit 40R. In the sensor unit 40, when the occupant touches the rim portion 16, electrostatic capacitance is generated between the sensor electrode 46 and the occupant.

[0047] In the touch detection device 10, the sensor units 40L and 40R have substantially the same configuration, and hereinafter, when there is no need to distinguish between the sensor units 40L and 40R, they will be described as the sensor unit 40. The temperature sensor 44 of the touch detection device 10 is disposed near the steering wheel 14 or near the rim portion 16 of the steering wheel 14 (for example, the boss portion 18 or the stay portion 20), and detects the temperature of the installation environment of the rim portion 16 (the temperature inside the vehicle cabin as the environmental temperature). In the touch detection device 10, the controller 42 is disposed near the steering wheel 14, and the temperature sensor 44 is disposed within the controller 42. However, the temperature sensor 44 may be disposed within the rim portion 16 and directly detect the temperature of the base 22, etc.

[0048] As shown in FIG. 1 , in the touch detection device 10 , the sensor unit 40 (sensor units 40L and 40R) and the temperature sensor 44 are electrically connected to the controller 42 .

[0049] Furthermore, when a heater 30 is installed on the steering wheel 14, the steering device 12 is equipped with a heater controller 34 that controls the operation of the heater 30, and the heater 30 and a controller 42 are connected to the heater controller 34. When a heater switch (not shown) is turned on, the heater controller 34 energizes the heater 30 and outputs a heater-on signal to the controller 42. When the heater switch is turned off, the heater controller 34 stops energizing the heater 30 and outputs a heater-off signal to the controller 42.

[0050] In the steering device 12, when current is applied to the heater 30, the rim portion 16 of the steering wheel 14 is heated to a predetermined temperature, preventing a passenger from feeling cold when touching the rim portion 16. Note that the heater control unit 34 may stop the application of current to the heater 30 and output a heater-off signal to the controller 42 when a predetermined time has elapsed since the heater 30 was powered (turned on).

[0051] The controller 42 includes a microcomputer in which a CPU, ROM, RAM, and non-volatile storage are connected by a bus, as well as required functional circuits (all not shown). In the controller 42, the CPU as a processor reads and executes a touch detection program stored in the ROM and storage as memory, thereby realizing a touch detection function using the required functional circuits. The controller 42 may also use a field programmable gate array (FPGA) or a programmable logic array (PLA) as a processor. The touch detection function may be performed by one of these various processors, or by a combination of two or more processors of the same or different types. The hardware structure of these various processors is, more specifically, an electric circuit combining circuit elements such as semiconductor elements.

[0052] The controller 42 is formed with a detector 50, a capacitance correction unit 52 constituting a correction unit, and a determination unit 54. The controller 42 also is formed with a filter unit 56 constituting the correction unit, a difference value generation unit 58, a comparison unit 60, a reference value setting unit 62, and a temperature filter unit 64. In the controller 42, the processor executes the touch detection program or the like to realize the functions of the correction unit including the capacitance correction unit 52, the filter unit 56, the difference value generation unit 58, the comparison unit 60, and the reference value setting unit 62, and the determination unit 54. The function of the temperature filter unit 64 may also be realized by executing the touch detection program or the like.

[0053] The detection unit 50, capacitance correction unit 52, filter unit 56, and differential value generation unit 58 include a detection unit 50L, capacitance correction unit 52L, filter unit 56L, and differential value generation unit 58 for the sensor unit 40L, and a detection unit 50R, capacitance correction unit 52R, filter unit 56R, and differential value generation unit 58R for the sensor unit 40R. The detection units 50L and 50R, the capacitance correction units 52L and 52R, the filter units 56L and 56R, and the differential value generation units 58L and 58R have the same basic configuration. For this reason, hereinafter, when there is no need to distinguish between the sensor unit 40L and the sensor unit 40R, they will be described as the detection unit 50, capacitance correction unit 52, filter unit 56, and differential value generation unit 58.

[0054] When an occupant comes into contact with the rim portion 16, a capacitance is generated between the sensor electrode 46 disposed on the rim portion 16 and the occupant. Furthermore, a parasitic capacitance may be generated between the sensor electrode 46 and the rim core metal portion 24. This parasitic capacitance varies depending on the dielectric constant of the insulating material used in the base 22 (and support sheet 32), etc., and the dielectric constant of the base 22, etc. varies depending on the temperature of the base 22 (and support sheet 32), etc.

[0055] The sensor electrode 46 of the sensor unit 40L is connected to the detection unit 50L, and the sensor electrode 46 of the sensor unit 40R is connected to the detection unit 50R. The detection unit 50 (50L, 50R) detects (measures) the capacitance generated in the sensor electrode 46 at predetermined time intervals. At this time, the detection unit 50 detects the potential output from the sensor electrode 46 in accordance with the capacitance, and outputs the capacitance (capacitance value) C(t) generated in the sensor electrode 46 at every time t from the detected potential. As a result, the detection unit 50L measures the capacitance C(t) generated in the sensor unit 40L. Ｌ (t), and the detection unit 50R outputs the capacitance C Ｒ (t) is output.

