Vibration device and imaging device

Abstract

The present disclosure provides a vibration device and an imaging device capable of suppressing local application of a large vibration stress to a light-transmitting body if foreign matter adhering to a surface of the light-transmitting body is removed by vibrating the light-transmitting body. A vibration device (10) comprises: a light-transmitting body that transmits light of a prescribed wavelength; an internal vibration body (3) that contacts the light-transmitting body and vibrates the light-transmitting body; a piezoelectric element (5) provided to the internal vibration body (3); and an external vibration body (2) in which a holding part that holds the light-transmitting body has a cylindrical shape, and which covers the internal vibration body (3). In the portion of the internal vibration body (3) that contacts the light-transmitting body, the percentage of a value obtained by subtracting 1 from a ratio of a displacement amount of a second portion on an outer side to a displacement amount of a first portion on an inner side is 2.5% or less.

Description

Vibration device and imaging device

[0001] The present disclosure relates to a vibration device and an imaging device.

[0002] In recent years, vehicles are provided with imaging devices at the front and rear of the vehicle in order to control safety devices or perform driving assistance control using images obtained by the imaging devices. Such imaging devices are often provided outside the vehicle, and foreign substances such as raindrops (water droplets), mud, and dust adhere to the light-transmitting body (protective cover or lens) that covers the outside.

[0003] When foreign substances adhere to the light-transmitting body, the foreign substances are reflected in the image obtained by the imaging device, and a clear image cannot be obtained. Therefore, in Japanese Patent Application Laid-Open No. 2017-170303 (Patent Document 1), an imaging device is provided with a droplet elimination device (vibration device) that vibrates the light-transmitting body in order to remove foreign substances adhering to the surface of the light-transmitting body.

[0004] Japanese Patent Application Laid-Open No. 2017-170303

[0005] When vibrating the light-transmitting body to remove foreign substances adhering to the surface of the light-transmitting body, the vibration stress of the vibration device is applied to the light-transmitting body in order to vibrate the light-transmitting body by the vibration device. If the vibration stress of the vibration device is not uniformly applied to the light-transmitting body, but a locally large vibration stress is applied to the light-transmitting body, there is a risk of damaging the light-transmitting body.

[0006] Therefore, an object of the present disclosure is to provide a vibration device and an imaging device that can suppress the application of a locally large vibration stress to the light-transmitting body when vibrating the light-transmitting body to remove foreign substances adhering to the surface of the light-transmitting body.

[0007] The vibration device according to one aspect of the present disclosure includes a light-transmitting body that transmits light of a predetermined wavelength, an internal vibration body that contacts the light-transmitting body and vibrates the light-transmitting body, a piezoelectric element provided on the internal vibration body, and a holding portion that holds the light-transmitting body having a cylindrical shape, and an external vibration body that covers the internal vibration body. The internal vibration body has a percentage of a value obtained by subtracting 1 from the ratio of the displacement amount of the outer second portion to the displacement amount of the inner first portion at a portion where it contacts the light-transmitting body of 2.5% or less.

[0008] An imaging device according to one embodiment of the present disclosure comprises the above-mentioned vibrating device and an imaging sensor arranged such that the light-transmitting material is in the direction of the field of view.

[0009] According to this disclosure, the internal vibrating body, at the portion in contact with the transparent material, has a value of 2.5% or less obtained by subtracting 1 from the ratio of the displacement of the outer second part to the displacement of the inner first part. Therefore, it is possible to suppress the application of large localized vibration stress to the transparent material and reduce damage to the transparent material.

[0010] This is a schematic diagram of the imaging device according to the embodiment. This is a cross-sectional view of the imaging device according to the embodiment. This is a half-cross-sectional view for explaining the displacement and stress occurring in a comparative vibration device. This is a graph for explaining the relationship between the displacement ratio and stress between the inner and outer parts of the internal vibrator. This is a half-cross-sectional view for explaining the displacement and vibration stress occurring in the vibration device according to the embodiment. This is a graph for explaining the relationship between the axial length of the first cylindrical part of the internal vibrator, the axial length of the holding part, and the vibration stress. This is a half-cross-sectional view for explaining the outer diameter of the spring part of the internal vibrator and the inner diameter of the holding part of the external vibrator. This is a half-cross-sectional view for explaining the thickness and axial length of each part of the internal vibrator. This is a graph for explaining the relationship between the axial length of the first cylindrical part of the internal vibrator and the axial length of the spring part. This is a half-cross-sectional view for explaining the positional relationship between the internal vibrator and the holding part of the external vibrator.

[0011] The imaging device described below will be explained in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts. The imaging device described below is, for example, for automotive use and can vibrate a translucent material (e.g., the outermost lens) to remove foreign matter adhering to its surface. The imaging device is not limited to automotive applications. For example, the imaging device can also be applied to security cameras, drones, etc.

