Patent Publication Number: US-9904207-B2

Title: Image formation apparatus, image formation system, control method, and non-transitory recording medium

Description:
This application is based on Japanese Patent Application No. 2015-244281 filed with the Japan Patent Office on Dec. 15, 2015, the entire content of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to control of an image formation apparatus and particularly to control of an image formation apparatus of an electrophotography type. 
     Description of the Related Art 
     An image formation apparatus of an electrophotography type has widely been used. The image formation apparatus of the electrophotography type performs, as print processing, evenly charging a photoconductor while the photoconductor is rotated, forming an electrostatic latent image by exposing the photoconductor, attaching toner to the electrostatic latent image on the photoconductor, and transferring a toner image on the photoconductor to a printed matter. 
     A toner bottle can be attached to an image formation apparatus. The toner bottle supplies toner to a sub hopper. The sub hopper temporarily stores toner supplied from the toner bottle and supplies the toner to a development apparatus. As the toner is supplied from the development apparatus to a photoconductor, a toner image is developed on the photoconductor. 
     As a remaining amount of toner in the toner bottle decreases, a user of the image formation apparatus replaces the toner bottle. If the toner bottle is replaced with a large amount of toner remaining, toner will be wasted. Therefore, toner which remains in the toner bottle is preferably supplied to the sub hopper before the toner bottle is replaced. 
     In connection with a method of supplying toner from a toner bottle, Japanese Laid-Open Patent Publication No. 2009-210743 discloses an image forming apparatus “that is capable of reducing work burdens imposed on a user in terms of toner cartridge replacement.” Japanese Laid-Open Patent Publication No. 2002-132039 discloses an image recording apparatus “capable of using toner without waste by preventing such a disadvantage that determination as toner not being left is made with a large amount of usable toner remaining.” Japanese Laid-Open Patent Publication No. 2013-97005 discloses an image formation apparatus “which determines whether or not replacement of a toner bottle is necessary by sensing load imposed on a toner bottle motor.” 
     In order to decrease a remaining amount of toner by the time of replacement of a toner bottle, toner is preferably supplied to a sub hopper as much as possible before replacement of the toner bottle. It is generally difficult, however, to accurately predict timing of replacement of a toner bottle. 
     In order to decrease a remaining amount of toner by the time of replacement of a toner bottle, it is also possible to periodically supply toner in a toner bottle to a sub hopper as much as possible. If toner is supplied to the sub hopper with a large amount of toner remaining in the toner bottle, however, an amount of supply of toner will not be stable and toner may spill out of the sub hopper. 
     Therefore, an image formation apparatus capable of decreasing a remaining amount of toner by the time of replacement of a toner bottle while supply of toner from the toner bottle to a sub hopper is stabilized has been desired. Patent Documents 1 to 3 do not disclose an image formation apparatus which achieves both decrease in remaining amount of toner by the time of replacement of a toner bottle and stabilization of supply of toner from the toner bottle to a sub hopper. 
     SUMMARY OF THE INVENTION 
     An object in one aspect of the present disclosure is to provide an image formation apparatus capable of decreasing a remaining amount of toner by the time of replacement of a toner bottle while supply of toner from the toner bottle to a sub hopper is stabilized. An object in another aspect is to provide an image formation system capable of decreasing a remaining amount of toner by the time of replacement of a toner bottle while supply of toner from the toner bottle to a sub hopper is stabilized. An object in yet another aspect is to provide a control method which allows decrease in remaining amount of toner by the time of replacement of a toner bottle while supply of toner from the toner bottle to a sub hopper is stabilized. An object in still another aspect is to provide a non-transitory recording medium storing a control program which allows decrease in remaining amount of toner by the time of replacement of a toner bottle while supply of toner from the toner bottle to a sub hopper is stabilized. 
     According to one aspect, an image formation apparatus includes a toner bottle, a storage portion which temporarily stores toner supplied from the toner bottle, a development portion which receives supply of toner from the storage portion, a first detector which detects a remaining amount of toner in the toner bottle, a second detector which detects an empty space for toner in the storage portion, and a controller which has toner supplied from the toner bottle to the storage portion each time the empty space exceeds a prescribed threshold value. The controller lowers the prescribed threshold value from a current value when a remaining amount of toner in the toner bottle is smaller than a prescribed amount. 
     Preferably, the controller lowers the prescribed threshold value as the remaining amount of toner in the toner bottle is smaller. 
     Preferably, the image formation apparatus further includes a display. The display shows contents for having a new toner bottle prepared when the remaining amount of toner is smaller than the prescribed amount. 
     Preferably, the display shows contents for inviting replacement of the toner bottle when the remaining amount of toner is smaller than a predetermined amount smaller than the prescribed amount. 
     Preferably, the image formation apparatus further includes a prohibition unit which prohibits printing by the image formation apparatus when the remaining amount of toner is smaller than the predetermined amount and when the empty space exceeds the prescribed threshold value. 
     Preferably, the image formation apparatus further includes a setting unit which accepts whether or not to activate change in prescribed threshold value by the controller. 
     Preferably, the image formation apparatus further includes a setting unit which accepts setting of the prescribed threshold value. 
     Preferably, the image formation apparatus further includes a communication unit which transmits a request for ordering a new toner bottle to a server when the remaining amount of toner is smaller than the prescribed amount. 
     Preferably, the communication unit can receive a command for transmitting the request to the server from another image formation apparatus or the server. The controller lowers the prescribed threshold value from the current value based on reception of the command. 
     Preferably, the controller lowers the prescribed threshold value from the current value based on transmission of the request to the server. 
