Patent Publication Number: US-2018031670-A1

Title: Printed circuit board on which vibration component for generating vibration is mounted

Description:
BACKGROUND 
     Field 
     An aspect of the present invention generally relates to a shape of a printed circuit board on which a vibration component for generating vibration is mounted. 
     Description of the Related Art 
     An information processing apparatus of recent years has been provided with a sensor for detecting a person who uses the information processing apparatus (hereinafter, referred to as “human detection sensor”). Japanese Patent Application Laid-Open No. 2015-195548 discusses an image forming apparatus provided with an ultrasonic sensor (i.e., vibration component) as a human detection sensor. 
     The ultrasonic sensor is mounted on a printed circuit board on which a driving circuit for outputting an ultrasonic wave and an amplification circuit for amplifying a reflected wave of the received ultrasonic wave are mounted. The ultrasonic sensor outputs the ultrasonic wave when a voltage is applied to a piezoelectric element to make the piezoelectric element vibrate. Further, the piezoelectric element is vibrated with a reflected wave of the output ultrasonic wave, so that the ultrasonic sensor outputs a detection result (e.g., voltage value) according to the vibration. 
     The vibration of the ultrasonic sensor propagates to the other members of the printed circuit board on which the ultrasonic wave is mounted. Then, the other members vibrate along with the vibration of the ultrasonic sensor, so that the vibration thereof propagates to the ultrasonic sensor via the printed circuit board. In this way, the vibration of the other members induced by the vibration of the ultrasonic sensor propagates to the ultrasonic sensor via the printed circuit board. 
     SUMMARY 
     An aspect of the present invention is directed to a printed circuit board capable of suppressing vibration of other members induced by a vibration component mounted on a printed circuit board from propagating to the vibration component via the printed circuit board. 
     According to an aspect of the present invention, a printed circuit board is fixed to a pedestal, and a vibration component that generates vibration in the operation period is mounted thereon. A slit is formed on the printed circuit board, and this slit is formed on a straight line that connects a first position where the vibration component is mounted on the printed circuit board and a second position where the printed circuit board is in contact with the pedestal. 
     Further features of aspects of the present invention will become apparent from the following description of exemplary 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 block diagram illustrating details of the MET. 
         FIG. 3  is a diagram illustrating a detection area of an ultrasonic sensor. 
         FIG. 4  is a diagram illustrating a perspective view of a human detection sensor unit. 
         FIG. 5  is a block diagram illustrating devices mounted on a board. 
         FIG. 6  is a diagram illustrating a human detection sensor unit before and after a horn is attached thereto. 
         FIGS. 7A, 7B, and 7C  are diagrams respectively illustrating a front view, a top view, and a cross-sectional view of the human detection sensor unit. 
         FIG. 8  is a diagram illustrating a plan view of a board on which an ultrasonic sensor is mounted. 
         FIGS. 9A, 9B, 9C, and 9D  are diagrams illustrating a detailed structure of the horn. 
         FIGS. 10A and 10B  are diagrams illustrating a shock-absorbing member attached to the horn. 
         FIGS. 11A and 11B  are diagrams illustrating cross-sectional views of the human detection sensor unit. 
         FIG. 12  is a diagram illustrating a state where a user approaches the MFP from a front face thereof. 
         FIG. 13  is a diagram illustrating a state where a user approaches the MFP from a side face thereof. 
         FIG. 14  is a diagram illustrating a state where a person passes in front of the MFP. 
         FIG. 15  is a flowchart illustrating return algorithm based on a detection result of the ultrasonic sensor. 
         FIGS. 16A, 16B, and 16C  are diagrams illustrating variation examples of the board. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an exemplary embodiment of the present invention will be described with reference to the appended drawings. An exemplary embodiment in which the present invention is applied to a multifunction peripheral (MFP) having a plurality of functions such as scanning, printing, and copying will be described. 
       FIG. 1  is a block diagram schematically illustrating an MFP. 
     An MFP  10  includes a power source 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 detection sensor unit  600 . The MFP  10  includes at least two power modes. The MFP  10  includes a stand-by mode in which functions such as scanning, printing, and copying can be executed, and a sleep mode in which power consumption is lower than that of the stand-by mode. The stand-by mode and the sleep mode respectively corresponds to a state S0 and a state S3 specified in the Advanced Configuration and Power Interface (ACPI) standard. 
     The MFP  10  shifts to a sleep mode from a stand-by mode when a condition of shifting to the sleep mode is satisfied. More specifically, the MFP  10  shifts to a sleep mode from a stand-by mode when a predetermined time has passed without the user operating the operation unit  500  in the stand-by mode. The condition of shifting to the sleep mode is not limited to the above-described passage of a predetermined time, and the MFP  10  also shifts to the sleep mode when a user operates a power saving button provided on the operation unit  500 , when the time has reached a preset sleep mode shifting time, or when a predetermined time has passed without executing printing processing or scanning processing. 
     In the sleep mode, power supplied to the main controller unit  200 , the scanner unit  300 , the printer unit  400 , and the operation unit  500  is limited. Further, in the sleep mode, display unit  501  of the operation unit  500  is turned off. In the stand-by mode, the display unit  501  of the operation unit  500  is turned on. In the stand-by mode, power is supplied to the main controller unit  200 , the scanner unit  300 , the printer unit  400 , and the operation unit  500 . 
     in the sleep mode, power is supplied to the human detection sensor unit  600 . The human detection sensor unit  600  does not operate in the stand-by mode whereas the human detection sensor unit  600  operates in the sleep mode. In the sleep mode, the MFP  10  shifts to the stand-by mode from the sleep mode based on a detection result of the human detection sensor unit  600 . 
