Touch detection device

Abstract

To provide a touch detection device in which deterioration in detection accuracy is prevented.SOLUTION: A touch detection device 10 is designed such that, in each of sensor units 40L, 40R disposed in a steering wheel 14, a sensor electrode 46 faces a core metal portion via a base body. In a controller 42, a detection unit 50 detects electrostatic capacitances CL(t), CR(t), and sets reference values CBASE_L(t), CBASE_R(t) for correcting the electrostatic capacitances CL(t), CR(t) detected by a detection unit 50 from difference values ΔCL(t), ΔCR(t) indicating changes in the electrostatic capacitances CL(t), CR(t). A determination unit 54 performs touch determination using electrostatic capacitances Ctouch_L(t), Ctouch_R(t) obtained by correcting the electrostatic capacitances CL(t), CR(t). As a result, even when parasitic capacitance changes due to temperature, the touch of an occupant on the steering wheel 14 can be accurately detected.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a touch detection device that detects contact of an occupant.

Background Art

[0002] Patent Document 1 discloses a contact determination processing device in which a shield layer is formed so as to surround a core metal on the core metal (and heater layer) side with respect to a contact sensor whose output changes according to the contact state and non-contact state of an occupant with a steering wheel.

[0003] In this contact determination processing device, when the output of the contact sensor is equal to or greater than a predetermined threshold value, it is determined that the contact state exists, and when the output is less than the predetermined threshold value, it is determined that the non-contact state exists. At this time, the contact determination processing device detects or estimates the temperature of the steering wheel or the ambient temperature, and the threshold value is changed according to the detected or estimated temperature. Further, in the contact determination processing device, when a heater for heating the steering wheel is driven, the threshold value is decreased by a predetermined value until a predetermined time elapses after the driving or until a predetermined temperature is reached.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a vehicle, cost reduction is desired for a configuration for detecting an occupant's touch on a steering wheel. In the steering wheel or touch sensor, the structure can be simplified and the cost can be reduced by removing a shield layer (shield electrode).

[0006] In addition, the dielectric constant and the like of the insulating material interposed between the sensor electrode and the core metal or the heater change according to the temperature. For this reason, when the shield electrode arranged on the core metal part side of the sensor electrode is excluded, the parasitic capacitance generated in the sensor electrode changes due to the temperature change in the vehicle interior, and there is a problem that the detection accuracy of touch detection using the sensor electrode decreases.

[0007] The present invention has been made in view of the above facts, and an object thereof is to provide a touch detection device capable of suppressing a decrease in detection accuracy in touch detection for detecting contact of an occupant with a steering wheel.

Means for Solving the Problems

[0008] To achieve the above object, a touch detection device according to a first aspect includes a steering body in which a conductive core metal part grounded to a vehicle body is covered with an insulating base body and the vehicle is steered by being contacted and operated by an occupant, a plurality of sensor parts in which a capacitance is generated between a sensor electrode arranged on an outer peripheral part of the base body of the steering body and an 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 by using a difference value indicating a change in the capacitance of each of the sensor electrodes detected by the detection part, and a determination part for determining a contact state of an occupant with the steering body based on the corrected capacitance.

[0009] A touch detection device according to a second aspect is the touch detection device according to the first aspect, wherein the sensor electrode is provided on one surface of a sheet-like insulating support body and faces the core metal part.

[0010] A touch detection device according to a third aspect is the touch detection device according to the first or second aspect, wherein the sensor electrodes are arranged in pairs on the left and right in the vehicle width direction in the steering body.

[0011] In the touch detection device according to the fourth aspect, in any one of the first to third aspects, the correction unit includes setting a correction value for correcting the capacitance of each sensor electrode using the absolute value of the difference value for each sensor electrode.

[0012] The touch detection device according to the fifth aspect includes a temperature detection unit that detects a change in the ambient temperature around the steering body in the fourth aspect, and the correction unit sets the correction value from each of the difference values and the change in the ambient temperature.

[0013] The touch detection device according to the sixth aspect includes, in the fourth or fifth aspect, a reference value setting unit that sets an initial value of a reference value of the capacitance for each sensor electrode from the capacitance for each sensor electrode in a state where no occupant is 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 for each sensor electrode using the updated reference value for each sensor electrode.

[0014] In the touch detection device according to the seventh aspect, in any one of the fourth to sixth aspects, the correction unit evaluates whether the correction value is less than a preset threshold value, and when it is evaluated that the correction value is less than the threshold value, corrects the capacitance for each sensor electrode using the correction value.

[0015] The touch detection device according to the eighth aspect includes heating means that is provided in the base body in the steering body and operates to heat the steering body in any one of the first to seventh aspects.

[0016] In the touch detection device according to the ninth aspect, in the eighth aspect that cites the seventh aspect, the threshold value is changed according to the operating state of the heating means.

[0017] In the touch detection device according to the tenth aspect, in the ninth aspect, the threshold value is set higher when the heating means is operating than when the heating means is not operating.

Advantages of the Invention

[0018] In the touch detection device according to the first aspect of the present invention, in a steering body that is touched and operated by an occupant to steer a vehicle, a core metal portion covered with an insulating base is grounded to the vehicle body. A plurality of sensor portions are arranged on the steering body. In each sensor portion, sensor electrodes are arranged on the outer peripheral portion of the base of the steering body, and a capacitance is generated between the sensor electrodes and an occupant who touches the steering body. A detection unit detects the capacitance of each of the sensor electrodes, and a determination unit determines the contact state of the occupant with the steering body based on the capacitance of each sensor electrode corrected by a correction unit.

[0019] On the other hand, a parasitic capacitance is generated between the sensor electrode and the core metal portion, heater, etc., and the parasitic capacitance appears in the capacitance of the sensor electrode. When a temperature change or the like occurs in the base or the like, the parasitic capacitance changes, and the capacitance that appears in the sensor electrode changes.

[0020] Here, the correction unit uses a difference value indicating the change in the capacitance of each sensor electrode detected by the detection unit to correct the capacitance of each sensor electrode detected by the detection unit. Thereby, even if the parasitic capacitance or the like changes in the sensor electrode and the capacitance changes, the correction unit can suppress this change in capacitance.

[0021] In the touch detection device according to the second aspect, sensor electrodes are provided on one surface of a sheet-like insulating support and are opposed to the core metal portion. Further, in each of the sensor portions, a shield electrode having a function of electrically shielding between the sensor electrode and the core metal portion is not arranged.