     Preferably, the image formation apparatus further includes a storage unit which holds a history of replacement of the toner bottle and an estimation unit which estimates next timing of replacement of the toner bottle based on the history of replacement. The controller lowers the prescribed threshold value as the next timing of replacement is nearer. 
     According to another aspect, an image formation system including a plurality of image formation apparatuses and a server which communicates with the plurality of image formation apparatuses is provided. Each of the image formation apparatuses includes a toner bottle, a storage portion which temporarily stores toner supplied from the toner bottle, a development portion which receives supply of toner from the storage portion, a first detector which detects a remaining amount of toner in the toner bottle, a second detector which detects an empty space for toner in the storage portion, a first controller which has toner supplied from the toner bottle to the storage portion each time the empty space exceeds a prescribed threshold value, and a communication unit which transmits a request for ordering a new toner bottle to the server when a remaining amount of toner in the toner bottle is smaller than a prescribed amount. The server includes a second controller which performs, in response to reception of the request from one image formation apparatus among the plurality of image formation apparatuses, processing for ordering a new toner bottle for another image formation apparatus which satisfies a prescribed ordering condition among the plurality of image formation apparatuses and the one image formation apparatus and gives a mode switching instruction to instruct the image formation apparatus for which the server has performed the ordering processing to switch to a mode for lowering the prescribed threshold value. The first controller lowers the prescribed threshold value from a current value in response to the mode switching instruction from the server. 
     According to yet another aspect, a method of controlling an image formation apparatus which communicates with a server is provided. The image formation apparatus includes a toner bottle, a storage portion which temporarily stores toner supplied from the toner bottle, and a development portion which receives supply of toner from the storage portion. The method includes detecting a remaining amount of toner in the toner bottle, detecting an empty space for toner in the storage portion, supplying toner from the toner bottle to the storage portion each time the empty space exceeds a prescribed threshold value, the image formation apparatus transmitting a request for ordering a new toner bottle to the server when a remaining amount of toner in the toner bottle is smaller than a prescribed amount, the server searching for another image formation apparatus which satisfies a prescribed ordering condition among a plurality of the image formation apparatuses in response to reception of the request from one image formation apparatus among the plurality of image formation apparatuses, the server performing processing for ordering a new toner bottle for the one image formation apparatus and another image formation apparatus which satisfies the prescribed ordering condition, the server giving a mode switching instruction instructing the image formation apparatus for which the server has performed the ordering processing to switch to a mode for lowering the prescribed threshold value, and the image formation apparatus lowering the prescribed threshold value from a current value in response to the mode switching instruction from the server. 
     According to still another aspect, a control program executed by a server which communicates with a plurality of image formation apparatuses is provided. The image formation apparatus includes a toner bottle, a storage portion which temporarily stores toner supplied from the toner bottle, a development portion which receives supply of toner from the storage portion, a first detector which detects a remaining amount of toner in the toner bottle, a second detector which detects an empty space for toner in the storage portion, a controller which has toner supplied from the toner bottle to the storage portion each time the empty space exceeds a prescribed threshold value, and a communication unit which transmits a request for ordering a new toner bottle to the server when a remaining amount of toner in the toner bottle is smaller than a prescribed amount. The control program causes the server to perform searching, in response to reception of the request from one image formation apparatus among the plurality of image formation apparatuses, for another image formation apparatus which satisfies a prescribed ordering condition among the plurality of image formation apparatuses, performing processing for ordering a new toner bottle for the one image formation apparatus and another image formation apparatus which satisfies the prescribed ordering condition, and instructing the image formation apparatus for which the server has performed the ordering processing to switch to a mode lower in the prescribed threshold value. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a process for supplying toner when a remaining amount of toner in a toner bottle is large. 
         FIG. 2  is a diagram showing a process for supplying toner when a remaining amount of toner in the toner bottle is small. 
         FIG. 3  is a diagram showing one example of an apparatus configuration of an image formation apparatus according to a first embodiment. 
         FIG. 4  is a diagram showing a cross-sectional view of a sub hopper and a toner bottle. 
         FIG. 5  is a diagram showing a replenishment mechanism further added to the apparatus configuration in  FIG. 4 . 
         FIG. 6  is a diagram showing one example of a functional configuration of the image formation apparatus according to the first embodiment. 
         FIG. 7  is a diagram showing one example of a manner of representation on the image formation apparatus in accordance with a remaining amount of toner in the toner bottle and the sub hopper. 
         FIG. 8  is a flowchart showing a part of processing performed by the image formation apparatus according to the first embodiment. 
         FIG. 9  is a block diagram showing a main hardware configuration of the image formation apparatus according to the first embodiment. 
         FIG. 10  is a diagram showing change in remaining amount of toner in the sub hopper in the image formation apparatus according to the first embodiment and an image formation apparatus according to a comparative example. 
         FIG. 11  is a diagram showing one example of a system configuration of an image formation system according to a second embodiment. 
         FIG. 12  is a flowchart showing processing for ordering a toner bottle by the server. 
         FIG. 13  is a sequence diagram showing a flow of data between the image formation apparatus and the server. 
         FIG. 14  is a diagram showing one example of a functional configuration of the image formation apparatus according to a third embodiment. 
         FIG. 15  is a diagram showing contents in a history of replacement of a toner bottle. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Each embodiment according to the present invention will be described hereinafter with reference to the drawings. In the description below, the same elements and components have the same reference characters allotted. Their label and function are also identical. Therefore, detailed description thereof will not be repeated. Each embodiment and each modification described below may selectively be combined as appropriate. 