[0056] The capacitance correction unit 52 (52L, 52R) corrects the capacitance C detected by the detection unit 50. Ｌ (t), C Ｒ (t) is the reference value (capacitance value) C for correction set in the reference value setting unit 62 BASE_Ｌ (t), C BASE_ＲAs a result, the capacitance corrector 52L corrects the temperature by using the capacitance C touch_Ｌ (t), and the capacitance correction unit 52R outputs the capacitance C touch_Ｒ (t) is output.

[0057] The determination unit 54 determines a preset threshold value Th for determining a touch (state determination). judge Using the capacitance C touch_Ｌ (t), C touch_Ｒ Based on this threshold value Th (t), it is determined whether or not the occupant is in contact with the sensor units 40L and 40R. judge A value (capacitance value) set in accordance with a change in capacitance that occurs when an occupant approaches the sensor electrode 46 is applied to the capacitance.

[0058] The determination unit 54 outputs a state signal G(t) indicating the state of the occupant's grip on the steering wheel 14 (touch state including whether or not the occupant is touching the steering wheel 14) based on the determination result.

[0059] On the other hand, the filter unit 56 (56L, 56R), the difference value generation unit 58 (58L, 58R), the comparison unit 60, and the reference value setting unit 62 that constitute the correction unit begin to operate when the judgment unit 54 detects that the occupant is gripping (touching) the steering wheel 14 (a state signal G(t) indicating gripping is output).

[0060] When it is detected that the occupant is gripping (cantilevering) the steering wheel 14 with only the left hand or the right hand, the filter unit 56 on the side where gripping is not detected and the differential value generation unit 58 may stop processing. For example, when the occupant is gripping the steering wheel 14 with the right hand (when no touch is detected on the sensor unit 40L side), the filter unit 56R and the differential value generation unit 58R may start processing, and the filter unit 56L and the differential value generation unit 58L may stop processing.

[0061] The filter section 56 (56L, 56R) has a capacitance C Ｌ (t), C ＲThe filter unit 56 performs the noise component removal process from (t). For example, the noise component removal process is performed by using n times of capacitance C Ｒ , C Ｌ As a result, the filter unit 56L performs a moving average process to average the capacitance C Ｌ (t), and the filter unit 56R outputs the filtered capacitance C Ｒ The noise removal process (filtering process) is not limited to the moving average, but also uses a smoothly changing (noise component suppressed) capacitance C Ｌ (t), C Ｒ As long as the configuration (t) can be obtained, the present invention is not limited to this.

[0062] The difference value generating unit 58 (58L, 58R) calculates the capacitance C Ｌ (t), C Ｒ (t) and the capacitance C after the previous filtering process Ｌ (t-1), C Ｒ The difference between (t-1) is calculated, and the difference value (capacitance value) ΔC, which is the amount of change in capacitance, is obtained. Ｌ (t), ΔC Ｒ That is, the difference value generating unit 58L outputs the difference value ΔC Ｌ (t) (= C Ｌ (t)-C Ｌ (t-1)) to the comparison unit 60, and the difference value generation unit 58L outputs the difference value ΔC Ｒ (t) (= C Ｒ (t)-C Ｒ (t-1)) is output to the comparison unit 60.

[0063] The temperature filter unit 64 is connected to the temperature sensor 44, and acquires temperature T as temperature information from the temperature sensor 44 at predetermined time intervals, performs predetermined filtering, and outputs the filtered temperature T(t) to the comparison unit 60. In the filtering process in the temperature filter unit 64, for example, an averaged temperature T(t) is acquired using a moving average of n temperatures T. Note that the noise removal process in the temperature filter unit 64 is not limited to the moving average, and is not limited to this as long as it is configured to obtain a temperature T(t) that changes smoothly (with noise components suppressed).

[0064] The comparison unit 60 calculates the difference value ΔC Ｌ (t) and the difference value ΔC Ｒ (t) is compared with the difference value ΔC(t) to set the correction value ΔC(t). Ｌ Absolute value of (t) |ΔC Ｌ (t) | and the difference value ΔC Ｒ Absolute value of (t) |ΔC Ｒ (t)| is compared. At this time, the change in capacitance in the sensor unit 40 may be a change caused by the temperature T and a change caused by the movement of the occupant, and the change caused by the movement of the occupant is larger than the change caused by the temperature T.

[0065] From this, the comparison unit 60 calculates the absolute value |ΔC Ｌ (t) |, |ΔC Ｒ (t) | Ｌ (t) (or ΔC Ｒ (t)) is a candidate for the correction value ΔC(t).

[0066] In addition, the comparison unit 60 calculates the difference value ΔC Ｌ (t), ΔC Ｒ The sign of temperature T(t) is determined, and whether the temperature T(t) is trending upward or downward.

