Steering-wheel grip detection device

Abstract

To provide a steering-wheel grip detection device capable of inhibiting a deterioration in robustness of grip detection and achieving highly accurate grip detection.SOLUTION: A steering-wheel grip detection device 3 includes: a first electrode 21 arranged at a rim 2; a second electrode 22 arranged at the rim 2; and a control circuit 40. The first electrode 21 is an electrode having a wider projected area than the second electrode 22. The control circuit 40 can be switched between: a first mode in which the first electrode 21 serves as a sensor electrode, and the second electrode 22 serves as a shield electrode; and a second mode in which the first electrode 21 serves as the shield electrode, and the second electrode 22 serves as the sensor electrode. The control circuit obtains a first-mode capacitance detected by the first electrode 21 serving as the sensor electrode in the first mode and a second-mode capacitance detected by the second electrode 22 serving as the sensor electrode in the second mode, and detects a grip on a steering wheel 1 on the basis of the first-mode capacitance and the second-mode capacitance.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a steering wheel grip detection device. [Background technology]

[0002] Patent Document 1 discloses a sensor pad including a pad substrate, a sensor electrode, and a shield electrode. A sensor electrode and a shield electrode are arranged parallel to each other and spaced apart on a first surface of the pad substrate. The shield electrode is electrically connected to a voltage source, generating capacitance between the shield electrode and the sensor electrode, and the sensor electrode can detect changes in the capacitance. The shield electrode can also heat the surface of a vehicle component. The sensor electrode can sense the presence of a passenger's hand or body adjacent to the steering wheel or seat assembly. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 022765 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a heater pattern with a smaller projected area than the sensor electrode is used as the shield electrode, arranging the heater pattern parallel to the sensor electrode increases the parasitic capacitance between the core metal (ground potential member) inside the steering wheel and the sensor electrode. When detecting gripping of the steering wheel, the signal is detected with the parasitic capacitance added to the grip detection sensor value. Because the parasitic capacitance constantly fluctuates depending on the external environment, such as temperature and humidity, the detected signal value also fluctuates, which poses the issue of false detection.

[0005] Therefore, an object of the present disclosure is to provide a steering wheel grip detection device that can suppress a decrease in robustness of grip detection and achieve highly accurate grip detection. [Means for solving the problem]

[0006] A steering wheel grip detection device according to one embodiment of the present disclosure comprises a first electrode arranged on the rim of a steering wheel, a second electrode arranged on the rim and located closer to the inner surface of the steering wheel than the first electrode, and a control circuit, wherein the first electrode has a larger projected area than the second electrode, and the control circuit is switchable between a first mode in which the first electrode is used as a sensor electrode and the second electrode is used as a shield electrode, and a second mode in which the first electrode is used as a shield electrode and the second electrode is used as a sensor electrode, and calculates a first mode capacitance detected by the first electrode used as a sensor electrode in the first mode and a second mode capacitance detected by the second electrode used as a sensor electrode in the second mode, and detects gripping of the steering wheel based on the first mode capacitance and the second mode capacitance. [Effects of the Invention]

[0007] The steering wheel grip detection device of the present disclosure can suppress a decrease in robustness of grip detection and achieve highly accurate grip detection. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a vehicle interior in which a steering wheel according to an embodiment is arranged. [Figure 2] FIG. 2 is a perspective cross-sectional view showing the steering wheel taken along line II-II in FIG. [Figure 3] FIG. 3 is a circuit diagram showing the steering wheel grip detection device according to the embodiment. [Figure 4]FIG. 4 is a diagram showing capacitances when the first mode, the second mode, and the third mode are executed when the user's finger is in contact with the steering wheel. [Figure 5] FIG. 5 shows a case where each mode is driven in a time-division manner. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0010] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in the independent claims are described as optional components.

[0011] In addition, each drawing is a schematic diagram and is not necessarily an exact illustration. In addition, the same components are denoted by the same reference numerals in each drawing.

[0012] Furthermore, in the following embodiments, expressions such as "T-shaped" are used. For example, "T-shaped" does not only mean that it is a perfect T-shape, but also means that it is substantially a T-shape, that is, that it includes an error of about a few percent. Furthermore, "T-shaped" means a T-shape within the scope in which the effects of the present disclosure can be achieved. The same applies to other expressions using "shape."

[0013] (Embodiment) First, the configuration of the steering wheel grip detection device 3 will be described with reference to FIGS.

