Patent Publication Number: US-7899342-B2

Title: Image forming apparatus

Description:
This application is the US national phase of international application PCT/JP2004/005188, filed 9 Apr. 2004, which designated the U.S. and claims priority of JP 2003-121899, filed 25 Apr. 2003, the entire contents of each of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present technology relates to an image forming apparatus. Specifically, it relates to improving a processing operation when there are not enough sheets remaining in a paper feed cassette to satisfy the requested number of image forming sheets. 
     BACKGROUND ART 
     Conventionally, in image forming apparatuses such as copying machines, printers, and the like, a paper feed cassette is provided that stores recording paper supplied to an image forming portion. Ordinarily, in order for it to be possible to refill and exchange recording paper in this paper feed cassette, it is installed so that the paper feed cassette can be inserted and removed from the main body of the image forming apparatus. Also, this paper feed cassette is provided with a rotating board (also referred to as a lift board) that can rotate in the vertical direction while supporting the recording paper. A coil spring is disposed on the underside of this rotating board, and biasing force is conferred on the rotating board in the upward direction by this coil spring. Therefore, when the paper feed cassette loaded with paper is inserted in the main body of the image forming apparatus, the uppermost sheet of recording paper faces or makes contact with a pickup roller, and it is possible for paper to be supplied from the paper feed cassette toward an image forming portion by the rotation of this pickup roller. 
     On the other hand, in this type of image forming apparatus, the achievement of a reduction in the installation space of the apparatus has been sought, and in response, image forming apparatuses have been developed wherein a paper feed portion (the paper feed cassette) is disposed in the lower portion, an original capturing portion (scanner portion) is disposed in the upper portion, and an image forming portion (print portion) and a discharge portion (discharge tray) are provided between the paper feed portion and the original capturing portion. That is, a reduction in the installation space of the image forming apparatus is achieved by adopting a configuration such that the discharge tray does not protrude in the lateral direction of the apparatus. Also, in this image forming apparatus, the paper feed cassette, the scanner portion, and the print portion are arranged in the shape of a sideways U in a front perspective of the apparatus. Therefore, the discharge tray is configured as an intermediate space open in the lateral direction (one side of the sideways U shape is open), and printed materials discharged to this intermediate space portion are removed from the front side or the lateral side (the open side described above) of the apparatus. 
     However, in an image forming apparatus with this sort of configuration, because the paper feed cassette is disposed in the lower portion of the apparatus, when the user wants to check the amount of paper remaining in the paper feed cassette, he must, in a bent over posture, pull the paper feed cassette out of the main body of the image forming apparatus and visually check the remaining paper. Particularly, when the user is a disabled individual, this checking operation is extremely bothersome and requires time. 
     Also, when the image forming apparatus stops during a printing operation, it is necessary for the user to check the reason for the stop, and afterwards take action to deal with the problem, and when the cause of the stoppage is an exhausted supply (during a printing operation there is no paper remaining in the paper feed cassette), after pulling out the paper cassette and visually confirming that there is no paper remaining, as described above, the user prepares paper and refills the paper feed cassette. This action requires a long period of time, during which print jobs are erased, and when there are image forming requests from other users during that period of time, multiple print jobs accumulate in the memory of the image forming apparatus, and an insufficient memory status may result. 
     As a way of solving this problem, for example, JP 2000-313533A discloses technology wherein when there is no paper remaining in the paper feed cassette during execution of a print operation, the paper feed cassette is automatically pushed out a small amount from its installed state. By doing so, the user can quickly confirm that the supply is exhausted without pulling out the paper cassette. 
     However, in the technology disclosed in JP 2000-313533A, when the image forming apparatus stops during a printing operation, the user can not confirm that the supply is exhausted unless he goes to the location where the image forming apparatus is installed and visually checks the condition of the paper feed cassette. Therefore, when refill paper is stored in a different location than the printer is installed, the user must go to the storage location to get refill paper after going to the installed location of the image forming apparatus and confirming that the supply is exhausted, and again return to the location in which the image forming apparatus is installed. 
     Also, ordinarily, when an image request signal is given from a terminal on a network to the image forming apparatus, a printer mark (a mark indicating that a print operation is in progress) is displayed on the display of this terminal, but when the user has confirmed that this display has not disappeared for a long time, it is necessary for the user to move to the location where the image forming apparatus is installed and check the reason that the print operation has not completed. That is, after the image forming request signal is given from the terminal to the image forming apparatus, though another operation is being performed on that terminal, this operation must be temporarily interrupted and the reason that the print operation has not completed must be confirmed, worsening operating efficiency. 
     The present technology was made with the foregoing in mind, and it is an object thereof to provide an image forming apparatus wherein a state is not incurred in which, if a user gives an image forming request when there are few sheets of paper remaining in the paper feed cassette, the supply is exhausted during the image forming operation, and the user must move to the location in which the image forming apparatus is installed and perform a confirmation operation, nor a state in which an operation of the user is temporarily interrupted. 
     DISCLOSURE OF PRESENT TECHNOLOGY 
     Overview of the Present Technology 
     In order to achieve the object stated above, in accordance with the present technology, if there are not enough sheets remaining in the paper feed cassette to satisfy an image forming request when forming an image, waits for a paper refill is awaited without executing the image forming operation, and the image forming operation is begun after that paper refill. When awaiting this paper refill, along with prompting the user to refill the paper, the paper feed cassette is popped out and the lack of paper can easily be confirmed. 
