Touch detection device

Abstract

To provide a touch detection device that suppresses the decrease in judgment accuracy caused by parasitic capacity. [Solution] In the touch detection device 10, the switching unit 40 and the detection control unit 42 directly charge the sensor electrodes 34L and 34R respectively to detect their respective capacitances L and R. Then, while directly charging one of the sensor electrodes 34L and 34R, the other is indirectly charged to detect the capacitances Lb and Rb of the directly charged sensor electrodes 34L and 34R. The calculation unit 44 calculates the difference values ​​DLR, DL, and DR from the capacitances L, R, Lb, and Rb, and the determination unit 46 performs a touch determination from the difference values ​​DLR, DL, and DR. As a result, the touch detection device 10 can suppress a decrease in determination accuracy caused by parasitic capacitance occurring in the sensor electrodes 34L and 34R.

Description

Technical Field

[0001] The present invention relates to a touch detection device.

Background Art

[0002] In the steering unit described in Patent Document 1, a contact sensor is arranged on the steering wheel, and based on a preset threshold value and a contact signal output from the contact sensor, contact (grasping) or non-contact (non-grasping) of an occupant with the steering wheel is determined. Further, the steering unit is equipped with a first thermometer that measures the first temperature of the outer surface of the steering wheel and a second thermometer that measures the second temperature as the internal temperature of the steering wheel. Thereby, in the steering unit, the threshold value is changed according to the first temperature and the second temperature, and contact determination is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a capacitive touch sensor for detecting an occupant's contact with a steering wheel, a sensor electrode and a shield electrode are used in an overlapping manner. However, by omitting the shield electrode, cost reduction can be achieved.

[0005] However, the parasitic capacitance changes according to environmental conditions such as temperature. For example, as the environmental temperature rises, the parasitic capacitance also increases. For this reason, accurate touch determination may become difficult.

[0006] This invention was made in view of the above facts, and aims to provide a touch detection device that can reduce costs while suppressing a decrease in judgment accuracy caused by changes in parasitic capacity. [Means for solving the problem]

[0007] To achieve the above objective, the touch detection device according to the first embodiment includes: a first sensor electrode and a second sensor electrode, each positioned on the steering body and accessible to the occupant, and for which capacitance is detected; a detection unit that, when detecting a first capacitance for each of the first and second sensor electrodes, directly charges each of the first and second sensor electrodes for detection, and when detecting a second capacitance for each of the first and second sensor electrodes, directly charges one of the first and second sensor electrodes and indirectly charges the other using the power from the direct charge; a calculation unit that calculates a first difference value which is the difference between the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode, and calculates a second difference value which is the difference between the first capacitance and the second capacitance for each of the first and second sensor electrodes; and a determination unit that uses the first difference value and the second difference value for each of the first and second sensor electrodes to determine whether the occupant is in contact with the first and second sensor electrodes.

[0008] The touch detection device according to the second embodiment includes, in the first embodiment, that the first sensor electrode and the second sensor electrode are two sensor electrodes among a plurality of sensor electrodes arranged on the steering body.

[0009] In the third embodiment, the touch detection device includes, in the first or second embodiment, a first detection unit that supplies power to the first sensor electrode to detect the first capacitance and supplies power to the first sensor electrode and the second sensor electrode to detect the second capacitance, and a second detection unit that supplies power to the second sensor electrode to detect the second capacitance and supplies power to the second sensor electrode and the first sensor electrode to detect the second capacitance.

[0010] In the fourth embodiment, the touch detection device includes, in the third embodiment, a switching unit that switches between supplying power to the first sensor electrode and supplying power to the second sensor electrode together with the first sensor electrode, and switches between supplying power to the second sensor electrode and supplying power to the first sensor electrode together with the second sensor electrode.

[0011] A touch detection device according to the fifth embodiment includes, in the third or fourth embodiment, a first amplification unit that amplifies the charging power supplied to the second sensor electrode when charging the first sensor electrode, and a second amplification unit that amplifies the charging power supplied to the first sensor electrode when charging the second sensor electrode.

[0012] The touch detection device according to the sixth embodiment includes a setting unit that sets a reference value to be used as a basis for a first threshold value for the first difference value and a second threshold value for each of the second difference values, and sets the first threshold value and the second threshold value based on the set reference value, in any one of the first to fifth embodiments.

[0013] In the seventh embodiment, the touch detection device includes, in the sixth embodiment, setting the reference value from the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode when the occupant is not in contact with the first sensor electrode and the second sensor electrode.

[0014] In the eighth embodiment, the touch detection device includes, in the sixth or seventh embodiment, setting the setting unit to set the smaller of the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode as the reference value when the occupant is not in contact with either the first sensor electrode or the second sensor electrode.

[0015] The touch detection device according to the ninth embodiment includes, in any one of the first to eighth embodiments, the determination unit determining whether an occupant has made contact with the first sensor electrode and the second sensor electrode using the first difference value and one of the second difference values ​​of the first sensor electrode and the second sensor electrode, respectively.

[0016] The touch detection device according to the tenth embodiment includes, in any one of the first to ninth embodiments, that each of the second difference values ​​is applied after being accumulated by a predetermined number of the second difference values.

[0017] In the eleventh embodiment of the touch detection device, in any one of the first to tenth embodiments, the determination unit includes a complementation unit that complements the determination result using the second difference value of the first sensor electrode or the second sensor electrode and the first difference value using the first capacitance of the first sensor electrode and the second sensor electrode, respectively.

[0018] In the 12th embodiment, the touch detection device, in the 11th embodiment, includes determining whether the occupant is in contact with both the first and second sensor electrodes based on the first capacitance of each of the first and second sensor electrodes, when it is determined that the occupant is not in contact with at least one of the first and second sensor electrodes. [Effects of the Invention]

[0019] In the touch detection device according to the first embodiment, the first sensor electrode and the second sensor electrode are each positioned on the steering body so that the occupant can touch them, and the capacitance generated at each is detected. When the detection unit detects the first capacitance for each of the first and second sensor electrodes, it directly charges each of the first and second sensor electrodes for detection. Furthermore, when the detection unit detects the second capacitance for each of the first and second sensor electrodes, it directly charges one of the first and second sensor electrodes and indirectly charges the other using the power from the direct charge.

[0020] The calculation unit calculates a first difference value, which is the difference between the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode, and also calculates a second difference value for each of the first and second sensor electrodes, which is the difference between the first capacitance and the second capacitance.

[0021] Here, the determination unit uses the first difference value, the second difference value of the first sensor electrode, and the second difference value of the second sensor electrode to determine whether the occupant is in contact with the first and second sensor electrodes. As a result, the first and second difference values, which are free from the influence of parasitic capacitance in the first and second sensor electrodes, are used, so even when cost reduction is achieved, a decrease in determination accuracy due to changes in parasitic capacitance can be suppressed.

[0022] In the touch detection device according to the second embodiment, the first sensor electrode and the second sensor electrode are two of a plurality of sensor electrodes arranged on the steering body. This makes it possible to determine, for example, whether the occupant is gripping the steering body with at least one hand by arranging them on the left and right sides of the steering body.

[0023] In the touch detection device according to the third aspect, the detection unit includes a first detection unit and a second detection unit. The first detection unit charges the first sensor electrode to detect a first capacitance, and charges the first sensor electrode and the second sensor electrode to detect a second capacitance of the first sensor electrode. Further, the second detection unit charges the second sensor electrode to detect a second capacitance, and charges the second sensor electrode and the first sensor electrode to detect a second capacitance of the second sensor electrode. Thereby, detection of the first capacitance and the second capacitance of each of the first sensor electrode and the second sensor electrode can be simplified.

