Patent Publication Number: US-2020290184-A1

Title: Machining system, fitting device, and method for controlling fitting device

Description:
TECHNICAL FIELD 
     The present invention relates to a machining system including a target device and a fitting device for fitting a fixing member in the target device. The present invention also relates to the fitting device and a method for controlling the fitting device. 
     BACKGROUND ART 
     Patent Literature 1, for example, discloses a double floor installation method involving emitting a laser beam from a laser generator and receiving the laser beam, measuring a positional relationship in terms of height relative to the level of the received laser beam, and adjusting the level of a floor being installed based on a difference between a predetermined level and the measured positional relationship in terms of height. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     Japanese Patent Application Laid-Open Publication No. 9-268740 
     SUMMARY OF INVENTION 
     Technical Problem 
     Incidentally, a fixing member (for example, a small screw, a large screw, or a nail) is fitted in a through hole of a constituent part for fixing the constituent part, but the fixing member is sometimes fitted with an axial direction thereof oblique to a central axis of the through hole. In such a situation, the fixing member is unsuccessfully fitted in the through hole, or is successfully fitted in the through hole but fails to reliably fix the constituent part. 
     For example, a worker fixes a constituent part by fitting a screw in the constituent part using an electric screwdriver as a fitting device. In a situation in which the constituent part is a large constituent part, such as a housing of a large liquid crystal display panel, the worker may not be able to see a screw receiving site of the constituent part from the front while working, because the constituent part is difficult to move or working space is limited. In such a situation, it is not easy for the worker to fit the screw in the constituent part while holding the screw in its correct orientation. 
     The present invention has been made in view of the circumstances described above, and an object thereof is to provide a machining system capable of preventing a fixing member from being fitted in a tilted manner, a fitting device, and a method for controlling the fitting device. 
     Solution to Problem 
     A machining system according to an aspect of the present invention includes a target device and a fitting device. The target device has a housing and a light source disposed within the housing. The fitting device fits a fixing member in the housing. The target device has at least one light exit opening. The at least one light exit opening is provided in the housing and lets out light emitted by the light source to an exterior of the housing. The fitting device includes a fitting mechanism, at least one light receiver, and a drive controller. The fitting mechanism is driven to fit the fixing member in the housing. The at least one light receiver receives the emitted light that has exited through the at least one light exit opening. The drive controller controls driving of the fitting mechanism based on a result of light reception by the at least one light receiver. 
     A fitting device according to another aspect of the present invention fits a fixing member in a housing of a target device. The target device has the housing, a light source, and at least one light exit opening. The light source is disposed within the housing. The at least one light exit opening is provided in the housing and lets out light emitted by the light source to an exterior of the housing. The fitting device includes a fitting mechanism, at least one light receiver, and a drive controller. The fitting mechanism is driven to fit the fixing member in the housing. The at least one light receiver receives the emitted light that has exited through the at least one light exit opening. The drive controller controls driving of the fitting mechanism based on a result of light reception by the at least one light receiver. 
     A method for controlling a fitting device according to another aspect of the present invention is for fitting a fixing member in a housing of a target device. The target device has the housing, a light source, and at least one light exit opening. The light source is disposed within the housing. The at least one light exit opening is provided in the housing and lets out light emitted by the fight source to an exterior of the housing. The method includes receiving and controlling. In the receiving, the emitted light that has exited through the at least one light exit opening is received. In the controlling, driving of a fitting mechanism for fitting the fixing member is controlled based on a result of the receiving of the emitted light. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to prevent a fixing member from being fitted in a tilted manner. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating a machining system according to Embodiment 1. 
         FIG. 2  is a diagram illustrating partial external appearance of a television receiver according to Embodiment 1. 
         FIG. 3  is a partial cross-sectional view illustrating a portion of a cross-section taken along line A-A in  FIG. 2 . 
         FIG. 4  is a diagram illustrating an electric screwdriver according to Embodiment 1 fitting a screw in the television receiver. 
         FIG. 5  is a functional block diagram illustrating a configuration of main elements of the electric screwdriver according to Embodiment 1. 
         FIG. 6  is a flowchart of a process that is performed by a controller of the electric screwdriver according to Embodiment 1. 
         FIG. 7  is a functional block diagram illustrating a configuration of main elements of an electric screwdriver according to Embodiment 2. 
         FIG. 8  is a diagram illustrating a configuration of a notification section of the electric screwdriver according to Embodiment 2. 
         FIG. 9  is a flowchart of a process that is performed by a controller of the electric screwdriver according to Embodiment 2. 
         FIG. 10  is a functional block diagram illustrating a configuration of main elements of an electric screwdriver according to Embodiment 3. 
         FIG. 11  is a diagram illustrating a relationship between angle of incidence and angle of refraction of emitted light received by a light receiver. 
         FIG. 12  is a flowchart of a process that is performed by a controller of the electric screwdriver according to Embodiment 3. 
         FIG. 13  is a diagram illustrating partial external appearance of a television receiver according to Embodiment 4. 
         FIG. 14  is a diagram illustrating an electric screwdriver according to Embodiment 4 fitting a screw in the television receiver. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes embodiments of the present invention in detail based on the drawings using an example of a machining system in which a target device is a television receiver having a liquid crystal display panel and a fitting device is an electric screwdriver. 
     Embodiment 1 
       FIG. 1  is a conceptual diagram illustrating a machining system  1  according to Embodiment 1. The machining system  1  includes a television receiver  100  and an electric screwdriver  10  for performing screwing on the television receiver  100 . 
     The television receiver  100  is for example a large television receiver. The television receiver  100  includes a rectangular liquid crystal display panel  2  for displaying images on a display surface thereof, which is a front surface. A periphery of the liquid crystal display panel  2  is surrounded by a bezel  7 . 
     In the following description, a left-right direction in a front view of the television receiver  100  is referred to as a device lateral direction, and an up-down direction in the front view of the television receiver  100  is referred to as a device longitudinal direction. A thickness direction of the television receiver  100 , which in other words is a direction from a front to a back or the back to the front of the television receiver  100 , is referred to as a device thickness direction. 