[0012] (Embodiment) Figure 1 is a schematic diagram of the imaging device 100 according to the embodiment. Figure 2 is a cross-sectional view of the imaging device 100 according to the embodiment. In the figures, the X, Y, and Z directions indicate the depth, lateral, and height directions of the imaging device 100, respectively. The imaging device 100 includes a vibrator 10 and a sensor device 20. The vibrator 10 includes an outermost lens 1, an external vibrator 2, an internal vibrator 3, and a piezoelectric element 5. The sensor device 20 includes an inner lens 4 and a bracket 8 that holds the image sensor 6.

[0013] After aligning the outermost lens 1, the innermost lens 4, and the image sensor 6, the sensor device 20 is joined to the vibration device 10 to form the imaging device 100. The image sensor 6 is an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and is mounted on the circuit board 61. The circuit board 61 also has semiconductor elements such as general-purpose ICs (Integrated Circuits) and ASICs (Application Specific Integrated Circuits) mounted on it to control the image sensor 6.

[0014] The bracket 8 also includes a drive circuit 7 on which semiconductor elements that generate signals for driving the piezoelectric element 5 are mounted. The drive circuit 7 is electrically connected to the piezoelectric element 5 via wiring 51, and is also electrically connected to external circuits and power supplies via wiring 71. The retaining plate 41 that holds the inner layer lens 4 and the circuit board 61 are fixed to the bracket 8, respectively, in positions where the alignment of the inner layer lens 4 and the image sensor 6 is adjusted with respect to the outermost layer lens 1. The bracket 8 is closed off on the side opposite to the side that connects to the vibration device 10 by a bottom plate 81. The bracket 8 is made of, for example, aluminum (A5052).

[0015] The outermost lens 1 is a light-transmitting material that transmits light of a predetermined wavelength (for example, the wavelength of visible light, the wavelength that can be imaged by the image sensor, etc.), and is, for example, borosilicate crown glass (BK7), quartz glass, crown glass, flint glass, or a convex meniscus lens. The vibration device 10 may use a transparent material such as a protective cover instead of the outermost lens 1. The protective cover is made of glass or a resin such as transparent plastic.

[0016] The outermost lens 1 is held at the end 2b of a cylindrical holding portion 2a that extends in the Z direction. By designing the imaging device 100 to hold the outermost lens 1 at the end 2b of the holding portion 2a, interference with other devices can be avoided when mounted on a vehicle or the like, and the degree of freedom in installation location is increased. Although the shape of the holding portion 2a is described as cylindrical in Figure 1, it is not limited to a cylindrical shape and may be a polygonal prism shape such as a rectangular prism or a pentagonal prism.

[0017] The end portion 2b of the holding portion 2a is in contact with the outermost lens 1, with the retainer 21 in between. The retainer 21 may be made of a resin such as polyphenylene sulfide (PPS) or a metal such as stainless steel (SUS304, SUS420, SUS440). The end portion 2b of the holding portion 2a, the retainer 21, the outermost lens 1, and the internal vibrator 3 are bonded together, for example, with an adhesive. In Figure 1, the external vibrator 2 indirectly holds the outermost lens 1 via the retainer 21, but it may also be held directly by the end portion 2b of the holding portion 2a.

[0018] The external vibrator 2 includes a holding portion 2a, a cylindrical housing portion 2c with a larger diameter than the holding portion 2a, and a connecting portion 2d that connects the holding portion 2a and the housing portion 2c. The connecting portion 2d is a disc shape that extends radially (X, Y direction) from the holding portion 2a. The external vibrator 2 has a shape in which two cylinders of different diameters (holding portion 2a and housing portion 2c) are connected by a disc (connecting portion 2d).

[0019] The holding portion 2a undergoes elastic deformation in the axial direction (Z direction) of the cylinder due to vibrations from the internal vibrator 3, as will be described later. However, since the housing portion 2c is provided with a weight 2e, vibrations from the internal vibrator 3 can be suppressed, and it hardly displaces. Therefore, vibrations from the internal vibrator 3 are not transmitted from the housing portion 2c to the sensor device 20, and by attaching the housing portion 2c and the sensor device 20 to a vehicle or the like, vibration leakage from the internal vibrator 3 to the vehicle or the like can be prevented. The external vibrator 2, including the holding portion 2a, end portion 2b, housing portion 2c, connecting portion 2d, and weight 2e, may be formed as a single unit or individually. The external vibrator 2 may be made of, for example, stainless steel (SUS304, SUS420, SUS440).