[0022] Here, the correction unit corrects the capacitance of each sensor electrode detected by the detection unit by using a difference value indicating the change in capacitance for each sensor electrode detected by the detection unit. As a result, even if the parasitic capacitance or the like changes and the capacitance of the sensor electrode changes without providing a shield electrode between the sensor electrode and the core metal part or the like, it is possible to accurately determine the contact state of the occupant with the steering body.

[0023] In the touch detection device according to the third aspect, the sensor electrodes are arranged in pairs on the left and right in the vehicle width direction on the steering body. Thereby, it is possible to accurately determine whether the occupant is gripping the steering body with both hands or with one hand.

[0024] In the touch detection device according to the fourth aspect, the correction unit sets a correction value for correcting the capacitance of each sensor electrode by using the absolute value of the difference value for each sensor electrode. The change in capacitance due to the change in parasitic capacitance is less than the change in capacitance due to the contact state of the occupant with the steering body. From this, for example, by using a difference value with a small absolute value among a plurality of difference values, it is possible to suppress the capacitance from being corrected too large.

[0025] In the touch detection device according to the fifth aspect, the temperature detection unit detects a change in the ambient temperature of the steering body, and the correction unit sets a correction value from each of the difference values and the change in the ambient temperature. Since the parasitic capacitance in the sensor electrode changes according to the temperature, by using the change in the ambient temperature for setting the correction value, it becomes possible to set a more appropriate correction value.

[0026] In the touch detection device according to the sixth aspect, the reference value setting unit sets an initial value of the reference value of the capacitance for each sensor electrode from the capacitance for each sensor electrode in a state where no occupant is in contact with the steering body, and updates and sets each of the reference values by using the correction value. The correction unit corrects the capacitance of each sensor electrode by using the reference value updated and set for each sensor electrode.

[0027] Here, the reference value is mainly the capacitance corresponding to the parasitic capacitance. By correcting and updating this reference value from the initial value with the correction value, the capacitance of each sensor electrode is corrected using the corrected (updated) reference value for each sensor electrode. Thereby, it is possible to accurately determine the contact state (touch detection) using the corrected capacitance.

[0028] In the touch detection device according to the seventh aspect, it is evaluated whether the correction value is less than a preset threshold value. When 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, it is possible to suppress the capacitance of each sensor electrode from being corrected too much.

[0029] In the touch detection device according to the eighth aspect, heating means for heating the steering body by operating in the base body is provided in the steering body. Therefore, when the heating means operates, the parasitic capacitance of each sensor electrode increases and the change in capacitance increases, but since the detected capacitance can be corrected according to the change in capacitance, it is possible to suppress a decrease in the accuracy of determining the contact state (touch detection).

[0030] In the touch detection device according to the ninth aspect, the threshold value is changed according to the operating state of the heating means. Also, in the touch detection device according to the tenth aspect, the threshold value when the heating means is operating is set higher than the threshold value when the heating means is not operating. Thereby, when the heating means is operating, the correction value can be increased, so that the capacitance of each sensor electrode can be appropriately corrected.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiment for Carrying Out the Invention

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The touch detection device 10 according to the present embodiment is provided in the steering device 12 of a vehicle and detects whether or not an occupant is gripping the steering wheel 14 of the steering device 12.

[0033] In FIG. 1, the schematic configuration of the touch detection device 10 is shown in a block diagram. Further, in FIG. 2, the schematic of the steering wheel 14 of the steering device 12 is shown in a front view as seen from the occupant, and in FIG. 3, the schematic configuration of the main part of the steering wheel 14 is shown in a cross-sectional view in the radial direction. In the drawings, the right side in the vehicle width direction is indicated by the arrow HR, and the upper side is indicated by the arrow UP.

[0034] The steering device 12 functions as an operating device operated by an occupant (driver) in a vehicle. Further, the steering wheel 14 is provided on the steering device 12. The steering wheel 14 is disposed on the front side of the vehicle of the seat (driver's seat, not shown) where the occupant (driver) who operates the vehicle is seated, and the steering wheel 14 functions as an operating body and a steering body operated by the occupant.

[0035] As shown in FIG. 2, the steering wheel 14 includes a substantially annular rim portion 16 as a gripping 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 drawings, the radial direction of the steering wheel 14 is indicated by the arrow R.

[0036] The steering wheel 14 includes a metal core part as a core part constituting the skeleton. The core part is composed of a substantially annular rim core part 24 (see FIG. 3) of the rim part 16, a boss core part (not shown) of the boss part 18, and a stay core part (not shown) of the stay part 20. In the steering wheel 14, the boss core part and the rim core part 24 are connected by the stay core part, and the rim part 16, the boss part 18, and the stay part 20 are integrated.

[0037] The steering device 12 includes a steering shaft (not shown). The steering shaft is rotatably supported by the vehicle body with its axial direction being substantially the longitudinal direction of the vehicle on the front side of the driver's seat in the vehicle. The steering wheel 14 has the boss core part of the boss part 18 fixed to the rear end of the steering shaft in the vehicle. The steering wheel 14 is integrally rotatable with the steering shaft and supported by the vehicle body, and the core part is grounded to the vehicle body via the steering shaft.

[0038] In the 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. Note that FIG. 2 shows the steering wheel 14 in a straight-ahead state of the vehicle.

[0039] As shown in FIG. 3, a base 22 made of a resin material such as urethane as an insulating material is disposed on the rim part 16 of the steering wheel 14. The base 22 covers the rim core part 24 of the rim part 16, and the rim core part 24 is accommodated in the base 22 by insert molding. Note that FIG. 3 schematically shows a state in which a cross section along the circumferential direction of the main part of the rim part 16 is developed.

[0040] The steering wheel 14 has a decorative portion 26 as a contact portion (skin) disposed on the radially outer side of the base body 22. The decorative portion 26 is made of leather or resin (partially may be made of wood) and has insulating properties. The rim portion 16 of the steering wheel 14 is covered by the decorative portion 26 over the entire circumference in the radial cross-section of the base body 22 of the steering wheel 14 and over the entire circumference (the entire area) in the circumferential direction of the steering wheel 14.

[0041] Also, in the steering device 12, a heater (electric heater) 30 can be installed as heating means (warming means) on the steering wheel 14. Note that in FIGS. 1 and 2, a part of the heater 30 is shown.