     Solving Means 
     Specifically, an image forming apparatus is presumed that is provided with a paper feed cassette and an image forming portion, and takes out a recording medium stored in this paper feed cassette sheet by sheet in response to an image forming request and performs image forming in the image forming portion. This image forming apparatus is provided with a push-out means, a warning means, a sheet quantity confirming means, and a control means. The push-out means can push out the paper feed cassette from an installed state toward an uninstalled state relative to the main body of the apparatus. The warning means can emit a warning that there is insufficient paper to a user who requested image forming. The sheet quantity confirming means can confirm the number of sheets of the recording medium stored in the paper feed cassette. The control means causes the sheet quantity confirming means to confirm the number of sheets of the recording medium stored in the paper feed cassette when an image forming request has been received, and if the number of sheets of the recording medium stored in the paper feed cassette is lower than the number of sheets requested by the image forming request, the control means causes the paper feed cassette to be pushed out from an installed state toward an uninstalled state by the push-out means without executing the image forming operation, and causes the user to be warned by the warning means that the number of sheets of the recording medium is insufficient. 
     With these specified items, when the image forming apparatus receives an image forming request signal, the sheet quantity confirming means confirms the number of sheets of the recording medium that are stored in the paper feed cassette. When the confirmed number of sheets (the number of sheets of paper remaining in the paper feed cassette) is greater than the requested number of image forming sheets, that is, when the image forming operation can be completed from the remaining recording medium, the image forming operation is executed in that state. 
     On the other hand, when the confirmed number of sheets (the number of sheets of paper remaining in the paper feed cassette) is lower than the requested number of image forming sheets, that is, in a condition in which when executing the image forming operation as-is, the paper will run out during image forming, the paper feed cassette is pushed out from an installed state toward an uninstalled state with the push-out means without beginning the image forming operation, and the user is warned by the warning means that the number of sheets of the recording medium is insufficient. Thus the user can immediately confirm that a refill of the storage medium (paper) is necessary, and immediately begin the work of refilling the paper without the need to confirm the status of the image forming apparatus. Thus, when the refill recording medium is stored in a different location than the image forming apparatus is installed, the user can go to get the recording medium from the storage location of the refill recording medium without going to the installed location of the image forming apparatus, and then go to the installed location of the image forming apparatus and perform the work of refilling the paper. That is, the activity of approaching the installed location of the image forming apparatus and confirming that there is no paper remaining, prior to going to the storage location of the recording medium, is no longer necessary. And, it is possible to allow the user to confirm the lack of paper within a short period of time after sending an image request signal from a terminal to the image forming apparatus. That is, after the user has sent an image request signal and before beginning separate work on that terminal, it is possible to prompt the user for a paper refill as necessary, and so it is possible to avoid temporarily interrupting work on the user terminal after it has been begun. 
     The following is given as a specific configuration of the control means. That is, when an image forming request has been received from a terminal machine through a network, the control means lets the sheet quantity confirming means confirm the number of sheets of the recording medium stored in the paper feed cassette, and if the number of sheets of the recording medium stored in the paper feed cassette is lower than the number of sheets requested by the image forming request, the control means the paper feed cassette to be pushed out from an installed state toward an uninstalled state by the push-out means without executing the image forming operation, and the user is warned by the warning means that the number of sheets of the recording medium is insufficient. 
     That is, this solving means is a configuration in the case of having the image forming apparatus function as a printer on a network. Particularly, in this case, because the user is always in the installed location of the terminal machine (user terminal), in the conventional technology, when the image forming apparatus stops during a printing operation, it is difficult to quickly confirm the reason for the stoppage. With the present solving means, before the printing operation is begun, it is possible to have the user confirm that if the print operation is executed in the present state the print operation will be stopped before it completes due to the supply being exhausted. 
     The following is specifically given as a configuration of the sheet quantity confirming means. 
     First, a paper storage board is provided in the paper feed cassette that, along with supporting the recording medium, moves to a lower position as the number of stored sheets of the recording medium increases. The sheet quantity confirming means is configured so as to confirm the number of sheets of the recording medium stored in the paper feed cassette by detecting the height position of the paper storage board with a reflective optical sensor. 
     Also, as another configuration of the sheet quantity confirming means, it is provided with a matching portion made of metal that extends in the vertical direction along the edge of the stored recording medium and matches the recording medium, and a paper storage board made of metal that is movable along this matching portion in the vertical direction while contacting this matching portion and that moves to a lower position as the number of stored sheets of the recording medium increases. The sheet quantity confirming means is configured so as to let a current flow from the paper storage board to the matching portion, and confirm the number of sheets of the recording medium stored in the paper feed cassette based on the electrical resistance from the paper storage board to the matching portion, which changes according to the height position of the paper storage board. 
     From these specified items, it is possible to confirm the number of sheets (remaining sheets) of the recording medium stored in the paper feed cassette with a comparatively simple configuration. Particularly, in the configuration that confirms the number of sheets of the recording medium based on the electrical resistance, by utilizing the fact that, from the related art, the rotating board and the matching portion are made of metal, it is possible to confirm the number of sheets of the recording medium without requiring a special electric circuit. 
     The following is given as a specific configuration of the push-out means. That is, the push-out means is provided with an engaging mechanism that can switch between an engaged state and a released state of the paper feed cassette relative to the main body of the apparatus, and a biasing portion that confers a biasing force on the paper feed cassette in the push-out direction, and when the number of sheets of the recording medium stored in the paper feed cassette is lower than the requested number of image forming sheets, the engaging mechanism puts the paper feed cassette in a released state relative to the main body of the apparatus. 
     By these specified items, when an image forming request has been received, when the number of sheets of the recording medium stored in the paper feed cassette is lower than the requested number of image forming sheets, the engaging mechanism puts the paper feed cassette in a released state relative to the main body of the apparatus, and thus the paper feed cassette is pushed out from the main body of the apparatus by the biasing force of the biasing portion. That is, it becomes possible to realize a push-out means with a simply configured engaging mechanism such as a solenoid, for example, and an improvement in practicality can be realized. 