[0014] Fig. 1 is a diagram showing a cabin of a vehicle 4 in which a steering wheel 1 according to an embodiment is arranged. Fig. 2 is a perspective cross-sectional view showing the steering wheel 1 taken along line II-II in Fig. 1.

[0015] As shown in FIGS. 1 and 2, a steering wheel 1 can apply a steering angle to the steered wheels of a vehicle 4, for example.

[0016] The steering wheel 1 has an annular rim 2 and a steering wheel grip detection device 3. The rim 2 is integrally formed with T-shaped spokes arranged on the inner circumferential surface of the rim 2. The rim 2 is a grip portion to be held by the driver's hands, and is ring-shaped.

[0017] The rim 2 has a metal core 2a that is a circular metal core, and a resin layer 2b that covers the metal core 2a. A first electrode 21, a second electrode 22, and a substrate 23 of the steering wheel grip detection device 3 are wound around the rim 2. The first electrode 21, the second electrode 22, and the substrate 23 will be described later. The outer periphery of the first electrode 21 of the steering wheel grip detection device 3 wound around the rim 2 is covered by a steering cover 11 made of leather, wood, resin, or the like. The steering cover 11 is adhered and fixed to the outer periphery of the first electrode 21 of the steering wheel grip detection device 3 with an adhesive, double-sided tape, or the like. The resin layer 2b is made of a urethane resin material, for example, polyurethane foam.

[0018] The steering wheel grip detection device 3 is a device that detects contact of the user's (human body's) hands with the steering wheel 1. Contact does not only include cases where the user's hands directly contact the steering cover 11 of the steering wheel 1, but also includes a state where the user's hands are separated from the steering cover 11, as long as the steering wheel grip detection device 3 can detect the user's hands. The steering wheel grip detection device 3 can detect contact not only when the user's hands contact the steering wheel 1, but also when their arms, legs, etc. contact the steering wheel 1. In this embodiment, a case where the user's hands contact the steering wheel 1 will be described.

[0019] The steering wheel grip detection device 3 is, for example, a capacitance-type proximity sensor, and is a grip sensor that detects the grip of a user's hand in a vehicle 4 having a steering wheel 1. Specifically, the steering wheel grip detection device 3 detects whether the user's hand is touching the steering wheel 1 by detecting a change in capacitance between the user's hand and a first electrode 21 of the steering wheel grip detection device 3. When the user's hand is away from the steering wheel 1, the steering wheel grip detection device 3 detects the capacitance between the vehicle 4 and the first electrode 21. However, the distance between the vehicle 4 and the first electrode 21 is much larger than the distance between the first electrode 21 and the user's hand when the user's hand approaches or touches the steering cover 11, so the capacitance value between the vehicle 4 and the first electrode 21 is extremely small. Furthermore, when the user's hand approaches or touches the steering cover 11, the user's hand is interposed between the first electrode 21 and the vehicle body, causing a change in capacitance. If the detected capacitance is equal to or greater than a specified value, it can be determined that the user's hand is touching or gripping the steering wheel 1.

[0020] The steering wheel grip detector 3 includes a first electrode 21, a substrate 23, a sewing thread 24, a second electrode 22, a control circuit 40, and a power supply circuit 40c. are.

[0021] The first electrode 21 is disposed on the rim 2 of the steering wheel 1. Specifically, the first electrode 21 is disposed on the back surface of the steering cover 11 and on the front surface of the substrate 23. In other words, the first electrode 21 is sandwiched between the steering cover 11 and the substrate 23. The front surface of the substrate 23 faces the steering cover 11. The first electrode 21 is adhered to the back surface of the steering cover 11 with an adhesive layer (not shown) and to the front surface of the substrate 23 with an adhesive layer (not shown), and is fixed to the substrate 23. The first electrode 21 is connected to the control circuit 40.

[0022] Only one first electrode 21 may be disposed on the surface of the base material 23, or a plurality of first electrodes 21 may be disposed.

[0023] The first electrode 21 is an electrode having a larger projected area than the second electrode 22. As will be described later, the second electrode 22 is a heater wire made of a conductive wire, and therefore, when the first electrode 21 and the second electrode 22 are viewed overlapping each other, the projected area of ​​the first electrode 21 is larger than that of the second electrode 22.

[0024] The first electrode 21 may be, for example, a planar electrode made of a conductor, or a conductive cloth made by plating non-metallic fibers. The non-metallic fibers may be polyethylene terephthalate (PET) or the like. The plating may be, for example, copper plating and nickel plating laminated on the copper plating.

