Steering wheel unit

Abstract

Since there is necessarily a dead zone where a sensor cannot be placed due to appearance and design restrictions of a steering wheel unit, the purpose of the present invention is to provide a steering wheel unit capable of determining whether there is contact of a hand of an operator even in a dead zone where there is no sensor.　In this steering wheel unit, if an electrostatic capacitance measured by a capacitance measurement unit is at least a first threshold when set in a self-capacitance detection mode by a mode switching unit, it is determined that a hand of an operator is contacting a position, on a rim, that overlaps at least one of a plurality of electrodes. If the electrostatic capacitance is at least a second threshold, which is lower than the first threshold, and is less than the first threshold, the mode is switched from the self-capacitance detection mode to a mutual-capacitance detection mode. Thereafter, if the electrostatic capacitance measured by the capacitance measurement unit in the mutual-capacitance detection mode is at least a third threshold, it is determined that a hand of the operator is contacting a position, on the rim, that overlaps with a gap between the plurality of electrodes.

Description

[Technical Field]

[0001] The present disclosure relates to a steering wheel unit. [Background technology]

[0002] There have been steering wheel units in the past that use sensors to detect human body contact with a vehicle steering wheel. One steering wheel unit is characterized in that it includes a capacitance sensor attached to the steering wheel that detects the magnitude of capacitance associated with human body contact with the steering wheel, the capacitance sensor being arranged on the outer periphery of the rim of the steering wheel to form a sensing area that detects human body contact with the steering wheel, and dead zones that do not detect human body contact with the steering wheel being formed in a left portion located relatively to the left of the rim when the steering wheel is in a neutral position, and in a right portion opposite the left portion across the center of the rim (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-23009 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional steering wheel units cannot detect a hand touching the steering wheel if the position where the hand is touching the steering wheel is in a dead zone. Furthermore, capacitance sensors are designed to detect self-capacitance. Conventional steering wheel units have a dead zone to prevent false detections and erroneous operation when detecting self-capacitance, but the dead zone does not allow the detection of a hand touching the steering wheel.

[0005] To provide a steering wheel unit capable of determining whether an operator's hand is in contact with the steering wheel even in a dead zone where no sensor exists, since a dead zone where no sensor can be placed is always present due to design restrictions of the steering wheel unit. [Means for solving the problem]

[0006] A steering wheel unit according to an embodiment of the present disclosure includes a steering wheel having a rim, spokes, and a plurality of electrodes arranged to cover the rim with gaps therebetween; a mode switching unit that switches between a self-capacitance detection mode and a mutual capacitance detection mode for the plurality of electrodes; a capacitance measurement unit that measures capacitance due to the plurality of electrodes; and a contact determination unit that determines whether an operator's hand is in contact with the steering wheel based on the capacitance measured by the capacitance measurement unit, wherein in the mutual capacitance detection mode, the mode switching unit selects a drive electrode from the plurality of electrodes and selects an electrode adjacent to the selected drive electrode as a detection electrode, and the contact determination unit determines whether an operator's hand is in contact with the steering wheel based on the capacitance measured by the capacitance measurement unit. When the self-capacitance detection mode is set by the unit, if the capacitance measured by the capacitance measurement unit is equal to or greater than a first threshold, it is determined that the operator's hand is in contact with the rim at a position overlapping with at least one of the plurality of electrodes; if the capacitance measured by the capacitance measurement unit is equal to or greater than a second threshold that is smaller than the first threshold but is less than the first threshold, the mode switching unit switches from the self-capacitance detection mode to the mutual capacitance detection mode, and then, if the capacitance measured by the capacitance measurement unit in the mutual capacitance detection mode is equal to or greater than a third threshold, it is determined that the operator's hand is in contact with the rim at a position overlapping with a gap between the plurality of electrodes. [Effects of the Invention]

[0007] A steering wheel unit can be provided that can determine whether or not an operator's hand is in contact with the steering wheel rim in a dead zone where no sensor is present. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a steering wheel included in a steering wheel unit according to an embodiment; [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the cross section AA in FIG. [Figure 3] FIG. 2 is a diagram illustrating an example of a configuration of a steering wheel unit according to an embodiment. [Figure 4] 10 is a flowchart illustrating an example of processing executed by a HODECU. [Figure 5A] FIG. 10 is a diagram illustrating a threshold value Th1 used by a contact determination unit. [Figure 5B] FIG. 10 is a diagram illustrating a threshold value Th2 used by the contact determination unit. [Figure 6] FIG. 10 is a diagram showing a threshold value Th4 used by the contact determination unit. [Figure 7A] FIG. 10 is a diagram showing a threshold value Th3 set by the contact determination unit. [Figure 7B] FIG. 10 is a diagram showing a threshold value Th5 set by the contact determination unit. [Figure 8] FIG. 10 is a diagram illustrating a configuration of a sensor according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the steering wheel unit of the present disclosure is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing an example of a steering wheel 110 included in a steering wheel unit 100 of an embodiment. The steering wheel 110 has a rim 110A, spokes 110B, a hub 110C, a steering core 111, a cover 112, and sensors 113A, 113B, 113C, and 113D. The sensors 113A to 113D are examples of a plurality of electrodes. In the following, when describing the configuration of the steering wheel 110, unless otherwise specified, the configuration will be described as seen from the driver's seat when the steering wheel 110 is attached to a vehicle and in a neutral position. The driver's seat side of the steering wheel 110 will be referred to as the front side, and the vehicle front side of the steering wheel 110 will be referred to as the rear side.

[0011] The left side of Fig. 1 shows a steering wheel 110. The center of Fig. 1 shows an exploded view of the steering wheel 110. In the center of Fig. 1, the cover 112 is omitted to make it easier to see the arrangement of the sensors 113A to 113D. The right side of Fig. 1 shows an enlarged view of a portion of the rim 110A of the steering wheel 110. The right side of Fig. 1 shows a portion of the rim 110A in a straight line.

