Abstract:
An image forming apparatus of the present invention comprises a developing device to form a positive image by supplying toner to an image carrier, a toner residual amount detecting unit to detect residual tone amount that can be supplied from the developing device, a comparing unit to compare a set toner consumption that is consumed under set image forming conditions with the residual toner amount, an advance warning signal output unit to generate an advance warning signal for generation of the interruption during the image forming before starting the image forming under the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption)&gt;(Residual toner amount), and a display device to display the advance warning signal for generation of the interruption, and warns user the generation of interruption of the image forming operation in advance before starting the image forming operation and urges to prepare for avoiding the interruption of the operation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus of electro-photographic system such as copying machines, printers, etc, that is capable of efficient image forming when residual amount of toner to be supplied to electrostatic latent images formed on a photosensitive drum decreased. 
     2. Description of the Related Art 
     In a developing device used in an image forming apparatus of electro-photographic system for development using a so-called two-component developer comprising toner and carrier, toner density in the developing device is detected by an automatic toner sensor and according to the detected result, additional toner is supplied from a toner cartridge for maintaining the developing density at a desired level. 
     So far, residual toner amount in a toner cartridge was detected and when residual toner amount decreased to a specified near empty state, the near empty was displayed. In the case where a large volume of copying or printing was required, user once interrupts the image forming operation when recognized this near empty display, exchanged a toner cartridge. On the other hand, in the case of copying or printing of small volume, the image forming operation was continued and a toner cartridge was exchanged at the time when the toner empty was displayed. 
     Such the residual toner displayed device is similarly used in a cartridge type developing device using one-component toner. For example, an image forming apparatus that displays the number of residual formable sheets for the future by calculating the number of image sheets that are formable from residual tone amount for the future by detecting residual amount of one-component toner in a developing cartridge using an electrostatic capacity detecting system was disclosed in Japanese Patent Application No. 2001-83842. When the number of formable sheets is displayed, user exchanges a developing cartridge or supplies additional toner to the developing device according to the displayed device contents. 
     However, by such the conventional technology it is difficult to grasp whether a desired image forming operation can be made within residual toner amount, that is, within the number of formable image forming sheets before starting the image forming operation. In particular, when a desired image forming is for a large volume of original documents or it is desired to obtain a large amount of copies in the 2-in-1 mode or the 4-in-1 mode, even if the number of image formable sheets is simply displayed, user must compute and judge whether the desired image forming can be made within the displayed formable sheets. 
     Further, although the near toner empty is not displayed at the beginning when the image forming operation is started, the near toner empty may be displayed during the operation. In particular, if a desired image forming was voluminous, the near toner empty might be displayed during the operation in many cases and it was forced to interrupt the image forming operation. Further, when the operation was restarted, it became necessary to check the number of image formed copies already completed and reset the image forming conditions for remaining copies and thus, the operability of a copying machine could be lowered. Particularly, when the image forming operation is directed through a personal computer (PC) terminal such as a printer or when user was left from a copying machine in copying a large amount of sheets, user was not aware of the interruption of the image forming operation and a copying machine was left in the interrupted state and its productive could be lowered. 
     Accordingly, it is possible for user to easily recognize whether a desired image forming operation that is going to start is within residual toner amount before starting the image forming operation. When toner becomes empty during the operation, it is desired to urge user to take action for avoiding the interruption before starting the image forming operation and avoid the interruption of the operation, thereby improving operability and productivity. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an image forming apparatus that has high operability as well as productivity by urging user to take action to avoid the image forming operation from being interrupted during the operation for empty of toner prior to starting the image forming operation. 
     According to the embodiment of the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a developing device to form a positive image by supplying toner to an image carrier; a residual toner amount detecting unit to detect residual toner amount that can be supplied from the developing device; a comparing unit to compare a set toner consumption that is consumed under set image forming conditions with the residual toner amount; an advance warning signal output unit to generate an advance warning signal for generation of interruption during the image forming before starting the image forming under the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption)&gt;(Residual toner amount); and a display device for displaying the advance warning signal for generation of interruption. 
