Patent Publication Number: US-2018031684-A1

Title: Information processing apparatus including substrate on which vibration component that outputs sound wave through vibration is mounted

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The disclosure relates to an attaching structure of a substrate on which a vibration component that outputs a sound wave through vibration is mounted and a horn that limits an output direction of the sound wave. 
     Description of the Related Art 
     Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-545143 discusses a printed circuit board on which a surface mounted ceramic capacitor that vibrates due to a piezoelectric effect is mounted. 
     In Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-545143, however, a horn that limits the output direction of a sound wave output from the surface mounted ceramic capacitor is not discussed at all. A horn needs to be attached to limit the output direction of a sound wave output from a vibration component mounted on a substrate. For the reasons of dimensional constraints and the like of the vibration component, it is difficult to directly attach a horn to the vibration component mounted on a surface of the substrate. Thus, attaching the horn to the substrate on which the vibration component is mounted can be considered. 
     When the horn is attached to the substrate, it is necessary to prevent a sound wave output from the vibration component from leaking out from between the horn and the substrate. If the horn is brought into direct contact with the substrate to prevent a sound wave from leaking out from between the horn and the substrate, however, vibration of the vibration component is transmitted to the horn via the substrate. 
     SUMMARY OF THE INVENTION 
     The disclosure is directed to an information processing apparatus capable of inhibiting a sound wave output from a vibration component from leaking out from between a substrate and a horn and also inhibiting vibration of the vibration component from transmitting to the horn via the substrate. 
     According to an aspect of the disclosure, an information processing apparatus includes a substrate on which a vibration component that outputs a sound wave through vibration is mounted, a horn in a tubular shape configured to limit an output direction of the sound wave output from the vibration component, and a first buffer member provided between a surface of the substrate on a side on which the vibration component is provided and an opening on one side of the horn. 
     Further features and aspects of the disclosure will become apparent from the following description of various example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a multifunction peripheral (MFP). 
         FIG. 2  is a detailed block diagram of the MFP. 
         FIG. 3  is a view illustrating a detection area of an ultrasonic sensor. 
         FIG. 4  is a perspective view of a human sensor unit. 
         FIG. 5  is a block diagram illustrating devices mounted on a substrate. 
         FIG. 6  is a view illustrating the human sensor unit before a horn is mounted and the human sensor unit after the horn is mounted. 
         FIGS. 7A to 7C  are views illustrating a sectional view and the like of the human sensor unit. 
         FIG. 8  is a plan view illustrating a substrate on which the ultrasonic sensor is mounted. 
         FIGS. 9A to 9D  are views illustrating a detailed structure of the horn. 
         FIGS. 10A and 10B  are views illustrating a buffer member attached to the horn. 
         FIGS. 11A and 11B  are sectional views of the human sensor unit. 
         FIG. 12  is a diagram illustrating a case where a user approaches the MFP from the front thereof. 
         FIG. 13  is a diagram illustrating a case where the user approaches the MFP from the side thereof. 
         FIG. 14  is a diagram illustrating a case where a passerby passes in front of the MFP. 
         FIG. 15  is a flowchart illustrating a return algorithm based on a detection result by the ultrasonic sensor. 
     
    
    
     DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
     Hereinafter, a mode for carrying out the disclosure will be described using the drawings. A mode in which the disclosure is applied to a multifunction peripheral (MFP) having a plurality of functions such as scanning, printing, and copying will be described below. 
       FIG. 1  is a schematic block diagram of an MFP. 
     The MFP  10  includes a power supply unit  100 , a main controller unit  200 , a scanner unit (reading unit)  300 , a printer unit (printing unit)  400 , an operation unit  500 , and a human sensor unit  600 . The MFP  10  has at least two power modes. The MFP  10  has a standby mode in which functions such as scanning, printing, and copying can be executed and a sleep mode in which less power is consumed than in the standby mode. The standby mode is an S0 state and the sleep mode is an S3 state specified by the Advanced Configuration and Power Interface (ACPI) standard. 
     The MFP  10  transfers from the standby mode to the sleep mode when transfer conditions for the sleep mode are satisfied. Specifically, the MFP  10  transfers from the standby mode to the sleep mode after the passage of a predetermined time without the operation unit  500  being operated by a user. The transfer conditions for the sleep mode are not limited to the above passage of the predetermined time and may be a user&#39;s operation of a power-saving button provided on the operation unit  500 , that a preset sleep transfer time has come, or the passage of a predetermined time without a print process or a scan process being performed. 
     In the sleep mode, the supply of power to the main controller unit  200 , the scanner unit  300 , the printer unit  400 , and the operation unit  500  is limited. Also in the sleep mode, a display unit  501  of the operation unit  500  is turned off. In the standby mode, the display unit  501  of the operation unit  500  is turned on. Power is supplied to the main controller unit  200 , the scanner unit  300 , the printer unit  400 , and the operation unit  500  in the standby mode. 