[0020] As shown in Figure 2, the vibration device 10 is in contact with the internal vibrator 3 in order to vibrate the outermost lens 1. The internal vibrator 3 is cylindrical in shape and consists of a first cylindrical portion 31 that is in contact with the outermost lens 1, a second cylindrical portion 32 on which a piezoelectric element 5 is provided, and a spring portion 33 that connects the first cylindrical portion 31 and the second cylindrical portion 32. The cross-sectional shape of the spring portion 33 is S-shaped. The inner lens 4 is placed inside the cylinder of the internal vibrator 3. The internal vibrator 3 is made of, for example, stainless steel (SUS304, SUS420, SUS440).

[0021] The first cylindrical portion 31 is a cylindrical shape extended in the axial direction (Z direction) of the cylinder, and its end portion 31a contacts the peripheral edge of the outermost lens 1, transmitting vibrations of the internal vibrator 3 to the outermost lens 1. The first cylindrical portion 31 has an end portion 31a that extends in the radial direction (X, Y direction) of the cylinder in order to stably hold the outermost lens 1.

[0022] The second cylindrical portion 32 vibrates along with the vibration of the piezoelectric element 5, and its thickness is greater than that of the first cylindrical portion 31 and the spring portion 33. This makes it easier to efficiently transmit the vibration of the piezoelectric element 5 through the outermost lens 1.

[0023] The spring portion 33 supports the first cylindrical portion 31 and transmits vibrations of the second cylindrical portion 32 to the first cylindrical portion 31. The first cylindrical portion 31, the second cylindrical portion 32, and the spring portion 33 may be formed as a single unit or individually. Furthermore, although the cross-sectional shape of the spring portion 33 has been described as S-shaped, any shape that can transmit vibrations of the second cylindrical portion 32 to the first cylindrical portion 31 (for example, a shape with two S-shapes connected together) is acceptable.

[0024] The piezoelectric element 5 is provided on the surface of the second cylindrical portion 32 opposite to the side that contacts the outermost lens 1. The piezoelectric element 5 is hollow and circular, and vibrates by polarization in the thickness direction, for example. The piezoelectric element 5 is made of lead zirconate titanate piezoelectric ceramics. ３ Other piezoelectric ceramics such as LiTaO may also be used. ３ Piezoelectric single crystals such as the above may be used.

[0025] The hollow circular piezoelectric element 5 vibrates radially, and this vibration is converted into vibration in the Z direction (up and down direction in the figure) by the spring portion 33 of the internal vibrator 3, causing the outermost lens 1 to vibrate in the Z direction. The vibration device 10 can vibrate the outermost lens 1 in the Z direction and remove foreign matter adhering to the surface of the outermost lens 1.

[0026] When an imaging device 100 equipped with such a vibration device 10 is attached to a vehicle body, the holding portion 2a of the outermost lens 1 needs to be extended in the Z direction in order to align the position of the outermost lens 1 with the surface of the vehicle body. Similarly, when a cover for restricting external protrusions is provided on the imaging device 100, the holding portion 2a of the outermost lens 1 needs to be extended in the Z direction in order to align the position of the outermost lens 1 with the surface of the cover. However, if the shape of the holding portion 2a is made cylindrical and the axial length is increased, the axial length of the first cylindrical portion 31 of the internal vibrator 3 also simply increases. When the axial length of the first cylindrical portion 31 increases, the rigidity decreases, and when the outermost lens 1 is vibrated, a large localized vibration stress is applied to the outermost lens 1, which could damage the outermost lens 1.

[0027] Figure 3 is a semi-cross-sectional view illustrating the displacement and stress generated in the comparison vibrator. The vibrator shown in Figure 3 has a cylindrical shape for the holding part, increasing its axial length, and the axial length of the first cylindrical part of the internal vibrator is also simply increased. Figure 3 shows the results of a vibration simulation performed on the comparison vibrator, with Figure 3(a) showing the amount of displacement generated in the comparison vibrator and Figure 3(b) showing the stress generated in the comparison vibrator. The vibration simulation was calculated using the finite element method, with Femtet® (registered trademark) used as the CAE (Computer Aided Engineering) software, and piezoelectric / resonance analysis selected as the analysis condition.

[0028] In Figure 3(a), the magnitude of displacement is indicated by the intensity of the hatching, with darker hatching indicating areas of greater displacement. In the comparative vibrator shown in Figure 3(a), the displacement of the largest displaced part is approximately 5 μm. When the axial length of the first cylindrical part of the internal vibrator is also increased, as in the comparative vibrator, the rigidity of the first cylindrical part decreases, and at the part in contact with the outermost lens, the displacement of the outer part (second part) becomes greater than the displacement of the inner part (first part). In other words, the first cylindrical part of the internal vibrator generates a rotational moment as shown by arrow M1 in Figure 3(a).