     Further, according to the embodiment of the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a developing device to form a developed image by supplying toner to an image carrier; a residual toner detecting unit to detect residual toner amount retained in the developing device; a comparing unit to comparing a set toner consumption that is consumed under set image forming conditions with the residual toner amount; a substitute condition changing unit to changing substitute image forming conditions to those that are approximate to the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption)&gt;(Residual toner amount), that is, when the expected toner consumption is within the residual toner amount; and a display device to display the substitute image forming conditions. 
     Further, according to the embodiment of the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a toner cartridge containing toner; a developing device to forming a developed image by supplying the toner supplied from the toner cartridge to an image carrier; a residual toner amount detecting unit to detect residual toner amount in the toner cartridge; a comparing unit to compare set toner consumption that is consumed under the set image forming conditions with the residual toner amount; a substitute condition changing unit for changing the substitute image forming condition to substitute image forming conditions approximate to the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption)&gt;(Residual toner amount), that is, when the expected toner consumption is within the residual toner amount, and a display device to displaying the substitute image forming conditions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing an image forming system in an embodiment of the present invention; 
     FIG. 2 is a schematic diagram showing an image forming unit in an embodiment of the present invention; 
     FIG. 3 is a schematic perspective view showing a toner cartridge and a rotary driving device in an embodiment of the present invention; 
     FIG. 4 is a block diagram showing the control system of the image forming system in the embodiment of the present invention; and 
     FIG. 5 is a flowchart for showing an advance warning of interruption and substitute print conditions in the embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the present invention will be described below in detail referring to attached drawings. FIG. 1 is a schematic block diagram showing an image forming system  1  using a printer  10  as an image forming apparatus. On the top of the printer  10 , an automatic document feeder  11  (hereinafter, abbreviated to ADF) and an mage reading scanner  12  are provided. Further, in the main body of the printer  10 , a paper supply portion  15  including an image forming unit  13 , first through fourth paper cassettes  16   a ˜ 16   d , a manual paper supply tray  17  and a duplex unit  18 , a fixing device  7  and a paper discharge device  8  are provided. This printer  10  is capable of forming images in a single mode, duplex mode, 2-in-1 mode, and 4-in-1 mode. 
     As shown in FIG. 2, the image forming unit  13  has a charger  21 , an exposure unit  24  to which laser beam  22  is applied from a laser unit  23  according to image data read by the image reading scanner  12  or image data from PC or facsimile, a developing device  26  that accommodates two-component toner comprising toner and carrier and supplies the two-component toner to a photosensitive drum  20  by a developing roller  26   a , a transfer/separation charger  27 , a cleaner  28  and a charge eliminating lamp  30  around the photosensitive drum  20  that is an image carrier in its rotating direction. Further,  31  is a toner cartridge for supplying toner to the developing device  26 . Toner is supplied from the toner cartridge  31  to the developing device  26  to a rate of toner at about 5% against carrier at about 95%. The rate of toner in the developing device  26  is constantly supervised by a magnetic sensor (not shown), etc. 
     The printer  10  that has such the image forming unit  13  is uniformly charged by the main charger  21  according to the rotation of the photosensitive drum  20  in the arrow direction “s”. Then, the laser beam  22  is applied to the drum  20  from the laser unit  23  corresponding to image data and a latent image corresponding to the image data is formed on the photosensitive drum  20 . Further, toner is supplied to this latent image from the developing device  26  and a toner image that is a positive image is formed on the photosensitive drum  20 . 
     On the other hand, a sheet of paper that is a transfer material (not shown) taken out of a paper supply unit  14  synchronous with the formation of a toner image, is conveyed to the position of the transfer/separation charger  27  and the toner image formed on the photosensitive drum  20  is transferred on the transfer material by the transfer/separation charger  27  and thereafter, fixed in a fixing device  7  and discharged to the discharge device  8 . The image forming on a transfer material is thus completed. 