       FIG. 2  is a block diagram illustrating details of the MFP  10 . 
     The scanner unit  300  optically reads an image of a document and generates image data. The scanner unit  300  includes a scanner control unit  321  and a scanner driving unit  322 . The scanner driving unit  322  includes a driving unit for moving a reading head for reading an image of a document and a driving unit for conveying a document to a reading position. The scanner control unit  321  controls the operation of the scanner driving unit  322 . When scanning processing is executed, the scanner control unit  321  communicates with the main controller unit  200  to receive setting information set by the user and controls the operation of the scanner driving unit  322  based on the received setting information. 
     The printer unit  400  forms an image on a recording medium (sheet) through an electrophotographic method. The printer unit  400  includes a printer control unit  421  and a printer driving unit  422 . The printer driving unit  422  includes (and not shown) a motor rotating a photosensitive drum, a mechanism portion for pressurizing a fixing unit, and a heater. The printer control unit  421  controls the operation of the printer driving unit  422 . When printing processing is executed, the printer control unit  421  communicates with the main controller unit  200  to receive setting information set by the user and controls the operation of the printer driving unit  422  based on the received setting information. 
     The main controller unit  200  controls the operations of the scanner unit  300  and the printer unit  400 . For example, the main controller unit  200  controls the scanner unit  300  to read an image of a document and generate image data according to a copying instruction input to the operation unit  500 . Then, the main controller unit  200  executes image processing on the generated image data and outputs the processed image data to the printer unit  400 . Then, the main controller unit  200  controls the printer unit  400  to print an image. 
     The main controller unit  200  includes at least two power source systems, i.e., power source system  1  which includes devices that have to operate in the sleep mode and a power source system  2  which includes devices that do not have to operate in the sleep mode. An internal power source generation unit  202  receives power from the power source unit  100  via a power source interface (I/F)  201  and supplies power to the devices in the power source system  1  in the sleep mode. In the sleep mode, power is not supplied to the devices in the power source system  2 . 
     in addition, power supply with respect to the devices in the power source system  2  does not have to be stopped but may be limited in the sleep mode. Further, clock-gating may be performed with respect to the devices in the power source system  2  or clock frequency may be lowered in the sleep mode. The devices in the power source system  1  include a power source control unit  211 , a local area network (LAN) controller  212 , a facsimile (FAX) controller  213 , and a random access memory (RAM)  214 . In order to enable the MFP  10  to return to the stand-by mode when the MFP  10  receives a fax or receives a print request through the network during the sleep mode, power is supplied to the fax controller  213  or the LAN controller  212  in the sleep mode. 
     In the stand-by mode, the internal power source generation unit  202  supplies power to the devices in the power source system  2 . The devices in the power source 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 . In the sleep mode, power supply to the devices in the power source system  2  is stopped. 
     The power source control unit  211  is a device for controlling a power mode of the MFP  10 . The power source control unit  211  may be configured of a processor that executes software, or may be configured of a logic circuit. Interrupt signal A, B, or C is input to the above-described power source control unit  211 . When the interrupt signal A, B, or C is input to the power source control unit  211  in the sleep mode, the power source control unit  211  controls the internal power source generation unit  202  to supply power to the devices in the power source system  2 . Through this operation, the MFP  10  returns to the stand-by mode from the sleep mode. 
     The interrupt signal A is a signal output from the fax controller  213 , and the fax controller  213  outputs the interrupt signal A when a fax is transmitted through a fax line. The interrupt signal B is a signal output from the LAN controller  212 , and the LAN controller  212  outputs the interrupt signal B when a print job packet or a status check packet is received through a LAN. The interrupt signal C is a signal output from a microcomputer  514  of the operation unit  500 , and the microcomputer  514  outputs the interrupt signal C when existence of a user of the MFP  10  is determined based on a detection result of the human detection sensor unit  600  or when a power saving button  512  is pressed. 
     Because the interrupt signal A, B, or C is input thereto, the CPU  221  receives power and makes the MFP  10  return to a state before shifting to the sleep mode. More specifically, the CPU  211  reads out information indicating a state of the MFP  10  from the RAM  214  that has been executing self-refresh operation in the sleep mode. Then, the CPU  211  uses the read information to bring back the MFP  10  to a state before shifting to the sleep mode. Then, the CPU  221  executes processing according to the return factor of the interrupt signal A, B, or C. 
     The operation unit  500  includes a liquid crystal display (LCD) touch panel unit  524  (display unit  501 ) integrally configured of an LCD panel and a touch panel, a key unit  515  for detecting key operations of a numerical keypad or a start key performed by the user, and a buzzer  526 . An image corresponding to the image data generated by the CPU  221  of the main controller unit  200  is rendered on the LCD touch panel unit  524 . An LCD controller  523  receives image data from the CPU  221  and displays an image on the LCD touch panel unit  524  based on the image data. When the user touches a screen of the LCD touch panel unit  524 , a touch panel controller  516  analyzes coordinate data of touched position and notifies the coordinate data to the microcomputer  514 . The microcomputer  514  notifies the coordinate data to the CPU  221 . In addition, the microcomputer  514  may notify the CPU  221  of information indicating a touched icon instead of the coordinate data. The microcomputer  514  periodically scans operations performed on the key unit  515 . Then, if the microcomputer  514  determines that the key unit  515  is operated by the user, the microcomputer  514  notifies the CPU  221  of information about the operated key unit  515 . The CPU  221  is notified of the user operation with respect to the LCD touch panel  524  or the key unit  515  to make the MFP  10  operate according to the user operation. 