[0067] At this time, the comparison unit 60 calculates the difference value ΔC Ｌ (t), ΔC Ｒ When the sign of each of (t) is "+" (positive, plus), and when the sign of each of (t) is "-" (negative, minus), the absolute value |ΔC Ｌ (t) |, |ΔC Ｒ (t) | Ｌ (t) (or ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0068] In addition, the comparison unit 60 calculates the difference value ΔC Ｌ (t), ΔC ＲIf one sign of (t) is "+" and the other sign is "-" (negative, minus), the temperature T(t) (the change tendency of the temperature T(t)) is used to set the correction value ΔC(t). In this case, the comparison unit 60 uses the absolute value |ΔC Ｌ (t) |, |ΔC Ｒ (t) | The difference value ΔC of the one with the sign "+" Ｌ (t) (or ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0069] On the other hand, in the comparison unit 60, when the temperature T(t) is on a downward trend (when the temperature T(t) is lower than the previous temperature T(t-1)), the difference value ΔC Ｌ (t), ΔC Ｒ The difference value ΔC of (t) with the sign "-" Ｌ (t) (or ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0070] Furthermore, if the heater 30 is installed in the steering wheel 14, there is a possibility that the temperature T(t) may not fully reflect the temperature of the base 22 (steering wheel 14). From this, the comparison unit 60 acquires a signal indicating whether the heater 30 is on or off from the heater control unit 34. The comparison unit 60 acquires the difference value ΔC when the heater 30 is on and the difference value ΔC Ｌ (t), ΔC Ｒ If one sign of (t) is "+" and the other sign is "-" (negative, minus), the difference value ΔC Ｌ (t), ΔC Ｒ The difference value ΔC of (t) with a sign "+" Ｌ (t) (or ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0071] The correction value ΔC(t) set in the comparison unit 60 is the original difference value ΔC Ｌ (t) or the difference value ΔC Ｒ The value of (t) (capacitance value) including its sign is inherited. Ｌ (t), ΔC ＲIf one sign of (t) is "+" and the other sign is "-" (negative, minus), and it is determined that there is no change in the temperature T(t) (if it is determined that there is neither an upward nor downward trend), the correction direction cannot be properly determined, so the correction value ΔC(t) is set to "0" (ΔC(t) = 0).

[0072] On the other hand, the reference value setting unit 62 sets a reference value C as an initial value (capacitance value) for the sensor units 40L and 40R in advance. BASE_Ｌ (t), reference value C BASE_Ｒ (t) is set. BASE_Ｌ (t), reference value C BASE_Ｒ The initial value of (t) is the capacitance C detected from the sensor units 40L and 40R when, for example, an ignition switch (not shown) of the vehicle is turned on and the touch detection device 10 starts operating. Ｌ (t), C Ｒ (t) is used. That is, the reference value C BASE_Ｌ (t), reference value C BASE_Ｒ The capacitance (mainly due to parasitic capacitance) when the occupant is not touching the sensor units 40L and 40R is applied to (t).

[0073] Furthermore, when the heater 30 is installed in the steering wheel 14 , a signal indicating whether the heater 30 is on or off is input from the heater control unit 34 to the reference value setting unit 62 .

[0074] Furthermore, the reference value setting unit 62 sets the reference value C using the correction value ΔC(t). BASE_Ｌ (t), C BASE_Ｒ A threshold value Th for determining whether or not to correct (t) BASE is set, and the reference value setting unit 62 sets the threshold value Th BASE The correction value ΔC(t) is evaluated using the threshold value Th BASE It is preferable that a plurality of values ​​(capacitance values) are set for the capacitance in response to changes in temperature T(t), on / off of the heater 30, etc.

[0075] Threshold Th BASE The conditions for changing the temperature T(t) include a change in the temperature T(t), the state of the heater 30 (on or off), and the detected capacitance (capacitance C Ｌ(t), C Ｒ (t)) and the difference value (difference value ΔC Ｌ (t), ΔC Ｒ (t)) and the like. BASE An example is shown.

[0076] As shown in Fig. 4, the temperature T(t) can be divided into three stages: rising (rising trend), no change, or falling (falling trend). The state of the heater 30 can be divided into two stages: on or off. Furthermore, the capacitance detected by the sensor unit 40 can be divided into two stages: increasing (rising trend) or decreasing (falling trend).

[0077] From here, the threshold value Th BASE As for Th BASE１ From Th BASE１２ In addition, when the heater 30 is not installed, the heater state is limited to off, so the threshold value Th BASE It is conceivable that the threshold value Th can be set in six stages. BASE The threshold Th can be set by predicting the change in parasitic capacitance in advance in accordance with each condition, or by measuring the change in parasitic capacitance in accordance with the condition, and setting a value based on the predicted or measured result. BASE The number of (threshold Th BASE The stages are not limited to these.