[0029] When a rotational moment is generated in the first cylindrical portion that contacts the outermost lens, the end of the outermost lens is pulled by the external vibrator due to this rotational moment. As a result, a large localized vibrational stress is applied to the end of the outermost lens, as shown in Figure 3(b). In Figure 3(b), the magnitude of the stress is indicated by the density of the hatching, with darker hatching indicating areas of high stress. In the vibrating device shown in Figure 3(b), the stress at the point where the greatest stress is applied is approximately 20 MPa.

[0030] From the vibration simulation of the comparative vibration device shown in Figure 3, it was found that when the displacement of the outer part is larger than the displacement of the inner part, a large localized vibration stress is applied to the edge of the outermost lens 1 in the region indicated by arrow S1, and there is a risk that the outermost lens 1 may break. Therefore, in the vibration device 10 according to this embodiment, in order to reduce the risk of damage to the outermost lens 1, we will consider to what extent the displacement of the outer part needs to be suppressed relative to the displacement of the inner part at the part in contact with the outermost lens 1.

[0031] Figure 4 is a graph illustrating the relationship between the displacement ratio between the inner and outer parts of the internal vibrating body 3 and the stress. Figure 4 shows the results of a vibration simulation performed on the vibration device 10, with the horizontal axis representing the displacement ratio between the inner and outer parts (in %) and the vertical axis representing the vibration stress applied to the outermost lens 1 (in MPa). The displacement ratio between the inner and outer parts is expressed as a percentage, obtained by subtracting 1 from the ratio of the displacement of the outer part to the displacement of the inner part.

[0032] It is known that when the vibration stress applied to the outermost lens 1 is approximately 20 MPa or less, the risk of damage to the outermost lens 1 decreases. Therefore, as can be seen from graph A in Figure 4, in order to satisfy the condition that the vibration stress applied to the outermost lens 1 is approximately 20 MPa or less, it is necessary that the displacement ratio between the inner part and the outer part be approximately 2.5% or less. In other words, if the displacement ratio between the inner part and the outer part of the vibration device 10 is approximately 2.5% or less, the risk of damage to the outermost lens 1 is low even if the displacement of the outer part is larger than the displacement of the inner part.

[0033] Of course, if the displacement of the inner part and the displacement of the outer part are the same, no rotational moment will be generated in the first cylindrical part 31 of the internal vibrator 3. In other words, it is even more preferable if the displacement ratio between the inner part and the outer part of the vibrating device 10 is 0.0%.

[0034] Therefore, in order to make it difficult to generate a rotational moment in the first cylindrical portion 31 of the internal vibrating body 3, the vibration device 10 should be designed in a way that does not reduce the rigidity of the first cylindrical portion 31.

[0035] In order to increase the rigidity of the first cylindrical portion 31 and to keep the displacement ratio between the inner and outer portions at approximately 2.5% or less, the vibration device 10, as an example, has the axial length H2 of the first cylindrical portion 31 shorter than the axial length H1 of the holding portion 2a of the external vibrator 2 (H1 > H2), as shown in Figure 2. In this embodiment, the axial length H2 of the first cylindrical portion 31 is the axial length of the first cylindrical portion 31 excluding the end portion 31a, as shown in Figure 2.

[0036] Figure 5 is a semi-cross-sectional view illustrating the displacement and stress generated in the vibrating device 10. In the vibrating device 10 shown in Figure 5, the shape of the holding part 2a is cylindrical and its axial length is increased, but the axial length of the first cylindrical part 31 of the internal vibrating body 3 is shortened. Figure 5 shows the results of a vibration simulation performed on the vibrating device 10, with Figure 5(a) showing the amount of displacement generated in the vibrating device 10 and Figure 5(b) showing the stress generated in the vibrating device 10. The vibration simulation was calculated using the finite element method, with Femtet® registered trademark used as the CAE software, and piezoelectric / resonance analysis selected as the analysis condition.

[0037] In Figure 5(a), the magnitude of the displacement is indicated by the intensity of the hatching, with darker hatching indicating areas of greater displacement. In the vibrating device 10 shown in Figure 5(a), the displacement of the largest displaced part is approximately 5 μm. In the vibrating device 10, since the axial length of the first cylindrical part 31 of the internal vibrating body 3 is short, the rigidity of the first cylindrical part 31 does not decrease, and the displacement of the inner part (first part) and the outer part (second part) in the part in contact with the outermost lens 1 are approximately the same. In other words, the first cylindrical part 31 of the internal vibrating body 3 is displaced parallel to the part in contact with the outermost lens 1, as shown by arrow M2 in Figure 5(a).