     The operation unit  500  includes a plurality of light-emitting diodes (LEDs). A main power LED  511  is turned on when a main power of the MFP  10  is ON. A notification LED unit  527  is turned on through the control of the microcomputer  514 , and notifies the user of a state of the MFP  10  when a job is executed or an error has occurred. 
     Similar to the main controller unit  200 , the operation unit  500  also includes at least two power source systems, i.e., a power source system  1  which includes devices that have to operate in the sleep mode and a power source system  2  which includes devices that do not have to operate in the sleep mode. The devices in the power source system  1  includes the microcomputer  514 , the main power LED  511 , the power saving button  512 , the power saving LED  513 , the touch panel controller  516 , and the key unit  515 . The devices in the power source system  2  includes the LCD controller  523 , the LCD touch panel unit  524 , the buzzer  526 , and the notification LED unit  527 . In order to enable the MFP  10  to return to the stand-by mode from the sleep mode when the user operates the power saving button  512  in the sleep mode, power is supplied to the power saving button  512  and the power saving LED  513  for lighting up the power saving button  512  in the sleep mode. 
     The human detection sensor unit  600  is a device included in the power source system  1 , and operates in the sleep mode to detect a user of the MFP  10 . The human detection sensor unit  600  includes an ultrasonic sensor  610 . The microcomputer  514  periodically reads and analyzes a detection result of the ultrasonic sensor  610  to determine whether the user of the MFP  10  exists. The ultrasonic sensor  610  according to the present exemplary embodiment is a sensor that executes output and reception of the ultrasonic waves through a single chip. In addition, the ultrasonic sensor  610  may be configured of an oscillation chip for outputting the ultrasonic wave and a reception chip for receiving the ultrasonic wave. The ultrasonic sensor (vibration component)  610  of the present exemplary embodiment makes a piezoelectric element arranged inside the ultrasonic sensor  610  vibrate to output the ultrasonic wave, and outputs an electric signal (voltage value) corresponding to the vibration received by the piezoelectric element. 
     In the present exemplary embodiment, although an exemplary embodiment using the ultrasonic sensor  610  will be described, a sensor other than the ultrasonic sensor  610  may be used. For example, a pyroelectric sensor or an infrared sensor may be used instead of the ultrasonic sensor  610 . 
     The microcomputer  514  outputs an oscillation signal to the ultrasonic sensor  610  for a certain period. With this operation, the piezoelectric element of the ultrasonic sensor  610  is vibrated, and an ultrasonic wave in a non-audible range of  40  KHz is output for a certain period. Thereafter, the microcomputer  514  determines existence of the user of the MFP  10  based on a detection result of the ultrasonic wave received by the ultrasonic sensor  610 . The microcomputer  514  outputs an interrupt signal C to the power source control unit  211  when existence of the user of the MFP  10  is determined. When the interrupt signal C is input thereto, the power source control unit  211  controls the power source unit  100  to return the power mode of the MFP  10  to the stand-by mode from the sleep mode. Further, in the present exemplary embodiment, although an exemplary embodiment in which power is supplied to the human detection sensor unit  600  from the internal power source generation unit  202  has been described, power may be directly supplied to the human detection sensor unit  600  from the power source unit  100 . 
       FIG. 3  is a diagram illustrating a detection area of the ultrasonic sensor  610 . 
     The ultrasonic sensor  610  according to the present exemplary embodiment outputs an ultrasonic wave and receives an ultrasonic wave reflected on an object such as a human (hereinafter, referred to as “reflected wave” as appropriate). A distance to the object or the human can be estimated based on the time taken to receive the reflected wave after outputting the ultrasonic wave. In the present exemplary embodiment, the microcomputer  514  calculates a distance to the human or the object based on a detection result of the ultrasonic sensor  610 . 
     The ultrasonic sensor  610  is disposed so as to make a front side or a slightly lower side of the MFP  10  be set as a detection area of the ultrasonic sensor  610 . The detection area is a range within 2 m from the MFP  10 . The human detection sensor unit  600  is disposed at a position on a front side of the scanner unit  300  and an opposite side of the operation unit  500  when the MFP  10  is viewed from the front. The human detection sensor unit  600  is disposed so as to be inclined toward the operation unit  500 , so that a user standing in front of the operation unit  500  can be detected thereby. 
       FIG. 4  is a perspective view of the human detection sensor unit  600 . 
     The human detection sensor unit  600  includes a printed circuit board  620  on which the ultrasonic sensor  610  is mounted, a pedestal  630  to which the printed circuit board  620  is fixed, a horn  640  for controlling directionality of the ultrasonic wave output from the ultrasonic sensor  610 , and a shock-absorbing member (sponge)  650 . Hereinafter, the printed circuit board  620  is also referred to as “board  620 ” appropriate. The ultrasonic sensor  610  is surface mount device (SMD) type ultrasonic sensor mounted on a surface of the board  620 . The ultrasonic sensor  610  includes a piezoelectric element which outputs an ultrasonic wave according to an applied voltage and outputs an electric signal corresponding to a received ultrasonic wave. 