[0025] The base material 23 is a nonwoven fabric formed into a long sheet shape from a material having elasticity, flexibility, and ductility. For example, the base material 23 is made of a synthetic resin such as polyethylene (PE) or polyethylene terephthalate (PET).

[0026] The substrate 23 has a front surface and a back surface. The first electrode 21 is disposed on the front surface via an adhesive layer (not shown), and the second electrode 22 is disposed on the back surface via an adhesive layer (not shown). In other words, the substrate 23 is sandwiched between the first electrode 21 and the second electrode 22. The back surface is the surface on which the second electrode 22 is held and faces the rim 2.

[0027] The first electrode 21, the second electrode 22, and the substrate 23 of the steering wheel grip detection device 3 are wound around the rim 2, and the substrate 23 is attached to the rim 2. When the first electrode 21, the second electrode 22, and the substrate 23 of the steering wheel grip detection device 3 are wound around the rim 2, the substrate 23 is wound in the direction of winding around the rim 2 and also in a direction perpendicular to the winding direction, resulting in a long (strip-like) shape that can cover the entire rim 2. In other words, the substrate 23 is formed according to the shape and size of the rim 2.

[0028] The second electrode 22 is a heater wire made of a conductive wire. The second electrode 22 is disposed on the rim 2. Specifically, the second electrode 22 is disposed on an inner layer of the steering wheel 1 relative to the first electrode 21, i.e., closer to the rim 2 than the first electrode 21. One end of the second electrode 22 and the other end of the second electrode 22 are connected to the control circuit 40. The second electrode 22 is disposed in a zigzag pattern on the back surface of the base material 23. Specifically, the second electrode 22 is a metal wire such as a copper wire, and is sewn to the back surface of the base material 23 with sewing thread 24 so as to form a zigzag pattern. Here, "the second electrode 22 is sewn to the back surface of the base material 23 with the sewing thread 24" means that the second electrode 22 is fixed to the base material 23 by the sewing thread 24 sewn to the base material 23.

[0029] In the present embodiment, the second electrode 22 is sewn to the rear surface of the base material 23 with sewing thread 24, but may also be fixed to the base material 23 by thermocompression bonding or the like. Also, the second electrode 22 may be fixed to the base material 23 with an adhesive.

[0030] The second electrode 22 is disposed on the surface of the rim 2 and is adhered to the surface of the rim 2 with an adhesive (not shown). The second electrode 22 is sandwiched between the rim 2 and the substrate 23.

[0031] The control circuit 40 is embedded in, for example, a spoke. The control circuit 40 is electrically connected to the first electrode 21 and the second electrode 22, and when the user's hand approaches the steering wheel 1, the control circuit 40 detects contact with the steering wheel 1 based on a signal transmitted from the first electrode 21. In other words, the control circuit 40 detects whether the user's hand is in contact with the rim 2.

[0032] The control circuit 40 is electrically connected to a power supply circuit 40c. By controlling the power supply circuit 40c, the control circuit 40 supplies power from a battery 39 to the first electrode 21 and the second electrode 22 when detecting whether the user's hand is touching the rim 2, and supplies power from the battery 39 to the second electrode 22 to heat the second electrode 22. In other words, the power supply circuit 40c is controlled by the control circuit 40 to apply a measurement potential to the first electrode 21 and the second electrode 22. The power supply circuit 40c is also controlled by the control circuit 40 to pass a direct current through the second electrode 22. The second electrode 22 functions as a heater when a direct current flows through it. In this case, because only a direct current flows through the second electrode 22, one end of the second electrode 22 is electrically connected to a battery terminal 39a and the other end to ground 38, as shown in FIG. 3 (described later). Note that the second electrode 22 is not limited to a configuration having a heater function. The second electrode 22 may be configured to simply float above the ground 38 without passing a direct current.

[0033] Next, the circuit configuration and functions of the steering wheel grip detection device 3 will be described with reference to FIGS.

[0034] Fig. 3 is a circuit diagram showing the steering wheel grip detection device 3 of the embodiment. Fig. 4 is a diagram showing the capacitance when the first mode, the second mode, and the third mode are executed when the user's hand is in contact with the steering wheel 1. Fig. 4(a) shows the capacitance C measured when the user's hand is in contact with the steering wheel 1 in the first mode. fgr and capacitance C strHOD FIG. 4(b) shows the capacitance C measured when the user's hand is in contact with the steering wheel 1 in the second mode. strTHD FIG. 4(c) shows that no capacitance is measured when the user's hand is in contact with the steering wheel 1 in the third mode.