     First Embodiment 
     [Method of Supplying Toner] 
     A method of supplying toner in an image formation apparatus  100  according to the present embodiment will be described with reference to  FIG. 1 .  FIG. 1  is a diagram showing a process for supplying toner when a remaining amount of toner in a toner bottle  70  is large.  FIG. 2  is a diagram showing a process for supplying toner when a remaining amount of toner in toner bottle  70  is small. 
     As shown in  FIGS. 1 and 2 , image formation apparatus  100  includes toner bottle  70  which holds toner, a sub hopper  72  (a storage portion), and a development apparatus  75 . Toner bottle  70  supplies toner to sub hopper  72 . Sub hopper  72  temporarily stores toner supplied from toner bottle  70 . Development apparatus  75  receives supply of toner from sub hopper  72  and develops a toner image in accordance with an electrostatic latent image onto a photoconductor  40  which will be described later. 
     Image formation apparatus  100  can detect a remaining amount of toner in toner bottle  70  with a first detector  152  (see  FIG. 6 ) which will be described later. Image formation apparatus  100  can detect an empty space for toner in sub hopper  72  with a second detector  154  (see  FIG. 6 ) which will be described later. 
     The empty space here refers to an amount of toner which can be supplied to sub hopper  72 . The empty space corresponds to a value calculated by subtracting a current remaining amount of toner from an amount of toner in a full state. Since the “empty space for toner” and the “remaining amount of toner” correlate with each other, when the term “empty space for toner” is used, a concept of the “remaining amount of toner” may also be encompassed, and when the term “remaining amount of toner” is used, a concept of the “empty space for toner” may also be encompassed. 
     As shown in  FIG. 1 , when the remaining amount of toner in toner bottle  70  is equal to or greater than a threshold value ThA, image formation apparatus  100  supplies toner from toner bottle  70  to sub hopper  72  each time an empty space for toner in sub hopper  72  exceeds a threshold value Th 1 . As shown in  FIG. 2 , image formation apparatus  100  lowers threshold value Th 1  to a threshold value Th 2  when the remaining amount of toner in toner bottle  70  is smaller than threshold value ThA. 
     Thus, when the remaining amount of toner in toner bottle  70  is small, image formation apparatus  100  can increase a frequency of supply of toner from toner bottle  70  to sub hopper  72 . When the remaining amount of toner in toner bottle  70  is small, replacement of toner bottle  70  is more likely. When a frequency of supply to sub hopper  72  is increased here, image formation apparatus  100  can decrease the remaining amount of toner by the time of replacement of toner bottle  70 . 
     When the remaining amount of toner in toner bottle  70  is large, an amount of toner supplied from toner bottle  70  to sub hopper  72  at one time may be irregular and unstable. Image formation apparatus  100  increases a frequency of supply of toner after the remaining amount of toner in toner bottle  70  becomes small. Therefore, toner can be supplied to sub hopper  72  in a stable manner. 
     Though a method of controlling supply of toner to sub hopper  72  based on threshold values in two stages of threshold value Th 1  and threshold value Th 2  is described with reference to the example in  FIG. 2 , image formation apparatus  100  may control supply of toner to sub hopper  72  based on threshold values in three or more stages. For example, image formation apparatus  100  may lower a value for threshold value Th 1  as the remaining amount of toner in toner bottle  70  is smaller. Threshold value Th 1  is lowered in accordance with a remaining amount of toner in toner bottle  70 . Thus, as the remaining amount of toner in toner bottle  70  is smaller, a frequency of supply of toner to sub hopper  72  is increased. Consequently, image formation apparatus  100  can more reliably decrease a remaining amount of toner by the time of replacement of toner bottle  70 . 
     [Apparatus Configuration of Image Formation Apparatus  100 ] 
     An apparatus configuration of image formation apparatus  100  according to the first embodiment will be described with reference to  FIGS. 3 to 5 .  FIG. 3  is a diagram showing one example of an apparatus configuration of image formation apparatus  100 .  FIG. 4  is a diagram showing a cross-sectional view of sub hopper  72  and toner bottle  70 .  FIG. 5  is a diagram showing a replenishment mechanism  71  further added to the apparatus configuration in  FIG. 4 . 
       FIG. 3  shows image formation apparatus  100  as a color printer. Though image formation apparatus  100  as the color printer is described below, image formation apparatus  100  is not limited to the color printer. For example, image formation apparatus  100  may be a monochrome printer or a multi-functional peripheral (MFP) of a monochrome printer, a color printer, and a FAX as being combined. 
     Image formation apparatus  100  includes an image reader  10  which reads an image of a document and a printer  20  which prints the read image. 
     Image reader  10  reads a document placed on a glass plate (not shown) by moving a scanner. An image obtained by reading the document is decomposed into three colors of red (R), green (G), and blue (B), and converted to an electric signal by a charge coupled device (CCD) image sensor (not shown). Consequently, image data of each color of R, G, and B is obtained. 
     The image data for each color component obtained by image reader  10  is subjected to various processing in a control device  102  and converted to image data of each reproduction color of cyan (C), magenta (M), yellow (Y), and black (K). 
     Each piece of image data is stored in an image memory  34  in control device  102  for each reproduction color, subjected to correction of position displacement, and thereafter read for each one scanning line in synchronization with supply of a document, so that a signal for driving a light emitting diode is output. 
     Documents are taken out one by one from a paper feed tray  61  by a paper feed roller  62  and sent in synchronization with an intermediate transfer belt  53  which will be described later. 