     The pedestal  630  is a member used for arranging the board  620  on which the ultrasonic sensor  610  is mounted to be inclined toward the operation unit  500 . 
       FIG. 5  is a block diagram illustrating devices mounted on the board  620 . 
     The board  620  is a two-layered glass epoxy board. As illustrated in  FIG. 5 , the ultrasonic sensor  610 , a driving circuit  621 , a receiving resistor  622 , an amplification circuit  623 , a detection circuit  624 , and a threshold circuit  625  are mounted on the board  620 . The driving circuit  621  receives a driving pulse P output from the CPU  221  to vibrate the piezoelectric element of the ultrasonic sensor  610 . The receiving resistor  622  converts sound pressure of the ultrasonic wave received by the ultrasonic sensor  610  to voltage. The amplification circuit  623  amplifies the converted voltage. A voltage wave form V 1  amplified by the amplification circuit  623  is demodulated by the detection circuit  624 . Then, a signal V 2  output from the detection circuit  624  is compared to a voltage level set to the threshold circuit  625 . Then, the signal is output as an analog signal S from the threshold circuit  625  to the microcomputer  514 . The board  620  on which the ultrasonic sensor  610  is mounted is arranged so as to be inclined toward the operation unit  500  by approximately 15 degrees from a front face of the MFP  10 . In addition, the angle of the board  620  is not limited to the above-described 15 degrees, and may be adjusted based on a positional relationship between the operation unit  500  and the human detection sensor unit  600 . More specifically, the angle is smaller when a distance between the operation unit  500  and the human detection sensor unit  600  is shorter, and the angle is larger when a distance therebetween is longer. 
     The horn  640  is a member for controlling directionality of the ultrasonic wave to prevent diffusion of the ultrasonic wave output from the ultrasonic sensor  610 . It is difficult to limit the detection area without using the horn  640 . An opening portion  644  of the horn  640  on a side of the cover member  301  (see  FIG. 9 ) has a square shape with a size of approximately 13 mm×13 mm, and the size of the opening portion  644  is gradually narrowed down toward the ultrasonic sensor  610  (i.e., inverted conical shape). In addition, an opening size of the opening portion  644  of the horn  640  is not limited to the above-described size. 
     The shock-absorbing member  650  is arranged between the horn  640  and a cover member  301  (see  FIG. 7C ) described below. The shock-absorbing member  650  fills a space between the horn  640  and the cover member  301 , so that the ultrasonic wave does not leak through the space between the horn  640  and the cover member  301 . 
       FIG. 6  is a diagram illustrating the human detection sensor unit  600  before and after the horn  640  is attached thereto. 
     The human detection sensor unit  600  is fixed to a frame plate (fixing member)  700  provided in the scanner unit  300 . The board  620  is fixed to the pedestal  630  with a screw  626 . 
     The horn  640  is arranged on a side of the board  620  where the ultrasonic sensor  610  is mounted. The horn  640  is fixed to the pedestal  630 . The shock-absorbing member  650  is attached to an end portion of the horn  640  on a side of the cover member  301 . The shock-absorbing member  650  is arranged between the horn  640  and the cover member  301 , so as to fill the space between the horn  640  and the cover member  301 . With this configuration, the ultrasonic wave output from the ultrasonic sensor  610  can be suppressed from leaking through the space between the horn  640  and the cover member  301 . Further, because the shock-absorbing member  650  is made of sponge, vibration of the horn  640  can be suppressed from propagating to the cover member  301 . 
       FIGS. 7A, 7B, and 70  are diagrams respectively illustrating a front view, a top view, and a cross-sectional view of the human detection sensor unit  600 .  FIG. 7A  is a front view of a portion of the scanner unit  300  where the human detection sensor unit  600  is arranged,  FIG. 7B  is a top view of the portion of the scanner unit  300  where the human detection sensor unit  600  is arranged, and  FIG. 70  is a cross-sectional view taken along a line A-A in  FIG. 7B . 
     if the human detection sensor unit  600  is arranged at a position touchable by the user, the user&#39;s finger may touch the ultrasonic sensor  610  or the board  620  to cause malfunction of the ultrasonic sensor  610  or the board  620 . Therefore, as illustrated in  FIG. 7A , the human detection sensor unit  600  is covered by the cover member  301  of the scanner unit  300 . The cover member  301  is provided with a plurality of slits  302  for outputting the ultrasonic wave output from the ultrasonic sensor  610  to the outside of the apparatus or receiving a reflected wave of the ultrasonic wave reflected from the outside thereof. Each of the slits  302  has an elongated hole shape extending in horizontal direction in the present exemplary embodiment, the three slits  302  are aligned in a vertical direction. Each of the slits  302  has a length (i.e., breadth) in the horizontal direction greater than the opening size of the horn  640  in the horizontal direction. 
       FIG. 8  is a diagram illustrating a plan view of the board  620  on which the ultrasonic sensor  610  is mounted. 