[0035] 3, the control circuit 40 has a first mode in which the first electrode 21 is used as a sensor electrode and the second electrode 22 is used as a shield electrode, and a second mode in which the first electrode 21 is used as a shield electrode and the second electrode 22 is used as a sensor electrode. The control circuit 40 can switch between the first mode and the second mode. In this case, the control circuit 40 can detect gripping of the steering wheel 1 based on the determined first mode capacitance and second mode capacitance.

[0036] The control circuit 40 further has a third mode in which the second electrode 22 operates as a heater. The control circuit 40 can also switch between the first mode, the second mode, and the third mode. In this case, the control circuit 40 can detect gripping of the steering wheel 1 based on the determined first mode capacitance and second mode capacitance, and can supply power to the second electrode 22 to cause the second electrode 22 to generate heat.

[0037] The control circuit 40 includes a capacitance sensor circuit 40a.

[0038] The capacitance sensor circuit 40a calculates the capacitance between the first electrode 21 and the user's hand to detect contact between the user's hand and the steering wheel 1, and can detect the user's hand gripping the steering wheel 1.

[0039] The capacitance sensor circuit 40a has a sensor terminal 41 and a shield terminal .

[0040] The sensor terminal 41 can apply a measurement potential to an electrode connected to the sensor terminal 41, and therefore the connected electrode can be used as a sensor electrode. Specifically, the sensor terminal 41 can use the first electrode 21 as the sensor electrode in the first mode and the second electrode 22 as the sensor electrode in the second mode.

[0041] The shield terminal 42 can apply a shield potential in phase with the measurement potential to the electrode connected to the shield terminal 42, allowing the connected electrode to serve as a shield electrode. Specifically, the shield terminal 42 can use the second electrode 22 as the shield electrode in the first mode and the first electrode 21 as the shield electrode in the second mode.

[0042] The steering wheel grip detection device 3 includes a control circuit 40, a power supply circuit 40c, a first electrode 21, and a second electrode 22, as well as a first switch 31, a second switch 32, a third switch 33, a fourth switch 34, a fifth switch 35, and a sixth switch 36.

[0043] The first switch 31 is disposed between the sensor terminal 41 and the second electrode 22. Specifically, one end of the first switch 31 is connected to the sensor terminal 41 and one end of the second switch 32, and the other end of the first switch 31 is connected to one end of the sixth switch 36, the other end of the third switch 33, and one end of the second electrode 22.

[0044] The second switch 32 is disposed between the sensor terminal 41 and the first electrode 21. Specifically, one end of the second switch 32 is connected to the sensor terminal 41 and one end of the first switch 31, and the other end is connected to the other end of the fourth switch 34 and one end of the first electrode 21.

[0045] The third switch 33 is disposed between the shield terminal 42 and the second electrode 22. Specifically, one end of the third switch 33 is connected to the shield terminal 42 and one end of the fourth switch 34, and the other end is connected to the other end of the first switch 31, one end of the sixth switch 36, and one end of the second electrode 22.

[0046] The fourth switch 34 is disposed between the shield terminal 42 and the first electrode 21. Specifically, one end of the fourth switch 34 is connected to the shield terminal 42 and one end of the third switch 33, and the other end is connected to the other end of the second switch 32 and one end of the first electrode 21.

[0047] The fifth switch 35 is disposed between the battery terminal 39a and the other end of the second electrode 22. Specifically, the fifth switch 35 has one end connected to the other end of the second electrode 22, and the other end connected to a power supply circuit 40c for supplying power from the battery 39.

[0048] The sixth switch 36 is disposed between the ground 38 and one end of the second electrode 22. Specifically, one end of the sixth switch 36 is connected to the other end of the first switch 31, the other end of the third switch 33, and one end of the second electrode 22, and the other end is connected to the ground 38.

[0049] The control circuit 40 further includes a mode switching circuit 40b.

[0050] The mode switching circuit 40b can control switching of each of the first switch 31, the second switch 32, the third switch 33, the fourth switch 34, the fifth switch 35, and the sixth switch 36. Therefore, the mode switching circuit 40b can switch between the first mode and the second mode at a predetermined cycle. The mode switching circuit 40b can also switch between the first mode, the second mode, and the third mode at a predetermined cycle.