     In the sleep mode, power is supplied to the human sensor unit  600 . In the sleep mode, the MFP  10  transfers from the sleep mode to the standby mode based on a detection result by the human sensor unit  600 . 
       FIG. 2  is a detailed block diagram of the MFP. 
     The scanner unit  300  optically reads an image of a document to generate image data. The scanner unit  300  includes a scanner control unit  321  and a scanner drive unit  322 . The scanner drive unit  322  includes a drive unit to move a reading head that reads an image of a document, and a drive unit to convey the document to a reading position. The scanner control unit  321  controls the operation of the scanner drive unit  322 . When a scan process is performed, the scanner control unit  321  receives setting information set by the user through communication with the main controller unit  200  and controls the operation of the scanner drive unit  322  based on the received setting information. 
     The printer unit  400  forms an image on a recording medium (sheet) according to the electrophotographic method. The printer unit  400  includes a printer control unit  421  and a printer drive unit  422 . The printer drive unit  422  includes a motor that rotates a photosensitive drum (not illustrated), a mechanism portion to press a fixing apparatus, and a heater. The printer control unit  421  controls the operation of the printer drive unit  422 . When a print process is performed, the printer control unit  421  receives setting information set by the user through communication with the main controller unit  200  and controls the operation of the printer drive unit  422  based on the received setting information. 
     The main controller unit  200  controls the operation of the scanner unit  300  and the printer unit  400 . For example, the main controller unit  200  causes the scanner unit  300  to read an image of a document to generate image data according to a copying instruction input into the operation unit  500 . Then, the main controller unit  200  performs image processing on the generated image data and outputs the processed image data to the printer unit  400 . Then, the main controller unit  200  causes the printer unit  400  to print the image. 
     The main controller unit  200  includes at least two power supply systems, i.e., a power supply system  1  to which devices that need to operate also in the sleep mode belong and a power supply system  2  to which devices that do not need to operate in the sleep mode belong. An internal power generation unit  202  that receives the supply of power from the power supply unit  100  via a power supply interface (I/F)  201  feeds power to the devices in the power supply system  1  in the sleep mode. In the sleep mode, power is not supplied to the devices in the power supply system  2 . 
     The supply of power to the devices in the power supply system  2  may only be limited in the sleep mode, instead of being stopped. Also in the sleep mode, the devices in the power supply system  2  may be clock-gated or the clock frequency may be lowered. The devices in the power supply system  1  include a power supply control unit  211 , a local area network (LAN) controller  212 , a facsimile (FAX) controller  213 , and a random access memory (RAM)  214 . Even when the MFP  10  is in the sleep mode, power is supplied to the FAX controller  213  and the LAN controller  212  in the sleep mode so that the controllers can return to the standby mode in response to FAX reception or a print request from a network. 
     The internal power generation unit  202  feeds power to the devices in the power supply system  2  in the standby mode. The devices in the power supply system  2  include a central processing unit (CPU)  221 , an image processing unit  222 , a scanner I/F  223 , a printer I/F  224 , a hard disk drive (HDD)  225 , and a read only memory (ROM)  226 . The supply of power to the devices in the power supply system  2  is stopped in the sleep mode. 
     The power supply control unit  211  is a device that controls the power mode of the MFP  10 . The power supply control unit  211  may be configured as a processor that executes software or as a logic circuit. Interrupt signals A, B, and C are input into the power supply control unit  211 . If one of the interrupt signals A, B, and C is input into the power supply control unit  211  in the sleep mode, the power supply control unit  211  controls the internal power generation unit  202  to supply power to the devices in the power supply system  2 . The MFP  10  is thereby returned from the sleep mode to the standby mode. 
     The interrupt signal A is a signal output by the FAX controller  213 . The FAX controller  213  outputs the interrupt signal A in response to FAX reception from a FAX line. The interrupt signal B is a signal output by the LAN controller  212 . The LAN controller  212  outputs the interrupt signal B in response to reception of a print job packet or a status confirmation packet from a LAN. The interrupt signal C is a signal output by a microcomputer  514  of the operation unit  500 . The microcomputer  514  outputs the interrupt signal C when the microcomputer  514  determines that a user of the MFP  10  is present based on a detection result by the human sensor unit  600  or a power-saving button  512  is pressed. 
     The CPU  221  to which power is supplied in response to input of one of the interrupt signals A to C returns the MFP  10  to the state before transferring to the sleep mode. Specifically, the CPU  221  reads information indicating the state of the MFP  10  from the RAM  214  performing a self-refresh operation in the sleep mode. Then, the CPU  221  uses the read information to return the MFP  10  to the state before transferring to the sleep mode. Then, the CPU  221  performs processing corresponding to a return factor of the interrupt signals A to C. 
