Steering device

Abstract

To provide a steering device that can be prevented from erroneously determining due to variation of an environmental condition around a steering handle, with a simple structure.SOLUTION: A steering device comprises a plurality of proximity sensors in which electrode parts are installed at different positions with respect to a steering handle, and a gripping determination device that determines whether the steering handle is gripped or not, on the basis of filter values Ch_R_f(n), Ch_L_f(n) of measured values by the plurality of proximity sensors. The gripping determination device comprises a capacitance threshold setting part that sets a reference value Ch_0 with respect to electrostatic capacitance of the electrode parts, and a determination part that determines whether the steering handle is gripped or not, on the basis of a difference between measured values Ch_R_d(n), Ch_L_d(n) and the reference value Ch_0. The capacitance threshold setting part determines whether the reference value Ch_0 needs to be corrected or not, on the basis of a similarity of a changing trend of the filter values Ch_R_f(n), Ch_L_f(n) of the measured values by the plurality of proximity sensors.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a steering device, and more particularly to a steering device including a steering wheel and a grip determination device that determines whether or not the steering wheel is being gripped by a driver. [Background technology]

[0002] In recent years, in order to improve traffic safety, vehicles are increasingly being equipped with driving assistance devices that assist the driver in driving the vehicle, such as a lane keeping function, a lane departure prevention function, a lane change function, and a preceding vehicle following function. In vehicles equipped with such driving assistance devices, a grip determination device as shown in Patent Document 1, for example, determines whether the driver is gripping the steering wheel, and if it is determined that the driver is not gripping the steering wheel, the device may prompt the driver to grip the steering wheel or cancel the driving assistance function being executed.

[0003] The grip determination device disclosed in Patent Document 1 determines whether or not the driver is gripping the steering wheel based on a comparison between the output value of a capacitance sensor provided on the steering wheel and a predetermined threshold value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-87883 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the output value of the capacitance sensor varies depending on the temperature around the steering wheel. Therefore, if the threshold value is fixed regardless of changes in the environmental conditions around the steering wheel, there is a risk of erroneous determination. Therefore, in the invention described in Patent Document 1, the threshold value for the output value of the capacitance sensor is changed based on the detected value or estimated value of the temperature around the steering wheel.

[0006] However, in the invention shown in Patent Document 1, it is necessary to provide a temperature sensor in addition to the capacitance sensor. Also, the output value of the capacitance sensor varies not only with the surrounding temperature but also with the humidity. Therefore, in order to take the surrounding humidity into account, not only a temperature sensor but also a humidity sensor is required.

[0007] The present invention aims to provide a steering device that has a simple configuration and can prevent erroneous judgments due to changes in the environmental conditions around the steering wheel, and ultimately to contribute to the development of sustainable transportation systems. [Means for solving the problem]

[0008] (1) A steering device according to the present invention (for example, a steering device 1 described later) includes a steering wheel (for example, a steering wheel 2 described later) that receives a steering operation of a vehicle by a driver, a measuring device (for example, measuring circuits 42, 52 described later) that measures the capacitance of an electrode portion (for example, electrode portions 40, 50 described later) provided on the steering wheel, a plurality of the measuring devices having different installation positions of the electrode portion, and a control device that determines whether or not the steering wheel is being gripped based on measurement values ​​(for example, measurement values ​​Ch_R_d(n), Ch_L_d(n) and their filter values ​​Ch_R_f(n), Ch_L_f(n) described later) measured by the plurality of the measuring devices. and a grip determination device (e.g., grip determination device 80 described later) for determining whether or not the steering wheel is being gripped, and a detection target area is defined on the steering wheel for each of the measuring devices. The grip determination device includes a capacitance threshold setting unit (e.g., capacitance threshold setting unit 82 described later) that sets a capacitance threshold for the capacitance of the electrode unit (e.g., a reference value Ch_0 or a grip determination threshold Ch_th described later), and a determination unit (e.g., determination unit 81 described later) that determines whether or not the steering wheel is being gripped for each of the detection target areas based on a difference or comparison between the measurement value and the capacitance threshold, and the capacitance threshold setting unit determines whether or not the capacitance threshold needs to be corrected based on a degree of similarity in the change trends of the measurement values ​​of the multiple measuring devices.

[0009] (2) In this case, it is preferable that the capacity threshold setting unit calculates a similarity (e.g., similarity S(n) described below) that increases or decreases depending on the degree of similarity, corrects the capacity threshold when the similarity is higher than a predetermined similarity standard (e.g., similarity standard S_th described below), and maintains the capacity threshold constant when the similarity is lower than the similarity standard.

[0010] (3) In this case, it is preferable that the capacity threshold setting unit calculates the similarity by comparing the slopes of the measurement values ​​of the multiple measurement devices (for example, slopes a_R(n) and a_L(n) described below).

[0011] (4) In this case, it is preferable that the capacity threshold setting unit calculates the similarity by comparing the amount of change in the measurement values ​​of each of the multiple measurement devices over a predetermined judgment period (for example, the amounts of change dCh_R_f(n), dCh_L_f(n) described below).

[0012] (5) In this case, it is preferable that the capacity threshold setting unit corrects the capacity threshold toward an increase when the measurement values ​​of the multiple measuring devices are all tending to increase, and corrects the capacity threshold toward a decrease when the measurement values ​​of the multiple measuring devices are all tending to decrease.

[0013] (6) In this case, it is preferable that the judgment unit judges whether or not the steering wheel is being gripped based on a capacity difference value (e.g., capacity difference values ​​ΔCh_R, ΔCh_L described below) obtained by subtracting a reference value which is the capacity threshold value (e.g., reference value Ch_0 described below) from the measurement value.

[0014] (7) In this case, it is preferable that the determination unit determines whether the steering wheel is being gripped by comparing the measurement value with a grip determination threshold (for example, a grip determination threshold Ch_th described later) which is the capacity threshold. Effect of the Invention