     The following is given as a timing of the operation of various means described above. That is, the control means is configured so that immediately after an image forming request has been received, the control means causes the sheet quantity confirming means to confirm the number of sheets of the recording medium stored in the paper feed cassette, and if the number of sheets of the recording medium stored in the paper feed cassette is lower than the number of sheets requested by the image forming request, the control means causes the paper feed cassette to be pushed out from an installed state toward an uninstalled state by the push-out means without executing the image forming operation, and the control means causes the user to be warned by the warning means that the number of sheets of the recording medium is insufficient. In this way, because an operation according to the number of sheets of the recording medium in the paper feed cassette is performed immediately after the image forming request has been received, after a user sends an image request signal, it is possible to reliably prompt the user to refill paper before beginning other work on that terminal, and avoid the need to temporarily interrupt work on that terminal. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing that schematically shows an internal structure of a compound machine according to an example embodiment. 
         FIG. 2  is a cross-sectional view with part of the paper feed cassette omitted. 
         FIG. 3  is a drawing illustrating the structure and principle of the reflective optical sensor. 
         FIG. 4A  is a drawing that shows the relationship between the distance to the reflective surface when the light receiving portion detects the reflective surface of the light and the output level corresponding to the amount of light received, and  FIG. 4B  is a drawing that shows the characteristic regions in which the reflective optical sensor operates. 
         FIG. 5  is a drawing that shows a modified example of the reflective optical sensor. 
         FIG. 6  is a drawing that shows the push-out mechanism. 
         FIG. 7  is a drawing illustrating the engaging mechanism. 
         FIG. 8  is a flowchart that illustrates the print operation of the compound machine. 
         FIG. 9  is cross-sectional view that shows a part of the interior of the paper feed cassette according to a second example embodiment. 
         FIG. 10  is a drawing that shows the relationship between the number of sheets of paper in the paper feed cassette and the electric current value detected by the electric current sensor. 
     
    
    
     BEST MODE FOR CARRYING OUT THE PRESENT TECHNOLOGY 
     Hereinafter, the present technology will be described by way of illustrative embodiments with reference to the drawings. In the present example embodiment, the present technology is described with regard to its application in a compound machine provided with a copy function, a print function, and a facsimile function. In these example embodiments, any paper such as image forming paper or recording paper can be used as a recording medium, but the recording medium is not restricted to these. Other forms of recording media may also be used, such as overhead projector sheets, for example. 
     Example Embodiment 1 
     Explanation of the Configuration of the Compound Machine as a Whole 
       FIG. 1  schematically shows an overview of the internal structure of a compound machine  1  as an image forming apparatus according to the present example embodiment. As shown in  FIG. 1 , the compound machine  1  includes a scanner portion  2 , a print portion  3  as an image forming portion, and an automatic original paper feed portion  4 . These parts are described below. 
     &lt;Description of The Scanner Portion  2 &gt; 
     The scanner portion  2  reads the image of an original placed on an original stage  41  that is made of transparent glass, or the like, or the image of an original that is supplied sheet by sheet from the automatic original paper feed portion  4 , and creates image data. This scanner portion  2  includes an exposure light source  21 , a plurality of reflective mirrors  22 ,  23 , and  24 , an imaging lens  25 , and a photoelectric transducer (CCD: Charge Coupled Device)  26 . 
     The exposure light source  21  irradiates light onto the original that is placed on the original stage  41  of the automatic original paper feed portion  4  or the original carried by the automatic original paper feed portion  4 . As shown in  FIG. 1  by the dotted line A indicating the optical path, the reflective mirrors  22 ,  23 , and  24  are set so as to first reflect the light that is reflected from the original to the left of the diagram, after which they reflect the light downward, and after which they then reflect the light rightward toward the imaging lens  25 . 
     As the operation to read the image of the original, if the original is placed on the original stage  41  (if used in the “stationary sheet mode”), then the exposure light source  21  and the reflective mirrors  22 ,  23 , and  24  horizontally scan the original stage  41  to read in the image of the entire original. On the other hand, if reading in an original that is carried by the automatic original paper feed portion  4  (if used in the “moving sheet mode”), the exposure light source  21  and the reflective mirrors  22 ,  23 , and  24  are fixed in the position shown in  FIG. 1 , and the image of the original is read in as the original passes a reading portion  42  of the automatic original paper feed portion  4 , described later. 
     Light that is reflected by the reflecting mirrors  22 ,  23 , and  24  to pass through the imaging lens  25  is guided to the CCD  26 , and the reflected light is converted into an electrical signal (original image data) by the CCD  26 . 
     &lt;Description of The Print Portion  3 &gt; 
     The print portion  3  includes an image forming system  31  and a paper transport system  32 . 
     The image forming system  31  includes a laser scanning unit  31   a  and a photosensitive drum  31   b  as a drum-type image transport body. The laser scanning unit  31   a  irradiates laser light onto the surface of the photosensitive drum  31   b , based on the original image data that is converted by the CCD  26 . The photosensitive drum  31   b  rotates in the direction of the arrow shown in  FIG. 1 , and an electrostatic latent image is formed on its surface by laser light irradiated from the laser scanning unit  31   a.    