     The ultrasonic sensor  610  is mounted on the board  620 . The above-described driving circuit  621 , the receiving resistor  622 , the amplification circuit  623 , the detection circuit  624 , and the threshold circuit  625  are mounted on the board  620  (they are not illustrated in  FIG. 8 ). A screw hole (through-hole)  620   a  through which a screw  626  for fixing the board  620  to the pedestal  630  passes is formed on the board  620 . In other words, a portion of the board  620  where the screw hole  620   a  is formed is a contact position (first position) of the pedestal  630  and the board  620 . The screw  626  is fixed to the pedestal  630  via the screw hole  620   a.  Further, a cutout portion  620   b  for latching a claw portion  631  formed on the pedestal  630  is formed on an opposite end portion of the screw hole  620   a  of the board  620 . 
     Furthermore, slits  620   c  and  620   d  are formed on both sides of the ultrasonic sensor  610  mounted on the board  620 . The slit  620   c  is formed at a position between the ultrasonic sensor  610  and the screw hole  620   a  on the board  620 . The slit  620   c  is formed on a straight line Li that connects a position (a hatched region in  FIG. 8 ) where the ultrasonic sensor  610  is mounted on the board  620  and a position (a shading region in  FIG. 8 ) where the board  620  is in contact with the pedestal  630 . Further, the slit  620   d  is formed at a position between the ultrasonic sensor  610  and the cutout portion  620   b  on the board  620 . The slit  620   d  is formed on a straight line L 2  that connects a position where the ultrasonic sensor  610  is mounted on the board  620  and a position (i.e., cutout portion  20   b ) where the board  620  is in contact with the pedestal  630 . 
     The slit  620   c  has a length in the lengthwise direction (Y-direction in  FIG. 8 ) longer than a length of the ultrasonic sensor  610  in the Y-direction. Further, the slit  620   d  has a length in the lengthwise direction (Y-direction in  FIG. 8 ) longer than the length of the ultrasonic sensor  610  in the Y-direction. The lengthwise direction (Y-direction) of the slit  620   c  is a direction orthogonal to a lengthwise direction (X-direction in  FIG. 8 ) of the board  620 . Further, the lengthwise direction (Y-direction) of the slit  620   d  is a direction orthogonal to the lengthwise direction (X-direction in  FIG. 8 ) of the board  620 . 
     Furthermore, an L-shaped slit  620   e  is formed at a position between the ultrasonic sensor  610  and the screw hole  620   a  on the board  620 . The slit  620   e  is formed so as to surround the screw hole  620   a  Similar to the slit  620   c,  the slit  620   e  is also formed at a position between the ultrasonic sensor  610  and the screw hole  620   a  on the board  620 . The slit  620   e  is formed on the straight line L 1 . 
     The slit  620   c  is formed on a side (one side) close to the ultrasonic sensor  610  from a central position between the hatched region and the shaded region in  FIG. 8 , whereas the slit  620   e  is formed on a side (another side) close to the screw hole  620   a  from the central position. 
     Because the slits  620   c,    620   d,  and  620   e  are formed on the board  620 , vibration of the ultrasonic sensor  610  can be prevented from propagating to the other members (i.e., the frame plate  700  and the pedestal  630 ) through the screw  626  and the claw portion  631 . In addition, a metallic screw  626  is used when the board  620  and the frame plate  700  have to be connected electrically. However, when the board  620  and the frame plane  700  do not have to be connected electrically, a plastic screw  626  may be used. If the plastic screw  626  is used, vibration of the ultrasonic sensor  610  can be prevented from propagating to the other members through the screw  626 . 
     Further, a boss hole  620   f  through which a boss  643  provided on the horn  640  passes is formed on the board  620  according to the present exemplary embodiment. The boss  643  provided on the horn  640  fits into the boss hole  620   f,  so that a relative position of the horn  640  with respect to the ultrasonic sensor  610  can be fixed with high precision. A shock-absorbing member  651  contacts a region indicated by hatched lines in  FIG. 8 . The shock-absorbing member  651  contacts a region where the slits  620   c  and  620   d  of the board  620  are formed. 
       FIGS. 9A, 9B, 90, and 9D  are diagrams illustrating a detailed structure of the horn  640 .  FIG. 9A  is a front view of the horn  640 ,  FIG. 9B  is a cross-sectional view taken along a line B-B in  FIG. 9A ,  FIG. 9C  is a rear view of the horn  640 , and  FIG. 9D  is a cross-sectional view taken along a line C-C in  FIG. 9A . 
     The horn  640  is a member for controlling directionality of the ultrasonic wave transmitted from the ultrasonic sensor  610  mounted on the board  620 . As illustrated in  FIGS. 9B and 9D , the horn  640  is formed into an inverted conical shape, so that an opening size thereof is gradually narrowed down toward the ultrasonic sensor  610 . In the present exemplary embodiment, although an inner face  645  of the horn  640  consists of a plurality of planar faces, the inner face  645  may be formed of a curved face. The horn  640  is provided with latching portions  641  and  642  for fixing the horn  640  to the pedestal  630 . The horn  640  is fixed to the pedestal  630  without being fixed to the board  620 . By fixing the horn  640  to the pedestal  630 , vibration of the ultrasonic sensor  610  is suppressed from propagating to the horn  640 . In addition, the horn  640  may be fixed to the board  620  as long as vibration of the horn  640  can be sufficiently suppressed by the slits  620   c,    620   d,  and  620   e  provided on the board  620 . 