[0015] (1) The grip determination device of the steering device according to the present invention includes a plurality of capacitance measuring devices having electrode portions at different installation positions relative to the steering wheel, and a grip determination device that determines whether or not the steering wheel is being gripped based on measurements by the plurality of measuring devices. A detection target area is defined for each measuring device on the steering wheel, and the grip determination device includes a capacitance threshold setting unit that sets a capacitance threshold for the capacitance of the electrode portion, and a determination unit that determines whether or not the steering wheel is being gripped for each detection target area based on a difference or comparison between the measurement value and the capacitance threshold. When the driver grips the steering wheel in any of the plurality of detection target areas, the measurement value of the measuring device that sets the gripped area as the detection target area increases, and thus the difference between the measurement value and the capacitance threshold also increases. Therefore, in the steering device, the presence or absence of gripping can be determined for each detection target area based on the difference or comparison between the measurement value and the capacitance threshold. When the environmental conditions around the steering wheel change, the capacitance measurement values ​​by these measuring devices also change, so in order to suppress erroneous determinations due to changes in the environmental conditions, it is necessary to appropriately correct the capacitance threshold in accordance with the changes in the environmental conditions. In addition, since the plurality of electrode portions are in approximately the same environment, the tendency of changes in the measurement values ​​of each measuring device due to changes in the environmental conditions is similar. Therefore, the capacity threshold setting unit judges whether or not the capacity threshold needs to be corrected based on the degree of similarity of the change trends of the measured values ​​of the multiple measuring devices, thereby separating the cause of the change in the measured value into a change in the driver's hand position and a change in the environmental condition, and correcting the capacity threshold at an appropriate timing. Therefore, according to the present invention, the difference between the measured value and the capacity threshold can be kept constant regardless of the change in the environmental condition around the steering wheel, so that erroneous judgment due to the change in the environmental condition around the steering wheel can be prevented, which can contribute to the development of a sustainable transportation system. In addition, since the present invention does not require a sensor for detecting the environmental condition around the steering wheel, erroneous judgment can be prevented with a simpler configuration than the conventional one.

[0016] (2) The capacity threshold setting unit calculates a similarity that increases or decreases according to the degree of similarity, and if this similarity is higher than a similarity standard, i.e., if the trends of changes in the measured values ​​of each of the multiple measuring devices are similar, the capacity threshold is corrected assuming that the changes in these measured values ​​are due to changes in the environmental conditions, and if the similarity is lower than the similarity standard, the capacity threshold is maintained constant assuming that the changes in these measured values ​​are due to changes in the position of the driver's hands. Thus, according to the present invention, since only the fluctuations due to changes in the environmental conditions can be removed from the difference between the measured values ​​and the capacity threshold, erroneous judgment due to changes in the environmental conditions around the steering wheel can be prevented.

[0017] (3) The capacitance threshold setting unit calculates the similarity by comparing the slopes of the measured values ​​of the multiple measurement devices. Therefore, according to the present invention, the similarity of the change trends of the measured values ​​can be calculated by a simple calculation.

[0018] (4) The capacitance threshold setting unit calculates the similarity by comparing the amount of change in the measured values ​​of the multiple measurement devices over a predetermined judgment period. Therefore, according to the present invention, the similarity of the change trends of each measured value can be calculated by a simple calculation.

[0019] (5) The capacity threshold setting unit corrects the capacity threshold to the increasing side when the similarity of the change trends of the multiple measured values ​​is higher than the similarity standard and all of the multiple measured values ​​are increasing, and corrects the capacity threshold to the decreasing side when the similarity of the change trends of the multiple measured values ​​is higher than the similarity standard and all of the multiple measured values ​​are decreasing. This makes it possible to keep the difference between the measured values ​​and the capacity threshold constant regardless of changes in the environmental state, thereby preventing erroneous judgments.

[0020] (6) In the present invention, the determination unit determines whether the steering wheel is being gripped based on a capacitance difference value obtained by subtracting a reference value, which is a capacitance threshold value, from a measured value. Therefore, according to the present invention, the capacitance difference value can be kept constant regardless of changes in the environmental conditions around the steering wheel, so that it is possible to accurately determine whether the steering wheel is being gripped.

[0021] (7) In the present invention, the determination unit determines whether the steering wheel is being gripped by comparing the measurement value with a grip determination threshold, which is a capacitance threshold. Therefore, according to the present invention, the difference between the capacitance difference value and the grip determination threshold can be kept constant regardless of changes in the environmental conditions around the steering wheel, so that it is possible to accurately determine whether the steering wheel is being gripped. [Brief description of the drawings]

[0022] [Figure 1] 1 is a diagram showing a configuration of a steering device according to an embodiment of the present invention; [Diagram 2] FIG. 4 is a diagram showing the circuit configuration of a right measurement circuit. [Diagram 3] 10 is a flowchart showing a specific procedure of a reference value setting process for setting a reference value. [Figure 4] 13 is a time chart showing the determination results as to whether or not a grip is present when a reference value is set by the reference value setting process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A steering device according to an embodiment of the present invention will be described below with reference to the drawings.

[0024] 1 is a diagram showing the configuration of a steering device 1 according to this embodiment. The steering device 1 is mounted on a vehicle (not shown). The steering device 1 includes a steering wheel 2 that receives vehicle steering operations and auxiliary device operations by a driver, a steering shaft 3 that supports the steering wheel 2, and a grip sensor unit 8 that determines whether or not the steering wheel 2 is being gripped by the driver based on a measurement result of the capacitance of a plurality of electrodes provided on the steering wheel 2.

[0025] The steering wheel 2 comprises a circular rim portion 20 which can be gripped by the driver, a hub portion 23 provided on the inside of the rim portion 20, and three spoke portions 25L, 25R, 25D which extend radially from the hub portion 23 and are connected to the rim inner portion 21 of the rim portion 20.

[0026] The hub portion 23 is disk-shaped and is provided, for example, at the center of the rim portion 20 as seen by the driver, constituting the center of the steering wheel 2. A steering shaft 3 that axially supports the steering wheel 2 is connected to the back side of the hub portion 23 as seen by the driver. The steering shaft 3 is an axial connecting member that connects a core metal that is the skeleton of the hub portion 23 to a steering mechanism that constitutes part of the vehicle body (not shown). Therefore, the steering torque generated by the driver rotating the steering wheel 2 is transmitted by this steering shaft 3 to the steering mechanism (not shown).

[0027] The rim portion 20 and the hub portion 23 are connected by three spoke portions 25L, 25R, and 25D. The left spoke portion 25L extends horizontally and connects the left portion of the hub portion 23 as seen by the driver to the left portion of the rim inner circumferential portion 21 as seen by the driver. The right spoke portion 25R extends horizontally and parallel to the left spoke portion 25L and connects the right portion of the hub portion 23 as seen by the driver to the right portion of the rim inner circumferential portion 21 as seen by the driver. The lower spoke portion 25D extends perpendicularly to the spoke portions 25L and 25R and vertically and connects the lower portion of the hub portion 23 as seen by the driver to the lower portion of the rim inner circumferential portion 21 as seen by the driver.

[0028] As described above, the rim portion 20 is annular when viewed from the driver, and the driver can grip the entire circumference of the rim portion 20. The rim portion 20 is provided with a plurality of electrode portions 40, 50 (two in the example of FIG. 1) of the grip sensor unit 8 described below. In this embodiment, a case where a plurality of electrode portions 40, 50 are provided on the rim portion 20 of the steering wheel 2 is described, but the present invention is not limited to this. The plurality of electrode portions may be provided on the hub portion 23, the spoke portions 25L, 25R, 25D, etc., in addition to the rim portion 20. In this embodiment, a case where two electrode portions 40, 50 are provided on the steering wheel 2 is described, but the present invention is not limited to this. The number of electrode portions provided on the steering wheel 2 may be three or more.