     In addition to the laser scanning unit  31   a , a development apparatus (development mechanism)  31   c , a transfer unit  31   d  that constitutes a transfer mechanism, a cleaning apparatus (cleaning mechanism)  31   e , a de-electrifier not shown in the drawings, and a charging unit  31   f  are circumferentially arranged in order around the photosensitive drum  31   b . The development apparatus  31   c  uses toner (a substance for forming a manifest image) to develop the electrostatic latent image formed on the surface of the photosensitive drum  31   b  into a visible image. The transfer unit  31   d  transfers the toner image formed on the surface of the photosensitive drum  31   b  onto a piece of image forming paper (recording medium) that is a recording medium. The cleaning apparatus  31   e  removes toner remaining on the surface of the photosensitive drum  31   b  after toner transfer. The de-electrifier removes a residual electric charge from the surface of the photosensitive drum  31   b . The charging unit  31   f  provides a predetermined electric potential to the surface of the photosensitive drum  31   b  before the electrostatic latent image is formed. 
     Thus, when forming an image on the image forming paper, the surface of the photosensitive drum  31   b  is charge to a predetermined electric potential by the charging unit  31   f , and then the laser scanning unit  31   a  irradiates laser light onto the surface of the photosensitive drum  31   b  based on the original image data. After this, the development apparatus  31   c  uses toner to develop a visible image on the surface of the photosensitive drum  31   b , and the toner image is transferred to image forming paper by the transfer unit  31   d . Further still, after this, the cleaning apparatus  31   e  removes the toner remaining on the surface of the photosensitive drum  31   b  and the de-electrifier removes the electric charge remaining on the surface of the photosensitive drum  31   b . Thus, one cycle of the operation to form an image on the image forming paper (printing operation) is complete. By repeating this cycle, it is possible to successively form images on a plurality of sheets of image forming paper. 
     On the other hand, the paper transport system  32  carries image forming paper contained in a paper cassette  33 , which is a paper containing portion, sheet by sheet to form images according to the image forming system  31 , and discharges the image forming paper on which an image has been formed to a discharge tray  35 , which is a discharge portion. 
     The paper transport system  32  is provided with a principal transport path  36  and a reverse transport path  37 . One end of the principal transport path  36  faces the discharge side of the paper cassette  33 , while the other end faces a discharge tray  35 . One end of the reverse transport path  37  is upstream (below, in the drawing) of the arranged position of the transfer unit  31   d  and is connected to the principal transport path  36 , and the other end is downstream (above, in the drawing) of the arranged position of the transfer unit  31   d  and is connected to the principal transport path  36 . 
     The upstream end of the principal transport path  36  (the part facing the discharge side of the paper cassette  33 ) is provided with a pickup roller  36   a  whose cross-section is semicircular. Image forming paper contained in the paper cassette  33  can be intermittently supplied sheet by sheet into the principal transport path  36  by rotating the pickup roller  36   a.    
     Register rollers  36   d  are arranged in the principal transport path  36  on the upstream side of the transfer unit  31   d . The register rollers  36   d  are rollers for matching the position of the toner image on the surface of the photosensitive drum  31   b  to the image forming paper while transporting the image forming paper. A fixing apparatus  39 , that is provided with a pair of fixing rollers  39   a  and  39   b  for using heat to fix the toner image that is transferred to the image forming paper, is arranged in the principal transport path on the downstream side of the arranged position of the transfer unit  31   d . This fixing apparatus  39  will be described in detail below. Moreover, discharge rollers  36   e  for discharging the image forming paper to the discharge tray  35  are arranged at the downstream end of the principal transport path  36 . 
     A branch catch  38  is arranged at the position at which the upstream end of the reverse transport path  37  connects to the principal transport path  36 . The branch catch  38  is rotatable around a horizontal axis between a first position, which is shown by a solid line in  FIG. 1 , and, rotating in a counter clockwise direction in  FIG. 1  from the first position, a second position opening the reverse transport path  37 . When the branch catch  38  is in the first position, the image forming paper is carried toward the discharge tray  35 , and when it is in the second position, the image forming paper can be delivered into the reverse transport path  37 . Transport rollers  37   a  are arranged in the reverse transport path  37 , and the paper transport system  32  is arranged such that if the image forming paper is delivered into the reverse transport path  37  (if the image forming paper is fed into the reverse transport path  37  by what is known as “switchback transport”), then the image forming paper is transported by the transport rollers  37   a  and the image forming paper is reversed on the upstream side of the register roller  36   d , and is again carried along the principal transport path  36  toward the transfer unit  31   d . That is to say, it is handled such that an image may be formed on the back side of the image forming paper. 
     &lt;Description of the Automatic Document Paper feed portion  4 &gt; 
     The following is a description of the automatic original paper feed portion  4 . The automatic original paper feed portion  4  is configured as what is known as an automatic two-sided original transport apparatus. The automatic original paper feed portion  4  can be used for a sheet moving mode and is provided with an original tray  43  as an original placement portion, an intermediate tray  44 , an original discharge tray  45  as an original discharge portion, and an original transport system  46  that transports originals between the trays  43 ,  44 , and  45 . 
     The original transport system  46  is provided with a main transport path  47  for transporting originals placed on the original tray  43  to the intermediate tray  44  via the original capturing portion  42  or the original discharge tray  45 , and a secondary transport path  48  for supplying originals on the intermediate tray  44  to the main transport path  47 . 
     An original pickup roller  47   a  and a fielding roller  47   b  are arranged at an upstream end (a portion facing the discharge side of the original tray  43 ) of the main transport path  47 . A fielding board  47   c  is arranged below the fielding roller  47   b  and, due to the rotation of the original pickup roller  47   a , one sheet of the originals on the original tray  43  passes between the fielding roller  47   b  and the fielding board  47   c  such that it is supplied to the main transport path  47 . PS rollers  47   e  are arranged on a side lower than the linking area between the main transport path  47  and the secondary transport path  48  (area B in the drawing). The PS rollers  47   e  regulate the leading edge of the original and the image reading timing of the scanner portion  2  when supplying originals to the original capturing portion  42 . That is, the PS rollers  47   e  temporarily stop the transport of the original in the state in which the original was supplied, and regulate the image reading timing when supplying originals to the original capturing portion  42 . 