     Next, the toner cartridge  31  will be described in detail. The toner cartridge  31  is in a nearly cylindrical shape and a spiral convex portion (not shown) is formed on the inner surface. On the surface of the tip of the toner cartridge  31 , a toner supply port  32  is formed. The toner cartridge  31  moves toner in the inside to the toner support port  32  by rotating in the arrow direction “A” as shown in FIG.  2  and FIG. 3, discharges a specified amount of toner from the toner supply port  32  and supplies to a supply port  26   b  of the developing device  26 . 
     When installing in the printer  10 , the toner cartridge  31  is compressed in a holder  34   a  of a toner supply portion  34  at the printer  10  side and is connected to a driving motor  36  that is mounted to a support plate  34   c  and a rotary driving device  37  including a belt driving mechanism  37   a  for deceleration and a gear driving mechanism  37   b , and is driven by the rotary driving device  37  in the arrow direction “A”. Further, the toner supply portion  34  has a guide plate to lead toner to the supply port  26   b  of the developing device  26 . 
     On the surface of the rear edge of the toner cartridge  31 , a flanged switch  38  is formed. Near the rear end of the toner cartridge  31 , there is provided a photo-sensor  40  that is a residual amount detector for detecting residual amount of toner in the toner cartridge  31  and the number of revolutions of the toner cartridge  31  is detected by the passing of the flanged switch  38 . That is, as the toner cartridge  31  supplies a specified amount of toner to the developing device  26  through the toner supply port  32  whenever the toner cartridge rotates by one turn in the arrow direction “t”, a printer CPU  51  that will be described later computes toner consumption and the residual mount of toner in the toner cartridge  31  is computed by subtracting the toner consumption from the capacity of the toner cartridge  31 . 
     Next, FIG. 4 shows the structure of the control system of the image forming system  1 . A CPU  50  that controls the entirety of the image forming system  1  is connected with the printer CPU  51  for controlling the printer  10 , a scanner CPU  52  for controlling the scanner  12 , and a controller  54  that has a PRT board  54   a  and a FAX board  54   b  that are connected to a printer and a facsimile that are external terminals of a control panel  53 . The scanner CPU  52  is connected to a Charge Coupling Device  56  (hereinafter, abbreviated to CCD) of the scanner  12  and the ADF  11  for controlling them. The control panel  53  is provided with a control portion  57  comprising a ten-key, a print key, etc. and a displayed device  58 . 
     To the printer CPU  51 , motor drivers  61  for driving a motor  36  for driving the photosensitive drum  20 , the developing roller  26   a  and the toner cartridge  31  through the image forming control CPU  60  that controls the image forming unit  13 , and switches/sensors  62  for detecting various operation timings including the photo-sensor  40  for detecting the rotation of the toner cartridge  31  are connected. Further, a non-volatile memory  63  (hereinafter, abbreviated to NV-RAM) for storing the number of revolutions of the toner cartridge  31  and computed results of the printer CPU  51  is connected to the printer CPU  51 . Further, a paper supply control CPU  64  for controlling the paper supply portion  14  and a laser CPU  66  for controlling the laser unit  23  are connected to the printer CPU  51 . This printer CPU  51  has a set toner consumption computing unit  51   a , a comparing unit  51   b , an advance warning signal output unit  51   c , a substitute condition changing unit  51   d , a number of formable sheets changing unit  51   f , a number of set sheets computing unit  51   g  and further, a ROM  51   h  for storing mean toner consumption for each print size. 
     Next, the operations will be described. First, when toner becomes empty and it becomes necessary to change the toner cartridge  31  in the printer  10 , the number of revolutions of the toner cartridge  31  stored in the NV-RAM  63  is cleared to zero (0) when the toner cartridge  31  is exchanged with a new cartridge. Thereafter, while the printer is operated, the toner cartridge  31  is rotated so as to maintain toner density in the developing device  26  at about 5% against carrier of about 95% and toner is supplied to the developing device. The number of revolutions of the toner cartridge  31  is detected by the photo-sensor and stored in the NV-RAM  63 . 