[0029] The left spoke portion 25L and the right spoke portion 25R are provided with a left accessory operation console unit 27L and a right accessory operation console unit 27R, respectively, that accepts accessory operations by the driver to operate vehicle accessories (not shown, for example, an audio device, a car navigation device, etc.) The driver can operate the vehicle accessories by operating a plurality of switches provided on these accessory operation console units 27L and 27R with his / her fingers.

[0030] In the following description, the positions of the rim portion 20, the rim inner periphery 21, the hub portion 23, and the steering shaft 3, which are substantially circular as viewed from the driver, and the orientations of the spoke portions 25L, 25R, and 25D may be expressed as angles [°] in a clockwise direction with the steering shaft 3 as the center and the upper end portion 20C of the rim portion 20 as viewed from the driver as the reference point. That is, the right spoke portion 25R extends along a 90° direction and connects the 90° portions of the hub portion 23 and the rim inner periphery 21. The lower spoke portion 25D extends along a 180° direction and connects the 180° portions of the hub portion 23 and the rim inner periphery 21. The left spoke portion 25L extends along a 270° direction and connects the 270° portions of the hub portion 23 and the rim inner periphery 21.

[0031] The grip sensor unit 8 includes multiple (in this embodiment, two) proximity sensors 4, 5, each with a different detection target area, and a grip determination device 80 that determines whether or not the driver is gripping the steering wheel 2 and the gripping position based on the measurement results of these proximity sensors 4, 5.

[0032] The right proximity sensor 4 includes a right electrode section 40 provided on the rim section 20 and a right measurement circuit 42 electrically connected to the right electrode section 40. The right electrode section 40 is arc-shaped extending along the rim section 20 and is conductive. The right electrode section 40 is provided inside the rim section 20. The right electrode section 40 is arranged in a range of about 180° between 0° and 180° of the rim section 20 (i.e., a range that the driver can hold with his right hand mainly when driving straight). In the following, the area of ​​the rim section 20 where the right electrode section 40 is arranged is also referred to as the right grip section 20R. The right measurement circuit 42 is connected to the right electrode section 40 via a wiring 41. The right measurement circuit 42 measures the capacitance between the right electrode section 40 and the ground as a value that increases or decreases depending on the distance between the arrangement position of the right electrode section 40 and the human body. The closer the distance between the arrangement position of the right electrode section 40 and the human body, the greater the capacitance between the right electrode section 40 and the ground. The capacitance measurement value Ch_R_d by the right measurement circuit 42 is transmitted to the grip determination device 80.

[0033] FIG. 2 is a diagram showing the circuit configuration of the right measurement circuit 42. The right measurement circuit 42 includes a pulse power supply 43, an amplifier 44, a first switch 45, a second switch 46, a charging capacitor 47, and a capacitance measurement unit 48. In Fig. 2, the capacitance between the right electrode unit 40 and the ground (e.g., the vehicle body) is illustrated as being divided into a capacitance Ch formed by the human body H including the driver's hands operating the steering wheel 2, and a floating capacitance Ce formed by a floating capacitor E such as wiring and components excluding the human body H.

[0034] As shown in FIG. 2, the pulse power supply 43 and the amplifier 44 are connected in series. The second switch 46 and the charging capacitor 47 are connected in parallel. The series circuit consisting of the pulse power supply 43 and the amplifier 44 and the parallel circuit consisting of the second switch 46 and the charging capacitor 47 are connected via the first switch 45. The output terminal of the amplifier 44 and the first switch 45 are connected to the right electrode section 40 via the wiring 41. Therefore, the pulse power supply 43 is connected to the right electrode section 40 via the amplifier 44 and the wiring 41. In addition, the second switch 46 and the charging capacitor 47 are connected to the right electrode section 40 via the first switch 45 and the wiring 41, respectively.

[0035] In response to a command from the grip determination device 80, the pulse power supply 43 supplies a pulse voltage Vs of a predetermined frequency and a predetermined voltage to the amplifier 44. The amplifier 44 amplifies the pulse voltage Vs supplied from the pulse power supply 43 and applies it to the right electrode portion 40.

[0036] The second switch 46 is a switching element that is turned on / off by a drive circuit (not shown). The drive circuit for the second switch 46 turns off the second switch 46 until the voltage VCref of the charging capacitor 47 reaches a predetermined threshold Vthr, for example, and turns on the second switch 46 after the voltage VCref reaches the threshold Vthr, thereby discharging the charge stored in the charging capacitor 47.

[0037] The first switch 45 is a switching element that is turned on / off by a drive circuit (not shown). The drive circuit for the first switch 45 turns off the first switch 45 in response to the rise of the pulse voltage Vs of the pulse power supply 43. As a result, the pulse voltage supplied from the pulse power supply 43 and the amplifier 44 is applied to the right electrode unit 40, and electric charge moves through the path indicated by the arrow 2a in FIG. 2, charging the human body H and the floating capacitor E.

[0038] Furthermore, the drive circuit of the first switch 45 turns on the first switch 45 in response to the falling edge of the pulse voltage Vs of the pulse power supply 43. This connects the human body H and the floating capacitor E to the charging capacitor 47, and electric charge moves from the human body H and the floating capacitor E to the charging capacitor 47 via the path indicated by the arrow 2b in Fig. 2, charging the charging capacitor 47. This causes the voltage VCref of the charging capacitor 47 to rise.

[0039] Therefore, when a pulse voltage is applied to the right electrode section 40 by the pulse power supply 43 and the amplifier 44, charging and discharging of the human body H and the floating capacitor E are repeated alternately, and the voltage VCref of the charging capacitor 47 gradually increases. At this time, the time until the voltage VCref of the charging capacitor 47 reaches the threshold value Vthr (or the number of pulses of the pulse power supply 43) varies depending on the capacitance Ch formed by the human body H, that is, the distance between the right electrode section 40 and the driver's body. That is, when a part of the driver's body is in contact with or close to the arrangement position of the right electrode section 40 of the rim section 20 and the capacitance Ch is high, the time until the voltage VCref of the charging capacitor 47 reaches the threshold value Vthr is short, and when a part of the driver's body is away from the arrangement position of the right electrode section 40 and the capacitance Ch is low, the time until the voltage VCref of the charging capacitor 47 reaches the threshold value Vthr is long.

[0040] The capacitance measuring unit 48 measures the time and the number of pulses until the voltage VCref of the charging capacitor 47 reaches the threshold value Vthr, and based on this measurement result, indirectly measures the capacitance Ch formed by the human body H present in the vicinity of the right electrode unit 40. The capacitance measuring unit 48 transmits the measurement value Ch_R_d of the capacitance Ch obtained by the above procedure to the grip determination device 80.