[0038] Since the portion of the first cylindrical part 31 that contacts the outermost lens 1 is displaced parallel to it, the end of the outermost lens 1 is not pulled by the external vibrator 2. As a result, a nearly uniform vibration stress is applied to the end of the outermost lens 1, as shown in Figure 5(b). In Figure 5(b), the magnitude of the stress is indicated by the density of the hatching, with darker hatching indicating areas of high stress. In the vibration device shown in Figure 5(b), the stress at the point where the greatest stress is applied is approximately 20 MPa.

[0039] From the vibration simulation of the vibration device 10 shown in Figure 5, it was found that by making the axial length of the first cylindrical portion 31 of the internal vibrator 3 shorter than the axial length of the holding portion 2a of the external vibrator 2, a substantially uniform vibration stress can be applied to the outermost lens 1, thereby reducing damage to the outermost lens 1. Furthermore, in the vibration device 10 according to this embodiment, the relationship between the axial length H2 of the first cylindrical portion 31, the axial length H1 of the holding portion 2a of the external vibrator 2, and the vibration stress will be examined.

[0040] Figure 6 is a graph illustrating the relationship between the axial length of the first cylindrical portion 31 of the internal vibrator 3, the axial length of the holding portion 2a, and the vibration stress. Figure 6 shows the results of vibration simulations performed on the vibration device 10 by varying the axial length H2 of the first cylindrical portion 31. The horizontal axis represents the length ratio of the cylindrical portions of the external vibrator 2 and the internal vibrator 3 (in %), and the vertical axis represents the vibration stress applied to the outermost lens 1 (in MPa). The length ratio of the cylindrical portions of the external vibrator 2 and the internal vibrator 3 is expressed as a percentage obtained by subtracting 1 from the ratio of the axial length of the first cylindrical portion 31 to the axial length of the holding portion 2a.

[0041] From graph B shown in Figure 6, it can be seen that the length ratio of the cylindrical portion between the external vibrator 2 and the internal vibrator 3 satisfies the condition that the vibration stress applied to the outermost lens 1 is approximately 20 MPa or less, and is approximately -63% or less. In other words, if the length ratio of the cylindrical portion between the external vibrator 2 and the internal vibrator 3 of the vibration device 10 is approximately -63% or less, damage to the outermost lens 1 can be reduced.

[0042] As shown in FIG. 2, the vibration device 10 has a portion where the cross-sectional shape of the spring portion 33 of the internal vibrator 3 is S-shaped and protrudes toward the external vibrator 2. Therefore, if the axial length H1 of the holding portion 2a of the external vibrator 2 is increased and the axial length H2 of the first cylindrical portion 31 is decreased in the vibration device 10, it is conceivable that the spring portion 33 of the internal vibrator 3 and the holding portion 2a of the external vibrator 2 come into contact with each other. FIG. 7 is a semi-sectional view for explaining the outer diameter R2 of the spring portion 33 of the internal vibrator 3 and the inner diameter R1 of the holding portion 2a of the external vibrator 2.

[0043] When the axial length H1 of the holding portion 2a of the external vibrator 2 is increased and the axial length H2 of the first cylindrical portion 31 is decreased in the vibration device 10, as shown in FIG. 7, the spring portion 33 of the internal vibrator 3 is disposed inside the holding portion 2a of the external vibrator 2. Since the spring portion 33 has a portion where the cross-sectional shape is S-shaped and protrudes toward the external vibrator 2, it is necessary to limit so as not to contact the holding portion 2a of the external vibrator 2.

[0044] Specifically, the outer diameter R2 of the spring portion 33 of the internal vibrator 3 is made smaller than the inner diameter R1 of the holding portion 2a of the external vibrator 2. Thereby, even if the axial length H1 of the holding portion 2a of the external vibrator 2 is increased and the axial length H2 of the first cylindrical portion 31 is decreased in the vibration device 10, the spring portion 33 can vibrate the outermost layer lens 1 without contacting the holding portion 2a.

[0045] Further, if the rigidity of the first cylindrical portion 31 is not decreased in the vibration device 10, no rotational moment occurs in the portion of the first cylindrical portion 31 that contacts the outermost layer lens 1, and no large vibration stress is applied to the end portion of the outermost layer lens 1. Therefore, the shape of the first cylindrical portion 31 is further examined from the viewpoint of rigidity. FIG. 8 is a semi-sectional view for explaining the thickness and axial length of each part of the internal vibrator 3.

[0046] In the internal vibrator 3, as shown in FIG. 8, the axial length H2 of the first cylindrical portion 31, the thickness W1 of the first cylindrical portion 31, the axial length H3 of the spring portion 33, and the thickness W2 of the spring portion 33 are set. The axial length H2 of the first cylindrical portion 31, the thickness W1 of the first cylindrical portion 31, the axial length H3 of the spring portion 33, and the thickness W2 of the spring portion 33 are changed, and a vibration simulation is performed on the vibration device 10.

