Patent Publication Number: US-2019179577-A1

Title: Image forming apparatus, method for controlling image forming apparatus, and computer readable recording mideum

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The entire disclosure of Japanese Patent Application No. 2017-236067, filed on Dec. 8, 2017, is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technological Field 
     The present invention relates to an image forming apparatus, a method for controlling an image forming apparatus, and a computer-readable recording medium. 
     2. Description of the Related Art 
     There has been known an image forming apparatus that is capable of storing, in a memory, a print job output in the past, and re-outputting the print job. For example, such an image forming apparatus displays a list of all print jobs stored in a memory on an operation display, and re-outputs a print job selected by a user. See Japanese Patent Publication No. 2015-101016. 
     SUMMARY 
     However, in the technique described above, when a large number of print jobs are included in a job list stored in the memory, information of a large number of print jobs are also displayed on the operation display. In such a case, the user needs to look for a print job to be re-output among an enormous number of candidates, which has resulted in a problem of poor operability of the user. 
     The present invention is made in view of the above circumstances. Therefore, an object of the present invention is to provide an image forming apparatus, a method for controlling an image forming apparatus, and a computer-readable recording medium that improve operability of a user selecting a print job from a job list. 
     To achieve at least one of the abovementioned objects, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention, comprises: a paper feeding tray that contains paper; and a hardware processor that obtains tray paper information that is information of paper set on the paper feeding tray, obtains job paper information from a memory that stores a job list including a plurality of print jobs associated with the job paper information that is information of paper used at the time of output of the print jobs, and narrows down the print jobs in the job list to at least one print job for re-output based on the obtained tray paper information and job paper information. 
     To achieve at least one of the abovementioned objects, according to an aspect of the present invention, a method for controlling an image forming apparatus reflecting one aspect of the present invention and comprising a paper feeding tray that contains paper, comprises: (a) obtaining tray paper information that is information of paper set on the paper feeding tray; (b) obtaining job paper information from a memory that stores a job list including a plurality of print jobs associated with the job paper information that is information of paper used at the time of output of the print jobs; and (c) narrowing down the print jobs in the job list to at least one print job for re-output based on the tray paper information obtained in the step (a) and the job paper information obtained in the step (b). 
     To achieve at least one of the abovementioned objects, according to an aspect of the present invention, a non-transitory computer-readable recording medium reflecting one aspect of the present invention stores a program that causes a computer to execute the abovementioned method. 
     The objects, features, and characteristics of this invention other than those set forth above will become apparent from the description given herein below with reference to preferred embodiments illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention. 
         FIG. 1  is a diagram showing a schematic configuration of an image forming apparatus according to a first embodiment; 
         FIG. 2  is a block diagram showing a functional configuration of a processor; 
         FIG. 3  is a diagram for explaining a relationship between a paper feeding tray and tray paper information; 
         FIG. 4  is a diagram showing an example of an operation screen for inputting tray paper information; 
         FIG. 5  is a diagram for explaining a relationship between a print job and job paper information; 
         FIG. 6  is a flowchart showing a procedure of processing of the image forming apparatus; 
         FIG. 7  is a subroutine flowchart showing a procedure of job narrowing processing of step S 105  of  FIG. 6 ; 
         FIG. 8  is a diagram showing an example of an operation screen for setting a job narrowing condition; 
         FIG. 9  is a diagram showing an example of a narrowing result table; 
         FIG. 10  is a subroutine flowchart showing a procedure of job displaying processing of step S 106  of  FIG. 6 ; 
         FIG. 11  is a diagram showing an example of an operation screen for displaying a job narrowing result; 
         FIG. 12  is a diagram showing a schematic configuration of an image forming apparatus according to a second embodiment; 
         FIG. 13  is a diagram showing another example of the operation screen for setting the job narrowing condition; 
         FIG. 14  is a diagram showing another example of the narrowing result table; 
         FIG. 15  is a diagram showing another example of the operation screen for displaying the job narrowing result; 
         FIG. 16  is a diagram for explaining a relationship between a print job and a plurality of pieces of the job paper information; 
         FIG. 17  is a flowchart showing a procedure of processing of an image forming apparatus according to a third embodiment; and 
         FIG. 18  is a diagram showing still another example of the operation screen for displaying the job narrowing result. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. 
     In description of the drawings, the same reference signs are attached to the same elements to avoid duplicate description. Ratios of dimensions in the drawings may be exaggerated for convenience of explanation, and different from actual ratios. 
     First Embodiment 
     First, a configuration of an image forming apparatus according to a first embodiment will be described. 
       FIG. 1  is a diagram showing a schematic configuration of the image forming apparatus according to the first embodiment. 
     As shown in  FIG. 1 , the image forming apparatus  1  includes a processor  10 , a memory  20 , a communicator  30 , an operation display  40 , a paper feeder  50 , a conveyor  60 , an image former  70 , and a fixer  80 . 
     The processor  10  includes a CPU (central processing unit), and executes control of the each of elements described above and a variety of arithmetic processing in accordance with programs. A functional configuration of the processor  10  will be described later. 
     The memory  20  includes a ROM (read only memory) that stores a variety of programs and a variety of pieces of data in advance, a RAM (random access memory) that serves as a working area that temporarily stores programs and data, and a hard disk that stores a variety of programs and a variety of pieces of data, or the like. 