[0041] The left proximity sensor 5 includes a left electrode section 50 provided on the rim section 20 and a left measurement circuit 52 electrically connected to the left electrode section 50. The left electrode section 50 is arc-shaped extending along the rim section 20 and is conductive. The left electrode section 50 is provided inside the rim section 20. The left electrode section 50 is arranged in a range of about 180° between 180° and 360° of the rim section 20 (i.e., a range that the driver can hold with his left hand mainly when driving straight). In the following, the area of ​​the rim section 20 where the left electrode section 50 is arranged is also referred to as the left grip section 20L. The left measurement circuit 52 is connected to the left electrode section 50 via a wiring 51. The left measurement circuit 52 measures the capacitance between the left electrode section 50 and the ground as a value that increases or decreases according to the distance between the arrangement position of the left electrode section 50 and the human body. The closer the distance between the arrangement position of the left electrode section 50 and the human body, the greater the capacitance between the left electrode section 50 and the ground. The capacitance measurement value Ch_L_d by the left measurement circuit 52 is transmitted to the grip determination device 80. Note that the circuit configuration of the left measurement circuit 52 is almost the same as the circuit configuration of the right measurement circuit 42 described with reference to Fig. 2, so a detailed description thereof will be omitted.

[0042] As described above, the right electrode portion 40 of the right proximity sensor 4 is provided in a position closer to the right grip portion 20R than the other electrode portions 50. Therefore, the right proximity sensor 4 has the right grip portion 20R of the rim portion 20 as its detection target area. The left electrode portion 50 of the left proximity sensor 5 is provided in a position closer to the left grip portion 20L than the other electrode portions 40. Therefore, the left proximity sensor 5 has the left grip portion 20L of the rim portion 20 as its detection target area. As described above, a detection target area is defined for each of the proximity sensors 4, 5 on the rim portion 20 of the steering wheel 2. The grip determination device 80 acquires whether or not the rim portion 20 is being gripped by the driver and the grip position based on the measured values ​​Ch_R_d, Ch_L_d of the two proximity sensors 4, 5 having different detection target areas on the rim portion 20 as described above.

[0043] The gripping determination device 80 includes a determination unit 81 that determines whether or not the driver is gripping each detection target area based on the difference or comparison between the measurement values ​​Ch_R_d, Ch_L_d of each proximity sensor 4, 5 and a capacitance threshold for capacitance such as a reference value Ch_0 or a gripping determination threshold Ch_th, and a capacitance threshold setting unit 82 that sequentially sets a capacitance threshold to be referenced when determining whether or not the object is being gripped in the determination unit 81 based on the measurement values ​​Ch_R_d, Ch_L_d.

[0044] The determination unit 81 calculates a capacitance difference value ΔCh_R by subtracting a reference value Ch_0 from the measurement value Ch_R_d of the right proximity sensor 4, and further compares the magnitude of this capacitance difference value ΔCh_R with the grip determination threshold value Ch_th to determine whether or not the right grip portion 20R of the steering wheel 2, which is the detection target area of ​​the right proximity sensor 4, is gripped. More specifically, when the difference (ΔCh_R-Ch_th) between the capacitance difference value ΔCh_R and the grip determination threshold value Ch_th is 0 or positive, that is, when the following formula (1-1) is established, the determination unit 81 determines that the steering wheel 2 is gripped by the driver at the right grip portion 20R of the rim portion 20. Also, when the difference (ΔCh_R-Ch_th) between the capacitance difference value ΔCh_R and the grip determination threshold value Ch_th is negative, that is, when the following formula (1-2) is established, the determination unit 81 determines that the steering wheel 2 is not gripped by the driver at the right grip 20R of the rim portion 20. Ch_R_d-Ch_0≧Ch_th (1-1) Ch_R_d-Ch_0 <Ch_th (1-2)

[0045] The determination unit 81 calculates a capacitance difference value ΔCh_L by subtracting a reference value Ch_0 from the measurement value Ch_L_d of the left proximity sensor 5, and further compares the magnitude of this capacitance difference value ΔCh_L with the grip determination threshold value Ch_th to determine whether or not the left grip portion 20L of the steering wheel 2, which is the detection target area of ​​the left proximity sensor 5, is gripped. More specifically, when the difference (ΔCh_L-Ch_th) between the capacitance difference value ΔCh_L and the grip determination threshold value Ch_th is 0 or positive, that is, when the following formula (2-1) is established, the determination unit 81 determines that the steering wheel 2 is gripped by the driver at the left grip portion 20L of the rim portion 20. Also, when the difference (ΔCh_L-Ch_th) between the capacitance difference value ΔCh_L and the grip determination threshold value Ch_th is negative, that is, when the following formula (2-2) is established, the determination unit 81 determines that the steering wheel 2 is not gripped by the driver at the left grip 20L of the rim portion 20. Ch_R_d-Ch_0≧Ch_th (2-1) Ch_R_d-Ch_0 <Ch_th (2-2)

[0046] Here, the reference value Ch_0 corresponds to the capacitance value of the electrode units 40, 50 when the driver's hands are in a position sufficiently distant from the installation positions of the electrode units 40, 50 on the steering wheel 2, and is a positive value. Therefore, the capacitance difference values ​​ΔCh_R (=Ch_R_d-Ch_0) and ΔCh_L (=Ch_L_d-Ch_0) increase as the driver's hands approach the installation positions of the electrode units 40, 50. For this reference value Ch_0, a predetermined fixed value or a value sequentially set by the capacitance threshold setting unit 82 is used.

[0047] The grip determination threshold Ch_th is a threshold, which is a positive value, set for the capacitance difference values ​​ΔCh_R and ΔCh_L in order to determine whether or not the driver's hands are sufficiently close to the installation positions of the electrode units 40 and 50, i.e., whether or not the driver is gripping the steering wheel 2. For this grip determination threshold Ch_th, a predetermined fixed value or a value successively set by the capacitance threshold setting unit 82 is used.

[0048] Here, the measured values ​​Ch_R_d, Ch_L_d and the capacitance difference values ​​ΔCh_R, ΔCh_L vary depending on the environmental conditions such as the temperature and humidity around the installation positions of the electrode units 40, 50 as well as the distance between the driver's hand and the installation positions of the electrode units 40, 50. More specifically, the measured values ​​Ch_R_d, Ch_L_d and the capacitance difference values ​​ΔCh_R, ΔCh_L tend to increase as the temperature increases and as the humidity increases. For this reason, if the capacitance thresholds such as the reference value Ch_0 and the grip determination threshold Ch_th are fixed values ​​that do not depend on changes in the environmental conditions, the determination unit 81 may make an erroneous determination. Therefore, the capacity threshold setting unit 82 changes both or either of the reference value Ch_0 and the grip determination threshold Ch_th depending on the changes in the environmental conditions. In this embodiment, the capacity threshold setting unit 82 changes the reference value Ch_0 depending on the changes in the environmental conditions and sets the grip determination threshold Ch_th to a fixed value, but the present invention is not limited to this.