[0042] For the heater 30, an electric heating wire or the like is used, which surrounds substantially the entire outer peripheral surface of the base body 22 within the rim portion 16 and is installed in a required range (for example, substantially the entire circumference) in the circumferential direction of the outer peripheral surface of the base body 22 of the steering wheel 14. The heater 30 is attached to a support sheet 32 that functions as a base body using an insulating material and a foamed urethane as a support member. The support sheet 32 is provided on the radially outer side of the rim portion 16 and is attached to the outer peripheral surface of the base body 22.

[0043] On the other hand, the touch detection device 10 is of a capacitance type (self-capacitance type), and the touch detection device 10 includes a sensor portion 40 for detecting the proximity of an occupant and a controller 42. Also, the touch detection device 10 is provided with a temperature sensor 44 as temperature detection means for detecting the ambient temperature.

[0044] The sensor portion 40 includes a sensor electrode 46 and a sensor sheet 48 as a support. The sensor electrode 46 and the sensor sheet 48 are each in the form of a long sheet (film-like). In the sensor portion 40, a conductive member is used for the sensor electrode 46, and a resin material as an insulating material (dielectric) is used for the sensor sheet 48.

[0045] The sensor unit 40 has a layer structure in which sensor electrodes 46 are arranged on one surface of the sensor sheet 48 and no shield electrode is provided. The sensor unit 40 is disposed outside the base body 22 with the sensor electrodes 46 on the side of the decorative portion 26 (the sensor sheet 48 on the side of the base body 22) in the rim portion 16. Further, the sensor unit 40 is arranged over substantially the entire circumference (substantially the entire region in the circumferential direction of the cross section of the rim portion 16) of the outer circumference of the base body 22 within a predetermined range in the circumferential direction of the steering wheel 14.

[0046] As a result, when the 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 approaches the sensor electrodes 46 of the sensor unit 40. When a heater 30 is arranged in the rim portion 16, the sensor unit 40 is arranged outside the support sheet 32 of the heater 30 (between the support sheet 32 and the decorative portion 26). Further, in the steering wheel 14, when the heater 30 is installed, the base body 22 is made thinner (the radial dimension is smaller) by the thickness of the heater 30 and the support sheet 32.

[0047] As shown in FIGS. 1 and 2, two sensor units 40 (40L, 40R) are used in the touch detection device 10. The sensor unit 40L is arranged in a range of 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 is arranged in a range of approximately half the circumference on the right side in the vehicle width direction. As a result, when the occupant grips the steering wheel 14 (rim portion 16), the occupant's left hand approaches the sensor unit 40L and the occupant's right hand approaches the sensor unit 40R. In the sensor unit 40, when the occupant comes into contact with the rim portion 16, a capacitance is generated between the sensor electrodes 46 and the occupant.

[0048] In the touch detection device 10, the sensor units 40L and 40R have substantially the same configuration. Hereinafter, when the sensor units 40L and 40R are not distinguished, 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 ambient temperature). In the touch detection device 10, the controller 42 is disposed near the steering wheel 14, and in the touch detection device 10, the temperature sensor 44 is disposed inside the controller 42. Not limited to this, the temperature sensor 44 may be disposed inside the rim portion 16 to directly detect the temperature of the base body 22 or the like.

[0049] 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 each electrically connected to the controller 42.

[0050] Further, when the heater 30 is installed in the steering wheel 14, the steering device 12 includes a heater control unit 34 that controls the operation of the heater 30. The heater 30 and the controller 42 are connected to the heater control unit 34. When a heater switch (not shown) is turned on, the heater control unit 34 energizes the heater 30 and outputs a heater-on signal to the controller 42. Further, when the heater switch is turned off, the heater control unit 34 stops the energization of the heater 30 and outputs a heater-off signal to the controller 42.

[0051] In the steering device 12, when the heater 30 is energized, the rim portion 16 of the steering wheel 14 is heated to a predetermined temperature, preventing a passenger who touches the rim portion 16 from feeling cold. Note that the heater control unit 34 may stop the energization of the heater 30 and output a heater-off signal to the controller 42 when a predetermined time has elapsed after the heater 30 is energized (after it is turned on).

[0052] The controller 42 includes a microcomputer with a CPU, ROM, RAM, and non-volatile storage connected by a bus, along with required functional circuits (all not shown). In the controller 42, the CPU reads and executes a touch detection program and the like stored in the ROM and storage, thereby realizing a touch detection function using the required functional circuits. Note that a field programmable gate array (FPGA), a programmable logic array (PLA), or the like may be used for the controller 42.

[0053] In the controller 42, a detection unit 50, a capacitance correction unit 52 that constitutes a correction unit, and a determination unit 54 are formed. Further, in the controller 42, a filter unit 56, a difference value generation unit 58, a comparison unit 60, a reference value setting unit 62, and a temperature filter unit 64 that constitute a correction unit are formed.

[0054] Note that the detection unit 50, the capacitance correction unit 52, the filter unit 56, and the difference value generation unit 58 include a detection unit 50L, a capacitance correction unit 52L, a filter unit 56L, and a difference value generation unit 58 for the sensor unit 40L, and a detection unit 50R, a capacitance correction unit 52R, a filter unit 56R, and a difference value generation unit 58 for the sensor unit 40R. The detection unit 50L and the detection unit 50R, the capacitance correction unit 52L and the capacitance correction unit 52R, the filter unit 56L and the filter unit 56R, and the difference value generation unit 58L and the difference value generation unit 58R have the same basic configuration. For this reason, hereinafter, when not distinguishing between the sensor unit 40L and the sensor unit 40R, the detection unit 50, the capacitance correction unit 52, the filter unit 56, and the difference value generation unit 58 will be described.

[0055] In the sensor electrode 46 disposed on the rim portion 16, when a passenger contacts the rim portion 16, a capacitance is generated between the passenger and the sensor electrode 46. In addition, parasitic capacitance may occur between the sensor electrode 46 and the rim core metal portion 24 or the like. This parasitic capacitance changes according to the dielectric constant of the insulating material used for the base body 22 (and the support sheet 32) and the like, and the dielectric constant of the base body 22 and the like changes according to the temperature of the base body 22 (and the support sheet 32) and the like.

[0056] The detection unit 50L is connected to the sensor electrode 46 of the sensor unit 40L, and the detection unit 50R is also connected to the sensor electrode 46 of the sensor unit 40L. 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 according to the capacitance, and outputs the capacitance (capacitance value) C(t) generated in the sensor electrode 46 at each time t from the detected potential. As a result, the detection unit 50L outputs the capacitance C L (t) generated in the sensor unit 40L, and the detection unit 50R outputs the capacitance C R (t) generated in the sensor unit 40R.