     In the present embodiment, the memory  20  stores a job list including a plurality of print jobs output in the past. However, a memory that stores the job list is not limited to the memory  20  that is locally included in the image forming apparatus  1 . For example, an external memory included in another apparatus, such as an optional server or another image forming apparatus connected by a network, may be used as the memory. Hereinafter, the memory  20  or the external memory will be collectively referred to as the “memory  20  or the like” or simply the “memory”. Each print job is associated with information of paper (hereinafter also referred to as the “job paper information”) used at the time of output of the print job. A print job is associated with the job paper information and added to the job list every time the print job is output by the image forming apparatus  1 . 
     The communicator  30  is an interface for communicating with other devices, such as a PC (personal computer) of a user, via networks, such as LAN (local area network). For example, the communicator  30  receives a print job from the PC of the user, and transmits information of an operation screen to be displayed on the PC of the user. 
     The operation display  40  includes a touch panel, a ten-key pad, a start button, a stop button and the like, displays a variety of pieces of information on an operation screen, and receives a variety of operations. 
     The paper feeder  50  includes a plurality of paper feeding trays  51  that contain paper to be used for printing, and a plurality of paper feeding rollers  52  that feed paper by separating each piece of paper from the other pieces contained in the paper feeding tray  51 . 
     The conveyor  60  includes a conveying path, a plurality of conveying roller pairs arranged along the conveying path, and a drive motor (not shown) that drives the conveying roller pair. The conveyor  60  carries paper fed by the paper feeder  50  to the image former  70  and the fixer  80 . 
     The image former  70  forms an image on paper based on image data included in a print job by using a well-known imaging process, such as an electrophotographic processes, including each process of charging, exposure, development, and transfer. 
     The fixer  80  includes a pressure roller and a heating roller. The fixer  80  heat-fixes an image by pressing and heating paper on which an image is formed by the image former  70 . 
     The image forming apparatus  1  may include elements other than the elements described above, or does not need to include some of the elements described above. 
     Next, a functional configuration of the processor  10  will be described. 
       FIG. 2  is a block diagram showing a functional configuration of the processor. 
     As shown in  FIG. 2 , the processor  10  functions as a display controller  11 , an operation receiver  12 , a memory controller  13 , a tray information obtainer  14 , a job information obtainer  15 , a narrowing unit  16 , and an output controller  17 , by reading programs and executing processing. 
     The display controller  11  causes the operation display  40  or a display of another device (for example, a PC connected to the image forming apparatus  1 ) (hereinafter collectively referred to as the “operation display  40  or the like”), to display a predetermined operation screen. 
     The operation receiver  12  receives operation input by a user on the operation display  40  or an operation unit of another device (for example, a PC connected to the image forming apparatus  1 ) (hereinafter collectively referred to as the “operation display  40  or the like”). 
     The memory controller  13  causes the memory  20  or the like to store a variety of pieces of information, and reads a variety of pieces of information from the memory  20  or the like. For example, the memory controller  13  causes the memory  20  or the like to store a print job associated with job paper information. 
     The tray information obtainer  14  obtains information relating to the paper feeding tray  51 . For example, the tray information obtainer  14  obtains information showing that paper is set on the paper feeding tray  51 , and information of paper set on the paper feeding tray  51  (hereinafter also referred to as the “tray paper information”). The tray paper information obtained by the tray information obtainer  14  is associated with each of the paper feeding trays  51 , and is stored in the memory  20  functioning as a tray information memory. The tray paper information will be described later in detail. 
     The job information obtainer  15  obtains information relating to a print job. For example, the job information obtainer  15  obtains information relating to a print job that is output in the past and stored in the memory  20  or the like from the memory  20  or the like. The job paper information will be described later in detail. 
     The narrowing unit  16  narrows down print jobs in the job list stored in the memory  20  or the like to at least one print job, that is, narrows down at least one print job from the job list stored in the memory  20  or the like, based on the tray paper information obtained by the tray information obtainer  14  and the job paper information obtained by the job information obtainer  15 . 
     The output controller  17  causes the paper feeder  50 , the conveyor  60 , the image former  70 , the fixer  80 , and the like (hereinafter also collectively referred to as the “output unit”) to output a print job. 
     Next, the tray paper information and the job paper information will be described in detail. 
       FIG. 3  is a diagram for explaining a relationship between the paper feeding tray and the tray paper information.  FIG. 4  is a diagram showing an example of an operation screen for inputting the tray paper information. 
     As shown in  FIG. 3 , each piece of the tray paper information is stored in association with each of the paper feeding trays  51 . Each piece of the tray paper information includes, for example, information relating to a plurality of attributes of paper, such as a size, a type, and a basis weight of paper. For example, types of paper include, without limitation to, plain paper, fine quality paper, and coated paper, and colored paper of them. 
     The image forming apparatus  1  displays an operation screen as exemplified in  FIG. 4 , for prompting the user to input the tray paper information before or after paper is set on the paper feeding tray  51 . The image forming apparatus  1  then receives the tray paper information input by the user on the operation screen. For example, the tray paper information is confirmed when a soft key of “OK” is pressed, and is returned to a state immediately before when a “Cancel” key is pressed. The tray paper information input once may be stored in the memory  20  when a “Register setting” key is pressed, and may be read out from the memory  20  and re-entered when a “Call setting” key is pressed later. 