[0051] In such a circuit configuration, in the first mode, the mode switching circuit 40b can turn on the second switch 32 and the third switch 33 and turn off the other switches (the first switch 31, the fourth switch 34, the fifth switch 35, and the sixth switch 36).

[0052] In the second mode, the mode switching circuit 40b can turn on the first switch 31 and the fourth switch 34 and turn off the other switches (the second switch 32, the third switch 33, the fifth switch 35, and the sixth switch 36).

[0053] In the third mode, the mode switching circuit 40b can turn on the fifth switch 35 and the sixth switch 36 and turn off the other switches (the first switch 31, the second switch 32, the third switch 33, and the fourth switch 34).

[0054] Next, the operation of the steering wheel grip detection device 3 will be described with reference to FIGS.

[0055] Figure 5 shows the cases where each mode is driven in a time-division manner. Figure 5(a) shows the case where switching is performed between the first mode and the second mode. Figure 5(b) shows the case where switching is performed between the first mode, the second mode, and the third mode. In Figures 5(a) and 5(b), the period when the first mode is being executed is indicated by hatching with diagonal lines going up to the right, the period when the second mode is being executed is indicated by hatching with diagonal lines going up to the left, and the period when the third mode is being executed is indicated by hatching in a grid pattern.

[0056] The capacitance sensor circuit 40a calculates a first mode capacitance detected by the first electrode 21 serving as a sensor electrode in the first mode and a second mode capacitance detected by the second electrode 22 serving as a sensor electrode in the second mode, and can detect the user's grip on the steering wheel 1 based on the first mode capacitance and the second mode capacitance.

[0057] As shown in FIG. 5(a), when the third mode is not being executed, the steering wheel grip detection device 3 can repeatedly switch between the first mode and the second mode at a predetermined cycle.

[0058] Specifically, as shown in Figures 3 and 4, the mode switching circuit 40b turns on the second switch 32 and the third switch 33 and turns off the other switches, causing the control circuit 40 to operate in the first mode. In the first mode, the capacitance sensor circuit 40a passes an AC current through the first electrode 21, i.e., applies a measurement potential to the first electrode 21. At this time, when the user's hand touches the steering cover 11 of the rim 2, the capacitance of the first electrode 21 corresponding to the contact point changes, and the sensor terminal 41 of the capacitance sensor circuit 40a measures the capacitance of the first electrode 21 based on the current value (measurement potential) of the current flowing through the first electrode 21. In terms of an equivalent circuit, as shown in Figure 4(a), when viewed from the first electrode 21 connected to the capacitance sensor circuit 40a, the capacitance C fgr and capacitance C strHOD The capacitance measured in the first mode (first mode capacitance) includes the capacitance C between the hand and the first electrode 21. fgr and the capacitance C between the first electrode 21 and the core metal 2a. strHOD It contains the capacitance C fgr indicates the sensor value between the hand and the first electrode 21. strHOD indicates the parasitic capacitance in the steering wheel 1. HOD is an abbreviation for Hands On Detection.

[0059] When a predetermined period sufficient for measuring capacitance in the first mode has elapsed, the mode switching circuit 40b switches from the first mode to the second mode. Specifically, the mode switching circuit 40b turns on the first switch 31 and the fourth switch 34 and turns off the other switches, driving the control circuit 40 in the second mode. In the second mode, the capacitance sensor circuit 40a passes an AC current through the second electrode 22, i.e., applies a measurement potential to the second electrode 22. Even if the user's hand is in contact with the steering cover 11, the capacitance between the user's hand and the first electrode 21 cannot be measured because the second switch 32 is off. Furthermore, the capacitance between the user's hand and the second electrode 22 cannot be measured because the first electrode 21 acts as a shield electrode between the user's hand and the second electrode 22. The sensor terminal 41 of the capacitance sensor circuit 40a measures the capacitance at the second electrode 22 based on the current value (measurement potential) of the current flowing through the second electrode 22. The capacitance measured in the second mode (second mode capacitance) is the capacitance C between the second electrode 22 and the core metal 2a. strTHD The capacitance C strTHD indicates the parasitic capacitance in the steering wheel 1. Note that THD is an abbreviation for Temperature & Humidity Detection.