     The original capturing portion  42  is provided with a platen glass  42   a  and an original pressing board  42   b  and, when an original supplied from the PS rollers  47   e  passes through between the platen glass  42   a  and the original pressing board  42   b , light from the above-mentioned exposure light source  21  passes through the platen glass  42   a  and is irradiated on the original. At this juncture, original image data is obtained by the above-mentioned scanner portion  2 . A biasing force is applied to the back surface (top surface) of the original pressing board  42   b  by an unshown coil spring. In this way, the original pressing board  42   b  makes contact against the platen glass  42   a  with a predetermined suppressing force, thus preventing the original from rising up from the platen glass  42   a  when the original passes through the original capturing portion  42 . 
     Transport rollers  47   f  and original discharge rollers  47   g  are provided on a downstream side of the platen glass  42   a . An original that passes over the platen glass  42   a  is discharged to the intermediate tray  44  or the original discharge tray  45  via the transport rollers  47   f  and the original discharge rollers  47   g.    
     An intermediate tray swinging board  44   a  is arranged between the original discharge rollers  47   g  and the intermediate tray  44 . The intermediate tray swinging board  44   a  has its swinging center at an edge area of the intermediate tray  44  and is able to swing between a position  1  shown in the drawing by a solid line and a position  2  in which it is raised upwards from the position  1 . When the intermediate tray swinging board  44   a  is in the position  2 , an original discharged from the original discharge rollers  47   g  is withdrawn to the original discharge tray  45 . On the other hand, when the intermediate tray swinging board  44   a  is in the position  1 , an original discharged from the original discharge rollers  47   g  is discharged to the intermediate tray  44 . When an original is discharged to the intermediate tray  44 , an edge of the original is sandwiched between the original discharge rollers  47   g , and by reversing the rotation of the original discharge rollers  47   g  while in this condition, the original is supplied to the secondary transport path  48  and is again dispatched to the main transport path  47  via the secondary transport path  48 . The operation of reversing the rotation of the original discharge rollers  47   g  is carried out by regulating the dispatch of the original to the main transport path  47  and the timing of image reading. In this way, an image on the reverse side of an original can be read by the original capturing portion  42 . 
     —Description of Basic Operation of the Compound Machine— 
     As the operation of the compound machine  1  configured as described above, first, this compound machine  1 , when it functions as a printer, receives print data (image data or text data) sent from a host apparatus such as a personal computer, and stores this received print data in a buffer (memory) not shown. Along with storing this print data in the buffer, print data is read out from the buffer in sequence, and based on this read out print data, an image is formed on image forming paper by the image forming operation of the print portion  3  described above. 
     Also, when this compound machine  1  functions as a scanner, it stores the scan image data of the original read by the scanner portion  2  in the buffer. Along with storing this scan image data in the buffer, it sends the scan image data in sequence from the buffer to the host apparatus, and shows the image on a display of this host apparatus. 
     Further, when this compound machine  1  functions as a copy machine, an image is formed on image forming paper by the image forming operation of the print portion  3 , based on the original image data read by the scanner function. 
     —Description of the Paper Cassette  33 — 
     The following is an explanation of the paper feed cassette  33 , which is one characteristic portion of the present example embodiment.  FIG. 2  is a cross-sectional view that omits part of the paper feed cassette  33  provided in this compound machine  1 . The left of the diagram is the direction that the paper feed cassette  33  is pulled out when it is pulled out from the main body of the apparatus (the direction shown by the arrow). 
     As shown in  FIG. 2 , the paper feed cassette  33  is configured such that inside a cassette main body  33   a  configured in the shape of a container that is open to the upper side, a rotating board  33   b , which is a paper storage board made of metal, is supported so that it can rotate. 
     The rotating board  33   b  is supported so that it can vertically rotate around a rotational center that extends in the width direction (the direction perpendicular to the paper face in  FIG. 2 ) on the bottom surface of the cassette main body  33   a , and a coil spring  33   c  is compressed under that board. That is, this rotating board  33   b  constantly receives an upward biasing force from the coil spring  33   c.    
     Also, a paper leading edge matching portion  33   d , which is a matching portion made of metal for making contact with and matching the leading edge of recording paper P, is provided in an edge portion (the right edge portion in the figure) in the interior of the cassette main body  33   a . This paper leading edge matching portion  33   d  is made of metal, and a pressing portion  33   e  is formed in its upper edge portion to press down the corner edge portion of the recording paper P from above. And, portion  33   f  in the figure is a paper trailing edge pressing portion for matching the position of the trailing edge of the recording paper P (the edge in the direction that the paper feed cassette  33  is pulled out). 
     Because the paper feed cassette  33  is configured in this manner, when the recording paper P is loaded into the paper feed cassette  33 , the rotating board  33   b  rotates upward due to the biasing force of the coil spring  33   c , and that position of rotation is regulated to be the position where the leading edge corner portion of the recording paper P makes contact with the pressing portion  33   e  of the paper leading edge matching portion  33   d . That is, the position of rotation of the rotating board  33   b  is determined by the number of sheets of paper in the paper feed cassette  33 , and the greater the number of sheets of recording paper P, the further downward the position of rotation of the rotating board  33   b  will become. By inserting the paper feed cassette  33  into the main body of the image forming apparatus in such a state, the uppermost sheet of recording paper P faces or makes contact with the pickup roller  36   a , and due to rotation of this pickup roller  36   a  it is possible to supply paper from the paper feed cassette  33  towards the print portion  3 . 
