1. Field of the Invention
The present invention relates to an image forming apparatus and in particular to an image forming apparatus that executes image forming jobs that have priority levels.
2. Description of the Related Art
Conventionally, in a system where a color image forming apparatus (color copy apparatus) and a black-and-white image forming apparatus (black and white copy apparatus) are connected to a network, when the images of a plurality of originals that contain both color originals and black-and-white originals are copied and printed out, users have been able to obtain a print result in which both color image pages and black-and-white image pages are mixed by having the images of all of the plurality of originals printed out by the color copy apparatus.
On the other hand, image formation processing by a color copy apparatus takes longer and is more costly than image formation processing by a black-and-white copy apparatus, so that there are demands for having the black-and-white originals in a plurality of originals in which both color originals and black-and-white originals are mixed printed out by a black-and-white copy apparatus. To meet such demands, when the images of a plurality of originals in which both color originals and black-and-white originals are mixed are copied and printed out, it is conceivable to have the black-and-white originals printed out by the black-and-white copy apparatus and the color originals printed out by the color copy apparatus.
In this case, in order to combine the recording sheets that have been printed by the black-and-white copy apparatus and the recording sheets that have been printed by the color copy apparatus into a single bundle like the original plurality of originals, the user has had to insert the recording sheets outputted by one of the copy apparatuses into the recording sheets outputted by the other copy apparatus by hand in order to arrange the originals in the page order.
This means that when the user wishes to collect a plurality of printed sheets together into a single document, part of the task cannot be performed by computer and the user has had to spread out the printed sheets on a desk and perform the task by hand, which has been very inefficient.
To improve this, the following conventional method has been proposed. A stacker tray (storage means) for temporarily storing color output sheets that have been outputted from a color MFP (Multi Function Peripheral) and an insert tray (refeeding means) for inserting color output sheets into black-and-white output sheets outputted from a black-and-white MFP when performing a color/black-and-white mixing are formed of a single common construction (hereinafter such common construction will be referred to as “the stacker tray”). Color output sheets that have been printed by the color MFP, whose output speed is lower than that of the black-and-white MFP, are stacked and stored in the stacker tray, and the stacker tray is attached to an insert apparatus (inserter) of the black-and-white MFP, so that the color output sheets are refed to perform color/black-and-white mixing control.
According to this color/black-and-white mixing control method, a variety of information for mixing color and black-and-white sheets, that is, information such as job numbers related to the color/black-and-white mixing job, designation of a printer for mixing, sheet size, the number of copies, stacking method, and material (a sheet type such as plain paper or thick paper) is set via a server that is connected to the network. Based on the set information, information on color originals is downloaded from the server and/or is read out from a storage means inside the image forming apparatus to form color images, and a color/black-and-white mixing operation is performed for color image sheets and black-and-white image sheets. By doing so, the occurrence of miscopied originals due to input errors by the user when making the settings has been suppressed.
However, with the above-described related art, when miscopies occur due to the erroneous insertion of one of a plurality of stacker trays or due to setting errors when a stacker tray is attached to an inserter, a large burden is placed on the user. In particular, setting errors for an inserter in the case where a plurality of black-and-white and color image forming apparatuses are connected via the network cause a large number of miscopies to be made and result in significant downtime. Also, in recent years there has been increasing demand for color/black-and-white mixing jobs of small lot sizes, so that it is desirable to stack output sheets for a plurality of jobs in a stacker tray.
According to one proposed solution of the above problem, the stacker tray is internally equipped with a memory that can be read and written and a variety of information on a plurality of jobs for performing color/black-and-white mixing is stored in advance in the memory. When the stacker tray is attached to an inserter, such information is automatically read. By performing color/black-and-white mixing control for one job or a plurality of jobs using such information, the erroneous attachment of the stacker tray and setting errors can be avoided.
FIG. 27 is a schematic diagram showing an image forming system comprised of a color MFP 2001 and a black-and-white MFP 2003, according to the proposed solution. It should be noted that in the illustrated example, output sheets related to a job that originally has a lower priority level are stacked on top of output sheets related to a job that originally has a higher priority level. A stacker 2002 is attached to the color MFP 2001 and is comprised of a stacker tray 2011 that is detachably attached and stores color output sheets, a storage device 2012 that stores a variety of information on a plurality of jobs, a lifter unit 2013 that can be raised and lowered and stacks color output sheets thereon, a discharge opening through which color output sheets are discharged from the color MFP 2001 to the stacker tray 2011, a sensor 2015 that detects a sheet surface inside the stacker tray 2011, a sensor 2016 that detects a position of the lifter unit 2013, a sensor 2017 that detects the attachment of the stacker tray 2011, gears 2018, 2019 that constitute a lifting mechanism for the lifter unit 2013, and so forth.
An inserter 2004 is attached to the black-and-white MFP 2003, and is comprised of a sensor 2021 that detects the attachment of the stacker tray 2011, sheet feeding rollers 2022 that feed black-and-white output sheets to an inside of the stacker tray, a multiple feeding prevention roller 2023 that prevents a plurality of black-and-white output sheets from being fed together, and so forth. After being detached from the stacker 2002 which is attached to the above-described color MFP 2001, the stacker tray 2011 can be attached to the inserter 2004. A large-capacity stacker 2005 is attached to the inserter 2004 and is comprised of a sensor 2031 that detects the attachment of the stacker tray 2011, a discharge opening 2032 through which output sheets are discharged from the inserter 2004, and so forth. Also, the above-described stacker tray 2011 can be detachably attached to the large-capacity stacker 2005 in the same way as with the inserter 2004.
However, there has been the following problem with the proposed solution described above. When a large number of output sheets that relate to a plurality of jobs have been stacked in the stacker tray 2011, if, as shown in FIG. 27 referred to, the stacker tray 2011 is attached to the inserter 2004 in a state where output sheets relating to a job with a lower priority level have been stacked on top of output sheets relating to a job with a higher priority level, output will be performed starting with the job with the lower priority level. This means that it is difficult to output the job with the higher priority level in a timely manner.