     Intermediate transfer belt  53  is looped over a drive roller  51  and a driven roller  52 . Driven roller  52  is biased to the left in  FIG. 3  by a spring (not shown), so that tensile force is applied to intermediate transfer belt  53 . As a main body controller  31  drives a transfer motor  54 , drive roller  51  rotates counterclockwise. Consequently, intermediate transfer belt  53  also rotates counterclockwise. 
     Development apparatuses  75 Y,  75 M,  75 C, and  75 K of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are arranged below intermediate transfer belt  53  at a prescribed interval. Photoconductors  40 Y,  40 M,  40 C, and  40 K are provided to face development apparatuses  75 Y,  75 M,  75 C, and  75 K, respectively. Development apparatuses  75 Y,  75 M,  75 C, and  75 K are hereinafter also collectively referred to as a development apparatus  75  (see  FIG. 1 ). Photoconductors  40 Y,  40 M,  40 C, and  40 K are also collectively referred to as a photoconductor  40 . 
     Transfer rollers  42 Y,  42 M,  42 C, and  42 K are arranged at respective positions opposed to photoconductor  40  of development apparatus  75 . Transfer rollers  42 Y,  42 M,  42 C, and  42 K are hereinafter also collectively referred to as a transfer roller  42 . 
     When intermediate transfer belt  53  passes between photoconductor  40  and transfer roller  42 , a toner image formed on a surface of photoconductor  40  is primarily transferred onto intermediate transfer belt  53 . 
     A document conveyed from paper feed tray  61  passes along a dashed line. A and passes through a nip portion between intermediate transfer belt  53  and a secondary transfer roller  55 . Here, the toner image on intermediate transfer belt  53  is secondarily transferred to the document. Then, the document is conveyed to a fixation apparatus  80 . Fixation apparatus  80  heats and pressurizes the document and fixes the toner image to the document. Thereafter, the document is ejected to the outside of the apparatus. 
     Toner which remains on intermediate transfer belt  53  is recovered by a transfer belt cleaner  91  and stored in a waste toner box  92 . 
     Development apparatuses  75 Y,  75 M,  75 C, and  75 K are provided with sub hoppers  72 Y,  72 M,  72 C, and  72 K which replenish a certain amount of toner of respective colors, respectively. Sub hoppers  72 Y,  72 M,  72 C, and  72 K are also hereinafter collectively referred to as sub hopper  72  (see  FIG. 1 ). Toner is supplied to development apparatus  75  via sub hopper  72 . 
     Toner bottles  70 Y,  70 M,  70 C, and  70 K are removably provided above sub hoppers  72 Y,  72 M,  72 C, and  72 K, respectively. Toner bottles  70 Y,  70 M,  70 C, and  70 K are also hereinafter collectively referred to as toner bottle  70  (see  FIG. 1 ). Toner bottle  70  holds toner and supplies toner to sub hopper  72  each time toner in sub hopper  72  decreases. When toner in toner bottle  70  runs out, toner bottle  70  is replaced with a new toner bottle  70  by a user. 
     Development apparatus  75  is provided with a sensor (not shown) for detecting a concentration of toner. When a concentration of toner in development apparatus  75  is lower than a prescribed value, a gear  703  of sub hopper  72  for replenishment to the development apparatus rotates forward and development apparatus  75  is replenished with toner, so that a predetermined concentration of toner is attained. 
     A supply port  723   a  of a cap portion  723  is located above sub hopper  72 . In sub hopper  72 , a float member  704  for detecting a level of an upper surface of toner is swingably provided around a shaft  704   a . A remaining amount of toner in sub hopper  72  is detected in accordance with the level of the upper surface detected by float member  704 . A cam  702  which rotates together with an agitation shaft is provided below float member  704 , and float member  704  vertically swings with rotation of cam  702 . Toner in sub hopper  72  is supplied to development apparatus  75  through replenishment mechanism  71 . 
     [Functional Configuration of Image Formation Apparatus  100 ] 
     A function of image formation apparatus  100  according to the first embodiment will be described with reference to  FIG. 6 .  FIG. 6  is a diagram showing one example of a functional configuration of image formation apparatus  100  according to the first embodiment. 
     As shown in  FIG. 6 , image formation apparatus  100  includes toner bottle  70 , sub hopper  72 , development apparatus  75 , and control device  102 . Control device  102  is implemented, for example, by a central processing unit (CPU), and includes as a functional configuration, first detector  152 , second detector  154 , a supply controller  160 , a first setting unit  170 , a second setting unit  172 , and a prohibition unit  180 . Control device  102  stores as data, a threshold value ThA for toner bottle  70  and a threshold value Th 1  for sub hopper  72 . Threshold value ThA and threshold value Th 1  may be stored in a storage area such as a cache of control device  102  or in a storage device  120  which will be described later. 
     First detector  152  detects a remaining amount of toner in toner bottle  70 . A method of detecting the remaining amount of toner is arbitrary. For example, first detector  152  may mechanically detect a remaining amount of toner by making use of a sensor or may detect a remaining amount of toner with software by making use of a toner amount detection program. 
     In one aspect, first detector  152  detects a remaining amount of toner in toner bottle  70  by making use of a sensor for detecting an amount of toner such as a magnetic sensor. In another aspect, first detector  152  detects a remaining amount of toner in accordance with the number of dots in a toner attached region in an input image. More specifically, first detector  152  counts the number of dots in the toner attached region each time print processing is performed, and calculates an amount of consumed toner in accordance with the count value. First detector  152  calculates a remaining amount of toner in toner bottle  70  by subtracting the calculated amount of consumed toner from an amount of toner at the time when toner bottle  70  is filled up with toner. 