[0060] Capacitance C strHOD and capacitance C strTHD Both are capacitances that are coupled within the steering wheel 1, and therefore fluctuate in response to changes in the external environment such as temperature and humidity. However, it is known that there is a correlation between the way capacitance fluctuates in response to changes in the external environment. For example, if the ambient temperature is 25°C and the humidity is 30%, the capacitance is 50 pF, but if the ambient temperature is 40°C and the humidity is 95%, the capacitance is 150 pF. By utilizing this characteristic, the capacitance C strTHD from capacitance C strHOD can be estimated and calculated.

[0061] Capacitance C strHOD = f(capacitance C strTHD) is calculated in advance, the capacitance sensor circuit 40a can calculate the capacitance C strTHD Using the function showing the correlation above, the capacitance C strHOD The capacitance sensor circuit 40a can calculate the capacitance C strHOD is calculated, the first mode capacitance measured in the first mode (capacitance C fgr +Capacitance C strHOD ) and calculate the capacitance C strHOD By subtracting the capacitance C fgr The capacitance sensor circuit 40a can calculate the calculated capacitance C fgr From this, it can be detected that the user's hands are gripping the steering wheel 1.

[0062] The execution period (predetermined period) of the first mode and the execution period (predetermined period) of the second mode are equal in length, for example, several milliseconds.

[0063] Therefore, by time-division driving the mode switching circuit 40b to switch between the first mode and the second mode at a predetermined period, the steering wheel grip detection device 3 can detect that the user's hands are gripping the steering wheel 1.

[0064] 5(b), the mode switching circuit 40b of the steering wheel grip detection device 3 can repeatedly switch among the first mode, the second mode, and the third mode at a predetermined cycle. For example, the mode switching circuit 40b may execute the first mode and the second mode, and then execute the third mode.

[0065] Specifically, after a predetermined period of time has elapsed while the mode switching circuit 40b is operating in the second mode, the mode switching circuit 40b switches from the second mode to the third mode. Specifically, the mode switching circuit 40b turns on the fifth switch 35 and the sixth switch 36 and turns off the other switches, causing the control circuit 40 to operate in the third mode. In the third mode, the capacitance sensor circuit 40a supplies a direct current to the second electrode 22, causing the second electrode 22 to function as a heater. In other words, the second electrode 22 is electrically connected to a battery 39 that supplies power to one end of the second electrode 22, causing the second electrode 22 to operate as a heater. In this case, because the sixth switch 36 is turned on, a direct current flows through the second electrode 22 and then escapes to ground 38. At this time, even if the user's hand is in contact with the steering cover 11 of the rim 2, the capacitance between the user's hand and the first electrode 21 cannot be measured because the second switch 32 is turned off. Furthermore, since the first switch 31 is OFF, the capacitance between the second electrode 22 and the core 2a cannot be measured.

[0066] During the period when the third mode is being executed, the steering wheel grip detection device 3 can warm the steering wheel 1 by causing the second electrode 22 to generate heat.

[0067] The period during which the third mode is executed is longer than the period during which the first mode is executed and the period during which the second mode is executed. For example, the period during which the third mode is executed is at least several tens of milliseconds. Therefore, it is possible to detect that the user's hands are gripping the steering wheel 1 while maintaining the temperature rise and heat retention of the steering wheel 1.

[0068] <Action and effect> Next, the operation and effect of the steering wheel grip detection device 3 in this embodiment will be described.

[0069] As described above, the steering wheel grip detection device 3 of technology 1 relating to this embodiment includes a first electrode 21 arranged on the rim 2 of the steering wheel 1, a second electrode 22 arranged on the rim 2 and located closer to the inner surface of the steering wheel 1 than the first electrode 21, and a control circuit 40, where the first electrode 21 has a larger projected area than the second electrode 22, and the control circuit 40 is switchable between a first mode in which the first electrode 21 is used as a sensor electrode and the second electrode 22 is used as a shield electrode, and a second mode in which the first electrode 21 is used as a shield electrode and the second electrode 22 is used as a sensor electrode.The control circuit 40 calculates a first mode capacitance detected by the first electrode 21 used as the sensor electrode in the first mode and a second mode capacitance detected by the second electrode 22 used as the sensor electrode in the second mode, and detects gripping of the steering wheel 1 based on the first mode capacitance and the second mode capacitance.

[0070] According to this, the capacitance C strTHD From the above, the capacitance C strHOD Therefore, the capacitance sensor circuit 40a is the first mode capacitance (capacitance C fgr +Capacitance C strHOD ) and calculate the capacitance C strHOD By subtracting the capacitance C fgr can be calculated.