     Also, a reflective optical sensor  7  is provided in this paper cassette  33  as a sheet quantity checking means that can check the number of sheets of recording paper P that are stored in the paper feed cassette  33 . As shown in  FIG. 3 , this reflective light optical sensor  7  is disposed on the bottom face of the cassette main body  33   a , and includes a light emitting portion (such as an LED)  71  that irradiates light towards the bottom face of the rotating board  33   b  and a light receiving portion (light receiving sensor)  72  that receives the light emitted toward the bottom face of the rotating board  33   b  by this light emitting portion  71 . Specifically, a concave portion  73  that has been made concave in approximately a V-shape is provided, the light emitting portion  71  is installed on one of the diagonal surfaces, and the light receiving portion  72  is installed on the other diagonal surface. The light emitting portion  71  and the light receiving portion  72  are arranged slightly tilted in the direction facing each other. 
     Thus, as shown by a solid line in  FIG. 3 , when the position of rotation of the rotating board  33   b  is a position in the upper direction (when there is a low quantity of paper remaining), the overlapping area of the irradiated region of light irradiated to the bottom face of the rotating board  33   b  from the light emitting portion  71  and the region of the bottom face of the rotating board  33   b  that can receive light with the light receiving portion  72  is comparatively small, and the distance from the light emitting portion  71  and the light receiving portion  72  to the bottom face of the rotating board  33   b  is comparatively far, and so comparatively little light is received by the light receiving portion  72 . Conversely, as shown by the broken line in  FIG. 3 , when the position of rotation of the rotating board  33   b  is in the lower direction (when there is a large quantity of paper remaining), the overlapping area of the irradiated region of light irradiated to the bottom face of the rotating board  33   b  from the light emitting portion  71  and the region of the bottom face of the rotating board  33   b  that can receive light with the light receiving portion  72  is comparatively large, and the distance from the light emitting portion  71  and the light receiving portion  72  to the bottom face of the rotating board  33   b  is comparatively close, and so a comparatively large amount of light is received by the light receiving portion  72 . In this way, because the position of rotation of the rotating board  33   b  can be confirmed by the amount of light received by the light receiving portion  72 , the number of sheets of paper in the paper feed cassette  33  can also be confirmed by the amount of light received. That is, a configuration is adopted wherein the less sheets there are in the paper feed cassette  33 , the less light is received. 
       FIG. 4(   a ) shows the relationship between the distance to the reflective surface when the light-receiving portion  72  detects the reflective surface of the light and the output level corresponding to the amount of light received. In this example embodiment, among the properties of this light receiving portion  72 , it is made such that the number of sheets of paper in the paper feed cassette  33  can be confirmed using the region in which the amount of light received gradually decreases as the distance to the reflective face increases (see  FIG. 4(   b )). That is, when the amount of light received is I in the figure, it is confirmed that the paper feed cassette  33  is full of recording paper P, and when the amount of light received is II, it is confirmed that the paper feed cassette  33  is empty. Also, when the amount of light received is between I and II, the number of sheets of recording paper P is confirmed according to that amount of light received. For example, in a paper feed cassette that can store 500 sheets of recording paper P, when the amount of light received is III, it is confirmed that there are 250 sheets of recording paper P stored in the paper feed cassette  33 . 
     In the present example embodiment, the light emitting portion  71  and the light receiving portion  72  are disposed in the approximately V-shaped concave portion  73 , but as shown in  FIG. 5 , the light emitting portion  71  and the light receiving portion  72  may also be disposed on the same flat surface. 
     —Description of the Push-Out Mechanism— 
     Following is a description of a push-out mechanism  8 , which is a push-out means wherein it is possible to push out the paper feed cassette  33  from an installed state towards an uninstalled state.  FIG. 6  shows this push-out mechanism  8 . As shown in this figure, the push-out mechanism  8  is provided with a coil spring  81  as a biasing portion that confers a biasing force in the direction that puts the paper feed cassette  33  in an uninstalled state, and an engaging mechanism  82  that can switch between the engaged state and the disengaged state of the paper feed cassette  33  with respect to the main body of the apparatus. 
     The coil spring  81  is compressed between the side of the paper feed cassette  33  (the insertion side when inserting the cassette into the main body of the apparatus) and the inner surface of the main body of the apparatus, and in a state in which the paper feed cassette  33  is installed in the main body of the apparatus, a biasing force is constantly conferred in the direction that will uninstall the cassette (the push-out direction: the left direction in  FIG. 6 ). 
     On the other hand, the engaging mechanism  82  is provided with a fixed catch  83  fixed on the lower edge of the side of the paper feed cassette  33  (the push-out side when pushing out the cassette from the main body of the apparatus), and a movable catch  84  supported so that it can rotate around the horizontal axis relative to the main body of the apparatus. This movable catch  84  is connected via a connecting portion  87  comprising a coil spring or the like to a leading edge portion of a rising and setting rod  86  that extends from a solenoid  85  installed in an apparatus frame  11 . Thus, in an unexcited state of the solenoid  85 , the movable catch  84  becomes engaged with the fixed catch  83 , and a state is maintained in which the paper feed cassette  33  is installed in the main body of the apparatus (the state in  FIG. 6  and  FIG. 7(   a )). On the other hand, in an excited state of the solenoid  85 , the rod  86  sinks in, the movable catch  84  moves in the direction escaping from the fixed catch  83 , and releases the paper feed cassette  33  (the state in  FIG. 7(   b )). Thus, the paper feed cassette  33  is pushed out in the direction in which it becomes uninstalled (the push-out-direction) by the biasing force of the coil spring  81 . 