[0078] Here, as an example, in the touch detection device 10, when the heater 30 is installed on the steering wheel 14, the threshold value Th BASE As a result, the reference value setting unit 62 sets the threshold value Th BASE The threshold value Th applied when the heater 30 is turned on is BASE_Ｈ and the value Th applied when the heater 30 is turned off. BASE_Ｌ At this time, since the change in capacitance due to the parasitic capacitance when the heater 30 is turned on is large, the reference value setting unit 62 sets the threshold value ThBASE_Ｈ is the value Th applied when the heater 30 is turned off. BASE_Ｌ is set to a value greater than BASE_Ｈ >Th BASE_Ｌ ).

[0079] In the evaluation, the reference value setting unit 62 uses the correction value ΔC(t) and the threshold value Th BASE When comparing the absolute value |ΔC(t)| of the correction value ΔC(t), the reference value setting unit 62 uses the absolute value |ΔC(t)| as a threshold value Th BASE If |ΔC(t)|<Th BASE ), the correction value ΔC(t) corresponds to a change in parasitic capacitance caused by a change in temperature T, and it is evaluated that correction is preferable. As a result, the reference value setting unit 62 calculates the reference value C using the correction value ΔC(t). BASE_Ｌ (t), C BASE_Ｒ (t) is set to be corrected.

[0080] At this time, the reference value setting unit 62 sets the threshold value Th BASE Threshold Th BASE_Ｈ is applied, and when the heater 30 is off, the threshold Th BASE Threshold Th BASE_Ｌ The reference value setting unit 62 turns on the heater 30 and sets the threshold value Th BASE Threshold Th BASE_Ｈ When the heater 30 is turned off, the threshold value Th BASE Threshold Th BASE_Ｈ to threshold Th BASE_Ｌ Change (revert) to

[0081] In addition, since the heater 30 is temperature-controlled by the heater control unit 34, the reference value setting unit 62 sets the threshold value Th BASE Threshold Th BASE_Ｈ When the heater 30 is turned on, the threshold value Th BASE Threshold Th BASE_Ｌ As this time, for example, the time until the temperature rise is stopped, such as the time until the steering wheel 14 reaches a predetermined temperature (the control temperature of the heater 30), can be applied.

[0082] The reference value setting unit 62 calculates the reference value C using the correction value ΔC(t). BASE_Ｌ (t), C BASE_Ｒ When it is set to perform correction of (t), the reference value C is calculated using the correction value ΔC(t). BASE_Ｌ (t), C BASE_Ｒ That is, the reference value setting unit 62 executes the following calculation process: C BASE_Ｌ (t) = C BASE_Ｌ (t-1)+ΔC(t) C BASE_Ｒ (t) = C BASE_Ｒ (t-1)+ΔC(t)

[0083] As a result, the reference value C BASE_Ｌ (t), C BASE_Ｒ Each of the reference values ​​C(t) is increased when the correction value ΔC(t) is positive (ΔC(t)>0) and decreased when the correction value ΔC(t) is negative (ΔC(t)<0). BASE_Ｌ (t), C BASE_Ｒ (t) indicates the previous reference value C BASE_Ｌ (t-1), C BASE_Ｒ (t-1) is applied (C BASE_Ｌ (t) = C BASE_Ｌ (t-1), C BASE_Ｒ (t) = C BASE_Ｒ (t-1)).

[0084] The capacitance correction unit 52 (52L, 52R) calculates the capacitance C Ｌ (t), C Ｒ (t) The reference value C corresponding to the parasitic capacitance BASE_Ｌ (t), C BASE_Ｒ By subtracting (t), the capacitance C used for touch determination is obtained. touch_Ｌ (t), C touch_Ｒ That is, the capacitance corrector 52L calculates the capacitance C touch_Ｌ (t) (= C Ｌ (t)-C BASE_Ｌ (t)) is calculated and output by the capacitance correction unit 52R, and the capacitance C touch_Ｒ (t) (= C Ｒ (t)-C BASE_Ｒ (t)) is calculated and output.

[0085] As a result, the determination unit 54 determines the capacitance C Ｌ (t), C Ｒ (t) is temperature-corrected to obtain the capacitance C touch_Ｌ (t), C touch_Ｒ Using (t), it is possible to determine whether the steering wheel 14 is being gripped by the occupant.

[0086] Next, the operation of the touch detection device 10 will be described as an action of this embodiment. In the touch detection device 10, when the ignition switch of the vehicle is turned on, the controller 42 starts operation, and the detection units 50L and 50R detect the capacitances C Ｌ (t), C Ｒ (t) detection is started, and the detected capacitance C Ｌ (t), C Ｒ Start outputting (t).

