Holding the detection device

Abstract

To provide a grip detecting device that can detect the grip of a steering wheel by a driver regardless of a physical size, a constitution, and clothes, etc., in order to improve the traffic safety.SOLUTION: A grip detecting device 6 includes: an electrostatic capacitance measuring unit 68 that measures the electrostatic capacitance of an electrode 60 provided at a steering wheel of a vehicle; a grip detecting unit 70 that detects the grip of the steering wheel by a driver on the basis of a comparison between an electrostatic capacitance measured value Ch_d and a grip threshold Ch_thr by the electrostatic capacitance measuring unit 68; and a threshold setting unit 69 that sets the grip threshold Ch_thr on the basis of a torque detected value Tr_d by a torque sensor 31 that detects steering torque, and of the electrostatic capacitance measured value Ch_d. The threshold setting unit 69 sets the grip threshold Ch_thr on the basis of the torque detected value Tr_d and of the electrostatic capacitance measured value Ch_d when the vehicle is in a certain driving state and when the torque detected value Tr_d is exceeding the torque threshold.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a grip detection device, and more particularly to a grip detection device that detects a driver's grip on a steering wheel. [Background technology]

[0002] In recent years, in order to improve traffic safety, vehicles have been increasingly equipped with driving assistance devices that assist drivers in driving the vehicle, such as a lane keeping function, a lane departure prevention function, a lane change function, and a leading vehicle following function. In vehicles equipped with such driving assistance devices, a grip detection device such as that shown in Patent Document 1 detects whether the driver is gripping the steering wheel, and if it is detected that the driver is not gripping the steering wheel, the device may prompt the driver to grip the steering wheel or cancel any driving assistance functions that are currently being executed.

[0003] The grip detection device disclosed in Patent Document 1 measures the capacitance of electrodes provided on the rim of the steering wheel, and detects whether the driver is gripping the steering wheel based on this capacitance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-87566 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the capacitance formed by the human body, including the driver's hands gripping the steering wheel, varies depending on the driver's physique, constitution, clothing, etc. For this reason, in capacitance-type grip detection devices such as those shown in Patent Document 1, threshold values ​​for capacitance measurements are often set assuming a standard physique, constitution, and clothing. Therefore, if the driver is someone who does not exhibit standard capacitance measurements (for example, someone who is small and has dry skin), there is a risk that the driver's grip on the steering wheel may not be properly detected.

[0006] An object of the present invention is to provide a grip detection device that can detect whether a driver is gripping a steering wheel regardless of the driver's physique, constitution, clothing, etc., in order to improve traffic safety. [Means for solving the problem]

[0007] (1) The grip detection device according to the present invention is characterized by comprising a measurement unit that measures the electrical characteristics of an electrode provided on a vehicle steering wheel, a detection unit that detects the driver's grip of the steering wheel based on a comparison between the electrical characteristic measurement value by the measurement unit and a grip threshold value, and a threshold setting unit that sets the grip threshold value based on a torque detection value by a torque sensor that detects steering torque on the steering wheel and the electrical characteristic measurement value.

[0008] (2) In this case, it is preferable that the threshold setting unit sets the grip threshold based on the torque detection value and the electrical characteristic measurement value when the torque detection value exceeds a predetermined torque threshold.

[0009] (3) In this case, it is preferable that the threshold setting unit sets the grip threshold based on the torque detection value and the electrical characteristic measurement value when the vehicle is in a specific operating state.

[0010] (4) In this case, it is preferable that the threshold setting unit calculates an electrical characteristic reference value based on the torque detection value, and sets the grip threshold based on a comparison between the electrical characteristic measurement value and the electrical characteristic reference value.

[0011] (5) In this case, it is preferable that the threshold setting unit sets the grip threshold to a value smaller than a predetermined grip reference value when the electrical characteristic measurement value is smaller than the electrical characteristic reference value. [Effects of the Invention]

[0012] (1) The grip detection device includes a measurement unit that measures the electrical characteristics of electrodes provided on the steering wheel, a detection unit that detects the driver's grip of the steering wheel based on a comparison between the electrical characteristic measurement value by the measurement unit and a grip threshold, and a threshold setting unit that sets the grip threshold based on the torque detection value and the electrical characteristic measurement value by the torque sensor. Here, when a driver turns the steering wheel while gripping the steering wheel, the electrical characteristic measurement value varies depending on the driver's physique, constitution, clothing, etc. (hereinafter also referred to as "the driver's electrical characteristics"), whereas the torque detection value is not correlated with the driver's electrical characteristics. Therefore, by using the electrical characteristic measurement value and the torque detection value, the threshold setting unit can set the grip threshold based on the electrical characteristic measurement value, taking into account the influence of the driver's electrical characteristics. Therefore, it is possible to detect the grip of the steering wheel regardless of the driver's electrical characteristics, thereby improving traffic safety.