     The operation unit  500  includes a liquid crystal display (LCD) touch panel unit  524  (display unit  501 ) in which an LCD panel and a touch panel are integrated, a key unit  515  that detects a user&#39;s key operation of the numeric keypad, the start key or the like, and a buzzer  526 . An image corresponding to image data generated by the CPU  221  of the main controller unit  200  is drawn in the LCD touch panel unit  524 . An LCD controller  523  receives image data from the CPU  221  and displays an image in the LCD touch panel unit  524  based on the image data. If the user touches the screen of the LCD touch panel unit  524 , a touch panel controller  516  analyzes coordinate data of the touched position and notifies the microcomputer  514  of the coordinate data. The microcomputer  514  notifies the CPU  221  of the coordinate data. The microcomputer  514  may notify the CPU  221  of, instead of the coordinate data, information indicating a touched icon or the like. The microcomputer  514  periodically scans the operation of the key unit  515 . Then, when the microcomputer  514  determines that the user has operated the key unit  515 , the microcomputer  514  notifies the CPU  221  of information about the key unit  515  that has been operated. When notified of a user&#39;s operation on the LCD touch panel unit  524  or the key unit  515 , the CPU  221  operates the MFP  10  according to the user&#39;s operation. 
     The operation unit  500  includes a plurality of light-emitting diodes (LEDs). A main power supply LED  511  lights up when the main power supply of the MFP  10  is turned on. A notification LED unit  527  is controlled to light up by the microcomputer  514  and notifies the user of the status of the MFP  10  such as execution of a job or the occurrence of an error. 
     The operation unit  500  includes, similarly to the main controller unit  200 , at least two power supply systems, i.e., the power supply system  1  to which devices that need to operate also in the sleep mode belong and the power supply system  2  to which devices that do not need to operate in the sleep mode belong. The devices in the power supply system  1  include the microcomputer  514 , the main power supply LED  511 , the power-saving button  512 , a power-saving LED  513 , the touch panel controller  516 , and the key unit  515 . The devices in the power supply system  2  include the LCD controller  523 , the LCD touch panel unit  524 , the buzzer  526 , and the notification LED unit  527 . Power is supplied to the power-saving button  512  and the power-saving LED  513  that lights up the power-saving button  512  even in the sleep mode so that the MFP  10  in the sleep mode can return from the sleep mode to the standby mode following a user&#39;s operation on the power-saving button  512 . 
     The human sensor unit  600  is a device in the power supply system  1  and operates to detect a user of the MFP  10  in the sleep mode. The human sensor unit  600  includes an ultrasonic sensor  610 . The microcomputer  514  determines whether a user of the MFP  10  is present by periodically reading and analyzing a detection result by the ultrasonic sensor  610 . The ultrasonic sensor  610  in the present example embodiment is a sensor that outputs and receives an ultrasonic wave by one chip. The ultrasonic sensor  610  may have a chip for oscillation that outputs an ultrasonic wave and a chip for reception that receives an ultrasonic wave separately. The ultrasonic sensor (vibration component)  610  in the present example embodiment outputs an ultrasonic wave by vibrating a piezoelectric element arranged inside the ultrasonic sensor  610  and also outputs an electric signal (voltage value) corresponding to the vibration received by the piezoelectric element. 
     In the present example embodiment, an example of using the ultrasonic sensor  610  will be described, but the sensor may not be an ultrasonic sensor. Instead of the ultrasonic sensor, for example, a pyroelectric sensor or an infrared sensor may be used. 
     The microcomputer  514  outputs an oscillation signal to the ultrasonic sensor  610  for a fixed time. As a result, the piezoelectric element of the ultrasonic sensor  610  vibrates to output an ultrasonic wave of about 40 KHz in an inaudible region for a fixed time. Then, the microcomputer  514  determines whether a user of the MFP  10  is present based on a detection result of the ultrasonic wave received by the ultrasonic sensor  610 . The microcomputer  514  outputs the interrupt signal C to the power supply control unit  211  based on the determination that a user of the MFP  10  is present. When the interrupt signal C is input, the power supply control unit  211  controls the power supply unit  100  to return the power mode of the MFP  10  from the sleep mode to the standby mode. In the present example embodiment, an example of supplying power from the internal power generation unit  202  to the human sensor unit  600  has been described, but power may be supplied to the human sensor unit  600  directly by the power supply unit  100 . 
       FIG. 3  is a view illustrating a detection area of an ultrasonic sensor. 