[0012] Although FIG. 1 shows two spokes 110B extending laterally from a hub 110C at the center of the steering wheel 110, the number of spokes 110B may be any number. The rim 110A does not have to be circular, but may be rectangular or D-shaped, or may not be circular. The steering core 111 has a shape similar to that of the steering wheel 110 and has a rim and spokes. The rim and spokes of the steering core 111 correspond to the rim 110A and spokes 110B of the steering wheel 110.

[0013] The skin 112 is a member that covers the rim of the steering core 111 and is the part that comes into direct contact with the hands of the vehicle operator (driver). The skin 112 is made of, for example, genuine leather, artificial leather, resin, or the like.

[0014] As an example, skin 112 is integrated with sensors 113A-113D and covers the rim of steering core 111 with sensors 113A-113D positioned between skin 112 and the rim of steering core 111. When skin 112 integrated with sensors 113A-113D is used to cover the rim of steering core 111, it becomes rim 110A of steering wheel 110. Furthermore, when decorative members made of resin or the like are attached to the spokes of steering core 111, they become spokes 110B of steering wheel 110.

[0015] The cover 112 integrated with the sensors 113A to 113D is a sheet-like member before being attached to the rim of the steering core 111. The cover 112 integrated with the sensors 113A to 113D is sewn to the rim of the steering core 111 while covering the rim, thereby forming a seam 112A. The seam 112A is formed along the circumferential direction of the rim 110A of the steering wheel 110. The seam 112A is formed, for example, on the inner periphery side, the inner periphery side and the outer periphery side, or the outer periphery side of the rim 110A of the steering wheel 110.

[0016] The sensors 113A to 113D are electrodes made of a conductor, and are provided to detect whether the operator's hands are in contact with the steering wheel 110. A cable 114 that is connected to a HODECU (Hands Off Detection Electronic Control Unit) or the like is connected to the sensors 113A to 113D. For example, electrodes made of a resin film or the like coated with silver paste, or electrodes made of a resin film or the like coated with aluminum foil or copper foil can be used as the sensors 113A to 113D.

[0017] For example, sensor 113A is located on the front side of the right half of rim 110A, and sensor 113B is located on the front side of the left half of rim 110A. Also, for example, sensor 113C is located on the rear side of the right half of rim 110A, and sensor 113D is located on the rear side of the left half of rim 110A.

[0018] The capacitance between sensors 113A-113D and the operator's hand changes depending on whether the operator's hand is in contact with rim 110A of steering wheel 110. The capacitance between sensors 113A-113D and the operator's hand differs depending on whether the operator's hand is gripping rim 110A of steering wheel 110 or lightly touching it. For example, the capacitance when gripping is greater than the capacitance when lightly touching it.

[0019] When cover 112 integrated with sensors 113A-113D is attached to the rim of steering core 111, sensors 113A-113D are not present at seam 112A, and therefore the capacitance between sensors 113A-113D and the operator's hand differs when the operator's hand is in contact with seam 112A of rim 110A of steering wheel 110 and when the operator's hand is in contact with a portion of rim 110A other than seam 112A (a portion overlapping with at least one of sensors 113A-113D). A portion without sensors 113A-113D, such as seam 112A, is an example of a position that overlaps with gaps between multiple electrodes on rim 110A of steering wheel 110.

[0020] Also, here, a case will be described in which the portion of rim 110A of steering wheel 110 where sensors 113A to 113D are not present is seam 112A, but there may be portions other than seam 112A where sensors 113A to 113D are not present. For example, if upholstery 112 is not sewn but is glued, the portion shown as seam 112A will be the seam of upholstery 112, and there may be a portion at the seam where sensors 113A to 113D are not present.

[0021] Furthermore, for example, if the decorative member of spoke 110B of steering wheel 110 is arranged to extend around rim 110A, it is not possible to attach cover 112 integrated with sensors 113A-113D to a portion of rim 110A of steering wheel 110, and therefore even if there is no seam 112A, there may be portions of rim 110A of steering wheel 110 where sensors 113A-113D are not present.

[0022] Furthermore, when seam 112A is not present on the outer periphery of rim 110A, the gap between sensor 113A located on the front side of the right half of rim 110A and sensor 113C located on the back side of the right half of rim 110A is a portion where no sensor is present. When seam 112A is not present on the outer periphery of rim 110A, the gap between sensor 113B located on the front side of the left half of rim 110A and sensor 113D located on the back side of the left half of rim 110A is a portion where no sensor is present. Furthermore, the gap between sensors 113A and 113C located on the front side of rim 110A and the gap between sensors 113B and 113D located on the back side of rim 110A are also portions where no sensor is present.

[0023] The steering wheel unit 100 of the embodiment can detect that the operator's hand is in contact with the rim 110A of the steering wheel 110 even when the operator's hand is in contact with a part of the rim 110A of the steering wheel 110 where no sensors 113A to 113D are present, such as the seam 112A. Details will be described below.

[0024] <Outline of Capacitance Detection Method in Steering Wheel Unit 100 of the Embodiment> Fig. 2 is a diagram showing an example of the configuration of the AA cross section in Fig. 1. Here, an outline of a method for detecting capacitance in steering wheel unit 100 of an embodiment will be described using Fig. 2. In Fig. 2, in order to represent the capacitance between the operator's hand H and sensor 113A or 113C with a capacitor symbol, the hand H is shown separated from upholstery 112 or seam 112A, but the description will be given assuming that the hand is in contact with upholstery 112 or seam 112A.