[0087] When the controller 42 starts operation, the reference value setting unit 62 calculates the capacitance C Ｌ Based on (t), the reference value C BASE_Ｌ The initial value of (t) is set, and the capacitance C detected by the sensor unit 40R is Ｒ Based on (t), the reference value C BASE_Ｒ At this time, since the occupant is not gripping (touching) the steering wheel 14, the capacitance C Ｌ (t), C Ｒ (t) is a capacitance mainly due to parasitic capacitance (a capacitance not affected by an occupant). Therefore, the reference value setting unit 62 sets the capacitance C Ｌ (t), C Ｒ (t) is the reference value C BASE_Ｌ (t) C BASE_Ｒ It can be set to the initial value of (t).

[0088] Furthermore, when the controller 42 starts operating, the temperature filter unit 64 also starts operating. As a result, the temperature filter unit 64 starts outputting the temperature T(t), which is the moving average (n-time moving average) of the temperature T detected by the temperature sensor 44.

[0089] After the touch detection device 10 starts operating, when the occupant grips the steering wheel 14 with both hands to steer the vehicle, the occupant's hands approach the sensor units 40L and 40R, and the capacitance C Ｌ (t), C Ｒ As a result, the capacitance C output from the capacitance correction units 52L and 52R increases. touch_Ｌ (t), C touch_Ｒ Each of (t) is a threshold Th judge Exceeds (C touch_Ｌ (t)>Th judge , C touch_Ｒ (t)>Th judge ), the determination unit 54 determines that grasping with both hands has begun. This determination result is output as a state signal G(t) from the determination unit 54.

[0090] When the controller 42 detects that the occupant has started to grip the steering wheel 14, the correction unit starts to operate. As a result, the filter units 56L and 56R respectively correct the capacitance C Ｌ (t), and the capacitance C detected by the sensor unit 40R Ｒ The filter units 56L and 56R start filtering the filtered capacitance C Ｌ (t), C Ｒ (t) is output to the difference value generating units 58L and 58R.

[0091] The differential value generating unit 58L generates the filtered capacitance C Ｌ The difference value ΔC indicating the change in (t) Ｌ (t) (= C Ｌ (t)-C Ｌ (t-1)) is calculated and output. Ｒ The difference value ΔC indicating the change in (t) Ｒ (t) (= C Ｒ (t)-C Ｒ (t-1)) is calculated and output.

[0092] Here, the comparison unit 60 calculates the difference value ΔC Ｌ (t) and the difference value ΔC Ｒ (t), and based on the comparison result, a reference value CBASE_Ｌ (t), C BASE_Ｒ The comparator 60 sets a correction value ΔC(t) for the temperature T(t). The comparator 60 also uses the filtered temperature T(t) as needed to set the correction value ΔC(t). Ｌ (t), difference value ΔC Ｌ Absolute value of (t) |ΔC Ｌ (t)|, difference value ΔC Ｒ (t), difference value ΔC Ｒ Absolute value of (t) |ΔC Ｒ (t)| and the temperature T(t) are used to set the correction value ΔC(t).

[0093] At this time, the comparison unit 60 calculates the difference value ΔC Ｌ (t), ΔC Ｒ If both of (t) have the sign "+" or "-" (if they have the same sign), the absolute value |ΔC Ｌ (t) |, |ΔC Ｒ (t) | Ｌ (t) (or difference value ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0094] In addition, the comparison unit 60 calculates the difference value ΔC Ｌ (t), ΔC Ｒ If one sign of the temperature T(t) is "+" and the other sign is "-", the change trend of the temperature T(t) is used. In this case, if the temperature T(t) is on an upward trend, the comparison unit 60 uses the difference value ΔC Ｌ (t), ΔC Ｒ The difference value ΔC of (t) with a sign "+" Ｌ (t) (or difference value ΔC Ｒ If the temperature T(t) is decreasing, the comparator 60 sets the difference value ΔC Ｌ (t), ΔC Ｒ The difference value ΔC of (t) with the sign "-" Ｌ (t) (or difference value ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0095] In the touch detection device 10, for example, the temperature sensor 44 detects the ambient temperature around the steering wheel 14, but the temperature sensor 44 is not necessarily able to detect the temperature of the base 22, etc. For this reason, even if the heater 30 is turned on and a temperature rise occurs in the base 22, etc. of the steering wheel 14, this may not be reflected in the temperature T(t).

[0096] From this, the touch detection device 10 may estimate that the temperature T(t) is on an increasing trend if the heater 30 is on. Ｌ (t), ΔC Ｒ When one sign of (t) is "+" and the other sign is "-" and the heater 30 is turned on, the difference value ΔC Ｌ (t), ΔC Ｒ The difference value ΔC of (t) with a sign "+" Ｌ (t) (or difference value ΔC Ｒ (t)) is set as the correction value ΔC(t).

[0097] When the correction value ΔC(t) is set in this way, the reference value setting unit 62 uses the correction value ΔC(t) to set the reference value C BASE_Ｌ (t), C BASE_Ｒ At this time, the reference value setting unit 62 corrects the threshold value Th according to whether the heater 30 is on or off. BASE and set this threshold Th BASE is used to determine whether the correction value ΔC(t) is appropriate (whether correction is necessary or not) (the correction value ΔC(t) is evaluated).