[0024] In the touch detection device according to the fourth aspect, the detection unit includes a switching unit. The switching unit switches between charging the first sensor electrode and charging the second sensor electrode together with the first sensor electrode, and switches between charging the second sensor electrode and charging the first sensor electrode together with the second sensor electrode. Thereby, detection of the second capacitance can be enabled with a simple configuration.

[0025] The touch detection device according to the fifth aspect includes a first amplifier unit and a second amplifier unit. The first amplifier unit amplifies the charging power when supplying the charging power for charging the first sensor electrode to the second sensor electrode. Further, the second amplifier unit amplifies the charging power (for example, the amplitude of the charging current) when supplying the charging power for charging the second sensor electrode to the first sensor electrode. Thereby, it is possible to suppress the decrease in the second difference value.

[0026] In the touch detection device according to the sixth aspect, the setting unit sets a reference value that serves as a reference for a first threshold value for the first difference value and a second threshold value for each of the second difference values. Further, the setting unit sets the first threshold value and the second threshold value based on the set reference value. Thereby, it is possible to suppress a decrease in the accuracy of touch determination using the first difference value and the second difference value due to parasitic capacitance.

[0027] In the seventh embodiment of the touch detection device, the setting unit sets reference values ​​from the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode when the occupant is not in contact with the first and second sensor electrodes. This allows for the setting of first and second threshold values ​​that suppress the influence of parasitic capacitance, thereby improving the accuracy of the determination.

[0028] In the touch detection device according to the eighth embodiment, when the occupant is not in contact with either the first sensor electrode or the second sensor electrode, the setting unit sets the smaller of the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode as the reference value. This allows for effective setting of the first and second thresholds, thereby improving the accuracy of the determination.

[0029] In the touch detection device according to the ninth embodiment, the determination unit uses a first difference value and either a second difference value of the first sensor electrode or the second sensor electrode to determine whether the occupant is in contact with the first sensor electrode or the second sensor electrode. This eliminates the need to detect a second capacitance for the second difference value in the first sensor electrode or the second sensor electrode, thereby simplifying the determination process.

[0030] In the touch detection device according to the tenth embodiment, the second difference value for each of the first and second sensor electrodes is applied by accumulating a preset number of second difference values. This effectively suppresses the influence of noise and other factors included in the second capacitance on the second difference value.

[0031] In the touch detection device according to the eleventh embodiment, the determination unit includes a complementation unit that complements the determination result using the second difference value of the first sensor electrode or the second sensor electrode, and the first difference value, using the first capacitance of the first sensor electrode and the second sensor electrode, respectively. This improves the determination accuracy of the determination unit.

[0032] In the touch detection device according to the twelfth embodiment, when the complementary unit determines that the occupant is not in contact with at least one of the first sensor electrode and the second sensor electrode, it determines whether the occupant is in contact with both the first sensor electrode and the second sensor electrode based on the first capacitance of each of the first and second sensor electrodes. This improves the accuracy of the determination when the occupant is in contact with both the first and second sensor electrodes, and when the occupant is not in contact with either. [Brief explanation of the drawing]

[0033] [Figure 1] This is a front view showing a schematic configuration of a steering wheel on which a touch detection device according to the first embodiment is installed. [Figure 2] This is a schematic diagram showing the general configuration of the main parts of a steering wheel. [Figure 3] This is a block diagram showing the schematic configuration of the control unit according to the first embodiment. [Figure 4] This is a schematic diagram showing the general connection of the switching unit 40 and the sensor electrodes. [Figure 5] (A) is a flowchart illustrating the general process of capacitance detection, and (B) is a flowchart illustrating the general process of touch detection. [Figure 6] This is a schematic diagram showing the changes in capacitance L and R. [Figure 7] (A) and (B) are schematic diagrams illustrating the charging process in the detection of capacitance L, with (A) showing the condition with both hands steering and (B) showing the condition with one hand steering. [Figure 8] (A) and (B) are schematic diagrams illustrating the charging process in the detection of capacitance Lb, with (A) showing the two-handed steering state and (B) showing the one-handed steering state. [Figure 9] This diagram shows a schematic representation of capacitance L, R, and differential values ​​DLR, DL according to the steering state. [Figure 10] This diagram shows a schematic representation of the capacitance L, R, Lb, and differential value DL according to the steering state. [Figure 11] This diagram illustrates touch detection using differential values ​​DLR and DL. [Figure 12] This is a block diagram showing the schematic configuration of the control unit according to the second embodiment. [Figure 13] (A) is a flowchart showing an overview of the touch detection process, and (B) is a flowchart showing an overview of the judgment completion process. [Figure 14] This diagram shows a schematic representation of capacitance L, R, and differential values ​​DLR, DL according to the steering state. [Figure 15] This diagram illustrates touch detection using differential values ​​DLR and DL. [Figure 16] This is a block diagram showing the schematic configuration of the control unit according to the third embodiment. [Figure 17] This is a flowchart illustrating the general process for setting reference values. [Figure 18] This diagram shows a schematic representation of capacitance L, R, and differential values ​​DLR, DL according to the steering state. [Modes for carrying out the invention]

[0034] Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] The touch detection device 10 according to the first embodiment is provided in the vehicle's steering system (not shown), which includes a steering wheel 12 that serves as both an operating body and a steering body operated by the occupant in the vehicle. The steering wheel 12 is positioned on the front side of the vehicle, in front of the seat (driver's seat) where the occupant who operates the vehicle sits.

[0035] Figure 1 shows a schematic of the steering wheel 12 on which the touch detection device 10 is installed, as seen from the occupant's perspective in a front view. In the drawing, the right side in the vehicle width direction is indicated by arrow HR, and the top is indicated by arrow UP.

[0036] As shown in Figure 1, the steering wheel 12 is composed of a substantially annular rim portion 14 as a gripping portion, a boss portion 16 provided at the center of the rim portion 14, and a stay portion 18 connecting the rim portion 14 and the boss portion 16, and the steering wheel 12 is formed in a substantially annular shape. In the drawing, the radial direction of the steering wheel 12 is indicated by arrow R, and the circumferential direction of the steering wheel 12 is indicated by arrow L.

[0037] The steering wheel 12 is equipped with a metal core that forms the frame, and the core is composed of a roughly annular rim core portion 20 of the rim portion 14, a boss core portion (not shown) of the boss portion 16, and a stay core portion (not shown) of the stay portion 18. The steering wheel 12 is formed by connecting the rim core portion 20 and the boss core portion by the stay core portion, so that the rim portion 14, the boss portion 16, and the stay portion 18 are integrated together.

[0038] The vehicle is equipped with a steering shaft (not shown), which is rotatably supported by the vehicle body at the front of the driver's seat with its axis oriented approximately in the longitudinal direction of the vehicle. The steering wheel 12 has a boss core metal portion of the boss portion 16 fixed to the rear end of the steering shaft, and the steering wheel 12 is supported by the vehicle body so as to be able to rotate integrally with the steering shaft. Therefore, the core metal of the steering wheel 12 is in contact with the vehicle body via the steering shaft.

[0039] In a vehicle, the steering shaft rotates when the steering wheel 12 is rotated, causing the steering wheels (front wheels) to turn and the vehicle to steer. Figure 1 shows the steering wheel 12 in a straight-ahead position.

[0040] Figure 2 shows a schematic diagram corresponding to a state in which the main part of the rim portion 14 of the steering wheel 12 is cut along the circumferential direction of the steering wheel 12.

[0041] As shown in Figure 2, a base body 22 made of a resin material such as urethane as an insulating material is placed on the rim portion 14 of the steering wheel 12. The base body 22 covers the rim core portion 20 of the rim portion 14, and the rim core portion 20 is housed inside the base body 22 by insert molding.

[0042] The steering wheel 12 has a decorative portion 24 positioned on the outer circumference of the base body 22 as a contact portion (surface). The decorative portion 24 is made of leather (synthetic leather) or resin (partially wood may be used) and has insulating properties. The rim portion 14 of the steering wheel 12 is covered by the decorative portion 24 all around the base body 22 in the radial cross-section of the steering wheel 12 and all around the steering wheel 12 in the circumferential direction.