[0057] The capacitance correction unit 52 (52L, 52R) performs temperature correction on the capacitance C L (t), C R (t) using the reference values (capacitance values) C BASE_L (t), C BASE_R (t) set by the reference value setting unit 62. As a result, the capacitance correction unit 52L outputs the capacitance C touch_L (t) for determining touch detection on the sensor unit 40L, and the capacitance correction unit 52R outputs the capacitance C touch_R (t) for determining touch detection on the sensor unit 40R.

[0058] The determination unit 54 uses a preset threshold Th judge for touch determination (state determination) to determine whether an occupant is in contact with the sensor units 40L and 40R from the capacitances C touch_L (t), C touch_R (t). This threshold Th judge is a value (capacitance value) set according to the change in capacitance that occurs when an occupant approaches the sensor electrode 46.

[0059] The determination unit 54 outputs a state signal G(t) indicating the gripping state (touch state including whether touching or not) of the occupant on the steering wheel 14 based on the determination result.

[0060] On the other hand, the filter unit 56 (56L, 56R), difference value generation unit 58 (58L, 58R), comparison unit 60, and reference value setting unit 62 that constitute the temperature correction unit start operating when the determination unit 54 detects that the occupant is gripping (touching) the steering wheel 14 (a state signal G(t) indicating gripping is output).

[0061] In addition, when it is detected that the occupant is gripping (single-handed) the steering wheel 14 with only the left hand or the right hand, the filter unit 56 and the difference value generation unit 58 on the side where gripping is not detected may have their processing stopped. For example, when the occupant is gripping the steering wheel 14 with the right hand (when touch detection is not performed on the sensor unit 40L side), the filter unit 56R and the difference value generation unit 58R may start processing, and the filter unit 56L and the difference value generation unit 58L may have their processing stopped.

[0062] The filter unit 56 (56L, 56R) performs noise component removal processing on the capacitances C L (t), C R (t). In the filter unit 56, as noise component removal processing, for example, a moving average process of averaging using n capacitances C R , C L is performed. As a result, the filter unit 56L outputs the filtered capacitance C L (t), and the filter unit 56R outputs the filtered capacitance C R (t). Note that the noise removal processing (filter processing) is not limited to the moving average, and as long as a smoothly changing (noise component suppressed) capacitance C L (t), C R (t) can be obtained, it is not limited to this.

[0063] The difference value generation unit 58 (58L, 58R) calculates the difference between the capacitances C L (t), C R after the current filter processing and the capacitances C L (t - 1), C R (t - 1) after the previous filter processing, and calculates the difference value (capacitance value) ΔC L (t), ΔCR Output (t). That is, the difference value generation 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)) to the comparison unit 60.

[0064] The temperature sensor 44 is connected to the temperature filter unit 64. The temperature filter unit 64 acquires the temperature T as temperature information from the temperature sensor 44 at a predetermined time interval, and performs a predetermined filter process to output the filtered temperature T(t) to the comparison unit 60. In the filter process in the temperature filter unit 64, for example, the temperature T(t) averaged using the moving average of the temperature T for n times is acquired. 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 a configuration can obtain a smoothly changing (noise component suppressed) temperature T(t).

[0065] The comparison unit 60 sets the correction value ΔC(t) by performing a comparison process of comparing the difference value ΔC L (t) and the difference value ΔC R (t). In the comparison process, the absolute value |ΔC L (t)| of the difference value ΔC L (t) and the absolute value |ΔC R (t)| of the difference value ΔC R (t) are compared. At this time, the change in capacitance in the sensor unit 40 is considered to be a change caused by the temperature T and a change caused by the movement of the occupant. The change caused by the movement of the occupant is larger than the change caused by the temperature T.

[0066] From here, in the comparison unit 60, the smaller difference value ΔC L (t) or |ΔC R (t)| (either ΔC L (t) or ΔC R (t)) among |ΔC

[0067] Further, in the comparison unit 60, the difference values ΔC L (t), ΔC R (t) are determined for their signs, and it is determined whether the temperature T(t) is on an upward trend or a downward trend.

[0068] At this time, in the comparison unit 60, when both of the difference values ΔC L (t), ΔC R (t) have signs of “+” (positive, plus), and when both have signs of “-” (negative, minus), the smaller of the absolute values |ΔC L (t)|, |ΔC R (t)| of the candidate difference values ΔC L (t) (or ΔC R (t)) is set as the correction value ΔC(t).

[0069] Further, in the comparison unit 60, when one of the difference values ΔC L (t), ΔC R (t) has a sign of “+” and the other has a sign of “-” (negative, minus), the temperature T(t) (the change trend of the temperature T(t)) is used for setting the correction value ΔC(t). At this time, in the comparison unit 60, when the temperature T(t) is on an upward trend (when the temperature T(t) is higher than the previous temperature T(T(t - 1))), the difference value ΔC L (t) with a sign of “+” among the absolute values |ΔC R (t)|, |ΔC L (t)| (or ΔC R (t)) is set as the correction value ΔC(t).

[0070] On the contrary, 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) with a sign of “-” among the difference values ΔC R (t), ΔC L (t) (or ΔC R (t)) is set as the correction value ΔC(t).

[0071] Furthermore, when the heater 30 is installed in the steering wheel 14, the temperature T(t) may not fully reflect the temperature of the base body 22 (the steering wheel 14). From this, the comparison unit 60 acquires a signal indicating the on / off state of the heater 30 from the heater control unit 34. In the comparison unit 60, when the heater 30 is turned on and one of the signs of the difference values ΔC L (t), ΔC R (t) is "+", and the other sign is "-" (negative, minus), the difference value ΔC L (t), ΔC R (t) with the sign of "+" is set as the correction value ΔC(t). L (or ΔC R (t)).

[0072] The correction value ΔC(t) set in the comparison unit 60 inherits the sign of the value (capacitance value) of the original difference value ΔC L (t) or the difference value ΔC R (t). Note that in the comparison unit 60, when one of the signs of the difference values ΔC L (t), ΔC R (t) is "+", and the other sign is "-" (negative, minus), and it is determined that there is no change in the temperature T(t) (when neither an upward trend nor a downward trend is determined), the correction value ΔC(t) is set to "0" (ΔC(t) = 0) because the correction direction cannot be properly determined.