[0047] The results of the vibration simulation are shown in FIG. 9. FIG. 9 is a graph for explaining the relationship between the axial length of the first cylindrical portion 31 of the internal vibrator 3 and the axial length of the spring portion 33. In FIG. 9, the horizontal axis represents the axial length ratio (unit: %) between the first cylindrical portion 31 and the spring portion 33, and the vertical axis represents the vibration stress (unit: MPa) applied to the outermost lens 1. The axial length ratio between the first cylindrical portion 31 and the spring portion 33 is expressed as a percentage of the value obtained by subtracting 1 from the ratio of the axial length H2 of the first cylindrical portion 31 to the axial length H3 of the spring portion 33. For example, when the axial length ratio between the first cylindrical portion 31 and the spring portion 33 is about -49%, the axial length H2 of the first cylindrical portion 31 is about 2.5 mm, and the axial length H3 of the spring portion 33 is about 4.9 mm.

[0048] In FIG. 9, a graph is shown in which the axial length H3 of the spring portion 33 is fixed at about 4.9 mm and the axial length H2 of the first cylindrical portion 31 is changed from about 2.5 mm to about 1.2 mm. That is, the axial length ratio between the first cylindrical portion 31 and the spring portion 33 changes in the range of about -49% to about -76%. The axial length H1 of the holding portion 2a of the external vibrator 2 is fixed at about 5.1 mm, and the length ratio of the cylindrical portions of the external vibrator 2 and the internal vibrator 3 changes in the range of about -51% to about -76%.

[0049] Further, in FIG. 9, a plurality of graphs are shown in which the axial length ratio between the first cylindrical portion 31 and the spring portion 33 is changed for the internal vibrator 3 having different thickness ratios (unit: %) between the first cylindrical portion 31 and the spring portion 33. Graph C shows that the thickness ratio between the first cylindrical portion 31 and the spring portion 33 is 0%, for example, the thickness W1 of the first cylindrical portion 31 is about 0.7 mm, and the thickness W2 of the spring portion 33 is about 0.7 mm. Graph D shows that the thickness ratio between the first cylindrical portion 31 and the spring portion 33 is about 14%, for example, the thickness W1 of the first cylindrical portion 31 is about 0.8 mm, and the thickness W2 of the spring portion 33 is about 0.7 mm.

[0050] Graph E shows a thickness ratio of approximately 29% between the first cylindrical part 31 and the spring part 33, for example, with a thickness W1 of approximately 0.9 mm for the first cylindrical part 31 and a thickness W2 of approximately 0.7 mm for the spring part 33. Graph F shows a thickness ratio of approximately 43% between the first cylindrical part 31 and the spring part 33, for example, with a thickness W1 of approximately 1.0 mm for the first cylindrical part 31 and a thickness W2 of approximately 0.7 mm for the spring part 33. Graph G shows a thickness ratio of approximately 57% between the first cylindrical part 31 and the spring part 33, for example, with a thickness W1 of approximately 1.1 mm for the first cylindrical part 31 and a thickness W2 of approximately 0.7 mm for the spring part 33.

[0051] Graph H shows a case where the thickness ratio of the first cylindrical part 31 to the spring part 33 is approximately 64%, for example, the thickness W1 of the first cylindrical part 31 = approximately 1.15 mm and the thickness W2 of the spring part 33 = approximately 0.7 mm. Graph I shows a case where the thickness ratio of the first cylindrical part 31 to the spring part 33 is approximately 71%, for example, the thickness W1 of the first cylindrical part 31 = approximately 1.2 mm and the thickness W2 of the spring part 33 = approximately 0.7 mm. Note that the thickness ratio of the first cylindrical part 31 to the spring part 33 is expressed as a percentage of the value obtained by subtracting 1 from the ratio of the thickness W1 of the first cylindrical part 31 to the thickness W2 of the spring part 33.

[0052] As shown in graphs C to I in Figure 9, the rigidity of the internal vibrator 3 increases when the axial length H2 of the first cylindrical portion 31 is shorter than the axial length H3 of the spring portion 33, and the vibration stress applied to the outermost lens 1 decreases. Also, the rigidity of the internal vibrator 3 increases when the thickness W1 of the first cylindrical portion 31 is thicker than the thickness W2 of the spring portion 33, and the vibration stress applied to the outermost lens 1 decreases.