[0025] As shown in Fig. 2, for example, rim 110A of steering wheel 110 has seam 112A on the inner periphery (left side in Fig. 2) and a dead zone where no sensors are present on the outer periphery (right side in Fig. 2). Seam 112A on the inner periphery and the dead zone where no sensors are present on the outer periphery correspond to the positions of the gaps between sensors 113A and 113C. Here, the right half of steering wheel 110 where sensors 113A and 113C are located will be described, but the same applies to the left half where sensors 113B and 113D are located, the front where sensors 113A and 113B are located, and the back where sensors 113C and 113D are located.

[0026] In the self-capacitance detection mode, the steering wheel unit 100 selects the sensor 113A or 113C as the detection electrode and measures the capacitance between the detection electrode and ground. In the self-capacitance detection mode, the detection electrode also functions as a drive electrode. In the self-capacitance detection mode, if a relatively large capacitance can be measured, it is determined that the hand H is in contact with the steering wheel 110 at a position overlapping the sensor 113A or 113C.

[0027] Furthermore, if the steering wheel unit 100 cannot measure a relatively large capacitance through sensor 113A or 113C in self-capacitance detection mode, it switches to mutual capacitance detection mode. Then, the steering wheel unit 100 selects one of sensors 113A or 113C as a drive electrode and selects the electrode adjacent to the drive electrode (the other of sensors 113A and 113C) as a detection electrode, and measures the capacitance between the drive electrode and the detection electrode. If the steering wheel unit 100 can measure a relatively large capacitance in mutual capacitance detection mode, it determines that the hand H is in contact with the steering wheel 110 at a position overlapping with seam 112A or a dead zone where no sensor is present.

[0028] <Configuration of steering wheel unit 100> FIG. 3 is a diagram showing an example of the configuration of a steering wheel unit 100 according to an embodiment. The steering wheel unit 100 includes a steering wheel 110, a capacitance measurement unit 120, and a HODECU 130. The HODECU 130 has a mode switching unit 131 and a contact determination unit 132. The HODECU 130 is connected to an ADASECU (Advanced Driver-Assistance System Electronic Control Unit) 200. The ADASECU 200 is a device that controls a system that provides advanced driving assistance, such as an autonomous driving system, for example. The autonomous driving system may be level 3 or higher out of levels 0 to 5 of autonomous driving defined by the Society of Automotive Engineers of Japan (JSAE).

[0029] 3 shows only the sensors 113A to 113D and the seam 112A for the steering wheel 110. The seam 112A is a dead zone where the sensors 113A to 113D are not present.

[0030] The capacitance measurement unit 120 is provided between the sensors 113A to 113D and the contact determination unit 132 of the HODECU 130, and is a measurement circuit that converts analog outputs from the sensors 113A to 113D into digital form and outputs the digitally converted capacitance to the contact determination unit 132. The capacitance that is converted and output by the capacitance measurement unit 120 is a digitally converted value (raw value) before the HODECU 130 determines the difference value (ΔAD) from a predetermined reference value.

[0031] The HODECU 130 is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. The mode switching unit 131 and the contact determination unit 132 represent the functions of the program executed by the HODECU 130 as functional blocks.

[0032] Mode switching unit 131 selects sensors 113A to 113D as drive electrodes or detection electrodes, and switches between a self-capacitance detection mode and a mutual capacitance detection mode. In the self-capacitance detection mode, mode switching unit 131 selects each of sensors 113A to 113D as a detection electrode in a time-division manner, and the capacitance is measured as self-capacitance by capacitance measurement unit 120. At this time, the remaining three sensors not used for detecting capacitance may be used as shields.

[0033] Alternatively, each of the sensors 113A to 113D may be simultaneously selected as a detection electrode, and the electrostatic capacitance may be measured as a self-capacitance by the capacitance measuring unit 120. In this case, no shield is set.

[0034] Here, shielding means driving a sensor that is not set as a detection electrode and is not used for capacitance detection at an arbitrary potential, which may be the ground level (0V).

[0035] Furthermore, in the mutual capacitance detection mode, mode switching unit 131 selects a drive electrode from sensors 113A to 113D and selects a sensor adjacent to the selected drive electrode as a detection electrode. Sensors 113A to 113D are adjacent to one another in a direction connecting the front and back of steering wheel 110 or in the circumferential direction of steering wheel 110. Therefore, mode switching unit 131 may select, for example, any one of sensors 113A to 113D as a drive electrode and select a sensor adjacent to the selected drive electrode as a detection electrode. In the mutual capacitance detection mode, capacitance measurement unit 120 measures the electrostatic capacitance between the drive electrode and the detection electrode as the mutual capacitance.

[0036] The contact determination unit 132 determines whether or not the operator's hand H is in contact with the rim 110A of the steering wheel 110, based on the capacitance measured by the capacitance measurement unit 120. Details of the processing performed by the contact determination unit 132 will be described using the flowchart in FIG.

[0037] <Flowchart> FIG. 4 is a flowchart illustrating an example of processing executed by the HODECU 130.

[0038] When the contact determination unit 132 starts processing, the mode switching unit 131 sets the self-capacitance detection mode, and the contact determination unit 132 acquires the capacitance measured in time division order in each of all the sensors 113A to 113D by the capacitance measurement unit 120 (step S1). In step S1, the contact determination unit 132 acquires a digital conversion value (raw value) that is the capacitance acquired by the capacitance measurement unit 120.

[0039] In step S1, the mode switching unit 131 may drive the three sensors other than the sensor that detects capacitance as shields. Such processing can be performed by the contact determination unit 132 instructing the mode switching unit 131. By driving the three sensors other than the sensor that detects capacitance as shields, it is possible to suppress the influence of the ground and the like around the sensors that detect capacitance, and it is possible to stably detect capacitance.

