Sound wave devices, double feed detection devices, and electronic equipment

Abstract

To provide an acoustic device that can suppress the adhesion of foreign matter to the acoustic element and that does not easily attenuate the transmitted and received sound waves, as well as a double-feed detection device and electronic equipment equipped with such an acoustic device. [Solution] An acoustic wave device comprising: a substrate having a hollow portion; an acoustic element provided at a position corresponding to the hollow portion of the substrate and generating sound waves; and a protective member provided on the surface of the substrate opposite to the surface on which the acoustic element is provided and closing the hollow portion, wherein the protective member has front and back sides to each other, a first surface facing the hollow portion and a second surface located on the opposite side of the hollow portion, and a void opening to the first surface and extending toward the second surface, the width of the void being smaller than the width of the acoustic element, and the void not penetrating the protective member.

Description

Technical Field

[0001] The present invention relates to a sound wave device, a double feed detection device, and an electronic device.

Background Art

[0002] Patent Document 1 discloses an image scanner as an electronic device including a sensor unit having an ultrasonic device that transmits ultrasonic waves, and an attachment target to which the sensor unit is attached.

[0003] The sensor unit includes a pair of ultrasonic devices. Ultrasonic waves are transmitted from one ultrasonic device, and the ultrasonic waves transmitted through the paper are received by the other ultrasonic device. Thereby, the sensor unit can detect double feeding of the paper according to the sound pressure of the received ultrasonic waves.

[0004] In addition, the sensor unit described in Patent Document 1 includes a mesh-shaped protective member through which ultrasonic waves transmitted from the ultrasonic device pass. By providing the protective member, it is possible to prevent foreign substances such as paper dust falling off from the paper from entering the inside of the ultrasonic device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the sensor unit of Patent Document 1 has a problem that ultrasonic waves transmitted through the protective member are attenuated. When the ultrasonic waves are attenuated, the accuracy of detecting double feeding of the paper decreases. Also, the same problem exists in devices using sound waves other than ultrasonic waves.

[0007] Therefore, there is a need for an acoustic device that can suppress the intrusion of foreign matter into the interior and also does not easily attenuate the sound waves being transmitted and received. [Means for solving the problem]

[0008] The sound wave device according to an application example of the present invention is: A substrate having a hollow portion, A sound wave element is provided at a position corresponding to the hollow portion of the substrate and generates sound waves, A protective member is provided on the surface of the substrate opposite to the surface on which the sound wave element is provided, and which closes the hollow portion. Equipped with, The protective member has a front-and-back relationship with respect to each other, and has a first surface facing the hollow portion and a second surface located on the opposite side of the hollow portion, as well as a void opening in the first surface and extending toward the second surface. The width of the aforementioned void is smaller than the width of the sound wave element. The aforementioned void does not penetrate the protective member.

[0009] The double-feed detection device according to an application example of the present invention is: The present invention comprises a sound wave device according to an application example, a transmitting unit that transmits the ultrasonic waves, The present invention comprises a sound wave device according to an application example, a receiving unit that receives the ultrasonic waves, Equipped with, The transmitting unit and the receiving unit are arranged on either side of the medium transport path. The transmitting unit transmits the ultrasonic waves, the receiving unit receives the ultrasonic waves that have passed through the medium, and the receiving unit detects the double feeding of the medium based on the signal strength of the received signal.

[0010] The electronic device according to an example of the application of the present invention is The present invention includes an acoustic device according to an example of its application. [Brief explanation of the drawing]

[0011] [Figure 1] This is an external view showing the schematic configuration of an image scanner as an electronic device according to the first embodiment. [Figure 2] It is a side sectional view showing an outline of a conveyance unit of an image scanner shown in FIG. 1. [Figure 3] It is a sectional view showing a schematic configuration of an ultrasonic sensor shown in FIG. 2. [Figure 4] It is a sectional view showing a configuration of a sound wave device of FIG. 3. [Figure 5] It is a partially enlarged view of FIG. 4. [Figure 6] It is a plan view of the sound wave device shown in FIG. 4. [Figure 7] It is a figure showing a result of simulating a state in which ultrasonic waves propagate in a hollow portion of a sound wave device and a space S located in the Z direction thereof. [Figure 8] It is a figure showing a result of simulating a state in which ultrasonic waves propagate in a hollow portion of a sound wave device and a space S located in the Z direction thereof. [Figure 9] It is a figure showing a result of simulating a state in which ultrasonic waves propagate in a hollow portion of a sound wave device and a space S located in the Z direction thereof. [Figure 10] It is a sectional view showing a modified example of the sound wave device of FIG. 4. [Figure 11] It is a plan view of the sound wave device shown in FIG. 10. [Figure 12] It is a sectional view showing a modified example of the sound wave device of FIG. 4. [Figure 13] It is a plan view of the sound wave device shown in FIG. 12. [Figure 14] It is a sectional view showing a modified example of the sound wave device of FIG. 12. [Figure 15] It is an external view showing a schematic configuration of a wireless earphone as an electronic device according to the second embodiment. [Figure 16] It is a partially enlarged sectional view of FIG. 15. [Figure 17] It is an external view of the wireless earphone shown in FIG. 15 when viewed from an angle different from FIG. 15.

Embodiments for Carrying Out the Invention

[0012] The sonic device, double feed detection device, and electronic equipment according to the present invention will be described in detail below based on the embodiments shown in the accompanying drawings.

[0013] 1. First Embodiment First, the first embodiment will be described.

[0014] 1.1. Image Scanner First, an image scanner will be described as an example of an electronic device according to the first embodiment.

[0015] Figure 1 is an external view showing the schematic configuration of an image scanner 10 as an electronic device according to the first embodiment. Figure 2 is a schematic side cross-sectional view showing the transport section of the image scanner 10 shown in Figure 1. Note that Figure 2 is a side cross-sectional view of the image scanner 10 when viewed from the main scanning direction (X direction) which is perpendicular to the transport direction (Y direction). In Figure 2, the Y direction is represented by an arrow, with the tip of the arrow being the +Y side and the base of the arrow being the -Y side.