       FIG. 2  is a diagram illustrating partial external appearance of the television receiver  100  according to Embodiment 1.  FIG. 2  shows the television receiver  100  viewed from a direction indicated by an arrow in  FIG. 1 .  FIG. 3  is a partial cross-sectional view illustrating a portion of a cross-section taken along line A-A in  FIG. 2 . 
     As illustrated in  FIG. 3 , an optical sheet  3 , a light guide plate  5 , and a reflective sheet  8  are disposed in the stated order on a back surface (a surface opposite to the display surface) of the liquid crystal display panel  2 , and the light guide plate  5  and the reflective sheet  8  are housed in a backlight chassis  9 . Light sources  16  are provided so as to each face a side surface of the light guide plate  5 . Hereinafter, a surface of each of the optical sheet  3 , the light guide plate  5 , and the reflective sheet  8  that is toward the liquid crystal display panel  2  is referred to as a front surface thereof. Likewise, a surface of each of the optical sheet  3 , the light guide plate  5 , and the reflective sheet  8  that is distant from the liquid crystal display panel  2  is referred to as a back surface thereof. 
     As illustrated in  FIGS. 1 to 3 , the bezel  7  has a rectangular frame-like shape and opens toward both a front side and a back side of the television receiver  100 . The bezel  7  may be a segmented bezel, which is an assembly of a plurality of components, or a one-component bezel. The bezel  7  may also be made from a metal or a resin. The following describes the bezel  7  using an example in which the bezel  7  is a metal segmented bezel to facilitate explanation. 
     As illustrated in  FIGS. 2 and 3 , the bezel  7  has side walls  72  elongated in the device longitudinal direction. At least one of the side walls  72  has a plurality of screw holes  73  that respectively receive fitting of screws S for fixing the bezel  7  to the backlight chassis  9 . The screw holes  73  penetrate the side wall  72  in a thickness direction thereof and are for example aligned in the device longitudinal direction. The bezel  7  is fixed to the backlight chassis  9  through the screws S being fitted in the screw holes  73  and screw holes  92  described below. 
     The side wall  72  of the bezel  7  also has light exit openings  74  for letting out light emitted by the light sources  16 . The light exit openings  74  are provided in the vicinity of and in one-to-one correspondence with the screw holes  73 . The light exit openings  74  penetrate the side wall  72  at right angle to a plane of the side wall  72  and are for example smaller than the screw holes  73 , According to the present embodiment, each of the light exit openings  74  and the corresponding screw hole  73  are in alignment with each other in the device thickness direction. However, the arrangement is not limited thereto, and each of the light exit openings  74  and the corresponding screw hole  73  may be out of alignment with each other in the device thickness direction. 
     The backlight chassis  9  has a rectangular parallelepiped box-like shape with one open face and includes side walls  91  respectively facing the side walls  72  of the bezel  7  and covered by the side walls  72 . 
     As illustrated in  FIG. 3 , the bezel  7  includes a hollow rectangular framing portion  71  that covers a periphery of the display surface of the liquid crystal display, panel  2 . The framing portion  71  has a specific length based on an end of the backlight chassis  9  on an open face side (i.e., a front side) of the backlight chassis  9  and extends inward from the side walls  72 . 
     A cushioning member (not shown) is disposed between the framing portion  71  and the periphery of the display surface of the liquid crystal display panel  2 . The framing portion  71  holds the periphery of the display surface of the liquid crystal display panel  2  through the cushioning member with pressure in the device thickness direction. 
     The optical sheet  3  is disposed on the back surface of the liquid crystal display panel  2 . The light guide plate  5  is disposed such that the front surface thereof faces the back surface of the optical sheet  3  with a specific space therebetween. The reflective sheet  8  is disposed on the back surface of the light guide plate  5 . 
     The optical sheet  3  disposed on the back surface of the liquid crystal display panel  2  receives light emitted by the light sources  16  and guided by the light guide plate  5 , diffuses or condenses the light into more uniform light, and emits the uniform light toward the liquid crystal display panel  2 . The optical sheet  3  for example includes two diffusion sheets and one prism sheet disposed between the two diffusion sheets. 
     A holding member  4  that holds the optical sheet  3  is provided at a periphery portion of the back surface of the optical sheet  3 . The holding member  4  has an L-shaped cross-section. The holding member  4  also has a protruding portion protruding in a direction intersecting with the side wall  91  of the backlight chassis  9  (in a direction of a plane of the optical sheet  3 ). The protruding portion has an end in contact with the periphery portion of the back surface of the optical sheet  3  and supports the optical sheet  3 . 
     The light guide plate  5  diffuses light emitted by the light sources  16  and entering through the side surfaces thereof, and emits the diffused light toward the optical sheet  3  from the front surface thereof. The tight guide plate  5  is for example made of a milky white resin (such as acrylic resin or polycarbonate resin containing a diffusing agent as an additive. In a configuration in which point light sources such as LEDs are used as the light sources  16 , the light guide plate  5  diffuses light from each of the point light sources into uniform light and surface-emits the light from the front surface thereof. 
     The reflective sheet  8  has a rectangular shape corresponding to the shape of the light guide plate  5 , and the front surface of the reflective sheet  8  faces the back surface of the light guide plate  5 . 
     The backlight chassis  9  houses the light guide plate  5  and the reflective sheet  8  as mentioned above. The side walls  91  have the screw holes  92  in one-to-one correspondence with the screw holes  73  of the bezel  7  and light exit openings  93  in one-to-one correspondence with the light exit openings  74  of the bezel  7 . 
     The screw holes  92  penetrate the side walls  91  in a thickness direction thereof and have for example the same diameter as the screw holes  73 . The screw holes  92  are in positions that match positions of the screw holes  73  in the device lateral direction when the bezel  7  and the backlight chassis  9  are in a desired positional relationship (a positional relationship upon fixation). The light exit openings  93  also penetrate the side walls  91  at right angle to planes thereof and have for example the same diameter as the light exit openings  74 . The light exit openings  93  are in positions that match positions of the light exit openings  74  in the device lateral direction when the bezel  7  and the backlight chassis  9  are in the desired positional relationship (the positional relationship upon fixation). 