[0040] The contact determination unit 132 subtracts a predetermined reference value from the digitally converted value (raw value) to obtain a capacitance as a difference value (ΔAD), and determines whether any of the obtained capacitances is equal to or greater than a threshold value Th2 (step S2). The threshold value Th2 is an example of a second threshold value, and is set to a capacitance that can determine whether the hand H is in contact with any part of the rim 110A of the steering wheel 110, including the seam 112A and the dead zone where no sensor is present, in the self-capacitance detection mode. Even if the hand H is in contact with the dead zone of the rim 110A of the steering wheel 110, the capacitance of at least one of the sensors 113A-113D increases to some extent. Therefore, the threshold value Th2 is used to detect whether the hand H is in contact with any part of the rim 110A of the steering wheel 110, including the seam 112A and the dead zone where no sensor is present.

[0041] If the contact determination unit 132 determines that the calculated capacitances include a capacitance equal to or greater than the threshold value Th2 (S2: Yes), it then determines whether the capacitance (ΔAD) is equal to or greater than the threshold value Th1 (step S3). Threshold value Th1 is an example of a first threshold, and is set to a capacitance that can determine whether the hand H is in contact with a position on the rim 110A of the steering wheel 110 that overlaps with at least one of the sensors 113A-113D. Here, the position on the rim 110A that overlaps with at least one of the sensors 113A-113D is a portion of the rim 110A other than the seam 112A or the dead zone where no sensor is present.

[0042] In particular, threshold value Th1 is set assuming detection of a state in which hand H is firmly gripping the rim 110A other than seam 112A or a portion other than the dead zone where no sensor is present. When hand H is firmly gripping the rim 110A other than seam 112A or a portion other than the dead zone where no sensor is present, an extremely large capacitance is obtained, so the processing of step S3 is provided to determine whether hand H is in contact with steering wheel 110.

[0043] Furthermore, in step S2, after determining that hand H is in contact with somewhere on rim 110A of steering wheel 110, including the dead zone where no seam 112A or sensor is present (S2: Yes), it is possible to determine whether the position where hand H is in contact is the dead zone where no seam 112A or sensor is present by determining whether hand H is in contact with any part of rim 110A other than the dead zone where no seam 112A or sensor is present.

[0044] If the contact determination unit 132 determines that the capacitance is equal to or greater than the threshold value Th1 (S3: Yes), it determines that the hand H is in contact with the rim 110A of the steering wheel 110 (step S4). When the contact determination unit 132 completes the processing of step S4, the HODECU 130 transmits the determination result to the ADASECU 200 and returns the flow to the start.

[0045] Furthermore, if contact determination unit 132 determines in step S3 that the capacitance is not equal to or greater than threshold value Th1 (S3: No), it causes mode switching unit 131 to switch to mutual capacitance detection mode (step S5). Mode switching unit 131 selects, as a driving electrode, a sensor from sensors 113A to 113D that detected a capacitance equal to or greater than threshold value Th2 in step S2, and selects, as a detection electrode, a sensor adjacent to the sensor serving as the driving electrode.

[0046] For example, if sensor 113A is selected as the drive electrode, sensor 113C adjacent to sensor 113A across the rim of steering core 111, or sensor 113B located on the opposite side of the rim of steering core 111, may be selected as the detection electrode. Furthermore, if sensor 113C is selected as the drive electrode, sensor 113A adjacent to sensor 113C across the rim of steering core 111, or sensor 113D located on the opposite side of the rim of steering core 111, may be selected as the detection electrode. Similarly, if sensor 113B is selected as the drive electrode, sensor 113D adjacent to sensor 113B across the rim of steering core 111, or sensor 113A located on the opposite side of the rim of steering core 111, may be selected as the detection electrode. Furthermore, if sensor 113D is selected as the drive electrode, sensor 113B adjacent to sensor 113D across the rim of steering core 111, or sensor 113C located on the opposite side of the rim of steering core 111, may be selected as the detection electrode.

[0047] The flow proceeds to step S5 when the capacitance is equal to or greater than threshold value Th2 in step S2 and becomes less than threshold value Th1 in step S3, in which case a relatively large capacitance is obtained, but hand H is not in contact with the part of rim 110A of steering wheel 110 that overlaps with sensors 113A to 113D, and there is a possibility that hand H is in contact with, for example, seam 112A or a dead zone where no sensor exists.

[0048] The contact determination unit 132 uses the drive electrodes and detection electrodes selected in step S5 to obtain the capacitance between the drive electrodes and detection electrodes (step S6).

[0049] In step S5, instead of selecting the sensor that detected a capacitance equal to or greater than threshold value Th2 in step S2 as the drive electrode, each of sensors 113A to 113D may be selected as the drive electrode, and the drive electrodes and detection electrodes may be selected in a round-robin fashion. In this case, the process of selecting the drive electrodes and detection electrodes in step S5 and the process of detecting the capacitance between the drive electrodes and detection electrodes in step S6 may be repeatedly performed.

[0050] Here, selecting the drive electrodes and detection electrodes in a round-robin manner means selecting all sensors in turn as drive electrodes and selecting sensors adjacent to the selected drive electrodes as detection electrodes, thereby measuring the capacitance (mutual capacitance) between the drive electrodes and detection electrodes when all sensors have been selected as drive electrodes.

[0051] The contact determination unit 132 determines whether the acquired capacitance is equal to or greater than a threshold value Th3 (step S7). The threshold value Th3 is an example of a third threshold value, and is set to a capacitance that allows determination of whether the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present in the mutual capacitance detection mode.

[0052] If the contact determination unit 132 determines that the acquired capacitance is equal to or greater than the threshold value Th3 (S7: Yes), it determines that the hand H is in contact with the rim 110A of the steering wheel 110 (step S4). The flow proceeds to step S4 via step S7 when the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present.