     Further, as illustrated in  FIGS. 9B and 9C , two bosses  643  for fixing the position of the horn  640  with respect to the ultrasonic sensor  610  are formed on the horn  640 . In order to output the ultrasonic wave from the ultrasonic sensor  610  with directionality, it is preferable that the horn  640  is arranged adjacent to the ultrasonic sensor  610 . However, if the horn  640  is fixed to the board  620  on which the ultrasonic sensor  610  is mounted, vibration of the ultrasonic sensor  610  propagates to the horn  640 . Further, the horn  640  disturbs the vibration of the ultrasonic sensor  610 . 
       FIGS. 10A and 10B  are diagrams illustrating shock-absorbing members attached to the horn  640 .  FIG. 10A  is a diagram illustrating a shock-absorbing member attached to the horn  640  on a side of the cover member  301 , and  FIG. 10B  is a diagram illustrating a shock-absorbing member attached to the horn  640  on a side of the board  620 . 
     As illustrated in  FIG. 10A , a shock-absorbing member  650  is arranged between the horn  640  and the cover member  301 . The shock-absorbing member  650  is made of sponge. Further, the shock-absorbing member  650  has an opening larger than the opening of the horn  640  on the side of the cover member  301 . 
     As illustrated in  FIG. 10B , the shock-absorbing member  651  is arranged between the horn  640  and the board  620 . Similar to the shock-absorbing member  650 , the shock-absorbing member  651  is made of sponge. Further, the shock-absorbing member  651  has an opening larger than the opening of the horn  640  on the side of the board  620 . 
     It is desirable for the shock-absorbing members  650  and  651  to be made of a material having a high sound absorption property and a high sound insulation property. As a material having the high sound absorption property, for example, porous material having a rough surface, an inner portion of which has a bubble-shaped cell structure, i.e., glass wool, rock wool, or flexible urethane form, may desirably be used for the shock-absorbing members  650  and  651 . Further, as a material having the high sound insulation property, a flexible material having a small compression stress, i.e., sponge or rubber, which comfortably fits into an irregular-shaped adherend, may be used for the shock-absorbing members  650  and  651 . 
     Further, it is desirable for the shock-absorbing members  650  and  651  to be made of a material having a high vibration absorption property and a high vibration damping property. As a material having the high vibration absorption property and the high vibration damping property, for example, an elastic damping member such as rubber or sponge may be used for the shock-absorbing members  650  and  651 . 
     in the present exemplary embodiment, a vibration damping material such as “Eptsealer” manufactured by Nitto Denko Corporation or “CalmFlex” manufactured by Inoac Corporation is used for the shock-absorbing members  650  and  651 . 
       FIGS. 11A and 11B  are cross-sectional diagrams of the human detection sensor unit  600 .  FIG. 11A  is an exploded sectional view of the human detection sensor unit  600 , and  FIG. 11B  is a cross-sectional view of the human detection sensor unit  600 . 
     As illustrated in  FIG. 11A , the shock-absorbing member  651  is not compressed when the horn  640  has not yet fixed to the pedestal  630 . Further, as illustrated in  FIG. 11A , the shock-absorbing member  650  is not compressed when the cover member  301  has not yet attached in front of the horn  640 . 
     When the horn  640  is fixed to the pedestal  630 , the shock-absorbing member  651  is compressed, so as to fill the space between the board  620  and the horn  640 . With this configuration, the ultrasonic wave output from the ultrasonic sensor  610  can be suppressed from leaking through the space between the board  620  and the horn  640 . Further, because the board  620  is brought into contact with the horn  640  via the shock-absorbing member  651 , vibration of the ultrasonic sensor  610  can be suppressed from propagating to the horn  640  from the board  620 . 
     Furthermore, when the cover member  301  is attached thereto, the shock-absorbing member  650  is compressed to fill the space between the cover member  301  and the horn  640 . With this configuration, the ultrasonic wave output from the ultrasonic sensor  610  can be suppressed from leaking through the space between the cover member  301  and the horn  640 . Further, because the horn  640  is brought into contact with the cover member  301  via the shock-absorbing member  650 , vibration of the ultrasonic sensor  610  can be suppressed from propagating to the cover member  301  from the horn  640 . 
       FIG. 12  is a diagram illustrating a state where the user approaches the MFP  10  from the front side thereof. In  FIG. 12 , a diagram in an upper row illustrates a positional relationship between the MFP  10  and the user viewed from the side, a diagram in a middle row illustrates the positional relationship between the MFP  10  and the user viewed from the above, and a diagram in a lower row illustrates a detection result of the ultrasonic sensor  610 . Further, in  FIG. 12 , respective states (t 1 ) to (t 4 ) are illustrated and sequentially arranged from the left. In  FIGS. 13 and 14  described below, respective states (t 1 ) to (t 4 ) are illustrated and arranged in a similar manner. 
     As illustrated in the lower row in  FIG. 12 , a wave form as a detection result of the ultrasonic sensor  610  includes a wave form of an oscillated ultrasonic wave and a wave form of a reflected wave. The ultrasonic sensor  610  according to the present exemplary embodiment oscillates for a predetermine period to output the ultrasonic wave. Therefore, the oscillation for outputting the ultrasonic wave has an influence on the initial stage of the detection result of the ultrasonic sensor  610 . Then, the ultrasonic sensor receives a reflected wave of the ultrasonic wave reflected on the human or the object. The ultrasonic sensor  610  outputs the sound pressure intensity of the reflected wave as a voltage value (this voltage value is taken as a detection vibration amplitude V). Although the above-described wave form caused by the oscillation does not appear if the ultrasonic sensor  610  is separately configured of an output unit for outputting the ultrasonic wave and a receiving unit for receiving the reflected wave, a wave form similar to the wave form illustrated in  FIG. 12  is acquired because the ultrasonic wave output from the output unit is directly received by the receiving unit. 