[0049] 3 is a flowchart showing a specific procedure of a reference value setting process for setting the reference value Ch_0. The reference value setting process shown in FIG.

[0050] First, in step ST1, the capacitance threshold setting unit 82 acquires a right measurement value Ch_R_d(n) of the capacitance of the right electrode unit 40 by the right proximity sensor 4 and a left measurement value Ch_L_d(n) of the capacitance of the left electrode unit 50 by the left proximity sensor 5, and proceeds to step ST2. Here, the symbol (n) is a symbol indicating discretized time, and indicates that the data is acquired or calculated by processing in the nth control cycle. In other words, if the symbol (n) is data acquired or calculated at the current control timing, the symbol (n-1) indicates that the data is acquired or calculated at the previous control timing (i.e., Δt ago). In the following description, the symbol (n) indicating time will be omitted as appropriate.

[0051] In step ST2, the capacity threshold setting unit 82 performs a filter process to remove high-frequency noise from each of the measured values ​​Ch_R_d(n) and Ch_L_d(n) acquired in step ST1, and then proceeds to step ST3. In the following, a value obtained by performing a filter process on the right measured value Ch_R_d(n) is called a right filter value and is denoted as "Ch_R_f(n)". In the following, a value obtained by performing a filter process on the left measured value Ch_L_d(n) is called a left filter value and is denoted as "Ch_L_f(n)". In this embodiment, the capacity threshold setting unit 82 performs a weighted moving average process as shown in the following formulas (3) and (4) as a filter process on each of the measured values ​​Ch_R_d(n) and Ch_L_d(n), but the present invention is not limited to this. In the following formula, "w" is a weight and is an arbitrary positive value greater than 0. Ch_R_f(n) = (Ch_R_d(n)+w×Ch_R_f(n-1)) / (1+w) (3) Ch_L_f(n) = (Ch_L_d(n)+w×Ch_L_f(n-1)) / (1+w) (4)

[0052] In step ST3, the capacity threshold setting unit 82 calculates the slope a_R(n) of the right filter value Ch_R_f(n) as a parameter representing the change tendency of the right filter value Ch_R_f(n) of the right measurement value, and proceeds to step ST4. More specifically, the capacity threshold setting unit 82 calculates the slope a_R(n) of the right filter value Ch_R_f(n) by dividing the change amount (Ch_R_f(n)-Ch_R_f(n-1)) of the right filter value in a judgment period of one cycle from the n-1th cycle to the nth cycle by the length (Δt) of the judgment period, as shown in the following formula (5). That is, when the right filter value Ch_R_f(n) is on the increase, the slope a_R(n) is a positive value, and when it is on the decrease, the slope a_R(n) is a negative value. a_R(n)= (Ch_R_f(n)-Ch_R_f(n-1)) / Δt (5)

[0053] In step ST4, the capacity threshold setting unit 82 calculates the slope a_L(n) of the left filter value Ch_L_f(n) as a parameter representing the change tendency of the left filter value Ch_L_f(n) of the left measurement value, and proceeds to step ST5. More specifically, the capacity threshold setting unit 82 calculates the slope a_L(n) of the left filter value Ch_L_f(n) by dividing the amount of change in the left filter value (Ch_L_f(n)-Ch_L_f(n-1)) during a judgment period of one cycle from the n-1th cycle to the nth cycle by the length (Δt) of the judgment period, as shown in the following formula (6). That is, when the left filter value Ch_L_f(n) is on the increase, the slope a_L(n) is a positive value, and when it is on the decrease, the slope a_L(n) is a negative value. a_L(n)= (Ch_L_f(n)-Ch_L_f(n-1)) / Δt (6)

[0054] In step ST5, the capacity threshold setting unit 82 calculates a similarity S(n) that increases or decreases according to the degree of similarity between the change tendency of the right filter value Ch_R_f(n) and the change tendency of the left filter value Ch_L_f(n) by comparing the calculated gradients a_R(n) and a_L(n), and then proceeds to step ST6. More specifically, the capacity threshold setting unit 82 calculates the similarity S(n) of the change tendency of the filter values ​​Ch_R_f(n) and Ch_L_f(n) according to, for example, the following formula (7). In the following formula (7), "a0" is a predetermined positive coefficient. The similarity S(n) defined by the following formula (7) becomes larger as the gradients a_R(n) and a_L(n) representing the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) become closer to each other, that is, as the degree of similarity of the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) becomes higher. Furthermore, the similarity S(n) becomes smaller as the gradients a_R(n), a_L(n) representing the change trends of the filter values ​​Ch_R_f(n), Ch_L_f(n) become more distant from each other, i.e., as the similarity of the change trends of the filter values ​​Ch_R_f(n), Ch_L_f(n) becomes lower. S(n)=a0 / (|a_R(n)-a_L(n)|) (7)

[0055] In step ST6, the capacity threshold setting unit 82 judges whether the slope a_R(n) of the right filter value Ch_R_f(n) and the slope a_L(n) of the left filter value Ch_L_f(n) have the same sign. If the judgment result in step ST6 is YES, the capacity threshold setting unit 82 proceeds to step ST7. In step ST7, the capacity threshold setting unit 82 judges whether the similarity S(n) is higher than a predetermined positive similarity standard S_th (S(n)>S_th).

[0056] If the determination result in step ST6 is NO or if the determination result in step ST7 is NO, that is, if the slopes a_R(n) and a_L(n) have opposite signs or the similarity S(n) is equal to or smaller than the similarity standard S_th, the capacity threshold setting unit 82 determines that the change in each of the filter values ​​Ch_R_f(n) and Ch_L_f(n) during the determination period from the n-1th cycle to the nth cycle is due to a change in the position of the driver's hands. In this case, the capacity threshold setting unit 82 determines that it is not necessary to correct the standard value Ch_0(n) and proceeds to step ST8.

[0057] In step ST8, the capacity threshold setting unit 82 sets the reference value Ch_0(n) to a value equal to the reference value Ch_0(n-1) in the previous cycle as shown in the following formula (8), and returns to step ST1. That is, the capacity threshold setting unit 82 maintains the reference value Ch_0(n) constant. The initial value Ch_0(0) of the reference value is set to, for example, a predetermined value or a value equal to the smaller of the right measurement value Ch_R_d(0) and the left measurement value Ch_L_d(0) immediately after the start of the reference value setting process shown in FIG. 3. Ch_0(n)=Ch_0(n-1) (8)

[0058] If the result of the determination in step ST7 is YES, i.e., if the slopes a_R(n) and a_L(n) have the same sign and the similarity S(n) is higher than the similarity standard S_th, the capacity threshold setting unit 82 determines that the changes in the filter values ​​Ch_R_f(n) and Ch_L_f(n) during the time Δt from the n-1th period to the nth period are due to changes in the environmental state. In this case, the capacity threshold setting unit 82 determines that the reference value Ch_0(n) needs to be corrected in response to the change in the environmental state, and proceeds to step ST9.