[0053] Furthermore, if the contact determination unit 132 determines in step S7 that the acquired capacitance is not equal to or greater than the threshold value Th3 (S7: No), it determines that the hand H is not in contact with the rim 110A of the steering wheel 110 (step S8). For example, if the hand H was in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor was present when the capacitance was acquired in step S1, but the hand H was no longer in contact with the rim 110A of the steering wheel 110 when the capacitance was acquired in step S6, the flow proceeds from step S7 to step S8. When the contact determination unit 132 completes the processing of step S8, the HODECU 130 transmits the determination result of the contact determination unit 132 to the ADASECU 200 and returns the flow to the start.

[0054] Furthermore, if the contact determination unit 132 determines in step S2 that the calculated capacitances (ΔAD) do not include a capacitance equal to or greater than the threshold value Th2 (S2: No), it determines whether the capacitances (raw values) of the sensors 113A-113D acquired in step S1 include a capacitance equal to or greater than a threshold value Th4, which is greater than the initial value (step S9). The threshold value Th4 is an example of a fourth threshold. The initial value is the output value of each of the sensors 113A-113D when the hand H is not in contact with the steering wheel 110. Such an initial value is determined by the structure of the sensors 113A-113D, and may be stored in an internal memory of the HODECU 130, for example. When setting the value of the threshold value Th4, the sensitivity for determining whether the hand H is in contact with the steering wheel 110 can be adjusted depending on how much of an increase from the initial value is expected.

[0055] Threshold value Th4 is set to a capacitance that allows determination in self-capacitance detection mode whether hand H is lightly touching anywhere on rim 110A of steering wheel 110, including dead zones where no seam 112A or sensors are present. Step S9 is a process that determines which sensor (one of 113A to 113D) hand H is closest to, if hand H is lightly touching anywhere on rim 110A, by looking at the increase in capacitance (raw value) of sensors 113A to 113D acquired in step S1. If hand H is lightly touching somewhere on rim 110A or hand H is close to rim 110A of steering wheel 110, step S9 narrows down to one sensor.

[0056] When contact determination unit 132 determines that the capacitance of sensors 113A to 113D is equal to or greater than threshold value Th4 (S9: Yes), contact determination unit 132 causes mode switching unit 131 to switch to mutual capacitance detection mode (step S10). Mode switching unit 131 selects, as a driving electrode, a sensor of sensors 113A to 113D determined to have a capacitance equal to or greater than threshold value Th4 in step S9, and selects, as a detection electrode, a sensor adjacent to the sensor serving as the driving electrode.

[0057] The contact determination unit 132 uses the drive electrodes and detection electrodes selected in step S10 to obtain the capacitance between the drive electrodes and detection electrodes (step S11).

[0058] The contact determination unit 132 determines whether the acquired capacitance is equal to or greater than a threshold value Th5 (step S12). The threshold value Th5 is an example of a fifth threshold value, and is set to a capacitance that allows determination of whether the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present in the mutual capacitance detection mode. The process of step S12 is the same as that of step S7, but the threshold value is different. The flow proceeds to step S12 when it is determined that the capacitance (ΔAD) calculated in step S2 does not include a capacitance equal to or greater than the threshold value Th2 (S2: No), that is, when the hand H is not in contact with any part of the rim 110A of the steering wheel 110, including the seam 112A or the dead zone where no sensor is present.

[0059] The threshold value Th3 used in step S7 is a capacitance that can determine whether the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present in the mutual capacitance detection mode. In contrast, the threshold value Th5 used in step S12 is a capacitance that can determine whether the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present in the mutual capacitance detection mode, and is therefore smaller than the threshold value Th3.

[0060] If the contact determination unit 132 determines that the acquired capacitance is equal to or greater than the threshold value Th5 (S12: Yes), the HODECU 130 determines that the hand H is in contact with the rim 110A of the steering wheel 110 (step S4). The flow proceeds to step S4 via step S12 when the hand H is in contact with a dead zone of the rim 110A of the steering wheel 110, such as the seam 112A, where no sensor is present.

[0061] Furthermore, if the contact determination unit 132 determines that the acquired capacitance is not equal to or greater than the threshold value Th5 (S12: No), the HODECU 130 determines that the hand H is not in contact with the rim 110A of the steering wheel 110 (step S8). For example, if the hand H was very lightly in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor was present when the capacitance was acquired in step S1, but the hand H was no longer in contact with the rim 110A of the steering wheel 110 when the capacitance was acquired in step S11, the flow proceeds from step S12 to step S8.

[0062] Furthermore, if the contact determination unit 132 determines in step S9 that none of the capacitances of the sensors 113A to 113D is equal to or greater than the threshold value Th4 (S9: No), the HODECU 130 determines that the hand H is not in contact with the rim 110A of the steering wheel 110 (step S8). For example, if the hand H is away from the rim 110A of the steering wheel 110, the flow proceeds from step S9 to step S8.

[0063] <Explanation of each threshold> <Threshold Th1> Fig. 5A is a diagram showing a threshold value Th1 used in the process of step S3 by the contact determination unit 132. In Fig. 5A, the vertical axis represents the capacitance ΔAD as a difference value (ΔAD) obtained by subtracting a predetermined reference value from a digitally converted value (raw value).

[0064] The threshold value Th1 is set to detect a state in which, in the self-capacitance detection mode, the hand H is firmly gripping the rim 110A other than the seam 112A and the dead zone where no sensor is present, and is therefore set to the largest value among the threshold values ​​used by the contact determination unit 132 in the flowchart of Figure 4.

[0065] If the contact determination unit 132 determines in step S2 that the calculated capacitances (ΔAD) include a capacitance equal to or greater than the threshold value Th2 (S2: Yes), the contact determination unit 132 determines whether the capacitance is equal to or greater than the threshold value Th1 (step S3). If the capacitance ΔAD1 shown in FIG. 5A is equal to or greater than the threshold value Th1, the contact determination unit 132 determines that the hand H is in contact with the rim 110A of the steering wheel 110 (step S4).