[0073] On the other hand, in the reference value setting unit 62, reference values C BASE_L (t), reference values C BASE_R (t) are set as initial values (capacitance values) for the sensor units 40L, 40R. The initial values of the reference values C BASE_L (t), reference values C BASE_R (t) are, for example, the capacitances C L (t), C R (t) detected from the sensor units 40L, 40R when an ignition switch (not shown) of the vehicle is turned on and the touch detection device 10 starts to operate. That is, the reference values C BASE_L (t), reference values C BASE_R(t) is applied with the capacitance (mainly the capacitance caused by parasitic capacitance) in a state where the occupant is not touching the sensor units 40L and 40R.

[0074] Also, when the heater 30 is installed on the steering wheel 14, a signal indicating the on / off state of the heater 30 is input from the heater control unit 34 to the reference value setting unit 62.

[0075] Furthermore, the reference value setting unit 62 uses the correction value ΔC(t) to determine whether to correct the reference values C BASE_L (t), C BASE_R (t). A threshold Th BASE is set for this purpose, and the reference value setting unit 62 evaluates the correction value ΔC(t) using the threshold Th BASE . It is preferable that a plurality of values (capacitance values) corresponding to changes in the temperature T(t), the on / off state of the heater 30, etc. are set for the threshold Th BASE .

[0076] The conditions for changing the threshold Th BASE include changes in the temperature T(t), the state of the heater 30 (on or off), changes in the detected capacitance (capacitances C L (t), C R (t)), and changes in the difference values (difference values ΔC L (t), ΔC R (t)), etc. An example of the threshold Th BASE based on these conditions is shown in FIG. 4.

[0077] As shown in FIG. 4, the temperature T(t) is divided into three stages: rising (rising trend), no change, or falling (falling trend). Also, the state of the heater 30 is divided into two stages: on (ON) or off (OFF). Furthermore, the capacitance detected by the sensor unit 40 is divided into two stages: increasing (increasing trend) or decreasing (decreasing trend).

[0078] From this, as the threshold Th BASE , Th BASE1from Th BASE12 can be divided into 12 steps. Also, when the heater 30 is not installed, since the heater state is limited to off, the threshold Th BASE can be set in 6 steps. These thresholds Th BASE can be set by predicting the change amount of the parasitic capacitance in advance according to each condition, or measuring the change amount of the parasitic capacitance according to the condition and applying the value set based on the prediction result or the measurement result. Note that the number of thresholds Th BASE (the number of steps of the threshold Th BASE ) is not limited to these.

[0079] Here, as an example, in the touch detection device 10, when the heater 30 is installed on the steering wheel 14, the threshold Th BASE is set excluding the condition of the temperature T(t) and the change in the capacitance of the sensor unit 40. Thereby, in the reference value setting unit 62, the threshold Th BASE applied when the heater 30 is on and the threshold Th BASE_H applied when the heater 30 is off are set. At this time, since the change in the capacitance caused by the parasitic capacitance is large when the heater 30 is turned on, in the reference value setting unit 62, the threshold Th BASE_L applied when the heater 30 is on is set to a value larger than the value Th BASE_H applied when the heater 30 is off (Th BASE_L > Th BASE_H > Th BASE_L ).

[0080] In the reference value setting unit 62, when comparing the correction value ΔC(t) with the threshold Th BASE in the evaluation, the absolute value |ΔC(t)| of the correction value ΔC(t) is applied. In the reference value setting unit 62, when the absolute value |ΔC(t)| is less than the threshold Th BASE (|ΔC(t)| < Th BASE ), it is evaluated that the correction value ΔC(t) corresponds to the change in the parasitic capacitance caused by the change in the temperature T and it is preferable to perform correction. Thereby, in the reference value setting unit 62, the reference values C BASE_L (t), C BASE_RSet it to correct (t).

[0081] At this time, in the reference value setting unit 62, when the heater 30 is on, the threshold value Th BASE is used as the threshold value Th BASE_H and when the heater 30 is off, the threshold value Th BASE is used as the threshold value Th BASE_L In the reference value setting unit 62, when the heater 30 is turned on and the threshold value Th BASE is used as the threshold value Th BASE_H when the heater 30 is turned off, the threshold value Th BASE is changed (returned) from the threshold value Th BASE_H to the threshold value Th BASE_L .

[0082] Also, since the temperature of the heater 30 is controlled by the heater control unit 34, in the reference value setting unit 62, when the threshold value Th BASE is set as the threshold value Th BASE_H after the heater 30 is turned on and a preset time has elapsed, the threshold value Th BASE is changed to the threshold value Th BASE_L . As this time, for example, the time when the temperature rise stops, such as the time when the steering wheel 14 reaches a predetermined temperature (the control temperature of the heater 30), can be applied.

[0083] In the reference value setting unit 62, when it is set to correct the reference values C BASE_L (t), C BASE_R (t) using the correction value ΔC(t), the reference values C BASE_L (t), C BASE_R (t) are updated. That is, the reference value setting unit 62 executes the following arithmetic processing. C BASE_L (t)=C BASE_L (t - 1)+ΔC(t) C BASE_R (t)=C BASE_R (t - 1)+ΔC(t)

[0084] Thereby, the reference values C BASE_L (t), CBASE_R (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). When the correction using the correction value ΔC(t) is not performed, the reference value C BASE_L (t), C BASE_R (t) is respectively 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)).

[0085] The capacitance correction unit 52 (52L, 52R) subtracts the reference value C L (t), C R (t) corresponding to the parasitic capacitance from the capacitance C BASE_L (t), C BASE_R (t) to calculate the capacitance C touch_L (t), C touch_R (t) used for touch determination. That is, the capacitance correction unit 52L calculates and outputs the capacitance C touch_L (t) (= C L (t) - C BASE_L (t)), and the capacitance correction unit 52R calculates and outputs the capacitance C touch_R (t) (= C R (t) - C BASE_R (t)).

[0086] Thereby, in the determination unit 54, the capacitance C L (t), C R (t) obtained by temperature - correcting the capacitance C touch_L (t), C touch_R (t) is used to determine whether the steering wheel 14 is being held by the occupant or not.

[0087] Next, as the operation of the present embodiment, the operation of the touch detection device 10 will be described. In the touch detection device 10, when the ignition switch of the vehicle is turned on, the controller 42 starts operating, and the detection units 50L, 50R respectively detect the capacitance C of the sensor units 40L, 40RL (t), C R Start detecting (t) and output the detected capacitance C(t). L (t), C R Start outputting (t).