     —Description of an Example Control Portion/Control Means— 
     A control portion/control means  93  that performs overall control over this compound machine  1  receives a signal from the light receiving portion  72 , and is switched between an excited and an unexcited state of the solenoid  85  of the engaging mechanism  82 . Specifically, this control portion  93  causes the number of sheets of recording paper P stored in the paper feed cassette  33  to be confirmed by the reflective optical sensor  7  when an image forming request is received from a terminal device, and when the number of sheets of recording paper P stored in the paper feed cassette  33  is lower than the requested number of image forming sheets, causes the paper feed cassette  33  to be pushed out from an installed state toward an uninstalled state by the push-out mechanism  8 , without executing an image forming operation. That is, it puts the paper feed cassette  33  in a released state by exciting the solenoid  85 , and thereby causes the paper feed cassette to be pushed out in the direction such that it is uninstalled (the push-out direction). 
     Also, the main compound machine  1  is provided with a warning means  94  that can emit a warning to a user (terminal device) that has made an image forming request, and when putting the paper feed cassette in a released state, gives a warning to the user with the warning means  94  to the effect that the number of sheets of recording paper is insufficient. Specifically, it displays a message such as “There is not enough paper” on the display of the terminal device that the user is operating. And, besides the message display on the terminal device that the user is operating, as another example, a warning means  94  may also be configured wherein an auditory warning is given to the user from the main compound machine  1 , and further, a warning means  94  may also be configured wherein a message display and an auditory warning are given to the user. 
     —Description of the Operating Procedure— 
     Following is a description of the printing operation of the compound machine  1  with reference to the flowchart in  FIG. 8 . First, in Step  1 , a printing request is made to the main compound machine  1 , and in Step  2 , completion of input of the supplied paper selection (print processing condition) is awaited. If there is no input of a supplied paper selection, a notifying operation is performed to prompt the user for input of a supplied paper selection. That is, a message such as “Please select the supplied paper” is displayed on the display of the terminal device that the user is operating. 
     When the supplied paper selection is input, (judged ‘yes’ in Step  2 ), the procedure advances to Step  4 , and it is judged whether the amount of paper in the selected paper feed cassette  33  is greater than the number of print processing sheets or not. Then, if this judgment is ‘Yes’, then the solenoid  85  is kept non-electrified and print processing is executed for the paper (Step  9 ). After this print processing is executed, image forming is successively performed in turn while judging the presence or absence of something to be printed next, and when image forming is complete for all of the image data, a “standby state” is entered that waits for the next print request. 
     On the other hand, when ‘No’ is judged (judged that the amount of paper in the selected paper feed cassette  33  is lower than the number of print processing sheets) in Step  4 , the procedure advances to Step  5 , a current is sent through the solenoid  85 , sinking in the rod  86 , and causing the movable catch  84  to rotate in the direction that frees it from the fixed catch  83  (see  FIG. 7(   b )). Thus, the paper feed cassette  83  becomes released, and the paper feed cassette  33  is pushed out in the direction that it becomes uninstalled (the push-out direction) by the biasing force of the coil spring  81 . 
     And, along with this push-out operation of the paper feed cassette  33 , in Step  6 , a display signal is sent for producing a display for prompting a paper refill to the terminal device that sent out the print request signal. 
     After that, in Step  7 , it is judged whether or not the paper has been refilled, and when this judgment is ‘Yes’, the current flowing through the solenoid  85  is turned off, the rod  86  returns to a protruding state, and thus the movable catch  84  also enters a standing state. In this state, the paper feed cassette  33  is pushed in towards the main body of the apparatus with a manual operation by the user, and when the fixed catch  83  surmounts the movable catch  84  and is pressed in to a predetermined installed position, the fixed catch  83  is engaged by the movable catch  84 , and the installed state of the paper feed cassette  33  is preserved (see  FIG. 6  and  FIG. 7(   a )). 
     Effect of Example Embodiment 
     As explained above, in the present example embodiment, when the number of sheets of paper remaining in the paper feed cassette  33 , confirmed by the reflective optical sensor  7 , is lower than the requested number of image forming sheets, that is, in a circumstance in which paper will run out during execution if an image forming operation is executed as-is, without beginning an image forming operation, along with pushing the paper feed cassette out from an installed state toward an uninstalled state with the push-out mechanism  8 , a warning is given to the user by a warning means  94  to the effect that the number of sheets of recording paper is insufficient. Thus the user, after sending a print request, immediately confirms that a refill of the recording paper is necessary, and it is possible to immediately begin the work of refilling the paper without requiring the user to check the status of the compound machine  1 . Accordingly, when the refill recording paper is stored in a different location than the compound machine  1  is installed, it is possible for the user to go to the storage location of the refill recording paper to get recording paper, without going to the installed location of the compound machine  1 , then go to the installed location of the compound machine  1  and perform the work of refilling the paper. That is, the activity of approaching the installed location of the compound machine  1  and confirming that there is no paper, remaining prior to going to get recording paper from the storage location, is no longer necessary. After sending an image request signal from the terminal to the compound machine  1 , it is possible to allow the user to confirm the lack of paper within a short period of time. That is, after the user has sent an image request signal and before beginning separate work on that terminal, it is possible to prompt the user for a paper refill as necessary, and so it is possible to avoid temporarily interrupting work on the terminal. 
     Also, when performing a copy operation in the main compound machine  1 , if the number of recording sheets P stored in the paper feed cassette  33  is lower than the number of requested copy sheets, without beginning the copy operation, along with the paper feed cassette being slightly pushing out, a message such as “There is not enough paper” is displayed on the operating panel of the compound machine  1 . In this case as well, it is possible for the user to immediately begin the work of refilling the paper without checking inside of the paper feed cassette  33 . 