[0066] On the other hand, if the capacitance ΔAD2 shown in FIG. 5A is less than the threshold value Th1, the contact determination unit 132 determines that the hand H may not be in contact with the rim 110A of the steering wheel 110, and proceeds to step S5.

[0067] <Threshold Th2> Fig. 5B is a diagram showing a threshold value Th2 used in the process of step S2 by the contact determination unit 132. In Fig. 5B, the vertical axis represents the capacitance ΔAD as a difference value (ΔAD) obtained by subtracting a predetermined reference value from a digitally converted value (raw value).

[0068] Threshold value Th2 is set to a capacitance that can determine, in the self-capacitance detection mode, whether hand H is in contact with any part of rim 110A of steering wheel 110, including seam 112A and dead zones where no sensor is present, and is lower than threshold value Th1 so that it can also determine whether hand H is in contact with the dead zone of rim 110A. Threshold value Th1 is also shown in Figure 5B.

[0069] In step S2, the contact determination unit 132 determines whether any capacitance is equal to or greater than threshold value Th2 among all capacitances measured by the capacitance measurement unit 120 in step S1. If any capacitance is equal to or greater than threshold value Th2, such as capacitance ΔAD3 shown in Fig. 5B, the contact determination unit 132 advances the flow to step S3. On the other hand, if all capacitances measured by the capacitance measurement unit 120 in step S1 are less than threshold value Th2, such as capacitance ΔAD4 shown in Fig. 5B, the contact determination unit 132 advances the flow to step S9.

[0070] <Threshold Th4> Fig. 6 is a diagram showing the threshold value Th4 used in the process of step S9 by the contact determination unit 132. In Fig. 6, the vertical axis represents the capacitance (raw value) measured by the capacitance measurement unit 120 in the self-capacitance detection mode.

[0071] The threshold value Th4 is set to a capacitance that can determine whether the hand H is lightly touching somewhere on the rim 110A of the steering wheel 110 in the self-capacitance detection mode, and is not a difference value (ΔAD) from a predetermined reference value, but a digitally converted value (raw value) before the difference value (ΔAD) is calculated. This is to capture slight changes in the capacitance (raw value) that is digitally converted and output by the capacitance measurement unit 120.

[0072] If the contact determination unit 132 determines in step S9 that the capacitances of the sensors 113A to 113D include a capacitance equal to or greater than the threshold value Th4 (S9: Yes), the flow proceeds to step S10 because there is a possibility that the hand H is lightly touching somewhere on the rim 110A of the steering wheel 110. If the capacitance is equal to or greater than the threshold value Th4, as in the case of capacitance Raw1 shown in FIG. 6, the contact determination unit 132 proceeds to step S10.

[0073] On the other hand, if the capacitance Raw2 shown in FIG. 6 is less than the threshold value Th4, the contact determination unit 132 determines that the hand H is not in contact with the rim 110A of the steering wheel 110 (step S8).

[0074] <Threshold Th3> Fig. 7A is a diagram showing threshold value Th3 used in the process of step S7 by contact determination unit 132. In Fig. 7A, the vertical axis represents capacitance ΔAD measured by capacitance measurement unit 120 in the mutual capacitance detection mode.

[0075] The threshold value Th3 is set to an electrostatic capacitance that makes it possible to determine whether the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present in the mutual capacitance detection mode.

[0076] 7A is equal to or greater than threshold value Th3 in step S7, contact determination unit 132 determines that hand H is in contact with rim 110A of steering wheel 110 (step S4). After determining in step S2 that at least hand H is in contact with somewhere on rim 110A and determining in step S3 that hand H is not in contact with a position that overlaps with at least one of sensors 113A to 113D, a state in which hand H is in contact with seam 112A of rim 110A of steering wheel 110 or a dead zone where no sensor is present is detected.

[0077] Furthermore, if the contact determination unit 132 determines in step S7 that the capacitance ΔAD6 shown in FIG. 7A is not greater than or equal to the threshold value Th3 (S7: No), it determines that the hand H is not in contact with the rim 110A of the steering wheel 110 (step S8).

[0078] <Threshold Th5> Fig. 7B is a diagram showing threshold value Th5 used in the process of step S12 by contact determination unit 132. In Fig. 7B, the vertical axis represents capacitance ΔAD measured by capacitance measurement unit 120 in the mutual capacitance detection mode.

[0079] The threshold value Th5 is set to a capacitance that can determine whether the hand H is in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present in the mutual capacitance detection mode. The flow proceeds to step S12 when it is determined that the capacitances (ΔAD) calculated in step S2 do not include a capacitance equal to or greater than the threshold value Th2 (S2: No), as opposed to the case where the flow proceeds to step S7.

[0080] The threshold value Th5 is used to detect whether the hand H is simply in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present, and is therefore smaller than the threshold value Th3 used to determine whether the hand H is in contact with the seam 112A of the rim 110A or a dead zone where no sensor is present.

[0081] 7B is equal to or greater than the threshold value Th5 in step S12, the contact determination unit 132 determines that the hand H is in contact with the rim 110A of the steering wheel 110 (step S4). This indicates that the hand H is simply in contact with the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present.

[0082] 7B is not equal to or greater than the threshold value Th5 in step S12, the contact determination unit 132 determines that the hand H is not in contact with the rim 110A of the steering wheel 110 (step S8). This indicates that the hand H is not even in a state of simply contacting the seam 112A of the rim 110A of the steering wheel 110 or a dead zone where no sensor is present, and is therefore not in contact.