[0071] Therefore, according to the present disclosure, it is possible to suppress a decrease in the robustness of grasp detection and achieve highly accurate grasp detection.

[0072] In particular, in conventional steering wheel grip detection devices, a third electrode serving as a shield electrode is disposed between the first electrode serving as a sensor electrode and the second electrode performing a heater function. However, in the present embodiment, the steering wheel grip detection device 3 is configured to detect gripping of the steering wheel 1 by switching between the first mode and the second mode, so it is not necessary to separately dispose a third electrode serving as a shield electrode on the steering wheel as in conventional steering wheel grip detection devices. Therefore, the steering wheel grip detection device 3 of the present disclosure can suppress an increase in the number of parts and a rise in the manufacturing cost of the steering wheel grip detection device 3.

[0073] In addition, in the steering wheel grip detection device 3 of Technology 2 according to this embodiment, the control circuit 40 includes a capacitance sensor circuit 40a having a sensor terminal 41 that can use the first electrode 21 as a sensor electrode in a first mode and the second electrode 22 as a sensor electrode in a second mode, and a shield terminal 42 that can use the second electrode 22 as a shield electrode in the first mode and the first electrode 21 as a shield electrode in the second mode. The control circuit 40 also includes a first switch 31 arranged between the sensor terminal 41 and the second electrode 22, a second switch 32 arranged between the sensor terminal 41 and the first electrode 21, a third switch 33 arranged between the shield terminal 42 and the second electrode 22, and a fourth switch 34 arranged between the shield terminal 42 and the first electrode 21. In the first mode, the control circuit 40 turns on the second switch 32 and the third switch 33 and turns off the other switches. In the second mode, the control circuit 40 turns on the first switch 31 and the fourth switch 34 and turns off the other switches. This is the steering wheel grip detection device 3 according to Technology 1.

[0074] According to this, it is possible to switch between the first mode and the second mode by controlling the first switch 31, the second switch 32, the third switch 33, and the fourth switch 34. Therefore, it is possible to detect whether the steering wheel 1 is being gripped, based on the first mode capacitance and the second mode capacitance.

[0075] Furthermore, in the steering wheel grip detection device 3 of Technology 3 according to this embodiment, the control circuit 40 is the steering wheel grip detection device 3 described in Technology 1 or 2, which is further switchable to a third mode in which the second electrode 22 operates as a heater.

[0076] According to this, by executing the third mode, the second electrode 22 can be operated as a heater. Therefore, the second electrode 22 can simultaneously realize the heater function of warming the steering wheel 1 and the function of detecting the user's grip on the steering wheel 1.

[0077] Furthermore, in the steering wheel grip detection device 3 of Technology 4 according to this embodiment, the second electrode 22 is connected to a battery 39 that supplies power to one end of the second electrode 22 when the second electrode 22 operates as a heater, and the other end of the second electrode 22 can be connected to ground 38. The steering wheel grip detection device 3 is also provided with a fifth switch 35 that is arranged between the battery 39 and one end of the second electrode 22, and a sixth switch 36 that is arranged between ground 38 and the other end of the second electrode 22. In the third mode, the control circuit 40 turns on the fifth switch 35 and the sixth switch 36 and turns off the other switches, which is the steering wheel grip detection device 3 described in Technology 3.

[0078] According to this, in the third mode, power can be supplied from the battery 39 to the second electrode 22, so that the second electrode 22 can generate heat and function as a heater to warm the steering wheel 1.

[0079] Furthermore, in the steering wheel grip detection device 3 of Technology 5 according to this embodiment, the control circuit 40 is the steering wheel grip detection device 3 described in any one of Technologies 1 to 4, which has a mode switching circuit 40b that switches between the first mode and the second mode at a predetermined period.

[0080] This allows for accurate detection of when the user's hands are gripping the steering wheel 1 and when the user's hands have been released from the steering wheel 1 by switching between the first mode and the second mode at a predetermined cycle.

[0081] Furthermore, in the steering wheel grip detection device 3 of Technology 6 according to this embodiment, the control circuit 40 is the steering wheel grip detection device 3 described in Technology 3 or 4, which has a mode switching circuit 40b that switches between the first mode, the second mode, and the third mode at a predetermined period.

[0082] According to this, by switching between the first mode, the second mode and the third mode at a predetermined period, the steering wheel 1 can be warmed by the second electrode 22, and it is possible to accurately detect when the user's hands are gripping the steering wheel 1 and when the user's hands have released the steering wheel 1.