[0016] 1.1.1. Schematic configuration of image scanner 10 The image scanner 10 shown in Figure 1 comprises a main unit 11 and a paper support 12. Inside the main unit 11, as shown in Figure 2, there is a transport unit 13 for transporting paper P, a scan unit 14 for reading the image of the transported paper P, an ultrasonic sensor 15 for detecting double feeding of paper P, and a control unit 16 for controlling the operation of the image scanner 10. In this embodiment, paper P is given as an example of the object for which the ultrasonic sensor 15 detects double feeding, but the object is not limited to this. Examples of objects include film, fabric, various media, etc.

[0017] As shown in Figures 1 and 2, the main body of the device 11 is provided with a paper feed port 11A at the connection point with the paper support 12. Paper P placed on the paper support 12 is fed one sheet at a time to the paper feed port 11A. The fed paper P is transported by the transport unit 13 along a predetermined transport path 130 inside the main body of the device 11. Then, at a reading position during transport, the scan unit 14 reads the image, and the paper is discharged from the discharge port 11B which opens at the lower front of the main body of the device 11.

[0018] 1.1.2. Configuration of the transport unit 13 The transport unit 13 shown in Figure 2 transports multiple sheets of paper P set in the paper support 12 one sheet at a time in the transport direction (Y direction). That is, the transport unit 13 feeds the paper P sent from the feed port 11A into the main body of the device 11, and then transports the fed paper P along a predetermined transport path 130.

[0019] More specifically, the transport unit 13 includes a first feed roller pair 131 positioned upstream (-Y side) in the Y direction of the transport path 130, and a second feed roller pair 132 positioned downstream (+Y side) of the first feed roller pair 131 in the Y direction. Furthermore, the transport unit 13 includes a first transport roller pair 133 positioned on the -Y side with the paper reading position P in between, and a second transport roller pair 134 positioned on the +Y side.

[0020] The first feed roller pair 131 consists of a first drive roller 131A and a first driven roller 131B. Similarly, the second feed roller pair 132 consists of a second drive roller 132A and a second driven roller 132B. The first transport roller pair 133 consists of a third drive roller 133A and a third driven roller 133B. Similarly, the second transport roller pair 134 consists of a fourth drive roller 134A and a fourth driven roller 134B. The driven rollers 131B to 134B are driven by the rotation of their respective pairs of drive rollers 131A to 134A.

[0021] Each drive roller 131A to 134A, which constitutes each roller pair 131 to 134, is rotated by the power of the transport motor 135, which is their power source. The operation of the transport motor 135 is controlled by the control unit 16, which drives each drive roller 131A to 134A.

[0022] Furthermore, the second driven roller 132B, which constitutes the second feed roller pair 132, is a retard roller, and the coefficient of friction of its outer surface with respect to the paper P is greater than the coefficient of friction of the outer surface of the second driven roller 132A with respect to the paper P. For this reason, the second feed roller pair 132 functions as a separation mechanism that separates the paper P one sheet at a time and feeds them to the +Y side. Consequently, the rotation of the first feed roller pair 131 causes the multiple sheets of paper P loaded on the paper support 12 to be fed one sheet at a time from the feed opening 11A into the device body 11, for example, starting from the top sheet, and then separated one sheet at a time by the rotation of the second feed roller pair 132 and fed to the +Y side.

[0023] 1.1.3. Configuration of the scanning unit 14 As shown in Figure 2, a scanning unit 14 is provided between the first pair of transport rollers 133 and the second pair of transport rollers 134 of the transport path 130.

[0024] The scanning unit 14 consists of a first scanning unit 14A and a second scanning unit 14B, which are provided on both sides of the transport path 130. This scanning unit 14 consists of a light source 141 capable of illuminating the paper P while it is being transported, and an image sensor 142 extending in the main scanning direction (X direction). In the normal reading mode, which reads the surface of the paper P, the first scanning unit 14A performs the reading operation, and in the double-sided reading mode, which reads both the front and back surfaces of the paper P, both the first scanning unit 14A and the second scanning unit 14B perform the reading operation. The first scanning unit 14A and the second scanning unit 14B each have a light source 141 and an image sensor 142. These are connected to the control unit 16, and the control unit 16 controls the scanning process to read the image of the paper P.

[0025] 1.1.4. Configuration of the ultrasonic sensor 15 The ultrasonic sensor 15 is located in the transport path 130 between the second feed roller pair 132 and the first transport roller pair 133. This ultrasonic sensor 15 is a double feed sensor (double feed detection device according to the first embodiment) and detects double feeding of paper P being transported by the transport unit 13 using ultrasonic waves.

[0026] Figure 3 is a cross-sectional view showing the schematic configuration of the ultrasonic sensor 15 shown in Figure 2. Note that Figure 3 shows a cross-section of the ultrasonic sensor 15 as viewed from the X direction.

[0027] The ultrasonic sensor 15 comprises a transmitting unit 151 and a receiving unit 152. The transmitting unit 151 transmits ultrasonic waves, which are high-frequency sound waves. The receiving unit 152 receives the ultrasonic waves transmitted from the transmitting unit 151.

[0028] As shown in Figure 3, the transmitting unit 151 and the receiving unit 152 are positioned opposite each other on the axis of the sensor central axis 15C, with the transport path 130 through which the paper P is transported in between. Alternatively, the transmitting unit 151 and the receiving unit 152 may be positioned in the reversed configuration shown in Figure 3.

[0029] In this ultrasonic sensor 15, the transmitting unit 151 transmits ultrasonic waves to the paper P being transported along the transport path 130 by the transport unit 13. The ultrasonic waves transmitted from the transmitting unit 151 are incident on the paper P, and the ultrasonic waves that have passed through the paper P are received by the receiving unit 152. When the ultrasonic waves are received by the receiving unit 152, a received signal corresponding to the sound pressure of the received ultrasonic waves is output from the receiving unit 152, and a double feed of the paper P is detected based on the signal strength of this received signal.

[0030] As shown in Figure 3, the sensor central axis 15C is an axis passing through the center of the transmitting unit 151 and the center of the receiving unit 152, and is the direction of transmission and reception of ultrasonic waves. In this embodiment, the sensor central axis 15C is inclined at an angle θ with respect to the normal to the surface of the paper P being transported along the transport path 130. By inclining the sensor central axis 15C with respect to the normal to the surface of the paper P, the reception of unwanted ultrasonic components such as multiple reflections of ultrasonic waves can be reduced, enabling highly accurate double-feed detection.