     When there is the tray paper information that can be automatically detected, the image forming apparatus  1  does not need to prompt the user to input the tray paper information. For example, the image forming apparatus  1  does not need to prompt the user to input a size of paper when the size of paper is a standard size that can be automatically detected, and may prompt the user to input the size of paper only when the size of paper is not the standard size. The image forming apparatus  1  may also display the tray paper information automatically detected, and prompt the user to make a correction as needed. 
       FIG. 5  is a diagram for explaining a relationship between a print job and the job paper information. 
     As shown in  FIG. 5 , each piece of the job paper information is stored in association with each print job output in the past. The tray paper information associated with the paper feeding tray  51  from which paper used for a print job output in the past is fed is stored as the job paper information. For this reason, each piece of the job paper information includes, for example, information relating to a plurality of attributes of paper corresponding to the tray paper information, such as a size, a type, and a basis weight of paper. 
     Next, a procedure of processing performed at the time of re-output of a print job of the image forming apparatus  1  according to the present embodiment will be described. Processing of the image forming apparatus  1  is processing for controlling to improve operability of a user selecting a print job from a job list stored in the memory  20  or the like. 
       FIG. 6  is a flowchart showing a procedure of processing of the image forming apparatus. An algorithm shown in the flowchart of  FIG. 6  is stored as a program in the memory  20  of the image forming apparatus  1 , and is executed by the processor  10 . 
     As shown in  FIG. 6 , the processor  10  first determines whether or not a job narrowing function, which is a function for narrowing down print jobs, is enabled (step S 101 ). Before step S 101 , the processor  10  may function as the display controller  11  to cause the operation display  40  or the like to display an operation screen for prompting the user to set enabling or disabling of the job narrowing function, and may function as the operation receiver  12  to receive setting made by the user on the operation screen in advance. Alternatively, initial setting of enabling or disabling of the job narrowing function may be stored in the memory  20 , and the processor  10  may function as the memory controller  13  to read out the initial setting. 
     When the job narrowing function is not enabled (step S 101 : NO), that is, when the job narrowing function is disabled, the processor  10  ends the processing. 
     When the job narrowing function is enabled (step S 101 : YES), the processor  10  determines whether or not paper is set on the paper feeding tray  51 , that is, the paper feeding tray  51  containing paper is mounted on (inserted into) a main body of the image forming apparatus  1  (step S 102 ). 
     When paper is not set on the paper feeding tray  51  (step S 102 : NO), the processor  10  waits until paper is set on the paper feeding tray  51 . 
     When paper is set on the paper feeding tray  51  (step S 102 : YES), the processor  10  functions as the tray information obtainer  14  to obtain the tray paper information (step S 103 ). More specifically, the processor  10  functions as the display controller  11  to cause the operation display  40  or the like to display an operation screen as exemplified in  FIG. 4 , for inputting the tray paper information, and functions as the operation receiver  12  to receive the tray paper information input by the user on the operation screen. The processor  10  then functions as the memory controller  13  to cause the memory  20  to store the received tray paper information, and functions as the tray information obtainer  14  to obtain the information. When displaying the operation screen after paper is set on the paper feeding tray  51 , the processor  10  waits until input by the user is completed and the tray paper information can be obtained. 
     Next, the processor  10  functions as the job information obtainer  15  to obtain the job paper information associated with print jobs output in the past from the memory  20  or the like (step S 104 ). The processor  10  then proceeds to job narrowing processing of step S 105 . The job narrowing processing is processing for narrowing down print jobs in the job list stored in the memory  20  or the like to at least one print job based on the tray paper information obtained in step S 103  and the job paper information obtained in step S 104 . Step S 105  will be described later in detail. 
     Next, the processor  10  proceeds to job displaying processing of step S 106 . The job displaying processing is processing for displaying print jobs narrowed down (obtained by narrowing down) in the job list in step S 105 , to the user. Step S 106  will be described later in detail. 
     Next, the processor  10  determines whether or not there is an instruction for outputting a print job in step S 106  (step S 107 ). 
     When there is no instruction for outputting (step S 107 : NO), the processor  10  ends the processing. 
     When there is an instruction for outputting (step S 107 : YES), the processor  10  functions as the output controller  17  to cause the output unit to output (re-output) a selected print job (step S 108 ). 
     Finally, the processor  10  functions as the memory controller  13  to cause the memory  20  or the like to store a new piece of the job paper information, which is information of paper used at the time of re-output of a print job, in association with the re-output print job (step S 109 ), and ends the processing. Since the image forming apparatus  1  can re-output a print job associated with the job paper information not completely matching with the tray paper information, the job paper information at the time of re-output may be different from the job paper information before the re-output. The processor  10  may cause the memory  20  or the like to store the job paper information at the time of re-output in place of the job paper information before the re-output (for example, by overwriting), or together with the original job paper information. 
     Next, the job narrowing processing of step S 105  will be described in detail. 
       FIG. 7  is a subroutine flowchart showing a procedure of the job narrowing processing of step S 105  of  FIG. 6 .  FIG. 8  is a diagram showing an example of an operation screen for setting a job narrowing condition.  FIG. 9  is a diagram showing an example of a narrowing result table. The job narrowing processing of  FIG. 7  is executed simultaneously or sequentially for all print jobs included in the job list stored in the memory  20  or the like. 