[0083] (Other variations) While the steering wheel grip detection device according to the present disclosure has been described above based on the above-described embodiments, the present disclosure is not limited to these embodiments. As long as the modifications do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art may also be included in the scope of the present disclosure.

[0084] For example, the steering wheel grip detection device 3 according to the present disclosure may include a plurality of first electrodes 21, or may include a plurality of second electrodes 22. Furthermore, the steering wheel grip detection device 3 may include one first electrode 21 and a plurality of second electrodes, or may include a plurality of first electrodes 21 and one second electrode. In these cases, too, the control circuit 40 may switch between the first mode and the second mode at a predetermined cycle, or may switch between each of the first mode, the second mode, and the third mode at a predetermined cycle.

[0085] Furthermore, a plurality of steering wheel grip detectors 3 according to the present disclosure may be independently arranged on the steering wheel 1. For example, when the steering wheel 1 is in the normal position (steering angle 0°), a steering wheel grip detector 3 may be arranged on each of the left and right halves. Naturally, three or more steering wheel grip detectors 3 may be arranged on the steering wheel 1.

[0086] In addition, in the steering wheel grip detection device 3 according to the present disclosure, the capacitance sensor circuit 40a and the mode switching circuit 40b are mounted on a single control circuit 40, but the capacitance sensor circuit 40a and the mode switching circuit 40b may be separate, independent circuits.

[0087] In addition, this disclosure also includes forms obtained by making various modifications to the above-mentioned embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in the embodiments within the scope that does not deviate from the intent of this disclosure. [Industrial Applicability]

[0088] The steering wheel grip detection device of the present disclosure can be applied to, for example, a steering wheel of a vehicle. [Explanation of symbols]

[0089] 1 steering wheel 2 rims 3. Steering wheel grip detection device 21 1st electrode 22 2nd electrode 31 First Switch 32 Second Switch 33 Third Switch 34 4th Switch 35 5th Switch 36 6th Switch 38 Grand 39 Battery 39a Battery terminal 40 Control circuit 40a Capacitive Sensor Circuit 40b Mode switching circuit 40c power circuit 41 Sensor terminal 42 Shield terminal

Claims

1. a first electrode disposed on the rim of the steering wheel; a second electrode disposed on the rim and positioned on an inner layer of the steering wheel than the first electrode; a control circuit; the first electrode has a larger projected area than the second electrode, The control circuit a first mode in which the first electrode is a sensor electrode and the second electrode is a shield electrode; a second mode in which the first electrode is a shield electrode and the second electrode is a sensor electrode; determining a first mode capacitance detected by the first electrode serving as a sensor electrode in the first mode and a second mode capacitance detected by the second electrode serving as a sensor electrode in the second mode; detecting gripping of the steering wheel based on the first mode capacitance and the second mode capacitance; Steering wheel grip detection device.

2. the control circuit includes a capacitance sensor circuit having a sensor terminal that can use the first electrode as a sensor electrode in the first mode and the second electrode as a sensor electrode in the second mode, and a shield terminal that can use the second electrode as a shield electrode in the first mode and the first electrode as a shield electrode in the second mode; moreover, a first switch disposed between the sensor terminal and the second electrode; a second switch disposed between the sensor terminal and the first electrode; a third switch disposed between the shield terminal and the second electrode; a fourth switch disposed between the shield terminal and the first electrode; The control circuit In the first mode, the second switch and the third switch are turned ON, and the other switches are turned OFF. In the second mode, the first switch and the fourth switch are turned ON, and the other switches are turned OFF. The steering wheel grip detection device according to claim 1 .

3. The control circuit is further switchable to a third mode in which the second electrode operates as a heater. The steering wheel grip detection device according to claim 1 or 2.

4. the second electrode is connected to a battery that supplies power to one end of the second electrode when the second electrode operates as a heater; The other end of the second electrode can be connected to ground, a fifth switch disposed between the battery and one end of the second electrode; a sixth switch disposed between the ground and the other end of the second electrode; In the third mode, the control circuit turns on the fifth switch and the sixth switch and turns off the other switches. The steering wheel grip detection device according to claim 3 .

5. the control circuit has a mode switching circuit that switches between the first mode and the second mode at a predetermined cycle. The steering wheel grip detection device according to claim 1 or 2.

6. the control circuit has a mode switching circuit that switches among the first mode, the second mode, and the third mode at a predetermined cycle. The steering wheel grip detection device according to claim 3 .

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