[0031] The transmitting unit 151 and the receiving unit 152 each include a sound wave device 1 according to the first embodiment. The configuration of the sound wave device 1 provided in the transmitting unit 151 will be described below. Note that the following description is also applicable to the sound wave device 1 provided in the receiving unit 152, so the description of the configuration of the sound wave device 1 provided in the receiving unit 152 will be omitted. The sound wave device 1 is a device that transmits and receives sound waves, and sound waves include, for example, ultrasound and audible sound waves. In the ultrasonic sensor 15, ultrasound is mainly used, so in the following description, the sound wave device 1 that transmits and receives sound waves, particularly in the ultrasonic range, will be used as an example. By using ultrasound, for example, a sound wave device 1 capable of measuring distance and detecting objects can be realized. Note that the following description is also applicable to sound wave devices that transmit and receive audible sound waves.

[0032] Figure 4 is a cross-sectional view showing the configuration of the acoustic device 1 shown in Figure 3. Note that Figure 4 shows a cross-section including the sensor central axis 15C shown in Figure 3. Figure 5 is a partially enlarged view of Figure 4. Figure 6 is a plan view of the acoustic device 1 shown in Figure 4. Note that Figure 6 shows the plan view as seen from the paper P side shown in Figure 3.

[0033] The acoustic wave device 1 shown in Figure 4 comprises a base material 111, an ultrasonic element 112 (acoustic wave element), a protective member 113, and a sealing member 114. The acoustic wave device 1 transmits ultrasonic waves in the Z direction indicated by the arrow in Figure 4. The Z direction is parallel to the sensor central axis 15C.

[0034] 1.1.4.1. Base material The base material 111 has a hollow portion 182 penetrating along the Z direction. Examples of the constituent material of the base material 111 include silicon-based materials such as Si; oxide-based materials such as SiOx (0 < x < 3) and ZrOx (0 < x < 3); resin-based materials such as permanent resists, and the like. Among these, silicon-based materials are preferably used from the viewpoints of ease of manufacturing and the like, and Si is more preferably used.

[0035] The length L111 of the hollow portion 182 in the Z direction is set according to the frequency of the ultrasonic wave transmitted by the acoustic wave device 1 and is not particularly limited, but is preferably 30 μm or more and 500 μm or less, and more preferably 50 μm or more and 200 μm or less.

[0036] The width W111 of the hollow portion 182 in the direction orthogonal to the Z direction is set according to the frequency of the ultrasonic wave transmitted by the acoustic wave device 1 and is not particularly limited, but is preferably 50 μm or more and 3000 μm or less, and more preferably 100 μm or more and 500 μm or less.

[0037] The ultrasonic element 112 is disposed on the side opposite to the Z direction of the base material 111. As shown in FIG. 4, the ultrasonic element 112 is provided at a position corresponding to the hollow portion 182 of the base material 111. That is, the ultrasonic element 112 closes the end opposite to the Z direction of the hollow portion 182.

[0038] As shown in FIG. 4, the ultrasonic element 112 includes a diaphragm 122 and a piezoelectric element 124 provided on the surface of the diaphragm 122 opposite to the Z direction. Note that the fact that the ultrasonic element 112 is provided at a position corresponding to the hollow portion 182 means that the piezoelectric element 124 overlaps so as to be included in the hollow portion 182 when viewed from the Z direction.

[0039] The diaphragm 122 is sandwiched between the base material 111 and the sealing member 114. Examples of the constituent material of the diaphragm 122 include silicon-based materials such as Si; oxide-based materials such as SiOx (0 < x < 3) and ZrOx (0 < x < 3); metal-based materials; resin-based materials such as permanent resist, etc. Further, the diaphragm 122 may be a laminate in which two or more layers of different constituent materials are laminated.

[0040] As shown in FIG. 5, the piezoelectric element 124 includes a first electrode 126, a piezoelectric film 127, and a second electrode 128, which are laminated in this order from the diaphragm 122 side. In the piezoelectric element 124, when a pulse wave voltage of a predetermined frequency is applied between the first electrode 126 and the second electrode 128, the piezoelectric film 127 expands and contracts. As a result, the diaphragm 122 vibrates at a frequency corresponding to the width W111 of the hollow portion 182 of the base material 111, etc., and ultrasonic waves are generated from the hollow portion 182 of the base material 111 in the Z direction. Therefore, the base material 111 and the ultrasonic element 112 function as an ultrasonic transducer. Further, since the piezoelectric element 124 as described above can be formed by a film-forming process, it is easy to manufacture and contributes to cost reduction of the acoustic wave device 1.

[0041] The width W112 of the ultrasonic element 112 in the direction orthogonal to the Z direction is not particularly limited, but is preferably set smaller than the width W111. Thereby, ultrasonic waves can be efficiently generated from the ultrasonic transducer.

[0042] The protective member 113 shown in FIG. 4 is arranged in the Z direction of the base material 111. That is, the protective member 113 is provided on the surface of the base material 111 opposite to the surface on which the ultrasonic element 112 is provided. And the protective member 113 closes the Z-direction end of the hollow portion 182. The ultrasonic waves generated from the ultrasonic transducer pass through the protective member 113 and are transmitted in the Z direction.

[0043] The protective member 113 is plate-shaped and has a first surface 165 and a second surface 166 that are on opposite sides of each other, as well as a void 164 that opens into the first surface 165 and extends toward the second surface 166. The first surface 165 is the surface facing the hollow portion 182 of the base material 111. The second surface 166 is the transmitting surface to which ultrasonic waves that have passed through the protective member 113 are transmitted.

[0044] The void 164 is a hole that does not penetrate the protective member 113. Specifically, the void 164 opens to the first surface 165 shown in Figure 4, but does not open to the second surface 166.

[0045] Furthermore, the width of the void 164 is defined as W164. The width W164 is the maximum width of the void 164 in the direction perpendicular to the Z direction. This width W164 is smaller than the width W112 of the ultrasonic element 112.

[0046] By providing a void 164 with this shape in the protective member 113, the ultrasonic waves generated by the ultrasonic transducer can efficiently pass through the protective member 113 and be transmitted in the Z direction, realizing an ultrasonic wave device 1. In other words, since the protective member 113 prevents internal exposure, an ultrasonic wave device 1 can be realized that transmits ultrasonic waves generated by the ultrasonic transducer while suppressing attenuation in the protective member 113. Furthermore, it is possible to receive ultrasonic waves while suppressing attenuation in the protective member 113, realizing an ultrasonic wave device 1 with high ultrasonic reception sensitivity. As a result, an ultrasonic sensor 15 with high accuracy in detecting double transmission can be realized.