[0059] In step ST9, the capacity threshold setting unit 82 calculates a correction value dCh_0(n) based on at least one of the slopes a_R(n) and a_L(n), and proceeds to step ST10. More specifically, the capacity threshold setting unit 82 calculates a correction value dCh_0(n) according to the change in the environmental state during the time Δt by multiplying the slope a_R(n) by the time Δt, for example, as shown in the following formula (9). Therefore, when both the filter values ​​Ch_R_f(n) and Ch_L_f(n) tend to increase, the correction value dCh_0(n) is a positive value. Also, when both the filter values ​​Ch_R_f(n) and Ch_L_f(n) tend to decrease, the correction value dCh_0(n) is a negative value. dCh_0(n)=a_R(n)×Δt (9)

[0060] In addition, since the slopes a_R(n) and a_L(n) have the same sign and are approximately equal, the correction value dCh_0(n) may be calculated by multiplying the slope a_L(n) by the time Δt, or the correction value dCh_0(n) may be calculated by multiplying the average value of the slopes a_R(n) and a_L(n) by the time Δt.

[0061] In step ST10, the capacity threshold setting unit 82 adds the correction value dCh_0(n) calculated in step ST9 to the reference value Ch_0(n-1) in the previous cycle as shown in the following formula (10), sets the result as the reference value Ch_0(n), and returns to step ST1. That is, when the filter values ​​Ch_R_f(n), Ch_L_f(n) are both increasing, the capacity threshold setting unit 82 corrects the reference value Ch_0(n) to the increasing side, and when the filter values ​​Ch_R_f(n), Ch_L_f(n) are both decreasing, the capacity threshold setting unit 82 corrects the reference value Ch_0(n) to the decreasing side. Ch_0(n)=Ch_0(n-1)+dCh_0(n) (10)

[0062] Fig. 4 is a time chart of the determination result of the presence or absence of gripping of the steering wheel 2 when the reference value Ch_0 is set by the above-mentioned reference value setting process. The upper part of Fig. 4 shows the right measurement value Ch_R_d (solid line), the left measurement value Ch_L_d (dash line), and the reference value Ch_0 (dashed line), the middle part shows the right capacitance difference value ΔCh_R (solid line), the left capacitance difference value ΔCh_L (dash line), and the grip determination threshold value Ch_th (dashed line), and the lower part shows the determination result of gripping at the right grip portion 20R and the left grip portion 20L. In Fig. 4, each filter value Ch_R_f, Ch_L_f is assumed to be substantially equal to each measurement value Ch_R_d, Ch_L_d, and is not shown.

[0063] First, between times t0 and t1, the driver grips the left grip portion 20L with his left hand, causing the left measurement value Ch_L_d to rise sharply. Therefore, between times t0 and t1, the left capacitance difference value ΔCh_L exceeds the grip determination threshold value Ch_th, and the determination unit 81 determines that the steering wheel 2 is gripped by the left grip portion 20L thereafter. Between times t0 and t1, the right measurement value Ch_R_d is substantially constant, and the right capacitance difference value ΔCh_R is substantially constant at a value less than the grip determination threshold value Ch_th. Therefore, between times t0 and t1, the determination unit 81 determines that the right grip portion 20R is not gripped. Also, the similarity S of the change tendency of each measurement value Ch_R_d, Ch_L_d between times t0 and t1 is less than the similarity reference S_th, so the capacity threshold setting unit 82 maintains the reference value Ch_0 constant (see step ST8 in FIG. 3).

[0064] Next, between times t2 and t3, the steering wheel 2 is held only by the left grip portion 20L, and the environmental conditions around the electrodes 40 and 50 change, so that the measured values ​​Ch_R_d and Ch_L_d increase at approximately the same rate. Therefore, the similarity S of the change tendency of the measured values ​​Ch_R_d and Ch_L_d between times t2 and t3 is equal to or greater than the similarity standard S_th, so that the capacitance threshold setting unit 82 corrects the reference value Ch_0 to the increasing side in accordance with the increase of the measured values ​​Ch_R_d and Ch_L_d (see steps ST9 and ST10 in FIG. 3). Therefore, between times t2 and t3, the capacitance difference values ​​ΔCh_R and ΔCh_L are maintained approximately constant regardless of the change in the environmental conditions. In particular, between times t2 and t3, the right capacitance difference value ΔCh_R can be maintained constant at a value less than the grip determination threshold value Ch_th by correcting the reference value Ch_0 to the increasing side in accordance with the increase of the right measured value Ch_R_d. Therefore, the determination unit 81 can prevent erroneous determination that the right grip portion 20R is gripped between times t2 and t3.

[0065] Next, between times t4 and t6, the right measurement value Ch_R_d rises sharply as the driver grips the right grip portion 20R with his right hand. Therefore, at time t5, the right capacitance difference value ΔCh_R exceeds the grip determination threshold value Ch_th, and the determination unit 81 determines that the steering wheel 2 is gripped by the left and right grip portions 20R and 20L from this time on. Also, between times t4 and t6, the driver continues to grip the left grip portion 20L, and the left measurement value Ch_L_d remains almost constant. Therefore, the similarity S of the change tendency of each measurement value Ch_R_d, Ch_L_d between times t4 and t6 is less than the similarity reference S_th, and the capacity threshold setting unit 82 maintains the reference value Ch_0 constant (see step ST8 in FIG. 3).

[0066] Next, between times t6 and t7, when the steering wheel 2 is held by both the left and right grips 20R and 20L, the environmental conditions around the electrodes 40 and 50 change, causing the measured values ​​Ch_R_d and Ch_L_d to rise at approximately the same gradient. Therefore, the similarity S of the change tendency of the measured values ​​Ch_R_d and Ch_L_d between times t6 and t7 is equal to or greater than the similarity reference S_th, so the capacitance threshold setting unit 82 corrects the reference value Ch_0 to the increasing side in accordance with the increase of the measured values ​​Ch_R_d and Ch_L_d (see steps ST9 and ST10 in FIG. 3). Therefore, between times t6 and t7, the capacitance difference values ​​ΔCh_R and ΔCh_L are approximately constant regardless of the change in the environmental conditions.