[0043] As a result, the rim portion 14 of the steering wheel 12 has a rim core portion 20 that forms the ground (GND) portion, the outside of the rim core portion 20 is the base body 22, and the decorative portion 24 is arranged on the outside of the base body 22.

[0044] Such a steering wheel 12 can have a steering heater 26 installed inside its base 22. The steering heater 26 is equipped with heater wiring (heating wire) 28, which is embedded in the base 22 of the steering wheel 12 and connected to a heater drive circuit (not shown). When a heater switch (not shown) located on the vehicle's instrument panel or elsewhere is turned on, power is supplied to the heater wiring 28 from the heater drive circuit. As a result, the heater wiring 28 in the steering heater 26 generates heat, warming (temperature-controlling) the rim 14 of the steering wheel 12.

[0045] On the other hand, the touch detection device 10 is of the capacitive type (self-capacitive type). The touch detection device 10 detects contact of the occupant's (hand) with the rim portion 14 of the steering wheel 12 and determines whether or not the occupant is gripping (steering) the rim portion 14 of the steering wheel 12.

[0046] As shown in Figure 1, the touch detection device 10 includes a sensor unit 30 for detecting the proximity of an occupant (contact with the rim portion 14), and a steering ECU 32 as a control unit. In the touch detection device 10, the steering ECU 32 functions as a determination unit, a detection unit, a charging unit, and a switching unit.

[0047] The sensor unit 30 is equipped with a plurality of sensor electrodes 34, which are arranged on the rim portion 14 of the steering wheel 12. As shown in Figure 2, the sensor electrodes 34 are in sheet form, wrapped around the circumferential direction of the rim portion 14 on the circumferential surface of the base body 22, and extend in the circumferential direction of the steering wheel 12, and are covered by the decorative portion 24.

[0048] The steering wheel 12 is equipped with two sensor electrodes 34. One of the sensor electrodes 34 is positioned over approximately half of the left side of the steering wheel 12 (hereinafter referred to as sensor electrode 34L), and the other sensor electrode 34 is positioned over approximately half of the right side of the steering wheel 12 (hereinafter referred to as sensor electrode 34R). As a result, when the occupant steers the steering wheel 12 (the rim portion 14) with their left hand, the occupant (their left hand) comes into contact with sensor electrode 34L, and when the occupant steers the steering wheel 12 with their right hand, the occupant comes into contact with sensor electrode 34R.

[0049] The steering ECU 32 is located within the boss portion 16 of the steering wheel 12 (not shown), and each of the sensor electrodes 34 (34L, 34R) is connected to it. The steering ECU 32 detects the capacitance of the sensor electrodes 34 (34L, 34R), determines whether an occupant is in contact with each of the sensor electrodes 34L and 34R, and determines whether the occupant is keeping the steering wheel 12 steerable so that the vehicle can be controlled. Figure 3 shows a schematic block diagram of the steering ECU 32 as a control unit.

[0050] The steering ECU32 includes a CPU (Central Processing Unit), memory such as ROM (Read Only Memory) and RAM (Random Access Memory), non-volatile storage such as HDD (Hard Disk Drive) and SSD (Solid State Drive), a communication interface (I / F) section, an input / output interface (I / F) section, and necessary functional circuits, all of which are connected to each other via a bus so as to be able to communicate with one another (not shown).

[0051] Furthermore, the steering ECU 32 stores a capacitance detection program and a touch detection program in ROM or storage. The steering ECU 32's CPU reads the capacitance detection program and touch detection program from ROM or storage, and executes them while expanding them into memory. As a result, as shown in Figure 3, the steering ECU 32 realizes the functions of the switching unit 40, detection control unit 42, calculation unit 44, determination unit 46, and output unit 48.

[0052] The detection control unit 42 includes a first detection unit and a second detection unit, a detection unit 50L for detecting the capacitance generated at the sensor electrode 34L and a detection unit 50R for detecting the capacitance generated at the sensor electrode 34R. When detecting the capacitance of the sensor electrodes 34L and 34R, the detection control unit 42 controls the detection units 50L and 50R, as well as the operation of the switching unit 40. Figure 4 shows a schematic configuration diagram of an example of the switching unit 40, and also schematically shows the connection of the sensor electrodes 34L and 34R.

[0053] As shown in Figure 4, the switching unit 40 is connected to the sensor electrodes 34L and 34R, respectively. Furthermore, the sensor electrode 34L is connected to the detection control unit 42 (detection unit 50L) via the switching unit 40, and the sensor electrode 34R is connected to the detection control unit 42 (detection unit 50R) via the switching unit 40 (see Figure 3).

[0054] The detection units 50L and 50R are capable of outputting charging power (charging current) CHG for charging the sensor electrodes 34L and 34R, grounding (GND) the sensor electrodes 34L and 34R, and detecting the capacitance of the sensor electrodes 34L and 34R (IN).

[0055] Sensor electrode 34L is charged by the charging power CHG input from detection unit 50L, and sensor electrode 34R is charged by the charging power CHG input from detection unit 50R. Detection units 50L and 50R detect the capacitance of sensor electrodes 34L and 34R by receiving a voltage (IN) corresponding to the capacitance of sensor electrodes 34L and 34R. For the sake of simplicity, in the following explanation, it will be assumed that detection units 50L and 50R detect capacitance.

[0056] Furthermore, the switching unit 40 is equipped with amplifiers 52L and 52R, which serve as the first and second amplification units used for indirect charging. The operation of amplifiers 52L and 52R is controlled by the operation signals Ls and Rs output from the detection control unit 42, respectively. Amplifier 52L is activated (turned on) when the operation signal Ls is input from the detection control unit 42, and amplifies the charging power of the sensor electrode 34L at a predetermined amplification factor (for example, by amplifying the charging current) and outputs it to the sensor electrode 34R. Amplifier 52R is also activated (turned on) when the operation signal Rs is input from the detection control unit 42, and amplifies the charging power of the sensor electrode 34R at a predetermined amplification factor and outputs it to the sensor electrode 34L. As a result, the sensor electrodes 34L and 34R are indirectly charged.

[0057] Here, the detection control unit 42 charges the sensor electrodes 34L and 34R individually (direct charging) by supplying charging power to the sensor electrodes 34L and 34R while the operation of amplifiers 52L and 52R is stopped. The detection units 50L and 50R individually detect the capacitance (voltage corresponding to capacitance, hereinafter referred to as capacitance L and R, respectively) at the charged sensor electrodes 34L and 34R. At this time, in the detection control unit 42, the detection unit 50R grounds the sensor electrode 34R during the direct charging of sensor electrode 34L, and the detection unit 50L grounds the sensor electrode 34L during the direct charging of sensor electrode 34R.

[0058] In the detection control unit 42, the amplifier 52L is activated (amplifier 52R is deactivated) to directly charge the sensor electrode 34L and indirectly charge the sensor electrode 34R, thereby detecting the capacitance Lb of the sensor electrode 34L. Also, in the detection control unit 42, the amplifier 52R is activated (amplifier 52L is deactivated) to directly charge the sensor electrode 34R and indirectly charge the sensor electrode 34L, thereby detecting the capacitance Rb of the sensor electrode 34R.

[0059] As a result, the detection control unit 42 detects the capacitances L and R, as well as the capacitances Lb and Rb, for the sensor electrodes 34L and 34R.

[0060] The calculation unit 44 includes an L / R calculation unit 60, a first difference value calculation unit 62, a second difference value calculation unit 64, and a reference calculation unit 66 as a setting unit. The L / R calculation unit 60 calculates the capacitances L and R of the sensor electrodes 34L and 34R, respectively. The first difference value calculation unit 62 calculates the difference value DLR between the capacitance L of sensor electrode 34L and the capacitance R of sensor electrode 34R as the first difference value. In this case, the difference value DLR uses the absolute value of the difference between capacitance L and capacitance R (DLR = |LR| = |RL|).