[0047] Furthermore, in this ultrasonic device 1, since the ultrasonic transmitting surface is the second surface 166 of the protective member 113, the substrate 111 and the ultrasonic element 112 are not exposed. Therefore, it is possible to suppress the entry of paper dust and other debris that have fallen from the paper P into the interior of the ultrasonic device 1. This also prevents foreign matter from adhering to the hollow portion 182 and the ultrasonic element 112. As a result, it is possible to suppress ultrasonic attenuation due to foreign matter and deterioration of the ultrasonic element 112 due to moisture, etc. As a result, a highly reliable ultrasonic sensor 15 can be realized.

[0048] Furthermore, as shown in Figure 6, the protective member 113 does not have a void 164 opening to the second surface 166. Therefore, the ultrasonic transmitting surface of the transmitting unit 151 and the ultrasonic receiving surface of the receiving unit 152 can be made flat. As a result, when cleaning the ultrasonic transmitting surface with a cleaning solution, the ability to wipe away foreign matter is improved. Thus, an ultrasonic sensor 15 with excellent maintainability can be realized.

[0049] While the sound wave device 1 may be positioned so that the second surface 166 is horizontal, it is preferable that the second surface 166 be positioned at an angle to the horizontal plane. This makes it easier for foreign matter or other particles that adhere to the second surface 166 to fall off naturally. This tendency is particularly pronounced when the second surface 166 is flat.

[0050] The effects described above are thought to be obtained by the pores 164 in the protective member 113. Specifically, the optimized width W164 of the pores 164 and the fact that the pores 164 do not open to the second surface 166 are thought to contribute to the unique transmission of ultrasound. Structures that produce such transmission phenomena are also called acoustic metamaterials. In the protective member 113 shown in Figure 4, the air inside the pores 164 resonates according to the frequency of the sound waves, and as a result, the thin film located in the Z direction of the pores 164 (the part between the pores 164 and the second surface 166 shown in Figure 4) vibrates significantly, which is thought to cause the sound waves to be uniquely transmitted.

[0051] Furthermore, when the sound wave device 1 is used in the receiving unit 152, improvements in ultrasonic reception sensitivity, reliability, and maintainability can be achieved.

[0052] Figures 7 to 9 show the results of a simulation of how ultrasound propagates in the hollow portion 182 of the sound wave device 1 and the space S located in the Z direction. The striped patterns shown in Figures 7 to 9 represent changes in pressure due to ultrasound. In other words, ultrasound propagates in the areas where the striped patterns are drawn, and does not propagate in the areas where the patterns are not drawn.

[0053] Figure 7 shows the result of simulating a model in which the protective member 113 does not exist between the hollow portion 182 and the space S. In the simulation shown in Figure 7, it is shown that the ultrasonic wave generated in the hollow portion 182 is transmitted to the space S almost without attenuation.

[0054] Figure 8 shows the result of simulating a model in which the protective member 113 having a through-hole is provided between the hollow portion 182 and the space S. That is, in the model shown in Figure 8, instead of the hole 164 that does not open to the second surface 166 as shown in Figure 4, a through-hole penetrating the protective member 113 is provided. The width of the through-hole is smaller than the width of the ultrasonic element not shown. In the simulation shown in Figure 8, it is shown that the ultrasonic wave generated in the hollow portion 182 hardly passes through the protective member 113.

[0055] Figure 9 shows the result of simulating a model in which the protective member 113 having a non-penetrating hole is provided between the hollow portion 182 and the space S. That is, the model shown in Figure 9 is a model simulating the acoustic wave device 1 shown in Figure 4. The width of the non-penetrating hole is smaller than the width of the ultrasonic element not shown. In the simulation shown in Figure 9, it is shown that the ultrasonic wave generated in the hollow portion 182 is transmitted to the space S.

[0056] From the above simulation results, it is confirmed that the protective member 113 having a width W164 smaller than the width W112 of the ultrasonic element 112 and formed so as not to penetrate can specifically transmit ultrasonic waves.

[0057] Examples of the constituent material of the protective member 113 include silicon-based materials such as Si; oxide-based materials such as SiOx (0 < x < 3) and ZrOx (0 < x < 3); resin-based materials such as permanent resist. Further, the constituent material of the protective member 113 may be a composite material using two or more of these.

[0058] The protective member 113 may be a single layer or a laminate. The protective member 113 shown in Figure 4 is an example composed of a laminate. The protective member 113 shown in Figure 4 is composed of a laminate in which a first layer 161, a second layer 162, and a third layer 163 are laminated in this order from the base material 111 side. The void 164 penetrates the first layer 161 but does not extend to the second layer 162 and the third layer 163. In other words, the second layer 162 and the third layer 163 function as a cover for the void 164. In Figure 4, the portion of the second layer 162 and the third layer 163 located in the Z direction of the void 164 is designated as cap C.

[0059] In Figure 4, the thickness of cap C is denoted as t. In the protective member 113, the width W164 of the void 164 and the thickness t of cap C should be optimized according to the frequency of the ultrasonic waves to be transmitted. This allows for efficient transmission of ultrasonic waves of the desired frequency.

[0060] As a general trend, if the width W164 of the void 164 is the same, the frequency of ultrasonic waves passing through the protective member 113 can be lowered by reducing the thickness t of the cap C or by decreasing the elastic modulus of the cap C. On the other hand, if the thickness t and elastic modulus of the cap C are the same, the frequency of ultrasonic waves passing through the protective member 113 can be lowered by increasing the width W164 of the void 164. Based on these trends, the optimal width W164 and thickness t can be found. Furthermore, a protective member 113 that can transmit not only ultrasonic waves but also audible sound waves can be realized.

[0061] For example, if the constituent material of cap C is Si and the thickness t of cap C is 1.5 μm, and the frequency of the ultrasonic waves transmitted through the protective member 113 is y [kHz], and the width W164 of the void 164 is x [μm], then the distance between the two is y = (2 × 10 7 )x -1.987 The following relationship holds true. In this case, for example, in order to transmit ultrasound with a frequency of 400 kHz, the width W164 of the pore 164 should be approximately 232 μm.

