Grip detection device and steering wheel

Abstract

To provide a gripping detection device that can highly accurately detect steering gripping.SOLUTION: A gripping detection device 10 includes: a detection mechanism 40 disposed at least at a gripping portion of a steering wheel 100 and configured to connect an output side piezoelectric element 20 to a receive side piezoelectric element 30 to transmit vibration output from the output side piezoelectric element 20 to the receive side piezoelectric element 30; and a clearance portion (projecting portion 41) taking a clearance between a placement surface of the steering wheel 100 on which the detection mechanism 40 is placed and the detection mechanism 40.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] In recent years, the demand for autonomous driving has increased, and steering wheel grip detection functions are now required by law. Currently, for autonomous driving level 2, the existing steering wheel grip devices are mainly capacitance and torque sensor types. However, for autonomous driving level 3, the occurrence of false detections with these methods becomes an issue.

[0003] To address the issues with capacitance and torque sensor types, grip detection methods using vibration have been proposed. For example, Patent Document 1 discloses a configuration in which a vibrating unit vibrates the core of the steering wheel, and the core is used as a vibration transmission unit between the vibrating unit and a detection unit, and the detection unit detects the state of the steering wheel being gripped from changes in the vibration waveform. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-078980 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a rigid body such as a core is vibrated, as in the method described in Patent Document 1, the vibration amplitude can be detected, but there is no elastic deformation, and the changes in the vibration amplitude and frequency characteristics are extremely small, making detection by gripping relatively difficult. Furthermore, when the core is used as the vibration transmission part, the vibration is further suppressed by wrapping it with a skin, which further reduces the detection ability.

[0006] An object of the present disclosure is to provide a grip detection device that can detect steering grip with high accuracy. [Means for solving the problem]

[0007] A grip detection device according to one aspect of an embodiment of the present invention is a grip detection device for detecting when an occupant of a vehicle is gripping the steering wheel, and comprises a transmitting piezoelectric element, a receiving piezoelectric element, and a transmission unit installed on at least the grip portion of the steering wheel, which transmits vibrations transmitted from the transmitting piezoelectric element to the receiving piezoelectric element. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a grip detection device that can detect steering grip with high accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a configuration of a grip detection device according to a first embodiment; [Figure 2] FIG. 2 is an exploded perspective view of the grip detection device shown in FIG. 1. [Figure 3] Schematic diagram of a cross section of a steering wheel with a grip detection device installed [Figure 4] A perspective view of the back side of the detection mechanism [Figure 5] Schematic diagram illustrating a mechanism for grip detection of the grip detection device of the first embodiment. [Figure 6] Schematic diagram showing the change in vibration amplitude when gripping and when not gripping [Figure 7] Functional block diagram of the grip detection device [Figure 8] Flowchart of grip detection method according to the first embodiment [Figure 9] FIG. 10 is a schematic diagram showing an example of the arrangement of a grip detection device according to a second embodiment on a steering wheel; [Figure 10] FIG. 10 is a schematic diagram showing another example of the arrangement of the grip detection device on the steering wheel according to the second embodiment; [Figure 11] FIG. 10 is a schematic diagram showing a grip detection device according to a modified example of the second embodiment; [Figure 12]FIG. 11 is a schematic diagram showing an example of the arrangement of a grip detection device according to a third embodiment on a steering wheel; [Figure 13] FIG. 10 is a schematic diagram showing another example of the arrangement of the grip detection device on the steering wheel according to the third embodiment; [Figure 14] 10 is a time chart illustrating a grip detection method according to the third embodiment; [Figure 15] FIG. 10 is a schematic diagram showing an example of the arrangement of a grip detection device according to a fourth embodiment on a steering wheel; [Figure 16] Schematic diagram illustrating a mechanism for grip detection of a grip detection device according to a fourth embodiment. [Figure 17] System block diagram of a grip detection device according to a fourth embodiment [Figure 18] FIG. 13 is a schematic diagram showing a grip detection device according to a modified example of the fourth embodiment. [Figure 19] FIG. 1 is a diagram illustrating vibration transmission in a grip detection device. [Figure 20] 10 is a perspective view of the back side of a first modified example of the protrusion of the detection mechanism portion; FIG. [Figure 21] 10 is a perspective view of the back side of a second modified example of the protrusion of the detection mechanism portion; FIG. [Figure 22] 10 is a perspective view of the back side of a third modified example of the protrusion of the detection mechanism portion; [Figure 23] 10 is a perspective view of the back side of a fourth modified example of the protrusion of the detection mechanism portion; [Figure 24] 10 is a perspective view of the back side of the fifth modified example of the protrusion of the detection mechanism portion; [Figure 25] 10 is a perspective view of the back side of a sixth modified example of the protrusion of the detection mechanism portion; [Figure 26] Schematic diagram of a first modified example of the shape of the detection mechanism part [Figure 27] Schematic diagram of a second modified example of the shape of the detection mechanism part [Figure 28] Schematic diagram of a third modified example of the shape of the detection mechanism part [Figure 29] FIG. 10 shows modified examples of the transmission frequency [Figure 30] FIG. 13 is a schematic diagram illustrating a non-grasping state of the grip detection device of the fifth embodiment. [Figure 31] 13 is a schematic diagram showing a grip state of the grip detection device of the fifth embodiment. [Figure 32] Schematic diagram to explain the vibration mechanism when a casing is installed [Figure 33] Schematic diagram to explain the vibration mechanism when there is no casing [Figure 34] A diagram showing the steering wheel core partially covered with urethane [Figure 35] Image showing the urethane removed [Figure 36] Diagram showing an example of bracket installation on the core [Figure 37] Diagram showing the space between the steering wheel core and the bracket [Figure 38] FIG. 10 is a diagram illustrating the arrangement of a transmitting piezoelectric element, a receiving piezoelectric element, and a control unit. [Figure 39] Cross-sectional view of a first structural example of a casing attached to a bracket [Figure 40] FIG. 1 is an exploded perspective view of a first structural example of a casing attached to a bracket; [Figure 41] Cross-sectional view of a second structural example of a casing attached to the detection mechanism unit [Figure 42] FIG. 10 is an exploded perspective view of a second structural example of a casing attached to the detection mechanism; [Figure 43] Cross-sectional view showing a third example of the casing structure [Figure 44] Cross-sectional view showing a fourth structural example of the casing [Figure 45] 1 is a cross-sectional view showing a first structural example of a spacer; [Figure 46] 10 is a cross-sectional view showing a second structural example of the spacer; [Figure 47] Cross-sectional view showing a first structural example of the bracket [Figure 48] Cross-sectional view showing a second structural example of the bracket [Figure 49] Cross-sectional view showing a third structural example of the bracket [Figure 50] Cross-sectional view showing a fourth structural example of the bracket [Figure 51] Cross-sectional view showing a fifth structural example of the bracket [Figure 52]Cross-sectional view showing a sixth structural example of the bracket [Figure 53] Cross-sectional view showing a seventh structural example of the bracket [Figure 54] Cross-sectional view showing an eighth structural example of the bracket [Figure 55] Cross-sectional view showing a ninth structural example of the bracket [Figure 56] Cross-sectional view showing the tenth structural example of the bracket DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0011] [First embodiment] A first embodiment will be described with reference to Figs. 1 to 8. Fig. 1 is a perspective view showing the configuration of a grip detection device 10 according to the first embodiment. Fig. 2 is an exploded perspective view of the grip detection device 10 shown in Fig. 1. Fig. 3 is a schematic cross-sectional view of a steering wheel 100 on which the grip detection device 10 is installed. Fig. 4 is a perspective view of the back side of the detection mechanism unit 40.

[0012] The grip detection device 10 according to the first embodiment is a device for detecting that a vehicle occupant is gripping a steering wheel 100, and is provided on the steering wheel 100.