     Accordingly, a portion of the light emitted by the light sources  16  exits out of the television receiver  100  through the light exit openings  93  and the light exit openings  74 . The light that has exited through the light exit openings  74  and  93 , which in other words is light emitted from the television receiver  100  (emitted light L (see  FIG. 4 )), is received by the light receiver  11  of the electric screwdriver  10  as described below. The bezel  7  is fixed to the backlight chassis  9  through the screws S being fitted in the screw holes  73  and  92  (through holes). 
       FIG. 4  is a diagram illustrating the electric screwdriver  10  according to Embodiment 1 fitting a screw S in the television receiver  100 .  FIG. 5  is a functional block diagram illustrating a configuration of main elements of the electric screwdriver  10  according to Embodiment 1. The following describes the configuration of the electric screwdriver  10  according to Embodiment 1 with reference to  FIGS. 4 and 5 . 
     The electric screwdriver  10  includes the light receiver  11  that receives the emitted light L that has exited through the light exit openings  74  and  93  of the television receiver  100 , a fitting mechanism  13  that fits the screws S in the television receiver  100 , a controller  12  (see  FIG. 5 ) that controls driving of the fitting mechanism  13  based on a result of light reception by the light receiver  11 , a notification section  14 , and a switch  15 . 
     The light receiver  11  has a casing  114 . The casing  114  has an entrance opening  113  through which the emitted light L from the television receiver  100  enters the light receiver  11 . The casing  114  houses a convex lens  111  for condensing the emitted light L that has entered through the entrance opening  113  and a light receiving element  112  for receiving the emitted light L that has passed through the convex lens  111 . While the light receiving element  112  is receiving the emitted light L, the light receiver  11  according to the present embodiment transmits a signal indicating the light reception (referred to below as a “light reception signal”) to the controller  12 . 
     The fitting mechanism  13  includes components such as an electric motor, not shown, and a screwdriver bit D that supports a screw S being worked on. The fitting mechanism  13  is driven by a drive controller  121  described below to fit the screws S to the screw holes  73  and  92  of the television receiver  100 . Specifically, driven by the drive controller  121 , the fitting mechanism  13  rotates the electric motor. The rotation of the electric motor is transmitted to the screwdriver bit D through an output shall, and thus the screwdriver bit D rotates. As a result, the screw S being supported by the screwdriver bit D rotates to be fitted in one set of screw holes  73  and  92  of the television receiver  100 . 
     The controller  12  includes a central processing unit (CPU) and memory, not shown, and functions as the drive controller  121  and a notification controller  127  through the CPU executing various computer programs stored in the memory. 
     The drive controller  121  controls driving of the fitting mechanism  13 . According to the present embodiment, the drive controller  121  drives the fitting mechanism  13  when the controller  12  is receiving the light reception signal from the light receiver  11 , that is, when the light receiver  11  is receiving the emitted light L (when the light receiving element  112  is receiving the emitted light L). On the other hand, the drive controller  121  stops driving the fitting mechanism  13  when the controller  12  is not receiving the light reception signal from the light receiver  11 . Note that the drive controller  121  does not have to control driving of the fitting mechanism  13  while the switch  15  is not being depressed. 
     According to the present embodiment, the light exit openings  74  and  93  are disposed in specific positions on the side walls  72  and  91 , and the light receiver  11  is disposed in a specific position on the electric screwdriver  10  and in a specific orientation so that a central axis of the screw S being supported by the screwdriver bit D of the fitting mechanism  13  is at a desired angle (at substantially right angle, according to the present embodiment) to the side walls  72  and  91  when the light receiver  11  is receiving the emitted light L. 
     Thus, the central axis of the screw S is at substantially right angle to the side walls  72  and  91  when the light receiver  11  is receiving the emitted light L that has exited through the light exit opening  74  and  93 . Through the switch  15  being depressed, the electric screwdriver  10  in such a state drives the fitting mechanism  13  to fit the screw S in one set of screw holes  73  and  92 . Thus, according to the present embodiment, fitting of the screws S in the screw holes  73  and  92  is performed only when the central axis of the screw S being worked on is at substantially right angle to the side walls  72  and  91 . It is therefore possible to prevent the screws S from being fitted in a tilted manner. 
     Under the control of the notification controller  127 , the notification section  14  notifies a user of information about the result of light reception by the light receiver  11 . According to the present embodiment, the notification section  14  is for example a lamp such as a light emitting diode (LED) and notifies the user of whether or not the light receiver  11  is receiving the emitted light L through the lamp being on or off. For example, the notification controller  127  turns on the notification section  14  if the controller  12  is receiving the light reception signal from the light receiver  11  and turns off the notification section  14  if the controller  12  is not receiving the light reception signal. Thus, the user can easily know whether or not the screw S is in a desired orientation (whether or not the central axis of the screw S is at substantially right angle to the side walls  72  and  91 ) through the notification section  14  being on or off, and therefore can easily decide whether or not to adjust the orientation of the screw S by shifting the electric screwdriver  10 . 
       FIG. 6  is a flowchart of a process that is performed by the controller  12  of the electric screwdriver  10  according to Embodiment 1. 
     First, the controller  12  determines whether or not the switch  15  of the electric screwdriver  10  is being depressed (Step S 101 ). Upon the controller  12  determining that the switch  15  is not being depressed (NO in Step S 101 ), the drive controller  121  stops driving the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 104 ), and then the controller  12  waits until the switch  15  is depressed. 
     Upon determining that the switch  15  is being depressed (YES in Step S 101 ), the controller  12  determines whether or not the light receiver  11  is receiving the emitted light L (Step S 102 ). Specifically, the controller  12  determines that the light receiver  11  is receiving the emitted light L if the controller  12  is receiving the light reception signal from the light receiver  11 . The notification controller  127  then turns on the notification section  14  if the light receiver  11  is receiving the emitted light L and turns off the notification section  14  if the light receiver  11  is not receiving the emitted light L. 