     Second detector  154  detects an empty space for toner in sub hopper  72 . A method of detecting the empty space is arbitrary. For example, second detector  154  may mechanically detect a remaining amount of toner by making use of a sensor or may detect a remaining amount of toner with software by making use of a toner amount detection program. 
     In one aspect, second detector  154  detects an empty space for toner in sub hopper  72  by making use of a sensor for detecting an amount of toner such as a magnetic sensor. More specifically, second detector  154  calculates an empty space for toner in sub hopper  72  by subtracting a remaining amount of toner in sub hopper  72  detected by the sensor from an amount of toner at the time when sub hopper  72  is filled up with toner. In another aspect, second detector  154  detects a remaining amount of toner in accordance with the number of dots in a toner attached region in an input image. More specifically, second detector  154  counts the number of dots in the toner attached region each time print processing is performed, and calculates an amount of consumed toner in accordance with the count value. The amount of consumed toner is initialized each time toner is supplied to sub hopper  72 . Second detector  154  detects an amount of consumed toner as an empty space for toner in sub hopper  72 . 
     Supply controller  160  has toner supplied from toner bottle  70  to sub hopper  72  each time the empty space for toner in sub hopper  72  exceeds threshold value ThA for toner bottle. When the remaining amount of toner in toner bottle  70  is smaller than threshold value ThA, threshold value Th 1  is lowered from the current value. Thus, when toner in toner bottle  70  is small in amount, a frequency of supply of toner to sub hopper  72  is increased. 
     First setting unit  170  accepts setting as to whether or not to activate change in threshold value Th 1  for sub hopper by supply controller  160 . The setting is accepted, for example, in a setting screen on image formation apparatus  100 . When change in threshold value Th 1  is set to active, change in threshold value Th 1  by supply controller  160  is permitted. When change in threshold value Th 1  is set to inactive, change in threshold value Th 1  by supply controller  160  is prohibited. 
     Second setting unit  172  accepts setting of at least one of threshold value ThA for toner bottle and threshold value Th 1  for sub hopper. The setting is accepted, for example, in a setting screen on image formation apparatus  100 . Namely, a user can arbitrarily input a value for threshold value ThA and threshold value ThA 1  in the setting screen. 
     Prohibition unit  180  prohibits print processing by image formation apparatus  100  when the remaining amount of toner in toner bottle  70  is smaller than threshold value ThA and when the empty space for toner in sub hopper  72  exceeds threshold value Th 1 . When the remaining amount of toner in sub hopper  72  and toner bottle  70  is small, prohibition unit  180  stops print processing. Thus, execution of the print processing in spite of absence of toner is prevented. 
     [Control of Representation on Image Formation Apparatus  100 ] 
     Control of representation on image formation apparatus  100  will be described with reference to  FIG. 7 .  FIG. 7  is a diagram showing one example of a manner of representation on image formation apparatus  100  in accordance with a remaining amount of toner in toner bottle  70  and sub hopper  72 . 
     A display  109  (see  FIG. 9 ) of image formation apparatus  100  changes contents of representation in accordance with a remaining amount of toner in toner bottle  70  and sub hopper  72 . 
     As shown with a state A in  FIG. 7 , display  109  shows nothing when a remaining amount of toner in toner bottle  70  is equal to or greater than threshold value ThA. When a sufficient amount of toner remains in toner bottle  70 , nothing is shown on display  109 . 
     As shown with a state B in  FIG. 7 , display  109  shows contents for having toner bottle  70  prepared when a remaining amount of toner in toner bottle  70  is smaller than threshold value ThA. In this case, for example, a message “prepare new toner bottle” is shown on display  109 . The user can thus prepare a new toner bottle before toner completely runs out. Contents for having toner bottle  70  prepared may be shown with an image instead of a message. 
     As shown with a state C in  FIG. 7 , display  109  shows contents for inviting replacement of toner bottle  70  when a remaining amount of toner in toner bottle  70  is smaller than a predetermined value smaller than threshold value ThA. The contents are shown when toner bottle  70  is empty. By way of example, the contents are shown when the remaining amount of toner being lower than the predetermined value is detected a plurality of times (for example, three times). For example, a message “time to replace toner bottle” is shown as representation contents on display  109 . The user can thus know appropriate timing of replacement of toner bottle  70 . Contents for having toner bottle  70  replaced may be shown with an image instead of a message. 
     As shown with a state D in  FIG. 7 , display  109  prohibits printing by image formation apparatus  100  and makes a degree of inviting replacement of toner bottle  70  higher than in state C when a remaining amount of toner in toner bottle  70  is smaller than the predetermined value smaller than threshold value ThA and when an empty space in sub hopper  72  exceeds threshold value Th 1  (see  FIG. 6 ). By way of example, when an amount of consumed toner after transition to state C exceeds a predetermined amount (for example, 10 g), image formation apparatus  100  determines that both of toner bottle  70  and sub hopper  72  are empty and transition from state C to state D is made. In this case, a message “replace toner bottle” is shown on display  109 . 
     [Control Structure of Image Formation Apparatus  100 ] 
     A control structure of image formation apparatus  100  will be described with reference to  FIG. 8 .  FIG. 8  is a flowchart showing a part of processing performed by image formation apparatus  100 . A process in  FIG. 8  is implemented by execution of a program by control device  102  of image formation apparatus  100 . In another aspect, a part or the entirety of the process may be performed by a circuit element or other hardware. 
     In step S 10 , control device  102  as supply controller  160  (see  FIG. 6 ) determines whether or not a remaining amount of toner in the toner bottle is larger than threshold value ThA (see  FIG. 1 ). When control device  102  determines that a remaining amount of toner in the toner bottle is larger than threshold value ThA (YES in step S 10 ), it switches control to step S 12 . Otherwise (NO in step S 10 ), control device  102  switches control to step S 20 . 