[0013] The steering wheel 100 is a part of a steering device operated by a driver to steer a vehicle, and is an annular member that is gripped by the driver. Although the steering wheel 100 is annular in the examples of FIGS. 1 and 2, it may have a shape other than a circle, such as an ellipse. In the following description, the direction along the annular shape of the steering wheel 100 will be referred to as the "annular direction."

[0014] As shown in FIG. 3, in a cross section perpendicular to the annular direction of the steering wheel 100, a core 101 is disposed at the center of the steering wheel 100. The core 101 is formed, for example, of a metal core bar. The outside of the core 101 is surrounded by a base 102. The base 102 is formed of a material softer than the core bar, for example, an elastic resin such as urethane. The base 102 may be formed of a material other than a resin material, such as a nonwoven fabric or a film. The outside of the base 102 is further surrounded by a cover 103. The cover 103 is the part that comes into direct contact with the occupant, and is formed, for example, of leather, artificial leather, resin, wood, or the like.

[0015] In this way, steering wheel 100 has a structure in which core portion 101, base portion 102, and cover portion 103 are layered from the center in a cross-sectional view. Note that although the cross-sectional shape of steering wheel 100 in the example of FIG. 3 is substantially circular, it may have other shapes such as an ellipse. In the following description, the direction connecting the center side and the outer periphery side of the cross-sectional shape of steering wheel 100 will be referred to as the "radial direction," and the direction along the outer periphery of the circular cross section will be referred to as the "circumferential direction."

[0016] 1 and 2 show a state in which a part of the cover portion 103 shown in FIG. 3 is removed from the finished product, exposing the base portion 102. That is, in this embodiment, the grip detection device 10 is installed in a groove 104 formed in the base portion 102, and is used in a state in which it is covered by the cover portion 103. The grip detection device 10 is installed along the annular direction of the steering wheel 100 so that its detection range includes at least the position where the occupant grips the steering wheel.

[0017] The grip detection device 10 includes a transmitting piezoelectric element 20, a receiving piezoelectric element 30, and a detection mechanism unit 40.

[0018] The detection mechanism 40 is an example of a transmission unit that transmits the vibrations transmitted from the transmitting piezoelectric element 20 to the receiving piezoelectric element 30. The detection mechanism 40 connects the transmitting piezoelectric element 20 and the receiving piezoelectric element 30, and transmits the vibrations transmitted from the transmitting piezoelectric element 20 to the receiving piezoelectric element 30. The detection mechanism 40 is installed in at least the grip portion of the steering wheel 100. The detection mechanism 40 is a long, thin plate member, and is formed from an elastically deformable material such as resin or metal.

[0019] The width of the detection mechanism 40 in the short side direction (circumferential direction) is preferably, for example, about 5 to 10 mm. The thickness (diameter dimension) of the thin plate shape of the detection mechanism 40 is preferably about 0.05 to 2 mm.

[0020] 1 and 2, a groove 104 is formed in the outer peripheral surface of the base 102 in the annular direction at the installation portion of the detection mechanism unit 40, the groove 104 being dug radially inward from the outer peripheral surface, and the grip detection device 10 is installed by being fitted into this groove 104. More specifically, the position of the groove 104 is preferably located at the outermost position of the annular shape of the steering wheel 100 in the circumferential direction of the base 102. This makes it easier for the detection mechanism unit 40 of the grip detection device 10 to face the palm or fingers of the occupant when the occupant grips the steering wheel 100, thereby improving the accuracy of grip detection.

[0021] 4, a convex portion 41 is provided on the back surface of the detection mechanism unit 40. The convex portion 41 is an example of a spacer that ensures a space for vibration of a transmission unit (in this example, the detection mechanism unit 40) that transmits the vibrations transmitted from the transmission-side piezoelectric element 20 to the reception-side piezoelectric element 30. As shown in FIG. 3, the convex portion 41 faces the bottom surface of the groove 104 when the grip detection device 10 is installed, and a clearance can be provided between the plate-like portion of the detection mechanism unit 40 and the bottom surface of the groove 104. In other words, the convex portion 41 functions as a "clearance portion that provides a clearance between the detection mechanism unit 40 and the installation surface on the steering wheel 100 on which the detection mechanism unit 40 is installed." Furthermore, the bottom surface of the groove 104 functions as an "installation surface on the steering wheel 100 on which the detection mechanism unit 40 is installed."

[0022] 4, a plurality of protrusions 41 are arranged at approximately equal intervals along the longitudinal direction, i.e., the annular direction, of the detection mechanism unit 40. In the example of Fig. 4, the shape of the protrusions 41 extends over the entire short side (circumferential direction) of the detection mechanism unit 40 when viewed in the radial direction, and is formed in an approximately Z-shape, extending from one of its ends in one direction in the longitudinal direction (annular direction) and from the other of its ends in the other direction in the longitudinal direction.

[0023] The intervals between the plurality of protrusions 41 arranged on the detection mechanism 40 are preferably, for example, about 30 to 50 mm.

[0024] Materials for the detection mechanism 40 and the protrusion 41 include, for example, polycarbonate (PC), polyacetal (POM), polyethylene terephthalate (PET), stainless steel (SUS), aluminum, aluminum alloy, zinc, tin, copper, and rubber. In the case of rubber, a relatively hard material such as a timing belt is preferable. Inorganic materials such as silicon may also be used.

[0025] 1, the grip detection device 10 has a transmitting piezoelectric element 20 and a receiving piezoelectric element 30 stacked on either end of a detection mechanism unit 40 and connected and fixed using an adhesive or the like. The detection mechanism unit 40 is then placed on the installation surface of the steering wheel 100, and both ends of the detection mechanism unit 40 are fixed to the installation surface by any method such as screw fastening. The transmitting piezoelectric element 20 and the receiving piezoelectric element 30 may be attached to either the front or back surface of the detection mechanism unit 40.

[0026] 5 is a schematic diagram illustrating the mechanism of grip detection of the grip detection device 10 of the first embodiment. FIG. 5(A) shows a non-gripping state, and FIG. 5(B) shows a gripping state. In the non-gripping state as shown in FIG. 5(A), the vibrations transmitted from the transmitting piezoelectric element 20 are transmitted to the receiving piezoelectric element 30 while maintaining their amplitude in the detection mechanism unit 40, and are measured by the receiving piezoelectric element 30.

[0027] On the other hand, in the case of gripping, as shown in Fig. 5(B), pressure due to the gripping force is applied to the detection mechanism unit 40 from the radially outer side. This pressure causes the plate-like portion of the detection mechanism unit 40 to elastically deform, thereby attenuating the vibrations transmitted to the detection mechanism unit 40. The attenuated vibrations are transmitted to the receiving piezoelectric element 30 and measured by the receiving piezoelectric element 30. Furthermore, the protrusion 41 provided on the back surface of the detection mechanism unit 40 allows a large clearance to be secured between the plate-like portion of the detection mechanism unit 40 and the bottom surface of the groove 104, thereby increasing the amount of elastic deformation of the detection mechanism unit 40 due to pressure and increasing the degree of attenuation.

[0028] Fig. 6 is a schematic diagram showing the change in vibration amplitude when gripped and when not gripped. As shown in Fig. 6, the detection mechanism unit 40, which is vibrating at a constant frequency due to the transmission-side piezoelectric element 20, changes its vibration waveform when gripped by a vehicle occupant. As described above, when gripped, the detection mechanism unit 40 elastically deforms, thereby attenuating the vibration, so the vibration amplitude when gripped is smaller than when not gripped.

[0029] Fig. 7 is a functional block diagram of the grip detection device 10. As shown in Fig. 7, the grip detection device 10 includes a control unit 50 in addition to the above-mentioned transmitting piezoelectric element 20, receiving piezoelectric element 30, and detection mechanism unit 40.

[0030] The control unit 50 controls the grip detection process performed by the grip detection device 10. The control unit 50 includes a drive unit 51, a signal processing unit 52, an AD conversion unit 53, and an arithmetic processing unit .