     The state (t 1 ) in  FIG. 12  illustrates a state where the user enters an area detectable by the ultrasonic sensor  610 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 1  greater than a predetermined threshold vibration amplitude Vth 2  is generated when a time D 1  has passed after oscillation of the ultrasonic wave. The time D 1  is a time taken for the output ultrasonic wave to return after reflecting on the user, so that the time D 1  corresponds to a distance between the MFP  10  and the user. Hereinafter, the time D 1  .e., time taken for detecting a reflected wave after outputting a direct wave) is treated as a distance D 1  as appropriate. In the present exemplary embodiment, it is determined that a person exists in a detection area A 1  when a detection vibration amplitude V greater than the threshold vibration amplitude Vth 2  is detected in a distance longer than a predetermined distance Dth (hereinafter, referred to as “threshold distance Dth”). Further, it is determined that a person exists in a detection area A 2  when a detection vibration amplitude V greater than a threshold vibration amplitude Vth 1  (Vth 1 &gt;Vth 2 ) is detected in a distance shorter than the threshold distance Dth. When a user exists in a position far from the ultrasonic sensor  610 , a reflected wave returning from the faraway place is diffused, so that not all of the reflected wave can be received. 
     Therefore, the detection vibration amplitude is attenuated and reduced. At t 1  in  FIG. 12 , because the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not generated in a distance shorter than the threshold distance Dth, the MFP  10  remains in a sleep mode. 
     The state (t 2 ) in  FIG. 12  illustrates a state where the user moves toward the detection area A 2 , but has not entered the detection area A 2 . 
     As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 2  greater than the threshold vibration amplitude Vth 2  is output at a distance D 2  that is shorter than the distance D 1  and longer than the threshold distance Dth. The detection vibration amplitude V 2  is greater than the detection vibration amplitude V 1 . In the state (t 2 ) in  FIG. 12 , the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not generated in a distance shorter than the threshold distance Dth, so that the MFP  10  remains in a sleep mode. 
     The state t 3  in  FIG. 12  illustrates a state where the user enters the detection area A 2 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 3  greater than the threshold vibration amplitude Vth 1  is output in a distance D 3  shorter than the threshold distance Dth. In the state (t 3 ) in  FIG. 12 , although the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is generated in a distance shorter than the threshold distance Dth, the MFP  10  remains in a sleep mode because the detection vibration amplitude V is not continuously generated for a predetermined period. 
     The state (t 4 ) in  FIG. 12  illustrates a state where the user stays within the detection area A 2 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 4  greater than the threshold vibration amplitude Vth 1  is output in a distance D 4  shorter than the threshold distance Dth. When the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is continuously generated for a predetermined period in a distance shorter than the threshold distance Dth, the MFP  10  cancels the sleep mode and shifts to the stand-by mode. example, a predetermined period may be 300 ms. 
       FIG. 13  is a diagram illustrating a state where the user approaches the MFP  10  from the side. 
     A state (t 1 ) in  FIG. 13  illustrates a state where the user enters an area detectable by the ultrasonic sensor  610 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 5  greater than the threshold vibration amplitude Vth 1  is output in a distance D 5  shorter than the threshold distance Dth. At this point, the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not continuously generated for a predetermined period (e.g., 300 ms) in a distance shorter than the threshold distance Dth, so that the MFP  10  remains in the sleep mode. 
     A state (t 2 ) in  FIG. 13  illustrates a state where the user moves inside the detection area A 2 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 6  greater than the threshold vibration amplitude Vth 1  is output in a distance D 6  shorter than the threshold distance Dth. Similarly, at this point, the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not continuously generated for a predetermined time (e.g., 300 ms) in a distance shorter than the threshold distance Dth, so that the MFP  10  remains in the sleep mode. 
     A state (t 3 ) in  FIG. 13  illustrates a state where the user arrives at the front of the MFP  10 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 7  greater than the threshold vibration amplitude Vth 1  is output in a distance D 7  shorter than the threshold distance Dth. Similarly, at this point, the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not continuously generated for a predetermined time (e.g., 300 ms)) in a distance shorter than the threshold distance Dth, so that the MFP  10  remains in the sleep mode. 
     The state (t 4 ) in  FIG. 13  illustrates a state where the user stays in front of the MFP  10 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 8  greater than the threshold vibration amplitude Vth 1  is output in a distance D 8  shorter than the threshold distance Dth. At this point, the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is continuously generated for a predetermined time (e.g., 300 ms) in a distance shorter than the threshold distance Dth, so that the MFP  10  cancels the sleep mode and returns to the stand-by mode. 
       FIG. 14  is a diagram illustrating a state where a person passes in front of the MFP  10 . 
     The state (t 1 ) in  FIG. 14  illustrates a state where the user enters an area detectable by the ultrasonic sensor  610 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 9  greater than the threshold vibration amplitude Vth 1  is output in a distance D 9  shorter than the threshold distance Dth. At this point, the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not continuously generated for a predetermined time (e.g., 300 ms) in a distance shorter than the threshold distance Dth, so that the MFP  10  remains in the sleep mode. 