     In step S 12 , control device  102  sets a state of image formation apparatus  100  to a “normal state” (state A) (see  FIG. 7 ). 
     In step S 14 , control device  102  as supply controller  160  determines whether or not an empty space in the sub hopper exceeds threshold value Th 1  (see  FIG. 1 ). When control device  102  determines that an empty space in the sub hopper exceeds threshold value Th 1  (YES in step S 14 ), it switches control to step S 16 . Otherwise (NO in step S 14 ), control device  102  returns control to step S 10 . 
     In step S 16 , control device  102  as supply controller  160  has a predetermined amount (for example, 10 g) of toner supplied from the toner bottle to the sub hopper. Typically, toner in an amount corresponding to the empty space in the sub hopper is supplied so that the sub hopper is filled up. 
     In step S 20 , control device  102  as supply controller  160  lowers threshold value Th 1  for sub hopper in accordance with the remaining amount of toner in the toner bottle. By way of example, control device  102  lowers threshold value Th 1  as the remaining amount of toner in the toner bottle is smaller. 
     In step S 22 , control device  102  as supply controller  160  determines whether or not an empty space in the sub hopper exceeds threshold value Th 1 . When control device  102  determines that the empty space in the sub hopper exceeds threshold value Th 1  (YES in step S 22 ), it switches control to step S 24 . Otherwise (NO in step S 22 ), control device  102  returns control to step S 10 . 
     In step S 24 , control device  102  as supply controller  160  has a predetermined amount (for example, 5 g) of toner supplied from the toner bottle to the sub hopper. Typically, toner in an amount corresponding to the empty space in the sub hopper is supplied. An amount of supply of toner in step S 24  is smaller than an amount of supply of toner in step S 16 . 
     In step S 30 , control device  102  as supply controller  160  determines whether or not a remaining amount of toner in the toner bottle is smaller than a predetermined value smaller than threshold value ThA. Control device  102  determines whether or not the toner bottle is empty. When control device  102  determines that a remaining amount of toner in the toner bottle is smaller than the predetermined amount (YES in step S 30 ), it switches control to step S 40 . Otherwise (NO in step S 30 ), control device  102  switches control to step S 32 . 
     In step S 32 , control device  102  sets a state of image formation apparatus  100  to a “near empty state” (state B) (see  FIG. 7 ). Thereafter, control device  102  has display  109  (see  FIG. 9 ) of image formation apparatus  100  show contents for having a user prepare a new toner bottle. 
     In step S 40 , control device  102  as supply controller  160  determines whether or not an empty space in the sub hopper exceeds threshold value Th 1 . When control device  102  determines that an empty space in the sub hopper exceeds threshold value Th 1  (YES in step S 40 ), it switches control to step S 44 . Otherwise (NO in step S 40 ), control device  102  switches control to step S 42 . 
     In step S 42 , control device  102  sets a state of image formation apparatus  100  to an “empty state (printing permitted)” (state C) (see  FIG. 7 ). Thereafter, control device  102  has display  109  of image formation apparatus  100  show contents for replacement with a new toner bottle. 
     In step S 44 , control device  102  as prohibition unit  180  (see  FIG. 6 ) sets a state of image formation apparatus  100  to an “empty state (printing prohibited)” (state D) (see  FIG. 7 ). In state D, control device  102  does not accept a print instruction. Control device  102  has display  109  of image formation apparatus  100  show contents for replacement with a new toner bottle. 
     When a toner bottle is replaced, control device  102  returns threshold value Th 1  to a value before change and resumes the process from step S 10 . 
     [Hardware Configuration of Image Formation Apparatus  100 ] 
     One example of a hardware configuration of image formation apparatus  100  will be described with reference to  FIG. 9 .  FIG. 9  is a block diagram showing a main hardware configuration of image formation apparatus  100 . As shown in  FIG. 9 , image formation apparatus  100  includes a read only memory (ROM)  101 , control device  102 , a random access memory (RAM)  103 , a network interface  104 , a scanner  106 , a printer  107 , an operation panel  108 , a power supply  110 , and storage device  120 . 
     ROM  101  stores a control program executed in image formation apparatus  100 . Control device  102  is implemented, for example, by a CPU. Control device  102  controls operations of image formation apparatus  100  by executing various programs such as a program for controlling image formation apparatus  100 . RAM  103  functions as a working memory and temporarily stores various types of data necessary for execution of a control program. 
     An antenna or the like is connected to network interface  104  (a communication unit). Image formation apparatus  100  exchanges data with other communication equipment through the antenna. Other communication equipment includes, for example, a portable communication terminal such as a smartphone, a server  200  which will be described later (see  FIG. 11 ), and other image formation apparatuses. Image formation apparatus  100  may be configured to be able to download a control program  122  according to the present embodiment from server  200  through the antenna. 
     Scanner  106  optically reads a document set on image formation apparatus  100  and generates image data of the document. 
     Printer  107  is, for example, an apparatus for converting image data read by scanner  106  with electrophotography or print data transmitted from other communication equipment into data for printing and printing an image of a document based on resultant data. 
     Operation panel  108  is implemented as a touch panel (not shown) and accepts a touch operation onto image formation apparatus  100 . By way of example, operation panel  108  is configured with display  109  and a touch sensor provided as being layered on display  109 . Operation panel  108  accepts, for example, a setting operation in connection with control program  122  or a print instruction. 
     Power supply  110  supplies electric power to various devices in image formation apparatus  100  based on pressing of a power button (not shown) in image formation apparatus  100 . 