[0013] (2) The threshold setting unit sets the grip threshold based on the torque detection value and the electrical characteristic measurement value when the torque detection value exceeds a predetermined torque threshold, i.e., when the driver is turning the steering wheel while gripping it tightly. This allows the influence of the driver's electrical characteristics to be extracted more accurately from the electrical characteristic measurement value, making it possible to set the grip threshold to a more appropriate value, thereby improving traffic safety.

[0014] (3) For example, when traveling at high speeds, the driver hardly needs to perform any steering operation, and therefore the detected torque value may be small even if the driver is firmly gripping the steering wheel. In contrast, in the present invention, the threshold setting unit sets the grip threshold based on the detected torque value and the electrical characteristic measurement value when the vehicle is in a specific driving state, thereby making it possible to set the grip threshold based on the electrical characteristic measurement value and the detected torque value acquired when the driver is firmly gripping the steering wheel. This makes it possible to more accurately extract the influence of the driver's electrical characteristics from the electrical characteristic measurement value, thereby making it possible to set the grip threshold to a more appropriate value, thereby improving traffic safety.

[0015] (4) The threshold setting unit calculates an electrical characteristic reference value based on the torque detection value, and sets the grip threshold based on a comparison between the electrical characteristic measurement value and this electrical characteristic reference value. This allows the influence of the driver's electrical characteristics to be extracted more accurately from the electrical characteristic measurement value, making it possible to set the grip threshold to a more appropriate value, thereby improving traffic safety.

[0016] (5) When the electrical characteristic measurement value is smaller than the electrical characteristic reference value, the threshold setting unit sets the grip threshold to a value smaller than the predetermined grip reference value. This makes it possible to properly detect the driver's grip of the steering wheel even if the electrical characteristic measurement value does not indicate the grip reference value, even if the driver is gripping the steering wheel, thereby improving traffic safety. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing the configuration of a steering device equipped with a grip detection device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing a circuit configuration of a grip detection device. [Figure 3] 10 is a flowchart showing a specific procedure of a grip threshold setting process. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a grip detection device according to an embodiment of the present invention will be described with reference to the drawings.

[0019] 1 is a diagram showing the configuration of a steering device 1 equipped with a grip detection device 6 according to this embodiment. The steering device 1 includes a steering wheel 2 that receives vehicle steering operations and auxiliary device operations by the driver, a steering shaft 3 that supports the steering wheel 2, and a grip detection device 6 that detects whether the driver is gripping the steering wheel 2.

[0020] The steering wheel 2 comprises a circular rim portion 20 that can be gripped by the driver, a hub portion 23 provided inside the rim portion 20, and three spoke portions 25L, 25R, 25D that extend radially from the hub portion 23 and are connected to the inner rim portion 21 of the rim portion 20.

[0021] 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 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 forms the framework of the hub portion 23 with a steering mechanism that forms part of the vehicle body (not shown). Therefore, the steering torque generated when the driver turns the steering wheel 2 is transmitted to the steering mechanism (not shown) by the steering shaft 3. The steering shaft 3 is also provided with a torque sensor 31 that detects the steering torque acting on the steering shaft 3 and outputs a signal corresponding to the detected value to the grip detection device 6.

[0022] The rim portion 20 and the hub portion 23 are connected by three spokes 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 with the left portion of the rim inner periphery 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 with the right portion of the rim inner periphery 21 as seen by the driver. The lower spoke portion 25D extends vertically and perpendicular to the spokes 25L and 25R and connects the lower portion of the hub portion 23 as seen by the driver with the lower portion of the rim inner periphery 21 as seen by the driver.

[0023] The left spoke portion 25L and the right spoke portion 25R are provided with a left accessory operation console unit 5L and a right accessory operation console unit 5R, respectively, that accepts accessory operation by the driver to operate vehicle accessories (e.g., an audio device, a car navigation device, etc., not shown). Each of these accessory operation console units 5L and 5R has a rectangular shape when viewed from the driver. The driver can operate the vehicle accessories by operating multiple switches 51L, 52L, 53L, 51R, 52R, and 53R provided on these accessory operation console units 5L and 5R with their fingers.