     As shown in  FIG. 7 , the processor  10  first determines whether or not determination of the size of paper is enabled based on a job narrowing condition (step S 201 ). The “job narrowing condition” is a condition showing attributes of paper to be determined in order to narrow down print jobs. 
     Before step S 201 , the processor  10  functions as the display controller  11  to cause the operation display  40  or the like to display an operation screen as exemplified in  FIG. 8 , for prompting the user to set the job narrowing condition. The processor  10  then functions as the operation receiver  12  to receive setting made by the user on the operation screen in advance. For example, soft keys for switching between enabling and disabling of determination are displayed in a section A when the user selects a section of “Determination enable/disable” of each attribute of paper on the operation screen. Then, for example, setting of “Enable” or “Disable” is confirmed when an “OK” key is pressed in a state where an “Enable” or “Disable” key is selected, and is returned to a state immediately before when a “Cancel” key is pressed. Initial setting of the job narrowing condition may be stored in the memory  20  or the like. 
     The description will be made on  FIG. 7  again. When the determination of the size of paper is enabled (step S 201 : YES), the processor  10  functions as the narrowing unit  16  to determine whether or not the size of paper included in the tray paper information matches with the size of paper included in the job paper information (step S 202 ). 
     When the sizes of paper match with each other (step S 202 : YES), the processor  10  functions as the memory controller  13  to cause the memory  20  to store information indicating that the sizes of paper match with each other (step S 203 ). The processor  10  then proceeds to processing of step S 204 . 
     When the determination of the size of paper is disabled (step S 201 : NO), or the sizes of paper do not match with each other (step S 202 : NO), the processor  10  proceeds to processing of step S 204  directly. 
     Next, the processor  10  executes processing of steps S 204  to S 206  for the type of paper, and processing of steps S 207  to S 209  for the basis weight of paper. Procedures of processing of steps S 204  to S 206  and steps S 207  to S 209  are substantially the same as those of steps S 201  to S 203 , and will be omitted from description. 
     Finally, the processor  10  functions as the memory controller  13  to cause the memory  20  to store names of print jobs associated with the job paper information including attributes of paper, at least part of which matches with attributes of paper included in the tray paper information (step S 210 ). That is, the processor  10  causes a narrowing result table T 1  as exemplified in  FIG. 9 , to store names (identifiers) of print jobs narrowed down based on the job narrowing condition, among print jobs included in the job list. The processor  10  also reflects a result stored in the memory  20  in steps S 203 , S 206 , and S 209  to the narrowing result table T 1 . In the narrowing result table T 1 , “OK” signifies that attributes of paper included in the tray paper information and the job paper information match with each other, “NG” signifies that such attributes do not match with each other, and “−” signifies that determination of attributes of paper is disabled. 
     The processor  10  may cause the narrowing result table T 1  to store names of print jobs only when at least sizes of paper included in the tray paper information and the job paper information match with each other. This is because a possibility is extremely low that a print job associated with the size of paper that does not match with the size of paper set on the paper feeding tray  51  is re-output by the user. 
     Next, the job displaying processing of step S 106  will be described in detail. 
       FIG. 10  is a subroutine flowchart showing a procedure of the job displaying processing of step S 106  of  FIG. 6 .  FIG. 11  is a diagram showing an example of an operation screen for displaying a job narrowing result. 
     As shown in  FIG. 10 , the processor  10  first functions as the display controller  11  to cause the operation display  40  or the like to display the tray paper information that is obtained in step S 103  and subject to comparison in the job narrowing processing of step S 105  (step S 301 ). The processor  10  then functions as the memory controller  13  to obtain the narrowing result table T 1  in which names of print jobs and the like are stored in step S 210  (step S 302 ). Further, the processor  10  functions as the display controller  11  to cause the operation display  40  or the like to display an operation screen on which print jobs are rearranged based on a job rearrangement condition (step S 303 ). The “job rearrangement condition” is a condition for rearranging print jobs so that, for example, priority is placed on the print jobs stored in association with the job paper information that matches with the tray paper information with a high degree of coincidence. Alternatively, the “job rearrangement condition” may be a condition for rearranging print jobs in accordance with other conditions, such as date and time of output. 
     The processor  10  causes the operation display  40  or the like to display an operation screen as exemplified in  FIG. 11 , for displaying the job narrowing result to the user. The operation screen of  FIG. 11  displays the tray paper information obtained in step S 103  and information of narrowed-down print jobs, and the order of print jobs is rearranged as compared with that in the narrowing result table T 1  of  FIG. 9 . This shows a result of the processor  10  rearranging print jobs so that priority is placed on the print jobs that are stored in association with the job paper information that matches with the tray paper information with a high degree of coincidence. When there are a plurality of print jobs associated with the job paper information that matches with the tray paper information with an equivalent degree of coincidence, like Job  4  and Job  12 , the image forming apparatus  1  may further rearrange the print jobs in order of date and time of output. 
     The description will be made on  FIG. 10  again. The processor  10  determines whether or not there is an instruction for canceling current processing (step S 304 ). For example, the processor  10  functions as the operation receiver  12  to determine whether or not a soft key of “Cancel” for ending current processing is pressed on an operation screen, such as one shown in  FIG. 11 . 
     When there is an instruction for canceling (step S 304 : YES), the processor  10  returns to the processing of  FIG. 6 . 