[0098] At this time, the absolute value |ΔC(t)| of the correction value ΔC(t) is the threshold value Th BASE If |ΔC(t)| < Th BASE ), the correction value ΔC(t) is mainly a change in parasitic capacitance, and the correction value ΔC(t) is used to calculate the reference value C BASE_Ｌ (t), C BASE_Ｒ (t) is corrected. As a result, the reference value C corresponding to the parasitic capacitance according to the temperature is obtained. BASE_Ｌ (t) (= C BASE_Ｌ (t-1)+ΔC(t)) and reference value C BASE_Ｒ (t) (= C BASE_Ｒ(t-1)+ΔC(t)) is obtained.

[0099] The capacitance correction unit 52L corrects the capacitance C detected by the sensor unit 40L in the detection unit 50L. Ｌ (t) and the reference value C BASE_Ｌ (t), and the capacitance C Ｌ (t) to the reference value C BASE_Ｌ (t) minus capacitance C touch_Ｌ (t) is calculated (C touch_Ｌ (t) = C Ｌ (t)-C BASE_Ｌ (t)). The capacitance correction unit 52R corrects the capacitance C detected by the sensor unit 40R in the detection unit 50R. Ｒ (t) and the reference value C BASE_Ｒ (t), and the capacitance C Ｒ (t) to the reference value C BASE_Ｒ (t) minus capacitance C touch_Ｒ (t) is calculated (C touch_Ｒ (t) = C Ｒ (t)-C BASE_Ｒ (t)).

[0100] The determination unit 54 determines the capacitance C touch_Ｌ (t) and threshold Th judge is used to determine whether the left side of the steering wheel 14 (the left hand of the occupant) is being gripped, and the capacitance C touch_Ｒ (t) and threshold Th judge At this time, the determination unit 54 determines whether the right side of the steering wheel 14 (the right hand of the occupant) is being gripped using the capacitance C touch_Ｌ (t) is the threshold value Th judge If it is greater than (C touch_Ｌ (t)>Th judge ), the determination unit 54 determines that the left side of the steering wheel 14 (the sensor unit 40L portion) is being gripped. touch_Ｒ (t) is the threshold value Th judge If it is greater than (C touch_Ｒ (t)>Th judge ), it is determined that the right side of the steering wheel 14 (the sensor unit 40R portion) is being gripped.

[0101] 5A to 5C show the temperature T(t) and capacitance C Ｌ (t), capacitance C Ｒ (t), and the reference value C BASE 5A shows the change in temperature T(t) with respect to time t, and FIG. 5B shows the change in capacitance C(t) with respect to time t. Ｌ (t) and capacitance C Ｒ (t) is shown, and FIG. 5C shows the change in the reference value C BASE In addition, in FIG. 5C, the reference value C BASE_Ｌ (t) and the reference value C BASE_Ｒ (t) is regarded as the same as the reference value C BASE (t).

[0102] As shown in FIG. 5A, the temperature T(t) gradually increases with the change in time t. ３ In the figure, the time t １ , t ２ , t ３ Gat １ <t ２ <t ３ It states that:

[0103] Also, as shown in FIG. 5B, the capacitance C Ｌ (t) is the time t ３ It increases until it reaches ３ When it reaches t, it starts to decrease. ２ The degree of increase changes (becomes larger) in the capacitance C Ｒ (t) is the time t １ through time t ２ It gradually decreases until it reaches ２ After passing this point, the temperature starts to rise, and then at time t ３ It is expected that the number will start to decrease once this period is passed.

[0104] Here, time t ２ Until then, the capacitance C Ｌ (t) difference value ΔC Ｌ (t) becomes "+", and the capacitance C Ｒ (t) difference value ΔCＲ (t) is "-". At this time, the temperature T(t) is increasing, so the capacitance C Ｌ (t) difference value ΔC Ｌ (t) is set as the correction value ΔC(t). As a result, as shown in FIG. 5C, the reference value C BASE (t) is the capacitance C Ｌ It changes to increase in the same way as (t).

[0105] Also, at time t ２ From time t ３ Between Ｌ (t) difference value ΔC Ｌ (t), and capacitance C Ｒ (t) difference value ΔC Ｒ (t) are both "+". At this time, the capacitance C Ｌ (t) changes with the capacitance C Ｒ Since the change in (t) is small, the absolute value |ΔC Ｒ (t) | is the absolute value |ΔC Ｌ (t) | becomes smaller than (|ΔC Ｌ (t) |>|ΔC Ｒ (t)|). This gives the reference value C BASE (t) is the time t ２ From time t ３ Between them, the capacitance C Ｒ It changes to increase in the same way as (t).