     To operate the printer, various kinds of print conditions are first set by user through the operation unit  57  of the control panel  53 . For example, the normal single mode or duplex mode, 2-in-1 mode or 4-in-1 mode is selected for the image forming mode, a print size is selected, and after setting the number of prints and an image forming magnification, the print condition setting is decided by turning the print key (not shown) ON. 
     To make the judgment as to whether the print operation under this decided print conditions is interrupted for the reason of toner empty can be known when the (Residual toner amount) of the toner cartridge  31  is compared with the set toner consumption under the set print conditions. However, the (Residual toner amount) can be converted into the number of printable sheets that is the number of image formable sheets and therefore, in this embodiment, (Number of printable sheets) is converted from (Residual toner amount) at a formable sheet changing unit  51   f  of the printer CPU  51  and further, (Number of set print sheets) that is the number of set image printable sheets is computed from the set print conditions at the set number of sheet computing unit  51   g , and whether the print operation is interrupted is checked by comparing (Number of set print sheets) with (Number of printable sheets). 
     That is, as (Toner capacity) of the toner cartridge  31  is fixed and the toner amount supplied to the developing device  26  through the toner supply port  32  at one turn of the toner cartridge is constant, if the number of revolutions α of the toner cartridge  31  up to the present detected by the photo-sensor  40  is known, the (Toner supply amount up to the present) is computed according to the following formula: 
     (Supplied toner amount/one turn)×α=(Toner supplied amount up to the present). Accordingly, (Residual toner amount) is computed from the following formula: 
     (Toner capacity)−(Supplied toner amount up to the present)=(Residual toner amount). 
     Further, using (Mean toner consumption for every print size) stored in the ROM  51   h , (Residual toner amount)/(Specified print size mean toner consumption)=(Number of printable sheets) is computed by the number of formable sheets changing unit  51   f  of the printer CPU  51  and by computing (Number of original documents)×(Number of print sheets)=(Number of set print sheets), (Number of set print sheets) is compared with (Number of printable sheets) by the comparing unit  51   b  of the printer CPU  51 . 
     As a result, when (Number of set print sheets)&lt;(Number of printable sheets), the print operation of the printer  10  is immediately started according to the set print conditions. 
     On the other hand, when (Number of set print sheets)&gt;(Number of printable sheets), an advance warning signal indicating that the print interruption is generated for toner empty is output to and displayed on the displayed device  58  of the control panel  53  from the advance warning signal output unit  51   c . Further, at the same time, when (Number of set print sheets)&gt;(Number of printable sheets), the substitute condition changing unit  51   d  of the printer CPU  51  converts the print conditions set by user into plural patterns of substitute print conditions that are substitute image forming conditions approximate to the user set conditions within (Residual toner amount) of the toner cartridge  31  and displayed devices on the displayed device  58  of the control panel  53 . 
     The contents of the plural patterns of substitute print conditions are such that (1) the number of print sheets is reduced, (2) the image forming magnification is lowered, (3) the image density is made thin or (4) the image forming mode is changed from the normal single mode to 1 in 1 more or 4-in-1 mode. 
     As a result, after confirming the warning for generation of interruption and substitute print conditions displayed on the display device  58  before starting the print operation, it becomes possible for user to select plural patterns of the print operation, for example, to perform the print operation under desired print conditions after exchanging a toner cartridge with new one when necessary or to perform the print operation after resetting the displayed substitute print conditions as new print conditions or to perform the print operation under the set print conditions until the toner empty becomes definite by turning on the print key (not shown) on the operation unit  57  again disregarding the display on the display device  58 . 
     Next, the above operation will be described referring to the flowchart shown in FIG.  5 . In Step  100 , when print conditions are set from the operation unit  57  of the control panel  53  when starting the print operation, the data of set print conditions are input to the printer CPU  51  from the system CPU  50 . Then, in Step  101 , (Number of set print sheets) is computed using the number of set sheet computing unit  51   g  of the printer CPU  51  and in Step  102 , (Number of printable sheets) is computed from (Residual toner amount) using the number of printable sheets changing unit  51   f  of the printer CPU  51 . 