     The ultrasonic sensor  610  in the present example embodiment outputs an ultrasonic wave to receive an ultrasonic wave reflected by an object such as a human being (hereinafter, called a reflected wave when appropriate). The distance to a human being or an object can be estimated based on time from the output of an ultrasonic wave to reception of a reflected wave. In the present example embodiment, the microcomputer  514  calculates the distance to a human being or an object based on a detection result by the ultrasonic sensor  610 . 
     The ultrasonic sensor  610  is installed such that the detection area of the ultrasonic sensor  610  is the front of, or slightly downward of, the MFP  10 . The detection area is a range up to about 2 m from the MFP  10 . The installation location of the human sensor unit  600  is the front side of the scanner unit  300  and the opposite side of the operation unit  500  when the MFP  10  is viewed from the front side. The human sensor unit  600  is arranged by being inclined toward the operation unit  500  so that the user standing in front of the operation unit  500  can be detected. 
       FIG. 4  is a perspective view of the human sensor unit. 
     The human sensor unit  600  includes a substrate  620  on which the ultrasonic sensor  610  is mounted, a pedestal (fixing member)  630  that fixes the substrate  620 , a horn  640  to control directivity of an ultrasonic wave output from the ultrasonic sensor  610 , and a buffer member (sponge)  650 . The ultrasonic sensor  610  is a surface mount device (SMD) type ultrasonic sensor and is mounted on a surface of the substrate  620 . The ultrasonic sensor  610  has a piezoelectric element that outputs an ultrasonic wave according to an applied voltage and also outputs an electric signal corresponding to the received ultrasonic wave. 
     The pedestal  630  is a member to arrange the substrate  620  on which the ultrasonic sensor  610  is mounted such that the substrate  620  is inclined toward the operation unit  500 . 
       FIG. 5  is a block diagram illustrating devices mounted on the substrate. 
     The substrate  620  is a two-layer glass epoxy substrate. As illustrated in  FIG. 5 , the ultrasonic sensor  610 , a drive circuit  621 , a receiving resistance  622 , an amplifier circuit  623 , a detection circuit  624 , and a threshold circuit  625  are mounted on the substrate  620 . The drive circuit  621  vibrates the piezoelectric element of the ultrasonic sensor  610  in response to reception of a drive pulse P output by the CPU  221 . The receiving resistance  622  converts a sound pressure of the ultrasonic wave received by the ultrasonic sensor  610  into a voltage. The amplifier circuit  623  amplifies the converted voltage. A waveform V 1  of the voltage amplified by the amplifier circuit  623  is demodulated by the detection circuit  624 . Then, a signal V 2  output from the detection circuit  624  is compared with a voltage level set to the threshold circuit  625 . Then, an analog signal S is output from the threshold circuit  625  to the microcomputer  514 . The substrate  620  is arranged by being inclined toward the operation unit  500  by about 15 degrees relative to the front of the MFP  10 . However, the angle of the substrate  620  is not limited to about 15 degrees described above and is adjusted based on the positional relationship between the operation unit  500  and the human sensor unit  600 . Specifically, the angle decreases with a decrease in the distance between the operation unit  500  and the human sensor unit  600 , and the angle increases with an increase in the distance therebetween. 
     The horn  640  is a tubular member to limit the output direction of an ultrasonic wave so that the ultrasonic wave output from the ultrasonic sensor  610  is not diffused. Without the horn  640 , it is difficult to limit the detection range. An opening  644  of the horn  640  on the side of a cover member  301  ( FIG. 7 ) (the other side) has a rectangular shape of about 13 mm× about 13 mm and has a conic shape in which the size of the opening  644  decreases toward the ultrasonic sensor  610 . However, opening dimensions of the opening  644  of the horn  640  are not limited to the above dimensions. 
     The buffer member  650  is arranged between the opening  644  on the other side of the horn  640  and the cover member  301  ( FIG. 7 ) described below. The buffer member  650  fills a gap between the horn  640  and the cover member  301  so that an ultrasonic wave should not leak out from the gap between the horn  640  and the cover member  301 . 
       FIG. 6  is a view illustrating the human sensor unit before the horn is mounted and the human sensor unit after the horn is mounted. 
     The human sensor unit  600  is fixed to a frame plate (fixing member)  700  provided inside the scanner unit  300 . The substrate  620  is fixed to the pedestal  630  by a screw  626 . 
     The horn  640  is arranged on the side of the substrate  620  on which the ultrasonic sensor  610  is mounted. The horn  640  is fixed to the pedestal  630 . The buffer member  650  is attached to an end of the horn  640  on the side of the cover member  301 . The buffer member  650  is arranged between the horn  640  and the cover member  301  to fill the gap between the horn  640  and the cover member  301 . Accordingly, an ultrasonic wave output from the ultrasonic sensor  610  can be inhibited from leaking out from the gap between the horn  640  and the cover member  301 . The buffer member  650  is a sponge and thus can inhibit propagation of vibration of the horn  640  to the cover member  301 . 