[0024] In the following, the positions of the approximately circular rim portion 20, rim inner periphery 21, hub portion 23, and steering shaft 3 as viewed by the driver, and the orientations of each spoke portion 25L, 25R, 25D may also be expressed in degrees (°) clockwise from the steering shaft 3 as the center and the upper end portion 20C of the rim portion 20 as viewed by the driver. That is, the right spoke portion 25R extends along a 90° angle 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° angle 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° angle and connects the hub portion 23 and the 270° portions of the rim inner periphery 21.

[0025] The grip detection device 6 includes an electrode 60 provided on the steering wheel 2 and a sensor unit 62 electrically connected to the electrode 60.

[0026] The electrode 60 has, for example, a circular ring shape and is conductive. The electrode 60 is provided inside the rim portion 20. Note that in this embodiment, the case where the electrode 60 is provided inside the rim portion 20 will be described, but the shape and location of the electrode 60 are not limited to this. The shape of the electrode 60 is not limited to a circular ring shape, and it may be plate-shaped. Furthermore, the electrode 60 may be provided anywhere within the steering wheel 2, and may be provided on the spoke portions 25L, 25R, 25D, the hub portion 23, or the like, in addition to the rim portion 20.

[0027] The sensor unit 62 is connected to the electrode 60 via a wire 61. This sensor unit 62 is provided, for example, inside the left spoke portion 25L together with the above-mentioned left accessory operation console unit 5L.

[0028] FIG. 2 is a diagram showing the circuit configuration of the grip detection device 6. As shown in FIG. The sensor unit 62 measures the electrical characteristics of the electrode 60 (for example, the capacitance between the electrode 60 and the ground), and detects the driver's grip on the steering wheel 2 based on the measurement result and the torque detection value by the torque sensor 31.

[0029] The sensor unit 62 includes a pulse power supply 63, an amplifier 64, a first switch 65, a second switch 66, a charging capacitor 67, a capacitance measuring unit 68, a threshold setting unit 69, and a grip detection unit 70, and uses these to detect the driver's grip on the steering wheel 2. In Fig. 2, the capacitance between the electrode 60 and the ground (e.g., the vehicle body) is shown divided into a capacitance Ch formed by the human body H, including the driver's hands operating the steering wheel 2, and a stray capacitance Ce formed by stray capacitors E, such as wiring and components, excluding the human body H.

[0030] As shown in Figure 2, the pulse power supply 63 and amplifier 64 are connected in series. The second switch 66 and charging capacitor 67 are connected in parallel. The series circuit consisting of the pulse power supply 63 and amplifier 64 and the parallel circuit consisting of the second switch 66 and charging capacitor 67 are connected via a first switch 65. The output terminal of the amplifier 64 and the first switch 65 are connected to the electrode 60 via a wiring 61. Therefore, the pulse power supply 63 is connected to the electrode 60 via the amplifier 64 and wiring 61. Furthermore, the second switch 66 and charging capacitor 67 are connected to the electrode 60 via the first switch 65 and wiring 61, respectively.

[0031] The pulse power supply 63 supplies a pulse voltage Vs of a predetermined frequency and a predetermined voltage to the amplifier 64 in response to a command from the capacitance measuring unit 68 or the grip detecting unit 70. The amplifier 64 amplifies the pulse voltage Vs supplied from the pulse power supply 63 and applies it to the electrode 60.

[0032] The second switch 66 is a switching element that is turned on / off by a drive circuit (not shown). The drive circuit for the second switch 66 keeps the second switch 66 off until the voltage VCref of the charging capacitor 67 reaches a predetermined threshold Vthr, for example, and then turns the second switch 66 on after the voltage VCref reaches the threshold Vthr, thereby discharging the charge stored in the charging capacitor 67.

[0033] The first switch 65 is a switching element that is turned on / off by a drive circuit (not shown). The drive circuit for this first switch 65 turns off the first switch 65 in response to the rising edge of the pulse voltage Vs of the pulse power supply 63. As a result, the pulse voltage supplied from the pulse power supply 63 and the amplifier 64 is applied to the electrode 60, and electric charge moves through the path indicated by the arrow 2a in Figure 2, charging the human body H and the floating capacitor E.

[0034] Furthermore, the drive circuit for the first switch 65 turns on the first switch 65 in response to the falling edge of the pulse voltage Vs of the pulse power supply 63. This connects the human body H and the floating capacitor E to the charging capacitor 67, and charge moves from the human body H and the floating capacitor E to the charging capacitor 67 via the path indicated by the arrow 2b in Figure 2, thereby charging the charging capacitor 67. This causes the voltage VCref of the charging capacitor 67 to rise.