[0062] Furthermore, if the constituent material of cap C is changed to SiO2, then y = (2 × 10 7 )x -1.981 The following relationship holds. Furthermore, if the constituent material of cap C is changed to resin, then y = 9571.9x -0.965 The following relationship holds true.

[0063] The thickness t of the cap C is preferably 0.5 μm to 50 μm, and more preferably 1 μm to 20 μm. If the thickness t of the cap C is within the above range, a protective member 113 can be realized with good transmittance in the ultrasonic range, particularly in ultrasonic frequencies of about 40 kHz to 1 MHz, which are suitable for detecting distance and double feed.

[0064] The width W164 of the void 164 is preferably smaller than the wavelength of the ultrasound generated by the ultrasonic transducer (substrate 111 and ultrasonic element 112). With this configuration, the protective member 113 becomes an acoustic metamaterial, and a higher transmittance to the protective member 113 than the ultrasonic transmittance inherent to the constituent material of the cap C can be imparted to the protective member 113.

[0065] The width W164 of the void 164 is preferably 50% or less of the width W111 of the hollow portion 182, and more preferably 1% to 30%. If the thickness t of the cap C is within the above range, a protective member 113 can be realized with good transmittance in the ultrasonic range, particularly with good transmittance of ultrasonic waves at frequencies of about 40 kHz to 1 MHz, which are suitable for detecting distance and double feed.

[0066] Furthermore, the width W164 of the pore 164 is preferably 5 μm or more and 1000 μm or less, more preferably 30 μm or less and 800 μm or less, and even more preferably 50 μm or more and 600 μm or less.

[0067] The length L164 of the void 164 in the Z direction is preferably 20% to 99% of the thickness T of the protective member 113, and more preferably 50% to 95% of the thickness T. If the length L164 of the void 164 is within the above range, a protective member 113 can be realized with good transmittance in the ultrasonic region, particularly in ultrasonic frequencies of about 40 kHz to 1 MHz, which are suitable for detecting distance and double feed.

[0068] Furthermore, the length L164 of the pore 164 is preferably 5 μm or more and 200 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0069] The constituent materials of the first layer 161, the second layer 162, and the third layer 163 are not particularly limited and may be the same or different from each other. In the latter case, it is preferable that the constituent material of the second layer 162 be different from that of the first layer 161. This makes it possible to have different processing rates in mechanical and chemical processing for the first layer 161 and the second layer 162. As a result, the processing to form voids 164 only in the first layer 161 can be performed efficiently and easily. In other words, when forming voids 164, the second layer 162 and the third layer 163 can be left with almost no processing, so the thickness t of the cap C can be precisely controlled. This makes it possible to realize an acoustic device 1 in which the frequency of ultrasonic waves passing through the protective member 113 is precisely controlled.

[0070] For the three-layer laminate described above, a silicon-on-insulator (SOI) substrate is preferably used. The SOI substrate is a substrate consisting of a first layer 161 made of Si, a second layer 162 made of SiO2, and a third layer 163 made of Si. SOI substrates are widely available and easy to obtain, and their quality is stable. They are also materials that can be precisely processed by semiconductor processes. In particular, Si is easy to process by wet etching, and the processing rate of SiO2 by wet etching is lower than that of Si. Therefore, the first layer 161 can be processed with high precision to form voids 164 with high dimensional accuracy, while a protective member 113 with a precisely controlled thickness t of the cap C can be manufactured inexpensively depending on the thickness of the second layer 162. As a result, it is possible to realize an acoustic wave device 1 in which variations in the bandwidth of transmitted ultrasonic waves are suppressed, or an acoustic wave device 1 in which variations in the bandwidth of received ultrasonic waves are suppressed.

[0071] Therefore, it is preferable that the void 164 is an etched hole. This allows the void 164 to be formed accurately in a short time. As a result, the width W164 and length L164 of the void 164 are highly precise, and an acoustic wave device 1 in which the frequency of transmitted ultrasonic waves is strictly controlled can be easily realized.

[0072] The following is an example of a method for forming voids 164 by wet etching. First, a resist film having openings corresponding to the shape of the voids 164 to be formed is formed on the surface of the first layer 161 of the SOI substrate.

[0073] Next, an etching solution is supplied to the resist film. This causes the first layer 161 to come into contact with the etching solution at the opening, and the first layer 161 is etched in the Z direction. As a result, an etched hole with a shape corresponding to the opening can be formed. However, as the etched hole extends and reaches the second layer 162, the processing rate decreases, and further extension is suppressed. As a result, a void 164 is obtained that penetrates the first layer 161 but does not extend to the second layer 162 or the third layer 163.

[0074] In this embodiment, the protective member 113 has a three-layer structure, but the third layer 163 may be omitted. In this case, only the second layer 162 becomes the cap C, making it easier to make the thickness t of the cap C thinner.

[0075] On the other hand, in the above-mentioned three-layer laminate, the constituent material of the first layer 161 and the constituent material of the third layer 163 are the same (Si). In this case, the thermal expansion coefficients of the first layer 161 and the third layer 163 can be made the same, so warping of the laminate can be suppressed compared to when the third layer 163 is absent. As a result, a protective member 113 with less warping can be realized.

[0076] The number of voids 164 provided for each ultrasonic element 112 may be one or multiple. By providing multiple voids 164 for each ultrasonic element 112, the attenuation of ultrasonic waves in the protective member 113 can be further suppressed, thereby increasing the sound pressure of the transmitted ultrasonic waves. In addition, the reception sensitivity of ultrasonic waves in the sound wave device 1 can be further increased.

[0077] The shape of the void 164 when viewed from the Z direction can be, for example, a circle, ellipse, or oblong; a polygon such as a triangle, square, pentagon, or hexagon; or other shapes. Of these, a circle is preferred, and a circle is more preferred. This suppresses the reduction in the mechanical strength of the protective member 113 due to the void 164. In addition, the shape of the transmitted ultrasonic beam is improved, allowing for the transmission of ultrasonic waves that are less attenuated.

[0078] The arrangement of the multiple voids 164 is not particularly limited and may be random, but it is preferable that they be arranged regularly at regular intervals. Examples of regular arrangements include a square grid arrangement and a hexagonal grid arrangement.