[0031] The driving section 51 outputs a driving signal that vibrates the transmitting piezoelectric element 20 so that the vibration propagates to the detection mechanism section 40 (or the urethane 45 described below). The driving signal is, for example, an AC voltage with a constant period.

[0032] The signal processing unit 52 removes noise (for example, noise caused by the engine or running of the vehicle) contained in the analog output signal output from the receiving piezoelectric element 30 by filtering or the like.

[0033] The AD conversion unit 53 converts the analog output signal that has been subjected to signal processing such as filtering by the signal processing unit 52 into a digital signal.

[0034] The arithmetic processing unit 54 detects the state of the occupant's grip on the steering wheel 100 based on the digital signal supplied from the AD conversion unit 53, and outputs the detection result to an external device.

[0035] Each function of the control unit 50 can be realized by hardware such as a circuit configured with an analog circuit, a digital circuit, or an analog-digital mixed circuit. In this case, the control unit 50 is preferably installed inside a hub located at the center of the inside of the steering wheel 100, but may be installed in another location in the vehicle. Also, part or all of the control unit 50 may be configured as a computer system including a CPU, RAM, ROM, etc. In this case, the functions of the control unit 50 may be realized by, for example, an ECU (Electronic Control Unit) installed in the vehicle.

[0036] 8 is a flowchart of the grip detection method according to the first embodiment. Each process in the flowchart shown in FIG.

[0037] 8, a drive signal of a certain amplitude and frequency is supplied by the drive unit 51 to the transmitter piezoelectric element 20. As a result, the transmitter piezoelectric element 20 generates vibrations of a certain amplitude and frequency according to the drive signal, which are transmitted to the detection mechanism unit 40 (or urethane 45, described later).

[0038] In step S1, the output signal of the receiving piezoelectric element 30 is confirmed. Specifically, the output signal is processed by the signal processing unit 52 and the AD conversion unit 53, and the processed output signal is input to the calculation processing unit 54.

[0039] In step S2, the arithmetic processing unit 54 determines whether the amplitude V of the output signal from the receiving piezoelectric element 30 is within a predetermined normal range of V1 to V2.

[0040] If it is determined that the amplitude V is outside the predetermined normal range, the calculation processing unit 54 performs an abnormality diagnosis process to output an abnormality signal to notify the outside of an abnormality in the receiving side piezoelectric element 30 or the transmitting side piezoelectric element 20 (step S3).

[0041] On the other hand, when the calculation processing unit 54 determines that the amplitude V is within the predetermined normal range, it determines whether the change in the output signal is within a range that can be determined as an unheld state or a range that can be determined as a held state. When the calculation processing unit 54 determines that the steering wheel 100 is not held (unheld state), it executes the processing of step S1 again. When the calculation processing unit 54 determines that the steering wheel 100 is held (held state), it executes the processing of step S4.

[0042] In step S4, the calculation processing unit 54 determines whether the change in the output signal remains within a range (a gripped state range) that can be determined as a gripped state for a predetermined time (e.g., one second) or more. If the calculation processing unit 54 detects that the change in the output signal has fallen out of the gripped state range before continuing for a predetermined time or more, it executes the processing of step S1 again. On the other hand, if the calculation processing unit 54 detects that the change in the output signal remains within the gripped state range for a predetermined time or more, it determines that the steering wheel 100 is being gripped by the occupant (step S5).

[0043] The effects of the grip detection device 10 according to the first embodiment will be described.

[0044] Conventional grip detection methods, such as those described in Patent Document 1, involve vibrating a steering wheel core using a vibrator, using the core as a vibration transmission unit between the vibrator and a detection unit, and detecting the steering wheel's grip state from changes in the vibration waveform detected by the detection unit. However, when a rigid body such as a core is vibrated as in the method described in Patent Document 1, the vibration amplitude can be detected, but there is no elastic deformation, and changes in the vibration amplitude and frequency characteristics are extremely small, making grip detection relatively difficult. Furthermore, when the core is used as the vibration transmission unit, wrapping the surface further suppresses vibration, further reducing detection capabilities. Therefore, to detect grip using conventional technology, the piezoelectric element in the drive unit must be driven at a high voltage, which increases power consumption and shortens the element's lifespan. Furthermore, the high drive voltage generates vibration noise that is unpleasant to users, making this technology unsuitable for practical use.

[0045] In contrast, the grip detection device 10 of the first embodiment is equipped with a detection mechanism unit 40 that is installed in at least the grip portion of the steering wheel 100, which connects the transmitting piezoelectric element 20 and the receiving piezoelectric element 30 and transmits the vibrations emitted from the transmitting piezoelectric element 20 to the receiving piezoelectric element 30, and a clearance portion (convex portion 41) that provides clearance between the installation surface on the steering wheel 100 on which the detection mechanism unit 40 is installed and the detection mechanism unit 40.

[0046] This configuration allows the detection mechanism unit 40 to be positioned with a predetermined clearance on an installation surface, such as the surface of the base 102 of the steering wheel 100. Therefore, when vibrations are transmitted from the transmitting piezoelectric element 20, sufficient space is ensured for the detection mechanism unit 40 to vibrate radially in response to the vibrations. The signal transmitted from the transmitting piezoelectric element 20 can be reliably transmitted to the receiving piezoelectric element 30 via the detection mechanism unit 40. This makes it possible to detect the damping of vibrations in the grip state more clearly, enabling highly accurate detection of the steering wheel grip. Furthermore, because the pressure generated by gripping can be detected even in an environment where external pressure is constantly applied by the surface, the transmitting piezoelectric element 20 can be driven at a lower voltage than conventional devices, thereby improving on the problems of conventional technologies, such as low power consumption, reduced element lifespan, and user discomfort due to vibration noise.

[0047] In the grip detection device 10 of the first embodiment, the detection mechanism 40 is preferably a resin plate. This allows the detection mechanism 40 to easily deform elastically, allowing vibrations to be transmitted efficiently. Also, the grip detection device 10 can be made lighter.

[0048] Furthermore, in the grip detection device 10 of the first embodiment, the clearance portion is preferably a protrusion 41 that protrudes from the back surface of the detection mechanism portion 40. This allows the clearance portion to be formed integrally with the detection mechanism portion 40, thereby reducing the number of parts and improving manufacturing efficiency.

[0049] Furthermore, in the grip detection device 10 of the first embodiment, a groove 104 for fitting the detection mechanism unit 40 is provided in the installation portion of the steering wheel 100 where the detection mechanism unit 40 is installed, and the installation surface on the steering wheel 100 where the detection mechanism unit 40 is installed is preferably the bottom surface of this groove 104. This configuration makes it easy to determine the installation position of the detection mechanism unit 40 and prevents it from shifting position after installation. Furthermore, the depth of the groove 104 can prevent the detection mechanism unit 40 from protruding radially outward from the surface of the base 102 (or core 101) where the groove 104 is provided. Therefore, pressure applied to the detection mechanism unit 40 by wrapping a cover unit 103 or the like outside the installation position can be reduced, and vibration transmission can be more reliably achieved.

[0050] [Second embodiment] The second embodiment will be described with reference to Figures 9 to 11. In the second embodiment, the description of the same configurations and effects as those of the first embodiment will be omitted by citing the above description. In the embodiments described later, the description of the same configurations and effects as those of other embodiments will be omitted by citing the description of those other embodiments.

[0051] Fig. 9 is a schematic diagram showing an example of the arrangement of a grip detection device 10A according to the second embodiment on a steering wheel 100. In the first embodiment, a single system of grip detection is used, using one transmitting piezoelectric element 20 and one receiving piezoelectric element 30, whereas the grip detection device 10A of the second embodiment differs from the first embodiment in that it has two systems, one for left-hand grip detection and one for right-hand grip detection, using one transmitting piezoelectric element 20 and two receiving piezoelectric elements 30A and 30B, as shown in Fig. 9.