[0035] Therefore, when a pulse voltage is applied to the electrode 60 by the pulse power supply 63 and the amplifier 64, charging and discharging of the human body H and the floating capacitor E are repeated alternately, and the voltage VCref of the charging capacitor 67 gradually increases. At this time, the time until the voltage VCref of the charging capacitor 67 reaches the threshold Vthr (or the number of pulses of the pulse power supply 63) varies depending on the capacitance Ch formed by the human body H, i.e., the state of the driver's hand operating the steering wheel 2. That is, when the driver's hand is in contact with or close to the steering wheel 2 and the capacitance Ch is high, the time it takes for the voltage VCref of the charging capacitor 67 to reach the threshold Vthr becomes shorter, and when the driver's hand is away from the steering wheel 2 and the capacitance Ch is low, the time it takes for the voltage VCref of the charging capacitor 67 to reach the threshold Vthr becomes longer.

[0036] The capacitance measuring unit 68 measures the time and number of pulses until the voltage VCref of the charging capacitor 67 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 electrode 60. The capacitance measuring unit 68 transmits the measurement value Ch_d of the capacitance Ch obtained by the above procedure to the threshold setting unit 69 and the grip detection unit 70.

[0037] The grip detection unit 70 detects whether the driver is gripping the steering wheel 2 based on a comparison between the capacitance measurement value Ch_d by the capacitance measurement unit 68 and a grip threshold value Ch_thr set by a procedure described below in the threshold setting unit 69. More specifically, the grip detection unit 70 determines that the driver is not gripping the steering wheel 2 when the capacitance measurement value Ch_d is less than the grip threshold value Ch_thr, and determines that the driver is gripping the steering wheel 2 when the capacitance measurement value Ch_d is equal to or greater than the grip threshold value Ch_thr.

[0038] The threshold setting unit 69 sets a grip threshold Ch_thr to be referenced in the grip detection unit 70 by executing the grip threshold setting process described below based on the torque detection value Tr_d from the torque sensor 31 and the capacitance measurement value Ch_d from the capacitance measurement unit 68.

[0039] 3 is a flowchart showing a specific procedure for the grip threshold setting process, which is repeatedly executed by threshold setting unit 69 at predetermined intervals after the vehicle is started.

[0040] First, in step ST1, the threshold setting unit 69 determines whether the current driving state of the vehicle is a predetermined specific driving state. Here, the specific driving state refers to a driving state in which the steering torque can increase only by the steering operation of the steering wheel 2 by the driver, such as immediately after the vehicle has started to start. If the state is immediately after the vehicle has started to start, the driver needs to grip the steering wheel 2 and turn the steering wheel 2 in order to pull the vehicle out of a parking lot, so the steering torque can increase only by the steering operation of the steering wheel 2 by the driver. If the determination result in step ST1 is NO, the threshold setting unit 69 ends the grip threshold setting process, and if the determination result is YES, the process proceeds to step ST2.

[0041] Next, in step ST2, the threshold setting unit 69 acquires the torque detection value Tr_d from the torque sensor 31, and proceeds to step ST3. Next, in step ST3, the threshold setting unit 69 determines whether the acquired torque detection value Tr_d is greater than a predetermined torque threshold Tr_thr. If the determination result in step ST3 is NO, the threshold setting unit 69 ends the grip threshold setting process, and if the determination result is YES, proceeds to step ST4.

[0042] Next, in step ST4, the threshold setting unit 69 acquires the capacitance measurement value Ch_d from the capacitance measurement unit 68, and proceeds to step ST5. As described above, the threshold setting unit 69 sets the grip threshold value Ch_thr based on the torque detection value Tr_d and the capacitance measurement value Ch_d when the vehicle is in a specific operating state and the torque detection value Tr_d exceeds the torque threshold value Tr_thr.

[0043] Next, in step ST5, the threshold setting unit 69 calculates the required frictional force Ffr based on the detected torque value Tr_d acquired in step ST2, and then proceeds to step ST6. Here, the required frictional force Ffr corresponds to the frictional force between the driver's hand and the rim portion 20 that is required to increase the steering torque to the detected torque value Tr_d solely through the driver's steering operation. The threshold setting unit 69 calculates the required frictional force Ffr by searching, for example, a map (not shown) based on the detected torque value Tr_d.