[0079] The sealing member 114 is a mounting member disposed on the surface of the ultrasonic element 112 opposite to the Z direction. In the sealing member 114 shown in FIG. 4, a recess 172 that opens to the surface facing the Z direction is formed. The piezoelectric element 124 is housed in the recess 172. With such a configuration, the ultrasonic element 112 can be well supported while securing a space for the ultrasonic element 112 to vibrate.

[0080] Examples of the constituent material of the sealing member 114 include silicon-based materials such as Si; oxide-based materials such as SiOx (0 < x < 3) and ZrOx (0 < x < 3); resin-based materials such as permanent resist, and the like.

[0081] FIG. 10 is a cross-sectional view showing a modified example of the acoustic wave device 1 in FIG. 4. FIG. 11 is a plan view of the acoustic wave device 1 shown in FIG. 10.

[0082] In the acoustic wave device 1 shown in FIGS. 10 and 11, nine holes 164 are provided corresponding to one ultrasonic element 112. That is, the nine holes 164 face one hollow portion 182. Further, as shown in FIG. 11, the nine holes 164 are arranged in a square lattice. Thereby, an acoustic wave device 1 capable of transmitting an ultrasonic beam with a higher sound pressure and less variation in sound pressure over a wider range can be realized.

[0083] The lengths, widths, shapes, etc. of the nine holes 164 may be different from each other, but are preferably the same as each other. Thereby, the variation in the frequency of the ultrasonic wave transmitted through the protective member 113 is reduced, and an acoustic wave device 1 capable of transmitting an ultrasonic wave with a small frequency distribution can be obtained.

[0084] The number of holes 164 provided corresponding to one ultrasonic element 112 may be two or more and eight or less, or may be ten or more.

[0085] Even in such a modified example, the same effects as those of the acoustic wave device 1 shown in FIG. 4 can be obtained, and the sound pressure of the transmitted ultrasonic wave can be increased or the reception sensitivity of the ultrasonic wave can be increased.

[0086] Figure 12 is a cross-sectional view showing a modified example of the sound wave device 1 in Figure 4. Figure 13 is a plan view of the sound wave device 1 shown in Figure 12.

[0087] The sound wave device 1 shown in Figures 12 and 13 has nine voids 164 corresponding to nine ultrasonic elements 112. In other words, the sound wave device 1 shown in Figures 12 and 13 corresponds to a device formed by arranging nine sound wave devices 1 shown in Figures 4 to 6 in a square grid and coupling them together. This makes it possible to realize a sound wave device 1 capable of transmitting ultrasonic beams with higher sound pressure. Furthermore, the ultrasonic frequencies of the multiple ultrasonic elements 112 can be varied, or the transmission timing can be staggered. This makes it possible to transmit ultrasonic beams with multiple frequencies or ultrasonic beams with diversely controlled sound pressure changes.

[0088] Furthermore, the nine ultrasonic elements 112 are arranged in a square grid pattern, as shown in Figure 13. This makes it possible to realize an acoustic device 1 that can transmit an ultrasonic beam with higher sound pressure and less variation in sound pressure over a wider range.

[0089] The number of ultrasonic elements 112 in one sound wave device 1 may be between 2 and 8, or 10 or more.

[0090] Even in these modified versions, the same effects as the sound wave device 1 shown in Figure 4 can be obtained, and it is also possible to increase the sound pressure of the transmitted ultrasound and improve the reception sensitivity of the ultrasound.

[0091] Figure 14 is a cross-sectional view showing a modified example of the sound wave device 1 in Figure 12. The sound wave device 1 shown in Figure 14 is the same as the sound wave device 1 shown in Figure 12, except that the configuration of the hollow portion 182 formed in the substrate 111 is different.

[0092] In the acoustic wave device 1 shown in Figure 12, there are nine hollow portions 182 formed in the substrate 111, which is the same number as the ultrasonic elements 112. In contrast, the acoustic wave device 1 shown in Figure 14 has only one hollow portion 182. In other words, the hollow portion 182 shown in Figure 14 corresponds to a portion formed by connecting the nine hollow portions 182 shown in Figure 12. Even in these modified examples, the same effects as those obtained with the sound wave device 1 shown in Figure 12 can be obtained.

[0093] 2. Second Embodiment Next, as an example of an electronic device according to the second embodiment, wireless earphones will be described.

[0094] Figure 15 is an external view showing the schematic configuration of a wireless earphone 20 as an electronic device according to the second embodiment. Figure 16 is a partially enlarged cross-sectional view of Figure 15. Figure 17 is an external view of the wireless earphone 20 shown in Figure 15, viewed from a different angle than in Figure 15.

[0095] The second embodiment will be described below, focusing on the differences from the first embodiment, and similar matters will be omitted from the description. In Figures 15 to 17, components identical to those in the first embodiment are denoted by the same reference numerals.

[0096] The wireless earphones 20 shown in Figures 15 to 17 are similar to the image scanners 10 shown in Figures 1 and 2 in that they are equipped with a sound wave device 1. The wireless earphones 20 are worn in the user's ears and transmit audible sound waves, allowing the user to perceive sounds such as music.

[0097] The wireless earphone 20 shown in Figure 15 comprises a housing 24 and an acoustic device 1 built into the housing 24. The acoustic device 1 shown in Figure 15 has a base material 21, an acoustic element 22, and a protective member 23. Each of these components is the same as the components of the base material 111, ultrasonic element 112, and protective member 113 shown in Figure 4, except for the following.

[0098] The substrate 21 and the sound wave element 22 function as drivers that generate sound waves in the audible range. As shown in Figure 16, the protective member 23 is plate-shaped and has a first surface 235 and a second surface 236 that are on opposite sides, as well as multiple voids 234 that open in the first surface 235 and extend toward the second surface 236. The configuration of these voids 234 is the same as that of the voids 164 described above. In the protective member 23, the length, width, shape, etc., of the voids 164 are set so as to allow sound waves generated by the driver to pass through.

[0099] With this configuration, even though the void 234 is not exposed to the outside, sound waves generated by the driver can efficiently pass through the protective member 23 and be transmitted in the Z direction, realizing a sound wave device 1. In other words, a sound wave device 1 can be realized that transmits sound waves while suppressing attenuation of the sound waves generated by the driver.

[0100] Furthermore, in the wireless earphone 20, as shown in Figure 17, the second surface 236 of the protective member 23 is the sound wave transmission surface. Therefore, it is possible to suppress the intrusion of foreign matter such as dust into the sound wave device 1. In addition, because the sound wave transmission surface is flat, a wireless earphone 20 with excellent maintainability can be realized. In the second embodiment described above, the same effects as in the first embodiment can be obtained.