[0106] Furthermore, at time t ３ When the temperature T(t) starts to decrease after Ｌ (t) difference value ΔC Ｌ (t), and capacitance C Ｒ (t) difference value ΔC Ｒ (t) are both "-". Also, the capacitance C Ｌ (t) changes with the capacitance C Ｒ The change in (t) is small, so the absolute value |ΔC Ｒ (t) | is the absolute value |ΔC Ｌ (t) | becomes smaller than (|ΔC Ｌ (t) |>|ΔC Ｒ (t)|). This gives the reference value C BASE (t) is the time t ３By passing this, the capacitance C Ｒ It changes to decrease in the same way as (t).

[0107] In this way, in the touch detection device 10, the detection units 50L and 50R have capacitance C Ｌ (t), C Ｒ The sensor 50 detects (t) and the determination unit 54 performs touch detection (touch determination, determination of grip state), thereby determining the state of contact of the occupant with the steering wheel 14. Furthermore, in the sensor units 40L and 40R, no electrical shielding unit such as a shield electrode is provided between the sensor electrode 46 and the rim core metal portion 24.

[0108] Here, in the controller 42, the differential value generating units 58L and 58R calculate the filtered capacitance C Ｌ (t), C Ｒ The difference value ΔC of the change in (t) Ｌ (t), ΔC Ｒ (t) is generated, and the generated difference value ΔC Ｌ (t), ΔC Ｒ (t), the capacitance C detected by the detection units 50L and 50R Ｌ (t), C Ｒ (t) is corrected.

[0109] As a result, in the touch detection device 10, the parasitic capacitance and the like change in each of the sensor electrodes 46, and the capacitance C Ｌ (t), C Ｒ Even if (t) changes, the capacitance C touch_Ｌ (t), C touch_Ｒ (t) can be used to make a touch determination.

[0110] In the touch detection device 10, the sensor unit 40L is disposed on the left side in the vehicle width direction of the steering wheel 14, and the sensor unit 40R is disposed on the right side in the vehicle width direction. This allows the touch detection device 10 to accurately detect whether the occupant is gripping the steering wheel 14 with both hands, one hand, or no hand.

[0111] In the touch detection device 10, the comparison unit 60 calculates the filtered capacitance C Ｌ (t), C Ｒ(t) difference value ΔC Ｌ (t), ΔC Ｒ Absolute value of (t) |ΔC Ｌ (t) |, |ΔC Ｒ (t)| is used to set the correction value ΔC(t). At this time, the correction value ΔC(t) is set to the absolute value |ΔC Ｌ (t) |, |ΔC Ｒ (t) | the smallest difference value ΔC Ｌ (t) (or difference value ΔC Ｒ (t)) can be applied.

[0112] As a result, the capacitance C corresponding to the parasitic capacitance, which is smaller than the capacitance caused by the movement of the occupant, is touch_Ｌ (t), C touch_Ｒ (t) is obtained, so the capacitance C touch_Ｌ (t), C touch_Ｒ Therefore, in the touch detection device 10, the capacitance C touch_Ｌ (t), C touch_Ｒ This can prevent a decrease in touch determination accuracy caused by a large correction of (t).

[0113] Furthermore, the touch detection device 10 sets the correction value ΔC(t) based on the temperature T(t). Therefore, the touch detection device 10 can obtain the correction value ΔC(t) that appropriately corresponds to the parasitic capacitance that changes depending on the temperature T(t).

[0114] In addition, in the touch detection device 10, the capacitance C Ｌ (t), C Ｒ (t) is used as the initial value, and the reference value C is updated using the correction value ΔC(t). BASE_Ｌ (t), C BASE_Ｒ As a result, the touch detection device 10 uses the capacitance C Ｌ (t), C Ｒ (t) is the capacitance C excluding the capacitance corresponding to the parasitic capacitance touch_Ｌ (t), Ct ouch_Ｒ Since (t) can be used, touch determination can be performed with high accuracy.

[0115] In addition, in the touch detection device 10, the threshold value Th BASEThe correction value ΔC(t) is evaluated using the BASE Since the capacitance does not satisfy the threshold value ΔC(t) and is evaluated as appropriate, the touch detection device 10 performs correction using the correction value ΔC(t). This makes it possible to prevent the touch detection device 10 from performing unnecessary correction, such as using the capacitance that has changed due to the movement of the occupant.

[0116] Furthermore, in the case where the heater 30 is installed on the steering wheel 14, the touch detection device 10 determines the threshold value Th according to whether the heater 30 is on or off (operating state). BASE Also, the threshold value Th BASE is the threshold value Th used when the heater 30 is off. BASE_Ｌ is used when the heater 30 is turned on. BASE_Ｈ This makes it possible to suppress corrections including changes in capacitance due to the movement of the occupant.

[0117] In the above-described embodiment, correction is mainly performed when the steering wheel 14 is held with both hands. However, the touch detection device 10 can also be applied to a case where one hand is held, for example, when a right-hand grip is detected or a left-hand grip is detected (or vice versa).