[0088] When the operation is started in the controller 42, the reference value setting unit 62 sets the initial value of the reference value C(t) based on the capacitance C(t) detected by the sensor unit 40L, and sets the initial value of the reference value C(t) based on the capacitance C(t) detected by the sensor unit 40R. At this time, since the occupant is not gripping (touching) the steering wheel 14, the capacitances C(t), C(t) detected by the sensor units 40L and 40R are mainly capacitances caused by parasitic capacitances (capacitances not affected by the occupant). Therefore, the reference value setting unit 62 can set the capacitances C(t), C(t) mainly caused by parasitic capacitances as the initial values of the reference value C(t), C(t). L (t) based on the reference value C BASE_L (t) initial value, and the capacitance C R (t) based on the reference value C BASE_R (t) initial value. At this time, since the occupant is not gripping (touching) the steering wheel 14, the capacitances C L (t), C R (t) are mainly capacitances caused by parasitic capacitances (capacitances not affected by the occupant). Therefore, in the reference value setting unit 62, the capacitances C L (t), C R (t) as the reference value C BASE_L (t)C BASE_R (t) initial value can be set.

[0089] Also, when the operation is started in the controller 42, the temperature filter unit 64 starts operating. As a result, the temperature filter unit 64 starts outputting the moving average of the temperature T detected by the temperature sensor 44 (the moving average for n times), which is the temperature T(t).

[0090] After the touch detection device 10 starts operating, when the occupant grips the steering wheel 14 with both hands for vehicle steering, the hands of the occupant approach the sensor units 40L and 40R, and the capacitances C(t), C(t) increase. As a result, each of the capacitances C(t), C(t) output from the capacitance correction units 52L and 52R exceeds the threshold Th (C(t)>Th, C L (t), C R (t) increases. As a result, each of the capacitances C touch_L (t), C touch_R (t) exceeds the threshold Th judge (C touch_L (t)>Th judge , C touch_R(t) > Th judge ) and the determination unit 54 determines that the gripping with both hands has started. This determination result is output as a state signal G(t) from the determination unit 54.

[0091] When the controller 42 detects that the occupant has started gripping the steering wheel 14, the temperature correction unit starts operating. As a result, the filter units 56L and 56R respectively perform filter processing on the capacitance C L (t) detected by the sensor unit 40L and the capacitance C R (t) detected by the sensor unit 40R. The filter units 56L and 56R output the capacitances C L (t) and C R (t) that have been filter-processed to the difference value generation units 58L and 58R.

[0092] The difference value generation unit 58L calculates and outputs a difference value ΔC L (t) indicating the change in the filter-processed capacitance C L (t) (= C L (t) - C L (t - 1)). Also, the difference value generation unit 58R calculates and outputs a difference value ΔC R (t) indicating the change in the filter-processed capacitance C R (t) (= C R (t) - C R (t - 1)).

[0093] Here, the comparison unit 60 compares the difference value ΔC L (t) with the difference value ΔC R (t), and sets correction values ΔC(t) for the reference values C BASE_L (t) and C BASE_R (t) according to this comparison result. Also, in setting the correction value ΔC(t), the comparison unit 60 uses the filter-processed temperature T(t) as necessary. The comparison unit 60 calculates the absolute values |ΔC L (t)| of the difference value ΔC L (t) and the difference value ΔC L (t), and the absolute values |ΔC R (t)| of the difference value ΔC R (t)R Using (t) and temperature T(t), a correction value ΔC(t) is set.

[0094] At this time, in the comparison unit 60, for the difference values ΔC L (t), ΔC R (t), when both signs are either “+” or “-” (when they have the same sign), the smaller of the absolute values |ΔC L (t)|, |ΔC R (t)| of the difference values ΔC L (t) (or difference value ΔC R (t)) is set as the correction value ΔC(t).

[0095] Also, in the comparison unit 60, when one sign of the difference values ΔC L (t), ΔC R (t) is “+” and the other is “-”, the change tendency of the temperature T(t) is used. In this case, if the temperature T(t) is on an upward trend, the comparison unit 60 sets the difference value ΔC L (t), ΔC R (t) with the sign “+” (or difference value ΔC L (t)) as the correction value ΔC(t). Also, when the temperature T(t) is on a downward trend, the comparison unit 60 sets the difference value ΔC R (t) with the sign “-” among the difference values ΔC L (t), ΔC R (t) (or difference value ΔC L (t)) as the correction value ΔC(t). R (t)) as the correction value ΔC(t).

[0096] In the touch detection device 10, as an example, the temperature sensor 44 detects the ambient temperature around the steering wheel 14, and the temperature sensor 44 may not be able to detect the temperature of the base body 22 or the like. For this reason, even when the heater 30 is turned on and the temperature of the base body 22 of the steering wheel 14 or the like has increased, it may not be reflected in the temperature T(t).

[0097] From here, in the touch detection device 10, if the heater 30 is on, it may be estimated that the temperature T(t) is on an upward trend. Thereby, in the touch detection device 10, the difference value ΔC L (t), ΔC R (t), when one sign is "+", the other sign is "-", and the heater 30 is on, the difference value ΔC L (t), ΔC R (t), the difference value ΔC L (t) with the sign of "+" (or the difference value ΔC R (t)) is set as the correction value ΔC(t).

[0098] When the correction value ΔC(t) is set in this way, in the reference value setting unit 62, the reference values C BASE_L (t), C BASE_R (t) are corrected using the correction value ΔC(t). At this time, in the reference value setting unit 62, a threshold value Th BASE is set according to whether the heater 30 is on / off, etc., and using this threshold value Th BASE , the suitability (necessity of correction) of the correction value ΔC(t) is determined (the correction value ΔC(t) is evaluated).

[0099] At this time, when the absolute value |ΔC(t)| of the correction value ΔC(t) is less than the threshold value Th BASE (|ΔC(t)| < Th BASE ), assuming that the correction value ΔC(t) is mainly the change in parasitic capacitance, the reference values C BASE_L (t), C BASE_R (t) are corrected using the correction value ΔC(t). Thereby, the reference values C BASE_L (t) (= C BASE_L (t - 1) + ΔC(t)) corresponding to the parasitic capacitance according to the temperature, and the reference value C BASE_R (t) (= C BASE_R (t - 1) + ΔC(t)) are obtained.