     Upon the controller  12  determining that the light receiver  11  is receiving the emitted light L (YES in Step S 102 ), the drive controller  121  starts driving the fitting mechanism  13  if the fitting mechanism  13  is yet to be driven (Step S 103 ). Thus, the screwdriver bit D and a screw S being supported by the screwdriver bit D are caused to rotate, and fitting of the screw S in one set of screw holes  73  and  92  of the television receiver  100  is started. The drive controller  121  continues to drive the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 103 ). Thereafter, the controller  12  advances the process to Step S 101  and re-determines whether or not the switch  15  is being depressed. 
     Upon the controller  12  determining that the tight receiver  11  is not receiving the emitted light L (NO in Step S 102 ), the drive controller  121  stops driving the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 104 ), and then the controller  12  advances the process to Step S 101  and re-determines whether or not the switch  15  is being depressed. 
     As described above, the electric screwdriver  10  according to the present embodiment drives the fitting mechanism  13  to fit the screw S in one set of screw holes  73  and  92  of the television receiver  100  when the tight receiver  11  is receiving the emitted fight L. When the light receiver  11  is receiving the emitted tight L, the central axis of the screw S is at substantially right angle to the side walls  72  and  91 . Thus, according to the present embodiment, fitting of the screws S in the screw holes  73  and  92  is performed only when the central axis of the screw S being worked on is at substantially right angle to the side walls  72  and  91 . It is therefore possible to prevent the screws S from being fitted in a tilted manner. 
     The electric screwdriver  10  according to the present embodiment notifies the user of whether or not the light receiver  11  is receiving the emitted tight L through the notification section  14  being on or off Thus, the user can easily know whether or not the screw S is in a desired orientation, and therefore can easily decide whether or not to adjust the orientation of the screw S by shifting the electric screwdriver  10 . 
     Embodiment 2 
     A machining system  1  according to Embodiment 2 has a similar configuration to the machining system  1  according to Embodiment 1 other than the configuration of the controller  12  and the notification section  14  of the electric screwdriver  10 . The following mainly describes differences between Embodiments 2 and 1.  FIG. 7  is a functional block diagram illustrating a configuration of main elements of an electric screwdriver  10  according to Embodiment 2. 
     According to Embodiment 2, a controller  12  of the electric screwdriver  10  functions as an intensity measurement section  125  and an intensity determination section  126  in addition to functioning as a drive controller  121  and a notification controller  127  through a CPU executing various computer programs stored in memory. The memory of the controller  12  for example stores therein data indicating a specific range of optical intensity of emitted light L that has entered a convex lens  111  (referred to below as a “specific intensity range”). 
     When the controller  12  receives a light reception signal from a light receiver  11 , the intensity measurement section  125  measures the optical intensity of the received emitted light L, which in other words is the optical intensity of the emitted light L received by the light receiver  11 . The intensity measurement section  125  for example measures the optical intensity of the received emitted light L using an optical intensity sensor. 
     The intensity determination section  126  determines whether or not the optical intensity of the received emitted light L measured by the intensity measurement section  125  (referred to below as a “measured optical intensity”) is within the specific intensity range stored in the memory. According to the present embodiment, the specific intensity range is a range of greater than or equal to a specific threshold value. Specifically, the emitted light L whose optical intensity is within the specific intensity range can be considered to be directed at an approximately 0° angle of incidence relative to the convex lens  111  of the light receiver  11 . That is, the measured optical intensity being determined to be within the specific intensity range means that the emitted light L is entering the light receiver  11  (the convex lens  111 ) at an approximately 0° angle of incidence. 
     According to the present embodiment, the drive controller  121  drives a fitting mechanism  13  when the measured optical intensity is within the specific intensity range. Even when the light receiver  11  is receiving the emitted light L, however, the drive controller  121  does not drive the fitting mechanism  13  unless the measured optical intensity is within the specific intensity range. 
     According to the present embodiment, light exit openings  74  and  93  are disposed in specific positions on side walls  72  and  91 , and the light receiver  11  is disposed in a specific position on the electric screwdriver  10  and in a specific orientation so that a central axis of a screw S being supported by a screwdriver bit D of the fitting mechanism  13  is at a desired angle (at substantially right angle, according to the present embodiment) to the side walls  72  and  91  when the measured optical intensity is within the specific intensity range. 
     Thus, the central axis of the screw S is at substantially right angle to the side walls  72  and  91  when the measured optical intensity is within the specific intensity, range. Through a switch  15  being depressed, the electric screwdriver  10  in such a state drives the fitting mechanism  13  to fit the screw S in one set of screw holes  73  and  92 , Thus, according to the present embodiment, fitting of the screws S in the screw holes  73  and  92  is performed only when the central axis of the screw S being worked on is at substantially right angle to the side walls  72  and  91 . It is therefore possible to prevent the screws S from being fitted in a tilted manner. 
       FIG. 8  is a diagram illustrating a configuration of a notification section  14 A of the electric screwdriver  10  according to Embodiment 2. 
     The notification section  14 A has a plurality of lamps  141 A to  144 A, Which are for example LEDs. The lamps  141 A to  144 A respectively correspond to a plurality of ranges related to the optical intensity (referred to below as “optical intensity ranges”), which according to the present embodiment are the following four ranges: a first range, a second range, a second range, a third range, and a fourth range. The fourth range is the specific intensity range and corresponds to the lamp  144 A. The third range is a lower optical intensity range than the fourth range and corresponds to the lamp  143 A. The second range is a lower optical intensity range than the third range and corresponds to the lamp  142 A. The first range is a lower optical intensity range than the second range and corresponds to the lamp  141 A. On the electric screwdriver  10 , the word “Improper” is printed near the lamp  141 A, and the word “Proper” is printed near the lamp  144 A. 
     The intensity determination section  126  determines which of the optical intensity ranges (the first to fourth ranges) the measured optical intensity falls within. Hereinafter, this determination will be referred to as “intensity range determination”, Data indicating the optical intensity ranges other than the specific intensity range (the fourth range) are also stored in the memory of the controller  12 . The intensity determination section  126  refers to the optical intensity ranges stored in the memory to perform the intensity range determination. 