     When there is no instruction for canceling (step S 304 : NO), the processor  10  determines whether or not at least one print job is selected (step S 305 ). For example, the processor  10  functions as the operation receiver  12  to determine whether or not a section of “Job name” of each print job is selected on the operation screen, such as one shown in  FIG. 11 . 
     When no print job is selected (step S 305 : NO), the processor  10  repeats the processing of step S 304  and S 305  until there is an instruction for canceling or at least one print job is selected. 
     When at least one print job is selected (step S 305 : YES), the processor  10  determines whether or not there is an instruction for outputting a print job (step S 306 ). For example, the processor  10  functions as the operation receiver  12  to determine whether or not a soft key of “Output” for outputting a selected print job is pressed on the operation screen, such as one shown in  FIG. 11 . 
     When there is an instruction for outputting (step S 306 : YES), the processor  10  returns to the processing of  FIG. 6 . 
     When there is no instruction for outputting (step S 306 : NO), the processor  10  repeats the processing of step S 304  to S 306  until there is an instruction for canceling or an instruction for outputting. 
     When a predetermined timeout period elapses without no instruction for canceling or no instruction for outputting, the processor  10  may deem that there is an instruction for canceling and return to the processing of  FIG. 6 . 
     As described above, the image forming apparatus  1  narrows down print jobs in the job list to at least one print job based on the tray paper information, which is information of paper set on the paper feeding tray  51 , and the job paper information, which is information of paper used at the time of output of print jobs. Accordingly, the image forming apparatus  1  can narrow down print jobs in the job list only to print jobs that can be re-output by using paper contained in the paper feeding tray  51 , even when a large number of print jobs are stored in the memory  20  or the like. In this manner, the image forming apparatus  1  can improve operability of the user selecting a print job from the job list. 
     The image forming apparatus  1  also obtains the tray paper information input by the user on the operation screen. In this manner, the image forming apparatus  1  can obtain the tray paper information without the need of a special configuration. 
     The image forming apparatus  1  also narrows down print jobs in the job list at a timing at which paper is set on the paper feeding tray  51 . In this manner, the image forming apparatus  1  can automatically execute the job narrowing processing without waiting for a special operation performed by the user, which results in further improvement in operability of the user selecting a print job from the job list. 
     The image forming apparatus  1  also narrows down print jobs in the job list based on the job narrowing condition. In this manner, the image forming apparatus  1  can effectively execute the job narrowing processing based on the job narrowing condition. 
     The job narrowing condition is set by the user. In this manner, the image forming apparatus  1  can effectively execute the job narrowing processing based on requests from the user. 
     The image forming apparatus  1  also narrows down print jobs in the job list based on whether or not attributes of paper to be determined included in the tray paper information and the job paper information match with each other. In this manner, the image forming apparatus  1  can narrow down print jobs in the job list only to print jobs associated with the job paper information at least part of which matches with the tray paper information. 
     The image forming apparatus  1  also rearranges print jobs based on the job rearrangement condition when there is a plurality of narrowed-down print jobs. In this manner, the image forming apparatus  1  can display print jobs which are rearranged in the order preferable to the user, which results in further improvement in operability of the user selecting a print job from the job list. 
     The job rearrangement condition is a condition for rearranging print jobs so that priority is placed on the print jobs stored in association with the job paper information that matches with the tray paper information with a high degree of coincidence. In this manner, the image forming apparatus  1  can display print jobs so that priority is placed on the print jobs which have a high possibility of being re-output by the user. The image forming apparatus  1  can also display print jobs stored in association with the job paper information that does not completely, but partly, match with the tray paper information by placing a lower degree of priority. 
     The image forming apparatus  1  also adds a print job that is associated with the job paper information to the job list every time the print job is output. In this manner, the image forming apparatus  1  can make all print jobs which have been output before, subject to re-output. In addition, the image forming apparatus  1  can cause, not only in the memory  20  of the own apparatus, but also in a memory of other apparatuses, such as a server, to store print jobs. Accordingly, the image forming apparatus  1  can share the job paper information with other image forming apparatuses, which results in improvement in operability of the user using a plurality of image forming apparatuses. 
     When re-outputting a print job, the image forming apparatus  1  also stores the job paper information at the time of the re-output in association with the re-output print job on the memory  20  or the like. In this manner, the image forming apparatus  1  can execute the subsequent job narrowing processing based on the job paper information at the time of re-output. 
     In the above embodiment, an example of the processing of the image forming apparatus  1  is described. However, the present embodiment is not limited to the above example. Various modifications, improvements or the like, such as those described below, can be made. 
     The image forming apparatus  1  narrows down print jobs in the job list at a timing at which paper is set on the paper feeding tray  51  in step S 102  of  FIG. 6 . However, the present embodiment is not limited to the above example. The image forming apparatus  1  may execute the job narrowing processing at other timings. 
     As described above, the image forming apparatus  1  stores the obtained tray paper information in association with the paper feeding tray  51 . For this reason, the image forming apparatus  1  does not require the user to re-enter the tray paper information even when executing the job narrowing processing at a timing different from the timing at which paper is set on the paper feeding tray  51 . 