       FIGS. 7A to 7C  are views illustrating a sectional view and the like of the human sensor unit.  FIG. 7A  is a front view of a portion of the scanner unit where the human sensor is provided.  FIG. 7B  is a top view of the portion of the scanner unit where the human sensor is provided.  FIG. 7C  is a sectional view taken along line A-A in  FIG. 7B . 
     If the human sensor unit  600  is arranged in a place where the user can touch, the ultrasonic sensor  610  or the substrate  620  may malfunction due to contact of the user&#39;s finger or the like with the ultrasonic sensor  610  or the substrate  620 . Thus, as illustrated in  FIG. 7A , the human sensor unit  600  is covered with the cover member  301  of the scanner unit  300 . A plurality of slits  302  is provided in the cover member  301  to output an ultrasonic wave output from the ultrasonic sensor  610  to the outside or to receive a reflected wave of an ultrasonic wave reflected outside. Each of the slits  302  has a hole shape stretching in the horizontal direction. In the present example embodiment, three slits are arranged along the vertical direction. The length in the horizontal direction (horizontal width) of the slit  302  is larger than the opening dimension of the horn  640  in the horizontal direction. 
       FIG. 8  is a plan view illustrating the substrate on which the ultrasonic sensor is mounted. 
     The ultrasonic sensor  610  is mounted on the substrate  620 . The drive circuit  621 , the receiving resistance  622 , the amplifier circuit  623 , the detection circuit  624 , and the threshold circuit  625  are mounted on the substrate  620 , but are omitted in  FIG. 8 . The substrate  620  has a screw hole  620   a  formed to allow the screw  626  to pass therethrough to fix the substrate  620  to the pedestal  630 . That is, the portion of the substrate  620  where the screw hole  620   a  is formed becomes a contact portion between the pedestal  630  and the substrate  620 . The screw  626  is fixed to the pedestal  630  via the screw hole  620   a . Also, a notched portion  620   b  on which a claw portion  631  formed in the pedestal  630  is hooked is formed at an end of the substrate  620  on the opposite side of the screw hole  620   a.    
     Also, slits  620   c  and  620   d  are formed in the substrate  620  around the ultrasonic sensor  610 . The slit  620   c  is formed in the substrate  620  between the ultrasonic sensor  610  and the screw hole  620   a . The slit  620   d  is formed in the substrate  620  between the ultrasonic sensor  610  and the notched portion  620   b . The length of the slit  620   c  in the longitudinal direction (Y direction in  FIG. 8 ) is longer than the length of the ultrasonic sensor  610  in the longitudinal direction. Also, the length of the slit  620   d  in the longitudinal direction is longer than the length of the ultrasonic sensor  610  in the longitudinal direction. 
     A slit  620   e  in an L shape is formed in the substrate  620  between the ultrasonic sensor  610  and the screw hole  620   a . The slit  620   e  is formed to surround the screw hole  620   a . Like the slit  620   c , the slit  620   e  is formed in the substrate  620  between the ultrasonic sensor  610  and the screw hole  620   a.    
     By forming the slits  620   c ,  620   d , and  620   e  in the substrate  620 , vibration of the ultrasonic sensor  610  can be prevented from propagating from the screw  626  or the claw portion to other members (the frame plate  700  and the pedestal  630 ). If it is necessary to electrically connect the substrate  620  and the frame plate  700  or the like, the screw  626  made of metal is adopted. If, however, it is not necessary to electrically connect the substrate  620  and the frame plate  700  or the like, the screw  626  made of plastic or the like may be adopted. When the screw  626  made of plastic is adopted, it is possible to suppress the propagation of vibration of the ultrasonic sensor  610  to other members via the screw  626 . 
     Furthermore, the substrate  620  in the present example embodiment has a boss hole  620   f  that allows a boss  643  provided in the horn  640  to pass therethrough. The relative position of the horn  640  relative to the ultrasonic sensor  610  can be determined with high precision by the boss  643  of the horn  640  being inserted into the boss hole  620   f . A buffer member  651  is brought into contact with an area represented by oblique lines in  FIG. 8 . The buffer member  651  comes into contact with an area of the substrate  620  where the slits  620   c  and  620   d  are formed. 
       FIGS. 9A to 9D  are views illustrating a detailed structure of the horn.  FIG. 9A  is a front view of the horn.  FIG. 9B  is a sectional view taken along line B-B in  FIG. 9A .  FIG. 9C  is a rear view of the horn.  FIG. 9D  is a sectional view taken along line C-C in  FIG. 9A . 