     In Step  103 , (Number of set print sheets) and (Number of printable sheets) are compared by using the comparing unit  51   b  of the printer CPU  51 . When (Number of set print sheets)&lt;(Number of printable sheets), the operation goes to Step  104  and the print operation is started under the print conditions set by user. When (Number of print sheets)&gt;(Number of printable sheets) in Step  103 , the operation goes to Step  106  and an advance warning signal for the generation of print interruption is output to the system CPU  50  from the advance warning signal output unit  51   c  of the printer CPU  51  and the print interruption generating warning is displayed on the displayed device  58  of the control panel  53 . 
     Then, going to Step  107 , the substitute print conditions are converted into plural patterns using the substitute condition changing unit  51   d  of the printer CPU  51 , the substitute print conditions are input to the system CPU  50  from the printer CPU  51  and the substitute print conditions are displayed on the displayed device  58  of the control panel  53 . 
     Hereafter, when a specified time elapsed in Step  110 , the system judges that user suspends the print operation and returns to the ready state. When the specified time is not elapsed in Step  110 , waiting that new print conditions are set by user in Step  111 , returns to Step  100 . 
     That is, when the interruption generating warning and the substitute print conditions are displayed on the display device  58  in Step  106  or Step  108 , user selects and executes an action that is most required from the suspension of printing, the printing under the substitute print conditions or the printing under the set print conditions. 
     When the system is constructed as described above, if it was revealed that the residual toner amount in the toner cartridge  31  is detected less and the print operation is forced to be interrupted for toner empty during the printing under the print conditions set by user, before starting the print operation, the advance warning for generation of interruption is displayed on the display device  58  and further, substitute print conditions are displayed. Accordingly, user is able to easily recognize the generation of the interruption before starting the print operation, and taking an action to avoid generation of the interruption according to the desired print contents and improve the operability by avoiding the interruption of the print operation. Furthermore, as substitute print conditions are displayed, a method for action to avoid the print interruption can be easily grasped, the method for action can be easily set, and the operability of the printing is further improved. Furthermore, as the generation of the print interruption is warned in advance, it is avoided that user lefts the printer in the interrupted state for a long period without aware of the interruption of the print operation when left from the printer  10  as before and the productivity of the printer can be improved. 
     The present invention is not limited to the embodiment described above but can be varied without departing from the spirit and scope thereof and for, example, an image forming apparatus may be a copying machine or can be optionally a composite machine that has functions of copying machine, printer, facsimile, etc. Further, a developing device also can be of cartridge type using one component toner. In addition, residual toner amount can be detected optionally by detecting an electrostatic capacity in a toner cartridge or a developing cartridge. Further, when the generation of the interruption of the image forming operation is revealed, it may be displayed to user only by the voice for the advance notice of the generation of interruption or the lighting of a luminous device. 
     Further, number of patterns or contents of substitute image forming conditions are also not limited and when, for example, a finisher equipped with the folding and binding function is used, substitute image forming conditions can be displayed, for example, by changing the normal single mode to the folding and binding mode, and substitute image forming conditions may be mixed as described in the embodiment. Further, to check whether the set image forming operation is forced to be interrupted, a set toner consumption may be compared with a residual toner amount by computing the set toner consumption from the set image forming conditions. 
     According to the present invention as described above in detail, when the image forming operation under set image forming conditions is interrupted for empty of toner as the detected residual toner amount is small, an advance warning for generation of the interruption is displayed to user before starting the image forming operation. Accordingly, it is possible to take an action to avoid the interruption before starting the image forming operation and the improved operability of the system is obtained by avoiding the interruption of the operation. Further, the operation is no longer left in the interrupted state as user is not aware of the interruption of the image forming operation and it is possible to improve productivity of the image forming apparatus.