[0061] The second difference value calculation unit 64 calculates the difference between capacitance L and capacitance Lb as the second difference value DL (DL = L - Lb). The second difference value calculation unit 64 also calculates the difference between capacitance R and capacitance Rb as the second difference value DR (DR = R - Rb).

[0062] The reference calculation unit 66 calculates a reference value S for touch detection using the capacitances L and R detected by the sensor electrodes 34L and 34R when the touch detection device 10 is started. The reference calculation unit 66 also sets a threshold value Tha as a first threshold and a threshold value Thb as a second threshold based on the reference value S.

[0063] The determination unit 46 uses threshold values ​​Tha and Thb set based on the reference value S to determine whether an occupant is in contact with each of the sensor electrodes 34L and 34R (whether the occupant is steering the steering wheel 12) based on the difference values ​​DLR, DL, and DR. The output unit 48 outputs the determination result of the determination unit 46.

[0064] Next, the operation of the first embodiment will be described. In the touch detection device 10, the sensor electrodes 34 (34L, 34R) of the sensor unit 30 are positioned on the steering wheel 12 (rim portion 14). Therefore, when the occupant steers the steering wheel 12 (by making contact, gripping, or holding it in a steerable position), the capacitance of the sensor electrodes 34L and 34R increases.

[0065] The steering ECU 32 of the touch detection device 10 detects the capacitances L, R, Lb, and Rb of the sensor electrodes 34L and 34R, and uses the detected capacitances L, R, Lb, and Rb to determine the steering state of the steering wheel 12 by the occupant.

[0066] As shown in Figure 2, the touch detection device 10 has a structure in which the shield electrode on the rim core metal portion 20 side of the sensor electrode 34 is removed. As a result, the number of parts in the sensor portion 30 located on the steering wheel 12 is reduced in the touch detection device 10, and assembly is simplified, thereby reducing costs.

[0067] However, in the case of the sensor electrode 34, the shield electrode on the side opposite to the side where the occupant is in close proximity (the side with the rim core metal portion 20) is removed, resulting in capacitance C_GND between the sensor electrode and the rim core metal portion 20. Also, if a steering heater 26 is located on the rim portion 14 of the steering wheel 12, capacitance C_HEATER will be generated between the sensor electrode 34 and the heater wiring 28.

[0068] Capacitance C_GND and capacitance C_HEATER become parasitic capacitances Cs at the sensor electrode 34. These parasitic capacitances Cs change according to the temperature of the steering wheel 12 (ambient temperature), and increase as the temperature rises. Therefore, in touch detection, if the ambient temperature rises and the capacitance generated at the sensor electrodes 34L and 34R increases (changes) significantly, false detection may occur. The touch detection device 10 suppresses false detection when performing touch detection (steering detection) of the steering wheel 12 using the sensor electrodes 34L and 34R.

[0069] Here, we will explain the touch detection process in the touch detection device 10. Figure 5(A) shows a flowchart illustrating the capacitance detection process performed in the steering ECU 32, and Figure 5(B) shows a flowchart illustrating the touch detection process performed in the steering ECU 32.

[0070] The touch detection device 10 is activated when, for example, the ignition switch (not shown) of the vehicle is turned on, which activates the steering ECU 32. When the device is activated, the steering ECU 32 performs capacitance detection processing and touch determination processing at predetermined time intervals, detecting the capacitance detected in the capacitance detection processing and using the detected capacitance to determine whether or not the occupant is steering the steering wheel 12.

[0071] In the steering ECU 32, when the device is started, the capacitance detection process begins and is repeated at predetermined time intervals. In the first step 100 of the flowchart in Figure 5(A), the steering ECU 32 detects the capacitance L of the sensor electrode 34L, and in step 102, it detects the capacitance R of the sensor electrode 34R.

[0072] In the steering ECU 32, when detecting capacitances L and R, the operation of amplifiers 52L and 52R is stopped. The steering ECU 32 also grounds sensor electrode 34R and supplies charging power to sensor electrode 34L (direct charging) to detect capacitance L at sensor electrode 34L. The steering ECU 32 also grounds sensor electrode 34L and supplies charging power to sensor electrode 34R (direct charging) to detect capacitance R at sensor electrode 34R.

[0073] Next, in the steering ECU 32, the capacitance Lb at the sensor electrode 34L is detected in step 104, and the capacitance Rb at the sensor electrode 34R is detected in step 106.

[0074] When detecting capacitance Lb, the steering ECU 32 activates amplifier 52L while amplifier 52R is deactivated. In this state, the steering ECU 32 charges sensor electrode 34R (indirectly) via amplifier 52L by charging sensor electrode 34L (directly), and detects the capacitance of sensor electrode 34L as capacitance Lb.

[0075] Furthermore, when detecting capacitance Rb, the steering ECU 32 activates amplifier 52R with amplifier 52L deactivated. In this state, the steering ECU 32 charges the sensor electrode 34R (directly) and then charges the sensor electrode 34R (indirectly) via amplifier 52R, detecting the capacitance of the sensor electrode 34R as capacitance Rb.

[0076] In Figure 5(A), capacitance L, capacitance R, capacitance Lb, and capacitance Rb were detected in this order. However, the detection order is not limited to this, and various configurations can be applied, such as detecting capacitance L, capacitance Lb, capacitance R, and capacitance Rb in that order.

[0077] The steering ECU32 uses the capacitance L, capacitance R, capacitance Lb, and capacitance Rb detected in the capacitance detection process to perform touch detection processing.

[0078] The touch detection device 10 assumes that the occupant is not holding the steering wheel 12 immediately after the vehicle's ignition switch is turned on.

[0079] From here, the steering ECU 32 sets the reference value in the first step 120 of the flowchart in Figure 5(B). The steering ECU 32 sets the reference value S using the capacitance L and capacitance R of parasitic capacitance Cs only, when the occupant is not touching the sensor electrodes 34L and 34R, for example, by setting the average value of capacitance L and capacitance R to reference value S. The steering ECU 32 updates the reference value S using the capacitance L and R when the state in which the occupant is not in contact with the sensor electrodes 34L and 34R continues for a predetermined period of time.

[0080] In step 122, the steering ECU 32 sets thresholds. In setting the thresholds, the steering ECU 32 sets the threshold Tha for the difference value DLR, and the threshold Thb for the difference values ​​DL and DR. After this, the steering ECU 32 performs touch detection processing. The thresholds Tha and Thb are set to be a predetermined difference (capacitance difference) with respect to the reference value S.

[0081] In the steering ECU 32, in the next step 124, the difference value DLR (DLR=|LR|) is calculated using capacitance L and capacitance R. Furthermore, in step 126, the steering ECU 32 calculates the difference value DL (DL=L-Lb) using capacitance L and capacitance Lb, and integrates the results of N calculations (the previous N DLs). Finally, in step 128, the steering ECU 32 calculates the difference value DR (DR=R-Rb) using capacitance R and capacitance Rb, and integrates the results of N calculations (the previous N DRs).

[0082] Subsequently, in step 130, the steering ECU 32 uses threshold values ​​Tha and Thb to perform touch detection (steering control detection) from the differential values ​​DLR and DL and DR. In step 132, the steering ECU 32 outputs the detection result to an external module (not shown) that is configured to use the detection result.

[0083] Here, we will explain the detection of capacitances L, R, Lb, and Rb, and touch detection using the detection results. Note that the basic configuration for detecting capacitances L and Lb is the same as that for detecting capacitances R and Rb. Therefore, in the following, we will mainly explain the detection of capacitances L and Lb on the sensor electrode 34L side, and omit the explanation of the detection of capacitances R and Rb on the sensor electrode 34R side.