[0101] 8. Effects of the above embodiment As described above, the acoustic wave device 1 according to the embodiment comprises a base material 111, an ultrasonic element 112 (acoustic wave element), and a protective member 23. The base material 111 has a hollow portion 182. The ultrasonic element 112 is provided at a position corresponding to the hollow portion 182 of the base material 111 and generates ultrasonic waves (sound waves). The protective member 23 is provided on the surface of the base material 111 opposite to the surface on which the ultrasonic element 112 is provided and closes the hollow portion 182. The protective member 23 has a front and back relationship with itself, a first surface 165 facing the hollow portion 182, a second surface 166 located on the opposite side of the hollow portion 182, and a void 164 that opens to the first surface 165 and extends toward the second surface 166. The width W164 of the void 164 is smaller than the width W112 of the ultrasonic element 112, and the void 164 does not penetrate the protective member 113.

[0102] With this configuration, the protective member 113 prevents internal exposure, thus suppressing the intrusion of foreign matter into the interior. Furthermore, since ultrasonic waves can efficiently penetrate the protective member 113, a sound wave device 1 is obtained that does not easily attenuate the transmitted and received sound waves.

[0103] In the acoustic device 1 according to the above embodiment, the protective member 113 may have a laminate in which a first layer 161 and a second layer 162 located on the second surface 166 side of the first layer 161 are laminated together.

[0104] With this configuration, by using different materials for the first layer 161 and the second layer 162, holes that penetrate the first layer 161 but not the second layer 162, i.e., voids 164, can be efficiently formed using, for example, an etching method.

[0105] In the acoustic device 1 according to the above embodiment, it is preferable that the void 164 penetrates the first layer 161 but does not penetrate the second layer 162.

[0106] With this configuration, the thickness t of the cap C can be precisely controlled depending on the thickness of the second layer 162. Therefore, it is possible to realize an acoustic device 1 in which the frequency of sound waves transmitted through the protective member 113 is precisely controlled.

[0107] In the acoustic device 1 according to the above embodiment, the constituent materials of the first layer 161 and the constituent materials of the second layer 162 may be different from each other.

[0108] With this configuration, holes that penetrate the first layer 161 but not the second layer 162, i.e., voids 164, can be efficiently formed, for example, by using an etching method.

[0109] In the acoustic device 1 according to the above embodiment, the laminate may further have a third layer 163 laminated on the side of the second layer 162 opposite to the first layer 161.

[0110] With this configuration, for example, an SOI substrate can be used for the protective member 113. This makes it possible to manufacture a protective member 113 with a precisely controlled thickness t of the cap C at low cost. As a result, it is possible to realize an acoustic wave device 1 in which variations in the bandwidth of transmitted ultrasonic waves are suppressed, or an acoustic wave device 1 in which variations in the bandwidth of received ultrasonic waves are suppressed.

[0111] In the acoustic device 1 according to the above embodiment, the constituent materials of the first layer 161 and the third layer 163 may be the same as each other.

[0112] With this configuration, a protective member 113 with less warping due to differences in thermal expansion coefficients can be obtained.

[0113] In the acoustic device 1 according to the above embodiment, the constituent material of the first layer 161 may be Si, and the constituent material of the second layer 162 may be SiO2.

[0114] With this configuration, Si is easily processed by wet etching, while the processing rate of SiO2 by wet etching is lower than that of Si. Therefore, the first layer 161 can be processed with high precision to form voids 164 with high dimensional accuracy, while a protective member 113 with a precisely controlled thickness t of the cap C can be manufactured inexpensively, depending on the thickness of the second layer 162.

[0115] In the acoustic device 1 according to the above embodiment, it is preferable that the width W164 of the void 164 is smaller than the wavelength of the ultrasonic waves (sound waves).

[0116] With this configuration, the protective member 113 becomes an acoustic metamaterial, and a higher ultrasonic transmittance than that inherently possessed by the constituent material of the cap C can be imparted to the protective member 113.

[0117] In the acoustic device 1 according to the above embodiment, the length L164 of the void 164 is preferably 20% or more and 99% or less of the thickness T of the protective member 113.

[0118] With this configuration, a protective member 113 can be realized that has good transmittance in the ultrasonic range, particularly in ultrasonic frequencies of about 40 kHz to 1 MHz, which are suitable for detecting distance and double feed.

[0119] In the acoustic device 1 according to the above embodiment, the protective member 113 may have a plurality of voids 164.

[0120] With this configuration, the attenuation of ultrasonic waves in the protective member 113 can be further suppressed, thereby increasing the sound pressure of the transmitted ultrasonic waves. In addition, the reception sensitivity of ultrasonic waves in the sound wave device 1 can be further increased.

[0121] In the acoustic device 1 according to the above embodiment, the void 164 may be an etched hole.

[0122] With this configuration, the void 164 can be formed accurately in a short time. Therefore, the width W164 and length L164 of the void 164 are highly precise, and a sound wave device 1 in which the frequency of transmitted ultrasound is strictly controlled can be easily realized.

[0123] In the acoustic device 1 according to the above embodiment, the ultrasonic element 112 (acoustic element) may have a diaphragm 122, a first electrode 126, a piezoelectric film 127, and a second electrode 128. The diaphragm 122 is provided on the side of the base material 111 opposite to the protective member 113 and covers the hollow portion 182. The first electrode 126 is provided on the side of the diaphragm 122 opposite to the diaphragm 122. The piezoelectric film 127 is provided on the side of the first electrode 126 opposite to the diaphragm 122. The second electrode 128 is provided on the side of the piezoelectric film 127 opposite to the first electrode 126.

[0124] With this configuration, the ultrasonic element 112 can be formed by a thin-film deposition process, making manufacturing easy and contributing to a lower cost for the sound wave device 1.

[0125] In the acoustic wave device 1 according to the above embodiment, a sealing member 114 is provided on the side of the diaphragm 122 opposite to the base material 111. The sealing member 114 may have a recess 172 for housing an ultrasonic element 112 (acoustic wave element).

[0126] With this configuration, the ultrasonic element 112 can be properly supported while ensuring space for it to vibrate.