     The notification controller  127  turns on an appropriate one of the lamps  141 A to  144 A based on a result of the intensity range determination. Specifically, the notification controller  127  turns on the lamp  141 A upon the intensity determination section  126  determining that the measured optical intensity falls within the first range, turns on the lamp  142 A upon the intensity determination section  126  determining that the measured optical intensity falls within the second range, turns on the lamp  143 A upon the intensity determination section  126  determining that the measured optical intensity falls within the third range, and turns on the lamp  144 A upon the intensity determination section  126  determining that the measured optical intensity falls within the fourth range. Among the lamps  141 A to  144 A, the lamps other than the lamp turned on stay off. 
     The four lamps  141 A to  144 A each being on or off indicate how close to 0° the angle of incidence of the emitted light L is relative to the light receiver  11 . The closer to 0° the angle of incidence of the emitted light L is relative to the light receiver  11 , the greater the measured optical intensity is. According to the present embodiment, the central axis of the screw S being supported by the screwdriver bit D of the fitting mechanism  13  is at a desired angle (at substantially right angle) to the side walls  72  and  91  when the angle of incidence of the emitted light L relative to the light receiver  11  is approximately 0°, that is, when the measured optical intensity is within the specific intensity range (the fourth range). The four lamps  141 A to  144 A each being on or off indicate how close to the desired angle the central axis of the screw S is. Specifically, the central axis of the screw S is indicated to be closer to the desired angle in the order of the lamp  141 A being on, the lamp  142 A being on, and the lamp  143 A being on. The lamp  144 A being on indicates that, the central axis of the screw S is at the desired angle. 
     Under the control of the notification controller  127 , as described above, the notification section  14 A notifies a user of information about the result of light reception by the light receiver  11 , that is, which range the measured optical intensity falls by turning on an appropriate one of the lamps  141 A to  144 A. Thus, the user can easily know Whether or not the screw S is in a desired orientation and how close to the desired orientation the screw S is, and therefore can easily adjust the orientation of the screw S. 
       FIG. 9  is a flowchart of a process that is performed by the controller  12  of the electric screwdriver  10  according to Embodiment 2. 
     First, the controller  12  determines whether or not the switch  15  of the electric screwdriver  10  is being depressed (Step S 201 ). Upon the controller  12  determining that the switch  15  is not being depressed (NO in Step S 201 ), the drive controller  121  stops driving the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 208 ), and then the controller  12  waits until the switch  15  is depressed. 
     Upon determining that the switch  15  is being depressed (YES in Step S 201 ), the controller  12  determines whether or not the light receiver  11  is receiving the emitted light L (Step S 202 ). Specifically, the controller  12  determines that the light receiver  11  is receiving the emitted light L if the controller  12  is receiving the light reception signal from the light receiver  11 . 
     Upon the controller  12  determining that the light receiver  11  is receiving the emitted light L (YES in Step S 202 ), the intensity measurement section  125  measures the optical intensity of the received emitted light L (step S 203 ). 
     Next, the intensity determination section  126  performs the intensity range determination based on the optical intensity of the received emitted light L measured by the intensity measurement section  125  (the measured optical intensity) and the optical intensity ranges (the first to fourth ranges) stored in the memory (Step S 204 ). 
     Next, the notification controller  127  turns on an appropriate one of the tamps  141 A to  144 A based on a result of the intensity range determination and notifies a user of which optical intensity range the measured optical intensity falls within (Step S 205 ). 
     Upon the intensity range determination determining that the measured optical intensity falls within the fourth range (the specific intensity range) (YES in Step S 206 ), the drive controller  121  starts driving the fitting mechanism  13  if the fitting mechanism  13  is yet to be driven (Step S 207 ). Thus, the screwdriver bit D and a screw S being supported by the screwdriver bit D are caused to rotate, and fitting of the screw S in one set of screw holes  73  and  92  of the television receiver  100  is started. The drive controller  121  continues to drive the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 207 ). Thereafter, the controller  12  advances the process to Step S 201  and re-determines whether or not the switch  15  is being depressed. 
     Upon the controller  12  determining that the light receiver  11  is not receiving the emitted light L (NO in Step S 202 ), or the intensity range determination determining that the measured optical intensity fails within a range other than the fourth range (the specific intensity range) (NO in Step S 206 ), the drive controller  121  stops driving the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 208 ), and then the controller  12  advances the process to Step S 201  and re-determines whether or not the switch  15  is being depressed. 
     As described above, the electric screwdriver  10  according to the present embodiment drives the fitting mechanism  13  to fit the screw S in one set of screw holes  73  and  92  of the television receiver  100  when the measured optical intensity is within the specific intensity range. The central axis of the screw S is at substantially right angle to the side walls  72  and  91  when the measured optical intensity is within the specific intensity range. Thus, according to the present embodiment, fitting of the screws S in the screw holes  73  and  92  is performed only when the central axis of the screw S being worked on is at substantially right angle to the side walls  72  and  91 . It is therefore possible to prevent, the screws S from being fitted in a tilted manner. 
     According to the present embodiment, the electric screwdriver  10  notifies a user of which optical intensity range the measured optical intensity falls within by turning on an appropriate one of the lamps  141 A to  144 A. Thus, the user can know whether or not the screw S is in a desired orientation and how close to the desired orientation the screw S is, and therefore can easily adjust the orientation of the screw S. 
     The notification section  14 A according to the present embodiment has the plurality of lamps  141 A to  144 A, but may alternatively have only one lamp as in Embodiment 1. In such a configuration, the notification section  14 A may notify, under the control of the notification controller  127 , the user of whether or not the measured optical intensity is within the specific intensity range through the notification section  14 A being on or off. For example, the notification controller  127  may turn on the notification section  14 A if the measured optical intensity is within the specific intensity range and turn off the notification section  14 A if the measured optical intensity is not within the specific intensity range. 
     Embodiment 3 
     A machining system  1  according to Embodiment 3 has a similar configuration to the machining system  1  according to Embodiment 1 other than the configuration of the controller  12  of the electric screwdriver  10 . The following mainly describes differences between Embodiments 3 and 1,  FIG. 10  is a functional block diagram illustrating a configuration of main elements of an electric screwdriver  10  according to Embodiment 3. 