     For example, the image forming apparatus  1  may narrow down print jobs in the job list at a timing at which the paper feeding tray  51  is selected on an operation screen displayed on the operation display  40  or the like. For example, the image forming apparatus  1  displays, on the operation display  40  or the like, an operation screen for prompting the user to select the paper feeding tray  51  containing paper to be used. The image forming apparatus  1  then determines whether or not the paper feeding tray  51  is selected by the user on the operation screen in place of performing the processing of step S 102 . When the paper feeding tray  51  is selected, the image forming apparatus  1  executes the processing of steps S 103  to S 109 . In this manner, every time a different one of the paper feeding tray  51  is selected on the operation screen for selecting the paper feeding tray  51 , the image forming apparatus  1  can present to the user print jobs that can be re-output by using paper contained in the selected paper feeding tray  51 , which results in further improvement in operability of the user. 
     Alternatively, the image forming apparatus  1  may narrow down print jobs in the job list at a timing at which an operation screen for prompting the user to select a print job to be re-output is displayed. The operation screen may be, for example, an operation screen that is displayed when a “Job list” tab is selected on an operation screen, such as one shown in  FIG. 4 . The image forming apparatus  1  determines whether or not the “Job list” tab is selected. When the “Job list” tab is selected, the image forming apparatus  1  executes the processing of steps S 103  to S 109 . The image forming apparatus  1  may further display an operation screen for prompting the user to select the paper feeding tray  51 , for which the job narrowing processing is to be performed, before or after displaying the operation screen for selecting a print job. As described above, the image forming apparatus  1  can execute the job narrowing processing at various timings. 
     The image forming apparatus  1  determines whether or not types of paper included in the tray paper information and the job paper information match with each other in step S 205  of  FIG. 7 . The image forming apparatus  1  may determine that the types of paper included in the tray paper information and the job paper information match with each other even when the types of paper do not completely match with each other and partly match with each other. 
     As described above, types of paper include, for example, plain paper, fine quality paper, and coated paper, and colored paper of them. Accordingly, for example, when a type of paper included in the tray paper information is “white plain paper” and a type of paper included in the job paper information is “white fine quality paper”, colors of paper match with each other while materials of paper do not match with each other. In this case, in step S 205 , the image forming apparatus  1  may determine that the types of paper match with each other in order to obtain as many narrowed-down print jobs as possible, or may determine that the types of paper do not match with each other in order to narrow down print jobs as accurately as possible. Alternatively, in the job narrowing processing, the image forming apparatus  1  may determine a color and a material of paper separately as different attributes of paper instead of determining a color and a material of paper collectively as one attribute, which is the type, of paper. 
     The image forming apparatus  1  determines whether or not basis weights of paper included in the tray paper information and the job paper information match with each other in step S 208  of  FIG. 7 . However, the present embodiment is not limited to the above example. The image forming apparatus  1  may determine that the basis weights of paper included in the tray paper information and the job paper information match with each other even when the basis weights of paper do not completely match with each other, as long as a difference between the basis weights is a predetermined threshold value for determination or smaller. The predetermined threshold value for determination may be settable by the user on an operation screen, such as one shown in  FIG. 8 . 
     Second Embodiment 
     In the description of the first embodiment, the image forming apparatus  1  obtains the tray paper information input by the user. In a second embodiment, the image forming apparatus  1  obtains the tray paper information by another method. 
       FIG. 12  is a diagram showing a schematic configuration of an image forming apparatus according to the second embodiment. 
     As shown in  FIG. 12 , the image forming apparatus  1  according to the second embodiment has a configuration substantially the same as the image forming apparatus  1  according to the first embodiment, except a sensor  53 . 
     For example, the sensor  53  is provided above the paper feeding tray  51 , and detects information of paper set on the paper feeding tray  51  (tray paper information). The tray paper information according to the second embodiment may include information that is different from the tray paper information according to the first embodiment. The tray paper information according to the second embodiment includes, for example, information relating to a plurality of attributes of paper, such as a size, a thickness, a surface smoothness, and a glossiness of paper. 
     The sensor  53  may be configured with a plurality of types of sensors. For example, the sensor  53  may be configured with a plurality of types of sensors dedicated for detecting a size, a thickness, a surface smoothness, a glossiness, and the like of paper respectively. Alternatively, the sensor  53  may include, for example, an optical sensor or the like that can measure both a surface smoothness and a glossiness of paper. When a size of paper is a standard size that is automatically detectable, the image forming apparatus  1  does not need to cause the sensor  53  to detect the size of paper. 
     Before the sensor  53  detects a thickness of paper, the paper feeding roller  52  may move a position of a top piece of paper contained in the paper feeding tray  51 , and after the sensor  53  detects the thickness of the piece of paper, the paper feeding roller  52  may return the piece of paper to an original position. Alternatively, a sensor that detects the thickness of paper in the sensor  53  may be provided on the conveying path of the conveyor  60  to detect the thickness of paper carried by the conveyor  60 . 
     Next, a procedure of processing of the image forming apparatus  1  according to the second embodiment will be described. Hereinafter, only processing different from the processing of the image forming apparatus  1  according to the first embodiment will be described. 
     In the second embodiment, in step S 103  of  FIG. 6 , the image forming apparatus  1  obtains the tray paper information detected by the sensor  53  instead of the tray paper information input by the user. In addition, the image forming apparatus  1  displays an operation screen different from one in the first embodiment on the operation display  40  or the like before step S 201  of  FIG. 7 . 
       FIG. 13  is a diagram showing another example of the operation screen for setting the job narrowing condition. 