[0052] 9, the grip detection device 10A includes a transmitter piezoelectric element 20, a first receiver piezoelectric element 30A, a second receiver piezoelectric element 30B, a first detection mechanism unit 40A, and a second detection mechanism unit 40B. The first detection mechanism unit 40A connects the transmitter piezoelectric element 20 and the first receiver piezoelectric element 30A and transmits vibrations transmitted from the transmitter piezoelectric element 20 to the first receiver piezoelectric element 30A. The second detection mechanism unit 40B connects the transmitter piezoelectric element 20 and the second receiver piezoelectric element 30B and transmits vibrations transmitted from the transmitter piezoelectric element 20 to the second receiver piezoelectric element 30B.

[0053] As shown in Fig. 9, the transmitting piezoelectric element 20 is located at 12 o'clock when the steering wheel 100 is viewed from the seat side (i.e., directly above the center of the circular ring shape of the steering wheel 100). The first receiving piezoelectric element 30A is located at 7 o'clock when the steering wheel 100 is viewed from the seat side (i.e., diagonally downward and to the left from the center of the circular ring shape of the steering wheel 100). The second receiving piezoelectric element 30B is located at 5 o'clock when the steering wheel 100 is viewed from the seat side (i.e., diagonally downward and to the right from the center of the circular ring shape of the steering wheel 100).

[0054] In the grip detection device 10A of the second embodiment, by arranging two receiving piezoelectric elements 30A, 30B, one on each side of the steering wheel 100, it is possible to separately detect gripping of the left and right portions of the steering wheel 100. For example, as shown in Fig. 9, when the occupant grips the left side, vibrations are attenuated only by the first detection mechanism unit 40A that connects the transmitting piezoelectric element 20 and the first receiving piezoelectric element 30A, so it is possible to detect that the occupant is gripping the left side of the steering wheel 100 based on the output signal of the first receiving piezoelectric element 30A.

[0055] In the second embodiment, too, two systems of grip detection can be performed on the left and right sides of the steering wheel 100 using the output signal of the first receiving piezoelectric element 30A and the output signal of the second receiving piezoelectric element 30B, using a grip detection method similar to that of the first embodiment shown in Figure 8.

[0056] 10 is a schematic diagram showing another example of the arrangement of the grip detection device 10A according to the second embodiment on the steering wheel 100. The grip detection device 10A according to the second embodiment only needs to be able to perform two-system grip detection for the left and right portions of the steering wheel 100, and the arrangement of the piezoelectric elements 20, 30A, and 30B is not limited to that shown in FIG. 9. For example, as shown in FIG. 10, by arranging the transmitting piezoelectric element 20 in the 6 o'clock direction of the steering wheel 100 (i.e., directly downward from the center position of the circular ring shape of the steering wheel 100), arranging the first receiving piezoelectric element 30A in the 11 o'clock direction (diagonally upward to the left), and arranging the second receiving piezoelectric element 30B in the 1 o'clock direction (diagonally upward to the right), it is possible to detect grips on the left and right separately.

[0057] FIG. 11 is a schematic diagram showing a grip detection device 10B according to a modified example of the second embodiment. In the example of FIG. 11, the transmitter piezoelectric element 20 is arranged at the 7 o'clock direction (diagonally downward to the left) of the steering wheel 100, the first receiver piezoelectric element 30A is arranged at the 12 o'clock direction (directly upward), and the second receiver piezoelectric element 30B is arranged at the 5 o'clock direction (diagonally downward to the right). In the grip detection device 10B, when the left side of the steering wheel 100 is gripped, as shown in FIG. 11, both the first receiver piezoelectric element 30A and the second receiver piezoelectric element 30B detect an attenuated waveform, thereby detecting that the left side has been gripped. On the other hand, when the right side of the steering wheel 100 is gripped, only the second receiver piezoelectric element 30B detects an attenuated waveform, thereby detecting that the right side has been gripped.

[0058] [Third embodiment] The third embodiment will be described with reference to FIGS.

[0059] Fig. 12 is a schematic diagram showing an example of the arrangement of a grip detection device 10C according to the third embodiment on a steering wheel 100. As shown in Fig. 12, the grip detection device 10C of the third embodiment differs from the second embodiment in that it has two systems for left-hand grip detection and right-hand grip detection, using two transmitting piezoelectric elements 20A and 20B and one receiving piezoelectric element 30.

[0060] 12, the grip detection device 10C includes a first transmitter piezoelectric element 20A, a second transmitter piezoelectric element 20B, a receiver piezoelectric element 30, a first detection mechanism unit 40A, and a second detection mechanism unit 40B. The first detection mechanism unit 40A connects the first transmitter piezoelectric element 20A and the receiver piezoelectric element 30, and transmits vibrations transmitted from the first transmitter piezoelectric element 20A to the receiver piezoelectric element 30. The second detection mechanism unit 40B connects the second transmitter piezoelectric element 20B and the receiver piezoelectric element 30, and transmits vibrations transmitted from the second transmitter piezoelectric element 20B to the receiver piezoelectric element 30.

[0061] 12, the receiving piezoelectric element 30 is disposed at a position in the 12 o'clock direction (directly above) when the steering wheel 100 is viewed from the seat side. The first transmitting piezoelectric element 20A is disposed at a position in the 7 o'clock direction (diagonally downward left) of the steering wheel 100. The second transmitting piezoelectric element 20B is disposed at a position in the 5 o'clock direction (diagonally downward right) of the steering wheel 100.

[0062] That is, the arrangement of the piezoelectric elements in the grip detection device 10C shown in Fig. 12 is an arrangement in which the transmitting side and receiving side are swapped with respect to the grip detection device 10B of the second embodiment shown in Fig. 9. In the grip detection device 10C of the third embodiment, by arranging two transmitting side piezoelectric elements 20A, 20B, one on each side of the steering wheel 100, it is possible to separately detect gripping of the left and right parts of the steering wheel 100, as in the second embodiment.

[0063] 13 is a schematic diagram showing another example of the arrangement of the grip detection device 10C according to the third embodiment on the steering wheel 100. The arrangement of the piezoelectric elements of the grip detection device 10C shown in FIG. 13 is the same as that of the grip detection device 10B according to the second embodiment shown in FIG. 10, with the transmitting side and receiving side interchanged.

[0064] Fig. 14 is a time chart for explaining the grip detection method in the third embodiment. Fig. 14(A) shows the waveforms of the drive signals of the first transmitter piezoelectric element 20A and the second transmitter piezoelectric element 20B. In the figure, "second transmitter piezoelectric element (5 o'clock (right))" indicates the drive signal of the second transmitter piezoelectric element 20B, and "first transmitter piezoelectric element (7 o'clock (left))" indicates the drive signal of the first transmitter piezoelectric element 20A. In other words, the time chart in Fig. 14 corresponds to the arrangement of the piezoelectric elements in the grip detection device 10C shown in Fig. 12.

[0065] 14(A), the drive signals of the first transmitting piezoelectric element 20A and the second transmitting piezoelectric element 20B are controlled so that when one is on (generating vibration) the other is off (no vibration), and the vibration timing is switched at regular intervals. By comparing the vibration timing with the waveform detected by the receiving piezoelectric element 30, it is possible to detect whether the steering wheel 100 is being held on the left or right side separately.

[0066] Figure 14(B) shows the output signal of the receiving piezoelectric element 30 when not gripped. The "received waveform of the receiving piezoelectric element" in the figure refers to the output signal of the receiving piezoelectric element 30. Here, the waveform when not gripped shown in Figure 6 is shown as "large amplitude" and the waveform when gripped is shown as "small amplitude" for simplification. When not gripped, the receiving piezoelectric element 30 always detects the vibration amplitude of both the first transmitting piezoelectric element 20A and the second transmitting piezoelectric element 20B, so the amplitude is always large. Conversely, when both are gripped, the received waveform is always small amplitude.