     According to Embodiment 3, a controller  12  of the electric screwdriver  10  functions as an angle measurement section  122  and an angle determination section  123  in addition to functioning as a drive controller  121  and a notification controller  127  through a CPU executing various computer programs stored in memory. The memory of the controller  12  for example stores therein data indicating a specific range of angle of incidence of emitted light L relative to a convex lens  111  (referred to below as a “specific angle range”). 
     When the controller  12  receives a light reception signal from a light receiver  11 , the angle measurement section  122  measures the angle of incidence of the received emitted light L, which in other words is the angle of incidence of the emitted light L relative to the convex lens  111 , As illustrated in  FIG. 11 , the emitted light L that has entered the convex lens  111  at an angle of incidence θ 1  is refracted by the convex lens  111 , and then travels from a principal plane of the convex lens  111  to a focal point (a focal plane) F. The angle of incidence θ 1  and an angle of refraction θ 2  are in a relationship represented by equation 1 shown below. In equation 1, f represents a focal length. In equation 1, h represents a distance (a separation distance) from a center O of the convex lens  111  to a location on the principal plane through which the emitted light L has passed. Accordingly, the angle measurement section  122  can determine the angle of incidence θ 1  by measuring the angle of refraction θ 2 , the separation distance h, and the focal length f. 
       tan θ2= h/f +tan θ1  equation 1
 
     Referring back to  FIG. 10 , the angle determination section  123  determines whether or not the angle of incidence of the received emitted light L measured by the angle measurement section  122  (referred to below as a “measured angle of incidence”) is within the specific angle range stored in the memory. According to the present embodiment, the specific angle range is a range of approximately 0° (for example, a range of less than or equal to 0.5°). 
     According to the present embodiment, the drive controller  121  drives a fitting mechanism  13  when the measured angle of incidence is within the specific angle range. Even when the light receiver  11  is receiving the emitted light L, however, the drive controller  121  does not drive the fitting mechanism  13  unless the measured angle of incidence is within the specific angle range. 
     According to the present embodiment, light exit openings  74  and  93  are disposed in specific positions on side walls  72  and  91 , and the light receiver  11  is disposed in a specific position on the electric screwdriver  10  and in a specific orientation so that a central axis of a screw S being supported by a screwdriver bit D of the fitting mechanism  13  is at a desired angle (at substantially right angle, according to the present embodiment) to the side walls  72  and  91  when the measured angle of incidence is within the specific angle range. 
     Thus, the central axis of the screw S is at substantially right angle to the side walls  72  and  91  when the measured angle of incidence is within the specific angle range. Through a switch  15  being depressed, the electric screwdriver  10  in such a state drives the fitting mechanism  13  to fit the screw S in one set of screw holes  73  and  92 . Thus, according to the present embodiment, fitting of the screws S in the screw holes  73  and  92  is performed only when the central axis of the screw S being worked on is at substantially right angle to the side walls  72  and  91 . It is therefore possible to prevent the screws S from being fitted in a tilted manner. 
     The notification section  14  is a lamp such as an LED as in Embodiment 1 and notifies, under the control of the notification controller  127 , a user of whether or not the measured angle of incidence is within the specific angle range through the notification section  14 A being on or off. For example, the notification controller  127  turns on the notification section  14  if the measured angle of incidence is within the specific angle range and turns off the notification section  14  if the measured angle of incidence is not within the specific angle range. Thus, the user can easily know whether or not the screw S is in a desired orientation (whether or not the central axis of the screw S is at substantially right angle to the side walls  72  and  91 ) through the notification section  14  being on or off, and therefore can easily decide whether or not to adjust the orientation of the screw S by shifting the electric screwdriver  10 . 
       FIG. 12  is a flowchart of a process that is performed by the controller  12  of the electric screwdriver  10  according to Embodiment 3. 
     First, the controller  12  determines whether or not the switch  15  of the electric screwdriver  10  is being depressed (Step S 301 ). Upon the controller  12  determining that the switch  15  is not being depressed (No in Step S 301 ), the drive controller  121  stops driving the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 306 ), and then the controller  12  waits until the switch  15  is depressed. 
     Upon determining that the switch  15  is being depressed (YES in Step S 301 ), the controller  12  determines whether or not the light receiver  11  is receiving the emitted light L (Step S 302 ). Specifically, the controller  12  determines that the light receiver  11  is receiving the emitted light L if the controller  12  is receiving the light reception signal from the light receiver  11 . 
     Upon the controller  12  determining that the light receiver  11  is receiving the emitted light L (YES in Step S 302 ), the angle measurement section  122  measures the angle of incidence of the received emitted light L (step S 303 ). 
     Next, the angle determination section  123  determines whether or not the measured angle of incidence is within the specific angle range based on the angle of incidence of the received emitted light L measured by the angle measurement section  122  (the measured angle of incidence) and the specific angle range stored in the memory (Step S 304 ). The notification controller  127  turns on the notification section  14  if the measured angle of incidence is within the specific angle range and turns off the notification section  14  if the measured angle of incidence is not within the specific angle range. 
     Upon the angle determination section  123  determining that the measured angle of incidence is within the specific angle range (YES in Step S 304 ), the drive controller  121  starts driving the fitting mechanism  13  if the fitting mechanism  13  is yet to be driven (Step S 305 ). Thus, the screwdriver bit D and a screw S being supported by the screwdriver bit D are caused to rotate, and fitting of the screw S in one set of screw holes  73  and  92  of the television receiver  100  is started. The drive controller  121  continues to drive the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 305 ). Thereafter, the controller  12  advances the process to Step S 301  and re-determines whether or not the switch  15  is being depressed. 
     Upon the controller  12  determining that the light receiver  11  is not receiving the emitted light L (NO in Step S 302 ), or the angle determination section  123  determining that the measured angle of incidence is not within the specific angle range (NO in Step S 304 ), the drive controller  121  stops driving the fitting mechanism  13  if the fitting mechanism  13  is already driven (Step S 306 ), and then the controller  12  advances the process to Step S 301  and re-determines whether or not the switch  15  is being depressed. 