[0084] Figure 6 shows a schematic diagram illustrating the changes in capacitance L and R, with the vertical axis representing capacitance (capacitance value). Furthermore, each of the threshold values ​​Tha and Thb, which are set based on the reference value S, is provided with hysteresis, so that the threshold for ON determination (above the threshold) is set higher than the threshold for OFF determination (below the threshold).

[0085] As shown in Figure 6, the reference value S is set based on the capacitances L and R detected when the occupant is not touching the sensor electrode 34 (hands off). The reference value S is also set using the capacitances L and R when the ambient temperature is relatively low and the parasitic capacitance Cs is small. Based on this reference value S, the threshold Tha for the differential value DLR and the threshold Thb for the differential values ​​DL and DR are set.

[0086] When the parasitic capacitance Cs is small, the capacitances L and R when sensor electrodes 34L and 34R are in contact (both hands holding the steering wheel) exceed the threshold Tha. Conversely, when sensor electrodes 34L and 34R are not in contact (both hands released), the capacitances L and R do not exceed the threshold Tha. This enables accurate touch detection.

[0087] However, if the parasitic capacitance Cs increases due to rising temperature or other factors, the capacitances L and R may exceed the threshold Tha even when the occupant is not touching the sensor electrodes 34L and 34R (both hands off). As a result, a situation may arise where proper touch detection cannot be performed based on capacitances L and R.

[0088] Furthermore, as shown in Figure 4, the sensor electrode 34L has parasitic capacitances Cs, namely capacitances C_GND and C_HEATER, and when an occupant touches the sensor electrode 34L, capacitance Cf(CfL) is added. Similarly, the sensor electrode 34R has parasitic capacitances Cs, namely capacitances C_GND and C_HEATER, and when an occupant touches the sensor electrode 34R, capacitance Cf(CfR) is added. Note that in Figure 4, capacitance Chb represents the capacitance of the human body.

[0089] In the touch detection device 10, when detecting the capacitance L of the sensor electrode 34L, the amplifier 52L is stopped, the sensor electrode 34R side is grounded, and the sensor electrode 34L is directly charged to detect the capacitance L. Therefore, if the occupant is not touching the sensor electrode 34L, parasitic capacitance Cs is detected as the capacitance L.

[0090] Figures 7(A) and 7(B) show schematic diagrams illustrating the charging (power supply) process in the detection of capacitance L. Figure 7(A) shows the condition with both hands steering, and Figure 7(B) shows the condition with one hand steering.

[0091] As shown in Figure 7(A), in the touch detection device 10, when an occupant touches the sensor electrodes 34L and 34R, charging power flows from the sensor electrode 34L through the human body (occupant's body) to the sensor electrode 34R.

[0092] Furthermore, as shown in Figure 7(B), in the touch detection device 10, if the occupant is touching only the sensor electrode 34L, the charging power is grounded (GND) from the sensor electrode 34L through the human body (occupant's body) and does not flow to the sensor electrode 34R.

[0093] Furthermore, when the touch detection device 10 detects the capacitance Lb at the sensor electrode 34L, it directly charges the sensor electrode 34L and also operates the amplifier 52L to indirectly charge the sensor electrode 34R, thereby detecting the capacitance of the sensor electrode 34L as capacitance Lb. Therefore, if the occupant is not touching the sensor electrode 34L, parasitic capacitance Cs is detected as capacitance Lb.

[0094] Figures 8(A) and 8(B) show schematic diagrams illustrating the charging process in the detection of capacitance Lb. Figure 8(A) shows the condition with both hands steering, while Figure 8(B) shows the condition with one hand steering.

[0095] As shown in Figure 8(A), in the touch detection device 10, when an occupant touches the sensor electrodes 34L and 34R, the charging power for direct charging is grounded from the sensor electrode 34L through the human body (occupant's body), and the charging power for indirect charging is grounded from the sensor electrode 34R through the human body (occupant's body).

[0096] Furthermore, as shown in Figure 8(B), in the touch detection device 10, if the occupant is touching only the sensor electrode 34L, the charging power is transmitted from the sensor electrode 34L through the human body (occupant's body) to ground (GND), and does not flow to the sensor electrode 34R.

[0097] Figure 9 shows a schematic diagram illustrating the capacitance L, R, and differential values ​​DLR and DL according to the crew's steering control state.

[0098] Capacitances L and R each contain a small amount of parasitic capacitance Cs. Furthermore, the difference value DLR is defined as the difference between capacitance L and capacitance R. Therefore, the parasitic capacitance Cs cancels out in the difference value DLR. As a result, as shown in Figure 9, when both sensor electrodes 34L and 34R are touching (hands-on steering) or when neither is touching (hands-off), the difference value DLR becomes small and does not exceed the threshold value Tha.

[0099] In contrast, when only one of the sensor electrodes 34L or 34R is in contact (one-handed steering), the difference value DLR will include the capacitance L or R of the sensor electrode 34 that is being touched. Therefore, the difference value DLR exceeds the threshold Tha.

[0100] This allows for accurate determination of whether the occupant is steering the steering wheel 12 using either their right or left hand by using the difference value DLR (=|LR|). Furthermore, while the difference value DLR (=|LR|) alone does not clearly indicate whether the occupant is steering with their right or left hand, comparing the capacitance L, including the parasitic capacitance Cs, with the capacitance R can complement the determination of which hand is steering the steering wheel 12.

[0101] On the other hand, the capacitance L detected in Figure 7(B) and the capacitance Lb detected in Figure 8(B) have only a slight difference and can be considered almost the same (L ≈ Lb). That is, when the occupant is touching only one of the sensor electrodes 34L and 34R, the difference value DL (and the difference value DR) can be considered zero (DL ≈ 0, DR ≈ 0). Furthermore, capacitance L and capacitance Lb can be considered almost the same even when the occupant is not touching either of the sensor electrodes 34L or 34R (L ≈ Lb).

[0102] In contrast, a difference arises between the capacitance L detected in Figure 7(A) and the capacitance Lb detected in Figure 8(A). For example, as shown in Figure 9, when an occupant touches the sensor electrodes 34L and 34R respectively, the capacitance Lb becomes smaller than the capacitance L (L > Lb).

[0103] From here, by setting a threshold value Thb relative to the reference value S according to the amplification factor in amplifiers 52L and 52R, it is possible to determine from the difference value DL (or difference value DR) whether or not the occupant is steering the steering wheel 12 with both hands.

[0104] The difference between capacitance L and capacitance Lb increases when the amplification factor is set high when amplified by amplifier 52L. Figure 10 shows a schematic diagram of capacitances L, R, Lb, and the difference value DL.

[0105] As shown in Figure 10, when the crew member is using one-handed steering or both hands off the steering wheel (not shown), the capacitance Lb is approximately the same as the capacitance L (L ≈ Lb). Therefore, the difference value DL is also relatively small. However, even when using both hands to steer, the difference value DL is not large. From this, it can be shown that the difference value DL can be increased by providing the amplifier 52L.

[0106] However, if the amplification factor of amplifier 52L is increased, the noise component is also amplified, increasing the likelihood of misjudgment. Therefore, the touch detection device 10 uses the cumulative value of multiple (N) steps for the difference value DL, thereby preventing misjudgment caused by noise components while allowing the threshold Thb to be set to a larger value. As a result, the touch detection device 10 can accurately determine whether both hands are being used for steering when the difference value DL is equal to or greater than the threshold Thb.

[0107] Figure 11 shows the results of touch detection using the difference values ​​DLR (=|LR|) and DL (=L-Lb) in the determination unit 46 of the steering ECU 32.

[0108] As shown in Figure 11, the determination unit 46 determines that the occupant is not holding the steering wheel 12 (hands off) if the difference value DLR is less than the threshold Tha (OFF) and the difference value DL is less than the threshold Thb (OFF).