[0067] FIG. 14(C) shows the output signal of the receiving piezoelectric element 30 when the driver is gripping the left side. In the example of FIG. 14(C), the left side of the steering wheel 100 is gripped from time t1, when the second transmitting piezoelectric element 20B is turned on, to time t2, when the first transmitting piezoelectric element 20A is turned on after the vibration has been switched on and off three times. As shown in FIG. 14(C), in the case of left-handed gripping, the vibration of the first transmitting piezoelectric element 20A on the left side is turned off, i.e., the amplitude of the first transmitting piezoelectric element 20A is attenuated, so the receiving piezoelectric element 30 receives only the vibration waveform of the second transmitting piezoelectric element 20B on the right side. In the example of FIG. 14(C), when the output signal of the receiving piezoelectric element 30 is detected to switch from large amplitude to small amplitude at time t3, which is the first switching timing after time t1, the waveform matches that of the second transmitting piezoelectric element 20B, and therefore it can be determined that the driver is gripping the left side.

[0068] Also, in Figure 14 (C), after the transition to the non-grasping state at time t2, at time t4 when the second transmitting piezoelectric element 20B switches from on to off, the output signal of the receiving piezoelectric element 30 remains at a large amplitude and does not match the waveform of the second transmitting piezoelectric element 20B, so it can be determined that the state is not being grasped.

[0069] FIG. 14(D) shows the output signal of the receiving piezoelectric element 30 when the driver is gripping the right side. In the example of FIG. 14(D), as in (C), the right side of the steering wheel 100 is gripped from time t1, when the second transmitting piezoelectric element 20B is turned on, to time t2, when the first transmitting piezoelectric element 20A is turned on after the vibration has been switched on and off three times. As shown in FIG. 14(D), in the case of right-handed gripping, the vibration of the second transmitting piezoelectric element 20B on the right side is turned off. In other words, the amplitude of the second transmitting piezoelectric element 20B is attenuated, so the receiving piezoelectric element 30 receives only the vibration waveform of the first transmitting piezoelectric element 20A on the left side. In the example of FIG. 14(D), when the output signal of the receiving piezoelectric element 30 is detected to switch from large amplitude to small amplitude at time t1, when left-handed gripping begins, it matches the waveform of the first transmitting piezoelectric element 20A, so it can be determined that the driver is gripping the right side.

[0070] Also, in Figure 14 (D), at time t2 when the transition to the non-grasping state occurs, the output signal of the receiving piezoelectric element 30 remains large in amplitude and does not match the waveform of the first transmitting piezoelectric element 20A, so it can be determined that the state is not being grasped.

[0071] Even in the case of the arrangement of the piezoelectric elements of the grip detection device 10C shown in FIG. 13, gripping of the left and right sides of the steering wheel 100 can be detected separately by the same method as in FIG.

[0072] [Fourth embodiment] The fourth embodiment will be described with reference to FIGS.

[0073] FIG. 15 is a schematic diagram showing an example of the arrangement of a grip detection device 10D according to a fourth embodiment on a steering wheel 100. The fourth embodiment differs from the first to third embodiments in that a single piezoelectric element 21 for both transmission and reception is used. In the grip detection device 10D, as shown in FIG. 15, for example, the dual-purpose piezoelectric element 21 for transmission and reception (hereinafter simply referred to as the "piezoelectric element 21") is arranged diagonally below the left of the steering wheel 100, and one end of the detection mechanism unit 40 is connected to the dual-purpose piezoelectric element 21 for transmission and reception, extends to pass above the steering wheel 100, and the other end is arranged diagonally below the right of the steering wheel 100. Note that the dual-purpose piezoelectric element 21 for transmission and reception may be arranged diagonally below the right of the steering wheel 100, in a configuration that is reversed from the example of FIG. 15.

[0074] FIG. 16 is a schematic diagram illustrating the mechanism of grip detection of the grip detection device 10D according to the fourth embodiment. The piezoelectric element 21, which can be used for both transmission and reception, is used by switching between its transmission function and reception function at a predetermined timing. First, the piezoelectric element 21 is driven for transmission. The vibrations propagated through the detection mechanism unit 40 are reflected after reaching the end (other end) of the detection mechanism unit 40. The reflected vibrations propagate again through the detection mechanism unit 40 in the opposite direction (toward the piezoelectric element 21) and return to the piezoelectric element 21. After transmitting, the piezoelectric element 21 is switched to reception and receives the reflected vibrations. By detecting a change in the waveform of the reflected vibration due to gripping (for example, a waveform in which the vibration is attenuated), gripping can be detected with a single piezoelectric element 21.

[0075] Fig. 17 is a system block diagram of a grip detection device 10D according to the fourth embodiment. As shown in Fig. 17, the grip detection device 10D includes a control unit 50D in addition to the above-described dual-purpose piezoelectric element 21 and detection mechanism unit 40. The control unit 50D includes a drive circuit 55, a switching circuit 56, a receiving circuit 57, and a signal processing circuit 58.

[0076] The switching circuit 56 periodically switches the piezoelectric element 21 between the transmitting side and the receiving side. When the piezoelectric element 21 is used as the transmitting side, the switching circuit 56 connects the driving circuit 55 to the piezoelectric element 21. On the other hand, when the piezoelectric element 21 is used as the receiving side, the switching circuit 56 connects the receiving circuit 57 to the piezoelectric element 21.

[0077] The driving circuit 55 has the same function as the driving unit 51 shown in FIG. 7, and the receiving circuit 57 and the signal processing circuit 58 have the same function as the signal processing unit 52, the AD conversion unit 53, and the calculation processing unit 54 shown in FIG. 7, so their explanations are omitted.

[0078] Fig. 18 is a schematic diagram showing a grip detection device 10E according to a modification of the fourth embodiment. As shown in Fig. 18, both ends of the detection mechanism section 40 may be connected to a piezoelectric element 21 for both transmission and reception.

[0079] 18, for example, in the grip detection device 10E, the dual-purpose transmitting and receiving piezoelectric element 21 is disposed at a position in the 12 o'clock direction (directly above) of the steering wheel 100, and the detection mechanism unit 40 has one end connected to the dual-purpose transmitting and receiving piezoelectric element 21, extends around the entire circumference passing under the steering wheel 100, and the other end is also connected to the dual-purpose transmitting and receiving piezoelectric element 21. The dual-purpose transmitting and receiving piezoelectric element 21 may be installed at any position on the steering wheel 100 other than the 12 o'clock direction.

[0080] In the grip detection device 10E shown in Figure 18, as in the grip detection device 10D shown in Figure 15, etc., by switching between the transmission function and the reception function of the dual-purpose piezoelectric element 21 at a predetermined timing, it is possible to detect the grip of the steering wheel 100 using a single piezoelectric element 21.

[0081] Fig. 19 is a diagram illustrating vibration transmission in the grip detection device 10E. Fig. 19(A) illustrates vibration transmission when the piezoelectric element 21 is on the transmitting side during left-hand gripping. As shown in Fig. 19(A), vibrations W1 and W2 transmitted from the piezoelectric element 21 are initially transmitted equally to the left and right, but vibration W1 is attenuated in the gripping portion on the left side of the steering wheel 100.

[0082] 19(B) illustrates vibration transmission when the piezoelectric element 21 switches to the receiving side after (A). As shown in FIG. 19(B), the vibration W1 attenuated in (A) is received by the piezoelectric element 21 in an attenuated state after being transmitted along the right side of the steering wheel 100. Meanwhile, the vibration W2 is also attenuated as it propagates from the right side to the left side of the steering wheel 100 and passes through the grip portion, and is then received by the piezoelectric element 21.