[0083] <Effects> The steering wheel unit 100 includes a steering wheel 110 having a rim 110A, spokes 110B, and sensors 113A to 113D arranged inside the rim 110A, a mode switching unit 131 that selects the sensors 113A to 113D as drive electrodes or detection electrodes and enables switching between a self-capacitance detection mode and a mutual capacitance detection mode, a capacitance measuring unit 120 that measures the capacitance detected by the drive electrodes and the detection electrodes, and a contact determination unit 132 that determines whether or not the operator's hand H is in contact with the steering wheel 110 based on the capacitance measured by the capacitance measuring unit 120. In the mutual capacitance detection mode, the mode switching unit 131 selects a driving electrode from the sensors 113A to 113D and selects an electrode adjacent to the selected driving electrode as a detection electrode. When the mode switching unit 131 is set to the self-capacitance detection mode, the contact determination unit 132 determines that the operator's hand H is in contact with at least one of the sensors 113A to 113D on the rim 110A if the capacitance measured by the capacitance measurement unit 120 is equal to or greater than a threshold value Th1. If the capacitance measured by the capacitance measurement unit 120 is equal to or greater than a threshold value Th2 that is smaller than the threshold value Th1 but less than the threshold value Th1, the mode switching unit 131 is switched from the self-capacitance detection mode to the mutual capacitance detection mode, and then determines that the operator's hand H is in contact with a position on the rim 110A that overlaps with a gap between the sensors 113A to 113D if the capacitance measured by the capacitance measurement unit 120 is equal to or greater than a threshold value Th3. Therefore, even if it is determined in the self-capacitance detection mode that the operator's hand H is not in contact with the rim 110A, it is possible to determine whether the hand H is in contact by measuring the capacitance in the mutual capacitance detection mode.

[0084] Therefore, it is possible to provide a steering wheel unit 100 that can determine whether or not the operator's hand H is in contact with the rim 110A of the steering wheel 110 in a dead zone where no sensor is present.

[0085] Furthermore, if the capacitance measured by the capacitance measuring unit 120 in the mutual capacitance detection mode is less than the threshold value Th3, the contact determination unit 132 determines that the operator's hand H is not in contact with the rim 110A. Therefore, it is possible to determine that the operator's hand H is not in contact in the dead zone where no sensor is present.

[0086] Furthermore, if the capacitance measured by the capacitance measuring unit 120 in the self-capacitance detection mode is less than threshold value Th2 and the capacitance measured by the capacitance measuring unit 120 is equal to or greater than threshold value Th4, the contact determination unit 132 causes the mode switching unit 131 to switch from self-capacitance detection mode to mutual capacitance detection mode, and if the capacitance measured by the capacitance measuring unit 120 is equal to or greater than threshold value Th5, determines that the operator's hand H is in contact with the rim 110A at a position that overlaps with the gap between the sensors 113A to 113D. Therefore, even if the capacitance measured by the capacitance measuring unit 120 in the self-capacitance detection mode is so small that it is determined to be less than threshold value Th2, it is possible to determine that the operator's hand H is in contact with the dead zone where no sensor is present.

[0087] If the capacitance measured by the capacitance measuring unit 120 in the mutual capacitance detection mode is less than the threshold value Th5, the contact determination unit 132 determines that the operator's hand H is not in contact with the rim 110A. Therefore, even if the capacitance measured by the capacitance measuring unit 120 in the self-capacitance detection mode is so small that it is determined to be less than the threshold value Th2, it is possible to determine that the operator's hand H is not in contact in the dead zone where no sensor is present.

[0088] Furthermore, threshold value Th5 is smaller than threshold value Th3. Threshold value Th5 is used to detect whether hand H is simply in contact with seam 112A of rim 110A of steering wheel 110 or a dead zone where no sensor is present, and is smaller than threshold value Th3 for determining a state in which hand H is in contact with seam 112A of rim 110A or a dead zone where no sensor is present.

[0089] The threshold value Th4 is a threshold value for comparison with a value (raw value) obtained by subtracting a reference value from the capacitance measured by the capacitance measuring unit 120 in the self-capacitance detection mode. Therefore, by detecting a slight change in the capacitance (raw value) that is digitally converted and output by the capacitance measuring unit 120, it is possible to determine whether the operator's hand H is in contact with a dead zone where no sensor is present.

[0090] Furthermore, when the capacitance measured by the capacitance measuring unit 120 is equal to or greater than the threshold value Th2, the contact determination unit 132 determines whether the capacitance measured by the capacitance measuring unit 120 is equal to or greater than the threshold value Th1. This makes it possible to determine whether the position where the hand H is in contact is a dead zone where no seam 112A or sensor is present.

[0091] The gaps between the sensors 113A to 113D are located at the seams 112A or joints of the skin 112 that covers the rim 110A. Therefore, it is possible to determine whether or not the operator's hand H is in contact with the skin 112 in areas that become dead zones, such as the seams 112A or joints of the skin 112.

[0092] <Modification> Fig. 8 is a diagram showing the configuration of the sensor 113 according to a modified example of the embodiment. Although Fig. 1 to Fig. 3 illustrate an embodiment in which four sensors 113A to 113D are provided on the steering wheel 110, the number of sensors is not limited to four and may be, for example, more.

[0093] 8 shows 21 sensors 113 arranged in seven rows and three columns, with seven sensors 113 arranged horizontally and three sensors vertically, and the initial capacitance values ​​(raw values) of the seven sensors in the second row measured by the capacitance measurement unit 120. These 21 sensors 113 are provided on a sheet-like skin 112 (see FIG. 1). A seam 112A serving as a dead zone is located in a portion corresponding to the eighth column of the sensors 113 arranged in three rows and seven columns. For example, when the sensor 113 is wound around the rim of the steering core 111, the seam 112A is located between the sensors 113 in the first column and the sensors 113 in the seventh column.

[0094] The following describes the process that the HODECU 130 executes when the operator's hand H is in contact with the stitch 112A, which serves as the dead zone and is located at a position corresponding to the second row and eighth column.