[0044] Next, in step ST6, the threshold setting unit 69 calculates the number of gripping fingers Nf, which corresponds to the number of fingers with which the driver is gripping the rim portion 20, based on the required frictional force Ffr calculated in step ST5, and then proceeds to step ST7. Here, the frictional force acting between the driver's hand and the rim portion 20 increases as the number of fingers gripping the rim portion 20 increases, so the number of gripping fingers Nf also increases as the required frictional force Ffr increases. The threshold setting unit 69 calculates the number of gripping fingers Nf by searching a map (not shown), for example, based on the required frictional force Ffr.

[0045] Next, in step ST7, the threshold setting unit 69 calculates a capacitance reference value Ch_bs based on the number of gripped rods Nf calculated in step ST6, and then proceeds to step ST8. Here, the capacitance reference value Ch_bs corresponds to the capacitance measured by the capacitance measuring unit 68 when a hypothetical driver (hereinafter also referred to as a "standard driver") with a standard physique, constitution, clothing, etc. grips the rim portion 20 with the number of gripped rods Nf. The threshold setting unit 69 calculates the capacitance reference value Ch_bs by searching, for example, a map (not shown) based on the number of gripped rods Nf.

[0046] Next, in step ST8, the threshold setting unit 69 determines whether or not the capacitance measurement value Ch_d acquired in step ST4 is smaller than the capacitance reference value Ch_bs calculated in step ST7.

[0047] If the determination result in step ST8 is NO, the threshold setting unit 69 proceeds to step ST9, sets a predetermined grip reference value Ch_thr_bs as the grip threshold Ch_thr, transmits it to the grip detection unit 70, and then ends the grip threshold setting process. Here, the grip reference value Ch_thr_bs corresponds to a grip threshold set assuming a standard driver. More specifically, the grip reference value Ch_thr_bs is set to a value slightly smaller than the capacitance measured by the capacitance measurement unit 68 when a standard driver is gripping the rim portion 20.

[0048] If the determination result in step ST8 is YES, i.e., if the capacitance measurement value Ch_d is smaller than the capacitance reference value Ch_bs, the threshold setting unit 69 proceeds to step ST10. In step ST10, the threshold setting unit 69 calculates a correction coefficient a between 0 and 1 based on the difference ΔCh (=Ch_bs−Ch_d) between the capacitance reference value Ch_bs and the capacitance measurement value Ch_d, and proceeds to step ST11. More specifically, the threshold setting unit 69 calculates the correction coefficient a so that it approaches 1 as the difference ΔCh approaches 0, and approaches 0 as the difference ΔCh increases.

[0049] Next, in step ST11, the threshold setting unit 69 sets the grip threshold Ch_thr by correcting the grip reference value Ch_thr_bs using a correction coefficient a set between 0 and 1, transmits the corrected value to the grip detection unit 70, and then terminates the grip threshold setting process. More specifically, when the capacitance measurement value Ch_d is smaller than the capacitance reference value Ch_bs, the threshold setting unit 69 multiplies the grip reference value Ch_thr_bs by the correction coefficient a set between 0 and 1, thereby setting the grip threshold Ch_thr to a value smaller than the grip reference value Ch_thr_bs (Ch_thr = Ch_thr_bs × a). In this way, when the capacitance measurement value Ch_d is smaller than the capacitance reference value Ch_bs, the threshold setting unit 69 sets the grip threshold Ch_thr to a value smaller than the grip reference value Ch_thr_bs, and sets the grip threshold Ch_thr to a smaller value as the difference ΔCh increases.

[0050] The grip detection device 6 according to this embodiment has the following advantages. (1) The grip detection device 6 includes a capacitance measurement unit 68 that measures the capacitance of the electrodes 60 provided on the steering wheel 2, a grip detection unit 70 that detects the driver's grip of the steering wheel 2 based on a comparison between a capacitance measurement value Ch_d measured by the capacitance measurement unit 68 and a grip threshold value Ch_thr, and a threshold setting unit 69 that sets the grip threshold value Ch_thr based on a torque detection value Tr_d and a capacitance measurement value Ch_d measured by the torque sensor 31. Here, the capacitance measurement value Ch_d measured when the driver grips the steering wheel 2 and turns the steering wheel 2 varies depending on the driver's electrical characteristics, such as the driver's physique, constitution, and clothing, whereas the torque detection value Tr_d is not correlated with the driver's electrical characteristics. Therefore, by using the capacitance measurement value Ch_d and the torque detection value Tr_d, the threshold setting unit 69 can set the grip threshold value Ch_thr from the capacitance measurement value Ch_d while taking into account the influence of the driver's electrical characteristics. This makes it possible to detect the driver's grip of the steering wheel 2 regardless of the driver's electrical characteristics, thereby improving traffic safety.