     Second Example Embodiment 
     Next is an explanation of a second example embodiment of the present technology. In the first example embodiment described above, the reflective optical sensor  7  was adopted as a sheet quantity checking means that checks the number of sheets of recording paper that are in the paper feed cassette  33 . This second example embodiment is a modified example of this sheet quantity checking means, and in other respects the configuration of this second example embodiment is the same as in the first example embodiment described above. Accordingly, only points differing from the first example embodiment will be explained. 
       FIG. 9  is a cross-sectional view that shows a part of the interior of the paper feed cassette  33  according to the present example embodiment, which shows the structure for checking the number of recording sheets in the paper feed cassette  33 . As shown in  FIG. 9 , the sheet quantity checking means  9  is provided with a direct current power source  91  that applies a direct current voltage across the aforementioned coil spring  33   c , rotating board  33   b , and paper leading edge matching portion  33   d , and an electrical current sensor that detects its electrical current value. 
     As previously stated, the position of rotation of the rotating board  33   b  is determined according to the number of sheets of recording paper P that are in the paper feed cassette  33 , and the greater the number of sheets of recording paper P, the further the position of rotation of the rotating board  33   b  moves downward. That is, as shown in  FIG. 9(   a ), when the number of sheets of recording paper P is small, the rotating board  33   b  makes contact in the vicinity of the upper edge portion of the paper leading edge matching portion  33   d . Thus, the electrical resistance across the aforementioned coil spring  33   c , rotating board  33   b , and paper leading edge matching portion  33   d  is comparatively large, and the electrical current value detected by the electrical current sensor  92  is detected as a small value. On the other hand, as shown in  FIG. 9(   b ), when the number of sheets of recording paper P is large, the rotating board  33   b  makes contact in the vicinity of the lower edge portion of the paper leading edge matching portion  33   d . Thus, the electrical resistance across the aforementioned coil spring  33   c , rotating board  33   b , and paper leading edge matching portion  33   d  becomes comparatively small, and the electrical current value detected by the electrical current sensor  92  is detected as a large value.  FIG. 10  shows the relationship between the number of sheets of paper in the paper feed cassette  33  and the electrical current value detected by the electrical current sensor  92 . 
     In this way, the present example embodiment effectively applies the fact that, from the related art, the rotating board  33   b  and the paper leading edge matching portion  33   d  are made of metal. By utilizing the fact that the electrical resistance changes according to the position of rotation of the rotating board  33   b , because the position at which the rotating board  33   b  makes contact with the paper leading edge matching portion  33   d  changes, it is possible to confirm the number of sheets of recording paper without requiring a special electric circuit. 
     Other Example Embodiments 
     In the example embodiments described above, the present technology was described with respect to its application in the multifunction-type image forming apparatus (compound machine)  1  including functions as a copy machine and printer and facsimile apparatuses. The present invention is not restricted to this, and can also be applied in an image forming apparatus provided with only some single function, or in another image forming apparatus. 
     And, in the example embodiments described above, a configuration was adopted wherein the number of sheets of paper in the paper feed cassette  33  is confirmed based on the electrical resistance from the reflective optical sensor  7  and the coil spring  33   c  to the paper leading edge matching portion  33   d . The present invention is not limited to this configuration; a configuration may also be adopted wherein the number of sheets of paper in the paper feed cassette  33  is confirmed based on the value of a counter that counts the number of sheets printed. For example, a configuration may be adopted in which the counter is reset in a state in which paper is fully stored in the paper feed cassette  33 , and afterwards the number of sheets of paper in the paper feed cassette  33  is confirmed by subtracting the number of sheets printed from the number of sheets when full. 
     In the above manner, in the present technology, when forming an image, if there are not enough sheets of paper remaining to satisfy that request, without executing that image forming operation, a paper refill is awaited, and the image forming operation begins after that paper refill. When waiting for this paper refill, along with prompting the user for the paper refill, the paper feed cassette is popped out and the lack of paper can easily be confirmed. Thus, the user can, after sending an image forming request, immediately confirm that a refill of the storage medium (paper) is necessary, and immediately begin the work of refilling the paper without the need to confirm the status of the image forming apparatus. Thus, the activity of approaching the installed location of the image forming apparatus and confirming that there is no paper remaining, prior to going to get recording paper from the storage location of the recording medium, is no longer necessary. And, it is possible to allow the user to confirm the lack of paper within a short period of time after sending an image request signal from a terminal to the image forming apparatus. That is, after the user has sent an image request signal and before beginning separate work on that terminal, it is possible to prompt the user for a paper refill as necessary, and so it is possible to avoid temporarily interrupting work on the terminal. 
     As a sheet quantity checking means, if the number of sheets of the storage medium stored in the paper feed cassette is confirmed by turning on electricity from a paper storage board made of metal to a matching portion, and detecting the electrical resistance from the paper storage board to the matching portion, which changes according to the height position of the paper storage board, it becomes possible to confirm the number of sheets of recording paper without requiring a special electric circuit, and lower cost can be achieved. 
     The present invention may be embodied in other forms without departing from the gist or essential characteristics thereof. The example embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein. 
     This application claims priority on Patent Application No. 2003-121899 filed in Japan on Apr. 25, 2003, the entire contents of which are hereby incorporated by reference. 
     INDUSTRIAL APPLICABILITY 
     The present technology is applicable to image forming apparatuses that can form an image; these are not limited to copy machines, printer and facsimile apparatuses, and the like.