[0109] In response to this, the determination unit 46 determines that if the difference value DL is less than the threshold Thb (OFF), but the difference value DLR is greater than or equal to the threshold Tha (ON), the occupant is steering the steering wheel 12 with one hand (one-handed steering).

[0110] Furthermore, the determination unit 46 determines that the occupant is steering the steering wheel 12 with both hands (two-handed steering) if the difference value DL is greater than or equal to the threshold Thb (ON) and the difference value DLR is greater than or equal to the threshold Tha (ON).

[0111] Thus, the touch detection device 10 can accurately determine whether the steering is being done with one hand or not by using DLR, which is the difference between the capacitance L of sensor electrode 34L and the capacitance R of sensor electrode 34R. Furthermore, the touch detection device 10 can accurately determine whether the steering is being done with both hands or not by using DL, which is the difference between the capacitance L and the capacitance Lb. As a result, even when using sensor electrodes 34L and 34R, which reduce costs by omitting shield electrodes, the touch detection device 10 can accurately determine touches without being affected by parasitic capacitance Cs.

[0112] Furthermore, the touch detection device 10 has a sensor electrode 34L positioned on the left side of the steering wheel 12 and a sensor electrode 34R positioned on the right side, so it can accurately determine the steering state of the steering wheel 12 held by the occupant.

[0113] Furthermore, in the touch detection device 10, amplifiers 52L and 52R are provided in the switching unit 40, and the operation / stopping of amplifiers 52L and 52R is controlled to switch between direct charging and indirect charging, thus simplifying the configuration for capacitance detection processing.

[0114] Furthermore, the touch detection device 10 is equipped with amplifiers 52L and 52R to perform power amplification for indirect charging. In addition, the touch detection device 10 uses the cumulative value of N steps for the differential values ​​DL and DR applied to the judgment. Therefore, the touch detection device 10 can suppress a decrease in the accuracy of touch judgment even if the differential values ​​DL and DR are small.

[0115] Furthermore, the touch detection device 10 sets a reference value S using capacitances L and R detected when it is determined that the occupant is not touching the surface. As a result, the touch detection device 10 can appropriately set the threshold values ​​Tha and Thb even if the parasitic capacitance changes, thereby suppressing a decrease in judgment accuracy caused by parasitic capacitance.

[0116] In the first embodiment described above, the difference value DL on the sensor electrode 34L side and the difference value DR on the sensor electrode 34R side are used. However, since the difference value DL and the difference value DR are approximate values, either DL or DR may be used. This eliminates the need for detection processing of either capacitance Lb or Rb, thus simplifying the capacitance detection process.

[0117] Furthermore, in the first embodiment, amplifiers 52L and 52R are provided in the switching unit 40 to amplify the charging power of indirect charging, thereby increasing the changes in the detected capacitances Lb and Rb. However, the amplifiers may be omitted. In this case, the capacitances Lb and Rb for multiple cycles may be integrated, and the integrated value may be used.

[0118] [Second Embodiment] Next, a second embodiment will be described. In the second embodiment, the basic configuration is the same as in the first embodiment, and functional components similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and their descriptions are omitted.

[0119] In the touch detection device 10 according to the first embodiment, the cumulative values ​​of N trials are used as the difference values ​​DL (=L-Lb) and DR (=R-Rb) used for touch determination. This suppresses the occurrence of determination errors caused by the small size of the difference values ​​DL and DR (calculated from the result of one detection) for each trial.

[0120] However, when the driver holds the steering wheel 12 with both hands, there may be a delay before it is determined that the steering is being held with both hands, and when at least one hand is released from the steering wheel 12 that was being held with both hands, there may be a delay before it is determined that the steering is being held with one hand or that the driver has let go (determination delay). In the second embodiment, such determination delays are suppressed.

[0121] The touch detection device 70 according to the second embodiment includes a steering ECU 72 as a control unit. The steering ECU 72 is applied in the second embodiment in place of the steering ECU 32 of the first embodiment. Figure 12 shows a schematic block diagram of the control unit formed by the steering ECU 72 in the touch detection device 70.

[0122] As shown in Figure 12, the steering ECU 72 has a determination unit 74, which is formed in the steering ECU 72 in place of the determination unit 46 of the steering ECU 32 according to the first embodiment. The determination unit 74 has a determination complementation unit 76 formed as a complementary unit.

[0123] The functions of the determination unit 74 in the steering ECU 72 include the same functions as the determination unit 46 in the steering ECU 32. Furthermore, the determination completion unit 76 uses the capacitance L detected at the sensor electrode 34L and the capacitance R detected at the sensor electrode 34R to complete the determination result of the determination unit 74 (determination unit 46), thereby suppressing the occurrence of determination delay. In other words, the steering ECU 72 suppresses the occurrence of determination delay by performing touch detection using capacitances L and R in addition to the difference values ​​DLR, DL, and DR.

[0124] Next, the touch detection process in the touch detection device 70 will be described as the operation of the second embodiment. Figure 13(A) shows a flowchart of the touch detection process according to the second embodiment, and Figure 13(B) shows a flowchart of the judgment completion process. Figure 14 shows a schematic of the capacitance L, R, and difference values ​​DLR, DL according to the gripping (steering) state of the steering wheel 12, and Figure 15 shows the judgment result of the touch detection using the difference value DLR (=|LR|) and difference value DL (=L-Lb) in addition to the capacitance L, R in the judgment unit 74 of the steering ECU 72 in a diagram.

[0125] The touch detection device 70, like the touch detection device 10, detects capacitances L, Lb, R, and Rb (or capacitances L, Lb, and R), and sets a reference value S from the capacitances L and R when the occupant is not gripping the steering wheel 12. In this case, the touch detection device 70 mainly uses capacitances L and R due to parasitic capacitance Cs to set the reference value S, and threshold values ​​Tha and Thb are set according to the set reference value S, and the reference value S and threshold values ​​Tha and Thb are updated as appropriate.

[0126] Furthermore, when the touch detection device 70 detects capacitances L, Lb, R, and Rb, it calculates the difference values ​​DLR (=|LR|), DL (=L-Lb), and DR (=R-Rb) (the difference values ​​DLR and DL may also be used), and performs touch detection based on the calculation results. As a result, the touch detection device 70 can achieve the same effect as the touch detection device 10. Note that in the touch detection process shown in Figure 13(A), the setting process of the reference value S and threshold values ​​Tha and Thb (steps 120, 124) is omitted.

[0127] As shown in Figure 13(A), in step 124, the steering ECU 72 calculates the difference value DLR (DLR=|LR|) using capacitance L and capacitance R. In step 126, the steering ECU 72 calculates the difference value DL (DL=L-Lb) using capacitance L and capacitance Lb, and accumulates the results of N calculations (N DLs). Furthermore, in step 128, the steering ECU 32 calculates the difference value DR (DR=R-Rb) using capacitance R and capacitance Rb, and accumulates the results of N calculations (N DRs).

[0128] After that, in step 130, the steering ECU 72 performs a touch determination (holding steering determination) using the threshold values Tha and Thb and the difference values DLR, DL, and DR. As a result, in the touch detection device 70, similar to the touch detection device 10, from the difference values DLR, DL, and DR, it is determined whether the gripping state of the steering wheel 12 is both hands released, one - hand holding steering on either the left or right, or both hands holding steering. When the gripping state with respect to the steering wheel 12 is determined in the steering ECU 72, the determination complement processing shown in FIG. 13(B) is executed.

[0129] In the first step 140 of the flowchart in FIG. 13(B), the steering ECU 72 checks whether the determination result is other than one - hand holding steering. Here, when the determination result is one - hand holding steering (holding steering by the right hand or the left hand) determined by the difference value DLR, the steering ECU 72 makes a negative determination in step 140 and transfers to step 132, and outputs the determination result (the determination result in FIG. 13(A)) to an external module (not shown).