[0051] (2) When the torque detection value Tr_d exceeds the torque threshold value Tr_thr, that is, when the driver is turning the steering wheel 2 while tightly gripping it, the threshold setting unit 69 sets the grip threshold value Ch_thr based on the torque detection value Tr_d and the capacitance measurement value Ch_d. This makes it possible to extract with greater accuracy the influence of the driver's electrical characteristics from the capacitance measurement value Ch_d, thereby making it possible to set the grip threshold value Ch_thr to a more appropriate value, thereby improving traffic safety.

[0052] (3) For example, when traveling at high speeds, the driver hardly needs to perform any steering operation, and therefore the detected torque value Tr_d may indicate a small value even if the driver tightly grips the steering wheel 2. In response to this, in the grip detection device 6, the threshold setting unit 69 sets the grip threshold value Ch_thr based on the detected torque value Tr_d and the capacitance measurement value Ch_d when the vehicle is in a specific driving state, thereby making it possible to set the grip threshold value Ch_thr based on the capacitance measurement value Ch_d and the detected torque value Tr_d acquired when the driver is firmly gripping the steering wheel 2. This makes it possible to more accurately extract the influence of the driver's electrical characteristics from the capacitance measurement value Ch_d, thereby making it possible to set the grip threshold value Ch_thr to a more appropriate value, thereby improving traffic safety.

[0053] (4) The threshold setting unit 69 calculates the capacitance reference value Ch_bs based on the torque detection value Tr_d, and sets the grip threshold value Ch_thr based on a comparison between the capacitance measurement value Ch_d and this capacitance reference value Ch_bs.This makes it possible to more accurately extract the influence of the driver's electrical characteristics from the capacitance measurement value Ch_d, and therefore makes it possible to set the grip threshold value Ch_thr to a more appropriate value, thereby improving traffic safety.

[0054] (5) When the capacitance measurement value Ch_d is smaller than the capacitance reference value Ch_bs, the threshold setting unit 69 sets the grip threshold value Ch_thr to a value smaller than a predetermined grip reference value Ch_thr_bs. As a result, even if a driver grips the steering wheel 2 but the capacitance measurement value Ch_d does not indicate the grip reference value Ch_thr_bs, it is possible to properly detect that the driver is gripping the steering wheel 2, thereby improving traffic safety.

[0055] Although one embodiment of the present invention has been described above, the present invention is not limited to this, and the detailed configuration may be modified as appropriate within the scope of the spirit of the present invention. [Explanation of symbols]

[0056] 1...Steering device 2...Steering wheel 20...Rim section 23...Hub section 25L, 25R...Spoke section 31...Torque sensor 6...Grip detection device 60...electrode 61...Wiring 62...Sensor unit 63...Pulse power supply (power supply) 64...Amplifier 65...First switch 66...Second switch 67...Charging capacitor 68...Capacitance measuring section 69...Threshold setting unit 70...Grip detection unit

Claims

1. a measurement unit that measures electrical characteristics of an electrode provided on a steering wheel of a vehicle; a detection unit that detects a driver's grip of the steering wheel based on a comparison between an electrical characteristic measurement value by the measurement unit and a grip threshold value, a threshold setting unit that calculates an electrical characteristic reference value based on a torque detection value by a torque sensor that detects steering torque applied to the steering wheel, and sets the grip threshold value based on a comparison between the electrical characteristic measurement value and the electrical characteristic reference value.

2. The grip detection device according to claim 1, wherein the threshold setting unit sets the grip threshold based on the torque detection value and the electrical characteristic measurement value when the torque detection value exceeds a predetermined torque threshold.

3. The grip detection device according to claim 1 or 2, wherein the threshold setting unit sets the grip threshold based on the torque detection value and the electrical characteristic measurement value when the vehicle is in a specific driving state.

4. A measuring unit that measures the electrical characteristics of an electrode provided on a steering wheel of a vehicle; a detection unit that detects a driver's grip of the steering wheel based on a comparison between an electrical characteristic measurement value by the measurement unit and a grip threshold value, a threshold setting unit that calculates an electrical characteristic reference value based on a torque detection value by a torque sensor that detects steering torque applied to the steering wheel, and sets the grip threshold to a value smaller than a predetermined grip reference value if the electrical characteristic measurement value is smaller than the electrical characteristic reference value.

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