[0083] Here, in an area X below the gripping portion of the steering wheel 100 shown in Figure 19(A), vibrations W1 and W2 propagating from the left and right collide. Figure 19(C) shows the transition of the waveform when the two vibrations W1 and W2 intersect. As shown in Figure 19(C), the vibration waveforms W1 and W2 propagating in opposite directions are independent, so after being combined, they can be transmitted to the opposite side with the same amplitude as before being combined.

[0084] 19(B), both amplitude waveforms W1 and W2 are similarly attenuated at the gripping portion and returned to piezoelectric element 21. Therefore, grip detection device 10E can also detect gripping of steering wheel 100 based on the output signal received by piezoelectric element 21.

[0085] [Modification of the protrusion of the detection mechanism] 20 to 25, modified examples of the convex portion of the detection mechanism portion 40 will be described. In the example of Fig. 4, the convex portion 41 is formed in a substantially Z-shape, but the convex portion may have other shapes.

[0086] Fig. 20 is a perspective view of the back side of a first modified example 41A of the protrusion of the detection mechanism part. As shown in Fig. 20, the protrusion part 41A may be formed in a substantially T-shape that extends over the entire short-side direction (circumferential direction) of the detection mechanism part 40 when viewed in the radial direction, and extends from one end to the opposite side in the longitudinal direction (annular direction).

[0087] Fig. 21 is a perspective view of the back side of a second modified example 41B of the protrusion of the detection mechanism part. As shown in Fig. 21, the protrusion part 41B may be formed in a substantially H-shape that extends over the entire short side (circumferential direction) of the detection mechanism part 40 when viewed in the radial direction, and extends from both ends to both sides in the longitudinal direction (annular direction).

[0088] Fig. 22 is a perspective view of the back side of a third modified example 41C of the protrusion of the detection mechanism part. As shown in Fig. 22, the protrusion part 41C may be formed in a substantially I-shape extending over the entire short side direction (circumferential direction) of the detection mechanism part 40 when viewed in the radial direction.

[0089] FIG. 23 is a perspective view of the back side of a fourth modified example 41D of the protrusion of the detection mechanism unit. Like the protrusion 41D shown in FIG. 23, the generally Z-shaped protrusions shown in FIG. 4 may be formed intermittently at predetermined intervals when viewed in the radial direction. In the protrusion 41D, a plurality of generally square-shaped dots 42 (two in the example of FIG. 23) are arranged at predetermined intervals along the lateral direction (circumferential direction) of the detection mechanism unit 40, with one dot arranged at a predetermined interval from one of the ends of the lateral direction of the detection mechanism unit 40 in one longitudinal direction (annular direction), and one dot arranged at a predetermined interval from the other end in the other longitudinal direction. The arrangement of the dots 42 may be a generally T-shape as shown in FIG. 20, a generally H-shape as shown in FIG. 21, or a generally I-shape as shown in FIG. 22.

[0090] Fig. 24 is a perspective view of the back side of a fifth modified example 41E of the protrusion of the detection mechanism. As in the protrusion 41E shown in Fig. 24, instead of the angular dots 42 shown in Fig. 23, a configuration in which a plurality of semicircular dots 43 formed in a semicircular shape when viewed in the circumferential direction may be arranged. Note that the protrusion 41E may also be configured to arrange a plurality of semicircular dots 43 formed in a semicircular shape when viewed in the annular direction.

[0091] Fig. 25 is a perspective view of the back side of a sixth modified example 41F of the protrusion of the detection mechanism. As shown in Fig. 25, protrusion 41F may be configured to have a plurality of hemispherical dots 44 formed in a hemispherical shape when viewed in the annular direction, instead of the angular dots 42 shown in Fig. 23.

[0092] The gaps between the angular dots 42, semicircular dots 43, and hemispherical dots 44 illustrated in FIGS. 23 to 25 are preferably about 7 mm, for example.

[0093] [Modification of the shape of the detection mechanism] Modified examples of the shape of the detection mechanism will be described with reference to Figures 26 to 28. In Figure 1 and other figures, a long thin plate member is shown as an example, extending along the annular direction of the steering wheel 100, but the detection mechanism may have other shapes.

[0094] Figure 26 is a schematic diagram of a first modified example 40-1 of the shape of the detection mechanism unit. Figure 26(A) is a diagram showing the state in which the detection mechanism unit 40-1 is installed on the steering wheel 100, and Figure 26(B) is a diagram viewed from the annular direction. As with the detection mechanism unit 40-1 shown in Figure 26, it may be shaped so that a wide member extends along the circumferential direction and covers part of the circumferential direction of the steering wheel.

[0095] Figure 27 is a schematic diagram of a second modified example 40-2 of the shape of the detection mechanism unit. Figure 27(A) is a diagram showing the state in which the detection mechanism unit 40-2 is installed on the steering wheel 100, and Figure 27(B) is a diagram viewed from the annular direction. As with the detection mechanism unit 40-2 shown in Figure 27, a belt-shaped member may be wound spirally around the steering wheel.

[0096] Fig. 28 is a schematic diagram of a third modified example 40-3 of the shape of the detection mechanism unit. As with the detection mechanism unit 40-3 shown in Fig. 28, a continuous S-shaped member may be wrapped around the steering wheel 100. In the case of a leather-wrapped steering wheel, for example, the continuous S-shaped detection mechanism unit 40-3 is installed in a location excluding the leather-wrapped thread portion.

[0097] [Other variations] Fig. 29 is a diagram showing a modified example of the transmission frequency. The horizontal axis of Fig. 29 indicates the frequency (Hz) of the vibration transmitted from the piezoelectric element, and the vertical axis indicates the amplitude. A configuration is also possible in which multiple frequencies (for example, three or five) of the vibration transmitted from the piezoelectric element are set, and these multiple frequencies are transmitted by switching between them, and the vibration level of each frequency band is detected. As shown in Fig. 29, the vibration level at each frequency changes between non-grasping and grasping. Grasping can be detected by comparing this change.

[0098] Furthermore, the three elements of the grip detection device 10, namely the transmitting piezoelectric element 20, the receiving piezoelectric element 30, and the detection mechanism unit 40, may be configured to be arranged at least inside the cover unit 103 on the surface of the steering wheel 100. For example, the grip detection device may be arranged on the outer surface of the core unit 101, the inner surface of the base unit 102, the outer surface of the base unit 102, or the inner surface of the cover unit 103. These surfaces may be radial surfaces, surfaces on the driver's side (front side), or surfaces opposite the driver's side (rear side).

[0099] Furthermore, in the above embodiment, the detection mechanism 40 is provided separately from the steering wheel 100 and is installed on the installation surface (groove 104, etc.) of the steering wheel 100, but the detection mechanism 40 may be formed in the core 101 of the steering wheel 100 itself. For example, the thin plate-like detection mechanism 40, the protrusion 41, and elements corresponding to the groove 104 may be integrally formed in a part of the core 101, and these elements may be used as the detection mechanism 40 of the above embodiment. This reduces the number of parts and suppresses manufacturing costs.

[0100] Furthermore, in the above embodiment, a configuration has been exemplified in which the plurality of protrusions 41 arranged on the back surface of the detection mechanism unit 40 are arranged at approximately equal intervals, but the arrangement intervals may be changed individually. Also, protrusions 41 do not need to be provided over the entire area of ​​the detection mechanism unit 40 in the longitudinal direction (annular direction), and protrusions 41 may be provided only in areas where grip detection is desired. In this case, in areas where grip detection is not desired, the intervals between protrusions 41 may be made extremely small to make the protrusions denser, thereby reducing the grip detection accuracy in those areas.