     As described above, the electric screwdriver  10  according to the present embodiment drives the fitting mechanism  13  to fit the screw S in one set of screw holes  73  and  92  of the television receiver  100  when the measured angle of incidence is within the specific angle range. The central axis of the screw S is at substantially right angle to the side walls  72  and  91  when the measured angle of incidence is within the specific angle range, Thus, according to the present embodiment, fitting of the screws S in the screw holes  73  and  92  is performed only when the central axis of the screw S being worked on is at substantially right angle to the side walls  72  and  91 . It is therefore possible to prevent the screws S from being fitted in a tilted manner. 
     The electric screwdriver  10  according to the present embodiment notifies the user of whether or not the measured angle of incidence is within the specific angle range through the notification section  14  being on or off. Thus, the user can easily know whether or not the screw S is in a desired orientation, and therefore can easily decide whether or not to adjust the orientation of the screw S by shifting the electric screwdriver  10 . 
     Embodiment 4 
       FIG. 13  is a diagram illustrating partial external appearance of a television receiver  100  according to Embodiment 4.  FIG. 13  shows the television receiver  100  without screws S to facilitate explanation. 
     The television receiver  100  according to Embodiment 4 has a plurality of (two in the example illustrated in  FIG. 13 ) sets of light exit openings  74  and  93  for each set of screw holes  73  and  92 . Specifically, as illustrated in  FIG. 13 , one set of light exit openings (referred to below as “first light exit openings”)  74 A and  93 A is formed at a location a specific distance X away from one set of screw holes  73  and  92  in the device longitudinal direction, and another set of light exit openings (referred to below as “second light exit openings”)  74 B and  93 B is formed at a location a specific distance Y away from the one set of screw holes  73  and  92  in the device thickness direction. The arrangement of the sets of light exit openings  74  and  93  is not limited to that illustrated in  FIG. 13 . 
       FIG. 14  is a diagram illustrating an electric screwdriver  10  according to Embodiment 4 fitting a screw S in the television receiver  100 . 
     The electric screwdriver  10  according to Embodiment 4 includes a plurality of (two according to the example illustrated in  FIG. 14 ) light receivers  11  respectively corresponding to the sets of light exit openings  74  and  93  formed for each set of screw holes  73  and  92 . Specifically, the two light receivers  11  of the electric screwdriver  10  are a first light receiver  11 A corresponding to the first light exit openings  74 A and  93 A, and a second light receiver  11 B corresponding to the second light exit openings  74 B and  93 B. Each of the light receivers  11  receives emitted light L that has exited through the corresponding set of light exit openings  74  and  93 . 
     A controller  12  of the electric screwdriver  10  according to the present embodiment controls driving of a fitting mechanism  13  based on a result of light reception by each of the respective light receivers  11 . Specifically, the controller  12  has a similar configuration to the controller  12  according to any one of Embodiments 1 to 3 and operates as described below. That is, in a configuration in which the fitting mechanism  13  is driven when the light receiver  11  is receiving the emitted light L, the controller  12  performs a similar process to the process in the flowchart shown in  FIG. 6 . In this process, in Step S 102 , the controller  12  determines that the light receivers  11  are receiving the emitted light L if the first light receiver  11 A is receiving the emitted light L that has exited through the first light exit openings  74 A and  93 A, and the second light receiver  11 B is receiving the emitted light L that has exited through the second light exit openings  74 B and  93 B. 
     In a configuration in which the fitting mechanism  13  is driven when the measured optical intensity is within the specific intensity range, the controller  12  performs a similar process to the process in the flowchart shown in  FIG. 9 . In this process, in Step S 202 , the controller  12  determines that the light receivers  11  are receiving the emitted light L if the first light receiver  11 A is receiving the emitted light L that has exited through the first light exit openings  74 A and  93 A, and the second light receiver  11 B is receiving the emitted light L that has exited through the second light exit openings  74 B and  93 B. In Step S 206 , the controller  12  determines that the measured optical intensity falls within the fourth range (the specific intensity range) if the optical intensity of the received emitted light L that has exited through the first light exit openings  74 A and  93 A falls within the fourth range and the optical intensity of the received emitted light L that has exited through the second light exit openings  74 B and  93 B also falls within the fourth range. 
     In a configuration in which the fitting mechanists  13  is driven when the measured angle of incidence is within the specific angle range, the controller  12  performs a similar process to the process in the flowchart shown in  FIG. 12 . In this process, in Step S 302 , the controller  12  determines that the light receivers  11  are receiving the emitted light L if the first light receiver  11 A is receiving the emitted light L that has exited through the first light exit openings  74 A and  93 A, and the second light receiver  11 B is receiving the emitted light L that has exited through the second light exit openings  74 B and  93 B. In Step S 304 , the controller  12  determines that the measured angle of incidence is within the specific angle range if the angle of incidence of the received emitted light L that has exited through the first light exit openings  74 A and  93 A is within the specific angle range and the angle of incidence of the received emitted light L that has exited through the second light exit openings  74 B and  93 B is also within the specific angle range. 
     As described above, the electric screwdriver  10  according to the present embodiment determines whether or not to drive the fitting mechanism  13  based on the results of light reception by the plurality of (two, according to the present embodiment) light receivers  11  with respect to the emitted light L that has exited through the plurality of (two, according to the present embodiment) sets of light exit openings  74  and  93 . According to the present embodiment, therefore, it is possible to detect misdirection of the central axis of the screw S being worked on more accurately than when the detection is performed based on a result of light reception by one light receiver  11 . It is therefore possible to prevent the screw S from being fitted in a tilted manner more accurately. 
     Through the above, embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various changes may be made therein without departing from the gist of the present invention. 
     For example, a lens member for enhancing the directionality of the emitted light L, such as a lens sheet R, may be disposed over the light exit openings  74  and  93  (see  FIGS. 4 and 14 ). In such a configuration, the emitted light L passing through the lens sheet R is condensed and thus enhanced in directionality by the lens sheet R. As a result, the light receiver  11  receives the light more efficiently. The directionality of the emitted light L may be adjusted by changing the type of the lens sheet R. Note that the emitted light L according to the above-described embodiments is guided by the light exit openings  93  and  74 , which are through holes having a depth larger than a diameter thereof, and thus has some directionality. 