[0127] In the sound wave device 1 according to the above embodiment, the sound wave may be ultrasonic. With this configuration, for example, a sound wave device 1 capable of measuring distance or detecting objects can be realized.

[0128] The double-feed detection device (ultrasonic sensor 15) according to the above embodiment comprises a transmitting unit 151 and a receiving unit 152. The transmitting unit 151 is equipped with the sound wave device 1 according to the above embodiment and transmits ultrasonic waves. The receiving unit 152 is equipped with the sound wave device 1 according to the above embodiment and receives ultrasonic waves. In addition, the ultrasonic sensor 15 has the transmitting unit 151 and the receiving unit 152 positioned on either side of the transport path 130 for the paper P (medium). Furthermore, the ultrasonic sensor 15 transmits ultrasonic waves from the transmitting unit 151, receives the ultrasonic waves that have passed through the paper P in the receiving unit 152, and detects a double-feed of the paper P based on the signal strength of the received signal.

[0129] This configuration makes it possible to realize an ultrasonic sensor 15 with high accuracy in detecting double feeding and excellent reliability and maintainability.

[0130] The image scanner 10 as an electronic device according to the above embodiment includes the sound wave device 1 according to the above embodiment.

[0131] With this configuration, for example, foreign objects are prevented from entering the inside of the sound wave device 1, resulting in excellent reliability and maintainability. Furthermore, since ultrasonic attenuation in the protective member 113 is suppressed, an image scanner 10 with high accuracy in detecting double feeding of paper P can be realized.

[0132] Although the acoustic device, double-feed detection device, and electronic device according to the present invention have been described above based on the illustrated embodiments, the present invention is not limited thereto.

[0133] For example, in the sound wave device, double feed detection device, and electronic device according to the present invention, each part of the above embodiment may be replaced with any component having a similar function, or any component may be added to the above embodiment.

[0134] Furthermore, the electronic device according to the present invention can be applied to electronic devices other than image scanners and wireless earphones. [Explanation of symbols]

[0135] 1...Sonic device, 10...Image scanner, 11...Main unit, 11A...Feed port, 11B...Outlet port, 12...Paper support, 13...Transport unit, 14...Scanning unit, 14A...First scan unit, 14B...Second scan unit, 15...Ultrasonic sensor, 15C...Sensor central axis, 16...Control unit, 20...Wireless earphone, 21...Substrate, 22...Sonic element, 23...Protective member, 24...Housing, 111...Substrate, 112...Ultrasonic element, 113...Protective member, 114...Sealing member, 122...Diaphragm, 124...Piezoelectric element, 126...First electrode, 127...Piezoelectric film, 128...Second electrode, 130...Transport path, 131...Roller pair, 131A...Driven roller, 131B...Driven roller, 132...Roller -Pair, 132A...Drive roller, 132B...Driven roller, 133...Roller pair, 133A...Drive roller, 133B...Driven roller, 134...Roller pair, 134A...Drive roller, 134B...Driven roller, 135...Transport motor, 141...Light source, 142...Image sensor, 151...Transmitter, 152...Receiver, 161...First layer, 162...Second layer, 163...Third layer, 164...Void, 165...First surface, 166...Second surface, 172...Recess, 182...Hollow part, 234...Void, 235...First surface, 236...Second surface, C...Cap, P...Paper, S...Space, T...Thickness, t...Thickness, θ...Angle, L111...Length, L164...Length, W111...Width, W112...Width, W164...Width

Claims

1. A substrate having a hollow portion, A sound wave element is provided at a position corresponding to the hollow portion of the substrate and generates sound waves, A protective member is provided on the surface of the substrate opposite to the surface on which the sound wave element is provided, and which closes the hollow portion. Equipped with, The protective member has a front-and-back relationship with respect to each other, and has a first surface facing the hollow portion and a second surface located on the opposite side of the hollow portion, as well as a void opening in the first surface and extending toward the second surface. The width of the aforementioned void is smaller than the width of the sound wave element. The sound wave device is characterized in that the aforementioned void does not penetrate the protective member.

2. The sound wave device according to claim 1, wherein the protective member is a laminate comprising a first layer and a second layer located on the second surface side of the first layer.

3. The sound wave device according to claim 2, wherein the void penetrates the first layer but not the second layer.

4. The sound wave device according to claim 3, wherein the constituent materials of the first layer and the constituent materials of the second layer are different from each other.

5. The sound wave device according to claim 2, wherein the laminate further comprises a third layer laminated on the side of the second layer opposite to the first layer.

6. The sound wave device according to claim 5, wherein the constituent material of the first layer and the constituent material of the third layer are the same as each other.

7. The constituent material of the first layer is Si, The constituent material of the second layer is SiO ２ The sound wave device according to claim 2.

8. The sound wave device according to claim 1, wherein the width of the void is smaller than the wavelength of the sound wave.

9. The sound wave device according to claim 1, wherein the length of the void is 20% or more and 99% or less of the thickness of the protective member.

10. The sound wave device according to claim 1, wherein the protective member has a plurality of the aforementioned voids.

11. The sound wave device according to claim 1, wherein the aforementioned void is an etched hole.

12. The aforementioned sound wave element is A diaphragm is provided on the side of the base material opposite to the protective member, and covers the hollow portion, A first electrode is provided on the side of the diaphragm opposite to the hollow portion, A piezoelectric film provided on the side of the first electrode opposite to the diaphragm, A second electrode is provided on the side of the piezoelectric film opposite to the first electrode, The sound wave device according to claim 1, having the following characteristics.

13. The diaphragm is provided with a sealing member located on the side opposite to the substrate, The sound wave device according to claim 12, wherein the sealing member has a recess for housing the sound wave element.

14. The sound wave device according to claim 1, wherein the sound wave is an ultrasonic wave.

15. A sound wave device according to claim 14, comprising a transmitting unit that transmits the ultrasonic waves, The sound wave device according to claim 14 comprises a receiving unit that receives the ultrasonic waves, Equipped with, The transmitting unit and the receiving unit are arranged on either side of the medium transport path. A double-feed detection device characterized by transmitting the ultrasonic waves from the transmitting unit, receiving the ultrasonic waves that have passed through the medium with the receiving unit, and detecting double-feeding of the medium based on the signal strength of the received signal.

16. An electronic device characterized by comprising the sound wave device described in any one of claims 1 to 14.

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