     For example, the image forming apparatus  1  may also receive input of a “Determination threshold value (threshold value for determination)” in addition to selection of the “Determination enable/disable” made by the user on an operation screen as exemplified in  FIG. 13 , for prompting the user to set the job narrowing condition. For example, when a threshold value for determination for each attribute of paper is input, the image forming apparatus  1  displays a soft key in a section B. For example, the threshold value for determination is confirmed when an “OK” key is pressed, and is returned to a state immediately before when a “Cancel” key is pressed. That is, the “job narrowing condition” in the second embodiment can be considered as a condition showing attributes of paper to be determined in order to narrow down print jobs, and a condition relating to the threshold value for determination. An initial value of the threshold value for determination may be stored in the memory  20  or the like. 
     In the job narrowing processing of  FIG. 7 , the image forming apparatus  1  makes determination relating to the tray paper information according to the second embodiment, such as a size, a thickness, a surface smoothness, a glossiness of paper, instead of the tray paper information according to the first embodiment, such as a size, a type, a basis weight of paper. When the threshold value for determination is input, the image forming apparatus  1  may determine that attributes of paper included in the tray paper information and the job paper information match with each other even when numerical values showing the attributes of paper do not completely match with each other, as long as a difference between the numerical values is a threshold value for determination or smaller. In addition, in the job displaying processing of  FIG. 10 , the image forming apparatus  1  displays the tray paper information according to the second embodiment, such as a size, a thickness, a surface smoothness, a glossiness of paper, instead of the tray paper information according to the first embodiment, such as a size, a type, a basis weight of paper. 
       FIG. 14  is a diagram showing another example of the narrowing result table.  FIG. 15  is a diagram showing another example of the operation screen for displaying the job narrowing result. 
     In step S 210  of  FIG. 7 , the image forming apparatus  1  stores names of print jobs associated with the job paper information, at least part of which matches with the tray paper information, in a narrowing result table T 2  as exemplified in  FIG. 14 . A result of determination as to whether or not a difference between a numerical value showing an attribute of paper included in the tray paper information and a numerical value showing an attribute of paper included in the job paper information is the threshold value for determination or smaller, as well as a difference value (a parenthesized numerical value in  FIG. 14 ) may be stored in the narrowing result table T 2 . 
     In step S 303  of  FIG. 10 , the image forming apparatus  1  displays an operation screen as exemplified in  FIG. 15 , for displaying the job narrowing result on the operation display  40  or the like. On the operation screen of  FIG. 15 , the tray paper information obtained in step S 103  and information of narrowed-down print jobs are displayed so that priority is placed on the print jobs stored in association with the job paper information that matches with the tray paper information with a higher degree of coincidence. The image forming apparatus  1  can display whether or not a difference is the threshold value for determination or smaller as well as a difference value (a parenthesized numerical value), which results in a significant improvement in operability of the user selecting a print job to be re-output in consideration of a difference. 
     In the operation screen of  FIG. 15 , a result of determination and a difference value are displayed at the same time. However, the present embodiment is not limited to this example. The image forming apparatus  1  may display only a result of determination or only a difference value. Alternatively, display of a result of determination and display of a difference value may be switchable by an optional soft key or the like. 
     As described above, the image forming apparatus  1  according to the second embodiment obtains the tray paper information detected by the sensor  53 . In this manner, the image forming apparatus  1  can obtain the tray paper information without the need of inputting the tray paper information by the user, which results in a further improvement in convenience of the user. 
     The image forming apparatus  1  according to the second embodiment narrows down print jobs in the job list based on whether or not a difference between a numerical value showing an attribute of paper to be determined included in the tray paper information and a numerical value showing an attribute of paper to be determined included in the job paper information is the predetermined threshold value for determination or smaller. In this manner, the image forming apparatus  1  can determine that attributes of paper included in the tray paper information and the job paper information match with each other even when the attributes of paper do not completely match with each other, as long as a difference is a threshold value for determination or smaller. Accordingly, the image forming apparatus  1  can execute the narrowing processing in a more flexible manner. 
     The configurations and processing according to the first embodiment and the second embodiment may be used in combination. That is, the image forming apparatus  1  may obtain both the tray paper information input by the user and the tray paper information detected by the sensor  53 , and may narrow down print jobs in the job list based on both pieces of the tray paper information. In other words, the image forming apparatus  1  may receive, on the operation screen for setting the job narrowing condition, selection of “Determination enable/disable” and/or the “Determination threshold value” input by the user with respect to each of a size of paper automatically detected, a type and a basis weight of paper input by the user, and a surface smoothness, a glossiness, and a thickness of paper detected by the sensor  53 . In this manner, the image forming apparatus  1  can narrow down print jobs in the job list based on detailed requests from the user. 
     The image forming apparatus  1  according to the second embodiment may obtain, as the tray paper information, a surface smoothness, a glossiness, a thickness, and the like of paper input by the user, instead of a surface smoothness, a glossiness, a thickness, and the like of paper detected by the sensor  53 . In this manner, the image forming apparatus  1  can obtain, as the tray paper information, a surface smoothness, a glossiness, a thickness, and the like of paper measured by the user using optional sensors. 
     Third Embodiment 
     The above embodiments describe the processing that is performed when one piece of the job paper information is associated with one print job included in the job list. A third embodiment describes processing that is performed when a plurality of pieces of the job paper information are associated with one print job included in the job list. 
       FIG. 16  is a diagram for explaining a relationship between a print job and a plurality of pieces of the job paper information. 