[0053] Furthermore, as can be seen from Figure 9, graphs E to I satisfy the condition that the vibration stress applied to the outermost lens 1 is approximately 20 MPa or less. In other words, if the thickness ratio of the first cylindrical part 31 and the spring part 33 of the internal vibrating body 3 is approximately 29% or more, the risk of damage to the outermost lens 1 is low even if the displacement of the outer part is larger than the displacement of the inner part.

[0054] Furthermore, if the thickness ratio of the first cylindrical portion 31 to the spring portion 33 of the internal vibrator 3 is approximately 29% (Graph E), the axial length ratio of the first cylindrical portion 31 to the spring portion 33 is approximately -77% or less, and the vibration stress applied to the outermost lens 1 is approximately 20 MPa or less. On the other hand, if the thickness ratio of the first cylindrical portion 31 to the spring portion 33 of the internal vibrator 3 is approximately 71% (Graph I), the axial length ratio of the first cylindrical portion 31 to the spring portion 33 is approximately -50% or less, and the vibration stress applied to the outermost lens 1 is approximately 20 MPa or less.

[0055] Next, the structural features of the vibration device 10 will be described. In Figure 2, it was explained that a structural feature of the vibration device 10 is that the axial length H2 of the first cylindrical portion 31 is shorter than the axial length H1 of the holding portion 2a of the external vibrator 2. However, when considering the positional relationship between the internal vibrator 3 and the holding portion 2a of the external vibrator 2, the vibration device 10 has a structural feature in which the internal vibrator 3 is positioned relative to the external vibrator 2 such that, when viewed from the side of the holding portion 2a in a plan view, at least a part of the spring portion 33 of the internal vibrator 3 overlaps with the holding portion 2a.

[0056] Figure 10 is a half-cross-sectional view illustrating the positional relationship between the internal vibrator 3 and the holding portion 2a of the external vibrator 2. As shown in Figure 10, when the vibration device 10 is viewed in plan from the direction of arrow V (direction from the side of the holding portion 2a), at least a portion P of the spring portion 33 of the internal vibrator 3 overlaps with the holding portion 2a. In other words, the vibration device 10 has a structural feature in which the internal vibrator 3 is positioned relative to the external vibrator 2 such that at least a portion of the spring portion 33 of the internal vibrator 3 overlaps with the holding portion 2a.

[0057] (Modification) As shown in Figure 1, the vibration device 10 employs an internal vibrator 3 in which the cross-sectional shape of the spring portion 33 is S-shaped. However, the internal vibrator 3 is not limited to a structure in which the cross-sectional shape of the spring portion 33 is S-shaped. The internal vibrator 3 may have other shapes in the cross-sectional shape of the spring portion 33, such as a shape in which multiple S shapes are connected, or a curved shape which is half of an S shape.

[0058] The internal vibrator 3 may have any structure as long as the percentage obtained by subtracting 1 from the ratio of the displacement of the outer second part to the displacement of the inner first part at the portion in contact with the outermost lens 1 is approximately 2.5% or less. For example, the internal vibrator may have a structure in which multiple grooves in the shape of a Y turned on its side (tuning fork shape) are arranged in the circumferential direction at equal intervals.

[0059] Furthermore, the imaging device according to the above-described embodiment may include a camera, LiDAR, radar, etc. Furthermore, multiple imaging devices may be arranged side by side. In addition, the imaging device according to the above-described embodiment is not limited to an imaging device installed in a vehicle, but can be similarly applied to any imaging device that comprises an optical device and an image sensor arranged so that the translucent material is in the field of view direction, and where it is necessary to remove foreign matter from the translucent material.

[0060] (Aspects) (1) The vibration device according to the present disclosure comprises: a light-transmitting body that transmits light of a predetermined wavelength; an internal vibrating body that is in contact with the light-transmitting body and vibrates the light-transmitting body; a piezoelectric element provided on the internal vibrating body; and an external vibrating body that covers the internal vibrating body and has a cylindrical shape for holding the light-transmitting body, wherein the internal vibrating body, in the portion in contact with the light-transmitting body, has a percentage of 2.5% or less of the value obtained by subtracting 1 from the ratio of the displacement of the outer second part to the displacement of the inner first part.

[0061] As a result, the vibration device according to this disclosure can suppress the application of large localized vibration stress to the light-transmitting material, thereby reducing damage to the light-transmitting material.

[0062] (2) In the vibration device described in (1), the displacement of the first part of the internal vibrating body is the same as the displacement of the second part.

[0063] (3) In the vibration device described in (1) or (2), the internal vibrator is cylindrical in shape and includes a first cylindrical portion in contact with a light-transmitting body, a second cylindrical portion on which a piezoelectric element is provided, and a spring portion connecting the first cylindrical portion and the second cylindrical portion and having a curved cross-sectional shape, wherein the axial length of the first cylindrical portion is shorter than the axial length of the holding portion of the external vibrator.