[0100] The capacitance correction unit 52L uses the capacitance C L (t) detected from the sensor unit 40L by the detection unit 50L and the reference value C BASE_L (t), and from the capacitance C L (t) to the reference value CBASE_L Capacitance C subtracted by (t) touch_L Calculate (t) (C touch_L (t) = C L (t) - C BASE_L (t)). Further, the capacitance correction unit 52R calculates the capacitance C subtracted by the reference value C from the capacitance C detected from the sensor unit 40R in the detection unit 50R R (t) and the reference value C BASE_R (t), and uses the capacitance C R (t) to calculate the capacitance C subtracted by the reference value C from the capacitance C BASE_R (t) touch_R (t) (C touch_R (t) = C R (t) - C BASE_R (t)).

[0101] In the determination unit 54, it is determined whether the left side (the driver's left hand) of the steering wheel 14 is being gripped using the capacitance C touch_L (t) and the threshold value Th judge , and it is determined whether the right side (the driver's right hand) of the steering wheel 14 is being gripped using the capacitance C touch_R (t) and the threshold value Th judge . At this time, if the capacitance C touch_L (t) is greater than the threshold value Th judge (C touch_L (t) > Th judge ), the determination unit 54 determines that the left side (the sensor unit 40L part) of the steering wheel 14 is being gripped. Also, if the capacitance C touch_R (t) is greater than the threshold value Th judge (C touch_R (t) > Th judge ), the determination unit 54 determines that the right side (the sensor unit 40R part) of the steering wheel 14 is being gripped.

[0102] Here, in FIG. 5, the approximate changes in the temperature T(t), the capacitance C L (t), the capacitance C R (t), and the reference value C BASE (t) with respect to time t are shown in a diagram. Note that in FIG. 5(A), the change in the temperature T(t) with respect to time t is shown, and in FIG. 5(B), the capacitance C with respect to time tL (t) and capacitance C R The change of (t) is shown, and in FIG. 5(C), the reference value C with respect to time t BASE The change of (t) is shown. Also, in FIG. 5(C), the reference value C BASE_L (t) and the reference value C BASE_R (t) are regarded as the same, and shown as the reference value C BASE (t).

[0103] As shown in FIG. 5(A), the temperature T(t) gradually rises in response to the change of time t, but is assumed to turn downward at time t3. In the drawing, times t1, t2, t3 are such that t1 < t2 < t3.

[0104] Also, as shown in FIG. 5(B), the capacitance C L (t) increases until it reaches time t3, turns to decrease when it reaches time t3, and further changes (increases) the degree of increase at time t2. Also, the capacitance C R (t) gradually decreases from time t1 until it reaches time t2, turns to rise after passing time t2, and turns to decrease after further passing time t3.

[0105] Here, until time t2, the difference value ΔC L (t) of the capacitance C L (t) becomes "+", and the difference value ΔC R (t) of the capacitance C R (t) becomes "-". At this time, due to the increase of the temperature T(t), the difference value ΔC L (t) of the capacitance C L (t) is set to the correction value ΔC(t). Thereby, as shown in FIG. 5(C), the reference value C BASE (t) changes to increase in the same manner as the capacitance C L (t) until it reaches time t2.

[0106] Also, between time t2 and time t3, the difference value ΔC L (t) of the capacitance C L (t), and the capacitance CR The difference value ΔC of (t) R (t) is all "+", and at this time, the capacitance C L With respect to the change in (t), the capacitance C R Due to the small change in (t), the absolute value |ΔC R (t)| is smaller than the absolute value |ΔC L (t)| (|ΔC L (t)| > |ΔC R (t)|). Thus, the reference value C BASE (t) changes so as to increase in the same manner as the capacitance C R (t) between time t2 and time t3.

[0107] Furthermore, when the temperature T(t) turns to decrease after time t3, the capacitance C L The difference value ΔC of (t) L (t), and the capacitance C R The difference value ΔC of (t) R (t) are all "-". Also, with respect to the change in the capacitance C L (t), due to the small change in the capacitance C R (t), the absolute value |ΔC R (t)| is smaller than the absolute value |ΔC L (t)| (|ΔC L (t)| > |ΔC R (t)|). Thus, the reference value C BASE (t) changes so as to decrease in the same manner as the capacitance C R (t) after time t3.

[0108] In this way, in the touch detection device 10, the detection units 50L and 50R detect the capacitances C L (t), C R (t) by the sensor units 40L and 40R, and the determination unit 54 performs touch detection (touch determination, determination of the gripping state), thereby determining the contact state of the occupant with the steering wheel 14. Also, in the sensor units 40L and 40R, no electrical shielding means such as a shield electrode is provided between the sensor electrode 46 and the rim core metal part 24.

[0109] Here, in the controller 42, the differential value generation units 58L and 58R perform filter processing on the capacitance C L (t), C R (t), and generate the differential value ΔC L (t) of the change in C R (t), ΔC L (t). Using the generated differential values ΔC R (t), ΔC L (t), the capacitances C R (t) detected by the detection units 50L and 50R are corrected.

[0110] As a result, in the touch detection device 10, even if the parasitic capacitance or the like changes at each of the sensor electrodes 46 and the capacitance C L (t), C R (t) changes, touch determination can be performed using the capacitances C touch_L (t), C touch_R (t) in which the change caused by the parasitic capacitance is suppressed.

[0111] Also, 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. As a result, the touch detection device 10 can accurately detect whether the occupant is gripping the steering wheel 14 with both hands, one hand, or not gripping it at all.

[0112] Also, in the touch detection device 10, the comparison unit 60 sets the correction value ΔC(t) using the absolute values |ΔC L (t)|, |ΔC R (t)| of the differential values ΔC L (t), ΔC R (t) of the capacitances C L (t), C R (t) after filter processing. At this time, for the correction value ΔC(t), the differential value ΔC L (t) (or the differential value ΔC R (t)) of the smaller value among |ΔC L (t)|, |ΔC R (t)| can be applied.

[0113] As a result, a capacitance C touch_L (t), C touch_R (t) corresponding to a parasitic capacitance smaller than the capacitance caused by the movement of the occupant is obtained, so that the capacitance C touch_L (t), C touch_R (t) is not corrected to be larger than necessary. Therefore, in the touch detection device 10, it is possible to prevent a decrease in touch determination accuracy due to greatly correcting the capacitance C touch_L (t), C touch_R (t).