[0118] In this case, the capacitance C Ｌ (t) difference value ΔC Ｌ A correction value ΔC(t) is set according to the temperature T(t), and the threshold value Th is calculated for the set correction value ΔC(t). BASE In this way, when the correction value ΔC(t) is less than the threshold value, the correction value ΔC(t) is used to evaluate the reference value C BASE_Ｌ (t), C BASE_Ｒ (t) is corrected and updated. BASE_Ｌ Not only (t) but also the reference value C BASE_Ｒ Since (t) can be updated, a more appropriate contact state can be determined.

[0119] In addition, in this embodiment, the sensor unit 40 is used in which the sensor electrode 46 is arranged on one surface of the sensor sheet 48. However, the sensor unit may be configured in any manner as long as the sensor electrode is arranged on the outer periphery of the base body and capacitance is generated between the sensor electrode and the occupant (hands or fingers) who is placed close to the steering body.

[0120] In the embodiment described above, the sensors 40L and 40R are provided on the steering wheel 14. However, three or more sensors (sensor electrodes) may be provided on the steering body. In this case, the difference between the capacitances detected by the respective sensor electrodes is calculated, and the absolute values ​​of the calculated difference values ​​are compared, and a correction value is set based on the comparison result.

[0121] In this embodiment, a single threshold value Th is used as a threshold value for touch determination (determination of a contact state). judge However, a plurality of threshold values ​​may be set as the threshold value for determining whether or not a touch is made, such as a threshold value corresponding to a state in which the occupant grips the steering wheel tightly, a threshold value corresponding to a state in which the occupant grips the steering wheel lightly, and a threshold value corresponding to a state in which the occupant lightly touches the steering wheel.

[0122] Furthermore, in this embodiment, the capacitance C Ｌ (t), C Ｒ (t) and the capacitance C for touch determination. touch_Ｌ (t), C touch_Ｒ However, a capacitance for touch determination may be obtained corresponding to a combined capacitance of capacitances detected by each of the plurality of sensor electrodes. In this case, at least a threshold value for determining one-handed gripping and a threshold value for determining two-handed gripping may be set as the threshold value for touch determination.

[0123] In addition, in this embodiment, the steering wheel 14 is described as being substantially annular. However, the steering body is not limited to being substantially annular, and may be a non-standard steering wheel having a substantially rectangular shape in which a pair of grip portions are arranged on the left and right sides of a boss portion and each grip portion is connected to the boss portion at one or more points, or may be a D-shape (flat bottom shape), etc.

[0124] The touch detection program described in this embodiment may be provided in a form stored in a non-transitory storage medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. The touch detection program may also be downloaded from an external device via a network.

[0125] The disclosure of Japanese Patent Application No. 2023-206513, filed on December 6, 2023, is incorporated herein by reference in its entirety.

[0126] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A touch detection device comprising: a steering wheel having a conductive core part grounded to the vehicle body covered by an insulating base, which is touched and operated by an occupant to steer a vehicle; a plurality of sensor parts, each of which generates capacitance between a sensor electrode arranged on the outer periphery of the base of the steering wheel body and the occupant touching the steering wheel body; a detection part for detecting the capacitance of each of the sensor electrodes; a correction part for correcting the capacitance of each of the sensor electrodes detected by the detection part using a difference value indicating a change in capacitance for each of the sensor electrodes detected by the detection part; and a judgment part for judging the contact state of the occupant with the steering wheel body based on the corrected capacitance.

2. The touch detection device according to claim 1, wherein the sensor electrode is provided on one surface of a sheet-like insulating support and faces the metal core.

3. A touch detection device according to claim 1, wherein the sensor electrodes are arranged in pairs on the left and right sides of the steering body in the vehicle width direction.

4. The touch detection device according to claim 1, wherein the correction unit sets a correction value for correcting the capacitance of each of the sensor electrodes using an absolute value of the difference value for each of the sensor electrodes.

5. A touch detection device as described in claim 4, further comprising a temperature detection unit that detects a change in an environmental temperature around the steering body, and the correction unit sets the correction value from each of the difference values ​​and the change in the environmental temperature.

6. The touch detection device described in claim 4, wherein the correction unit includes a reference value setting unit that sets an initial value of a reference value of the capacitance of each of the sensor electrodes from the capacitance of each of the sensor electrodes when an occupant is not in contact with the steering body, and updates and sets each of the reference values ​​using the correction value, and the correction unit corrects the capacitance of each of the sensor electrodes using the updated reference value set for each of the sensor electrodes.

7. The touch detection device of claim 4, wherein the correction unit evaluates whether the correction value is less than a preset threshold value, and if it is evaluated that the correction value is less than the threshold value, corrects the capacitance of each of the sensor electrodes using the correction value.

8. The touch detection device according to claim 7, further comprising a heating section provided in said base body in said steering body and operable to heat said steering body.

9. The touch detection device according to claim 8, wherein the threshold value is changed according to an operating state of the heating section.

10. The touch detection device according to claim 9, wherein the threshold value is set higher when the heating unit is in operation than when the heating unit is not in operation.

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