[0130] On the other hand, when the determination result is other than one - hand holding steering, that is, both hands released or both hands holding steering, the steering ECU 72 makes an affirmative determination in step 140. When the steering ECU 72 makes an affirmative determination in step 140, it checks whether the capacitance L is greater than or equal to the threshold value Tha (step 142), and whether the capacitance R is greater than or equal to the threshold value Tha (steps 144 and 146).

[0131] When the capacitance L is greater than or equal to the threshold value Tha (L ≥ Tha) in the steering ECU 72, it makes an affirmative determination in step 140 and checks whether the capacitance R is greater than or equal to the threshold value Tha (R ≥ Tha) in the next step 144. As a result, if the capacitance R is less than the threshold value Tha (R < Tha), the steering ECU 72 makes a negative determination in step 144, transfers to step 148, determines it as one - hand holding steering by the left hand, and in step 132, outputs the determination result to the external module.

[0132] Also, in the steering ECU 72, when the capacitance L is less than the threshold Tha (L < Tha), a negative determination is made in step 140, and in the next step 146, it is confirmed whether the capacitance R is greater than or equal to the threshold Tha (R ≧ Tha). Thus, if the capacitance R is greater than or equal to the threshold Tha (R ≧ Tha), the steering ECU 72 makes an affirmative determination in step 146 and proceeds to step 150, determines that it is a one - hand steering by the right hand, and in step 132, outputs the determination result to an external module.

[0133] On the other hand, in the steering ECU 72, when the capacitance L is greater than or equal to the threshold Tha (L ≧ Tha) and the capacitance R is greater than or equal to the threshold Tha (R ≧ Tha), an affirmative determination is made in step 144 and the process proceeds to step 148. In this step 148, the steering ECU 72 determines that the steering wheel 12 is being held with both hands, and by proceeding to step 132, outputs the determination result to an external module.

[0134] Also, in the steering ECU 72, when the capacitance L is less than the threshold Tha (L < Tha) and the capacitance R is less than the threshold Tha (R < Tha), an affirmative determination is made in step 146 and the process proceeds to step 150. In this step 150, the steering ECU 72 determines that both hands have been released from the steering wheel 12, and by proceeding to step 132, outputs the determination result to an external module.

[0135] That is, in the steering ECU 72, when both the capacitances L and R are greater than or equal to the threshold Tha (L ≧ Tha, R ≧ Tha), an affirmative determination is made in each of steps 142 and 144 to determine that the steering wheel 12 is being held with both hands. Also, in the steering ECU 72, when both the capacitances L and R are less than the threshold Tha (L < Tha, R < Tha), a negative determination is made in each of steps 142 and 144 to determine that both hands have been released from the steering wheel 12.

[0136] As shown in Figure 14, the difference values ​​DL (DL=L-Lb) and DR (DR=R-Rb) gradually increase when transitioning from a hands-free state to hands-on steering. Note that the difference value DR is not shown in Figure 14.

[0137] Therefore, when transitioning from a hands-free state (or a one-handed steering state not shown) to hands-on steering, even though both capacitances L and R exceed the threshold Tha, there is a period during which hands-on steering is not detected because the difference value DL does not reach the threshold Thb. In this case, as shown in Figure 15, the steering ECU 72 determines that both hands are being used for steering if the capacitances L and R are equal to or greater than the threshold Tha.

[0138] Furthermore, as shown in Figure 14, when transitioning from two-handed steering to two-handed release (or one-handed steering not shown), the difference values ​​DL (DL=L-Lb) and DR (DR=R-Rb) gradually decrease. Therefore, when transitioning from two-handed steering to two-handed release (or one-handed steering not shown), even though both capacitances L and R are below the threshold Tha, the difference value DL is greater than or equal to the threshold Thb, resulting in a period during which the system is not judged as two-handed.

[0139] In this case, as shown in Figure 15, the steering ECU 72 can determine that the steering wheel is hands-free if the capacitances L and R each fall below the threshold Tha.

[0140] Furthermore, when transitioning from two-handed steering to one-handed steering, the difference values ​​DL (DL=L-Lb) and DR (DR=R-Rb) gradually decrease. As a result, when transitioning from two-handed to one-handed steering, there is a period during which the ship is incorrectly judged as two-handed steering because the difference value DLR is greater than or equal to the threshold Tha (one-handed steering determination) and the difference value DL is greater than or equal to the threshold Thb. In this case, as shown in Figure 15, the steering ECU 72 can determine that one-handed steering is occurring if either capacitance L or R exceeds the threshold Tha.

[0141] [Third Embodiment] Next, a third embodiment will be described. In the third embodiment, the basic configuration is the same as in the second embodiment. Furthermore, in the third embodiment, functional components similar to those in the first and second embodiments are denoted by the same reference numerals as in the first and second embodiments, and their descriptions are omitted.

[0142] In the first and second embodiments, a reference value S was set using capacitances L and R detected when both hands were released from the steering wheel 12, and threshold values ​​Tha and Thb were set based on the reference value S. However, because the parasitic capacitance Cs changes according to the ambient temperature, the updating of the reference value S and threshold values ​​Tha and Thb is delayed, increasing the likelihood of misjudgment. In the third embodiment, a touch detection device in which misjudgment is suppressed is described.

[0143] The touch detection device 80 according to the third embodiment includes a steering ECU 82 as a control unit. The steering ECU 72 is applied to the third embodiment in place of the steering ECU 32 of the first embodiment or the steering ECU 72 of the second embodiment. Figure 16 shows a schematic block diagram of the control unit formed by the steering ECU 72.

[0144] As shown in Figure 16, the steering ECU 82 has a reference calculation unit 84 as a setting unit. The reference calculation unit 84 is formed in the steering ECU 82 in place of the reference calculation unit 66 of the first and second embodiments.

[0145] The reference calculation unit 84 sets the reference value S and threshold values ​​Tha and Thb when the device is started, similar to the reference calculation unit 66. Also, similar to the reference calculation unit 66, the reference calculation unit 84 updates the reference value S and threshold values ​​Tha and Thb when the steering wheel 12 has been left with both hands off the wheel for a predetermined period of time or longer.

[0146] Furthermore, the reference calculation unit 84 updates the reference value S based on the capacitances L and R when the steering wheel 12 is being steered with one hand, and updates the threshold values ​​Tha and Thb according to the updated reference value S.

[0147] Next, the reference value update process in the touch detection device 80 will be described as an operation of the third embodiment. Figure 17 shows a schematic of the reference value update process according to the third embodiment in flowchart form, and Figure 18 shows a schematic of the capacitance L, R, and difference values ​​DLR, DL according to the gripping (steering) state of the steering wheel 12 in line diagram form.

[0148] Similar to touch detection devices 10 and 70, the touch detection device 80 detects capacitance L, Lb, R, and Rb (or capacitance L, Lb, and R), and sets a reference value S from capacitance L and R when the occupant is not gripping the steering wheel 12. Furthermore, the touch detection device 80 performs touch detection while detecting capacitance L, Lb, R, and Rb. As a result, the touch detection device 80 can achieve the same effect as the touch detection device 10 and the touch detection device 80.

[0149] Here, the touch detection device 80 performs a reference value update process not only when both hands are released, but also by executing the flowchart shown in Figure 17 at pre-set timings. The reference value update process is performed by the steering ECU 82, for example, after a pre-set time has elapsed, when the change in ambient temperature detected by the temperature detection means exceeds a predetermined value, or when it is determined that the parasitic capacitance Cs has exceeded the threshold Tha.