[0064] (4) In the vibrating device described in (3), the percentage of the value obtained by subtracting 1 from the ratio of the axial length of the first cylindrical part to the axial length of the holding part is -63% or less.

[0065] (5) In the vibration device described in (3) or (4), the outer diameter of the spring portion of the internal vibrator is smaller than the inner diameter of the holding portion of the external vibrator.

[0066] (6) In the vibration device described in any one of items (3) to (5), the internal vibrating body has an axial length of the first cylindrical portion that is shorter than the axial length of the spring portion, and a thickness of the first cylindrical portion that is thicker than the thickness of the spring portion.

[0067] (7) In the vibration device described in any one of items (3) to (6), the internal vibrating body has a percentage of -50% or less of the value obtained by subtracting 1 from the ratio of the axial length of the first cylindrical part to the axial length of the spring part, and a percentage of 29% or more of the value obtained by subtracting 1 from the ratio of the thickness of the first cylindrical part to the thickness of the spring part.

[0068] (8) In the vibration device described in any one of items (3) to (7), the internal vibrator is positioned relative to the external vibrator such that, when viewed from the side of the holding portion of the external vibrator, at least a part of the spring portion of the internal vibrator overlaps with the holding portion.

[0069] (9) In the vibration device described in any one of items (3) to (8), the spring portion has an S-shaped cross-section.

[0070] (10) The imaging device relating to this disclosure comprises a vibrating device as described in any one of paragraphs (1) to (9), and an imaging sensor arranged such that the light-transmitting material is in the direction of the field of view.

[0071] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

[0072] 1 Outermost lens, 2 External vibrator, 2a Holding part, 2b, 31a End part, 2c Housing part, 2d Connection part, 2e Weight, 3 Internal vibrator, 4 Inner lens, 5 Piezoelectric element, 6 Image sensor, 7 Drive circuit, 8 Bracket, 10 Vibration device, 20 Sensor device, 21 Retainer, 31 First cylindrical part, 32 Second cylindrical part, 33 Spring part, 41 Holding plate, 51, 71 Wiring, 61 Circuit board, 81 Bottom plate, 100 Imaging device.

Claims

1. A vibrating device comprising: a light-transmitting body that transmits light of a predetermined wavelength; an internal vibrating body that is in contact with the light-transmitting body and vibrates the light-transmitting body; a piezoelectric element provided on the internal vibrating body; and an external vibrating body that covers the internal vibrating body and has a cylindrical shape for holding the light-transmitting body, wherein the internal vibrating body, in the portion in contact with the light-transmitting body, has a percentage of 2.5% or less of the value obtained by subtracting 1 from the ratio of the displacement of the outer second part to the displacement of the inner first part.

2. The vibration device according to claim 1, wherein the displacement of the first portion of the internal vibrating body is the same as the displacement of the second portion.

3. The vibration device according to claim 1 or 2, wherein the internal vibrator is cylindrical in shape and includes a first cylindrical portion in contact with the light-transmitting body, a second cylindrical portion on which the piezoelectric element is provided, and a spring portion connecting the first cylindrical portion and the second cylindrical portion and having a curved cross-sectional shape, the axial length of the first cylindrical portion is shorter than the axial length of the holding portion of the external vibrator.

4. The vibration device according to claim 3, wherein the percentage of the value obtained by subtracting 1 from the ratio of the axial length of the first cylindrical portion to the axial length of the holding portion is -63% or less.

5. The vibration device according to claim 3 or 4, wherein the outer diameter of the spring portion of the internal vibrator is smaller than the inner diameter of the holding portion of the external vibrator.

6. The vibration device according to any one of claims 3 to 5, wherein the internal vibrating body has an axial length of the first cylindrical portion shorter than the axial length of the spring portion and a thickness of the first cylindrical portion greater than the thickness of the spring portion.

7. The vibration device according to any one of claims 3 to 6, wherein the internal vibrating body has a percentage of -50% or less of the value obtained by subtracting 1 from the ratio of the axial length of the first cylindrical portion to the axial length of the spring portion, and a percentage of 29% or more of the value obtained by subtracting 1 from the ratio of the thickness of the first cylindrical portion to the thickness of the spring portion.

8. The vibration device according to any one of claims 3 to 7, wherein, when viewed from the side of the holding portion of the external vibrator, the internal vibrator is positioned relative to the external vibrator such that at least a portion of the spring portion of the internal vibrator overlaps with the holding portion.

9. The vibration device according to any one of claims 3 to 8, wherein the spring portion has an S-shaped cross-section.

10. An imaging device comprising a vibrating device according to any one of claims 1 to 9, and an imaging sensor arranged such that the light-transmitting body is in the direction of the field of view.

Images