[0095] When the contact determination unit 132 starts processing, it causes the mode switching unit 131 to set the self-capacitance detection mode and acquires the capacitance measured in time division order at each of the 21 sensors 113 by the capacitance measurement unit 120 (step S1). In step S1, the contact determination unit 132 acquires a digital conversion value (raw value) that is the capacitance acquired by the capacitance measurement unit 120.

[0096] In step S1, the mode switching unit 131 may drive the 20 sensors other than the sensor that detects capacitance as shields. Such processing can be performed by the contact determination unit 132 instructing the mode switching unit 131. By driving the 20 sensors other than the sensor that detects capacitance as shields, it is possible to suppress the influence of the ground and the like around the sensors that detect capacitance, and it is possible to stably detect capacitance.

[0097] The contact determination unit 132 subtracts a predetermined reference value from the digitally converted value (raw value) to obtain the capacitance as the difference value (ΔAD), and determines whether any of the obtained capacitances is equal to or greater than the threshold value Th2 (step S2). Because the operator's hand H is in contact with the seam 112A, the capacitance is less than the threshold value Th2, and the process proceeds to step S9.

[0098] Here, the initial value (raw value) of the capacitance of each sensor acquired by the capacitance measuring unit 120 will be described.

[0099] The 21 sensors in the first to seventh columns are positioned at different positions from the seam 112A, and the number of sensors 113 located on the left and right in the horizontal direction is different. For example, the sensor in the second row and sixth column is located two sensors to the left and six sensors to the right from the seam 112A, and its initial value (raw value) of capacitance is lower than that of the sensor in the second row and seventh column. This is because the more sensors there are between the seam 112A, the smaller the capacitive coupling with the surrounding ground, such as the steering wheel 110, and the lower the initial value. Therefore, the 21 sensors in the first to seventh columns and the first to third rows have different initial values ​​of capacitance (raw value) measured by the capacitance measurement unit 120. The initial value is the capacitance (raw value) when the hand H is not in contact with the seam 112A.

[0100] In step S9, the contact determination unit 132 uses the threshold value Th4 to determine the sensors 113 in each row and column, and detects that the capacitance (raw value) of the sensors 113 in the first and seventh columns adjacent to the seam 112A exceeds the threshold value Th4, indicating that the hand H may be touching the seam 112A, and proceeds to step S10.

[0101] The processes in steps S10 to S12 are as described above.

[0102] The above describes a steering wheel unit according to an exemplary embodiment of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0103] This international application claims priority based on Japanese Patent Application No. 2022-125647, filed on August 5, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0104] 100 Steering Wheel Unit 110 Steering Wheel 110A rim 110B spokes 111 Steering core 112 Epidermis 112A Seam (Example of gaps and overlapping positions between multiple electrodes) 113, 113A to 113D Sensor (an example of multiple electrodes) 120 Capacity measurement section 130 HODECU 131 Mode switching section 132 Contact determination section 200 ADASECU

Claims

1. a steering wheel having a rim, spokes, and a plurality of electrodes arranged to cover the rim with gaps therebetween; a mode switching unit that switches between a self-capacitance detection mode and a mutual capacitance detection mode for the plurality of electrodes; a capacitance measurement unit that measures the capacitance of the plurality of electrodes; a contact determination unit that determines whether or not an operator's hand is in contact with the steering wheel based on the capacitance measured by the capacitance measurement unit; Equipped with the mode switching unit, in the mutual capacitance detection mode, selects a drive electrode from the plurality of electrodes and selects an electrode adjacent to the selected drive electrode as a detection electrode; When the self-capacitance detection mode is set by the mode switching unit, the contact determination unit If the capacitance measured by the capacitance measurement unit is equal to or greater than a first threshold, it is determined that the operator's hand is in contact with the rim at a position that overlaps with at least one of the plurality of electrodes; a steering wheel unit configured to determine, when the capacitance measured by the capacitance measuring unit is equal to or greater than a second threshold value that is smaller than the first threshold value and is less than the first threshold value, switch from the self-capacitance detection mode to the mutual capacitance detection mode by the mode switching unit, and then, when the capacitance measured by the capacitance measuring unit in the mutual capacitance detection mode is equal to or greater than a third threshold value, determine that the operator's hand is in contact with a position of the rim that overlaps with the gap between the plurality of electrodes.

2. 2. The steering wheel unit according to claim 1, wherein the contact determination unit determines that the operator's hand is not in contact with the rim if the capacitance measured by the capacitance measurement unit in the mutual capacitance detection mode is less than the third threshold value.

3. 2. The steering wheel unit according to claim 1, wherein, when the capacitance measured by the capacitance measuring unit in the self-capacitance detection mode is less than the second threshold and the capacitance measured by the capacitance measuring unit is equal to or greater than a fourth threshold, the contact determination unit determines that the operator's hand is in contact with a position of the rim that overlaps with a gap between the plurality of electrodes after switching from the self-capacitance detection mode to the mutual capacitance detection mode by the mode switching unit if the capacitance measured by the capacitance measuring unit is equal to or greater than a fifth threshold.

4. 4. The steering wheel unit according to claim 3, wherein the contact determination unit determines that the operator's hand is not in contact with the rim if the capacitance measured by the capacitance measurement unit in the mutual capacitance detection mode is less than the fifth threshold value.

5. The steering wheel unit according to claim 3 , wherein the fifth threshold value is smaller than the third threshold value.

6. The steering wheel unit according to claim 3 , wherein the fourth threshold value is a threshold value for comparison with a value obtained by subtracting a reference value from the capacitance measured by the capacitance measuring unit in the self-capacitance detection mode.

7. 7. The steering wheel unit according to claim 1, wherein the contact determination unit determines whether the capacitance measured by the capacitance measurement unit is equal to or greater than the first threshold value when the capacitance measured by the capacitance measurement unit is equal to or greater than the second threshold value.

8. The steering wheel unit according to claim 1 , wherein the gaps between the plurality of electrodes are located at seams or joints of a skin covering the rim.

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