[0114] Furthermore, in the touch detection device 10, a correction value ΔC(t) is set based on the temperature T(t). For this reason, in the touch detection device 10, it is possible to obtain a correction value ΔC(t) that appropriately corresponds to the parasitic capacitance that changes according to the temperature T(t).

[0115] Also, in the touch detection device 10, the capacitances C L (t), C R (t) when the occupant is not in contact are used as initial values, and reference values C BASE_L (t), C BASE_R (t) updated using the correction value ΔC(t) are used. As a result, in the touch detection device 10, it is possible to use the capacitances C L (t), C R (t) obtained by removing the capacitance corresponding to the parasitic capacitance from the capacitances C touch_L (t), Ct ouch_R (t) in touch determination, and thus touch determination can be performed with high accuracy.

[0116] Also, in the touch detection device 10, the correction value ΔC(t) is evaluated using a threshold Th BASE , and when the correction value ΔC(t) is less than the threshold Th BASE and is evaluated as appropriate, correction using the correction value ΔC(t) is performed. As a result, in the touch detection device 10, it is possible to suppress unnecessary correction such as using a capacitance that has changed due to the movement of the occupant.

[0117] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Furthermore, in the touch detection device 10, when the heater 30 is installed on the steering wheel 14, the threshold Th BASE is set according to the on / off (operating state) of the heater 30. Also, the threshold Th BASE used when the heater 30 is off, Th BASE_L is set to be smaller than the threshold Th BASE_H used when the heater 30 is on. This can suppress the correction including the change in capacitance caused by the operation of the occupant.

[0118] Note that in the above-described embodiment, the correction when gripping the steering wheel 14 with both hands is mainly taken as an example. However, the touch detection device 10 can also be applied when one-handed gripping is detected, for example, when gripping with the right hand is detected (or vice versa).

[0119] In this case, a correction value ΔC(t) is set according to the difference value ΔC L (t) of the capacitance C L (t) and the temperature T(t), and the set correction value ΔC(t) is evaluated using the threshold Th BASE . Thus, when the correction value ΔC(t) is less than the threshold value, the reference values C BASE_L (t), C BASE_R (t) can be corrected and updated using the correction value ΔC(t). This can update not only the reference value C BASE_L (t) but also the reference value C BASE_R (t), enabling a more appropriate determination of the contact state.

[0120] Also, in this embodiment, the sensor unit 40 in which the sensor electrode 46 is arranged on one surface of the sensor seat 48 is used. However, the sensor unit may have a configuration in which the sensor electrode is arranged on the outer peripheral portion of the base body and capacitance is generated between the sensor electrode and an occupant (the hand or finger of the occupant) close to the steering body.

[0121] In addition, in the present embodiment described above, the sensor units 40L and 40R are installed on the steering wheel 14. However, the sensor units (sensor electrodes) may be installed on the steering body at three or more positions. In this case, the difference value of the capacitance detected by each sensor electrode may be obtained, the absolute value of the obtained difference value may be compared, and a correction value may be set based on the comparison result.

[0122] In addition, in the present embodiment, one threshold Th judge is used as the threshold for touch determination (determination of the contact state). However, as the threshold for touch determination, a plurality of thresholds may be set, such as a threshold corresponding to a state where the occupant strongly grips the steering body, a threshold corresponding to a state where the occupant lightly grips the steering body, and a threshold corresponding to a state where the occupant lightly touches the steering body.

[0123] Furthermore, in the present embodiment, the capacitances C L (t) and C R (t) of the sensor units 40L and 40R respectively, the capacitances C touch_L (t) and C touch_R (t) for touch determination are obtained. However, the capacitance for touch determination may be obtained corresponding to the combined capacitance of the capacitances detected at each of the plurality of sensor electrodes. In this case, as the threshold for touch determination, at least a threshold for determining one-handed gripping and a threshold for determining two-handed gripping may be set.

[0124] In addition, in the present embodiment, the substantially annular steering wheel 14 is described as an example. However, the steering body is not limited to a substantially annular shape, and may be a substantially rectangular deformed steering wheel in which each of the grip portions arranged in pairs on the left and right with the boss portion interposed therebetween is connected to the boss portion at one or a plurality of positions, or may be a D shape (flat bottom shape) or the like.

Explanation of Reference Numerals

[0125] 10... Touch detection device, 14... Steering wheel (steering body), 22... Base body, 24... Rim core metal part (core metal part), 30... Heater (heating means), Support sheet (base body), 34... Heater control unit (heating means), 40 (40L, 40R)... Sensor unit, 42... Controller, 44... Temperature sensor (temperature detection unit), 46... Sensor electrode (sensor unit), 50 (50L, 50R)... Detection unit, 52 (52L, 52R)... Capacitance correction unit (correction unit), 54... Determination unit, 58 (58L, 58R)... Difference value generation unit (correction unit), 60... Comparison unit (correction unit), 62... Reference value setting unit (correction unit), 64... Temperature filter unit (temperature detection unit).

Claims

1. A steering body in which a conductive core metal part grounded to the vehicle body is covered with an insulating base body and the vehicle is steered by being contacted and operated by an occupant, a plurality of sensor parts in which a capacitance is generated between a sensor electrode disposed on the outer peripheral part of the base body of the steering body and an 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 by using a difference value indicating a change in the capacitance of each of the sensor electrodes detected by the detection part, a determination part for determining a contact state of an occupant with the steering body based on the corrected capacitance, A touch detection device including the above.

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 is opposed to the core metal part.

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

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

5. including a temperature detection part for detecting a change in the ambient temperature around the steering body, The touch detection device according to claim 4, wherein the correction part sets the correction value from each of the difference values and the change in the ambient temperature.

6. The correction part includes a reference value setting part for setting 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 in a state where no occupant is in contact with the steering body and updating and setting each of the reference values by using the correction value. The correction unit corrects the capacitance for each sensor electrode using the updated reference value for each sensor electrode, the touch detection device according to claim 4 including this.

7. The correction unit evaluates whether or not the correction value is less than a preset threshold value, and when it is evaluated that the correction value is less than the threshold value, corrects the capacitance for each sensor electrode using the correction value, the touch detection device according to claim 4 including this.

8. The touch detection device according to claim 7, including heating means that operates by being provided in the base body in the steering body to heat the steering body.

9. The touch detection device according to claim 8, which cites claim 7, wherein the threshold value is changed according to the operating state of the heating means.

10. The touch detection device according to claim 9, wherein the threshold value is set to be higher when the heating means is operating than when the heating means is not operating.

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