[0067] Next, between times t7 and t9, the driver removes his / her right hand from the right grip portion 20R, causing the right measurement value Ch_R_d to drop sharply. Therefore, at time t8, the right capacitance difference value ΔCh_R falls below the grip determination threshold value Ch_th. Therefore, after time t8, the determination unit 81 determines that the steering wheel 2 is not gripped by the right grip portion 20R. Also, between times t7 and t8, the driver continues to grip the left grip portion 20L, so the left measurement value Ch_L_d remains almost constant. Therefore, the similarity S of the change trends of the measurement values ​​Ch_R_d and Ch_L_d between times t7 and t9 is less than the similarity reference S_th, so the capacity threshold setting unit 82 maintains the reference value Ch_0 constant (see step ST8 in FIG. 3).

[0068] As described above, the capacity threshold setting unit 82 can change the reference value Ch_0 in accordance with fluctuations in the environmental conditions around the electrode units 40, 50 by increasing or decreasing the reference value Ch_0 in accordance with increases or decreases in each of the measurement values ​​Ch_R_d, Ch_L_d only during periods in which the similarity S of the change trends of each of the measurement values ​​Ch_R_d, Ch_L_d is higher than the similarity standard S_th (in the example of Figure 4, the periods from time t2 to t3 and from time t6 to t7).

[0069] As described above, in this embodiment, the necessity of correction of the reference value Ch_0(n) is judged based on the degree of similarity of the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) during the judgment period of one control cycle Δt from the n-1th cycle to the nth cycle, but the length of the judgment period is not limited to this. The judgment period may be several cycles Δt×m (m is an integer of 2 or more).

[0070] 3, the need to correct the reference value Ch_0(n) is determined based on the degree of similarity in the change trends of the filter values ​​Ch_R_f(n) and Ch_L_f(n), but the present invention is not limited to this. The capacity threshold setting unit 82 may determine the need to correct the reference value Ch_0(n) based on the degree of similarity in the change trends of the measurement values ​​Ch_R_d(n) and Ch_L_d(n) before the filter processing is performed.

[0071] In the present embodiment, the determination unit 81 determines whether the driver is gripping the right grip portion 20R of the steering wheel 2 based on the above formulas (1-1) and (1-2), but the present invention is not limited thereto. The determination unit 81 may determine whether the driver is gripping the steering wheel 2 based on the following formulas (11-1) and (11-2) which are equivalent to the above formulas (1-1) and (1-2). That is, the determination unit 81 may determine that the driver is gripping the steering wheel 2 at the right grip portion 20R when the sum of the grip determination threshold value Ch_th and the reference value Ch_0 is equal to or less than the measured value Ch_R_d, that is, when the following formula (11-1) is satisfied, and may determine that the driver is gripping the steering wheel 2 at the right grip portion 20R when the sum of the grip determination threshold value Ch_th and the reference value Ch_0 is greater than the measured value Ch_R_d, that is, when the following formula (11-2) is satisfied. The same applies to the determination of whether or not the left grip portion 20L is being gripped, so a detailed description thereof will be omitted. Ch_R_d≧Ch_th+Ch_0 (11-1) Ch_R_d <Ch_th+Ch_0 (11-2)

[0072] The steering device 1 according to this embodiment provides the following advantages. (1) The grip determination device 80 of the steering device 1 includes a plurality of proximity sensors 4, 5 whose electrode units 40, 50 are installed at different positions relative to the steering wheel 2, and the grip determination device 80 determines whether the steering wheel 2 is gripped based on the measurement values ​​Ch_R_d, Ch_L_d of the plurality of proximity sensors 4, 5. A detection target area is defined for each of the proximity sensors 4, 5 on the steering wheel 2, and the grip determination device 80 includes a capacitance threshold setting unit 82 that sets a reference value Ch_0 for the capacitance of the electrode units 40, 50, and a determination unit 81 that determines whether the steering wheel 2 is gripped for each detection target area based on the difference between the measurement values ​​Ch_R_d, Ch_L_d and the reference value Ch_0. When the driver grips the steering wheel 2 in any of the plurality of detection target areas, the measurement values ​​Ch_R_d, Ch_L_d of the proximity sensors 4, 5 whose detection target area is the gripped area increase, and the difference between the measurement values ​​Ch_R_d, Ch_L_d and the reference value Ch_0 also increases. Therefore, in the steering device 1, the presence or absence of gripping can be determined for each detection target area based on the difference between the measured values ​​Ch_R_d, Ch_L_d and the reference value Ch_0. Here, when the environmental condition around the steering wheel 2 changes, the measured capacitance values ​​Ch_R_d, Ch_L_d by these proximity sensors 4, 5 also change. Therefore, in order to suppress erroneous determination due to the change in the environmental condition, it is necessary to appropriately correct the reference value Ch_0 according to the change in the environmental condition. In addition, since the multiple electrode units 40, 50 are in almost the same environment, the measured values ​​Ch_R_d, Ch_L_d of each proximity sensor 4, 5 due to the change in the environmental condition tend to be similar. Therefore, the capacitance threshold setting unit 82 determines whether or not the reference value Ch_0 needs to be corrected based on the degree of similarity in the change tendency of the filter values ​​Ch_R_f, Ch_L_f of the measured values ​​of the multiple proximity sensors 4, 5, and thereby can distinguish the cause of the change in the measured values ​​Ch_R_d, Ch_L_d into those due to the change in the position of the driver's hands and those due to the change in the environmental condition, and can correct the reference value Ch_0 at an appropriate timing.Therefore, according to the steering device 1, the differences between the measured values ​​Ch_R_d, Ch_L_d and the reference value Ch_0 can be kept constant regardless of changes in the environmental conditions around the steering wheel 2, thereby preventing erroneous determination due to fluctuations in the environmental conditions around the steering wheel 2 and ultimately contributing to the development of a sustainable transportation system. Also, with the steering device 1, there is no need to provide a sensor for detecting the environmental conditions around the steering wheel 2, so erroneous determination can be prevented with a simpler configuration than before.

[0073] (2) The capacitance threshold setting unit 82 calculates a similarity S(n) that increases or decreases according to the degree of similarity of the change trends of the filter values ​​Ch_R_f(n) and Ch_L_f(n), and if this similarity S(n) is higher than the similarity standard S_th, that is, if the change trends of the filter values ​​Ch_R_f(n) and Ch_L_f(n) of the multiple proximity sensors 4 and 5 are similar, the change in these filter values ​​Ch_R_f(n) and Ch_L_f(n) is considered to be due to a change in the environmental condition, and corrects the reference value Ch_0, and if the similarity S(n) is lower than the similarity standard S_th, the change in these filter values ​​Ch_R_f(n) and Ch_L_f(n) is considered to be due to a change in the position of the driver's hands, and maintains the reference value Ch_0 constant. Therefore, according to the steering device 1, only the fluctuation due to the change in the environmental condition can be removed from the capacitance difference values ​​ΔCh_R and ΔCh_L, so that erroneous judgment due to the change in the environmental condition around the steering wheel 2 can be prevented.