     Some of the above-described embodiments may be combined. For example, Embodiment 2 and Embodiment 3 may be combined. In such a configuration, the controller  12  functions as the intensity measurement section  125 , the intensity determination section  126 , the angle measurement section  122 , and the angle determination section  123  in addition to functioning as the drive controller  121  and the notification controller  127 . Accordingly, the controller  12  may measure the optical intensity and the angle of incidence of the received emitted light L, so that the fitting mechanism  13  is driven when the measured optical intensity is within the specific intensity range and the measured angle of incidence is within the specific angle range, and the fitting mechanism  13  is not driven when the measured optical intensity is not within the specific intensity range or the measured angle of incidence is not within the specific angle range. 
     According to the above-described embodiments, the light exit openings  74  and  93  penetrate the side walls  72  and  91  at right angle to the planes of the side walls  72  and  91 , and therefore the emitted light L travels in a direction orthogonal to the side walls  72  and  91 . Accordingly, the light receiver  11  is disposed in a position (a position on the electric screwdriver  10 ) and in an orientation that allow the light receiver  11  to receive the emitted light L traveling in the direction orthogonal to the side walls  72  and  91  when the central axis of the screw S being supported by the screwdriver bit D is at substantially right angle to the side walls  72  and  91 . However, the above-described arrangement of the light receiver  11  and the light exit openings  74  and  93  is merely an example, and the present invention is not limited thereto. For example, the light exit openings  74  and  93  may penetrate the side walls  72  and  91  in an oblique manner relative to the planes of the side walls  72  and  91  so that the emitted light L travels in a direction oblique to the side walls  72  and  91 . In such a configuration, the light receiver  11  is disposed in a position and in an orientation that allow the light receiver  11  to receive the emitted light L traveling in the direction oblique to the side walls  72  and  91  when the central axis of the screw S being supported by the screwdriver bit D is at substantially right angle to the side walls  72  and  91 . 
     According to the above-described embodiments (Embodiments 1 to 3), one set of light exit openings  74  and  93  is provided for each of the plurality of sets of screw holes  73  and  92 . However, one set of light exit openings  74  and  93  may be provided for a plurality of sets of screw holes  73  and  92 . For example, one set of light exit openings  74  and  93  may be provided for two adjacent sets of screw holes  73  and  92  at an intermediate location between the two adjacent sets of screw holes  73  and  92 . In such a configuration, the electric screwdriver  10  can determine whether or not to drive the fitting mechanism  13  for fitting the screws S in the two sets of screw holes  73  and  92  based on a result of reception of the emitted light L that has exited through the set of light exit openings  74  and  93  provided at the intermediate location between the two sets of screw holes  73  and  92  (that is, based on whether or not the emitted light L is being received, whether or not the measured optical intensity of the emitted light L is within the specific intensity range, or whether or not the measured angle of incidence of the emitted light L is within the specific angle range), Thus, it is possible to reduce the number of light exit openings  74  and  93 , and improve the appearance of the television receiver  100  as a product. 
     According to the above-described embodiments, the notification section  14  is a lamp such as an LED. However, the present invention is not limited thereto, and the notification section  14  may be any other device, such as a display, capable of notifying of information about the result of light reception by the light receiver  11 . 
     The electric screwdriver  10  may for example be provided with a plurality of (for example, three) light receivers  11  aligned in a specific direction. In such a configuration, the electric screwdriver  10  may measure the optical intensity of the emitted light L received by each of the light receivers  11  and notify a user of the thus measured optical intensities. Knowing the optical intensity of the emitted light L received by each of the light receivers  11  aligned in the specific direction, the user can easily decide a side in the specific direction (for example, the front side or the back side of the television receiver  100 , where the specific direction is the device thickness direction) the electric screwdriver  10  is to be shifted toward in order to adjust the screw S being worked on toward the desired orientation. Specifically, the user can adjust the screw S toward the desired orientation by shifting the electric screwdriver  10  toward the side having the light receiver  11  in which the highest optical intensity has been measured among the plurality of light receivers  11 . 
     According to the above-described embodiments, the light receiver  11  transmits the signal indicating light reception (the light reception signal) to the controller  12  when the light receiver  11  is receiving the emitted light L, and the controller  12  determines that the light receiver  11  is receiving the emitted light L if the controller  12  is receiving the light reception signal. However, the present invention is not limited thereto. For example, the light receiver  11  may transmit a light reception start signal indicating start of light reception to the controller  12  when the light receiver  11  has started receiving the emitted tight L. The light receiver  11  may also transmit a light reception finish signal indicating finish of light reception to the controller  12  when the light receiver  11  has finished receiving the emitted light L. Accordingly, the controller  12  may determine that the light receiver  11  is receiving the emitted light L during a period from when the light reception start signal has been received to when the light reception finish signal has been received, and may otherwise determine that the light receiver  11  is not receiving the emitted light L. 
     According to the above-described embodiments, functions of the drive controller  121 , the notification controller  127 , the intensity measurement section  125 , the intensity determination section  126 , the angle measurement section  122 , and the angle determination section  123  are implemented through the CPU executing the various computer programs stored in the memory (that is, implemented through software). However, these functions may be implemented through hardware. 
     For the above-described embodiments, the description is given using an example in which the user manually operates the electric screwdriver  10 , However, the present invention is not limited thereto. For example, the machining system  1  according to the above-described embodiments can be applied to a situation in which the electric screwdriver is automatically controlled using vision recognition of a camera. In such a situation; the machining system  1  can omit a process of vision recognition and thus achieve cost reduction. 
     REFERENCE SIGNS LIST 
     
         
           1  Machining system 
           10  Electric screwdriver 
           11  Light receiver 
           13  Fitting mechanism 
           14  Notification section 
           16  Light source 
           73 ,  92  Screw hole 
           7  Bezel 
           9  Backlight chassis 
           74 ,  93  Light exit opening 
           100  Television receiver 
           121  Drive controller 
           122  Angle measurement section 
           123  Angle determination section 
           125  Intensity measurement section 
           126  Intensity determination section 
           127  Notification controller 
         L Emitted light 
         R Lens sheet 
         S Screw