[0101] [Fifth embodiment] Fig. 30 is a schematic diagram showing the grip detection device 11 according to the fifth embodiment in an ungripped state. Fig. 31 is a schematic diagram showing the grip detection device 11 according to the fifth embodiment in a gripped state. As shown in Fig. 30, in the ungripped state, the vibrations transmitted from the transmitting piezoelectric element 20 are transmitted to the receiving piezoelectric element 30 while maintaining their amplitude in the urethane 45, and are measured by the receiving piezoelectric element 30. The urethane 45 is an example of a transmission section that transmits the vibrations transmitted from the transmitting piezoelectric element 20 to the receiving piezoelectric element 30, and is installed in at least the gripped portion of the steering wheel 100.

[0102] 31 , in the case of gripping, pressure due to the gripping force is applied to urethane 45 from the radially outer side. This pressure elastically deforms the urethane portion of urethane 45 between transmitting piezoelectric element 20 and receiving piezoelectric element 30, thereby attenuating the vibrations transmitted to that urethane portion of urethane 45. The attenuated vibrations are transmitted to receiving piezoelectric element 30 and measured by receiving piezoelectric element 30.

[0103] The grip detection device 11 also includes a casing 60 that houses the transmitter piezoelectric element 20. The casing 60 is an example of a spacer that ensures space for the transmitter piezoelectric element 20 to vibrate. The casing 60 ensures space (clearance 61) for the transmitter piezoelectric element 20 to vibrate, thereby preventing the movement of the transmitter piezoelectric element 20 from being suppressed by the urethane 45 and preventing the vibration amplitude of the transmitter piezoelectric element 20 from becoming extremely small. Therefore, the transmitter piezoelectric element 20 can be driven at a relatively low voltage, thereby preventing the generation of vibration noise that is unpleasant to passengers.

[0104] FIG. 32 is a schematic diagram illustrating the vibration mechanism when a casing is provided. The casing 60 houses the transmitter piezoelectric element 20 so that a clearance 61 exists around the transmitter piezoelectric element 20. The transmitter piezoelectric element 20 repeatedly expands and contracts in the radial direction when driven by the drive unit 51 of the control unit 50 described above. The transmitter piezoelectric element 20, which repeatedly expands and contracts in the radial direction, presses on the bracket 62 via the adhesive 64, causing the bracket 62 to vibrate. The presence of the clearance 61 between the transmitter piezoelectric element 20 and the inner wall of the casing 60 increases the amount of displacement of the transmitter piezoelectric element 20 even with a low drive voltage. This increases the impact on the bracket 62 and the resulting vibrations.

[0105] The casing 60 is sealed with a sealant 65 to prevent the urethane 45 from flowing into the internal space. The sealant 65 seals the gap between the bracket 62 and the casing 60. The sealant 65 may be sealing rubber or an adhesive.

[0106] Fig. 33 is a schematic diagram for explaining the vibration mechanism when there is no casing. When the transmitter piezoelectric element 20 is buried in urethane 45 as in Fig. 33, the expansion and contraction of the transmitter piezoelectric element 20 is suppressed by the urethane 45, so the amount of displacement of the transmitter piezoelectric element 20 is reduced. This reduces the impact on the bracket 62, and the generated vibration amplitude becomes smaller.

[0107] FIG. 34 shows a state in which a portion of the core 101 of a steering wheel is covered with urethane 45. The urethane 45 covers the core 101 except for the hub 101a, and in this example, covers the annular rim and the multiple spokes connecting the hub 101a and the rim. The urethane 45 covers the casing 60 that houses the transmitting piezoelectric element 20, the bracket 62 that secures the casing 60 to the core 101, the uncased receiving piezoelectric element 30, and the bracket 63 that secures the receiving piezoelectric element 30 to the core 101. The urethane 45 corresponds to the base 102 sandwiched between the core 101 and the cover 103 in FIG. 3, for example. The urethane 45 is a resin that is softer than the core 101.

[0108] Figure 35 is a diagram showing a state where urethane 45 has been removed. Figure 36 is a diagram showing an example of attaching bracket 62 to core 101. Bracket 62 is fixed to core 101 by fastening members such as rivets 66.

[0109] 34 to 36, the transmitting piezoelectric element 20 and the receiving piezoelectric element 30 are arranged in the 6 o'clock direction of the steering wheel 100, but they may be arranged in any direction (position) other than this direction as long as they are covered with urethane 45. For example, the transmitting piezoelectric element 20 and the receiving piezoelectric element 30 may be arranged in the gripping portion of the steering wheel 100 in the 12 o'clock direction. The transmitting piezoelectric element 20 and the receiving piezoelectric element 30 may not be arranged in the same direction on the steering wheel 100, but may be arranged in different directions on the steering wheel 100. For example, the transmitting piezoelectric element 20 may be arranged in the gripping portion of the steering wheel 100 in the 6 o'clock direction, and the receiving piezoelectric element 30 may be arranged in the gripping portion of the steering wheel 100 in the 12 o'clock direction.

[0110] FIG. 37 is a diagram showing the space between the core 101 and bracket 62 of the steering wheel. A space is provided between the core 101 and bracket 62 to allow urethane 45 to flow in. This space is filled with urethane 45. As a result, the vibration of the transmitter piezoelectric element 20 inside the casing 60 is transmitted to the core 101 via the urethane 45 that has filled the space between the bracket 62 and the core 101. The transmitter piezoelectric element 20 is housed in the casing 60 so that the urethane 45 does not flow into the interior of the casing 60.

[0111] 38 is a diagram illustrating the arrangement of the transmitting piezoelectric element, the receiving piezoelectric element, and the control unit. The control unit 50 is installed in a hub located in the center of the inside of the steering wheel 100. The transmitting piezoelectric element 20 and the casing 60 are fixed to the core part 101 at the 6 o'clock position of the steering wheel 100 by a bracket 62. The receiving piezoelectric element 30 is fixed to the core part 101 at the 6 o'clock position of the steering wheel 100 by a bracket 63. The above-mentioned drive unit 51 of the control unit 50 is connected to the transmitting piezoelectric element 20 by a wiring 67, and the above-mentioned signal processing unit 52 of the control unit 50 is connected to the receiving piezoelectric element 30 by a wiring 68.

[0112] Fig. 39 is a cross-sectional view of a first structural example of a casing attached to a bracket, illustrating a form in which the casing is attached to the bracket. Fig. 40 is an exploded perspective view of the first structural example of a casing attached to a bracket, illustrating a form in which the casing is attached to the bracket. The casing 60 is attached to the bracket 62 so that the transmitter piezoelectric element 20 is sandwiched between the casing 60 and the bracket 62. The transmitter piezoelectric element 20 is electrically connected to wiring 67.

[0113] Fig. 41 is a cross-sectional view of a second structural example of a casing attached to a detection mechanism unit, illustrating a form in which the casing is attached to the detection mechanism unit. Fig. 42 is an exploded perspective view of the second structural example of a casing attached to a detection mechanism unit, illustrating a form in which the casing is attached to the detection mechanism unit. The detection mechanism unit 40 and the transmitter piezoelectric element 20 are sandwiched between casings 60A and 60B. The casing 60A is attached to the casing 60B so that the transmitter piezoelectric element 20 is sandwiched between the casing 60A and the detection mechanism unit 40.

[0114] 43 is a cross-sectional view showing a third structural example of the casing. The casing 60 may be a cover that is attached to the bracket 32 ​​so as to be able to open and close. The transmitting piezoelectric element 20 is fixed to the inner wall of the bracket 32.

[0115] 44 is a cross-sectional view showing a fourth structural example of the casing. The casing 60 may be fitted into the core 101. The transmitter piezoelectric element 20 is fixed to the inner wall of the casing 60.

[0116] 45 is a cross-sectional view showing a first structural example of the spacer. The transmitter piezoelectric element 20 is attached to a protrusion 62a provided on a bracket 62. The protrusion 62a is an example of a spacer that ensures a space (clearance 61) for the transmitter piezoelectric element 20 to vibrate. Because the clearance 61 exists, the urethane 45 may come into contact with the transmitter piezoelectric element 20.