     Storage device  120  is, for example, a storage medium such as a hard disk or an external storage device. Storage device  120  stores control program  122  for implementing a process according to the present embodiment, threshold value ThA for toner bottle, and threshold value Th 1  for sub hopper by way of example. 
     Control program  122  according to the present embodiment may be provided not as a program alone but as being incorporated as a part of any program. In this case, the process according to the present embodiment is implemented in cooperation with any program. Even a program not including some modules as such does not depart from the gist of the program according to the present embodiment. Some or all of functions provided by control program  122  according to the present embodiment may be implemented by dedicated hardware. Image formation apparatus  100  may be configured in such a form as what is called a cloud service in which at least one server implements the process according to the present embodiment. 
     [Result of Comparison] 
     An advantage of image formation apparatus  100  according to the first embodiment will be described with reference to  FIG. 10 .  FIG. 10  is a diagram showing change in remaining amount of toner in the sub hopper in image formation apparatus  100  according to the first embodiment and an image formation apparatus  100 X according to a comparative example. 
     More specifically, a graph (A) shows transition of a remaining amount of toner in the toner bottle. A graph (B) shows timing of supply of toner from the toner bottle to the sub hopper. A graph (C) shows transition of a remaining amount of toner in the sub hopper. 
     As shown in graphs (A) to (C), when an amount of toner in the toner bottle is smaller than threshold value ThA, image formation apparatus  100  supplies toner from the toner bottle to the sub hopper each time an empty space in the sub hopper exceeds threshold value Th 1 . Image formation apparatus  100 X supplies toner from the toner bottle to the sub hopper each time the sub hopper is empty. Consequently, a frequency of supply of toner to the sub hopper in image formation apparatus  100  is higher than that in image formation apparatus  100 X. 
     Thus, when time to replace a toner bottle is near, image formation apparatus  100  frequently supplies toner from the toner bottle to the sub hopper. Thus, as shown in graph (A), a remaining amount of toner in the toner bottle in image formation apparatus  100  is always smaller than a remaining amount of toner in the toner bottle in image formation apparatus  100 X. As above, image formation apparatus  100  can achieve decrease in remaining toner by the time of replacement of the toner bottle. 
     Second Embodiment 
     [Overview] 
     Image formation apparatus  100  alone is described in the first embodiment. In a second embodiment, an image formation system  300  will be described.  FIG. 11  is a diagram showing one example of a system configuration of image formation system  300 . 
     As shown in  FIG. 11 , image formation system  300  includes image formation apparatuses  100 A to  100 C and server  200 . Image formation apparatuses  100 A to  100 C are connected to server  200  through a network  150 . Image formation apparatuses  100 A to  100 C communicate with server  200 , for example, through network interface  104  (see  FIG. 9 ). Image formation apparatuses  100 A to  100 C are also hereinafter collectively referred to as image formation apparatus  100 . 
     Image formation apparatus  100  transmits a request for ordering a new toner bottle (hereinafter also referred to as an “ordering request”) to server  200  when a remaining amount of toner in the toner bottle is smaller than threshold value ThA (see  FIG. 1 ). When toner in the toner bottle decreases, a new toner bottle is ordered. As a toner bottle is thus automatically ordered, a user can save efforts for ordering a toner bottle. 
     Ordering of a toner bottle means that time to replace a toner bottle is near. Therefore, image formation apparatus  100  lowers threshold value ThA for sub hopper (see  FIG. 1 ) from the current value based on transmission of the ordering request to server  200 . Image formation apparatus  100  can thus increase a frequency of supply of toner from the toner bottle to the sub hopper and decrease a remaining amount of toner by the time of replacement of a toner bottle. 
     [Processing for Ordering Toner Bottle] 
     A control structure of image formation system  300  will be described with reference to  FIG. 12 .  FIG. 12  is a flowchart showing processing for ordering a toner bottle by server  200 . A process in  FIG. 12  is implemented by execution of a program by a control device (for example, a CPU) of server  200 . In another aspect, a pan or the entirety of the process may be performed by a circuit element or other hardware. 
     In step S 50 , server  200  receives a request for ordering a toner bottle (that is, an ordering request) from image formation apparatus  100 A. 
     In step S 52 , server  200  determines whether or not there is another image formation apparatus which satisfies an ordering condition. The ordering condition is satisfied, for example, when a remaining amount of toner in the toner bottle is smaller than a prescribed amount. Server  200  searches for an image formation apparatus which satisfies the ordering condition among image formation apparatuses managed by image formation system  300 . When server  200  determines that there is another image formation apparatus which satisfies the ordering condition (YES in step S 52 ), it switches control to step S 56 . Otherwise (NO in step S 52 ), server  200  switches control to step S 54 . 
     Search for an image formation apparatus which satisfies the ordering condition in step S 52  can be carried out as follows. Server  200  can receive information on another image formation apparatus  100  in response to an ordering request from image formation apparatus  100 A and can conduct a search based on the received information. Server  200  may periodically receive information from each image formation apparatus  100  and conduct a search based on already received information on another image formation apparatus  100  in response to an ordering request from image formation apparatus  100 A. 
     In step S 54 , server  200  performs processing for ordering a toner bottle only for image formation apparatus  100 A. 
     In step S 56 , server  200  performs processing for ordering a toner bottle for image formation apparatus  100 A and processing for ordering a toner bottle for another image formation apparatus which satisfies the ordering condition. Thus, processing for ordering a toner bottle also for another image formation apparatus in addition to image formation apparatus  100 A can be performed. Consequently, a user of each image formation apparatus can save efforts for ordering a toner bottle. 