     The horn  640  is a member that controls directivity of an ultrasonic wave sent from the ultrasonic sensor  610  mounted on the substrate  620 . As illustrated in  FIGS. 9A and 9D , the horn  640  has a conic shape in which the opening size decreases toward the ultrasonic sensor  610 . An inner surface  645  of the horn  640  in the present example embodiment is configured as a plurality of planes, but may also be configured as curved surfaces. The horn  640  is provided with hook portions  641  and  642  to fix the horn  640  to the pedestal  630 . The horn  640  is fixed to the pedestal  630  without being fixed to the substrate  620 . By fixing the horn  640  to the pedestal  630 , vibration of the ultrasonic sensor  610  is inhibited from propagating to the horn  640 . As long as the vibration to the horn  640  can sufficiently be inhibited by the slits  620   c ,  620   d , and  620   e  provided in the substrate  620 , the horn  640  may be fixed to the substrate  620 . 
     Also, as illustrated in  FIGS. 9B and 9C , the horn  640  has two bosses  643  formed to determine the position of the horn  640  relative to the ultrasonic sensor  610 . It is better to arrange the horn  640  close to the ultrasonic sensor  610  so that an ultrasonic wave output from the ultrasonic sensor  610  is output with directivity. If, however, the horn  640  is fixed to the substrate  620  on which the ultrasonic sensor  610  is mounted, vibration of the ultrasonic sensor  610  propagates to the horn  640 . Also, vibration of the ultrasonic sensor  610  is inhibited by the horn  640 . 
       FIGS. 10A and 10B  are views illustrating a buffer member attached to the horn.  FIG. 10A  is a view illustrating the buffer member attached to the horn on the side of the cover member.  FIG. 10B  is a view illustrating the buffer member attached to the horn on the side of the substrate. 
     As illustrated in  FIG. 10A , the buffer member  650  is arranged between the horn  640  and the cover member  301 . The buffer member  650  is a sponge. Also, the buffer member  650  is annular and has an opening larger than the opening  644  of the horn  640  on the side of the cover member  301  (the other side). 
     As illustrated in  FIG. 10B , the buffer member  651  is arranged between the opening  644  of the horn  640  on the side of the substrate  620  (one side) and the substrate  620 . The buffer member  651  is, like the buffer member  650 , a sponge. Also, the buffer member  651  is annular and has an opening larger than the opening  644  of the horn  640  on the side of the substrate  620  (one side). 
     The buffer member  650  and the buffer member  651  are desirably made of a raw material of high sound absorbing properties and sound insulating properties. As a raw material superior in sound absorbing properties, for example, a porous material having a rough surface and a large number of bubble shapes inside such as glass wool, rock wool, and soft urethane foam is desirably adopted for the buffer members  650  and  651 . Furthermore, as a raw material superior in sound insulating properties, a flexible raw material such as sponge and rubber having a small stress when compressed and conforming well with irregularities of an adherend can be adopted for the buffer members  650  and  651 . 
     A raw material of high vibration-proof properties and vibration control properties is more desirable for the buffer member  650  and the buffer member  651 . As a raw material superior in vibration-proof properties and vibration control properties, for example, an elastic damping material such as rubber and sponge can be adopted for the buffer member  650  and the buffer member  651 . 
     In the present example embodiment, EPTSEALER manufactured by Nitto Denko Corporation or CALMFLEX manufactured by Inoac Corporation is adopted for the buffer members  650  and  651 . 
       FIGS. 11A and 11B  are sectional views of the human sensor unit.  FIG. 11A  is an exploded sectional view of the human sensor unit.  FIG. 11B  is a sectional view of the human sensor unit. 
     As illustrated in  FIG. 11A , the buffer member  651  is not compressed before the horn  640  is fixed to the pedestal  630 . Also as illustrated in  FIG. 11A , the buffer member  650  is not compressed before the cover member  301  is attached in front of the horn  640 . 
     When the horn  640  is fixed to the pedestal  630 , the buffer member  651  is compressed and the gap between the substrate  620  and the horn  640  is closed up. As a result, an ultrasonic wave output from the ultrasonic sensor  610  is inhibited from leaking out from the gap between the substrate  620  and the horn  640 . Furthermore, the substrate  620  comes into contact with the horn  640  via the buffer member  651  and thus, vibration of the ultrasonic sensor  610  can be inhibited from propagating from the substrate  620  to the horn  640 . 
     Furthermore, if the cover member  301  is attached, the buffer member  650  is compressed and the gap between the cover member  301  and the horn  640  is closed up. Accordingly, an ultrasonic wave output from the ultrasonic sensor  610  is inhibited from leaking out from the gap between the cover member  301  and the horn  640 . Furthermore, the horn  640  comes into contact with the cover member  301  via the buffer member  650  and thus, vibration of the ultrasonic sensor  610  can be inhibited from propagating from the horn  640  to the cover member  301 . 