[0074] (3) The capacitance threshold setting unit 82 calculates the similarity S(n) by comparing the gradients a_R(n), a_L(n) of the filter values ​​Ch_R_f(n), Ch_L_f(n) of the proximity sensors 4, 5. Thus, according to the steering device 1, it is possible to calculate the similarity S(n) of the change trends of the filter values ​​Ch_R_f(n), Ch_L_f(n) by simple calculation.

[0075] (4) The capacity threshold setting unit 82 corrects the reference value Ch_0(n) to the increasing side when the similarity S(n) of the change tendency of the multiple filter values ​​Ch_R_f(n) and Ch_L_f(n) is higher than the similarity standard S_th and the multiple filter values ​​Ch_R_f(n) and Ch_L_f(n) are both increasing, and corrects the reference value Ch_0 to the decreasing side when the similarity S(n) of the change tendency of the multiple filter values ​​Ch_R_f(n) and Ch_L_f(n) is higher than the similarity standard S_th and the multiple filter values ​​Ch_R_f(n) and Ch_L_f(n) are both decreasing. This makes it possible to keep the capacity difference values ​​ΔCh_R and ΔCh_L constant regardless of changes in the environmental state, thereby preventing erroneous judgment.

[0076] (5) The determination unit 81 determines whether or not the steering wheel 2 is being gripped based on the capacitance difference values ​​ΔCh_R(n), ΔCh_L(n) obtained by subtracting the reference value Ch_0(n) from the measured values ​​Ch_R_d(n), Ch_L_d(n). Therefore, according to the steering device 1, the capacitance difference values ​​ΔCh_R(n), ΔCh_L(n) can be kept constant regardless of changes in the environmental conditions around the steering wheel 2, so that it is possible to accurately determine whether or not the steering wheel 2 is being gripped.

[0077] As described above, in this embodiment, the capacitance threshold setting unit 82 calculates the similarity S(n) by comparing the slopes a_R(n) and a_L(n) of the filter values ​​Ch_R_f(n) and Ch_L_f(n) of the proximity sensors 4 and 5. However, the present invention is not limited to this. The capacitance threshold setting unit 82 may calculate the change amounts dCh_R_f(n) and dCh_L_f(n) of the filter values ​​Ch_R_f(n) and Ch_L_f(n) of the proximity sensors 4 and 5 during a predetermined determination period (for example, from the n-1th period to the nth period) according to the following formulas (12) and (13), and compare these change amounts dCh_R_f(n) and dCh_L_f(n) to calculate the similarity S(n). dCh_R_f(n) = Ch_R_f(n)-Ch_R_f(n-1) (12) dCh_L_f(n) = Ch_L_f(n)-Ch_L_f(n-1) (13)

[0078] In this case, the capacity threshold setting unit 82 calculates the similarity S(n) according to, for example, the following formula (14). In the following formula (14), "a1" is a predetermined positive coefficient. The similarity S(n) defined by the following formula (14) becomes larger as the amounts of change dCh_R_f(n) and dCh_L_f(n) representing the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) become closer, that is, as the degree of similarity of the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) becomes higher. The similarity S(n) becomes smaller as the amounts of change dCh_R_f(n) and dCh_L_f(n) representing the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) become farther apart, that is, as the degree of similarity of the change tendency of each filter value Ch_R_f(n) and Ch_L_f(n) becomes lower. S(n) = a1 / (|dCh_R_f(n)-dCh_L_f(n)|) (14)

[0079] In the present embodiment, the capacity threshold setting unit 82 may change the reference value Ch_0 according to the change in the environmental condition while keeping the grip determination threshold Ch_th constant, but the present invention is not limited to this. The capacity threshold setting unit 82 may change the grip determination threshold Ch_th according to the change in the environmental condition while keeping the reference value Ch_0 constant. In this case, the timing and width of changing the grip determination threshold Ch_th are the same as the timing and width of changing the reference value Ch_0 in the reference value setting process shown in FIG. 3, so detailed description will be omitted. In this case, the difference between the capacity difference value ΔCh and the grip determination threshold Ch_th can be kept constant regardless of the change in the environmental condition around the steering wheel 2, so that the presence or absence of gripping can be determined with high accuracy as in the above embodiment. [Explanation of symbols]

[0080] 1...Steering device 2. Steering handle 20…Rim section 3...Steering shaft 4...Right proximity sensor 40...Right electrode part 42…Right measurement circuit (measuring device) 5...Left proximity sensor 50...Left electrode part (electrode part) 52...Left measuring circuit (measuring device) 8...Grip sensor unit 80...Grip determination device 81…Judgment section 82...Capacity threshold setting unit

Claims

1. a steering wheel that receives steering operation of the vehicle by a driver; a measuring device for measuring the capacitance of an electrode portion provided on the steering wheel; A plurality of the measuring devices, each of which has an electrode portion disposed at a different position; A steering device including: a grip determination device that determines whether or not the steering handle is being gripped based on measurement values ​​obtained by a plurality of the measurement devices, A detection target area is defined on the steering wheel for each of the measuring devices, The gripping determination device includes a capacitance threshold setting unit that sets a capacitance threshold for the capacitance of the electrode unit, and a determination unit that determines whether or not the detection target area is gripped based on a difference or comparison between the measurement value and the capacitance threshold, The steering device according to claim 1, wherein the capacity threshold setting unit determines whether or not the capacity threshold needs to be corrected based on a gradient of the measurement values ​​of each of the plurality of measuring devices or an amount of change in a predetermined determination period.

2. The steering device according to claim 1, characterized in that the capacity threshold setting unit calculates a similarity that increases or decreases depending on the degree of similarity in the change trends of the measurement values ​​of the multiple measuring devices by comparing the slope or the amount of change, and corrects the capacity threshold if the similarity is higher than a predetermined similarity standard, and maintains the capacity threshold constant if the similarity is lower than the similarity standard.

3. The steering device according to claim 2, characterized in that the capacity threshold setting unit corrects the capacity threshold to an increasing side when the measurement values ​​of the multiple measuring devices are all on an increasing trend, and corrects the capacity threshold to a decreasing side when the measurement values ​​of the multiple measuring devices are all on a decreasing trend.

4. 4. The steering device according to claim 3, wherein the determination unit determines whether the steering wheel is being gripped based on a capacitance difference value obtained by subtracting a reference value, which is the capacitance threshold value, from the measured value.

5. 4. The steering device according to claim 3, wherein the determination unit determines whether or not the steering wheel is being gripped by comparing the measured value with a grip determination threshold that is the capacity threshold.

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