     In step S 60 , server  200  transmits an instruction to switch from a first supply mode to a second supply mode to an image formation apparatus for which the server has performed processing for ordering a toner bottle, and image formation apparatus  100  which has received the instruction switches to the second supply mode. The “first supply mode” here refers to an operation mode in which a frequency of supply of toner from the toner bottle to the sub hopper is not increased without changing threshold value Th 1  (see  FIG. 1 ) for sub hopper. The “second supply mode” refers to an operation mode in which a frequency of supply of toner from the toner bottle to the sub hopper is increased with threshold value Th 1  for sub hopper being made smaller than in a normal condition. 
     [Data Flow in Image Formation System  300 ] 
     A flow of data in image formation system  300  will be described with reference to  FIG. 13 .  FIG. 13  is a sequence diagram showing a flow of data between image formation apparatuses  100 A and  100  and server  200 . 
     Image formation apparatus  100 A can receive a command for having image formation apparatus  100  order a toner bottle (hereinafter also referred to as an “ordering command”) from another image formation apparatus  100 B or also from server  200 . By way of example, an ordering command is issued to another image formation apparatus when each image formation apparatus orders a toner bottle for itself to server  200 . In step S 102 , image formation apparatus  100 A receives an ordering command from image formation apparatus  100 B. 
     In step S 104 , image formation apparatus  100 A switches an operation mode from the first supply mode to the second supply mode based on reception of the ordering command from image formation apparatus  100 B. Image formation apparatus  100 A lowers threshold value ThA (see  FIG. 1 ) for sub hopper from the current value based on reception of the ordering command from image formation apparatus  100 B. A frequency of supply from the toner bottle to the sub hopper is thus increased. 
     In step S 106 , image formation apparatus  100 A transmits a request for ordering a toner bottle to server  200 . 
     Though an example in which image formation apparatus  100 A switches the operation mode from the first supply mode to the second supply mode based on an ordering command from image formation apparatus  100 B is described with reference to the example in  FIG. 13 , image formation apparatus  100  may switch the operation mode from the first supply mode to the second supply mode based on an ordering command from server  200 . 
     [Summary] 
     As set forth above, image formation apparatus  100  according to the second embodiment increases a frequency of supply of toner from the toner bottle to the sub hopper when it transmits a request for replacing a toner bottle to the server or when it receives a command to replace a toner bottle from another image formation apparatus. As a frequency of supply of toner is increased at the time of ordering of a toner bottle, a remaining amount of toner can be decreased by the time of replacement of a toner bottle. 
     Third Embodiment 
     [Overview] 
     Image formation apparatus  100  according to the first embodiment increases a frequency of supply of toner to the sub hopper when a remaining amount of toner in the toner bottle decreases. In contrast, image formation apparatus  100  according to a third embodiment estimates next timing of replacement of a toner bottle and increases a frequency of supply of toner from the toner bottle to the sub hopper as the estimated next timing of replacement is nearer. 
     [Functional Configuration of Image Formation Apparatus  100 ] 
     Processing for estimating timing to replace a toner bottle will be described with reference to  FIGS. 14 and 15 .  FIG. 14  is a diagram showing one example of a functional configuration of image formation apparatus  100  according to the third embodiment.  FIG. 15  is a diagram showing contents in a history  130  of replacement of a toner bottle. 
     As shown in  FIG. 14 , image formation apparatus  100  includes toner bottle  70 , sub hopper  72 , development apparatus  75 , and control device  102 . Control device  102  is implemented, for example, by a CPU. Control device  102  includes, as a functional configuration, first detector  152 , second detector  154 , supply controller  160 , first setting unit  170 , second setting unit  172 , prohibition unit  180 , and an estimation unit  182 . Control device  102  stores as data, threshold value ThA for toner bottle, threshold value Th 1  for sub hopper, and replacement history  130 . Since the configuration other than estimation unit  182  and replacement history  130  are as described with reference to  FIG. 6 , description of the configuration will not be repeated. 
     Estimation unit  182  estimates next timing to replace a toner bottle based on replacement history  130 .  FIG. 15  shows contents in replacement history  130 . By way of example, timing to replace a toner bottle (for example, date or time) is written in replacement history  130  for each type of toner bottle. Image formation apparatus  100  writes a type of a toner bottle and timing of replacement of the toner bottle in replacement history  130  based on replacement of the toner bottle. Replacement history  130  may be stored in a storage area such as a cache of control device  102  or in storage device  120  (see  FIG. 9 ). 
     Estimation unit  182  estimates next timing of replacement of a toner bottle based on periodicity of timing of replacement of a toner bottle defined in replacement history  130 . For example, estimation unit  182  calculates an interval between timings of replacement by referring to replacement history  130 , averages the intervals between the timings of replacement for each type of the toner bottle, and calculates a period of replacement of each toner bottle. Estimation unit  182  determines a result of addition of a period of replacement of each toner bottle to previous timing of replacement of each toner bottle as estimated next timing of replacement of each toner bottle. Estimation unit  182  determines earliest timing among next timings of replacement of each toner bottle as estimated next timing of replacement. 
     Supply controller  160  lowers threshold value Th 1  for sub hopper as the current time is closer to estimated next timing of replacement. 
     [Summary] 
     As set forth above, image formation apparatus  100  according to the present embodiment increases a frequency of supply of toner to the sub hopper as the current time is closer to estimated next timing of replacement. Thus, image formation apparatus  100  can further decrease a remaining amount of toner by the time of replacement of a toner bottle. 
     Though the embodiments of the present invention have been described, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.