       FIG. 12  is a diagram illustrating a case where a user approaches the MFP from the front thereof. Diagrams when the positional relationship between the MFP  10  and the user is viewed from the side are illustrated in the top section of  FIG. 12 . Diagrams when the positional relationship between the MFP  10  and the user is viewed from above are illustrated in the middle section of  FIG. 12 . Detection results by an ultrasonic sensor are illustrated in the bottom section of  FIG. 12 . In  FIG. 12 , states at t 1  to t 4  are illustrated in order from left. This also applies to  FIGS. 13 and 14  described below. 
     As illustrated in the bottom section of  FIG. 12 , the waveform of detection results by the ultrasonic sensor  610  includes a waveform accompanying oscillation of an ultrasonic wave and a waveform of a reflected wave. The ultrasonic sensor  610  in the present example embodiment outputs an ultrasonic wave by oscillating the ultrasonic sensor  610  for a predetermined time. Thus, in an initial stage of detection results by the ultrasonic sensor  610 , an influence of oscillation for the output of an ultrasonic wave arises. Then, the ultrasonic sensor  610  receives a reflected wave of the ultrasonic wave reflected by a person or an object. The ultrasonic sensor  610  outputs sound pressure intensity of a reflected wave as a voltage value (this voltage value is denoted as a detection amplitude V). If an output unit that outputs an ultrasonic wave is configured separately from a receiving unit that receives the ultrasonic wave, a waveform accompanying the above oscillation does not appear, but the ultrasonic wave output from the output unit is directly received by the receiving unit and thus, a waveform similar to the waveform illustrated in  FIG. 12  is obtained. 
       FIG. 12  (t 1 ) illustrates a state in which the user enters a place that can be detected by the ultrasonic sensor  610 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 1  larger than a preset threshold amplitude Vth 2  is generated when time D 1  passes after the ultrasonic wave is oscillated. The time D 1  is the time needed for the ultrasonic wave to return after the ultrasonic wave is output and reflected by the user and thus corresponds to the distance between the MFP  10  and the user. In the description that follows, the time D 1  (the time between the output of a direct wave and detection of a reflected wave) is handled as a distance D 1 . In the present example embodiment, it is determined that a person is present in a detection area A 1  based on detection of the detection amplitude V larger than the threshold amplitude Vth 2  at a distance farther than a predetermined distance Dth (hereinafter, called a threshold distance Dth). Also, it is determined that a person is present in a detection area A 2  based on detection of the detection amplitude V larger than a threshold amplitude Vth 1  (&gt;Vth 2 ) at a distance shorter than the threshold distance Dth. When a user is present in a position far from the ultrasonic sensor  610 , reflected waves from afar diffuse and all reflected waves cannot be received and thus, the detection amplitude V attenuates and becomes smaller. In  FIG. 12  (t 1 ), the detection amplitude V exceeding the threshold amplitude Vth 1  is not generated at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 12  (t 2 ) illustrates a state in which the user moves toward the detection area A 2 . The user has not yet entered the detection area A 2 . 
     As a detection result by the ultrasonic sensor  610 , a detection amplitude V 2  larger than the threshold amplitude Vth 2  is output at a distance D 2  shorter than the distance D 1  and farther than the threshold distance Dth. The detection amplitude V 2  is larger than the detection amplitude V 1 . In  FIG. 12  (t 2 ), the detection amplitude V exceeding the threshold amplitude Vth 1  is not generated at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 12  (t 3 ) illustrates a state in which the user has entered the detection area A 2 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 3  larger than the threshold amplitude Vth 1  is output at a distance D 3  shorter than the threshold distance Dth. In  FIG. 12  (t 3 ), the detection amplitude V exceeding the threshold amplitude Vth 1  is generated at a distance shorter than the threshold distance Dth, but the detection amplitude V exceeding the threshold amplitude Vth 1  has not been generated continuously for a predetermined time at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 12  (t 4 ) illustrates a state in which the user remains in the detection area A 2 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 4  larger than the threshold amplitude Vth 1  is output at a distance D 4  shorter than the threshold distance Dth. If the detection amplitude V exceeding the threshold amplitude Vth 1  is generated continuously for a predetermined time at a distance shorter than the threshold distance Dth, the MFP  10  cancels the sleep mode to transfer to the standby mode. The predetermined time is, for example, 300 ms. 
       FIG. 13  is a diagram illustrating a case where the user approaches the MFP from the side thereof. 