     As shown in  FIG. 16 , each piece of the job paper information is stored in association with each print job output in the past. Three different pieces of the job paper information are associated with Job  2 , and two different pieces of the job paper information are associated with Job  3 . When a print job is output by using a plurality of types of paper between which at least one attribute of paper is different, a plurality of pieces of the job paper information are associated with the print job. 
       FIG. 17  is a flowchart showing a procedure of processing of the image forming apparatus according to the third embodiment. The processing of steps S 101  to S 109  of  FIG. 17  is similar to the processing of steps S 101  to S 109  of  FIG. 6 , and will be omitted from description. When a plurality of pieces of the job paper information are associated with one print job, the image forming apparatus  1  may execute the job narrowing processing of step S 105  for any piece of the job paper information. 
     After the job narrowing processing of step S 105 , the image forming apparatus  1  executes processing of step S 401  before the job displaying processing of step S 106 . That is, the processor  10  of the image forming apparatus  1  functions as the narrowing unit  16  to determine whether or not there is a print job associated with a plurality of different pieces of the job paper information among print jobs narrowed down in the job list in step S 105  (step S 401 ). 
     When there is no print job associated with a plurality of different pieces of the job paper information (step S 401 : NO), the image forming apparatus  1  proceeds to the processing of step S 106 , and executes processing similar to that in the first embodiment or the second embodiment. 
     When there is a print job associated with a plurality of different pieces of the job paper information (step S 401 : YES), the image forming apparatus  1  proceeds to processing of step S 402 . The image forming apparatus  1  then obtains information of paper set on all the paper feeding trays  51  (all pieces of the tray paper information) stored in the memory  20  functioning as a tray information memory (step S 402 ). As described above, every time paper is set on the paper feeding trays  51 , the tray paper information obtained by the tray information obtainer  14  is associated with each of the paper feeding trays  51 , and is stored in the memory  20  functioning as a tray information memory. 
     Next, the image forming apparatus  1  proceeds to the job narrowing processing of step S 105  again. The image forming apparatus  1  then executes the processing of steps S 201  to S 210  for each combination of the job paper information not determined previously among a plurality of different pieces of the job paper information associated with a print job and all pieces of the tray paper information. That is, the image forming apparatus  1  determines whether or not at least part of the job paper information not determined previously matches with any piece of the tray paper information. Alternatively, the image forming apparatus  1  determines whether or not a difference between a numerical value showing an attribute of paper included in any piece of the tray paper information and a numerical value showing an attribute of paper included in the job paper information not determined previously is a predetermined threshold value for determination or smaller. When there are a plurality pieces of the tray paper information at least part of which matches with the job paper information not determined previously, the image forming apparatus  1  may determine the tray paper information having a highest degree of coincidence as the tray paper information that matches with the job paper information. After the above, the image forming apparatus  1  adds a result of the determination to the narrowing result table, and proceeds to the processing of step S 106 . 
       FIG. 18  is a diagram showing still another example of the operation screen for displaying the job narrowing result. 
     The image forming apparatus  1  displays an operation screen as exemplified in  FIG. 18 , for displaying the job narrowing result on the operation display  40  or the like. On the operation screen of  FIG. 18 , a section of “Configuration” is provided, and “Plural” indicates that a plurality of different pieces of the job paper information are associated with a print job, and “Single” indicates only one piece of the job paper information is associated with a print job. In this example, three different pieces of the job paper information are associated with Job  9 . 
     When the section of “Plural” is selected on the operation screen of  FIG. 18 , the image forming apparatus  1  displays a new window, such as one indicated as C. In the new window, for example, the image forming apparatus  1  displays a result of determination of the tray paper information that has a highest degree of coincidence with three different pieces of the job paper information, and displays the tray paper information itself. The displayed content is not limited to the above example. When there does not exist the tray paper information at least part of which matches with the job paper information, the image forming apparatus  1  may notify the user about that. The image forming apparatus  1  may then prompt the user to select the paper feeding tray  51  containing paper to be used for outputting a print job associated with the job paper information that does not match with the tray paper information. 
     As described above, when there is a print job associated with a plurality of different pieces of the job paper information among print jobs narrowed down in the job list, the image forming apparatus  1  according to the third embodiment compares all pieces of the job paper information with the tray paper information. In this manner, even when a plurality of pieces of the job paper information are associated with one print job, the image forming apparatus  1  can display information relating to all pieces of the job paper information, which results in a further improvement in convenience of the user making an attempt to re-output a print job. 
     The processing of the image forming apparatus  1  according to the above embodiments may include steps other than the steps in the above flowchart, or does not need to include some of the above steps. The order of steps is not limited to those in the embodiments described above. Each step may be executed as one step in combination with other steps, may be executed by being included in other steps, or may be executed by being divided into a plurality of steps. 
     The means and methods of performing a variety of the processing of the image forming apparatus  1  according to the embodiments described above can be performed by both a dedicated hardware circuit and a programmed computer. The above program may be provided by a computer-readable recording medium, such as a CD-ROM (compact disc read only memory), or may be provided online over a network, such as the Internet. In this case, a program recorded on a computer-readable recording medium is normally transferred to and stored in a memory, such as a hard disk. The above program may be provided as single piece of application software, or may be incorporated in software of the image forming apparatus  1  as a function of the apparatus. 
     Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.