[0150] As shown in Figure 17, the steering ECU 82 checks in the first step 160 whether the difference value DLR is greater than or equal to the threshold Tha. If the difference value DLR is less than the threshold Tha, the steering ECU 82 makes a negative determination in step 160 and terminates the process. However, if a negative determination is made in step 160, and it is the timing for updating the reference value S using only the parasitic capacitances Cs and L and R, the process of updating the reference value S and the thresholds Tha and Thb may be executed.

[0151] In the steering ECU 82, when the differential value DLR is greater than or equal to the threshold value Tha, an affirmative determination is made in step 160 and the process proceeds to step 162. In step 162, the steering ECU 62 compares the capacitance L and the capacitance R.

[0152] When the differential value DLR is greater than or equal to the threshold value Tha, one of the sensor electrodes 34L and 34R is in a non-contact state and the other has the hand of an occupant touching it. For this reason, when the occupant is touching the sensor electrode 34L, the capacitance L becomes L = Cf + Cs, while the capacitance R becomes R = Cs. Also, when the occupant is touching the sensor electrode 34R, the capacitance L becomes L = Cs, while the capacitance R becomes R = Cf + Cs.

[0153] From here, in the steering ECU 82, in step 160, it is confirmed whether the capacitance L is greater than the capacitance R (L > R?)(L > R? is also acceptable). As a result, when the capacitance R is smaller than the capacitance L (L > R), the steering ECU 82 makes an affirmative determination in step 162 and proceeds to step 164, and updates the reference value S by setting the capacitance R to the reference value S. Also, when the capacitance L is smaller than the capacitance R (L < R), the steering ECU 82 makes a negative determination in step 162 and proceeds to step 166, and updates the reference value S by setting the capacitance L to the reference value S.

[0154] When the steering ECU 82 updates the reference value S, in step 168, each of the threshold values Tha and Thb is updated by setting each of the threshold values Tha and Thb based on the updated reference value S. As a result, together with the reference value S, the threshold values Tha and Thb are shifted according to the parasitic capacitance Cs (see FIG. 18). After this, in the steering ECU 82, touch determination processing is performed using the updated threshold values Tha and Thb (the threshold values Tha and Thb shifted according to the parasitic capacitance Cs).

[0155] As shown in Figure 18, when the temperature rises while both rudder controls are engaged, the parasitic capacitances Cs contained in capacitances L and R increase. In this case, the difference value DLR increases as parasitic capacitances Cs in capacitance L and Cs in capacitance R are combined. As a result, the difference between the parasitic capacitances Cs in capacitance L and Cs in capacitance R exceeds the threshold Tha, causing the difference value DLR to exceed the threshold Tha even when both rudder controls are engaged, leading to a misjudgment.

[0156] Furthermore, if the difference between the parasitic capacitance Cs contained in capacitance L and the parasitic capacitance Cs contained in capacitance R exceeds the threshold Tha, even with one-handed steering, the difference value DLR will be less than or equal to the threshold tha, and the system will no longer be recognized as having one-handed steering.

[0157] In contrast, when the reference value S is updated and the thresholds Tha and Thb are updated, even if the difference between the parasitic capacitance Cs included in capacitance L and the parasitic capacitance Cs included in capacitance R becomes large, the difference value DLR will not exceed the threshold Tha without any adjustments.

[0158] Therefore, in the touch detection device 80, even if the difference in parasitic capacitance Cs between sensor electrodes 34L and 34R becomes large due to continuous one-handed steering, misjudgment in the touch judgment process is suppressed.

[0159] In the first, second, and third embodiments described above, touch detection was performed using the sensor electrode 34L on the left side and the sensor electrode 34R on the right side of the steering wheel 12. However, sensor electrodes may also be placed on the occupant side (front side) and the opposite side (back side) of the steering body on both the left and right sides. This makes it possible to determine whether the occupant is touching the steering body on both the left and right sides, and whether they are gripping each side. [Explanation of Symbols]

[0160] 10, 70, 80... Touch detection device, 12... Steering wheel (steering body), 14... Rim section, 28... Heater wiring, 30... Sensor section, 32, 72, 82... Steering ECU (switching section, detection section, calculation section, determination section), 34 (34L, 34R)... Sensor electrodes (first sensor electrode and second sensor electrode), 40... Switching section 42...Detection control unit (switching unit, detection unit), 44, 44A...Calculation unit, 46, 74, 84...Decision unit, 50L, 50R...Detection unit (first detection unit and second detection unit), 52L, 52R...Amplifier (amplification unit), 62...First difference value calculation unit, 64...Second difference value calculation unit, 66, 84...Reference calculation unit (setting unit), 76...Decision completion unit (completion unit).

Claims

1. A first sensor electrode and a second sensor electrode are positioned on the steering body and are accessible to the occupant, and the capacitance generated at each of them is detected. When detecting a first capacitance for each of the first and second sensor electrodes, the detection unit directly charges each of the first and second sensor electrodes for detection, and when detecting a second capacitance for each of the first and second sensor electrodes, the detection unit directly charges one of the first and second sensor electrodes and indirectly charges the other using the power from the direct charge, A calculation unit calculates a first difference value which is the difference between the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode, and calculates a second difference value which is the difference between the first capacitance and the second capacitance for each of the first sensor electrode and the second sensor electrode. A determination unit that determines whether an occupant is in contact with the first sensor electrode and the second sensor electrode, using the first difference value and the second difference values ​​of the first sensor electrode and the second sensor electrode, A touch detection device including a touch detection device.

2. The touch detection device according to claim 1, wherein the first sensor electrode and the second sensor electrode are two sensor electrodes among a plurality of sensor electrodes arranged on the steering body.

3. The detection unit is A first detection unit that supplies power to the first sensor electrode to detect the first capacitance, and also supplies power to the first sensor electrode and the second sensor electrode to detect the second capacitance, A second detection unit that supplies power to the second sensor electrode to detect the second capacitance, and also supplies power to the second sensor electrode and the first sensor electrode to detect the second capacitance, A touch detection device according to claim 1, including the following:

4. The detection unit is Switching between supplying power to the first sensor electrode and supplying power to the second sensor electrode together with the first sensor electrode, The touch detection device according to claim 3, further comprising a switching unit for switching between supplying power to the second sensor electrode and supplying power to the first sensor electrode together with the second sensor electrode.

5. The touch detection device according to claim 3, comprising a first amplification unit that amplifies the charging power supplied to the second sensor electrode when charging the first sensor electrode, and a second amplification unit that amplifies the charging power supplied to the first sensor electrode when charging the second sensor electrode.

6. The touch detection device according to claim 1, further comprising a setting unit that sets a reference value to be used as a basis for a first threshold value for the first difference value and a second threshold value for each of the second difference values, and sets the first threshold value and the second threshold value based on the set reference value.

7. The touch detection device according to claim 6, further comprising setting the reference value from the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode when the occupant is not in contact with the first sensor electrode and the second sensor electrode.

8. The touch detection device according to claim 6, further comprising setting the setting unit to the smaller of the first capacitance of the first sensor electrode and the first capacitance of the second sensor electrode as the reference value when the occupant is not in contact with either the first sensor electrode or the second sensor electrode.

9. The touch detection device according to claim 1, further comprising the determination unit determining contact of an occupant with the first sensor electrode and the second sensor electrode using the first difference value and one of the second difference values ​​of the first sensor electrode and the second sensor electrode.

10. The touch detection device according to claim 1, wherein each of the second difference values ​​is applied after being accumulated by a predetermined number of the second difference values.

11. The touch detection device according to claim 1, wherein the determination unit includes a complementation unit that complements the determination result using the second difference value of the first sensor electrode or the second sensor electrode and the first difference value using the first capacitance of the first sensor electrode and the second sensor electrode, respectively.

12. The touch detection device according to claim 11, further comprising the complementation unit determining whether the occupant is in contact with both the first and second sensor electrodes based on the first capacitance of each of the first and second sensor electrodes when it is determined that the occupant is not in contact with at least one of the first and second sensor electrodes.

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