     A state (t 2 ) in  FIG. 14  illustrates a state where person moves inside the detection area A 2 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude  10  greater than the threshold vibration amplitude Vth 1  is output in a distance D 10  shorter than the threshold distance Dth. Similarly, at this point, the detection vibration amplitude V greater than the threshold vibration amplitude Vth 1  is not continuously generated for a predetermined time (e.g., 300 ms) in a distance shorter than the threshold distance Dth, so that the MFP  10  remains in the sleep mode. 
     A state (t 3 ) in  FIG. 14  illustrates a state where the person moves outside the detection area A 2 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 11  greater than the threshold vibration amplitude Vth 1  is output in a distance D 11  longer than the threshold distance Dth. Because the detection vibration amplitude V 11  greater than the threshold vibration amplitude Vth 1  is not generated in a distance shorter than the threshold distance Dth, the MFP  10  remains in a sleep mode. 
     A state (t 4 ) in  FIG. 14  illustrates a state where the person moves outside the detection area A 1 . As a detection result of the ultrasonic sensor  610 , a detection vibration amplitude V 12  smaller than the threshold vibration amplitude Vth 1  is output in a distance D 12  longer than the threshold distance Dth. Because the detection vibration amplitude V 11  greater than the threshold vibration amplitude Vth 1  is not generated in a distance shorter than the threshold distance Dth, the MFP  10  remains in a sleep mode. When the person starts moving away from the place (i.e., a position in front of the operation unit  500 ) where the user operates the MFP  10  as illustrated in the state (t 4 ) in  FIG. 14 , the detection distance D gradually becomes longer, and the detection vibration amplitude V gradually becomes smaller. 
       FIG. 15  is a flowchart illustrating return algorithm based on a detection result of the ultrasonic sensor  610 . The microcomputer  514  of the MFP  10  executes respective steps in  FIG. 15  according to a program. 
     In step S 1001 , the microcomputer  514  acquires a detection result of the ultrasonic sensor  610  at a predetermined interval (e.g., 100 ms). In step S 1002 , based on the detection result acquired from the ultrasonic sensor  610 , the microcomputer  514  calculates a distance D at which a detection vibration amplitude V greater than a threshold vibration amplitude Vth 1  is generated. Then, in step S 1003 , the microcomputer  514  determines whether the calculated distance D is equal to or longer than a predetermined threshold distance Dth. 
     If the microcomputer  514  determines that the calculated distance D is equal to or longer than the predetermined threshold distance Dth (YES in step S 1003 ), the processing proceeds to step S 1004 . In step S 1004 , the microcomputer  514  increments a count C. Next, in step S 1005 , the microcomputer  514  determines whether the count C is equal to or greater than a predetermined value Ct (e.g., Ct=4). If the microcomputer  514  determines that the count C is equal to or greater than the predetermined value Ct (YES in step S 1005 ), the processing proceeds to step S 1006 . In step S 1006 , the microcomputer  514  outputs an interrupt signal C to the power source control unit  211 . The power source control unit  211  receives the interrupt signal C and makes the MFP  10  return to a stand-by mode from a sleep mode. Then, in step S 1007 , the microcomputer  514  clears the count C. 
     In addition, in step S 1003 , if the microcomputer  514  determines that the calculated distance C is shorter than the threshold distance Dth (NO in step S 1004 ), the processing proceeds to step S 1008 . In step S 1008 , the microcomputer  514  clears the count C. 
     Modification Example 
       FIGS. 16A, 16B, and 16C  are diagrams illustrating modification examples of a board on which an ultrasonic sensor is mounted. 
     In the above-described exemplary embodiment, although a configuration in which a plurality of slits is provided on the board  620  has been described as an example, the number of slits may be one. More specifically, as illustrated in  FIG. 16A , on a board  1620  as a modification example 1, an L-shaped slit  1620   e  is formed at a position in the vicinity of a screw hole  620   a.    
     Further, in the above-described exemplary embodiment, although a configuration in which the slits  620   c  and  620   d  are formed on both sides of the ultrasonic sensor  610  has been described as an example, slits may be provided so as to surround the ultrasonic sensor  610 . More specifically, as illustrated in  FIG. 16B , on a board  2620  as a modification example  2 , four slits  2620   e  are formed so as to surround the ultrasonic sensor  610 . 
     Furthermore, in the above-described exemplary embodiment, although a single ultrasonic sensor  610  outputs and receives the ultrasonic wave, the ultrasonic wave may be output and received by different devices. In this case, as illustrated in  FIG. 160 , a device (ultrasonic wave transmission unit)  3610  for outputting the ultrasonic wave and a device (ultrasonic wave receiving unit)  3611  receiving the ultrasonic wave are mounted on a board  3620 . Then, a slit  3620   e  is formed on a board  3620 , at a position between the devices  3610  and  3611 . 
     Other Embodiments 
     Embodiment(s) of the present invention 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 (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 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 aspects of the present invention have been described with reference to exemplary embodiments, it is to be understood that aspects of the invention are not limited to the disclosed exemplary 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. 2016-150105, filed Jul. 29, 2016, which is hereby incorporated by reference herein in its entirety.