[0117] 46 is a cross-sectional view showing a second structural example of the spacer. The bracket 62 is attached to the core 101 so as to form a space (clearance 61) between the bracket 62 and the core 101. The transmitter piezoelectric element 20 is placed in this space. The bracket 62 has a side wall 62b that partitions the space.

[0118] 47 is a cross-sectional view showing a first structural example of the bracket. Holes are formed in the core 101 and the bracket 62, and rivets 66 are inserted into the holes. The bracket 62 is fixed to the core 101 by the rivets 66. The transmitting piezoelectric element 20, which is housed in a casing (not shown), is fixed to the bracket 62.

[0119] 48 is a cross-sectional view showing a second structural example of the bracket. The bracket 62 is an attachment that is attached so as to surround the core part 101. The transmitter piezoelectric element 20, which is housed in a casing (not shown), is fixed to the bracket 62.

[0120] 49 is a cross-sectional view showing a third structural example of the bracket. The bracket 62 is an attachment that is hooked onto and fixed to the edge of the core part 101. The transmitter piezoelectric element 20 housed in a casing (not shown) is fixed to the bracket 62.

[0121] 50 is a cross-sectional view showing a fourth structural example of the bracket. Bracket 62 is a molded part that molds core part 101 with resin or the like. Transmission-side piezoelectric element 20, which is housed in a casing (not shown), is fixed to bracket 62.

[0122] 51 is a cross-sectional view showing a fifth structural example of the bracket. The bracket 62 may be adhered to the core 101 with adhesive 64. The transmitter piezoelectric element 20 housed in a casing (not shown) is fixed to the bracket 62.

[0123] 52 is a cross-sectional view showing a sixth structural example of the bracket. The bracket 62 may be fixed to the core 101 by at least one screw 69. The transmitter piezoelectric element 20 housed in a casing (not shown) is fixed to the bracket 62.

[0124] 53 is a cross-sectional view showing a seventh structural example of the bracket. A part of the housing of the control unit 50 may be used as a bracket 62 for fixing the transmitter piezoelectric element 20. The transmitter piezoelectric element 20, which is housed in a casing (not shown), is fixed to the bracket 62.

[0125] 54 is a cross-sectional view showing an eighth structural example of the bracket. The bracket 62 with the connector 62c is embedded in the urethane 45 at the 6 o'clock position. The connector 62c, which is electrically connected to the transmitter piezoelectric element 20, protrudes from the urethane 45. The transmitter piezoelectric element 20, which is housed in a casing (not shown), is fixed to the bracket 62. The connector 62c is electrically connected to a connector 50c of the control unit 50, thereby integrating the transmitter piezoelectric element 20 and the control unit 50.

[0126] 55 is a cross-sectional view showing a ninth structural example of the bracket. A connector 62c electrically connected to the transmitter piezoelectric element 20 protrudes from the urethane 45. The transmitter piezoelectric element 20, housed in a casing (not shown), is fixed to the bracket 62. The connector 62c is electrically connected to a connector 71c of the display device 71, thereby integrating the transmitter piezoelectric element 20 and the display device 71. The transmitter piezoelectric element 20 may be connected to the control unit 50 via the display device 71. The display device 71 notifies the occupant of the gripping state determined by the control unit 50 by displaying light or the like.

[0127] 56 is a diagram showing a tenth structural example of the bracket. Holes are formed in the core 101 and the bracket 62, and rivets 66 are inserted into them. The bracket 62 is fixed to the core 101 by the rivets 66. The transmitter piezoelectric element 20 housed in a casing (not shown) is fixed to the bracket 62, which is also used for the receiver piezoelectric element 30. The transmitter piezoelectric element 20 may face the transmitter piezoelectric element 20, or may be adjacent to the transmitter piezoelectric element 20.

[0128] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise. [Explanation of symbols]

[0129] 10, 10A, 10B, 10C, 10D, 10E, 11 Grip detection device 20. Transmitting piezoelectric element 20A First transmitting piezoelectric element 20B Second transmitting piezoelectric element 21 Piezoelectric element for both transmission and reception 30 Receiving piezoelectric element 30A First receiving piezoelectric element 30B Second receiving piezoelectric element 40, 40-1, 40-2, 40-3 Detection mechanism 40A First detection mechanism 40B Second detection mechanism 41, 41A, 41B, 41C, 41D, 41E, 41F Convex part (clearance part) 42 square dots 43 semicircular dots 44 hemispherical dots 45 Urethane 50,50D control section 51 Drive unit 52 Signal processing section 53 AD conversion section 54 Processing unit 55 Drive circuit 56 Switching Circuit 57 Receiving circuit 58 Signal Processing Circuit 60, 60A, 60B casing 61 Clearance 62,63 Bracket 64 Adhesive 65 Sealant 66 Rivet 67,68 Wiring 69 screws 71 Display device 100 steering wheel 101 Core 102 Base 103 Cover part 104 Groove (installation surface)

Claims

1. A grip detection device for detecting whether an occupant of a vehicle is gripping a steering wheel, A transmitting piezoelectric element; a receiving piezoelectric element; a transmission unit that is installed at least in a grip portion of the steering wheel and that transmits the vibrations transmitted from the transmission-side piezoelectric element to the reception-side piezoelectric element; a spacer that ensures a space for the transmission unit or the transmission-side piezoelectric element to vibrate; A grip detection device comprising:

2. The grip detection device according to claim 1 , wherein the spacer provides a clearance between the transmission unit and an installation surface on the steering wheel on which the transmission unit is installed.

3. The grip detection device according to claim 2 , wherein the transmission part is a plate made of resin.

4. The grip detection device according to claim 2 or 3, wherein the spacer is a convex portion protruding from a rear surface of the transmission portion.

5. The grip detection device according to claim 2 , wherein a groove for engaging the transmission unit is provided in an installation portion of the steering wheel where the transmission unit is installed, and the installation surface is a bottom surface of the groove.

6. the receiving piezoelectric element has a first receiving piezoelectric element and a second receiving piezoelectric element, The transmission unit is a first detection mechanism that connects the transmitting piezoelectric element and the first receiving piezoelectric element and transmits vibrations transmitted from the transmitting piezoelectric element to the first receiving piezoelectric element; a second detection mechanism that connects the transmitting piezoelectric element and the second receiving piezoelectric element and transmits the vibration transmitted from the transmitting piezoelectric element to the second receiving piezoelectric element; The grip detection device according to claim 2 , further comprising:

7. the transmitter piezoelectric element has a first transmitter piezoelectric element and a second transmitter piezoelectric element, The transmission unit is a first detection mechanism that connects the first transmitting piezoelectric element and the receiving piezoelectric element and transmits vibrations transmitted from the first transmitting piezoelectric element to the receiving piezoelectric element; a second detection mechanism that connects the second transmitting piezoelectric element and the receiving piezoelectric element and transmits the vibration transmitted from the second transmitting piezoelectric element to the receiving piezoelectric element; The grip detection device according to claim 2 , further comprising:

8. The grip detection device according to claim 1 , wherein the spacer is a casing that houses the transmitting piezoelectric element and ensures a space for the transmitting piezoelectric element to vibrate.

9. The grip detection device according to claim 8 , wherein the transmission portion is located between a core portion and a cover portion of the steering wheel and is softer than the core portion.

10. The grip detection device according to claim 9 , wherein the transmission part is made of urethane.

11. A grip detection device for detecting whether an occupant of a vehicle is gripping a steering wheel, a piezoelectric element; a detection mechanism unit that is connected to the piezoelectric element, transmits vibrations emitted from the piezoelectric element, and returns the vibrations to the piezoelectric element, and is installed at least in a grip portion of the steering wheel; a clearance portion that provides a clearance between the detection mechanism portion and an installation surface on the steering wheel on which the detection mechanism portion is installed; A grip detection device comprising:

12. A steering wheel comprising the grip detection device according to any one of claims 1 to 11.

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