       FIG. 13  (t 1 ) illustrates a state in which the user enters a place that can be detected by the ultrasonic sensor  610 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 5  larger than the threshold amplitude Vth 1  is output at a distance D 5  shorter than the threshold distance Dth. At this point, the detection amplitude V exceeding the threshold amplitude Vth 1  has not been generated continuously for a predetermined time (for example, 300 ms) at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 13  (t 2 ) illustrates a state in which the user moves in the detection area A 2 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 6  larger than the threshold amplitude Vth 1  is output at a distance D 6  shorter than the threshold distance Dth. Also at this point, the detection amplitude V exceeding the threshold amplitude Vth 1  has not been generated continuously for a predetermined time (for example, 300 ms) at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 13  (t 3 ) illustrates a state in which the user arrives in front of the MFP  10 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 7  larger than the threshold amplitude Vth 1  is output at a distance D 7  shorter than the threshold distance Dth. Also at this point, the detection amplitude V exceeding the threshold amplitude Vth 1  has not been generated continuously for a predetermined time (for example, 300 ms) at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 13  (t 4 ) illustrates a state in which the user remains in front of the MFP  10 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 8  larger than the threshold amplitude Vth 1  is output at a distance D 8  shorter than the threshold distance Dth. At this point, the detection amplitude V exceeding the threshold amplitude Vth 1  has been generated continuously for a predetermined time (for example, 300 ms) at a distance shorter than the threshold distance Dth and thus, the MFP  10  cancels the sleep mode to return to the standby mode. 
       FIG. 14  is a diagram illustrating a case where a passerby passes in front of the MFP. 
       FIG. 14  (t 1 ) illustrates a state in which the passerby enters the range of distance that can be detected by the ultrasonic sensor  610 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 9  larger than the threshold amplitude Vth 1  is output at a distance D 9  shorter than the threshold distance Dth. At this point, the detection amplitude V exceeding the threshold amplitude Vth 1  has not been generated continuously for a predetermined time (for example, 300 ms) at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 14  (t 2 ) illustrates a state in which the passerby moves in the detection area A 2 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 10  larger than the threshold amplitude Vth 1  is output at a distance D 10  shorter than the threshold distance Dth. Also at this point, the detection amplitude V exceeding the threshold amplitude Vth 1  has not been generated continuously for a predetermined time (for example, 300 ms) at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 14  (t 3 ) illustrates a state in which the passerby moves out of the detection area A 2 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 11  larger than the threshold amplitude Vth 1  is output at a distance D 11  longer than the threshold distance Dth. The detection amplitude V 11  larger than the threshold amplitude Vth 1  is not generated at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. 
       FIG. 14  (t 4 ) illustrates a state in which the passerby moves out of the detection area A 1 . As a detection result by the ultrasonic sensor  610 , a detection amplitude V 12  smaller than the threshold amplitude Vth 1  is output at a distance D 12  longer than the threshold distance Dth. The detection amplitude V larger than the threshold amplitude Vth 1  is not generated at a distance shorter than the threshold distance Dth and thus, the MFP  10  maintains the sleep mode. When, like in  FIG. 14  (t 4 ), the passerby starts to leave the place where the MFP  10  is used (position in front of the operation unit  500 ), the detection distance D gradually increases and the detection amplitude V becomes gradually smaller. 
       FIG. 15  is a flowchart illustrating a return algorithm based on a detection result by the ultrasonic sensor. The microcomputer  514  of the MFP  10  executes each step in  FIG. 15  according to a program. 
     In step S 1001 , the microcomputer  514  acquires a detection result by the ultrasonic sensor  610  at fixed intervals (for example, 100 ms). In step S 1002 , the microcomputer  514  calculates the distance D to the position where the detection amplitude V larger than the detection amplitude Vth 1  is generated based on the detection result acquired from the ultrasonic sensor  610 . In step S 1003 , the microcomputer  514  determines whether the calculated distance D is equal to or larger than a preset threshold distance Dth. 
     If the calculated distance D is determined to be equal to or larger than the preset threshold distance Dth (YES in step S 1003 ), the microcomputer  514  increments a count C in step S 1004 . Next, in step S 1005 , the microcomputer  514  determines whether the count C is equal to or larger than a preset predetermined value Ct (for example, Ct=4). If the count C is determined to be equal to or larger than the preset predetermined value Ct (YES in step S 1005 ), the microcomputer  514  outputs an interrupt signal C to the power supply control unit  211  in step S 1006 . The power supply control unit  211  having received the interrupt signal C returns the MFP  10  from the sleep mode to the standby mode. In step S 1007 , the microcomputer  514  clears the count C. 
     If, in step S 1003 , the calculated distance D is determined to be less than the threshold distance Dth (NO in step S 1003 ), the microcomputer  514  clears the count C in step S 1008 . 
     Other Embodiments 
     Embodiment(s) of the disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the disclosure has been described with reference to example embodiments, it is to be understood that the invention is not limited to the disclosed example embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2016-150104, filed Jul. 29, 2016, which is hereby incorporated by reference herein in its entirety.